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    Xinjiang Oil & Gas    2024, 20 (1): 0-0.  
    Abstract88)      PDF (13817KB)(331)       Save
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    Research Progress on Capture of CO2 by Alcohol Amine Absorption Method
    YANG Tianmeng, YANG Fan, REZEY Rehemtuli, GOU Guolei, LI Xiuhui, HOU Junwei
    Xinjiang Oil & Gas    2024, 20 (1): 52-60.   DOI: 10.12388/j.issn.1673-2677.2024.01.007
    Abstract279)      PDF (3625KB)(314)       Save

    CO2 capture,utilization,and storage are the main technologies to cope with the greenhouse climate,achieve the strategic goal of carbon peak and neutralization,lead the transformation and upgrading of the global energy system,and promote the green and sustainable development of energy. The chemical absorption methods have the characteristics of high absorption efficiency and large processing capacity,most suitable for large-scale carbon capture in various industries. Among them,the alcoho lamine method is the most widely used and the most effective. After absorbing CO2,the alcoholamine solution becomes an alcoholamine-rich solution,which can be recovered by desorption treatment for cyclic utilization. However,in the process of CO2 capture by the existing alkanolamine absorbent,there are some disadvantages such as high energy consumption and great loss of absorbent,and it is necessary to improve the alcoholamine absorber to realize high absorption efficiency and a feasible process with low regeneration energy consumption. To solve the problems of large loss of absorbent and low regeneration rate,a new mixed alcoholamine absorber was developed for improvement. For the problem of high energy consumption for regeneration,the traditional thermal desorption process is improved and microwave desorption technology is selected. This paper introduces the mechanism and characteristics of CO2 absorption by alcoho lamine method,summarizes the basis for improving the mixed alcoholamine absorber,and expounds on the principle and characteristics of CO2 capture through microwave-assisted alcoholamine,providing a reference for industrial carbon capture and environmental protection.

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    Research Status and Development Proposal of ROP Improvement Technology with Percussion Rock-Breaking Method
    LI Gensheng, MU Zongjie, TIAN Shouceng, HUANG Zhongwei, SUN Zhaowei
    Xinjiang Oil & Gas    2024, 20 (1): 1-12.   DOI: 10.12388/j.issn.1673-2677.2024.01.001
    Abstract170)      PDF (7836KB)(182)       Save

    Enhancing the rate of penetration (ROP) is crucial for optimizing the efficiency of oil and gas development and deep exploration in China and ensuring national energy security. The percussion rock-breaking drilling technology has been applied in oil fields at home and abroad,resulting in significant improvements in ROP. Further research efforts are expected to address the technical challenges of low drilling footage and limited ROP enhancements encountered during deep exploration of hard rock formations with high temperature and pressure. This paper presents and analyzes the practice and development trends of the drill bit percussion rock-breaking drilling technology assisted by axial percussion,torsional percussion,and axial-torsional coupled percussion. It illustrates that the percussion-assisted drill bit rock-breaking mechanism is the core of percussion rock-breaking ROP improvement technology. This paper also reviews the scientific advancements made by domestic and overseas research scholars in physical experiments,theoretical modeling,and numerical simulation of percussion-assisted drill bit rock-breaking. In addition,it offers relevant proposals for the development of percussion rock-breaking ROP improvement technology,i.e. advancing research on material structure optimization design,intelligent control,integration of multiple technologies,and optimization of well applications. This is expected to provide valuable insights for enhancing the drilling efficiency in energy development of our country.

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    Research and Application Progress of Nanofluid for Enhanced Oil Recovery

    LIANG Tuo, YANG Changhua, ZHANG Yanjun, LI Pan, QU Ming, HOU Jirui
    Xinjiang Oil & Gas    2023, 19 (4): 29-41.   DOI: 10.12388/j.issn.1673-2677.2023.04.004
    Abstract172)      PDF (5519KB)(168)       Save

    In view of the limitations of traditional polymer and surfactant solutions in enhancing oil recovery,such as low viscosity retention and large adsorption loss,this paper examines the potential use of nanofluids for enhanced oil recovery and discusses recent research in this field. First,the synthesis of nanomaterials is described,and the methods used for evaluation of the stability of nanofluids in enhanced oil recovery in the field are summarized. Second,six mechanisms by which nanofluids enhance oil recovery are reviewed. These are:reducing interfacial tension,changing wettability,reducing crude viscosity,improving foam stability,structural disjoining pressure,and reducing pressure and increasing injection. Third,the use of nanofluids for enhanced oil recovery in the field is investigated. The “bottleneck” issues that limit the large-scale application of nanofluids in oilfields are also described. For example,there are currently no nanofluid flooding systems available for efficient development of unconventional reservoirs. Furthermore,there has been insufficient theoretical and technical discussion and research. More integrated research is required on inter-related matters such as the development of nanofluids containing two-dimensional nanosheets,determination of the mechanisms for enhanced oil recovery,and field pilot testing of the process. Finally,a direction for the practical introduction and application of nanofluids is proposed.

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    Research Progress on the Mechanisms and Control Methods of Casing Deformation in Shale Gas Horizontal Wells#br#
    YIN Aobo , LI Jun, , LIAN Wei , ZHANG Hui
    Xinjiang Oil & Gas    2025, 21 (1): 50-60.   DOI: 10.12388/j.issn.1673-2677.2025.01.006
    Abstract33)      PDF (3254KB)(131)       Save

    Significant casing deformation (CD) occurs during multi-stage fracturing of shale gas horizontal wells,which reduces the ratio of recovered reservoirs and increases operation costs. Based on a comprehensive review of global research on this issue,a comparative analysis of the current status of casing deformation in shale gas horizontal wells was conducted. With the casing deformation data from Changning-Weiyuan,Luzhou,and Weirong blocks,the distribution patterns of casing deformation in terms of time,space,and morphology were summarized. The influences of engineering factors such as casing and cement sheath types,cementing quality,fracturing and perforation parameters,and thermal stresses,as well as geological factors such as reservoir heterogeneity and reservoir slip,on casing deformation,were analyzed. The analysis results indicate that while engineering factors can increase casing stresses,they are unlikely to cause casing deformation. Among geological factors,reservoir slip induced by natural fractures and faults activated during multi-stage fracturing is the main controlling factor leading to significant casing deformation. To address this issue,various control methods were summarized,including optimizing casing and cement sheath parameters,improving cementing quality,selecting appropriate fracturing and perforation parameters,optimizing wellbore trajectory,and controlling reservoir slip. Additionally,it was proposed to enhance the understanding of formations and improve prediction accuracy of reservoir slip. The research findings provide references for casing integrity design and control during the fracturing process.

