Search

The unconfined compressive strength (UCS) is a crucial factor of rock strength parameters for estimating the in situ stresses of the rock, designing the most effective fracture design, predicting the best mud weight, and mitigating drilling issues. UCS is commonly determined by subjecting rock samples to uniaxial or triaxial strains until they fail. Laboratory tests provide a direct and more precise estimation of UCS. However, it is unable to generate a continuous profile along the well (i.e., limited to specific depth intervals) due to the presence of specimens, expense, and time consumption. Consequently, other approaches were devised to overcome the gaps in the UCS prediction by utilizing wire-line log data. Several empirical correlations for predicting UCS are derived from well-log data, particularly the porosity, density, and sonic logs. In this paper, the previous correlations for predicting the UCS of carbonate formation have been evaluated using measured data of UCS. The results show that the compressional wave velocity (VP) is the best well log parameter for estimating carbonate formation's unconfined compressive strength, and Yasar and Erdogan correlation best predicts the UCS that fit the measured data for carbonate formations. Thus, Yasar and Erdogan correlation has been chosen to estimate a continuous profile of UCS across the entire depth of carbonate formation in the Rumaila oil field. [ABSTRACT FROM AUTHOR]

In order to avoid potential personnel and financial losses, the evaluation of pre-drilling safety is of great importance in oil and gas exploration and development. This paper presents a method of evaluating pre-drilling safety through combining the Analytic Hierarchy Process (AHP) with the Alternating Condition Expectation (ACE) method. An indicator system with a 9-3-1 structure was established, incorporating various unrestricted variables to describe the technical factor. Additionally, nine membership functions and weights were determined in order to build the AHP model by connecting the independent variables in the basic layer to dependent variables in the middle layer. Four transformed functions were also formulated to construct the ACE model by linking the middle variables to the pre-drilling safety value in the final layer. A total of 28 sets of on-site drilling data from three oilfields were collected for the establishment and verification of the AHP-ACE model. Average absolute error (AAE) and average absolute relative error (AARE) of the model to predict the training data are 0.03 and 4.29%, respectively, whereas the AAE and AARE for verification samples are 0.03 and 4.51%, respectively. The sensitivity ranking of the three potential variables is as follows: human factor exhibits the highest degree of sensitivity, followed by natural factor and technical factor, in descending order. The AHP-ACE model for pre-drilling safety assessment faces limitations in universal applicability and scope, particularly in real-time drilling activities. However, its potential for improvement lies in integrating insights from past operations and expanding the dataset to enhance accuracy and broaden safety assessment coverage. This method is not limited by blocks, which is of great significance to ensure drilling safety. [ABSTRACT FROM AUTHOR]

Copyright of Uranium Geology is the property of Uranium Geology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The coal fines output is the key factor restricting the development of coalbed methane.Factors affecting coal fines output include static factors and dynamic factors.Drilling engineering is one of the important dynamic factors affecting coal fines output.Taking Liulin coalbed methane block as an example, this study established 2D and 3D models by ANSYS software from the perspective of the wellbore stability, and simulated the force and deformation of the borehole wall under different drilling orientations, drilling fluid density, wellbore size, and wellbore inclination.The influence of factors in drilling engineering on the coal fines production was analyzed for the coalbed methane horizontal well.Results show that borehole size and inclination on coal fines production exert greater effect than borehole orientation and drilling fluid density.When the borehole orientation is along the direction of the maximum horizontal in-situ stress, it demonstrates the biggest difference in the equivalent stress around the borehole, and the most obvious stress concentration.Excessive density drilling fluid will lead to tensile failure of the wellbore.In the process of horizontal well drilling, the larger the radius of the wellbore and the larger the inclination of the well, the easier it is to generate coal fines.In order to reduce the generation of coal fines caused by drilling factors, it is suggested that when drilling horizontal wells in the study area, the borehole orientation should be along the direction of the minimum horizontal in-situ stress, the horizontal section should be drilled with clear water, and the inclination of the horizontal section should be consistent with the inclination of the coal seam.The research results provide a theoretical basis for the control measures of coal fines.

