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Geologically, the Sokoto Basin is predominantly a gentle undulating plain with sediments having their local lateral equivalences reminiscence of what is happening in the larger basin. The total thickness from field studies was estimated to be about 1000 m. With the upbeat of petroleum exploration activities in the inland basins of Nigeria, emphasis is increasingly laid on a structural setting favorable to this and other mineral commodities. This study takes advantage of a large volume of surveyed airborne total-field magnetic data over the Sokoto Basin (the southeastern part, of this study). These high-resolution aeromagnetic (HRAM) data have been purchased from the Nigerian Geological Survey Agency (NGSA) where data were corrected for the main field effect leading to anomalies that reflect the effects of the low-inclination area. The anomaly field was further filtered with total gradients, source parameter imaging (SPI), deconvolution, and spectral filters. Pattern, recognition, and depth analyses from these processed data and other subsidiary (digital elevation model: DEM) data have been harvested to give information on the fault expressions within the sedimentary (with delineated sub-basins) and basement rocks. These analyses were accomplished with Geosoft Oasis Montaj (Version 8.3) potential field processing software. Depth estimates from spectrum analysis, Werner and Euler deconvolution operations, and source parameter imaging (SPI) of the magnetic field anomaly show the deepest magnetic basement configuration under the sedimentary portion nowhere exceeding 5 km in depth. Lineament extracted from the crustal field anomaly and from DEM show major E-W, NE-SW, and ENE-WSW as well as minor NW–SE trends. These lineaments correlate with known and unknown geologic features and therefore could be attractions for hydrocarbon accumulation and/or other mineralization. [ABSTRACT FROM AUTHOR]

In the central Tarim Basin, numerous hydrocarbon deposits were found along ultra-deep strike-slip faults, and its evolving progress and formation mechanism are research hotspots. The Paleozoic small-angle X-type strike-slip fault in the Tabei Uplift is the research subject in this article. Based on high-precision three-dimensional seismic data, three structural deformation layers were revealed: the rift system, weak strike-slip deformation and salt tectonics in the deep structural layer (Sinian-Middle Cambrian), the strong strike-slip deformation and karst-dissolution structure in the middle structural layer (Upper Cambrian-Middle Ordovician), and echelon normal faults in the shallow structural layer (Upper Ordovician-Carboniferous). The formation and evolution of strike-slip faults is jointly controlled by the distribution pattern of basement rift and the activities of surrounding orogenic belts, which can be divided into three stages. In the Middle to Late Cambrian, the initial subduction of the Paleo-Asian and Proto-Tethyan oceans precipitated the emergence of two sets of small-angle X-type strike-slip faults, striking NW and NE above the grooves of Precambrian rifts, influenced by local weak compressive stress. Affected by the closure of peripheral paleo-ocean, strike-slip faults deformed considerably in the Middle-Late Ordovician and were reactivated in the Silurian-Carboniferous, forming en-echelon normal faults in the shallow layer. The layered deformation structure of the strike-slip faults significantly affects the accumulation of hydrocarbons. The differential hydrocarbon enrichment of faults in the Tabei Uplift is collectively influenced by the distribution of source rocks and the migration of oil and gas. The topographical features of the Tabei Uplift, along with the distribution of strike-slip faults across tectonic units, have rendered the NE direction the preferential pathway for hydrocarbon migration. Additionally, impacted by the development of en echelon faults, the NE-trending faults offer superior conditions for hydrocarbon preservation and charging condition, compared to the NW-trending faults. [ABSTRACT FROM AUTHOR]

The Cenozoic era in the southwest of Xihu Depression has undergone great changes in tectonic environment such as fault- depression-reversal, and magmatic activity has become frequent, which is of great significance for understanding the relationship between magmatic activity and hydrocarbon accumulation in this area. In this paper, the formation time and spatial distribution location of magma rock mass in this area are depicted by various geophysical means such as edge detection, amplitude attribute filtering, multi-Z value interpretation, and automatic tracking, and the distribution rules and controlling factors of magma rock mass are analyzed. Combined with the evolution of magmatic activity, the influence of magma activity on hydrocarbon accumulation was discussed. The understanding is as follows: (1) The Cenozoic magmatic activity in the southwest of the Xihu Depression was mainly distributed in the northern section of the Tiantai slope belt and near the Tiantai West Fault, and the magmatic activity in the southwest gradually became stronger since the Miocene, and the magmatic activity reached its peak in the early Santan Formation. (2) The distribution of magmatic rock mass is mainly affected by the development of the basement fault system, the hysteresis effect of magmatic activity, the thickness of the sedimentary cover and other factors. (3) The relationship between magmatic activity and hydrocarbon accumulation in this area is positive and negative. Regional magmatic activity accelerates the maturation of hydrocarbon source rocks in the southwest, and is also conducive to the formation of trap morphology. However, late magmatic activity can also destroy early formed traps. [ABSTRACT FROM AUTHOR]

Extensional strike-slip basins have unique structural features that influence both sub-sags and traps. Despite previous investigations into the extension-strike-slip fault system, there remains a gap in the comprehensive analysis of its influence on sub-sag formation and trap development. The Huanghekoudong and Miaoxi'nan sub-sags within the Bohai Bay Basin, intersected by the Tan-Lu Fault Zone, offer exemplary cases for examining the interplay between strike-slip and extensional tectonic regimes. The neotectonic strike-slip movements along the Tan-Lu Fault Zone have given rise to various extensional strike-slip overlap zones in these sub-sags, rendering these locales ideal for investigating the dynamics of strike-slip and extensional tectonic processes. Employing three-dimensional seismic data, well logs, and a newly constructed sequence stratigraphic framework, our research delineates the geometric and kinematic phenomena characteristic of the extensional strike-slip fault system, including the dynamics of extensional fault deformation and interaction through time. By scrutinizing the fault system's vital role in shaping sub-sag evolution and trap genesis, we present a comprehensive model that significantly contributes to our understanding of structural trapping dynamics. This model not only fine-tunes existing trapping models but also offers invaluable insights for future exploration strategies within the Bohai Bay Basin and other similar extensional strike-slip basins worldwide. Our findings highlight the novel and significant implications of the extensional strike-slip fault system in controlling sub-sag and trap features, thus bridging a notable gap in existing geotechnical knowledge. [ABSTRACT FROM AUTHOR]

Ad'Daimah Field is a structural trap with a proven gas condensate reservoir in limestone. The Yamama Formation is the faulted anticline that makes up the field. Thirteen seismic lines were used for this study, with one well (Da-1). Velocity maps derived from the velocity model were used to construct time and depth maps. Certain stratigraphic features were present in the examined reflector, according to seismic interpretation in the region. In the research area, certain distribution mounds and continuous sand lenses in more than two-dimensional seismic lines were seen. These activity components offer a logical justification for the distribution of hydrocarbons in the study region. The major normal fault of (NW-SE) trending and minor normal faults of (NE-SW) trending, both with a bit of displacement, has been seen in the research region. These fault systems influence the examined reflectors (Yamama, Sulaiy). Time, velocity, and depth maps are created according to the selected reflectors' structural interpretation. The structural interpretation of these reflectors reveals an asymmetrical anticline that extends in an E-W trend, plunges to the southeast with a dip angle of about 5 degrees, and generally dips direction toward NE-SW. [ABSTRACT FROM AUTHOR]