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    A Global Review of Technical Status and Development Trend of Drilling Fluids for Deep and Ultra-Deep Wells

    LIU Fengbao, SUN Jinsheng, WANG Jianhua
    Xinjiang Oil & Gas    2023, 19 (2): 34-39.   DOI: 10.12388/j.issn.1673-2677.2023.02.004
    Abstract331)      PDF (573KB)(123)       Save

    Drilling fluid is the core technology of deep and ultra-deep drilling and completion,and is one of the key technologies determining the success of a drilling operation. In this paper,the difficulties facing drilling fluids of deep and ultra-deep wells were analyzed,including wellbore instability,failure of drilling fluids at high-temperature and high-salinity conditions,high friction and environmental protection. Moreover,the latest technical progress of water- and oil-based drilling fluids in both China and other countries was reviewed. It was concluded that there are still large technical gaps in temperature and salinity resistance of drilling fluids between domestic drilling fluid systems and foreign advanced technologies,and therefore,it is urgent to strengthen research and development  efforts in terms of failure mechanisms of drilling fluid agents,anti-ultra-high-temperature drilling fluid agents and supporting technologies for special formations.

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    Experimental Research and Application of VHSD Dilatation Stimulation in Shallow Heavy Oil Reservoirs

    ZHANG Liwei
    Xinjiang Oil & Gas    2023, 19 (2): 69-74.   DOI: 10.12388/j.issn.1673-2677.2023.02.009
    Abstract120)      PDF (3036KB)(110)       Save

    In the late development stage of heavy oil reservoirs by steam injection huff and puff,the vertical well + horizontal well pattern steam drive (VHSD) is considered an effective way to sustain the recovery of mature heavy oil blocks. However,due to the interlayer distribution,low formation pressure coefficient,and the presence of steam channels in mature heavy oil blocks,the resultant oil gain of this method is unsatisfactory. The SAGD dilatation stimulation technology for heavy oil recovery can effectively break through the interlayers between injection well and production well and improve the overall production degree of the reservoir. Therefore,it is necessary to perform in-depth investigation of the dilatation technology for heavy oil reservoirs in the context of the VHSD. A one-dimensional core dilatation experiment was carried out,and the results showed no considerable post-dilatation variation of the core porosity and yet,an increase in the effective permeability by about 200 times. Based on large scale three-dimensional physical modeling,a dilatation experiment under the VHSD well pattern mode was carried out. The experiment shows that:(1) When the horizontal well trajectory is parallel to the direction of the maximum principal stress,the dilatation area is larger;(2) The distance of less than 35m between the vertical well and horizontal well is conducive to the formation of the combined dilatation zone;(3) After the high-permeability channels are plugged,an effective dilatation zone can still be formed. The experimental results are applied to the field practice,which shows that the recovered degree of the horizontal section of the production horizontal well is increased by more than 15% and the well production is effectively improved. This research provides effective references for the optimization of key parameters of the dilatation stimulation of heavy oil reservoirs,and is of great significance for the continuous efficient development of mature heavy oil blocks.


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    Progress and Application of the Key Technologies of Deep and Ultra-Deep Well Cementing

    YU Yongjin, XIA Xiujian, WANG Zhiguo, LIAO Fuguo, LIU Binhui, DING Zhiwei,
    Xinjiang Oil & Gas    2023, 19 (2): 24-33.   DOI: 10.12388/j.issn.1673-2677.2023.02.003
    Abstract335)      PDF (1607KB)(107)       Save

    Deep and ultra-deep reservoirs are strategic alternatives for increasing reserves and production of hydrocarbons. Recently,significant progress has been made in deep well cementing,especially for special cementing working fluid systems(such as high temperature-resistant cementing additives,cement slurry tolerant of high temperature and large temperature deferences and ultra-high temperature cement slurry),high temperature-resistant spacer,cementing tools,and cementing technology such as precise managed-pressure cementing,gradual wellhead pressure-holding and prestressed cementing. The cement slurry and cementing technology developed independently in China have been applied to deep well cementing operations in Sichuan,Tarim and Bohai Bay and other basins,and present remarkable performance in the successful cementing operations of Well Pengshen 6,the deepest vertical well in Asia,and Well Hongxing 1,the first well in China featuring 8-section-and-8-completion,and Well Qiantan1,the well with the highest temperature in Dagang Oilfield. Nowadays,the increasing complexity of targets of hydrocarbon exploration and development leads to a series of new challenges for cementing deep and ultra-deep wells. Consequently,it is necessary to strengthen the research on the basic theory,key materials,working fluid system,functional tools and technologies for cementing deep and ultra-deep wells,so as to provide more powerful technical support for deep and ultra-deep oil and gas exploration and development.

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    Optimization of Well Shut-in Time after Fracturing in Jimusar Shale Oil Reservoirs
    ZHANG Yanjun , XU Shucan , LIU Yafei , WANG Xiaoping , GE Hongkui , ZHOU Desheng
    Xinjiang Oil & Gas    2023, 19 (1): 1-7.   DOI: 10.12388/j.issn.1673-2677.2023.01.001
    Abstract373)      PDF (3496KB)(104)       Save

    Well shut-in after fracturing is of great importance for increasing the oil recovery and production of shale oil reservoirs. The key is to determine the shut-in time. At present,there is no systematic and effective method for determining the time of shut-in either in China or across the world. The pressure transmission of the fracture system,the ion diffusion of the produced fluid and the capillary force imbibition are the key problems to be solved for addressing the above challenges. With laboratory experiments and field analysis,a comprehensive determination method for the shut-in time for Jimsar shale oil reservoirs was developed by clarifying the microscopic pore characteristics,wettability,laminae,and imbibition flooding potential of Jimsar shale oil reservoirs and analyzing the existing methods used and characteristics of shut-in time determination. It is concluded that the Jimusar shale oil reservoir provides strong imbibition and diffusion ability,and well shut-in after fracturing contributes to the displacement of oil. The shut-in time can be determined comprehensively in accordance with the required equilibrium time of the wellhead pressure,imbibition,and production fluid salinity. To determine the post-fracturing shut-in time for Jimsar shale oil reservoirs,the synergy of micro-fracture fluid charging and matrix imbibition should be taken into consideration. Specifically,with the second turning point of wellhead pressure decline taken as the lower limit and the turning point for the stable rising of salinity as the upper limit,the optimal shut-in time is determined,considering the imbibition equilibrium. The shut-in time after fracturing for Well Q was optimized based on laboratory experiments and field data. The suggested shut-in time for Well Q is about 55 days. This study provides an important reference for optimizing the shut-in time after fracturing.