Ultrashort-Radius Horizontal Well (URHW) drilling engineering plays an important role in increasing the recovery factor of old oilfields. By sidetracking old wellbores at a very high build-up rate, the URHW can effectively exploit the residual oil near old wellbores. Currently, the main problem faced in URHW drilling engineering is the reduced torque received by drill bits owing to the increased friction between the flexible drilling assembly and wellbore as the horizontal section extends, which greatly limits oil production from a single trip. To tackle this problem, we proposed an innovative machine design, a Dynamic Flexible Drill Rod (DFDR), to provide extra torque near the drill bit to extend the horizontal section of the URHW. The interior structure and working principle of the DFDR were illustrated. The mechanical properties of the DFDRs critical load-bearing part were examined via simulation. The torque and pressure loss characteristics were analyzed using computational fluid dynamics. Corresponding modifications were made to optimize the design, with model machines produced accordingly. Field trials were carried out based on old wellbores in Chunliang District, Shengli Oilfield. The DFDR-based technique extended the URHWs horizontal section in this area by 13.38% on average. [ABSTRACT FROM AUTHOR]

A new special electromagnetic fishing device for large diameter wells is developed. Based on the structural design of the device, the characteristics, key functions and research significance of its electromagnet module, removable pulley module, resistance reduction and flow diversion module, optional fishing basket module, water cooling technology and waterproof technology are discussed, and its application test is carried out. The results show that the electromagnetic fishing device developed for large diameter wells operates stably and reliably with high success rate of fishing and strong inter-well commonality, which can meet the needs of handling metal falling accidents in large diameter drilling construction.

In wellbore stability analysis, the inputs data have a certain range of errors and some uncertainties in terms of data source reliability. Hence, it is important to assess the effect of the input uncertainties on the performance of geomechanics modeling. The cumulative uncertainty in the outputs can be quantified to improve drilling decisions. However, limited studies have been reported in terms of risk assessment for drilling operations utilizing different failure criteria. This research was dedicated to enhance the reliability of uncertainty models in wellbore stability domains. In this study, a stochastic model was established utilizing Mohr–Coulomb and Mogi–Coulomb failure criteria. The Monte Carlo simulation is a probabilistic approach utilized to determine the mud weight as a probability distribution. The results indicated that the maximum horizontal stress has the most influence on the wellbore instability analysis. The presented probabilistic approach with rock failure criteria can quantify the influence of uncertainty to manage the drilling operations with uncertain conditions. Field cases in southern Iraq, Tanuma formation, have been used to validate the proposals of this study. The presented model can be used as an enhancement approach to the currently available tools used for designing drilling programs. [ABSTRACT FROM AUTHOR]

In order to solve the problem of No. 2 coal seam water hazards during the roadway tunneling process of the water-rich coal seam in northern Yuheng Mining Area, taking Balasu Coal Mine as an example, and combining the previous mining experience, firstly, the advanced drilling engineering （short drill + long drill） and the hydrochemical analysis in the rock roadway are carried out, and then the drainage water exploration ideas for the tunneling of the special coal seam water hazards in this area is proposed. The results show that the water drainage effect of the drilling project of No.2 coal seam in the early stage is remarkable, and the water volume and water pressure attenuation of each drill hole are obvious, indicating that the water recharge condition of No.2 coal seam is poor, and the whole coal seam belongs to the state of static water occurrence. Through the full analysis test of coal seam water, it is found that the water quality type of No.2 coal seam is basically SO4-Na·（Ｃａ） type water, with the pH value between 7.63-8.04 and a total salinity of 5 820.88 mg/L to 6 202.99 mg/L. It is believed that the water runoff and discharge conditions are limited and the water is in a closed state for a long time, which is conducive to the development of water drainage. Therefore, the ideas of drainage water exploration suitable for the roadway tunneling of No.2 coal seam in this area is proposed, including drilling technical schemes such as “double funnel mode”, “advance screen mode”, “lower coal drainagemode” and “bilateral feather mode”.

