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As a common method for liquid drainage in wave‐shaped pipelines, foam drainage has been used in gas‐gathering pipelines in various oil and gas fields. One of the common problems encountered in wave‐shaped foam drainage pipelines is the inaccurate prediction of the liquid retention rate. This issue makes it difficult to predict liquid accumulation points, which affects gas output efficiency, causes pipeline corrosion, and generates natural gas hydrates. To clarify the liquid‐holding rate law of wavy foam drainage pipelines is studied. In this study, through experiments to verify the accuracy of the numerical simulation method, we investigate the easiest liquid accumulation points and the liquid‐holding rate of wave‐shaped foam drainage pipelines, with factors such as inlet gas velocity, inlet liquid velocity, import and export differential pressure, undulation angle, and inlet temperature change rule. Among them, the error between the numerical simulation results and the experimental results is 4.68%. Finally, after considering the influence of the aforementioned factors on the liquid retention rate of wave‐shaped pipelines, a new liquid retention rate calculation model for wave‐shaped pipelines with foam drainage is established by introducing dimensionless numbers, such as gas‐phase velocity coefficient, liquid‐phase velocity coefficient, and angle correction coefficient. The method is compared with the results of previous research, and the error is within 15%. The model has a simple form and high calculation accuracy, providing a theoretical basis for pipeline inspectors to predict liquid accumulation conditions and reasonably adjust production schedules. [ABSTRACT FROM AUTHOR]

Mussel‐inspired materials have been widely studied due to their excellent adhesion and self‐healing properties, but few studies have introduced this interesting property into the fracturing development of deep/ultra‐deep oil and gas fields. Herein, a new type of mussel‐inspired delayed crosslinking gel fracturing fluid is reported, which is formed by mussel‐inspired polymers containing many catechol groups and organic zirconium delayed crosslinkers. The strong supramolecular interaction in mussel‐inspired polymers can construct a more complex and stable dually cross‐linked polymer network based on conventional chemical crosslinking, to cope with harsh conditions such as high temperature and shear in reservoirs. After shearing at 200 °C, the reserved viscosity of mussel‐inspired delayed crosslinking gel is as high as 95 mPa·s. More importantly, the viscosity of gel remains basically unchanged at 25 °C, and the cross‐linking is completed within 300 s at 90 °C. The chemical force probe atomic force microscope (AFM) technology has successfully demonstrated that catechol groups are the main source of supramolecular interaction in mussel‐inspired polymers. The molecular simulation results show that due to the addition of catechol groups, the hydrogen bond interactions within the mussel‐inspired polymers molecules are enhanced. And the additional hydrogen bonds formed are more stable at high temperature. [ABSTRACT FROM AUTHOR]

Although the early‐Precambrian crystalline basement is now only sporadically exposed in the northern and south‐western parts of the Yangtze Block, it is supposed to have a widespread distribution beneath its Neoproterozoic and Phanerozoic covers. Here we present results of regional aeromagnetic data processing in consideration of remanent magnetization to investigate the spatial distribution of the early‐Precambrian basement buried deep under the Upper Yangtze Block and surrounding areas. The direct analytic signal amplitude of the aeromagnetic anomalies, which is less affected by the magnetization direction, reveals a broader basement below the Sichuan Basin, extending far north to the Micang Mountain. A comparison between the direct analytic signal amplitude with the reduction to the pole aeromagnetic anomalies indicates that possible remanent magnetization exists beneath the Micang Mountain near the boundary between the Qinling Orogen and Sichuan Basin. The automatic depth from extreme points transform is then performed on the direct analytic signal amplitude to estimate the depth to the early‐Precambrian crystalline basement. A synthetic model of a magnetic interface with remanent magnetization and random noise shows that the depth from extreme points method is able to resolve variable basement depths. Application of the depth from extreme points method to the direct analytic signal amplitude of the Upper Yangtze Block presents meaningful results about the early‐Precambrian crystalline basement undulations. It is shallow and uplifted beneath the Sichuan Basin, extending north to the Qinling‐Dabie Orogen, probably corresponding to the ancient Chuanzhong palaeo‐uplift. Although it gradually deepens to the east, the deepest basement is buried under the Jiangnan Orogen, which is likely associated with the collision‐induced crustal thickening between the Yangtze and Cathaysia blocks during the assembly of the Columbia supercontinent. Large gas fields around the Sichuan Basin are found at the slopes or depressions between basement uplifts, indicating that the deep marine carbonate rocks in the south and east of Sichuan Basin, particularly those located at the slopes or depressions between ancient basement uplifts, are favourable targets for further petroleum exploration. [ABSTRACT FROM AUTHOR]

Natural gas fields with economic helium (>0.3 He %) require the radioactive decay of crustal uranium (U) and thorium (Th) to generate He and tectonic/structural regimes favorable to releasing and concentrating He. An unknown is determining the role of faults and structural features in focusing deep‐seated He sources on shallow accumulations. We tested the correlation between high‐He wells (n = 94) and structural features using a new high‐resolution aeromagnetic survey in the Four Corners area, USA. A depth‐to‐basement map with basement lineaments/faults, an intrusion map, and a flattened basement structural high map were created using Werner deconvolution algorithms by combining magnetic, gravity, and topography data with magnetic and gravity depth profiles. We show quantitatively (via analysis of variance) that a non‐random process controls the relationship between He (>0.3%) and both basement faults and intrusions: 88% of high‐He wells occur <1 km of basement faults; and 85% of high‐He wells occur <1 km of intrusions. As He % increases, the distance to the structural features decreases. Strong spatial/statistical correlations of He wells to both basement faults and intrusions suggest that advective transport via faults/intrusions facilitates He migration. The role of gas phase buoyancy and structural trapping is confirmed: 88% of high‐He occurs within basement structural highs, and 91% of the remaining wells are <1 km from intrusions (potential structural high). We present a composite figure to illustrate how a probabilistic approach can be used as a predictive model to improve He exploration success by targeting zones of intersection of basement faults and intrusions within basement structural highs. Plain Language Summary: Helium, which is a colorless and odorless gas, is an important and irreplaceable commodity that is used in a variety of modern applications. Helium is often found comingled with natural gases in underground rocks. The exact importance of structural features in the accumulation of significant amounts of helium underground is largely unknown. In this study, we utilize high resolution geophysical techniques focused in the Four Corners Area, USA combined with geochemical data of helium sampled from oil/gas wells to investigate the role of structural features on helium's occurrence. We show that helium occurrences are not randomly related to structural features (basement faults and/or intrusions) using statistical tests. In fact, we show that helium percentages in natural gas increase as one moves closer to basement faults and/or intrusions. Furthermore, we suggest that these faults and intrusions likely help enable helium gas migration from deeper areas to shallower areas underground based on the strong spatial and statistical correlations of helium wells to basement faults and intrusions. We also construct a predictive composite figure using structural elements that are likely favorable to helium accumulation to aid in exploring new areas of undiscovered helium gas accumulations in the subsurface. Key Points: We show quantitatively (via analysis of variance) that a non‐random process controls the relationship between He (>0.3%) and both basement faults and intrusionsStrong correlations of He wells to both basement faults and intrusions suggest that advective transport via faults/intrusions facilitates He migrationWe present a predictive exploration model (intersection of basement faults and intrusions) that can be translated to other areas to generate He prospects [ABSTRACT FROM AUTHOR]

Gas reservoir development and the estimation of rock properties heavily rely on lithology classification, which can be difficult, time-consuming, and prone to errors. In this study, a novel deep learning-based approach has been developed for the rapid, accurate, and efficient prediction of lithology in a gas field from conventional well-log data. The well-logs, referred to as numerical well-logs (NWLs), are transformed into two-dimensional images through two proposed approaches: shallow images (SIs) and deep images (DIs). In these images, the pixels effectively represent the relationships between different logs. For this purpose, we developed residual convolutional neural networks (ResCNN) named SIs-ResCNN 2D and DIs-ResCNN 2D. The feed data for DIs-ResCNN 2D are images created and referred to as DIs, which are initially formed from a vector in which the order of logs is somehow repeated, ensuring that each pairwise combination occurs only once. This resulted in the incorporation of the connection between the logs within the pixels of the generated images, alongside the integration of unique binary combinations of the logs. We compared the proposed models, including DIs-ResCNN 2D, DIs-ResCNN 2D, and NWLs-ResCNN 1D with baseline methods such as random forest (RF), K-nearest neighbor (KNN), and support vector machine (SVM). Based on the evaluation metrics, DIs-ResCNN 2D outperformed the other proposed and baseline methods on the test dataset. A balanced DIs-ResCNN 2D model achieved 93% accuracy and F1-score of 80% on a test well, highlighting the importance of data balancing during CNN model training. [ABSTRACT FROM AUTHOR]