The Proterozoic oil in Gaosheng area of the Western Depression of Liaohe Basin has great potential and is an important exploration field. However, the study about control factors of Gaosheng reservoir needs to be improved. The source rocks are characterized by using geochemical techniques and the structural evolution history is restored by using 2D-Move software. The characteristics of reservoirs and caps are clarified, and the controlling factors of reservoir formation are summarized. The oil generation intensity of Es4 and Es3 is generally 5 χ 106-10 χ 106 t/km2, indicating that the oil source is sufficient. The sandstone reservoir has fracture and dissolution porosity, which provide storage space for oil accumulation. Faults and unconformities provide pathways for oil migration. The dense Fangshenpao and Mesozoic basalt is a good cap layer to preserve the reservoir, which effectively prevents the upward migration of oil. According to the comprehensive analysis of main controlling factors, the favorable exploration areas are pointed out. The research results are of great significance to guide the future oil and gas exploration in Liaohe Basin. [ABSTRACT FROM AUTHOR]

In order to address the challenges related to exploration target search and sustainable development of oilfields in the Weixinan Sag of Beibuwan Basin, this study focused on fault-lithologic composite traps within the structural trap development section of the third member of Oligocene Weizhou Formation in the No.2 fracture zone of Weixinan Sag. By examining the relationship between the evolution of depression-controlling faults and the sedimentary characteristics of the third member of Weizhou Formation, it was observed that the No.2 fault zone exhibited weak activity during the sedimentary period of the third member, facilitating the continuous transportation of underwater distributary channels of the braided river delta along the long axis direction of the sag towards the depression. Conversely, the regional tectonic activities were intense during the sedimentary periods of the second and first members of Weizhou Formation, leading to the formation of a series of en-echelon faults. The interaction between relatively isolated underwater distributary channels of the braided river delta front and en-echelon faults resulted in angled staggered formations and intersecting channels, ultimately creating a distinctive channel-type structural-lithologic trap group characterized by NE-SW trending fault sealing and NW-SE trending sand body pinching. The research findings indicate the development of a three-factor coupling fault-lithologic trap model in the third member of the Weizhou Formation. This model includes the depression faulted uplift background of the No.2 fracture zone, low-frequency oscillating channel, and en-echelon tension-torsion fault. The intersection area of the main stream line of underwater distributary channel in a braided river delta and the No.2 fracture zone is identified as a favorable zone for structural-lithologic traps. Additionally, composite structural-lithologic traps are predominantly found in the near-source intersection area, while isolated structural-lithologic traps are more common in the far-source intersection area, leading to the formation of an accumulation model involving axial channel sand control, fault, and sand body composite control. The fault-lithologic trap model and accumulation model have demonstrated effective application in practice. Several favorable fault-lithologic composite trap groups with distinct fault sealing and sand body pinching orientations have been identified, particularly in the Wei B-E structure. Notably, well WB-E 1 has successfully drilled nearly 100 meters of oil layer, with subsequent wells yielding positive results. The exploration efforts in the third member of the Weizhou Formation within the No.2 fault zone of the Weixinan Sag have led to the discovery of geological reserves exceeding 10 million cubic meters, underscoring the significance of fault-lithologic composite traps in this region.

The Ediacaran–Ordovician strata within three major marine basins (Tarim, Sichuan, and Ordos) in China are analyzed. Based on previous studies focusing on the characteristics of the Neoproterozoic–Cambrian strata within the three major basins (East Siberian, Oman, and Officer in Australian) overseas, the carbonate–evaporite assemblages in the target interval are divided into three types: intercalated carbonate and gypsum salt, interbedded carbonate and gypsum salt, and coexisted carbonate, gypsum salt and clastic rock. Moreover, the concept and definition of the carbonate–evaporite assemblage are clarified. The results indicate that the oil and gas in the carbonate–evaporite assemblage are originated from two types of source rocks: shale and argillaceous carbonate, and confirmed the capability of gypsum salt in the saline environment to drive the source rock hydrocarbon generation. The dolomite reservoirs are classified in two types: gypsum-bearing dolomite flat, and grain shoal & microbial mound. This study clarifies that the penecontemporaneous or epigenic leaching of atmospheric fresh water mainly controlled the large-scale development of reservoirs. Afterwards, burial dissolution transformed and reworked the reservoirs. The hydrocarbon accumulation in carbonate-evaporite assemblage can be categorized into eight sub-models under three models (sub-evaporite hydrocarbon accumulation, supra-evaporite hydrocarbon accumulation, and inter-evaporite hydrocarbon accumulation). As a result, the Cambrian strata in the Tazhong Uplift North Slope, Maigaiti Slope and Mazatag Front Uplift Zone of the Tarim Basin, the Cambrian strata in the eastern-southern area of the Sichuan Basin, and the inter-evaporite Ma-4 Member of Ordovician in the Ordos Basin, China, are defined as favorable targets for future exploration.

The process of hydrocarbon accumulation in polycyclic superimposed basins often involves multistage crude oil charging, but not every stage of crude oil charging plays a significant role in the current hydrocarbon accumulation. Fluid inclusion methods can only provide constraints on the stages and time of crude oil charging, but cannot determine the contribution of each stage of crude oil charging for hydrocarbon accumulation. To study the contributions of different stages of crude oil charging for the reservoirs, the Ordovician carbonate reservoirs in the subsalt area, Tahe oilfield (Tahe subsalt area) were taken as an example. This study employed crude oil geochemistry, fluid inclusion analysis, fluorescence spectrum, and single well simulation analysis methods to systematically reveal the fluorescence characteristics of crude oil and hydrocarbon accumulation stages and time of the study area. The analysis of crude oil biomarker parameters indicates that the crude oil has the same parent material and was deposited in a marine weak reducing environment. By comparing the crude oil with the study area's source rocks, it was determined that all the crude oil was derived from the source rocks of the Lower Cambrian Yuertusi Formation. The aromatic methylphenanthrene index and methyldibenzothiophene parameters of crude oil serve as effective indicators for the quantitative evaluation of crude oil maturity. The calculated crude oil maturity (Ro) in the Tahe subsalt area ranges from 0.90% to 1.47%, and this may correspond to multiple stages of oil and gas charging. Based on fluorescence spectrum analysis of oil inclusions and homogeneity temperature and salinity measurements of associated saline inclusions in the Ordovician reservoirs in the Tahe subsalt area and the study area's burial history of single well burial history and thermal history simulation, it was determined that the oil reservoirs in the Tahe subsalt area experienced three stages of crude oil charging during the stages of middle Caledonian (420 Ma), middle Hercynian (318 Ma) and late Himalayan (10 Ma). By comparing the fluorescence spectrum parameters of crude oil and oil inclusions in these three stages, it is concluded that the late Himalayan is the primary stage of hydrocarbon accumulation in the Tahe subsalt area, making the largest contribution for the Ordovician reservoirs in the Tahe subsalt area.

The Southeast Depression of the Tarim Basin has a very low petroleum exploration degree, and currently, no industrial oil and gas have been discovered. Many hydrocarbon shows exist in the Ruoqiang Sag, where hydrocarbon sources and accumulation processes are unclear. Only two potential Jurassic hydrocarbon source rocks developed in the Ruoqiang Sag, the Yangye (J2y) lacustrine mudstone of the Middle Jurassic and the Kangsu (J1k) coal-bearing mudstone of the Lower Jurassic. In this study, the Jurassic asphalt found in the QD1 well, combined with the source rocks of drilling cores and outcrops, was used to explore the possible hydrocarbon source and forming process in the Ruoqiang Sag using oil-source correlation and hydrocarbon accumulation geochronology methods. The asphalts have lower light and heavy rare earth fractionation than the J2y mudstone, and the total rare earth element ^REE) content, chondrite-normalized curves, and δEu and Y/Ho values are similar to those of the J1k mudstone, especially for the J1k coal. The n-alkane ratios of the carbon preference index and the odd-to-even preference (OEP) of Jurassic asphalts are greater than 1.0, indicating that its source rock has experienced low thermal evolution. All Jurassic samples have similar source- related biomarkers but different maturity-related parameters, and the thermal evolution degree of asphalt is close to the J1k mudstone and coal but slightly higher than the J2y mudstone. Meanwhile, rhenium-osmium isotopes show the asphalts are formed in 192+30/-45 Ma, which is similar to the J1k sedimentation time. The asphalts contain coal macerals and probably derived from the asphaltene precipitated by the J1k coal during the early coalification. The low abundance of 25-norbornanes with a non-or slight petroleum biodegradation degree indicates the asphalt was generated relatively late and migrated into the J2y formation along the faults, possibly accompanied by the striking activities of the Altyn Tagh Fault during the Neotectonics movement. This study provides evidence for the J1k coal-bearing strata serving as the effective source rock in the Ruoqiang Sag and increases confidence for Jurassic petroleum exploration in the Southeast Depression of the Tarim Basin. The structural and lithological traps near hydrocarbon source stoves, where Jurassic strata were deeply buried and far from the Altyn Tagh Range, are favorable oil and gas exploration targets. [ABSTRACT FROM AUTHOR]