The malignant leakage of complex formations seriously restricts the drilling time and has become a major drilling technical problem that needs to be solved urgently at this stage. In particular, the malignant leakage of large fractures and fractured formations is difficult to construct, and the success rate of plugging is low. In this paper, according to the above formation conditions, by analyzing the leakage mechanism of the malignant leakage formation, the method of plugging the large fractures and broken fractured formations is summarized. The adiabatic copolymerization co-hydrolysis method was used as the gel synthesis method, 2-methacrylic acid amide and acrylamide (AM) were used as the main raw materials, and the redox initiation system composed of sodium sulfate and sodium bisulfite was used as the initiator. Using its redox initiation characteristics, high-strength bonding between organic polymer covalent bonds was achieved by a self-made cross-linking agent; using the thermoplasticity of hot-melt adhesive, the initiator is wrapped in hot-melt adhesive particles to achieve high-temperature slow-release initiation, and finally, a gel plugging agent with good compatibility with drilling fluid, controllable gel formation time, stable gel formation, and good gel breaking performance was synthesized, which is suitable for severe lost circulation under high-temperature and high-pressure conditions. A compatibility study of gel and common drilling fluid systems, the effect of temperature on gel formation, gel rheological properties under high temperature and high pressure, gel start-up pressure, and gel breakability tests were evaluated under laboratory conditions. The experimental results show that the gel has good compatibility with common drilling fluid systems; with the increase of temperature, the gel time of the gel plugging agent gradually decreases, and the gel time can be adjusted from 1 to 3 h at a high temperature of 150°C; when the concentration of the gel in the experimental slurry exceeds 2%, its rheological properties change abruptly; under certain conditions, the starting pressure of the gel can reach up to 6.5 MPa; and under the condition of 150°C, the gel breaking rate was over 98% after 24 h. Various experiments show that the gel’s performance meets the requirements for plugging malignant leakage formations, and the effect is good. Compared with traditional gel materials, the gel plugging agent synthesized in this paper has the characteristics of a simple configuration process and superior performance with drilling fluid, which provides a new idea for malignant leakage plugging.

Measurement while drilling (MWD) technology is important for obtaining downhole parameters. As an essential parameter in drilling engineering, lateral force provides a powerful reference basis for judging the downhole drilling direction. Although stress measurement technology has matured, research on downhole lateral forces, especially near-bit lateral forces during the drilling process in petroleum exploration, is lacking. Based on the force analysis of a short measurement circuit, the lateral force measurement value of a drill bit and centralizer was converted to a drill string's radial-bending-force measurement. Two perpendicular lateral force components were measured using strain gauge technology, a lateral force measurement theory model was established, and a set of MWD systems was designed according to the model. The systems' function was verified through laboratory and field tests, and the field-test data were successfully obtained in the field application. The test results showed that the tested MWD system had acceptable accuracy, stability, and reliability and had the application potential to measure lateral force in the drilling industry. This article provides a new idea to study lateral force while drilling, which is of great significance to oil-drilling exploration and development. [ABSTRACT FROM AUTHOR]

The problem of creating unwanted fractures while drilling ultradeep wells is mitigated with the application of wellbore strengthening techniques. Despite the numerous applications, an open question remains about the efficiency of the loss of circulation materials (LCM) and its implications on the closure stress distribution change during plugging. This work investigates the effects on the stress field before and after plugging along the fracture extension axis by introducing a hydrodynamic plug. With the hydrodynamic plug, fluid flow is constrained by pressure conditions at specific locations in the fracture simulating the LCM. Three different scenarios were considered. First, the efficiency of the bridge is simulated by varying the pressure drop. Second, the location of the bridge inside the fracture and finally a nearly packed fracture. The models are fully coupled and were solved with the finite element method in impermeable and permeable hard rocks. We find that for high‐efficiency bridges, narrower fracture profiles are predicted, which causes the induced closure stresses to increase significantly. On the other hand, when the bridge is close and near the wellbore area, the fracture profiles are maintained wide and narrow when it is nearest to the tip. The predicted fracture geometry induces higher closure stresses when the plug is near the well and slightly reduces when it is near the tip. Finally, the pressure profile resulting from the packed fracture significantly affects the fracture dimensions, resulting in narrower fracture, however resulting in a smooth variation of induced closure stresses with high magnitude comparable to the stresses at the state of propagation. The diffusion occurring in the permeable case creates back‐stresses that appear to have an additive contribution to the induced closure stresses. This underlines the significance of diffusion on the induced coupled closure stresses for large fractures while performing wellbore strengthening methodologies. [ABSTRACT FROM AUTHOR]