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    Research Progress on String Erosion During Massive Sand Fracturing

    ZHANG Sisong, ZENG Dezhi, PAN Yuting, TIAN Gang, YU Huiyong, SHI Shanzhi
    Xinjiang Oil & Gas    2022, 18 (3): 65-72.   DOI: 10.12388/j.issn.1673-2677.2022.03.011
    Abstract88)      PDF (2870KB)(98)       Save
    Massive sand fracturing is a necessary means for the development of unconventional oil and gas resources, as well as an important cause for the failure of downhole pipe strings and tools due to erosion wear. Targeted at this problemthe erosion theories and main research conclusions proposed by foreign scholars based on different materials are reviewed comprehensivelyand the derivative researches into basic erosion theories conducted in China are summarized. Combined with the actual technological conditionsthe main causes of serious erosion of pipe string in the process of sand fracturing are expounded. With respect to the pipe string structures and fracturing tools that are likely to be eroded in the process of massive sand fracturingthe research progress is introduced. Current research difficulties and future research direction of fracturing string erosion are pointed outwhich is of important reference value and engineering significance for protecting the fracturing string against erosion and the wellbore integrityand improving the development effect of unconventional oil and gas resources.
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    The Lost Circulation Mechanism in Formations Prone to Lost Circulation at Misui Block in Changqing Oilfield

    PENG Lei, LUO Jiangwei, ZHAO Hongbo, LE Lu, BIAN Jing, DONG Jingnan
    Xinjiang Oil & Gas    2023, 19 (4): 10-19.   DOI: 10.12388/j.issn.1673-2677.2023.04.002
    Abstract124)      PDF (8824KB)(98)       Save

    Rich in natural gas resources,Misui Block is a key strategic area for accelerating the production of Changqing Oilfield. However,the frequent occurrence of lost circulation in recent years has seriously restricted improvement of cost-efficiency. Therefore,to curb the occurrence of well lost circulation,the lost circulation mechanism in this area has been studied through multi-scale quantitative experiment on rock physical property,microelectrode imaging logging observation and geo-mechanical profile analysis of wells. The results show that the thief zones in Misui Block are mainly in Liujiagou and Shiqianfeng Formations,which have large numbers of micro- and nano-scale fractures. The average calculated dynamic Yang's modulus of the cores from these formations are 17.94 GPa and 8.47 GPa,respectively,and the average dynamic Poisson's ratios are 0.394 and 0.064,respectively. The clay mineral content of Liujiagou Formation is more than 50%,and the brittle mineral content of Shiqianfeng Formation is as high as 72%. The imaging logging map shows that the area contains tensile fractures. The single well geo-mechanical profile reveals a low-pressure area in the thief zone,where the density of drilling fluid is 1.18 g/cm3. Finally,analysis shows that the high contents of clay and brittle minerals in the formation caused both hydration fractures and structural fractures,with low formation pressure causing drilling fluid to flow into natural fractures,eventually resulting in lost circulation. The research results not only reveal the lost circulation mechanism at Misui Block,but also provide technical guidance for selecting plugging methods and reducing well lost circulations at Misui Block.

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    Study on the Law of Wellbore Alkali-Salt Deposition in Fengcheng Formation  of Mahu Sag#br#
    WU Dingying , PU Di, , ZHENG Miao , YIN Jianyu , LUO Pingya , GUO Yongjun,
    Xinjiang Oil & Gas    2023, 19 (3): 42-48.   DOI: 10.12388/j.issn.1673-2677.2023.03.007
    Abstract89)      PDF (1744KB)(93)       Save

    The post-frac flowback and production of the alkali-salt layers of Fengcheng Formation in Mahu Sag suffer from wellbore salt deposition,but the salt deposition law remains unclear. Therefore,through static and dynamic salt precipitation evaluation experiments,the reservoir conditions affecting the salt precipitation rate and the impacts of flow rate and gas production on wellbore salt deposition in the production process are investigated to clarify the wellbore salt deposition law. The results show that the three typical salts,with their solubility from most to least sensitive to temperature,are sodium carbonate,sodium bicarbonate and sodium chloride. Moreover,the boundary conditions (total salinity and ion composition) and salt crystal types of salt crystal precipitation are defined for composite salt solutions with different compositions. Under the same salinity,the precipitation degrees of composite salts with different compositions are between those of the individual salt,and the priority orders of salt precipitation are sodium bicarbonate,sodium carbonate and sodium chloride,which is consistent with the change of solubility of various salts with temperature. With the increasing flow rate and gas production,the salt deposition first grows and then declines. The salt deposition peaks in the case of the daily liquid production of 40 m3/L and the gas-liquid ratio of 200 m3/L.The study on the salt deposition law in alkali-salt wells helps to set reasonable drainage parameters,delay the salt deposition during flowback,ensure the smooth completion of formation testing after fracturing,and provide a theoretical basis for on-site salt prevention measures in the later production from Fengcheng Formation alkali-salt layers.

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    Xinjiang Oil & Gas    2023, 19 (3): 0-.  
    Abstract91)      PDF (13819KB)(91)       Save
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    Research Progress and Application of Chemical Plugging Materials and Method for Carbon Dioxide Flooding

    ZHU Daoyi, SHI Chenyang, ZHAO Yanlong, CHEN Shengen, ZENG Meiting
    Xinjiang Oil & Gas    2023, 19 (1): 65-72.   DOI: 10.12388/j.issn.1673-2677.2023.01.010
    Abstract206)      PDF (1379KB)(88)       Save

    Carbon Capture,Utilization and Storage (CCUS) technology is an important tool for the energy sector to enable efficient oil and gas production under the dual-carbon goal. Injecting CO2 into oil reservoirs can significantly enhance oil recovery. However,its mobility differs greatly from that of the crude oil,and there’s clear differentiation with oil and water,which results in a limited sweep efficiency of CO2. Therefore,it is urgent to develop efficient CO2 plugging materials and corresponding plugging control technologies to improve reservoir recovery and CO2 storage efficiency. This article explains the characteristics of plugging in the CO2 flooding process and gives an overview of the commonly used CO2 plugging materials and methods. It also describes their applications in oil fields across the world,and their potential for improving CO2 recovery and storage in Xinjiang Oilfield. This study is inspiring for the global research and development of plugging materials in the process of CO2 flooding in oilfields worldwide,and highlights the future direction of CO2 plugging technology in Xinjiang oilfields.

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    Practice and Understanding of Volume Fracturing Technology for Horizontal Wells in Jimsar Shale Oil Reservoir

    XU Jiangwen, WANG Mingxing, WANG Junchao, SUN Haoran, WANG Liang
    Xinjiang Oil & Gas    2024, 20 (3): 23-30.   DOI: 10.12388/j.issn.1673-2677.2024.03.003
    Abstract119)      PDF (790KB)(86)       Save

    Addressing Jimsar shale oil reservoir,this study aims to enhance fracture-controlled reserves by conducting theoretical research and technical practices. Focused on four key aspects—fracture network design,construction,proppant effectiveness,and the enhancement of in-situ oil mobility,three generations of technological advancements have been realized. Fundamental theories regarding the effective propagation of hydraulic fracture in thin interlayers and key technologies such as multi-cluster fracturing within a stage and the use of cost-effective materials have been mastered. An integrated horizontal well volume fracturing technology system centered on fracture-matrix matching,precise stimulation,multi-scale proppant support,and CO2 prepad injection has been developed. The key technical indicators of fracturing have reached the advanced domestic level,supporting the large-scale and efficient development of Jimsar shale oil. In 2023,the oil production of Jimsar shale oil surpassed 60×104 t,with a consecutive annual production increase of 10×104 t in the block for three years. This achievement has provided robust technical support for the establishment of China's first national continental shale oil demonstration zone by 2025 and serves as a reference for optimizing shale oil development technologies in other regions of China.