The H structure is located in the central and southern part of the Xihu Depression central depression structural belt, adjacent to the hydrocarbon-rich Shaoxing 36 depression and divided by multiple faults as a structural trap, which has good conditions for hydrocarbon accumulation. However, currently, the research on faults in this structure is relatively weak, which restricts the exploration of hydrocarbon potential. To clarify the development characteristics of faults and their control over hydrocarbon accumulation, this article starts from 3D seismic data interpretation and drilling data, analyzes the development characteristics and evolution process of H structural faults, conducts research on the control of faults on hydrocarbon accumulation within the structure, and divides hydrocarbon accumulation types. Research shows that the faults within the H structure mainly developed in the Paleogene, the dominant trend was NNE. The faults can be divided into two hierarchical class: source rocks-linking faults and regulative faults. Among them, F1 and F4 faults located on the east and west sides of the structure control the formation of the structure, and fault activity controls the ancient high point. The fault level and fault sand coupling degree can control the abundance of hydrocarbon. Based on the comprehensive analysis of fault activity, source-fault combination types, and transportation models, two hydrocarbon accumulation models were established, providing guidance for the next step of oil and gas exploration in this structure. [ABSTRACT FROM AUTHOR]

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Faults play a pivotal role in controlling fluid migration and retention within sedimentary basins, particularly in the context of fault-bound hydrocarbon reservoirs. Assessing the stability and sealing capabilities of faults enhances our comprehension of these systems and aids in the identification of pathways for fluid migration. In this study, we focus on a series of fault-bound hydrocarbon accumulations located in the southern Wenchang A subbasin within the Pearl River Mouth Basin. We emphasize the significant influence of faults in governing the processes of hydrocarbon migration and accumulation. By leveraging 3D seismic data and well information, we have assessed the sealing potential of ten faults that either currently retain hydrocarbon columns or have the potential to do so. Our analysis reveals that even faults with a relatively low Shale Gouge Ratio (as low as 15%) can effectively support substantial column heights. Taking into account factors, such as the source rock maturity, fault activity, geometry, sealing potential, and the distribution of hydrocarbon accumulations, we have formulated a conceptual model for hydrocarbon migration and accumulation within the study area. This model underscores potential fluid traps within the rift basin, shedding light on the complex dynamics of hydrocarbon movement in this region. [ABSTRACT FROM AUTHOR]

With continuous hydrocarbon exploration extending to deeper basins, the deepest industrial oil accumulationwas discovered below 8,200 m, revealing a new exploration field. Hence, the extent to which oil exploration can be extended, and the prediction of the depth limit of oil accumulation (DLOA), are issues that have attracted significant attention in petroleum geology. Since it is difficult to characterize the evolution of the physical properties of the marine carbonate reservoir with burial depth, and the deepest drilling still cannot reach the DLOA. Hence, the DLOA cannot be predicted by directly establishing the relationship between the ratio of drilling to the dry layer and the depth. In this study, by establishing the relationships between the porosity and the depth and dry layer ratio of the carbonate reservoir, the relationships between the depth and dry layer ratio were obtained collectively. The depth corresponding to a dry layer ratio of 100% is the DLOA. Based on this, a quantitative prediction model for the DLOA was finally built. The results indicate that the porosity of the carbonate reservoir, Lower Ordovician in Tazhong area of Tarim Basin, tends to decrease with burial depth, and manifests as an overall low porosity reservoir in deep layer. The critical porosity of the DLOA was 1.8%, which is the critical geological condition corresponding to a 100% dry layer ratio encountered in the reservoir. The depth of the DLOA was 9,000 m. This study provides a new method for DLOA prediction that is beneficial for a deeper understanding of oil accumulation, and is of great importance for scientific guidance on deep oil drilling. [ABSTRACT FROM AUTHOR]

The Ediacaran-Ordovician strata within three major marine basins (Tarim, Sichuan, and Ordos) in China are analyzed. Based on previous studies focusing on the characteristics of the Neoproterozoic-Cambrian strata within the three major basins (East Siberian, Oman, and Officer in Australian) overseas, the carbonate-evaporite assemblages in the target interval are divided into three types: intercalated carbonate and gypsum salt, interbedded carbonate and gypsum salt, and coexisted carbonate, gypsum salt and clastic rock. Moreover, the concept and definition of the carbonate-evaporite assemblage are clarified. The results indicate that the oil and gas in the carbonate-evaporite assemblage are originated from two types of source rocks: shale and argillaceous carbonate, and confirmed the capability of gypsum salt in the saline environment to drive the source rock hydrocarbon generation. The dolomite reservoirs are classified in two types: gypsum-bearing dolomite flat, and grain shoal & microbial mound. This study clarifies that the penecontemporaneous or epigenic leaching of atmospheric fresh water mainly controlled the large-scale development of reservoirs. Afterwards, burial dissolution transformed and reworked the reservoirs. The hydrocarbon accumulation in carbonate-evaporite assemblage can be categorized into eight sub-models under three models (sub-evaporite hydrocarbon accumulation, supra-evaporite hydrocarbon accumulation, and inter-evaporite hydrocarbon accumulation). As a result, the Cambrian strata in the Tazhong Uplift North Slope, Maigaiti Slope and Mazatag Front Uplift Zone of the Tarim Basin, the Cambrian strata in the eastern-southern area of the Sichuan Basin, and the inter-evaporite Ma-4 Member of Ordovician in the Ordos Basin, China, are defined as favorable targets for future exploration. [ABSTRACT FROM AUTHOR]

In the central Tarim Basin, numerous hydrocarbon deposits were found along ultra-deep strike-slip faults, and its evolving progress and formation mechanism are research hotspots. The Paleozoic small-angle X-type strike-slip fault in the Tabei Uplift is the research subject in this article. Based on high-precision three-dimensional seismic data, three structural deformation layers were revealed: the rift system, weak strike-slip deformation and salt tectonics in the deep structural layer (Sinian–Middle Cambrian), the strong strike-slip deformation and karst-dissolution structure in the middle structural layer (Upper Cambrian–Middle Ordovician), and echelon normal faults in the shallow structural layer (Upper Ordovician–Carboniferous). The formation and evolution of strike-slip faults is jointly controlled by the distribution pattern of basement rift and the activities of surrounding orogenic belts, which can be divided into three stages. In the Middle to Late Cambrian, the initial subduction of the Paleo-Asian and Proto-Tethyan oceans precipitated the emergence of two sets of small-angle X-type strike-slip faults, striking NW and NE above the grooves of Precambrian rifts, influenced by local weak compressive stress. Affected by the closure of peripheral paleo-ocean, strike-slip faults deformed considerably in the Middle–Late Ordovician and were reactivated in the Silurian–Carboniferous, forming en-echelon normal faults in the shallow layer. The layered deformation structure of the strike-slip faults significantly affects the accumulation of hydrocarbons. The differential hydrocarbon enrichment of faults in the Tabei Uplift is collectively influenced by the distribution of source rocks and the migration of oil and gas. The topographical features of the Tabei Uplift, along with the distribution of strike-slip faults across tectonic units, have rendered the NE direction the preferential pathway for hydrocarbon migration. Additionally, impacted by the development of en echelon faults, the NE-trending faults offer superior conditions for hydrocarbon preservation and charging condition, compared to the NW-trending faults.