The successful drilling operation depends upon the achievement of target drilling attributes within the environmental and economic constraints but this is not possible only on the basis of laboratory testing due to the limitation of time and resources. The chemistry of the mud decides its rheological potential and selection of the techniques required for recycling operations. Conductivity, pH, and photometer testing were performed for the physio-chemical characterization of the grass to be used as an environmental friendly drilling mud additive. In this study, different particle sizes (75, 150, and 300 µm) of grass powder were mixed in mud density of 8.5, 8.6, and 8.7 ppg in the measurement of gel strength and viscosity of drilling mud. The grass additive was added in different weight conditions considering no additive, 0.25, 0.5, and 1 g to assess the contribution of grass on the gel strength and viscosity of the drilling mud. The machine learning techniques (Multivariate Linear Regression Analysis, Artificial Neural Network, Support Vector Machine Regression, k-Nearest Neighbor, Decision Stump, Random Forest, and Random Tree approaches) were applied to the generated rheological data. The results of the study show that grass can be used for the improvement of the gel strength and viscosity of the drilling mud. The highest improvement of the viscosity was seen when grass powder of 150 µm was added in the 8.7 ppg drilling mud in 0.25, 0.5, and 1 g weights. The gel strength of the drilling mud was improved when the grass additive was added to the drilling mud 8.7 ppg. Random forest and Artificial Neural Network had the same results of 0.72 regression coefficient (R2) for the estimation of viscosity of the drilling mud. The random tree was found as the most effective technique for the modeling of gel strength at 10 min (GS_10min) of the drilling mud. The predictions of Artificial Neural Network had 0.92 R2 against the measured gel strength at 10 s (GS_10sec) of the drilling mud. On average, Artificial Neural Network predicted the rheological properties of the mud with the highest accuracy as compared to other machine learning approaches. The work may serve as a key source to estimate the net effect of grass additives for the improvement of the gel strength and viscosity of the drilling mud without the performance of any large number of laboratory tests. [ABSTRACT FROM AUTHOR]

Accurate calculation and prediction of wellbore transient surge pressure is essential to ensure drilling safety. Through the analysis of the wellbore flow path, a calculation model of the transient surge pressure in the wellbore annulus was established. The characteristic line method was used for numerical solution, and the transient surge pressure value and the time distribution characteristics of the transient surge pressure in the annulus could be obtained. The calculation results of the drilling process based on the data of a well on site show that the pressure wave propagates in the wellbore flow channel in the form of elastic wave. As the operating speed of the drill pipe increases, the transient surge pressure in the annulus increases. During on-site drilling operations, under the premise of ensuring drilling safety, the impact of transient pressure fluctuations can be reduced by reducing the density of the drilling fluid and the tripping speed. [ABSTRACT FROM AUTHOR]

Copyright of Oil Drilling & Production Technology / Shiyou Zuancai Gongyi is the property of Shiyou Zuancai Gongyi Bianjibu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Ultrashort-Radius Horizontal Well (URHW) drilling engineering plays an important role in increasing the recovery factor of old oilfields. By sidetracking old wellbores at a very high build-up rate, the URHW can effectively exploit the residual oil near old wellbores. Currently, the main problem faced in URHW drilling engineering is the reduced torque received by drill bits owing to the increased friction between the flexible drilling assembly and wellbore as the horizontal section extends, which greatly limits oil production from a single trip. To tackle this problem, we proposed an innovative machine design, a Dynamic Flexible Drill Rod (DFDR), to provide extra torque near the drill bit to extend the horizontal section of the URHW. The interior structure and working principle of the DFDR were illustrated. The mechanical properties of the DFDRs critical load-bearing part were examined via simulation. The torque and pressure loss characteristics were analyzed using computational fluid dynamics. Corresponding modifications were made to optimize the design, with model machines produced accordingly. Field trials were carried out based on old wellbores in Chunliang District, Shengli Oilfield. The DFDR-based technique extended the URHWs horizontal section in this area by 13.38% on average.