The normalized full gradient was developed to determine anomalous bodies, such as oil and gas fields or simple geological structures studies. We believe that even in complicated geology, normalized full gradient is practical. We introduce data preprocessing and use step‐by‐step simple‐to‐complicated synthetic tests to develop previous researchers' ideas for regional‐scale gravity modelling. One of the most important steps of the normalized full gradient is the determination of the N optimum value. We found that prevalent methods such as the standard spectral or maxima method are feasible in simple structures only. So, we have suggested the imaging criteria routine for complicated cases. We trace maximum normalized full gradient responses to detect the normalized full gradient responses at the increasing harmonic numbers as the transition of the extensive part of the anomaly to the sharp part of that. With imaging criteria for the determination of N optimum values, the complicated synthetic test results show the success of the normalized full gradient to understand complicated gravity signals. In the real case, we have studied the Northwestern Iran normalized full gradient model of the Bouguer ground gravity data beneath the seismic profile and prepared a P receiver function depth section to uncover the geometry of the Moho boundary and important interfaces in the crust. We suggest the inferred synthetic model from the Bouguer ground gravity anomaly and P receiver function depth section to normalized full gradient trustworthy test in real cases. According to the synthetic test results, we understand the frame of the normalized full gradient responses in the semi‐real case and truthful responses in the real case. Along with this, we study the second ground gravity profile of Northwestern Iran in a good resolution to uncover the deeper structures. The real case results show the possibility of Moho offset and thinning lithosphere beneath the North Tabriz Fault lithospheric boundary, the possible source of Sahand volcanic centre at the west side of the Moho offset beneath North Tabriz Fault, the deep root of the Sabalan volcanic centre in the lower crust and the lithospheric and asthenospheric wedge with the density contrast beneath Sahand–Sabalan volcanic centres. One of the most important results of our study is the lithosphere–asthenosphere boundary offset and stepped Moho possibility beneath the Talesh Mts next to the South Caspian Basin boundary. [ABSTRACT FROM AUTHOR]

The helium (He) contents of the Weiyuan and Anyue gas fields in the Sichuan Basin (China) differ significantly despite their similar helium‐nitrogen (N2) coupling characteristics, that is, the positive correlation between the N2 and He contents, and the negative correlation between the nitrogen/helium (N2/He) ratio and depth. To determine the factors influencing the differential enrichment of He resources and He–N2 coupling in the Weiyuan and Anyue gas fields, this study analysed the compositions of natural gases within the study area and established a computational model for evaluating the dissolution and exsolution amount of He and N2 in the pore water. The results indicated that: the uplift of the basement granite was crucial for the exsolution and enrichment of dissolved helium, and it was also the main reason for He–N2 coupling. The differential uplift that occurred in the Leshan–Longnvsi palaeo‐uplift during the Himalayan period further promoted the differential enrichment of He resources, thus also impacting the N2/He ratio in the study area. The distinct quantities of N2 and He exsolution during the uplift directly affected the negative correlation between the N2/He ratio and the depth. Within the same depth range of the uplift, the average and variations of the N2/He ratio in the crust‐derived helium‐rich natural gas reservoir were inversely proportional to the in situ molar partial pressure of He. The uplift of the crystalline basement is an important mechanism that causes the enrichment of helium resources and the coupling of helium‐nitrogen in the crust‐derived helium‐rich natural gas reservoir, which is of great significance for understanding the variation of N2/He ratio and exploration of He resources. [ABSTRACT FROM AUTHOR]

As the cleanest fossil fuel, natural gas plays a key role in the path towards renewables. Considering the increasing gas demand, rich CO2 and H2S gas reserves, in the past considered economically unviable, are becoming fruitful. However, the non‐conventional nature of this kind of gases, in addition to the potentially higher production cost, raises the need of new strategies for their monetization, bypassing the conventional approaches. Starting from the huge number of novel large‐scale projects for the exploitation of rich‐H2S gas fields, this paper overviews the current tendencies in sour and ultra‐sour natural gas production, focusing on the removal of sulfur‐based compounds, together with H2S and CO2. At first, available technologies for ultra‐sour gas treatment are discussed. Then, simulations of the absorption processes based on a real case‐study are carried out, in order to verify the effectiveness of the proposed alternatives for the removal of mercaptans, as well as CO2 and H2S. Results are critically analyzed, in view of providing a practical guide of industrial interest for the selection of the most suitable method. [ABSTRACT FROM AUTHOR]

To understand the research progress of molecular dynamics (MD) method in the field of clay minerals, the application of MD in the interface interaction of clay minerals is reviewed in this paper. MD simulations have become the indispensable means to study mineral interface effects. Clay minerals are common associated minerals with hydrophilic surface, the ease of argillization, negative electricity, and the ability of forming impurities and defects. They are widely concerned in the fields of mine wastewater treatment, fine clay mineral flotation, shale oil and gas exploitation, and so forth. In addition, clay minerals are considered as natural adsorbents due to their large specific surface area, but their complex interface interactions hinder their effective utilization. Therefore, it is particularly important to reveal the interaction mechanism of clay interface at the atomic/molecular level by means of software simulation technology. In this review, our focus is on the applications of MD method in the field of clay mineral interface interaction, such as clay/gas interface, clay/water interface, agents and clay/water interface, and mineral particle and clay/water interface. Furthermore, the history and shortcomings of MD simulation are summarized. The research and effective utilization of clay interface are summarized and prospected as well. [ABSTRACT FROM AUTHOR]

Numerical models reproducing the seismic evolution in gas fields can be utilized to study the characteristics of compaction‐induced seismicity during production and thus derive valuable information for the assessment of the seismic hazard. Here, we present a numerical approach for a Rotliegend gas field in Northern Germany ("reference field"), consisting of the simulation of poro‐elastic stresses within a 3D finite element model. Fault stability is controlled by Coulomb friction, whereas the post‐failure process is implemented using a slider‐block model. The model successfully computes seismic sequences, which reproduce the main characteristics of the observed seismicity in the reference field: the location, the temporal seismic evolution, including the retarded onset several years after the beginning of production, the high prevalence of moderate magnitudes, the observed maximum magnitude and cumulative seismic moment release. The numerical simulations reveal that seismicity‐driving stresses are restricted to the vicinity of fault intersections with the top and bottom of the reservoir, respectively. Slip frequently extends beyond the vertical boundaries of the reservoir, although the failure process is generally self‐arrested outside the reservoir boundaries. The magnitude frequency distribution of observed and simulated earthquakes deviates from the log‐linear behavior frequently assumed in seismic hazard assessments. Instead, the earthquake activity is consistent with a "characteristic earthquake" model, where a fault repeatedly hosts earthquakes with a specific maximum magnitude. Our analysis indicates that production‐induced seismicity is primarily controlled by poro‐elastic stress changes rather than by unknown details of subsurface conditions. This allows for a prognosis of future seismicity and associated hazard. Plain Language Summary: Seismicity induced by gas production in Northern Europe exhibits an unusual signature compared to seismicity associated with other subsurface technologies. Moderately strong earthquakes appear after several years of production, frequently without any smaller‐sized precursors. A so far unanswered question is whether the magnitude of the strongest earthquakes continues to increase during ongoing gas production or stays at a moderate magnitude level. We have developed a numerical model to simulate induced seismicity caused by gas production at a field in Northern Germany. Initially, we model the gas depletion and the associated changes in the stress conditions in the subsurface. Subsequently, we simulate earthquakes triggered by these stress changes with a block‐spring approach, where subsurface faults consist of a large number of undeformable but interconnected blocks. The strength of each earthquake at a certain time is mainly determined by the area of simultaneously activated blocks. The results of these simulations indicate that the maximum earthquake strength remains constant with ongoing gas production. The earthquake of maximum strength is subjective to each fault and may occur several times. This finding is crucial regarding the assessment of the seismic hazard for producing gas fields in Northern Europe. Key Points: A physics‐based model reproduces the most important characteristics of gas production‐induced seismicity in a field in Northern GermanyEarthquakes originate at the reservoir boundaries and may propagate into the surrounding rock, where the failure process is self‐arrestedSeismicity on each fault is characterized by a recurring maximum magnitude [ABSTRACT FROM AUTHOR]

Green synthesis and metal oxide composites have attracted much attention from researchers of industry and academia. As a typical application of green synthesis and metal oxide composites, the continuous change of industrial technology and the continuous improvement of the social and economic level, the demand for oil and gas are also increasing. However, the spatial gap between the place of origin and the place of demand for oil and gas resources is large, so the long-distance oil and gas pipeline came into being. However, under the action of time, coupled with the corrosion effect of the soil due to deep burial, some pipelines have serious aging and corrosion phenomena. Therefore, in order to give corresponding guarantees for economic development, we need to conduct in-depth research and analysis of the corrosion of oil and gas long-distance pipelines and give effective solutions. In this paper, the corrosion rate prediction of buried oil and gas pipelines is studied in Changqing gas field. By improving the inertial weights and learning factors of the traditional particle swarm algorithm, the parameters of the generalized regression neural network are optimized and selected, and the corrosion rate prediction model of buried pipelines is finally constructed. Comparative analysis with other swarm intelligence algorithms shows that the improved particle swarm algorithm has stronger convergence ability and higher prediction accuracy than the BP model and SVM model. In addition, based on the detection data collected at the site of the gathering and transportation pipeline in Changqing gas field, this paper uses the extreme value distribution theory and the local corrosion progress formula to establish a prediction model for the residual life of corrosion of buried pipelines. The model established in this paper can effectively determine the risk pipe segment of buried pipeline and provide a decision-making basis for pipeline management departments. The work provides an important application guidance to green synthesis and metal oxide composites. [ABSTRACT FROM AUTHOR]