Extensional strike-slip basins have unique structural features that influence both sub-sags and traps. Despite previous investigations into the extension-strike-slip fault system, there remains a gap in the comprehensive analysis of its influence on sub-sag formation and trap development. The Huanghekoudong and Miaoxi’nan sub-sags within the Bohai Bay Basin, intersected by the Tan-Lu Fault Zone, offer exemplary cases for examining the interplay between strike-slip and extensional tectonic regimes. The neotectonic strike-slip movements along the Tan-Lu Fault Zone have given rise to various extensional strike-slip overlap zones in these sub-sags, rendering these locales ideal for investigating the dynamics of strike-slip and extensional tectonic processes. Employing three-dimensional seismic data, well logs, and a newly constructed sequence stratigraphic framework, our research delineates the geometric and kinematic phenomena characteristic of the extensional strike-slip fault system, including the dynamics of extensional fault deformation and interaction through time. By scrutinizing the fault system’s vital role in shaping sub-sag evolution and trap genesis, we present a comprehensive model that significantly contributes to our understanding of structural trapping dynamics. This model not only fine-tunes existing trapping models but also offers invaluable insights for future exploration strategies within the Bohai Bay Basin and other similar extensional strike-slip basins worldwide. Our findings highlight the novel and significant implications of the extensional strike-slip fault system in controlling sub-sag and trap features, thus bridging a notable gap in existing geotechnical knowledge.

The Study focuses on examining the formation and deposition process of sedimentary formations containing oil and gas in the sedimentary basins on Vietnam's continental shelf. Determining the distribution trend, characteristics, and scale of these sediments is of great importance. By analyzing field samples, lithologic data, references, documents, and conducting geological-geophysical research, the author has investigated the formation process of lower Miocene sediments with oil and gas in the Cuu Long basin. Through the study of identified characteristics, distribution scale, sedimentological features, and seismic data, the author has shed light on the process of formation and the trend of hydrocarbon accumulation in the lower Miocene sedimentary basin of the Cuu Long Basin. The predominant trend of sediment deposition distribution is observed from the continental portion of the Dalat Zone towards the Cuu Long Basin, cutting through it in a west-east direction. Furthermore, the research reveals that the lower Miocene sandstone in the Cuu Long Basin can be divided into two sequences: BI.2 and BI.1, both originating from granitoid sources. These findings also contribute to our understanding of the evolution of magma-sediment processes in the studied area and its surrounding regions. Additionally, tectonic extensions and climate changes, which lead to sea-level rise during the lower Miocene sequence, create favorable conditions for the deposition and accumulation of sedimentary particles.

Clarification of the cause of overpressure is of great significance for the study of hydrocarbon generation, migration and accumulation processes under an overpressure environment, and the prediction of predrilling pressure. The cause of overpressure in Xihu Depression is still controversial. This study, based on mudstone compaction research and organic matter correction of logging data, ascertained the causes of overpressure in the Pinghu tectonic zone, Xihu Depression. A modified discrimination method for overpressure genesis was used and the overpressure–hydrocarbon distribution relationship was explored. The results show the following: (1) Vertically, overpressure is located in the lower section of the Pinghu Formation, with a pressure coefficient of 1.1–1.7 and a pressure relief feature. On the plane, the pressure coefficient in the Pingzhong area exceeds that in the Pingbei area. (2) The main causes of abnormal high pressure in the research area are undercompaction and fluid expansion. The fluid expansion mechanisms include overpressure transmission and hydrocarbon charging within the reservoir as well as hydrocarbon generation pressurisation and overpressure transmission within the source rock. (3) In the surge section of kaolinite, under fluid pressure, kaolin migrates toward the low-pressure areas, decreasing the porosity in low-pressure areas and preserving pores in high-pressure areas. The evolution of fluid pressure can be divided into two stages: pressurisation; and both pressurisation and pressure relief. Pressurisation and pressure relief drive hydrocarbon charging, but hydrocarbons are more enriched in overpressure layers. [ABSTRACT FROM AUTHOR]

Based on the determination of oil-source fault and analysis of its controlling factors for advantageous pathways of hydrocarbon migration, the 3D seismic, well logging and mud logging data are used to study the advantage pathways on the parts of oil-source fault activity, internal lithology and hydrocarbon potential field, and then to comprehensively predict the advantage pathway of oil-source fault. The comprehensive evaluation parameters of advantageous pathways of hydrocarbon migration by oil-source fault are calculated by weighted assignment to determine the favorable range of hydrocarbon accumulation near the oil-source fault. The method is used to predict the advantageous pathways of hydrocarbon migration by F3 oil-source fault in Daliuquan area of Langgu Sag in Mid-Hebei Depression, Bohai Bay Basin. The results show that there are 11 advantageous pathways developed in F3 fault, including 3 of activity, 2 of internal lithology and 6 of section hydrocarbon potential. The favorable hydrocarbon accumulation area near the F3 fault is restricted by the comprehensive evaluation parameter greater than 1.65, which is consistent with the proven hydrocarbon distribution in the study area, indicating that the method is feasible for the prediction of advantageous pathways for hydrocarbon migration in oil-source fault, and helpful for favorable oil-gas target searching. [ABSTRACT FROM AUTHOR]

The platform margins of Gucheng and Luoxi in the Cambrian are developed on both sides of the eastern Tarim Basin. Based on the analysis of cores, thin sections, and seismic data of Luoxi platform margin slope areas, we systematically studied the formation condition, reservoir characteristics, and favourable accumulation factors of gravity flow. The types of gravity flow include debris flow, high‐density flow, and low‐density flow, and the high‐density flow reservoir is better. Hydrothermal fluids have an active effect on reservoir reconstruction. Six‐phase reefs are developed in the platform margin, and the lithology of the reservoir is algal framework dolomite and granular dolomite. Multi‐phase reefs form an inclined slope. The 3D seismic and geochemical data show that the platform margin reefs have karst unconformity characteristics. The platform margin slope has the requirements of geomorphology and reservoir source, and the total area of slope gravity flow is 5854 km2. The gravity flow in the Gucheng platform margin slope is near the Cheerchen fault zone, and tectonic movement forms the nose‐like structure. The gravity flow is between the source rocks of the Xidashan Formation and the Heituwa Formation. Hydrocarbon generation and caprock are both favourable for hydrocarbon accumulation. Multi‐phase events of hydrothermal fluids are favourable to the reservoir and hydrocarbon charging. Gravity flow is important for oil and gas exploration in the Tarim Basin. [ABSTRACT FROM AUTHOR]

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The Proterozoic oil in Gaosheng area of the Western Depression of Liaohe Basin has great potential and is an important exploration field. However, the study about control factors of Gaosheng reservoir needs to be improved. The source rocks are characterized by using geochemical techniques and the structural evolution history is restored by using 2D-Move software. The characteristics of reservoirs and caps are clarified, and the controlling factors of reservoir formation are summarized. The oil generation intensity of Es4 and Es3 is generally 5 × 106–10 × 106 t/km2, indicating that the oil source is sufficient. The sandstone reservoir has fracture and dissolution porosity, which provide storage space for oil accumulation. Faults and unconformities provide pathways for oil migration. The dense Fangshenpao and Mesozoic basalt is a good cap layer to preserve the reservoir, which effectively prevents the upward migration of oil. According to the comprehensive analysis of main controlling factors, the favorable exploration areas are pointed out. The research results are of great significance to guide the future oil and gas exploration in Liaohe Basin.