Featured Application: The obtained kinds of borehole camera images of long or deep holes in the tunnels of the building Sichuan-Tibet Railway. Digital panoramic borehole imaging technology has been widely used in the practice of drilling engineering. Based on many high-definition panoramic borehole images obtained by the borehole imaging system, this paper puts forward an automatic recognition method based on clustering and characteristic functions to perform intelligent analysis and automatic interpretation researches, and successfully applied to the analysis of the borehole images obtained at the Wudongde Hydropower Station in the south-west of China. The results show that the automatic recognition method can fully and quickly automatically identify most of the important structural planes and their position, dip, dip angle and gap width and other characteristic parameter information in the entire borehole image. The recognition rate of the main structural plane is about 90%. The accuracy rate is about 85%, the total time cost is about 3 h, and the accuracy deviation is less than 4% among the 12 boreholes with a depth of about 50 m. The application of automatic recognition technology to the panoramic borehole image can greatly improve work efficiency, reduce the time cost, and avoid the interference caused by humans, making it possible to automatically recognize the structural plane parameters of the full-hole image. [ABSTRACT FROM AUTHOR]

Drilling industry faces multitude of challenges ranging from resources constraint driven by activity volatility, increasing demand for cost efficiency and its expansion into non-conventional oil and gas drilling such as unconventional resource, carbon capture and storage (CCS), geothermal etc. The geothermal industry in Japan encounters those challenges in addition to higher requirements for drilling efficiency improvement and health, safety and environment(HSE) accountability. These challenges call for a more accurate and extensive well construction planning solution, where operator can mitigate drilling risk and improve the drilling efficiency from the planning phase. The solution shall inherently drive efficiency well planning process where less resources would be required. An innovative well construction planning solution on cloud has been developed to cover all different aspects of the well planning and engineering workflows, delivering a step change in terms of capabilities and efficiency. The capabilities and efficiency are achieved through digital technology combining automatic engineering and validation, big data analytics, concurrent engineering, and project orchestration. Recently the trend of utilizing cloud based digital technology is increasing in the international drilling industry, and one trial project was conducted for a domestic geothermal well construction planning. The efficiency gain and quality improvement of well planning were evidently demonstrated in the trial project with the various positive feedback from the user. The trend of cloud utilization is expected to continue increasing. [ABSTRACT FROM AUTHOR]

Measurement while drilling (MWD) technology is important for obtaining downhole parameters. As an essential parameter in drilling engineering, lateral force provides a powerful reference basis for judging the downhole drilling direction. Although stress measurement technology has matured, research on downhole lateral forces, especially near-bit lateral forces during the drilling process in petroleum exploration, is lacking. Based on the force analysis of a short measurement circuit, the lateral force measurement value of a drill bit and centralizer was converted to a drill string’s radial-bending-force measurement. Two perpendicular lateral force components were measured using strain gauge technology, a lateral force measurement theory model was established, and a set of MWD systems was designed according to the model. The systems’ function was verified through laboratory and field tests, and the field-test data were successfully obtained in the field application. The test results showed that the tested MWD system had acceptable accuracy, stability, and reliability and had the application potential to measure lateral force in the drilling industry. This article provides a new idea to study lateral force while drilling, which is of great significance to oil-drilling exploration and development.