At present, extended reach wells (ERWs) are widely applied on oil and gas exploitation in numerous reservoirs around the globe, and this is attributed to their superiority in the development of marginal oil and gas fields and cost-effectiveness. Identifying the effects of reservoir properties on production is significant to the operation of ERWs for oil and gas extraction. This work utilizes numerical modeling techniques to simulate the application of ERWs in low-permeability formations. The impacts of low permeability on the oil production and the pressure distribution of the reservoirs with different formation properties are analyzed, and the simulation results of the oil exploitation by ERWs are compared with the oil production and pressure distribution of that by horizontal wells (HWs). A test scheme is designed to analyze the effect of reservoir properties on oil extraction through ERWs and quantify the sensitivity of oil production to reservoir properties. The reservoir properties of formation rock compressibility, formation fluid compressibility, initial reservoir pressure, reservoir saturation pressure, formation porosity, and absolute permeability are studied through 66 ERW cases. The results illustrate that low permeability leads to a fast decrease of oil production rates and significantly uneven pressure distribution. The pressure is lower at the center of the ERW but is higher at both ends of the ERW, while the pressure is evenly distributed along the horizontal well in the HW cases. In addition, the oil production is in direct proportion with the initial reservoir pressure, formation rock compressibility, formation porosity, and formation fluid compressibility but is in an inverse ratio with the reservoir saturation pressure. Furthermore, the initial reservoir pressure has the largest impact on both the total cumulative oil production driven out by natural energy and the cumulative oil production after the development of ten years by natural energy; on the contrary, the absolute permeability has no effect on the total cumulative oil production driven out by natural energy. [ABSTRACT FROM AUTHOR]

The naturally fractured reservoirs are one of the most challenging due to the tectonic movements that are caused to increase the permeability and conductivity of the fractures. The instability of the permeability and conductivity effects on the fluid flow path causes problems during the transfer of the fluids from the matrix to the fractures and fluid losses during production. In addition, these complications made it difficult for engineers to estimate fluid flow during production. The fracture properties' study is important to model the fluid flow paths such as the fracture porosity, permeability, and the shape factor, which are considered essential in the stability of fluid flow. To examine this, this research introduced new models including decision tree (DT), random forest (RF), K-nearest regression (KNR), ridge regression (RR), and LASSO regression model,. The research studied the fracture properties in naturally fractured reservoirs like the fracture porosity (FP) and the shape factor (SF). The datasets used in this study were collected from previous studies "i.e., Texas oil and gas fields" to build an intelligence-based predictive model for fluid flow characteristics. The prediction process was conducted based on interporosity flow coefficient, storativity ratio, wellbore radius, matrix permeability, and fracture permeability as input data. This study revealed a positive finding for the adopted machine learning (ML) models and was superior in using statistical accuracy metrics. Overall, the research emphasized the implementation of computer-aided models for naturally fractured reservoir analysis, giving more details on the extensive execution techniques, such as injection or the creation of artificial cracks, to minimize hydrocarbon losses or leakage. [ABSTRACT FROM AUTHOR]

The accurate estimation of in situ stress tensor has an inevitable role in solving problems facing the development of oil and gas fields. Two components of three, vertical stress (σv${\sigma }_v$) and minimum horizontal stress (σh${\sigma }_h$), could be computed through direct methods. The last and most challenging component, maximum horizontal stress (σH${\sigma }_H$), is commonly computed based on the elastic theory assumptions and shape of the borehole breakouts from well‐logging data. Due to the abundance of borehole breakouts data, methods based on the shape of breakouts are highly valued. Field observations show that such breakouts commonly occur in the weak layers, which contradict elastic assumptions. Furthermore, finding the consistent relationship between the shape of the breakouts and loading conditions remains the main issue for such approaches. The process's initiation and development until stabilization have been simulated by borehole breakout modeling considering inelastic deformation. Machine learning algorithms have been implemented to ascertain the relationship between applied in situ stress and obtained borehole breakouts. In this paper, first using the finite element method and elastoplastic model, a set of in situ stress and their corresponding shape of borehole breakouts is obtained. Then, the data set is used to train four machine learning algorithms (XGBoost, LightGBM, CatBoost, and AdaBoost) to find the relationship between the in situ stress and the shape of breakouts. Finally, employing the inversed analysis to the trained algorithms, the in situ stress is estimated from the shape of breakouts. Even though, the numerical experiments show that all four algorithms are promising for predicting the in situ stress, the XGBoost algorithm indicates more accuracy than the others. [ABSTRACT FROM AUTHOR]

High‐velocity friction experiments on simulated fault gouges sheared at high normal stress and to low displacement are particularly relevant to induced seismicity, which is becoming an important topic in fault mechanics. Using a new, improved set‐up, which allows simulation of fault stress and fluid pressure (P $P$) conditions approaching in‐situ reservoir values, we performed ring‐shear experiments on simulated fault gouges prepared from the source‐, reservoir‐, and caprock‐formations of the Groningen gas field. Pre‐sheared gouges were subjected to a rotational slip pulse reaching ∼1.0 m/s peak velocity and 13–16 cm total displacement at effective normal stresses (σne ${\sigma }_{n}^{e}$) of 5–31 MPa and P $P$ up to 5 MPa, using water or dry nitrogen as pore fluid. All water‐saturated gouges show strong dynamic weakening within a few cm of slip, with the lowest dynamic friction (0.2–0.4) measured at the highest σne ${\sigma }_{n}^{e}$. By contrast, the weakening was subtle in experiments using nitrogen. Our analyses focus on the high‐P $P$ experiments, which are more realistic and show a distinct dependence of constitutive parameters (e.g., slip‐weakening rate) on σne ${\sigma }_{n}^{e}$, in the form of empirical linear, power‐law or exponential relations. The results provide much‐needed constraints for numerical modeling of induced rupture propagation in the Groningen field. Based on temperature‐ and P $P$‐measurements made in near‐direct contact with the active shear band, and using "post‐mortem" microstructures, we exclude previously‐proposed dynamic weakening mechanisms (e.g., flash heating or thermal pressurization) and suggest that water pressurization at heated asperity or grain contacts explains the weakening seen in our high‐P $P$ experiments. Plain Language Summary: In the Groningen gas field of the Netherlands, induced seismic events have occurred since the 1990s. The strongest event occurred in 2012 with a magnitude of MW 3.6. How faults slip during such small magnitude earthquakes (i.e., magnitude 3–4) is not clear, despite several recent studies. We conduct laboratory experiments to simulate the pulse‐like (i.e., short but rapid) fault slip behavior characteristic for small magnitude human‐induced seismicity, using a newly designed experimental set‐up enabling monitoring of the slip behavior under stress and displacement closer to conditions relevant to faults in Groningen. We find that the different rock types present in the Groningen field offer various levels of resistance to rupture of small earthquakes, which is crucial information for modeling earthquakes and understanding seismic hazard and risk. In addition, based on observations of fluid pressure, temperature and dilatation during the experiments, we propose a fault weakening mechanism occurring on the micrometer scale, that can explain our observations. Key Points: Wet faults in Groningen gas field lithologies weaken significantly in a short seismic slip pulse while dry ones do notWe observed fluid depressurization and dilation during seismic slip pulse, which is opposite to what is expected from thermal pressurizationSmall earthquake rupture experiences different resistance and slip weakening behaviors within different lithologies in the Groningen field [ABSTRACT FROM AUTHOR]

Hydrocarbon production from oil and gas fields is controlled by a variety of interconnected factors with a hierarchy of significance that is, for the most part, difficult to untangle. This article documents and investigates the spatial and temporal distribution of key hydrocarbon field parameters on the UK Continental Shelf. Data have been compiled from publicly available sources for 424 fields. Variables are considered as "descriptive parameters," "control parameters" and "outcomes". Descriptive parameters are metadata such as field name, location, etc. Control Parameters include depositional environment, present depth of burial, porosity, permeability, reservoir formation pressure, reservoir temperature, average net‐to‐gross, number of fault populations, hydrocarbon API, field area, bulk rock volume, well density, number of wells (production and injection), well spacing, gas oil ratio, reservoir thickness, fluid saturation, compartmentalization (quantitated by number of observable non‐communicating fault compartments), structural complexity (scaled from 0 to 5), field production strategy, trap type and stratigraphic heterogeneity. Outcomes are used to assess field performance and include final recovery factor (estimated), maximum production rate, and cumulative monthly production. Analysis of the database illustrates a number of empirical observations regarding hydrocarbon production on the UKCS. The Jurassic plays have been the most successful in the region in terms of total volumes produced while the Permian reservoirs of the SNS account for the majority of the gas. Most of the UKCS reservoirs record top depths between 2000 and 4500 m with good reservoir quality. The best reservoir quality is observed in reservoirs that were deposited within deep marine systems. The largest hydrocarbon reserves are found in the Northern North Sea basin in these deep marine (as well as paralic and shallow marine) reservoirs. Using the data from this article and affiliated data, potential exists for extracting insight beyond spatio‐temporal distributions. [ABSTRACT FROM AUTHOR]