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    Fracture Propagation Law of Hydraulic Fracturing in High-Salinity Reservoir of Fengcheng Formation in Mahu #br#

    PAN Liyan, HAO Lihua, LIU Kaixin, SUN Xize, ZHU Zhenlong, ZHAO Yanxin,
    Xinjiang Oil & Gas    2023, 19 (4): 20-28.   DOI: 10.12388/j.issn.1673-2677.2023.04.003
    Abstract95)      PDF (2886KB)(83)       Save

    The high salt content of Fengcheng Formation in Mahu leads to high operating pressures, difficulty in fracture propagation when penetrating salt layers, and increased difficulty in adding proppant. True triaxial fracturing experiments are carried out on equivalent salt-bearing rock samples prepared according to similarity criteria, and fracture propagation in salt-bearing reservoirs is numerically simulated using the finite element and cohesive element methods. The influence of salt content, viscosity, pump rate, and other factors on fracture propagation is explored. The results show that the fracture opening pressure of salt-bearing reservoirs is greater than that of conventional sandstone reservoirs, and their plasticity is stronger. The existence of pure salt interlayers hinders the longitudinal propagation of fractures. The lower the fluid viscosity , the stronger the dissolution of the salt-bearing reservoir and the lower the operating pressure. The higher the pump rate, the higher the fracturing friction and the operating pressure. In field, high viscosity fluid (120 mPa·s) with clean water and high pump rate (5 m3/min per single cluster) have been adopted to achieve effective penetration into pure salt barriers and form wider fractures. These results have important guiding significance for the stimulation of salt-bearing reservoirs in Mahu area.

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    Xinjiang Oil & Gas    2022, 18 (4): 0-0.  
    Abstract115)      PDF (4475KB)(83)       Save
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    Advances in Study on Rheology Modifier for Water-Based Drilling Fluids
    SUN Jinsheng, , YANG Jie, , RONG Kesheng , WANG Ren, , QU Yuanzhi, , LIU Fan,
    Xinjiang Oil & Gas    2023, 19 (2): 1-16.   DOI: 10.12388/j.issn.1673-2677.2023.02.001
    Abstract134)      PDF (7116KB)(82)       Save

    The global oil and gas exploration is gradually moving from shallow layer to deep layer,conventional hydrocarbon resources to unconventional hydrocarbon resources,medium and high-permeability to low-permeability and low-grade,and shallow seas to deep seas. With the increasing drilling workload,fit-for-purpose drilling fluid technology is needed to provide support for high-performance drilling. High-performance drilling fluids are the key to safe,efficient,economical,and green drilling,and the drilling fluid rheology is the core parameter for evaluating the performance of the drilling fluid system. As an essential treatment agent for building the drilling fluid systems,rheology modifiers can enhance viscosity and shear,improve the yield point-plastic viscosity ratio and optimize shear thinning,so as to control the rheology of drilling fluids. In order to drive the research and development of new rheology modifiers for drilling fluids,this paper investigates and classifies the rheology modifiers for water-based drilling fluids at home and abroad,and summarizes the research results,application,and existing problems of various rheology modifiers. The future direction of rheology modifiers for water-based drilling fluid was also analyzed to facilitate the technical improvement of water-based drilling fluids.

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    Current Status and Suggestions for Drilling Technology of CNPC Continental Shale Oil Reservoirs

    Xinjiang Oil & Gas    2024, 20 (3): 1-14.   DOI: 10.12388/j.issn.1673-2677.2024.03.001
    Abstract191)      PDF (2045KB)(79)       Save

    Shale oil with medium to high maturity is the key field for China's shale oil strategic breakthrough,and strengthening the exploration and development of continental shale oil is an important way to ensure the security of national energy supply. The technical progress of shale oil drilling in Ordos,Junggar and Songliao Basins by China National Petroleum Corporation (CNPC) was introduced in detail,including large platform factory-like well placement,horizontal well casing program optimization,"one-run drilling" in separate well sections,high-performance drilling fluids for horizontal wells,integrated geological steering and other key technologies. By benchmarking against advanced shale oil drilling technologies in North America,the gap and development trend of shale oil drilling in China were analyzed in terms of well placement and wellbore configuration,geological-engineering integration and steering technology,supporting technology for accelerating rates of penetration (ROP),drilling fluid and cementing supporting technology. Development suggestions,such as continuously promoting large platform factory-like operations,optimizing wellbore configurations,integrating ROP acceleration technologies,strengthening research on geological-engineering integration,and accelerating the research and development of new-generation steering tools,were proposed in order to achieve the goals of ROP acceleration,cost reduction,and efficiency improvement in continental shale oil drilling,and moreover,the engineering goals of the shale oil revolution.

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    ZHANG Jingchun, , REN Hongda , YU Tianxi , YIN Jianyu , ZHOU Jian , ZHOU Hongtao
    Xinjiang Oil & Gas    2023, 19 (1): 27-34.   DOI: 10.12388/j.issn.1673-2677.2023.01.005
    Abstract138)      PDF (547KB)(76)       Save

    Proppant is the key material for propping hydraulic fracturing,and its performance has a significant impact on the effect of fracturing stimulation,so the research on fracturing proppants has received extensive attention. This paper summarizes the research and application of fracturing proppants and related technologies,including conventional proppants such as quartz sand,ceramic proppant,and coated proppant,as well as new types of proppant and related technologies such as self-suspension proppant,gas-suspension proppant,and in-situ generated proppant reported in recent years,totaling 10 categories. Last but not least,the paper looks into the future development directions of proppants and related technologies to provide reference for researchers of proppants and further accelerate the development of proppant technology.