Copyright of Oil Drilling & Production Technology / Shiyou Zuancai Gongyi is the property of Shiyou Zuancai Gongyi Bianjibu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With the development of oil and gas exploration, the drilling proportion of deep and ultra-deep wells is increasing, which leads to the risk of blowout accidents in drilling engineering. The establishment of lost circulation and overflow monitoring methods is of great significance for controlling the blowout accidents and achieving the objectives of safe and high-quality drilling. The main factors that cause the occurrence of lost circulation and overflow were analyzed. Combined with the actual working conditions of oil and gas drilling, taking the total amount of drilling fluid, density and inlet and outlet flow as the monitoring objects, the judgment model of lost circulation and overflow was established. Based on the new model, the overall scheme, software and hardware design of the lost circulation and overflow monitoring system were developed, which could meet the needs of safe and efficient drilling of oil and gas. The field test of the monitoring system has achieved good monitoring and early warning effect in Daqing Oilfield, which proved the working stability and reliability of the monitoring system. [ABSTRACT FROM AUTHOR]

Tight sandstone reservoirs have the characteristics of small pore throat radius, strong heterogeneity, large shale influence, and development of microfractures, making them particularly vulnerable to damage caused by external intrusive fluids, resulting in decreased reservoir permeability. During the drilling process, the drilling fluid will invade the formation, which is harmful for the development of oil and gas wells after production. Considering these characteristics and drawbacks of the current drilling fluid system, this paper compares six major drilling fluid systems commonly used in China's three major oilfields (Huabei Oilfield, Zhongyuan Oilfield, and Chuanqing Drilling). Plugging agent were added to the original formula, and the experiment shows that the drilling fluid formula of Huabei Oilfield has the best blocking effect. Compared with the other drilling fluid, there is one more ammonium salt in the formula, indicating that the ammonium salt sand disc has a better fluid loss reduction effect. Observation by optical microscope shows that the pollution on the sand disc surface is the least after the drilling fluid is contaminated. The lowest degree of damage indicates the strongest reservoir protection ability. Antipollution experiments show that the anti-NaCl pollution can reach more than 15% and the anti-gypsum pollution can reach more than 2%. The EP-B extreme pressure lubrication instrument is used to analyze the drilling fluid lubrication selected in this article. The coefficients are large and the performance is average. The experiment using the JHTP new high temperature and high pressure non-contact smart dilatometer shows that due to the low content of the reservoir swelling clay minerals, the hydration swelling inhibition effects of each system are better, and at the same time in the drilling fluid system KC1 is added to improve the inhibition of the system. [ABSTRACT FROM AUTHOR]

Copyright of Dokuz Eylul University Muhendislik Faculty of Engineering Journal of Science & Engineering / Dokuz Eylül Üniversitesi Mühendislik Fakültesi Fen ve Mühendislik Dergisi is the property of Dokuz Eylul Universitesi Muhendislik Fakultesi Fen ve Muhendislik Dergisi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Petroleum drilling is a high-input, high-risk and high-tech concealed underground project. There are a large number of complex, random and uncertain factors, which can easily lead to a variety of risks such as complexity and accidents, which seriously affects the economic benefits and environmental protection of the system. Drilling site monitoring parameters provide a wealth of construction information and are important data for timely diagnosis of drilling risks. The essence of drilling risk assessment is to study the internal laws between complex downhole accidents and geological parameters and monitoring parameters, and describe them with a functional relationship. Comprehensively considering the influencing factors of the drilling process and the monitoring parameter selection principles such as "high sensitivity, good stability, strong correspondence, small calculation amount and easy direct acquisition", 9 logging parameters such as mud outlet flow rate, hook load, pump pressure, turntable speed, turntable torque, weight on bit, mud volume, mud density, and drilling speed were established as identification variables. Five kinds of drilling conditions, such as normal, lost circulation, overflow, stuck pipe and drilling tool accident, were determined. Finally, a real-time drilling risk assessment method based on neural network and Monte Carlo simulation was established. This method can analyze the downhole working conditions by using on-site engineering parameters and logging parameters, identify the drilling risk types, and consider the uncertainty of monitoring parameters and identification models, and calculate the risk probability of the corresponding downhole complex accidents. The example analysis shows that the results of the drilling risk monitoring and evaluation calculated by the theoretical method are basically consistent with the actual engineering, and can meet the requirements of drilling risk monitoring and evaluation. It can provide reliable technical support for safe and efficient drilling and well site environmental protection. [ABSTRACT FROM AUTHOR]