The Jurassic petroleum system in the piedmont zone between Qaidam Basin and Altun Mountain is rich in oil and gas resources. Based on the sedimentary environment, geochemical analysis, and distribution prediction of the Middle–Lower Jurassic source rocks in the piedmont zone between the south‐western Qaidam Basin and Altun tage region, the Jurassic oil and gas exploration potential in the area was systematically evaluated. The Jurassic source rocks in the study area are mainly coal, dark mudstone, and carbonaceous mudstone developed in the Lower Jurassic fan delta facies, as well as, oil shale, and mudstone in the Middle Jurassic of lacustrine facies, and coal measure strata of braided river delta facies. The thickness of Middle Jurassic source rocks is relatively thicker. Through restoration and weathered source rock samples analysis, the average TOC of the Middle Jurassic source rocks in the area can reach 4.19%, and the average chloroform bitumen "A" is 0.5915%, meeting the criteria for a good source stone. Every index is close to the Yuka Jurassic source rock, the highest quality found in the basin so far. At the same time, the distribution range of Jurassic source rocks in the study area is meticulously described through seismic facies identification and prediction analysis. Several Jurassic hydrocarbon generating centers in the area, such as Honggouzi ‐ Yueyashan, Nanyishan ‐ Xiaoliangshan, Pingxi, and Dafengshan, with thicknesses ranging from 200 to 400 m, indicating that the Jurassic source rocks have the material basis for large oil and gas fields formation. [ABSTRACT FROM AUTHOR]

As fishbone multilateral wells are increasingly used in the development of oil and gas fields, the need for the optimal design of multilateral well parameters has become increasingly urgent. Although the establishment of multilateral well productivity models has taken a step forward due to recently contributed research results, there are still few studies on model verification; that is, these models lack verification, and their reliability is uncertain, which increases the difficulty of their promotion and application in practice. Therefore, based on a more comprehensive horizontal well productivity prediction model, a fishbone multilateral well productivity prediction model was established in this work. Taking an oil field in the Middle East as an example, multilateral well productivity prediction and parameters sensitivity analysis were carried out, and the results were compared with the simulation results determined by using CMG digital simulation software. The established model was verified in terms of branch length, branch angle, and branch output contribution. The conclusions reached by these two methods were consistent, which verified that the established model was reliable. [ABSTRACT FROM AUTHOR]

Hydraulic fracturing, as an oil-water well stimulation and injection technology, is particularly important in the production and stimulation of low-permeability oil and gas fields, and the performance of the fracturing fluid directly affects the success of the fracturing operation. Compared with traditional water-based fracturing fluids, clean fracturing fluids have the advantages of strong sand-carrying ability and easy gel breaking with no residue. Aiming at the problem of poor temperature resistance and shear resistance of the clean fracturing fluid, based on previous research, this paper selects a high-temperature-resistant clean fracturing fluid system and evaluates the performance of the system. The research results show that the system has better rheological properties, better sand-carrying performance, shorter gel-breaking time, and less damage to the reservoir. [ABSTRACT FROM AUTHOR]

Sulige gas field is the largest natural gas producing area in China. Due to the "water blocking" effect, the gas–water layer significantly influences the development of gas reservoirs. The existence of low‐resistivity gas layers in the He 8 member of the Shihezi Formation in the southwestern Sulige gas field makes it challenging to distinguish the gas layers from the gas–water layers using conventional identification methods. To effectively identify the low‐resistivity gas layers, their genetic mechanisms are analyzed by studying their lithology and pore structural characteristics based on the well logging and core experimental data. The low‐resistivity gas layers are main affected by three causes: (1) electrical conductivity of argillaceous laminae in sandstone, (2) additional conductivity of clay minerals, and (3) high bound water saturation caused by the development of micropores and clay minerals in sandstone. Herein, to effectively distinguish the low‐resistivity gas layer from the gas–water layer based on the genetic mechanism of the low‐resistivity gas layer, first, a gas‐bearing index was constructed to characterize the gas‐bearing properties of the reservoir using the neutron logging and density logging curves after eliminating the influence of the dispersed shale. Second, a model to calculate the bound water saturation was constructed by selecting sensitive parameters with respect to the causes of bound water. Then, two plots, namely the gas‐bearing index–natural gamma relative value cross‐plot and the bound water content–porosity cross‐plots, were constructed using the gas testing data, and the identification standard of the low‐resistivity gas and gas–water layers was established. The interactive identification of the two cross‐plots effectively distinguished the low‐resistivity gas layer from the gas‐water layer, thereby providing a basis for understanding the distribution of gas and water in the southwestern Sulige gas field, which may guide further exploration and the deployment of the development well pattern. [ABSTRACT FROM AUTHOR]

The growing energy demand, together with the depletion of sweet gas reservoirs, impose the monetization of ultra‐sour natural gas fields with a high H2S content. To date, in large scale facilities, H2S is removed from natural gas through amine washing and it is converted to sulphur in the Claus process. The Claus process is the leading H2S conversion technology for large scale applications. Regarding small scale plants, scavengers are the most efficient and widely spread choice. On the other hand, present middle scale options show quite high operating costs. Therefore, research efforts are devoted to developing new intermediate scale alternatives with lower costs and easier operability. When developing a new process, the study of the state‐of‐the‐art is the first essential step. No systematic review of H2S valorisation technologies is available in literature. To fill this gap, the aim of this work is to summarize the available processes considering both commercial and novel tendencies for H2S conversion. For each technology, details about process operating conditions are discussed and the typical application is provided, when possible, together with the corresponding pros and cons. [ABSTRACT FROM AUTHOR]

Enhanced gas recovery (EGR) is a recognised CO2 utilisation technique that can reduce the cost of carbon storage and improve its economic feasibility. Although there are many studies on the potential of depleted gas fields for CO2 storage, there has not been a comprehensive full‐scale study that can analyse different aspects of carbon utilisation together with the potential of storage, from reservoir characterisation to modelling and economic evaluation. The aim of this study is to develop a benchmark for assessing the technical and economic feasibility of carbon utilisation and storage in abandoned and nearly depleted gas fields. A depleted gas field from the Bredasdorp Basin in South Africa was selected for CO2‐EGR and storage, given the availability of data and infrastructure. The reservoir of interest is divided into compartments, with this study focusing exclusively on compartment C1. The gas in place (Gi) in compartment C1 was 5.8E+08 MSCF, which was reduced to 3.33E+08 MSCF at the end of the primary production phase. The results obtained indicated that the gas reservoir is very heterogeneous, and a recovery of 20% can be achieved if the injection and production rates are 500 and 3000 MSCF/day, respectively. The amount of CO2 injected after 71 years was about 7.78E+07 MSCF. It was shown that the CO2 in this field can be injected for 71 years without causing problems with the integrity of the reservoir. The economic model was built assuming a project duration of 10 years. The model shows that the total cost of carbon capture, transport and storage is higher than the total revenue for 8 years of natural gas utilisation, which means that the amount of gas recovered from compartment C1 of the reservoir could not offset the cost of CCUS. It is recommended that additional data be collected for the C2 compartment, the carbon capture processes at the Mossel Bay GTL plant, and pipeline transportation to reduce the uncertainty of the proposed economic model. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Helium, a rare gas widely applied in high-tech fields, is a significant strategic resource in China. The foreign-trade dependence ratio of helium in China is 95%. The work reviewed the applications and market analysis of helium and reservoir modeling and distribution of helium in Changqing Gas Field as well as the helium extraction techniques from natural gases. According to the analysis of the component test and the dynamic monitoring of exploited gas wells and gas-gathering stations, the average helium content in Changqing Gas Field was 0.028%. Helium was rich in the northwest of Changqing Gas Field, but poor in the central and eastern regions. The helium volume contents in Qingyang Gas Field, Huanglong Gas Field, and the central, western, and southern regions of Sulige Gas Field have reached the industrial development standard. PetroChina performed the economic-feasibility evaluation and production-factor matching research on helium development and selected Changqing Gas Field as the demonstration for development. A large helium plant was established in Changqing Gas Field using the cryogenic method with/without membrane separation for helium extraction. Then, a helium development scheme was formulated and implemented to build the industry chain of helium in China. Changqing Gas Field is rich in helium resources. Developing helium has entered a strategic period with the technological advancement in extracting helium from natural gases and the increased prosperity of the international helium market. There are broad prospects and great benefits to exploiting helium resources in Changqing. [ABSTRACT FROM AUTHOR]

Several large gas fields have been found in the Central Sichuan Basin in recent years, with proven reserves of more than 100 × 10 9 m3. Among these, the tight sandstone gas in the Late Triassic Xujiahe Formation is a key target in the Sichuan Basin. The key to the discovery of high‐yield areas rich in tight sandstone gas is to determine the pore structures and the lower limits of effective physical properties of reservoirs that control natural gas accumulation. In this study, we investigate the Late Triassic second Member of the Xujiahe Formation (hereinafter referred to as the Xu2 Member) in the Central Sichuan Basin as an example. We analyse the distribution characteristics of pores and throats in the reservoirs and identify that the reservoir in the study area is mainly characterized by small pores and narrow throats. The physical properties of reservoirs in the area are mainly controlled by pore‐throat radius and the permeability–porosity ratio. Nuclear magnetic resonance analysis indicates that the irreducible water saturation is mostly more than 50% and is inversely correlated with the physical properties of reservoirs in the study area. Meanwhile, with an increase in the physical properties of reservoirs, the proportion of large pores increases and the irreducible water saturation rapidly decreases. According to the gas–water two‐phase seepage experiment, for reservoirs with good physical properties, the gas relative permeability significantly increases with an increase in gas saturation and the reservoir permeability has more significant effects. Where the reservoir permeability is less than 0.4 mD, the permeability of both gas phase and water phases is only less than 0.1, and the mobility of both gas and water is poor. Only when the reservoir permeability is more than 0.4 mD, can the gas relative permeability reach more than 0.3, and the water mobility is significantly inhibited. In this case, favourable results can be achieved from the natural gas development. As verified by the development of the tight sandstone reservoirs in the Xu2 Member in Central Sichuan Basin, the lower limits of physical properties allowing for effective natural gas development include the reservoir permeability of more than 0.1 mD (preferably more than 0.2 mD) and the reservoir porosity of greater than 6%–7%. [ABSTRACT FROM AUTHOR]