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    Numerical Simulation of the Pressure Law of Energy Charging and Permeability Enhancement in Low Permeability Reservoirs

    ZHU Zheng, DANG Hailong, CUI Pengxing, DANG Kaiyan, BAI Pu, ZHAO Yining
    Xinjiang Oil & Gas    2023, 19 (4): 56-62.   DOI: 10.12388/j.issn.1673-2677.2023.04.007
    Abstract103)      PDF (6406KB)(75)       Save

    A number of problems have been experienced with water injection in Yanchang Oilfield,such as high-pressure injection failure,poor flooding effect,and rapid increase of water cut during injection. An innovative method for energy charging and permeability enhancement is proposed to address these issues. Numerical reservoir simulation is used to study the evolution of fractures,matrix pressure,and bottom hole pressure propagation during injection and well shut in. The influence of injection volume on fracturing effect is also analyzed. It is found that,during the injection stage,rapid injection of fluid increases the pressure in the fracture,with the injected fluid passing through the main fracture to the tips of the fractures. The pressure increase mainly occurs around the fracture itself,with little change in the matrix pressure. In shut in stage,as shut in time increases,the matrix pressure in the fracture and near-fracture zone initially decreases rapidly and then tends to become stable after a certain time. If the distance from the fracture is more than 30 m,the matrix pressure first increases and then decreases with the increase of shut in time. The bottom hole pressure also declines rapidly in the early stage of shut in with the rate of decline slowing in the later stage. The greater the injection volume,the higher the formation energy. Analysis of the effect of energy charging and permeability enhancement in field applications for low permeability reservoirs shows remarkable increases in pressure and oil production. This provides a valuable reference for the development of energy charging and permeability enhancement in similar reservoirs.

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    Analysis of the Effects for Reamer Size under Different Operation Conditions:a Case Study of Well H101 in the Southern Margin of Junggar Basin

    GAN Quan, ZHANG Maolin, ZHANG Chen, WEI Qiang, LI Bingqing, ZHANG Dong
    Xinjiang Oil & Gas    2023, 19 (3): 10-20.   DOI: 10.12388/j.issn.1673-2677.2023.03.002
    Abstract114)      PDF (5579KB)(74)       Save

    The determination of the reamer size(the desirable reamed borehole size) is a global challenge for research on reaming in drilling. To ensure smooth drilling and cementing of reamed borehole sections,an in-depth case study of Well H101 drilled in the southern margin of Junggar Basin was performed to identify the affecting patterns of the reamed borehole size on drilling,tripping and cementing operations. The requirements for the reamer size were analyzed from perspectives of the drilling tool bending deformation,pump rate optimization,BHA vibration,swab and surge pressure during tripping and fluid density window,surge pressure of running liners,equivalent circulating density(ECD) during cementing,and wellbore integrity incorporating wellbore curvature,and the impacts of changes in casing sizes on cementing of the reamed borehole section were investigated. Finally,the above analyses were combined with a mathematical statistical approach to comprehensively determine the reamer size. The determined reamer size was applied to Well H101 and analogous wells in the southern margin of Junggar Basin,which were all found with smooth drilling operations after reaming,and moreover,Well H101 delivered a daily penetration of 101 m for the reamed borehole section. The presented method and strategy for the reamer size optimization incorporate more factors and are more reliable. They provide important references for determining the reamer size of to-be-reamed wells. 

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    Design Optimization of Downhole Throttling for Gas Wells in Xinjiang Oilfield and Its Application 
    DU Junjun , CHI Ming , Xieraili·MAIMAITI , WANG Gang , WANG Wenwen , LIANG Haibo
    Xinjiang Oil & Gas    2022, 18 (4): 84-88.   DOI: 10.12388/j.issn.1673-2677.2022.04.015
    Abstract201)      PDF (751KB)(72)       Save
    In order to meet the requirements of gathering and transportation pressure,and prevent wellhead hydrate freeze bloking,design optimization has been made for the downhole throttling process of high-pressure and medium/low-pressure gathering and transportation regarding well selection conditions,gas nozzle diameter,setting depth,and other key technical parameters based on the technological principle of downhole throttling,and wellbore temperature and pressure profiles have been simulated. The results show that the downhole throttling process can meet the pressure requirements of high-pressure and medium/low-pressure gathering and transportation,and effectively solve the problem of wellhead hydrate freeze bloking. 
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    A Machine Learning-Based Bridging Particle Size Recommendation Method for Lost Circulation Control

    LIU Fan, LIU Yushuang, ZHANG Zhen, LI Yongjian, LIU Ce, MA Zhihu,
    Xinjiang Oil & Gas    2024, 20 (1): 13-20.   DOI: 10.12388/j.issn.1673-2677.2024.01.002
    Abstract93)      PDF (3565KB)(68)       Save

    Lost circulation is a key technical challenge in oil and gas exploration,and bridge plugging is the most commonly used method for lost circulation control. As an important parameter,the size of bridging particles directly affects the plugging. At present,the size selection mainly relies on experience,lacking a scientific and effective method. In light of this,this paper investigates a particle size recommendation method for lost circulation control based on machine learning algorithms. The basic data used for this method are well-logging,mud logging,and lost circulation control data from 126 completed wells in Kuqa piedmont area of Tarim Basin. The input layer adopts 23 main parameters screened based on the Pearson algorithm,and the output layer is in 4 bridging particle size ranges of 0-750 μm,750-1 500 μm,1 500-4 000 μm and>4 000 μm. 10 commonly used machine learning algorithms are trained and tested to determine the accuracy of three types of datasets:well logging data,mud logging data,and combination of the former two types. It is found that the scores of each algorithm for the well logging + mud logging dataset are generally higher than those for the well logging and mud logging datasets. For the combined dataset,the support vector machine and extremely randomized trees algorithms have the highest F1 scores of above 0.9. The bridging particle size recommendation model based on the support vector machine and extremely randomized trees algorithms is validated twice on a well in Kuqa piedmont area. The predicted results of bridging particle size of the two algorithm models are consistent with the actual bridging effect in the field. This method exhibits good application prospects in the scientific optimization of bridging particle size.

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    Non-Uniform Perforation to Balance Multi-Cluster Fractures Propagation and Parameter Optimization
    SHENG Mao , DENG Chao , LI Jie , GU Mingzhe , WANG Tianyu , TIAN Shouceng,
    Xinjiang Oil & Gas    2024, 20 (3): 54-63.   DOI: 10.12388/j.issn.1673-2677.2024.03.007
    Abstract109)      PDF (5659KB)(68)       Save