The Southeast Depression of the Tarim Basin has a very low petroleum exploration degree, and currently, no industrial oil and gas have been discovered. Many hydrocarbon shows exist in the Ruoqiang Sag, where hydrocarbon sources and accumulation processes are unclear. Only two potential Jurassic hydrocarbon source rocks developed in the Ruoqiang Sag, the Yangye (J2y) lacustrine mudstone of the Middle Jurassic and the Kangsu (J1k) coal-bearing mudstone of the Lower Jurassic. In this study, the Jurassic asphalt found in the QD1 well, combined with the source rocks of drilling cores and outcrops, was used to explore the possible hydrocarbon source and forming process in the Ruoqiang Sag using oil-source correlation and hydrocarbon accumulation geochronology methods. The asphalts have lower light and heavy rare earth fractionation than the J2y mudstone, and the total rare earth element (ΣREE) content, chondrite-normalized curves, and δEu and Y/Ho values are similar to those of the J1k mudstone, especially for the J1k coal. The n-alkane ratios of the carbon preference index and the odd-to-even preference (OEP) of Jurassic asphalts are greater than 1.0, indicating that its source rock has experienced low thermal evolution. All Jurassic samples have similar source-related biomarkers but different maturity-related parameters, and the thermal evolution degree of asphalt is close to the J1k mudstone and coal but slightly higher than the J2y mudstone. Meanwhile, rhenium–osmium isotopes show the asphalts are formed in 192+30/−45 Ma, which is similar to the J1k sedimentation time. The asphalts contain coal macerals and probably derived from the asphaltene precipitated by the J1k coal during the early coalification. The low abundance of 25-norbornanes with a non- or slight petroleum biodegradation degree indicates the asphalt was generated relatively late and migrated into the J2y formation along the faults, possibly accompanied by the striking activities of the Altyn Tagh Fault during the Neotectonics movement. This study provides evidence for the J1k coal-bearing strata serving as the effective source rock in the Ruoqiang Sag and increases confidence for Jurassic petroleum exploration in the Southeast Depression of the Tarim Basin. The structural and lithological traps near hydrocarbon source stoves, where Jurassic strata were deeply buried and far from the Altyn Tagh Range, are favorable oil and gas exploration targets.

The Hurenbuqi Sag, located on the Bayinbaolige uplift in the northern Erlian Basin, is a secondary depression rich in oil. In order to study the influence on hydrocarbon accumulation of the Early Cretaceous structures in the southern Hurenbuqi Sag, the geological, drilling and geophysical data has been analyzed carefully to reveal the Early Cretaceous extensional structural characteristics, differential structural deformation characteristics, tectonic evolution process, and the hydrocarbon accumulation process. The study revealed that, extensional tectonic system is the mainly composition of Early Cretaceous structure, it has controlled the three main tectonic subsidence stages, early initial tectonic subsidence, middle rapid tectonic subsidence and late slow tectonic subsidence, of the southern Hurenbuqi Sag. During the tectonic evolution, the Early Cretaceous deformation obviously controlled the development of the source rocks and hydrocarbon accumulation. This study is of great significance for analyzing the enrichment regulations of hydrocarbon and guiding the next oil and gas exploration.

Fault step zones are well developed in faulted lake basins in the eastern part of China, among which, forward fault step zones account for a large proportion, and their spatiotemporal configuration relationship, oil and gas accumulation periods and accumulation conditions, which play a key role in the geological evaluation of regional oil and gas exploration, are difficult to study. In order to further clarify its hydrocarbon accumulation mode and filling period, the authors, by taking the Paleogene Dongying and Shahejie formations in the study area as the main target layers, and selecting wells Qidong 3-1, Zhang 10 and Chenghai 16 to represent the low, medium and high fault levels of the fault area, respectively, conducted in-depth research on the oil and gas properties and distribution laws of different charging stages in various districts of Chengbei through reservoir microlithography observation, fluid inclusion identification, salt water inclusion homogenization temperature and salinity test, GOI statistical analysis and other technologies; applied laser Raman test to effectively identify the gas composition of single inclusions in wells Zhang-10 and Qidong 3-1, determined the specific oil and gas accumulation time in Chengbei fault step zone in combination with the single well burial history, paleogeothermal history and autoclastic illite K-Ar isotopic dating technology of well Qidong 3-1, and summarized the four accumulation elements of source rocks, reservoirs, preservation and transportation in Chengbei area. There are two charging stages in the reservoir, the specific accumulation time of the first stage is from the end of Dongying to the early stage of Guantao, about 16 Ma ±, while that of the second stage is in the early stage of Minghua Town, starting from 6 Ma ± and continuing to the present. Multiple sets of reservoir layers are developed in the study area, and the special fault step structure plays a controlling role in channeling the source rocks and reservoirs, the sealing and preservation of oil and gas, and the transportation and accumulation of reservoirs. The regional accumulation conditions are relatively mature, and the lateral migration-accumulation mode of dual-source hydrocarbon supply and multi-stage accumulation and the longitudinal migration-accumulation mode of fault-sand coupling and relay climbing are reflected in the process of oil and gas accumulation.

Based on outcrop, seismic and drilling data, the main regional unconformities in the Sichuan Basin and their controls on hydrocarbon accumulation were systematically studied. Three findings are obtained. First, six regional stratigraphic unconformities are mainly developed in the Sichuan Basin, from the bottom up, which are between pre-Sinian and Sinian, between Sinian and Cambrian, between pre-Permian and Permian, between middle and upper Permian, between middle and upper Triassic, and between Triassic and Jurassic. Especially, 16 of 21 conventional (and tight) gas fields discovered are believed to have formed in relation to regional unconformities. Second, regional unconformity mainly controls hydrocarbon accumulation from five aspects: (1) The porosity and permeability of reservoirs under the unconformity are improved through weathering crust karstification to form large-scale karst reservoirs; (2) Good source-reservoir-caprock assemblage can form near the unconformity, which provides a basis for forming large gas field; (3) Regional unconformity may lead to stratigraphic pinch-out and rugged ancient landform, giving rise to a large area of stratigraphic and lithologic trap groups; (4) Regional unconformity provides a dominant channel for lateral migration of oil and gas; and (5) Regional unconformity is conducive to large-scale accumulation of oil and gas. Third, the areas related to regional unconformities are the exploration focus of large gas fields in the Sichuan Basin. The pre-Sinian is found with source rocks, reservoir rocks and other favorable conditions for the formation of large gas fields, and presents a large exploration potential. Thus, it is expected to be an important strategic replacement.