Steam‐assisted gravity drainage reservoirs require an immense amount of energy and water resources, and proper monitoring of steam evolution and depletion patterns is integral to the economic and environmental efficiency of the operation. Muon tomography is a passive sensing technique, which has proven to successfully model density anomalies in a variety of applications but has not yet been applied to the oil and gas field. A previous study simulated muon intensity data to model density changes in a realistic steam‐assisted gravity drainage reservoir at 1.25 and 5 years after initial production. The results showed that muon tomography is a promising technique for monitoring steam‐assisted gravity drainage reservoirs with high spatial resolution and over short time intervals of weeks to months. Here we demonstrate the advantage of using vertical gravity gradient data and muon tomography data in a joint inversion to improve the muon‐only inverse models. Forward models for simulated muon and gravity gradient data are jointly inverted for a realistic steam‐assisted gravity drainage reservoir at 230 and 130 m total vertical depth at 1.25 years after initial production. Results show that the addition of gravity gradient data helps to constrain the density change models mainly in depth and to a smaller extent laterally. For a sparse muon sensor array of 48 sensors over a 1000m$1000\, \text{m}$×$\ensuremath{\times}$600m$600\, \text{m}$ reservoir at 100m$100\, \text{m}$ depth, the joint inversion using gravity gradient data reduces the difference between the inverse and true model by 12% compared to a muon‐only inversion. The improvement is smaller at 200m$200\, \text{m}$ depth with 6%. The improvement in resolvability metrics is summarized, and limitations are discussed. The addition of multiple data types in a joint inversion improves the resulting models leading to an overall decrease in model uncertainty which can be used for improved operational efficiency in steam‐assisted gravity drainage operations. [ABSTRACT FROM AUTHOR]

To solve the difficult problems in the field of unconventional oil and gas extraction and hard rock excavation in urban underground spaces, this paper proposes a rock-breaking technique with high-temperature and high-pressure water under thermally driven conditions and establishes a coupled thermal-fluid-solid model with COMSOL Multiphysics (COMSOL Co., Ltd. Shanghai, China). Different simulation groups are established by controlling variables to explore the effects of the surrounding rock load, heat source power, and Biot coefficient on the damage evolution during thermally driven rock breaking. To make the results relevant to practical engineering, the damage evolution results under the maximum normal stress criterion, maximum normal strain criterion, and Coulomb-Navier damage criterion are considered, and a comparative analysis is performed. The results of this study show that an increase in unilateral load and heat source power accelerates the damage evolution rate, while an increase in bilateral load and Biot coefficient has the opposite effect. The damage evolution rate controlled by the maximum normal stress criterion is the fastest under general conditions. Finally, the advantages in rock breaking provided by the established method are verified by a comparison of results from the proposed model and a conventional hydraulic fracturing model. [ABSTRACT FROM AUTHOR]

Energy development is one of the most rapidly increasing land uses in North America, so understanding how wildlife respond to different types of energy infrastructure is crucial for informing land‐use policies. Effects of energy development on wildlife habitat use and selection can vary depending on infrastructure type, level of industrial activity, and density. I examined seasonal habitat use and selection of greater sage‐grouse in relation to energy development in a high‐elevation oil and gas field in western Colorado by linking spatially and temporally explicit energy infrastructure layers with telemetry locations of marked females from 2006 to 2014. Objectives were to (1) quantify energy infrastructure around seasonal use locations; (2) examine how seasonal resource selection is affected by energy infrastructure with disturbed versus reclaimed surface and different levels of industrial activity; and (3) assess current surface disturbance and infrastructure density caps. Between 92% and 97% of seasonal use locations had <3% disturbed surface within 1000 m. After accounting for landcover and topography, breeding and wintering females selected locations with less disturbed, reclaimed, and total anthropogenic surface. Breeding females selected locations farther from high‐activity well pads and facilities. In contrast, females selected locations with low to intermediate values of disturbed and reclaimed surface and locations closer to pipelines and roads in summer–fall. This is the first evidence that greater sage‐grouse select locations with energy infrastructure in any season and suggests that responses to energy development may differ between mesic and arid sagebrush ecosystems. Females avoided locations with >1.1%–2.5% disturbed surface during breeding and winter and selected locations with lower densities of active energy features during breeding and roads in winter. Density caps of one active energy feature and 1.5 mi (2.41 km) of road per section were adequate to prevent avoidance except during the breeding season. Disturbance caps should be set at 1.1% disturbed surface and 1.8% total anthropogenic surface in breeding habitat and 2.5% disturbed surface and 3.5% total anthropogenic surface in winter habitat to minimize negative impacts on female habitat selection in this population. Results also support timing restrictions on construction and drilling during breeding and rapid transitioning of well pads from drilling to production. [ABSTRACT FROM AUTHOR]

In recent years, a series of highly saturated leakage‐type gas hydrates have been discovered in the western Qiongdongnan Basin (QDNB), South China Sea. Based on the molecular compositional and isotopic characteristics of the gas samples relevant to the gas hydrates collected from the two leakage‐type gas hydrate accumulations in the GMGS5 and GMGS6 drilling zones, a detailed geochemical gas‐to‐gas correlation was conducted in this study, in order to further understand the geochemical characteristics and possible hydrocarbon sources of these gas hydrates. The natural gas relevant to the gas hydrates in the GMGS5 block is characterized by wet gas (67.96% < %C1 < 98.58%, C1/C1+ < 0.9) and significant molecular and carbon isotope fractionation within the depth profile, whereas the gas samples from the GMGS6 block exhibit the characteristics of dry gas (99.25% < %C1 < 99.81%, C1/C1+ > 0.9) and lack molecular and carbon isotope fractionation. Approximately 40%–60% of the methane within the gas hydrate is of microbial origin, while the C2+ gas components are typical coal‐type gas that are derived from thermogenic source rocks or deeply‐buried natural gas fields. In addition, typical in situ primary microbial methane (–80.6‰ < δ13C‐C1 < −67.7‰) was discovered in well Wb, which was applied to estimate the contribution of the microbial gas to the gas hydrates. The gas‐to‐gas correlation results show that the hydrate gases within the two leakage‐type gas hydrate accumulations in the GMGS5 and GMGS6 blocks are geochemically different, suggesting that they may have been derived from different source kitchens. Our results further indicate that the deeply‐buried thermogenic gas significantly contributed to the shallowly‐buried gas hydrates in the western QDNB and multiple effective thermogenic source kitchens provided the hydrocarbon gas in the gas hydrate accumulations. [ABSTRACT FROM AUTHOR]

Various lines of evidence, including the occurrence of bitumen and fluid inclusions, show that oil charge once took place in the Kela-2 gas field, Kuqa foreland basin, Northwest China. However, the scale of the ancient oil reservoir remains unclear, as does the process by which the reservoir evolved into the present dry gas field. Here, using data from analyses of fluid inclusions, petrography, laser Raman spectroscopy, and quantitative fluorescence, the hydrocarbon accumulation history of the Kela-2 gas field is reconstructed. The results show that the gas field underwent three periods of hydrocarbon charging and one period of adjustment. The first oil charging occurred at about 12 Ma, as recorded by the first group of oil inclusions containing 0–8 vol.% gas with yellowish-brown fluorescence. The second charging involved mature oil charging at about 4 Ma, recorded by the second group of oil inclusions containing 15–25 vol.% gas with blue-white fluorescence. According to quantitative grain fluorescence (QGF) and rock pyrolysis analysis, an ancient oil reservoir existed with an oil-column height of about 350 m, and the paleo oil–water contact was lower than the present gas–water contact. Under intense thrusting from 3 Ma, the ancient oil reservoir was destroyed, with oil escaping through the Kashangtuokai thrust fault, which broke the salt layer, as this layer at that time lay in the brittle deformation domain. The inferred destruction of the ancient oil reservoir is supported by the numerous oil and gas shows at the surface and in shallow layers near the Kashangtuokai fault, as well as the anomalous development of authigenic kaolinite in the gas reservoir, which was enhanced by an open or semiopen system caused by the fault breaking through the salt layer. Subsequently, with increasing burial depth to more than 3000 m, the fault that had cut through the salt layer annealed because the salt layer then lay within the ductile deformation domain. The higher overpressure that occurred during the third gas charging at about 2 Ma reflected the annealing of the fault in the salt layer, favoring late gas accumulation and preservation. The evolution of the Kela-2 gas field provides an important case study for understanding the role of the salt layer crossing the brittle–plastic transition and the dynamic evolution of the salt caprock in salt-containing foreland basins. [ABSTRACT FROM AUTHOR]