    Multi-cluster perforation staged fracturing of horizontal well has become one of the key technologies for completion and stimulation in unconventional oil and gas reservoirs. However,the fractures of the central perforation clusters in each fracturing stage are significant affected by stress interference from the fractures of heel and toe clusters,leading to substantial propagation resistance of the central cluster fractures. This is a major cause of the unbalanced propagation of multi-cluster fractures. This study optimized the design of non-uniform perforation distribution pattern between clusters to regulate the perforation parameters,balance the fluid distribution among clusters,mitigate the stress interference between fractures,and promote the balanced propagation of fractures. Therefore,a multi-stage,multi-cluster fracture propagation model that accounts for stress superposition between stages/clusters was established. The model was used to compare and analyze the fracture propagation patterns and mechanisms of spindle-shaped,sloped and uniform perforating patterns. The difference in fracture length and height propagation morphology was utilized to assess the equilibrium of fracture propagation. The perforation distribution pattern was optimized,and an orthogonal test was designed to refine the parameters of non-uniform perforation distribution pattern. The findings indicate that under typical shale oil reservoir conditions,the spindle-shaped perforation pattern achieves the best fracture propagation equilibrium,followed by uniform pattern and then the sloped pattern. The mechanism is that,with the spindle-shaped perforation pattern,the clusters at both ends have a perforation friction 1.4~16.7 times greater than that of the central clusters,reducing the stress interference from the heel and toe fractures on the central-cluster fractures. This results in an increased fluid inflow distribution in the central clusters,enhancing the fracture propagation equilibrium by 17.2 % compared to the uniform pattern. Conversely,the sloped perforation pattern,with over 35% of the holes concentrated at the toe cluster and accounting for 49.3 % of the fluid inflow,exerts a significant squeezing effect on the central cluster fractures,which is counterproductive to achieving a balanced fracture propagation. The optimization of the spindle-shaped perforation parameters reveals that an fracture propagation equilibrium is achieved with a total of 49 holes,a perforation diameter of 10 mm,and an end-cluster perforation proportion of 24.5%. The research results are expected to offer an effective approach for the design of non-uniform perforation in multi-cluster fracturing for unconventional oil and gas reservoirs. 

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    Study on Penetration Depth and Rock Breaking Mechanism of PDC Cutter in Different Percussion Drilling Methods

    LIU Wei, XI Yan, ZHA Chunqing, GUO Qingfeng, XU Zhaohui, Wang Wei
    Xinjiang Oil & Gas    2023, 19 (2): 17-23.   DOI: 10.12388/j.issn.1673-2677.2023.02.002
    Abstract120)      PDF (5746KB)(65)       Save

    Based on actual engineering applications of conventional drilling and percussion drilling,and considering the material parameters and intrinsic model of rock dynamic mechanics,a numerical model of rock breaking of the cutters of Polycrystalline Diamond Composite(PDC) bit was established. The penetration depth,damage area,size of rock debris particles and rock breaking volume of PDC cutters under different percussive drilling models were compared and analyzed. The results show that the rock cutting pattern is very similar between the numerical simulation results and the laboratory physical experimental model of single-cutter. The penetration depth of single tooth of rotary,torsional,and combined percussive drilling increased by 19.8%,6.6% and 26.9% respectively compared with that of conventional drilling,and the combined percussive drilling saw the most significant increase in rate of penetration. When there is axial impact load during percussive drilling(such as combined percussive drilling or rotary percussive drilling),it will cause visible damage to the rocks below the cutting surface,which facilitates the “second cutting” after the drilling cutters turn 360 °,but large rock debris particles can be produced,so it is necessary to optimize the drilling fluid parameters to keep the wellbore clean. The fluctuation range of penetration depth of the cutter in torsional percussive drilling is small,which indicates that this method helps reduce the risk of bit stick-slip,and the rock debris particles produced are small which makes it easy to keep the wellbore clean. The research results are of great significance for the selection of different types of percussion drilling tools and tool parameters optimization. 

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    Xinjiang Oil & Gas    2023, 19 (2): 0-.  
    Abstract74)      PDF (12789KB)(65)    PDF(mobile) (12789KB)(39)    Save
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    Optimization and Application of Strength Criterion for Wellbore Mechanical Instability Evaluation in Drilling

    YANG Hu, CHEN Hao, LI Yilin, SUN Weiguo, ZHOU Penggao
    Xinjiang Oil & Gas    2022, 18 (3): 1-5.   DOI: 10.12388/j.issn.1673-2677.2022.03.001
    Abstract158)      PDF (855KB)(64)       Save
    There is a lack of theoretical guidance and practical optimization method for the selection of strength criteria in wellbore stability evaluation in field, which may lead to the deviation of the drilling fluid density used. The collapse pressure calculated by six strength criteria widely used in rock engineering had been compared. The results show that the collapse pressure calculated by D-Pi criterion is the highest followed by M-C criterion H-B criterion and D-Pc criterion the collapse pressure calculated by LAm criterion and W-Cm criterion is in the middle. Through field practice a set of method for strength criteria optimization and application has been summarized. Applying the optimized strength criterion to the wellbore stability evaluation in later drilling to optimize the design and use of drilling fluid density can not only ensure the wellbore stability but also improve the drilling speed and oil and gas discovery. This method has been applied in some blocks and strata of Junggar Basin and achieved good results which is proved to be of popularization and application value.
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    Development Status of Wellbore Integrity Inspection Technology for Deep Strata and Deep Wells
    SONG Xuefeng , LI Zhibin, , LIU Jinming , WANG Jiangshuai , DING Yida , QIAN Xuesen
    Xinjiang Oil & Gas    2024, 20 (4): 8-18.   DOI: 10.12388/j.issn.1673-2677.2024.04.002
    Abstract128)      PDF (2630KB)(64)       Save

    As the development of oil and gas resources is continuously advancing toward deep water areas,deep and ultra-deep strata,complex geology and extreme wellbore conditions pose great challenges to the safe and stable production of oil and gas wells. Conventional wireline logging technology and casing packer leak detection technology can meet the technical requirements of wellbore integrity inspection,but they both require to shutdown wells and the costs of joint inspection are high. In recent years,the application of fiber optic sensing in petroleum industry has become increasingly widespread,opening up new ideas for real-time monitoring of wellbore integrity. By systematically summarizing the current development status of wellbore integrity inspection,the following prospects are made:(1) Permanently or semi-permanently placing optical cables in oil wells enables monitoring the temperature field,pressure field,stress field,sound waves,vibration,and fluids inside the wellbore in real time to provide direct data for evaluating the integrity status of oil and gas wells.(2) Fiber optic sensing technologies such as DTS and DAS are characterized by continuous,real-time and distributed measurement,for which it is preferred to place them during the well construction to deliver full lifecycle monitoring of oil and gas wells. However,the overall cost of fiber optic laying is relatively high,and the fiber optic layout method needs to consider the impact of pipe string insertion and cementing perforation operations. The fiber optic winding method and light source scattering type also have an impact on optical signal transmission and signal-to-noise ratio. Corresponding measures need to be taken to optimize the signal-to-noise ratio,improve the measurement accuracy and stability of the sensor.(3) Processing of fiber optic signals mostly relies on empirical methods determining the signal range in accordance with laboratory simulation experiments. However,considerable differences exist between the laboratory environment and the downhole environment. Therefore,it is still necessary to conduct wellbore experiments and establish measurement interpretation models based on the actual wellbore environment.