The objective of this research was to carry out a petrophysical evaluation and seismic interpretation of Geowil hydrocarbon bearing field in the Niger Delta Region of Nigeria using standard techniques. Three hydrocarbon bearing sands were identified namely reservoir R-1000, R-2000 and R-3000 from the well log data. The result showed that both reservoir R-1000 and R-2000 reveal high resistivity values and low water saturation while reservoir R-3000 indicates that the hydrocarbon contained is oil and gas. Both reservoir R-1000 and R-2000 are observed to be thinning out across the field, reservoir R-3000 is seen to be slightly undulating across the field. The petrophysical computation obtained for the three reservoirs (R-1000, R-2000 and R-3000) revealed that they all have very good average porosity anomalies of 27%, 27% and 25% respectively as well as moderate permeability values (159.974Md, 126.9Md, and 162.02 Md respectively) rating. The hydrocarbon saturation index obtained for all the three reservoir (55%, 54% and 50%) showed that they are all good indicator of prolific hydrocarbon accumulation. The result of the volume of hydrocarbon originally in place and the volume that can be recovered estimated revealed that R-1000 has STOIIP of 262.47MMSTB, R-2000 has 2.66MMSTB and R-3000 has 42.67MMSTB. The ultimate recovery for the three reservoirs is 19.31MMSTB, 1.19MMSTB, and 19.2MMSTB respectively. This implies that the reservoir has great potential for oil resources in considerable size. [ABSTRACT FROM AUTHOR]

The Sichuan basin has a great potential for hydrocarbon exploration. In recent years, Permian strata have been identified as one of the main target strata for natural gas exploration in the Sichuan basin. Not only the source rocks are abundant, but also there are good reservoirs due to the wide and complex continental oceanic interaction. However, there are still many shortcomings, especially the relationship between the tectonic evolution and the hydrocarbon accumulation model. Therefore, this research aims at understanding the characteristics of paleo-highs/lows of the Permian strata and their controlling effects on hydrocarbon migration/accumulation in the Sichuan basin. Firstly, the distribution patterns of paleo-highs/lows in the Permian strata at each critical tectonic period were constructed by integrating spatial erosion calculation. Then the temporal evolution of the Permian strata at each critical tectonic period will be revealed by restoring the upper strata sequentially. The results of this research improve the precision of paleo-highs/lows reconstruction and provide useful hints for the hydrocarbon exploration of the Sichuan basin: (i) Paleo-highs/lows directly determine the development location of the Permian key reservoirs; (ii) Tectonic evolution controls many factors and the process of hydrocarbon accumulation. [ABSTRACT FROM AUTHOR]

The objective of this research was to carry out a petrophysical evaluation and seismic interpretation of Geowil hydrocarbon bearing field in the Niger Delta Region of Nigeria using standard techniques. Three hydrocarbon bearing sands were identified namely reservoir R-1000, R-2000 and R-3000 from the well log data. The result showed that both reservoir R-1000 and R-2000 reveal high resistivity values and low water saturation while reservoir R-3000 indicates that the hydrocarbon contained is oil and gas. Both reservoir R-1000 and R-2000 are observed to be thinning out across the field, reservoir R-3000 is seen to be slightly undulating across the field. The petrophysical computation obtained for the three reservoirs (R-1000, R-2000 and R-3000) revealed that they all have very good average porosity anomalies of 27%, 27% and 25% respectively as well as moderate permeability values (159.974Md, 126.9Md, and 162.02 Md respectively) rating. The hydrocarbon saturation index obtained for all the three reservoir (55%, 54% and 50%) showed that they are all good indicator of prolific hydrocarbon accumulation. The result of the volume of hydrocarbon originally in place and the volume that can be recovered estimated revealed that R-1000 has STOIIP of 262.47MMSTB, R-2000 has 2.66MMSTB and R-3000 has 42.67MMSTB. The ultimate recovery for the three reservoirs is 19.31MMSTB, 1.19MMSTB, and 19.2MMSTB respectively. This implies that the reservoir has great potential for oil resources in considerable size.

Transfer zones are structural areas of faults interactions where fault motion or displacement can be transferred from one fault to another, regional strain maintains laterally constant. Transfer zones are widely developed in rift basins and have significance on hydrocarbon accumulation. In this review article, we attempt to summarize recent advances on the types, distance-displacement curves, evolutionary stages and controlling factors of transfer zones in rift basins and their effects on sedimentary systems, reservoir properties, trap formation and hydrocarbon migration. The formation of transfer zones is genetically related to the segmented growth of normal faults. Depending on the degree of interaction between these normal faults, transfer zones in rift basins could be divided into two types: soft-linked and hard-linked, which are further subdivided into transfer slope, oblique anticline, horst and transfer fault based on the combination patterns of normal faults. In general, the development of transfer zones experiences several stages including isolated normal faulting, transfer slope forming, complicating and breaking. During the interaction and growth of segmented normal faults, stress-strain and spatial array of faults, pre-existing basement structures, and mechanical conditions of rocks have a great influence on the location and development processes of transfer zones. A transfer zone is commonly considered as a pathway for conveying sediments from provenance to basin, and it hence exerts an essential control on the distribution of sandbodies. In addition, transfer zone is the area where stresses are concentrated, which facilitates the formation of various types of structural traps, and it is also a favorable conduit for hydrocarbon migration. Consequently, there exists great hydrocarbon potentials in transfer zones to which more attention should be given. [ABSTRACT FROM AUTHOR]

Langshan Branch Fault is the dominant fault controlling Jartai Structural Belt in Hetao Basin and the hydrocarbon accumulation of many high-capacity oil-gas wells has close evolutional relationship with the formation of the fault. The geometric characteristics and motion characteristics of Langshan Branch Fault were analyzed based on 3D seismic data and well-drilling data. According to the changes in fault displacement, and occurrence of the fault, Langshan Branch Fault was divided into three sections: north section, middle section and south section. Based on reverse fault theory, the inversion types and stages of the fault were made clear. A model was established with the method of formation tendency. and the drilling well sound wave time-difference point-control correction method was adopted to calculate the original thickness of the stratum of the hanging wall and the footwall and recover the ancient fault displacement of the fault, 6 different calculation methods were summarized for three kinds of growth faults including the normal fault, the reverse fault and the negative inversion to quantify and calculate the activity rate of each fault section in different depositional stages. The quantitative evaluation of the activity characteristics of the faults at north section, middle section and south section was carried out. Based on the comparison of the balanced cross-sections and analysis of the activity rate, it was deemed that Langshan Branch Fault experienced four evolution stages. There were three "isolated" faults with different trends and strikes in the early stage of development. In the depositional stage of the Lisangou Formation in the Early Cretaceous, the sectionalized thrusting existed and the north section and the middle section of the fault were flexibly connected. In the depositional stage of Guyang Formation, all thrust faults in the sections were reversed into the normal faults. It was strongly extended from the Paleogene to the Neogene, and the northern section and the middle section of the fault were hard-connected as a whole fault. From Late Neogene to the Quaternary, the fault underwent the local strike-slip twist, and these three sections of the fault were formally linked into the present connected fault. The activity of this fault in different historical stages obviously controlled the development of the sedimentary system of both the hanging wall and the footwall, the formation and evolution of traps, and the migration and accumulation of oil and gas.

With the great discovery of unconventional oil in the Fengcheng Formation in the Mahu sag, the Wuxia fault belt, which shows similar lithological characteristics and lithofacies, is considered the most favorable area for future petroleum exploration. However, the complicated structural patterns remain unclear and restrict the petroleum exploration and development. In this study, combined with new seismic data and some borehole data, we conclude the structural styles in the Wuxia fault belt and analyze their distribution characteristics, and further investigate their implications for tectonic evolution and hydrocarbon accumulation. Five typical seismic sections are captured from the west to the east of the fault belt. Decollement folds and fold accommodation faults superimpose on the underlying basement fault related folds. Structure patterns also show a zonation in S–N direction and a segmentation in E–W direction. The balanced section reveals that the present-day structure features were fundamentally formed by Late Permian. The structural deformation shows distinctive features of a foreland basin which may develop in Early Permian and continue until the Late Permian. The oil reservoirs in the Fengcheng Formation in deeper detachment fold and the autochthonous Fengcheng Formation in fault propagation folds are the most favorable regions for further unconventional petroleum exploration.