From 2017 to 2019, three destructive earthquakes (27 January 2017 Mw 4.7, 16 December 2018 Mw 5.2, and 3 January 2019 Mw 4.8) occurred in the Changning shale gas field in the southwest Sichuan Basin, China. Previous seismological studies attributed these events to hydraulic fracturing (HF), but were unable to identify the causative seismogenic faults and their slip behaviors. Here, we use Sentinel‐1 synthetic aperture radar data to measure surface deformation triggered by the three events and conduct geodetic inversions to characterize their rupture models. The resulting coseismic interferograms show prominent surface deformation with the maximum line‐of‐sight displacements of up to 4 cm. The inversion results show that all three earthquakes mainly ruptured sedimentary formations above the shale gas bed, in the upper 3 km of the crust, with slip magnitudes ranging from 8.5 to 15 cm, and stress drops ranging from ∼1.8 to ∼3.3 MPa. Their source faults intersect with horizontal HF wells, but do not root in the crystalline basement. Combined with the reported difficulty of increasing HF operation pressures prior to the three events, we argue that they were most likely induced by direct injection of pressurized fluids into the fault zones. Crustal deformation patterns inferred from regional topography and GPS velocities highlight that the Changning field is located within a triple junction region near the southeastern margin of the Tibetan Plateau with large deformation gradients; such conditions are not only favorable to the development of critically stressed faults, but also facilitate the occurrence of at least moderate magnitude earthquakes. Plain Language Summary: The number of earthquakes induced by the process of shale gas extraction through hydraulic fracturing (HF) has been increasing across the globe, with dozens of M > 4 events reported by the end of August 2021. Although most case studies on HF‐induced seismicity are from the United States and Canada, the southwestern Sichuan Basin (China), located to the southeast of the Tibetan Plateau, is another region with notable seismicity linked to HF operations, including dozens of moderate‐to‐large earthquakes. We here focus on the three largest Mw ≥ 4.7 earthquakes that occurred within the Changning shale gas field up to now. We use geodetic techniques to measure ground deformation caused by the three earthquakes and to further infer their ruptures at depth. Our results reveal that the three earthquakes occurred on shallow faults intersecting with horizontal HF wells, with little‐to‐no slip in the crystalline basement below the depth of 3 km. These questions the common theme of HF‐induced earthquakes having hypocenters proximal to basement rock, presumably associated with basement‐rooted faults, and suggests that the potential for ground shaking of HF‐induced earthquakes is more significant than previously understood. Key Points: The three events ruptured shallow faults within sedimentary formations above the shale gas bed rather than basement‐rooted faultsThe faults of the three events intersect with horizontal hydraulic fracturing wells and were likely reactivated by direct fault‐zone pressurizationHigh HF‐induced seismicity rate in the Changning area links to the proximity to a triple junction region with relatively high tectonic strain accumulation rates [ABSTRACT FROM AUTHOR]

With the high-speed development of artificial intelligence, machine learning methods have become key technologies for intelligent exploration, development, and production in oil and gas fields. This article presents a workflow analysing the main controlling factors of oil saturation variation utilizing machine learning algorithms based on static and dynamic data from actual reservoirs. The dataset in this study generated from 468 wells includes thickness, permeability, porosity, net-to-gross (NTG) ratio, oil production variation (OPV), water production variation (WPV), water cut variation (WCV), neighbouring liquid production variation (NLPV), neighbouring water injection variation (NWIV), and oil saturation variation (OSV). A data processing workflow has been implemented to replace outliers and to increase model accuracy. A total of 10 machine learning algorithms are tested and compared in the dataset. Random forest (RF) and gradient boosting (GBT) are optimal and selected to conduct quantitative analysis of the main controlling factors. Analysis results show that NWIV is the variable with the highest degree of impact on OSV; impact factor is 0.276. Optimization measures are proposed for the development of this kind of sandstone reservoir based on main controlling factor analysis. This study proposes a reference case for oil saturation quantitative analysis based on machine learning methods that will help reservoir engineers make better decision. [ABSTRACT FROM AUTHOR]

Reservoir compaction, surface subsidence, and induced seismicity are often associated with prolonged hydrocarbon production. Recent experiments conducted on the Groningen gas field's Slochteren sandstone reservoir rock, at in‐situ conditions, have shown that compaction involves both poroelastic strain and time independent, permanent strain, caused by consolidation and shear of clay films coating the sandstone grains, with grain failure occurring at higher stresses. To model compaction of the reservoir in space and time, numerical approaches, such as the Discrete Element Method (DEM), populated with realistic grain‐scale mechanisms are needed. We developed a new particle‐interaction law (contact model) for classic DEM to explicitly account for the experimentally observed mechanisms of nonlinear elasticity, intergranular clay film deformation, and grain breakage. It was calibrated against both hydrostatic and conventional triaxial compression experiments and validated against an independent set of pore pressure depletion experiments conducted under uniaxial strain conditions, using a range of sample porosities, grain size distributions, and clay contents. The model obtained was used to predict compaction of the Groningen reservoir. These results were compared with field measurements of in‐situ compaction and matched favorably, within field measurement uncertainties. The new model allows systematic investigation of the effects of mineralogy, microstructure, boundary conditions, and loading path on compaction behavior of the reservoir. It also offers a means of generating a data bank suitable for developing generalized constitutive models and for predicting reservoir response to different scenarios of gas extraction, or of fluid injection for stabilization or storage purposes. Plain Language Summary: In an oil or gas reservoir, located at a few km's depth in the subsurface, pressurized fluid is present in small spaces (pores) between the grains making up the rock. When extracting the fluid, the pressure of the fluid decreases and the reservoir rock will start to feel more of the effective weight of the overlying rock layers. This may lead to elastic (reversible) and inelastic (permanent) compaction of the reservoir by interactions happening at the scale of the individual grains. This reservoir compaction can be observed at the surface through phenomena such as surface subsidence and induced seismicity. Therefore, accurately predicting reservoir compaction, using a numerical model, is crucial to assess these phenomena, and develop safe production strategies. We have developed a grain‐scale, numerical model for the reservoir sandstone rock of the seismogenic Groningen gas field (the Netherlands), based on recent experimental observations. Our model includes realistic grain‐scale interactions, and allows for variations in porosity and mineralogy, as seen in the real rock. With such 'digital samples', in the future it will be possible to extrapolate the limited laboratory experimental data, obtained at specific locations in the reservoir, to the whole field. Key Points: New grain‐contact model for discrete element method is proposed based on microphysical mechanisms observed in Groningen reservoir sandstoneThe new contact model combined with discrete element modeling predicts nonlinear elastic and inelastic deformation of sandstoneIt allows systematic investigation of the effects of mineralogy, microstructure, boundary conditions, and loading paths on reservoir behavior [ABSTRACT FROM AUTHOR]

Hydrate formation risk is an important challenge in the development of deep-water gas field. Considering the characteristics of the Lingshui (LS) gas field in the South China Sea and the difference of well structures, a model for calculating wellbore temperature and pressure in deep-water gas production well is proposed and verified by the field data. Combining the hydrate equilibrium models with varied gas components, the prediction method of hydrate formation region in deep-water gas well in the South China Sea is obtained. The hydrate formation regions under different operating conditions for a deep-water gas well in the South China Sea were given by the proposed model. The results show that no hydrate formation risk exists in the production operation, but the risk exists in the shut-in and testing operations. Meanwhile, the determination of the hydrate inhibitor injection parameters during the testing operation is studied, and the influence of the inhibitors' injection concentration and pressure on preventing gas hydrates is analyzed. This work provides useful advice for the prediction and prevention of hydrate formation risk in the development of deep-water gas fields, especially in the South China Sea. [ABSTRACT FROM AUTHOR]

Successful exploitation of tight sandstone gas is one of the important means to ensure the "increasing reserves and production" of the oil and gas initiative and also one of the important ways to ensure national energy security. To further improve the accuracy of historical matching of field data such as gas production and bottom-hole pressure during the production process of this type of gas reservoir, in this study, a new expression of wellbore pressure for the uniform flow of vertical fractured wells in Laplace space based on the point sink function model of vertical fractures in tight sandstone gas reservoirs is constructed. This innovation is based on a typical production data analysis plot of the Blasingame type that uses the numerical inversion decoupling mathematical equation. After analyzing the pressure and pressure derivative characteristics of each flow stage in the typical curves, a new technique of type-curve matching was proposed. In order to verify the correctness of the model and the application value of the field, based on the previous production data of Sulige Gas Field in China, a new set of production data diagnostic chart of tight sandstone gas reservoir was formed. A case analysis showed that the application of the production data analysis method and data diagnosis plot in the field accurately evaluated the development effect of the tight sandstone gas reservoirs, clarified the scale of effective sand bodies, and provided technical support for optimizing and improving the well pattern and realizing the efficient development of gas fields. [ABSTRACT FROM AUTHOR]

Rock materials show dramatic dynamic weakening in large-displacement (m), high-velocity (~1 m/s) friction experiments, providing a mechanism for the generation of large, natural earthquakes. However, whether such weakening occurs during induced M3-4 earthquakes (dm displacements) is unknown. We performed rotary-shear experiments on simulated fault gouges prepared from the source-, reservoir- and caprock formations present in the seismogenic Groningen gas field (Netherlands). Watersaturated gouges were subjected to a slip pulse reaching a peak circumferential velocity of 1.2-1.7 m/s and total displacements of 13-20 cm, at 2.5-20 MPa normal stress. The results show 22%-81% dynamic weakening within 5-12 cm of slip, depending on normal stress and gouge composition. At 20 MPa normal stress, dynamic weakening from peak friction coefficients of 0.4-0.9 to 0.19-0.27 was observed, probably through thermal pressurization. We infer that similar effects play a key role during induced seismic slip on faults in the Groningen and other reservoir systems. Plain Language Summary During large, natural earthquakes, rapid sliding motion on faults through several meters of displacement generates large amounts of frictional heat. This triggers mechanisms that cause crushed fault rocks to weaken drastically, allowing the rupture to propagate, and the earthquake to grow. However, whether this occurs during relatively small, human-induced seismicity, caused by hydrocarbon production or fluid injection in the subsurface, for example, is unknown. Here we simulate seismic fault slip during magnitude 3 to 4 earthquakes, using crushed rock materials derived from the seismogenic Groningen gas field (Netherlands). Our experiments show that even for shortdisplacement (dm), representative for such induced earthquakes, the fault rocks weaken significantly (22%-81%), depending on mineralogy and on the normal stress acting on the fault. These findings provide insights for the larger induced events recorded in Groningen (magnitude up to 3.6), and improve hazard assessment capabilities using numerical models. [ABSTRACT FROM AUTHOR]