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    Application of Air-Foam Drilling in Well Chaitan1
    SUN Lanjiang , ZHANG Shuxia , LI Baoqing , XING Chao , LIU Wan , ZHONG Ninglong
    Xinjiang Oil & Gas    2022, 18 (4): 1-6.   DOI: 10.12388/j.issn.1673-2677.2022.04.001
    Abstract219)      PDF (699KB)(63)       Save
    In many areas of Qaidam Basin,such as Yingxiongling,Ganchaigou and Xiandong,the shallow strata have poor lithology, loose cementation,fracture development,and frequently-occurred loss-return leakage in the process of drilling,which have seriously restricted the speed of drilling and affected the safety of drilling. This is a regional problem that needs to be solved urgently. Well Chaitan1 is a risk exploratory well located in Xiandong area. Conventional drilling fluid was used for the drilling of the surface section hole with a diameter of 660.4 mm. Leakage during the drilling was huge,and the plugging effect was not satisfactory. Therefore,it no longer possessed conditions to continue with the drilling. By using air-foam drilling technique and selecting the most suitable foaming agent and inhibitor for this well,the problem of frequently-occurred loss-return leakage in shallow strata has been solved,and the drilling cycle has been greatly shortened. By using the technique of sand cleaning-casing running,safe casing running has been realized in the well section with instable borehole and irregular hole diameters. The successful application of air-foam drilling technique in the Φ660.4 mm hole of Well Chaitan1 provides an approach and technical reserve for solving the problems of low pressure and likelihood for leakage and collapse in shallow strata during drilling in Qaidam Basin.
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    Study on Main Controlling Factors of Water Production in Tight Gas Wells 
    LI JingSong, LIU Zixiong, KOU Shuangyan, ZHANG Xiuming, LIU Rumin, WANG Jinwei
    Xinjiang Oil & Gas    2022, 18 (4): 20-25.   DOI: 10.12388/j.issn.1673-2677.2022.04.004
    Abstract113)      PDF (513KB)(63)       Save
    It is well known that water production is the main factor leading to low production and low efficiency of gas wells. However, due to the lack of understanding of the main controlling factors of water production,applying the conventional drainage gas production method is always of low efficiency. In order to comprehensively study the main controlling factors of water production,the cocoon stripping optimization algorithm by big data analysis is introduced to firstly establish a big data sample library for factors that may affect water production,including geological,engineering,drainage and production factors;secondly,all the data is cleaned to eliminate invalid data. After that,the single factor analysis is carried out to determine the positive and negative relationship of each factor;then,multifactor analysis is conducted to find out the main controlling factors affecting water production in tight gas wells. Finally,39 main controlling factors are found out by using elimination method and the main control equation of water production is established to define the effect of each factor on water production. The study shows that:the main factors that greatly affect water production are producible porosity and total porosity identified by logging,gas testing and production casing pressure,clay content,etc. In order to avoid the impact of water production on gas production in the later stage,the reservoir sections with larger producible porosity,larger total porosity and lower clay content are preferred for fracturing. Meanwhile,the production scheme shall be implemented in the production process to avoid excessive pressure difference which can aggravate formation water production,so as to provide a basis for taking effective treatment measures for water-producing gas well in the later stage. 
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    Key Technologies and Practice of Shale Oil Cost-Effective Development in Jimsar Sag,Junggar Basin

    QI Hongyan, WU Chengmei, HU Ke, CHEN Yiwei, XU Tianlu, WANG Yongjiao
    Xinjiang Oil & Gas    2024, 20 (3): 15-22.   DOI: 10.12388/j.issn.1673-2677.2024.03.002
    Abstract97)      PDF (2526KB)(61)       Save

    Xinjiang Jimsar Shale Oil Demonstration Area is the first national-level continental shale oil demonstration project,located in Jimsar Sag,Junggar Basin,China. The target layer is Permian Lucaogou Formation. After ten years of exploration and development,with the obtained abundant production and geological data of the reservoir and deepened geological understanding,the corresponding exploration and development technologies become fairly mature. The fine 3D seismic survey with broadband excitation and well-surface integrated acquisition improves the geological understanding. The fine characterization and classification evaluation techniques of shale oil sweet spots provide a basis for development deployment. The comprehensive mud logging technology of "gold targets" improves the target-layer drilling ratio that is fundamental for delivering high stable production from horizontal wells. The customized fracturing technology of "complex fracture networks" provides an effective means for the efficient development of shale oil. The production capacity of horizontal wells is fully exploited by the flowback and production scheme optimization technique. The marketization has greatly reduced costs and improved both quality and efficiency. The cost-effective development technology system of Jimsar shale oil provides references for the efficient exploration and development of shale oil in China.

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    Multi-Field Coupling Analysis of Wellbore Instability in Hutubi Anticline While Using Water-Based Drilling Fluid

    SONG Xianzhi, GUO Yong, XIANG Dongmei, JU Pengfei, TAN Qiang, LIU Wei
    Xinjiang Oil & Gas    2023, 19 (4): 1-9.   DOI: 10.12388/j.issn.1673-2677.2023.04.001
    Abstract107)      PDF (3894KB)(60)       Save

    Complex problems,such as HTHP,wellbore collapse,and lost circulation were encountered during drilling Hutubi Anticline. The fabric,mechanical properties,and in-situ stress state of the troublesome medium-deep shale formation were analyzed to determine the countermeasures necessary to stabilize the borehole and reduce risk. A multi-field calculation model for collapse pressure was established linking mechanical factors,drilling fluid chemistry,and fluid seepage. The mechanism of wellbore instability when using water-based drilling fluid in the middle-deep shale formation of Hutubi anticline was identified. The results indicate that the montmorillonite content of the illite-smectite mixed layers in the mudstone in Paleogene Anjihaihe-Ziniquanzi Formation (which collapses readily) exceeds 35%. The formation exhibits moderate expansion and high dispersion,with water expansion rate and recovery rate both being less than 10%. The formation strength also shows anisotropic properties. The mudstone in Cretaceous Hutubihe-Qingshuihe Formation shows reduced swelling and increased hardness and brittleness. Hutubi Anticline is subject to significant tectonic stress,with the maximum horizontal principal stress being equivalent to nearly 2.50 g/cm3,which is higher than the overburden pressure. Applying the multi-field coupling model indicates that the main causes of wellbore instability are seepage of drilling fluid along cracks,hydration of mudstone after contact with drilling fluid,and insufficient effective mechanical support of drilling fluid for the wellbore. The collapse pressure calculated using the multi-field coupling model is 0.05-0.25 g/cm3 higher than when only considering mechanical factors. It was established that the wellbore can be kept stable by maintaining the sealing ability of the drilling fluid to the fractured formation,preventing contact with easily hydrated mudstone during drilling,and increasing the density of the drilling fluid to slightly higher than the collapse pressure.