Faults play a pivotal role in controlling fluid migration and retention within sedimentary basins, particularly in the context of fault-bound hydrocarbon reservoirs. Assessing the stability and sealing capabilities of faults enhances our comprehension of these systems and aids in the identification of pathways for fluid migration. In this study, we focus on a series of fault-bound hydrocarbon accumulations located in the southern Wenchang A subbasin within the Pearl River Mouth Basin. We emphasize the significant influence of faults in governing the processes of hydrocarbon migration and accumulation. By leveraging 3D seismic data and well information, we have assessed the sealing potential of ten faults that either currently retain hydrocarbon columns or have the potential to do so. Our analysis reveals that even faults with a relatively low Shale Gouge Ratio (as low as 15%) can effectively support substantial column heights. Taking into account factors, such as the source rock maturity, fault activity, geometry, sealing potential, and the distribution of hydrocarbon accumulations, we have formulated a conceptual model for hydrocarbon migration and accumulation within the study area. This model underscores potential fluid traps within the rift basin, shedding light on the complex dynamics of hydrocarbon movement in this region.

The Guantao Formation is the most important reservoir with significant faces developed, and this is different from the near-source accumulation of Nanpu sag. Guantao Formation in Matouying Uplift was found far away from the source area, which is a typical accumulation outside sources. What is the difference on accumulation condition and main controlling factors between the far-source accumulation and near-source accumulation? And what is the reasonable explanation for these reservoirs? According to the main controlling factors of Guantao Formation reservoir in Matouying Uplift, the abundant accumulation in hydrocarbon generation sag, efficient transport system and good spatial and temporal configuration of reservoir cap rock are the main controlling factors for its hydrocarbon accumulation outside sources. The hydrocarbon movement follows a migration model when it passes through a multiple faulted terrace zone and an effective connection to faults has an increase in the hydrocarbon abundance. The determination of oil sources and the correct understanding of the transport system are the keys to the reservoir understanding of the Guantao Formation in Matouying Uplift, as well as to the establishment of the reservoir model and the prediction of favorable oil and gas development areas. It provides enlightenment for the exploration of reservoir outside sources in peripheral convex and although oil and gas displays have been seen during single-well drilling, no large-scale reservoirs have been discovered until the industrial flow of oil and the results enrich the future exploration trend and potential areas in the uplift around the Nazione and Npu sag are determined. [ABSTRACT FROM AUTHOR]

Mahu sag is an important hydrocarbon-rich sag and a large stratigraphic lithologic reservoir exploration field in the northwestern Junggar Basin, forming a large stratigraphic lithologic reservoir with multiple layers. In order to find out the distribution law of oil and gas in this area and provide geological basis for the next exploration deployment, based on core observation and comprehensive analysis of seismic, logging and other data, the structural sequence analysis method was applied to study the main oil and gas reservoir series from Permian to Triassic. The results show that there are many large stratigraphic unconformity surfaces from Permian to Triassic in Mahu sag, which can be divided into Lower Permian, Middle Permian, Upper Permian-Triassic and other structural sequences. From Permian to Triassic, it experiences three major evolution stages of fault depression, depression and large depression slope, forming the superposition of three major structural sequences. The Lower Permian is a dustpan structural sequence formed under the extensional tectonic background; the northern stratum is thick, and the southern stratum is thin; it is deposited under the dustpan structure background of deep north and shallow south; the depression area is widely distributed fine-grained mixed rock, which is constructed of high-quality hydrocarbon source rock, and gradually becomes sandstone and conglomerate towards the slope area. The Middle Permian is a structural sequence with thick central and thin peripheral margins under the tectonic background of depression; the basin margin fan delta is developed, which is characterized by large basin, shallow water, limited basin margin fan body, and interbedded sediment of sand and mud in the basin. In Upper Permian-Triassic, Mahu area is located in the northwest slope area of Junggar large depression basin; under the background of shallow water, gentle slope and lacustrine transgression, the large retrogressive fan delta deposits are formed, and the sand bodies are vertically superimposed and horizontally distributed. The vertical superposition of the three major structural sequences forms the multi-layer distribution of stratum-lithologic or structure-lithological reservoirs in the area. [ABSTRACT FROM AUTHOR]

The Qaidam Basin is a Cenozoic continental basin formed by the subduction and collision between the Indian plate and the Eurasian plate. It is the only large oil- and gas-bearing basin in China on the Qinghai–Tibet Plateau. The Qaidam Basin has recorded the uplift of the plateau with its complete Cenozoic sequences. Therefore, studying the structural characteristics of the Qaidam Basin helps us to understand the uplift of the Qinghai–Tibet Plateau. Studies have shown that the structural activities in the Qaidam Basin were episodic, transformable, and inconsistent, which reflected the characteristics of the uplift of the Qinghai–Tibet Plateau. In general, the structural activities of the Qaidam Basin are divided into three phases, which are characterized by the shifting of structural activities from the south to the north, the west to the east, and from the margin to the hinterland of the basin, respectively. The intensity of the early activity was greater than that of the early basin in both time and space. In conclusion, the uplift of the Qinghai–Tibet Plateau controls the structural and sedimentary characteristics of the basin and ultimately, the hydrocarbon accumulation and distribution of the basin. [ABSTRACT FROM AUTHOR]

According to the latest three-dimensional seismic stratification data, the Triassic source rocks are recognized to be deeply buried on the southern slope of Kuqa Depression, Tarim Basin, making it possible to develop local source rocks. Based on geochemical data and basin simulation, the burial history, thermal history and maturity evolution history of Triassic source rocks in this area were simulated and analyzed. By discussing the thermal evolution and maturity process of source rocks, the maturity stage and hydrocarbon generation stage of source rocks were proposed and their reservoir forming significance was further discussed. The source rocks of the Triassic Karamay Formation are distributed on the southern slope of Kuqa Depression. The burial depth in the southern area of Xinhe is generally about 6 700 m, which tends gradually to deepen in the north and reaches themaximum depth over 8 000 m, showing an overall characteristics of "shallowly buried in the south and deeply buried in the north". The southern slope of Kuqa Depression has the same overall subsidence amplitude, which has experienced the tectonic evolution process of stable burial in the early stage, continuous subsidence in the middle stage and rapid burial in the late stage. During the Triassic period, the strata were deposited stably and the burial depth was small. From Cretaceous to Paleogene, continental clastic rocks were mainly deposited, and the strata continued to deposit. From Neogene to present, the southern slope of Kuqa Depression entered the stage of rapid thermal subsidence, and the burial depth reached the largest. The evolution degree of Triassic source rocks on the southern slope of Kuqa Depression is characterized by "high degree in the north and low degree in the south". The northern region matured early, which entered the hydrocarbon generation threshold at the beginning of Paleogene (Ro=0.5%), evolved to mature stage by the end of Paleogene (Ro=0.7%) and to high maturity stage in the middle Neogene (Ro=1.0%) and till now (Ro=1.30%), mainly generating gas. The southern region matured relatively late, which entered the oil window in the early Neogene, reached mature stage in the middle Neogene (Ro=0.7%), and till now (Ro=0.86%), mainly generating oil. There are two oil and gas transportation of far-source and near-source on the southern slope of Kuqa Depression, which provides sufficient sources for oil and gas accumulation. This area has the overall characteristics of dual source hydrocarbon supply.