Carbonate reservoirs are the main reservoir types in China, which occupy the large ratio of reserves and production at present. The high-efficiency development of carbonate reservoirs is of great significance to assure the stability of national energy supply. The Lower Paleozoic reservoir in Jingbian gas field and the Sinian reservoir in Anyue gas field are two typical carbonate gas reservoirs, and their successful development experiences can provide significant references for other similar carbonate gas reservoirs. For Jingbian gas field, it is a lithological-stratigraphic reservoir developed in a westward monocline and multiple rows of nose-fold structures, and is a stable craton basin with simple palaeognomy distribution and stable connectivity, which has complex gas-water distribution. However, for Anyue gas field, it is a lithological-structural reservoir with multiple tectonic high points and multiple fault systems, and is biological dune beach facies under extensional setting with highly differentiated inside of the block in palaeognomy characteristics, which has limited connectivity and tectonic side water is in a local area. The difference of gas reservoir characteristics leads to the diverse development strategies. For these two gas reservoirs, although there are some similar aspects, such as the screen of enrichment areas, the application of irregular well pattern and reservoir stimulation techniques, the criteria of enrichment areas, the well types, and the means of reservoir stimulation are absolutely different. In addition, due to the differences of control reserves and production capacity for these two kinds of reservoirs, the mode of stable production is also different. The effective development of Jingbian gas field can give some references to the future exploitation on the Sinian gas reservoir. Firstly, the sedimentary characteristics should be studied comprehensively. Secondly, the distribution pattern and distribution characteristics of the palaeognomy should be found and determined. Thirdly, the distribution of fracture system in the reservoir should be depicted finely. Finally, dynamic monitoring on the production performance should be strengthened, and the management for this gas field should be improved further. The findings of this study can help for better understanding of the Karst weathering-crust carbonate gas reservoir formation characteristics and the optimal development technologies that should be taken in practice. [ABSTRACT FROM AUTHOR]

The hydrogeochemical characteristics of coalbed-produced water can provide insights into the sources of ions and water, the groundwater environments, hydrodynamic conditions, and water-rock interactions of depositional basins. To study the water-rock reaction process and reveal whether there is a microbial activity in the groundwater, a case of the Dafosi biogenic gas field was chosen by testing the ionic concentrations and hydrogen and oxygen isotopic compositions of coalbed-produced water and employing R-type cluster and principal component analyses. The results showed that Na+, Cl − , and HCO3- are the principal ions in the coalbed-produced water, while the water type is mainly a Na–Cl. Due to the hydrolysis of HCO3-, the pH in this region was controlled primarily by HCO3-. As the main cation in water, Na+ contributed substantially to the total dissolved solids. Na+ is also related to the exchange between rock-bound Na+ and Ca2+ and Mg2+ in water or surrounding rocks. The coalbed-produced water's oxygen isotopes displayed a characteristic 18O drift and enrichment, indicating that the 16O isotope in the water was preferentially exchanged with the coal organic matter. Early evaporation is also contributed to the enrichment of TDS (total dissolved solids) and 18O in the water. The central part of the study area, including the Qijia anticline, was affected by the Yanshanian uplift and denudation and subsequently developed a water-conducting fissure zone and was recharged atmospheric precipitation; these conditions were conducive to the formation of secondary biogenic gas. [ABSTRACT FROM AUTHOR]

The oil and gas fields are commonly developed with a group of production wells. Therefore, it can be essential for the industries to predict the performance of the production wells in order to optimize the development strategies. In practice, it frequently happens that we only hope to study the performance of a single production well. In such cases, it can be time consuming to run the reservoir simulation with the entire reservoir model to study the well performance. Hence, it can be preferred to determine the control volume (or drainage volume) of the target well from the entire reservoir and run the simulation with the small control volume to reduce the simulation cost. However, an irregular layout of the production wells and the heterogeneity of reservoir properties, which can be commonly observed in real field cases, can induce a stringent barrier for one to determine the control volumes. At present, we are still lacking a method to determine the control volumes of the production wells considering well distribution and reservoir heterogeneities. In order to overcome such a barrier, the authors proposed a new approach to divide the entire reservoir into small control volumes on the basis of the fast marching method (FMM). This approach is validated by comparing the simulation outputs of the target well calculated only with the determined control volume to those calculated with the entire reservoir model. The calculated results show that using the control volume that is determined with the proposed method to calculate the well performance can yield results that agree well with the results that are calculated with the entire reservoir model. This indicates that this proposed method is reliable to determine the control volume of the production wells. In addition, the calculated results in this work show that changing fracture length exerts a slight influence on the control volumes if the length of all fractures is increased, whereas, if only one of the fracture lengths is increased, the control volume of the corresponding well will be significantly increased. The number of the production wells and the distribution of the production well can noticeably influence the control volumes of the production wells. The findings of this study can help for optimizing the well spacing, estimating the ultimate recovery, and reducing the computational cost. [ABSTRACT FROM AUTHOR]

The architecture analysis of the different orders sedimentary bodies is of great significance to the efficient development of oil and gas fields. In order to investigate the effects of the architectural interfaces on reservoir quality and heterogeneity, this study takes the Gudong oil field as a case to investigate the architectural characteristics of hierarchical bounding surfaces using detailed descriptions of core and wireline logs. Architectural models from the 7th-order to the 3rd-order are analyzed, and the developmental characteristics of the 5th-order braided river, 4th-order single sandstone, and 3rd-order accretion are summarized. The interlayer between two braided rivers is floodplain mud deposition, with poor physical properties, stable thickness, and strong blocking capacity. Two models of interlayers are found in the 4th-order deposition. The first interlayer is between the braided filling channel and midchannel bar, which is composed of generally fine-grained sediments with calcium cementation and poor physical properties. The second interlayer is a transformation belt between two midchannel bars and is generally composed of gravel-scoured deposition with penetration capability. The 3rd-order surfaces are defined as the surfaces of accretions within midchannel bars. Two models of interlayers are also found in the 3rd-order surfaces of accretions. The paleocurrent of the sandy braided river is reconstructed by synthesizing the core data, well logging data, and production performance data. A total of 1 fluvial system (7th-order), 2 compound braided rivers (6th-order), 11 braided rivers (5th-order), 41 midchannel bars (4th-order), and 96 accretions (3rd-order) are developed in the study area. [ABSTRACT FROM AUTHOR]

With the presence of highly permeable pathways, such as faults and fractures zones, coal seam gases, particularly CO2, could potentially migrate upwardly from the coal deposits into the shallow subsurface and then to the atmosphere. This letter reports soil gas mapping and gamma ray survey in coal basin of Hunter River Valley, Australia. The survey facilitated the delineation of fault structures across the sampling regions, where the identified faults were confirmed by an independent drilling investigation later. Furthermore, to evaluate the gas emission fluxes from coalbeds through fault zones, the measured CO2 concentrations, coupled with an inverse modeling, enable the estimation of the width of the fault zone and associated CO2 emission flux in the range of 2 × 10−5–6 × 10−5 mol/m2/s at the study site. Our new approach provides a way to determine emissions of gases from deep formations, which may contribute considerably to the greenhouse gases cycles. Plain Language Summary: Australia is one of the world's biggest coal exporters. Total fugitive emissions in Australia have increased in line with the expanding coal and gas production sector. CO2 emissions may occur during the operation and following the closure of coal mines and coal seam gas fields. Leakage of gases to the atmosphere may be induced through fractured gas‐bearing strata and open vents. Hence, the emissions of CO2 from coal basins should be counted toward the overall emissions budget. The new approach proposed by the current study can be applied to estimate emissions of CO2 from fracture and fault zones, which have not been well quantified and yet can be potentially an important source of greenhouse gases contributing to the overall budget at a global scale. So this work could provide a better track progress on international emission commitments. Key Points: Field assessments on gas emission fluxes from coal basin at fault zones in the Hunter River Valley, AustraliaSoil gas mapping and gamma ray survey delineated several fault structures across the sampling transects, which were later confirmed by an independent borehole drilling investigationAn inverse modeling is applied to determine the width of the fault zone and its CO2 emission flux at the study site [ABSTRACT FROM AUTHOR]

The Achimov Formation is one of the most important oil- and gas-bearing strata in the West Siberian basin in Russia. The total estimated reserves of this stratum exceed one billion tons. The formation was first explored in 1981, but it remains largely underdeveloped due to its deep burial depth and poor physical properties. Therefore, further research on the genetic mechanisms and distribution characteristics of the reservoirs in the formation can contribute to its further exploitation. The Achimov Formation is dominated by of fine- to medium-grained sandstones interbedded with shale. Based on analysis of well logging data, hand specimens, and previous research, this study analyzed the properties of three members (Ach1, Ach2, and Ach3) of the Achimov Formation and summarized their distribution patterns. Research on reservoir rocks from different oil and gas fields reveals varying physical properties across the formation with permeability and porosity increasing from the northern to central areas and decreasing from the central to the southern areas. Burial depth is one of the major controlling factors for reservoir properties in the formation. Reservoirs in both the northern and southern parts of the formation are buried deeper than those in the central areas, resulting in a disparity in reservoir quality. [ABSTRACT FROM AUTHOR]