Digital panoramic borehole imaging technology has been widely used in the practice of drilling engineering. Based on many high-definition panoramic borehole images obtained by the borehole imaging system, this paper puts forward an automatic recognition method based on clustering and characteristic functions to perform intelligent analysis and automatic interpretation researches, and successfully applied to the analysis of the borehole images obtained at the Wudongde Hydropower Station in the south-west of China. The results show that the automatic recognition method can fully and quickly automatically identify most of the important structural planes and their position, dip, dip angle and gap width and other characteristic parameter information in the entire borehole image. The recognition rate of the main structural plane is about 90%. The accuracy rate is about 85%, the total time cost is about 3 h, and the accuracy deviation is less than 4% among the 12 boreholes with a depth of about 50 m. The application of automatic recognition technology to the panoramic borehole image can greatly improve work efficiency, reduce the time cost, and avoid the interference caused by humans, making it possible to automatically recognize the structural plane parameters of the full-hole image.

A research study is conducted to evaluate the well efficiency assessment of horizontal wells in geothermal fields. The study is comprised of developing the field by means of drilling 15 wells, and conducting reservoir simulation. Drilling planning of vertical and horizontal wells are studied together with their respective time and cost estimates. The time estimate of horizontal geothermal wells is benchmarked to previously drilled vertical and horizontal oil wells, since the data belonging to horizontal wells was not available for study. The findings indicate that the horizontal drilling scenario would take only 7 months more than the vertical drilling scenario. Monetary wise; horizontal wells for a geothermal field is estimated to be drilled 41% more in cost. A hypothetical geothermal field model is generated for the simulations, using TOUGH2. The simulations of four scenario sensitivity analyses reveal that drilling of horizontal wells provide efficient energy extraction out of a geothermal field, in comparison having the wells drilled vertically. The approach provides powerful comparison without having made any investment in the hypothetically simulated geothermal field. The study is a novel in kind since in country such as Turkey there is no horizontal well drilled within the geothermal fields. The analysis of the results indicate that energy production from the horizontal wells are greater than the energy production of vertical wells, definitely paying off the additional investment costs for horizontal drilling and completion. • Geothermal horizontal wells are beneficial in energy production and longer pressure sustainability. • The pressure difference in high skin factor; for vertical and horizontal wells revealed considerable difference, on favor of horizontal wells. • The energy production from horizontal wells are greater than vertical wells, paying off for the costs to be invested for horizontal drilling. [ABSTRACT FROM AUTHOR]

Abstract Thermal spallation is an effective drilling technique for hard rock formations. Models based on Weibull statistical failure theory are widely used in the simulation in thermal spallation. The aspect ratio (diameter/thickness), a parameter in Weibull models, is assumed as a constant in the previous simulations of flame-jet spallation. We conducted the flame-jet experiment in granite and collected 280 spalls to calculate the aspect ratio. Results show that the aspect ratio is size-dependent. A new trimodal distribution of aspect ratio is proposed to incorporate in Weibull models to accurately predict the rate of penetration. The comparison results show that the size-dependent aspect ratio has a significant effect on the rate of penetration. Meanwhile, a smaller aspect ratio (6.91) is recommended for the prediction of the surface temperature in the Weibull model, by which the predicted result can get a better match with the published data. Additionally, given the aspect ratio and rock intrinsic strength of 6.91 (dimensionless) and 70 Mpa, a homogeneity factor is recommended between 10 and 17 (dimensionless). This study can provide an accurate aspect ratio for simulating properties of flame-jet spallation in granite using Weibull models. Highlights • A new trimodal distribution of aspect ratio is proposed to be incorporated in Weibull models. • The size-dependent aspect ratio has a significant effect on the rate of penetration. • A smaller aspect ratio (6.91) is recommended for the prediction of the surface temperature in Weibull model. • A homogeneity factor is recommended between 10 and 17. [ABSTRACT FROM AUTHOR]