Aiming at the differential distribution of overpressure in vertical and lateral directions in the foreland thrust belt in the southern margin of Junggar Basin, the study on overpressure origin identification and overpressure evolution simulation is carried out. Based on the measured formation pressure, drilling fluid density and well logging data, overpressure origin identification and overpressure evolution simulation techniques are used to analyze the vertical and lateral distribution patterns of overpressure, genetic mechanisms of overpressure in different structural belts and causes of the differential distribution of overpressure, and the controlling effects of overpressure development and evolution on the formation and distribution of oil and gas reservoirs. The research shows that overpressure occurs in multiple formations vertically in the southern Junggar foreland thrust belt, the deeper the formation, the bigger the scale of the overpressure is. Laterally, overpressure is least developed in the mountain front belt, most developed in the fold anticline belt, and relatively developed in the slope belt. The differential distribution of overpressure is mainly controlled by the differences in disequilibrium compaction and tectonic compression strengths of different belts. The vertical overpressure transmission caused by faults connecting the deep overpressured system has an important contribution to the further increase of the overpressure strength in this area. The controlling effect of overpressure development and evolution on hydrocarbon accumulation and distribution shows in the following aspects: When the strong overpressure was formed before reservoir becoming tight overpressure maintains the physical properties of deep reservoirs to some extent, expanding the exploration depth of deep reservoirs; reservoirs below the overpressured mudstone cap rocks of the Paleogene Anjihaihe Formation and Lower Cretaceous Tugulu Group are main sites for oil and gas accumulation; under the background of overall overpressure, both overpressure strength too high or too low are not conducive to hydrocarbon enrichment and preservation, and the pressure coefficient between 1.6 and 2.1 is the best.

The fluid distribution is considerably influenced by the reservoir homogeneity. This study analyzes carbonate reservoir heterogeneity and hydrocarbon accumulation processes in the Khasib reservoirs in AB oilfield in the Middle East to discuss factors controlling the distribution of fluid and the effects of this distribution on the productivity of single wells. The Khasib reservoirs in the AB oilfield show uniform vertical distributions, with a large difference in the longitudinal pore throats, and the upper part of the reservoir is better than the lower one. Because the hydrocarbon accumulation is multiphasic, the heterogeneity of crude oil is based on whether traps are formed in the early or late stage of source rock formation during accumulation. Moreover, the longitudinal physical differences in crude oil properties are mainly attributed to the longitudinal differences in the pore throats. The difference in the pore throat and physical properties of crude oil affords differences in the productivity of horizontal wells in different subzones.

The discovery of an oil reservoir in Pishan Caldera of the Tarim Basin, northwest China, highlights the hydrocarbon exploration potential of large calderas. We used 3 D seismic interpretations, waveform clustering analysis, and seismic profiles to investigate the origin and evolution of Pishan Caldera, along with the mechanisms of hydrocarbon accumulation, and its significance for future oil and gas exploration. Pishan Caldera is located at depths of >7000 m, has an elliptical shape, extends over an area of 25 × 20 km, and is surrounded by ring faults. Pishan Caldera were the result of magma withdrawal and later magma intrusion. Volcanic eruptions, caldera collapse, and reactivation of Pishan Caldera resulted in Cretaceous oil migration and accumulation in Cretaceous breccia reservoirs. Ring faults, dense fracture networks, and lava tubes associated with the caldera acted as conduits for upward hydrocarbon migration. We propose a generalized model for hydrocarbon reservoirs related to the caldera, which includes five major reservoir types: drape anticline, fault block, volcanic-trapped, laterally sealed and lava tube type. Further efforts should be made to identify deep caldera structures that may be targets for hydrocarbon exploration. [ABSTRACT FROM AUTHOR]

[Display omitted] • Monazite U-Th dating identifies two fluid flow events in the Sichuan Basin. • These events relate to Proto-Pacific Ocean subduction and Emeishan mantle plume. • Monazite U-Th isotopes can date fluid flow, oil charging, gas generation events. Obtaining precise ages of the Phanerozoic fluid flow events of petroliferous basins is essential for understanding the tectonothermal histories, petroleum- and ore-forming processes. Conventional isotopic dating methods are often compromised by inheritance from detrital constituents and/or subsequent thermal resetting. Monazite is a trace mineral widely present in low-grade metasedimentary rocks, and as an excellent U–Th–Pb geochronometer it has great potential in dating fluid flow activities related to basin evolution. We present results of an in-situ monazite U-Th-Pb geochronology study on shale samples from the Neoproterozoic (651 Ma) Datangpo Formation intersected by a drill-hole in the Sichuan Basin, a typical petroliferous basin in western South China. We recognized two fluid flow events at ca. 450 Ma and ca. 263 Ma, and relate the former to the far-field effect of the Proto-Pacific Ocean subduction and the latter to emplacement of the Emeishan large igneous province. We infer that the ca. 450 Ma fluid flow event induced the first stage of oil charging in the paleo oil pools in the Sichuan Basin, as also recorded by the bitumen samples from the Anyue gas field which yielded re-Os isotopic ages of 458–492 Ma, whereas the ca. 263 Ma event triggered the gas generation of the Paleozoic marine strata in the Sichuan Basin. The results and findings of this study have important implications to reconstructing the complex histories of fluid flow, oil charging and gas generation events of petroliferous basins. [ABSTRACT FROM AUTHOR]

Reconstructing karst palaeogeomorphology is a useful approach to identifying target areas for oil and gas exploration. This study used the elevation method to reconstruct the karst palaeogeomorphology at the top of the 4th member (Z2dn4) of the Dengying Formation (Z2dn) in the Central Sichuan Basin based on 2D and 3D seismic and drilling data. The bottom of the Longwangmiao Formation and the top of the 2nd member (Z2dn2) of the Z2dn were optimized as the upper and lower base levels, respectively. The reconstructed palaeogeomorphology was divided into five types – slopes, erosional peneplains, monadnocks, domes and depressions – according to their morphology, scope and gradient, allowing inference of the palaeohydrological conditions. Slopes were subdivided into gentle (<1.2°) and steep (≥ 1.2°; maximum gradient around 16°). Reservoirs on steep slopes and monadnocks are the most developed, owing to their considerable hydraulic head differences, strong palaeohydrodynamics, and intense erosion and incision. Steep slopes with more developed karst porosities are banded and immediately adjoin a regional hydrocarbon generation centre. Hydrocarbons generated in this centre tend to migrate laterally and become entrapped in porous slopes and their vicinities. Consequently, hydrocarbons move upward along steep slopes and, preferentially, slopes and monadnocks. Thus, the steep slope zone and its vicinity (including some monadnocks, gentle slopes and peneplains) are the most favourable areas for exploration of hydrocarbon reservoirs and should be the primary targets. [ABSTRACT FROM AUTHOR]

The Lower Cretaceous Bayingebi Formation at the Hari sag, Northern China is a significant bearing oil-gas tight reservoir in the Yin'E Basin. In order to understand petrophysical properties of the reservoirs, the diagenesis and hydrocarbon accumulation phases were investigated using casting thin sections, scanning electron microscopy (SEM), X-ray diffraction and fluid inclusion analysis. Additionally, the histories of burial evolution, organic matter thermal evolution and hydrocarbon charge are investigated. The results showed that the pore types include primary pore, intergranular pore and dissolution intragranular pore. The diagenesis of sandstone reservoirs in the process of burial and diagenesis mainly includes compaction, fracture, cementation, metasomatism and dissolution. The comprehensive analysis of various diagenetic stage indexes shows that Bayingebi Formation is in the middle diagenetic stage A-B. The homogenization temperature and salinity of fluid inclusions are low temperature and low salinity (120 °C ∼ 130 °C, 0% ∼ 9%), medium temperature and high salinity (140 °C ∼ 150 °C, 10% ∼ 17%) and high temperature and medium salinity (160 °C ∼ 170 °C, 9% ∼ 11%) respectively. According to the homogenization temperature of the inclusions and the history of burial evolution, the Bayingebi Formation has mainly three phases of hydrocarbon accumulation (100 ∼ 97Ma, 93 ∼ 87Ma, 84 ∼ 81Ma). [ABSTRACT FROM AUTHOR]