Gas transport in shale matrix is complex due to multiple mechanisms and is difficult to be investigated by macroscopic experiment. For Gas Research Institute (GRI) method, which is the most accepted one for gas transport investigation in shale matrix, the apparatus was modified by adding an automatic gas supplement and pressurization (AGSP) system, and a numerical model considering the variation of real gas property and the Klinkenberg effect was established for data interpretation. Then, the intrinsic permeability and Klinkenberg coefficient were effectively obtained by maintaining high expanding speed of gas in apparatus and eliminating the negative effect of low filling degree of sample. By analysis, the ideal gas transports faster than real gas due to the viscosity difference at low pressure and the deviation factor difference at high pressure. For Wufeng-Longmaxi shale matrix, the positive influence of Klinkenberg effect on gas transport would attenuate with increasing pressure and is more powerful than bulk shale sample with fractures. Therefore, the gas transport in real shale matrix could be well known, which is meaningful to production forecast and evaluation in oil and gas fields. [ABSTRACT FROM AUTHOR]

Dual‐mixed refrigerant (DMR) process is a promising candidate for liquefying the natural gas (LNG) at onshore as well as offshore sites, thanks to its higher liquefaction capacity and flexibility in using full gas turbines. DMR involves two mixed refrigerant cycles to perform precooling and subcooling of natural gas (NG), and these refrigerant compositions need constant tweaking to match the ever‐changing NG cooling curve, as it is obtained from different gas fields. Mismatching of cooling curves often results in suboptimal operation, which ultimately leads to an increase in the overall energy consumption. Thus, this study is aimed at making DMR liquefaction operation close to optimal using the invasive‐weed paradigm. At first, the decision variables for performance improvement were determined using degrees of freedom analysis then through invasive‐weed paradigm the best set of parameters that results in minimal overall energy consumption were obtained. For the given set of conditions, it was found that after optimization, the DMR process can produce LNG using 16.2% less compression power compared to the published optimized DMR process. Taking into account the higher sensitivity of the DMR process against NG feed conditions, the IWO approach was also examined to find the multiple optimal solutions corresponding to different sets of feed conditions. The thermodynamic evaluation revealed that the mixed refrigerant involves in NG subcooling and interstage coolers have the highest level of exergy destruction. After successful performance improvement of the DMR process, it is also found that still, 62% improvement potential (based on avoidable/unavoidable exergy destruction analysis) is available in the DMR process that can be attained through either sole optimization or optimal retrofitting/revamping. [ABSTRACT FROM AUTHOR]

Although the Sulige gas field has been developed for several years, accurate reservoir classification, evaluation, and prediction is still a worth-exploring scientific issue as this is a necessary procedure which could give the guidance of well deployment during later gas field development. Here, based on the analysis of lithological features and diagenesis, we give an evaluation of gas reservoirs in the western Sulige gas field by using the improved method of gray relational analysis. Our results show that the study area Su-54 block is dominated by low permeability and low porosity litharenite and lithic silicarenite with clear evidence of strong diagenesis processes. Compaction is believed to be relatively strong due to the great burial depth and destroy most of the primary pores. Based on the premise of a lower limit of an effective reservoir, we select five parameters (permeability (K), porosity (Φ), effective sand thickness (M), effective sand/sand thickness ratio (D), and gas saturation ( S g )) to calculate the correlation coefficient, relational degree, and index weights for reservoir quality evaluation. By weighted gray correlation theory, the dynamic testing data—effective thickness of gas production data—is used as mother sequences. The results show that the predicted favorable areas for gas exploration and development coincide well with sedimentary and sand body distribution (e.g., point bars and central bars) in the study block; well blocks such as s372, s373, s374, and e24 could be future key development targets. This also indicates a broader application of the gray relational analysis to quality evaluation and distribution prediction of reservoirs. Therefore, our findings could give a new theoretical and practical guidance for the later gas exploration and development, for the search of hidden stratigraphic lithological traps, and for the improvement of the proven rate of oil and gas resources in this area. [ABSTRACT FROM AUTHOR]

With the continuous development of gas fields, water production problems are seriously affecting production rates. Aiming at the problem of the high production rates of mineralized formation water in China's gas fields, we investigate the feasibility of a foam for gas well deliquification process using a combination of nanoparticles and surfactants. Through the combination of anionic and non‐ionic surfactants, a system with better foam stability is optimized by the hand‐shock method. Based on the formation of hydrogen bonds between the fatty alcohol polyoxyethylene ether and SiO2 nanoparticles, the fatty alcohol polyoxyethylene ether created hydrophobicity after silica was added. Adsorbed on the gas–liquid interface, the dilatational modulus of the gas–liquid interface increased, the shift time extended, and the diameter of the generated foam is smaller, that is, a unit volume of gas can carry more liquid. Foam stability can be adjusted by altering the pH value of the foam for gas well deliquification. Last, the oil resistance of the system was improved by adding fatty alcohols. Here, a foam for gas well deliquification was established by the combination of surfactant, nanoparticles, and fatty alcohols, which has good foaming performance, stability, and oil resistance. [ABSTRACT FROM AUTHOR]

The Siberian Platform, covering a vast area of East Siberia (Russian Federation), represents one of the largest underexplored regions in Asia. Previous expeditions and regional surveys in the twentieth century, however, suggest that the Siberian Platform and adjacent orogenic belts hold significant potential for large undiscovered gold, copper, diamond and industrial mineral deposits, along with extensive oil and gas fields. The remoteness of the region, its inhospitable winter climate, and a major lack of modern infrastructure and mining methods have long hampered exploration in this area. These factors, along with the additional investment required and political uncertainties involved with operating in Russia, have deterred many international mining companies from considering the Siberian Platform as a viable region for exploration and mining. However, as mining industry paradigms change into a green, battery metals‐driven commodity sector, and modern mining methods are developed, increasing efficiency at a lower cost, the significant undiscovered mineral potential of the Siberian Platform could elevate the region to the forefront of mineral exploration and mining in the future. [ABSTRACT FROM AUTHOR]

For more than three decades, the depleted Rongchang gas reservoir in China's Sichuan Basin was used for the disposal of unwanted water, which resulted in induced earthquakes, with magnitudes as high as 5.2. After all wells were closed, the frequency of seismic activity was observed to decay following a modified Omori law, and since April 2015, seismic activity again began to increase, and a M4.9 earthquake occurred on 27 December. The results of an epidemic‐type aftershock sequence (ETAS) model analysis show that forced seismicity accounted for more than 70% of the total events. For most M ≥ 3.5 earthquakes, including two M ≥ 4 events, the estimated overpressure was lower than the maximum injection pressure. These results, coupled with the fact that postinjection seismic activity has similar characteristics to seismicity during injection, indicate that the injected overpressure fluid was still the driving factor for postinjection seismic activity. Plain Language Summary: Prior to 2013, unwanted water was intermittently pumped into the depleted Rongchang gas reservoir at a depth of 3 km for approximately three decades, inducing many earthquakes with a magnitude up to 5.2. Although all nearby injection wells were closed in 2013, the seismicity in the area has remained relatively high. At this location, M4.9 and M4.0 earthquakes occurred in December 2016. In order to assess the situation, we carried out an integrated study focused on the area's seismicity before and after the injections ceased. The results, including the overpressure required for major earthquakes and various statistical features, suggest that the postinjection seismicity, which was the same as that during injection, was caused by the delayed rupture of preexisting faults within the reservoir and its surrounding faults. Therefore, at an injection site, at which significant injection‐induced earthquakes occurred during injections, there is still a high probability of continuous occurrence of relatively large earthquakes after injection ends. Key Points: Long‐term injection for wastewater disposal into the depleted Rongchang gas reservoir induced earthquakes with magnitudes as large as 5.2After shutting down of injection, seismicity decayed following a modified Omori law with some major eventsPostinjection seismicity demonstrates features similar to that during injection except for a change in event rate [ABSTRACT FROM AUTHOR]

Energy has become the driving force for national infrastructure development, including the socioeconomic development of every society. Ghana, like many other African countries, formulated developmental policies to attain middle-income status in the medium term. Socioeconomic growth comes with an upsurge in electricity consumption. Ghana seeks to use industrialization to achieve its middle-income target. To achieve this target, there is a need to develop a reliable, sustainable and affordable energy supply in a benign environment. The entry point for Ghana to become a middle-income economy is a cost-effective and reliable electricity supply. Ghana is endowed with fossil fuel, hydro and renewable resources to drive its industrial ambitions, but the indigenous gas fields feeding some thermal plants for electricity production are decreasing and could run out by early 2030 unless new fields are discovered and may also be affected by price volatility. The untapped hydro resources are also small and unreliable if the country seeks to become a middle-income country. Despite the abundant renewable resources, they are intermittent and do not present a baseload option. In safeguarding Ghana's energy security, the country seeks to include nuclear energy into her energy mix. This research paper discusses the major drivers for nuclear energy inclusion. [ABSTRACT FROM AUTHOR]