Abstract The future of oil and natural gas drilling is dependent on deep well drilling operations. Kick tolerance is a concept which is very important for the industry to ensure that the wells are drilled safely. Especially for natural gas wells one of the most important requirements in deep well engineering design is the kick tolerance calculations. The literature survey reveals that there is no global standard utilized for the kick tolerance calculations by any of the operators, drilling contractors or any other official institutions. It is obvious that the industry needs a reliable procedure for kick tolerance calculations not only for safer drilling but also optimized well plannings. In order to test the methodology a data acquisition process has been implemented to collect the data from the literature. A depth based novel kick tolerance calculation methodology that is based on iteration is introduced in this study, which easily identifies if any kick tolerance troubles are going to be encountered or not. The results indicate that with the introduced kick tolerance methodology the engineering teams can design the wells safely provided that the pore pressure and fracture gradient information belonging to the wells are accurate and available as needful. The study outputs the analysis for the well designers in regards to the depths that a well control incident can occur, which differentiates this research study from others by means of identifying the depth ranges for possible well control incidents. The utilization of the novel kick tolerance calculation approach provides an appropriate planning of drilling operations, safer drilling activities and improved capability of natural resource discoveries. Highlights • Prensented a kick tolerance calculation methodology, which is not existing as a standard in oil industry. • The kick volume can be instantly calculated for each wellbore section either in pre-drill or post-drill. • With the proporsed methodology wells can be planned much safely, addressing the well control related risks. • The engineering team can identify the depth stations at which the kick tolerance pose a risk to the wellbore. [ABSTRACT FROM AUTHOR]

Relying on the Ankang second line Xi'an Baqiao River Railway Bridge large-diameter cap pile project, an SH25H hydraulic and pneumatic DTH drill with the drilling technology of slurry positive circulation was developed at the same time using the underwater self-balancing anti-seepage device. Finally, a new method of wet hole formation for fractured and complicated stratum was determined. In summary, the drilling efficiency and quality were greatly improved. The method has pioneered a new way of thinking in the area of large-diameter rock bored-grouting piles. [ABSTRACT FROM AUTHOR]

Copyright of Oil Drilling & Production Technology / Shiyou Zuancai Gongyi is the property of Shiyou Zuancai Gongyi Bianjibu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To improve the corrosion and wear resistance performance of aluminum alloy drill pipes in geological and petroleum drilling applications, a strengthening coating was prepared on the surface of the 2618 aluminum alloy by combining treatment with ultrasonic cold forging technology (UCFT) and micro-arc oxidation (MAO). The effects of the strengthening coating on the corrosion and wear resistance of the aluminum alloy were evaluated by electrochemical and tribological tests. The results demonstrated that the corrosion and wear resistance of the aluminum alloy were improved by the UCFT and MAO technologies, especially the salt corrosion resistance. The corrosion morphology of the strengthening coating primarily included pitting, micro-cracks and NaCl attachment. In addition, the UCFT + MAO composite coating exhibited the best wear performance. The wear rate of the UCFT + MAO composite coating was lower than that of the aluminum alloy by 94%. The results provided support for this excellent surface treatment technology for the corrosion and wear resistance of aluminum alloy drill pipes, and they also present a feasible evaluation method for drill pipes. [ABSTRACT FROM AUTHOR]

Copyright of Oil Drilling & Production Technology / Shiyou Zuancai Gongyi is the property of Shiyou Zuancai Gongyi Bianjibu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Ice cores from ice shelves contain abundant paleoclimatic information and provide essential information concerned with the prediction of future climatic change and global sea level variations. Efficient retrieval of ice cores is always an engineering challenge in polar ice and marine research. Here, we present design and other information of a new hot-water ice-coring drill used in combination with a hot-water drilling system that provides a rapid and environmentally friendly ice coring system. The coring system shares the surface equipment and hydraulic hose with the hot-water drilling system. Tests with the drill were carried out at an ice drill testing facility, and theoretical estimations were performed to predict the rate of penetration (ROP) and water flow rates. The results indicate the optimal water temperature for ice-coring to be 50 °C, and the most suitable water flow rate to be from 42 L/min to 55 L/min. With those drilling parameters, the maximum ROP is 27.8 m/h and the ice cores are 55−59 mm in diameter.