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    Xinjiang Oil & Gas    2023, 19 (1): 0-0.  
    Abstract132)      PDF (12767KB)(58)       Save
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    Micro-Scale Oil and Water Migration Characteristics of Water-Injection Huff and Puff in Ultra-Low Permeability Reservoirs

    CUI Pengxing, HOU Binchi, MENG Xuangang, DANG Hailong, WANG Chenchen
    Xinjiang Oil & Gas    2023, 19 (1): 8-15.   DOI: 10.12388/j.issn.1673-2677.2023.01.002
    Abstract108)      PDF (2043KB)(55)       Save

    Water injection huff and puff has become one of the key technologies for developing ultra-low permeability reservoirs in China. To understand the characteristics of oil and water migration in the process of water-injection huff and puff in ultra-low permeability reservoirs,the influence of time and pressure on the huff and puff effect was tested using the natural core of Chang6 reservoir in Nanniwan and the simulated sand pack tube model,and the affected range and micro fluid migration characteristics of dynamic imbibition of water-injection huff and puff was investigated. The analysis found that the effect of the first and the third cycles of huff and puff got better with increase of the time of shut-in,but the effect of the second cycle of huff and puff got worse,while the increase of shut-in pressure led to enhanced huff and puff effect. The range of dynamic imbibition positively correlates with the imbibition time. The difference of oil saturation changes gradually decreases with the increase of imbibition distance. Permeability and pore size affect the sweep of water in the process of huff and puff and the second migration of crude oil in large and small pore channels,therefore,it is necessary to expand the sweep range of injected water as much as possible in the development practices. At the same time,it is also important to pay attention to the secondary migration of oil and water in the pores with different sizes.

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    Analysis of Factors Affecting the Productivity of Radial Multilateral Horizontal Wells in Low Permeability Reservoirs

    SUN Xize, YU Tianxi, Anivar·SHAYIMU, ZHENG Weijie, DING Kebao
    Xinjiang Oil & Gas    2023, 19 (3): 49-56.   DOI: 10.12388/j.issn.1673-2677.2023.03.008
    Abstract88)      PDF (3945KB)(55)       Save

    Radial multilateral horizontal well technology can be used to improve the productivity of low permeability reservoirs by drilling multilateral branches in the oil intervals of horizontal wellbores,which increases the oil displacement area. However,the factors affecting the productivity of radial multilateral horizontal wells are not clear and,to date,there has been little research on methods of prediction. This paper describes a numerical model for radial multilateral horizontal wells,using numerical simulation software COMSOL,and its application in evaluating the influence of factors such as reservoir and well type on well production. The mathematical model was solved using the finite element method and radial horizontal well output predicted using the material balance method. The focus of the study is to analyze the effects of changes in radial multilateral well parameters and formation heterogeneity on production behavior and transient pressure distribution. The results show that branch length has a significant effect on productivity,effectively expanding the control area. The number of branches,their angles,and formation heterogeneity,are found to be the principal controlling factors.

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    Development of Viscosity Reducer for High Density Water-Based Drilling Fluid and Its Application#br#
    DENG Zhengqiang , OU Meng , BAI Hailong , JING Yujuan , HUANG Ping , SHAO Ping
    Xinjiang Oil & Gas    2023, 19 (3): 33-37.   DOI: 10.12388/j.issn.1673-2677.2023.03.005
    Abstract177)      PDF (548KB)(55)       Save

    One of the main reasons for rheology out-of-control of high density water-based drilling fluid is the increase of inferior solid phase content. Inferior solid phase is dispersed in high density water-based drilling fluid,which enhances the system architecture,resulting in increased drilling fluid viscosity and higher shearing force. Based on the principle of viscosity reduction by competitive adsorption,WNTHIN,a low molecular weight polymer viscosity reducer was synthesized with 2-acrylamide-2-methylpropanesulfonic acid,styrene,maleic anhydride,N and N-dimethylacrylamide in a molar ratio of 1∶2∶1∶1.Test results of the viscosity reducer show that WNTHIN can significantly reduce the viscosity and shearing force of high density potassium polysulfonate water-based drilling fluid with a density of 2.40 g/cm3,with plastic viscosity reduced by 42.85%,static shearing force reduced by 51.35%,and the recommended WNTHIN dosage addition is 1.5%. The field application of WNTHIN in a well in Penglai Gas Field showed improved rheology of high density potassium polysulfonate water-based drilling fluid. The plastic viscosity dropped from 58 mPa·s to 30 mPa·s,the yield point dropped from 29 Pa to 14 Pa,and the 10 min static shearing force dropped from 28 Pa to 16 Pa. The performance of the high density water-based drilling fluid has been improved to meet the technical requirements for safe drilling in deep wells. 

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    Settling Plugging Technology for Severe Lost Circulation at the Salt Bottom of Tarim Piedmont Zone

    LIU Fengbao, YIN Da, WEI Tianxing, WU Hongyu, WANG Ziwu
    Xinjiang Oil & Gas    2024, 20 (4): 1-7.   DOI: 10.12388/j.issn.1673-2677.2024.04.001
    Abstract78)      PDF (990KB)(53)       Save

    High-pressure gypsum salt beds and low-pressure clastic rock target beds are commonly developed in the piedmont zone of Tarim Basin,and the pressure difference between these two stratigraphic systems generally exceeds 20 MPa. Because of the inaccuracy of geological stratigraphic determination during drilling,it is highly likely to drill through the gypsum salt bed into the target bed and then trigger severe lost circulation. To solve the problem of severe lost circulation at the salt bottom of Tarim piedmont zone,this paper evaluates the performance parameters of plugging materials such as pressure-bearing capacity and settling velocity,identifies the optimal conditions (velocity and mass) of oil- and water- based drilling fluid (OBM and WBM) settling plugging pills respectively,and finally develops the high density large pressure difference settling plugging technology specialized for OBM and WBM,based on the known mechanism of the severe lost circulation problem (drilling induced communication between high and low pressure formations) and the principle of the "bottle plug" plugging practice. Specifically,optimal plugging pills are expected to form in the case of OBM with a oil-water ratio of 50:50 and ES of 200-300 V or WBM with 0.2% XC + 0.2% demulsifier + plugging agents. The developed settling plugging technology has been successfully tested in three wells in Tarim piedmont zone,and Well DB1302 was found with a pressure bearing capacity of 30 MPa,demonstrating excellent application performance.

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    Construction and Performance Evaluation of Nano Microemulsion Oil Displacement System#br#
    ZHENG Cunchuan, ZHANG Liwei, XU Jinshan, ZEN Meiting, FU Gaofeng, FU Yulong
    Xinjiang Oil & Gas    2023, 19 (1): 89-94.   DOI: 10.12388/j.issn.1673-2677.2023.01.013
    Abstract125)      PDF (1731KB)(52)       Save

    Microemulsion flooding is an effective technology to improve oil recovery. Microemulsions were prepared using dodecyl betaine,isopropanol and 90 ~ 120 petroleum ether. The impact of Km,the ratio of cosurfactant to surfactant,on microemulsion was studied using the pseudo-ternary phase diagram method. The results show that with the increase of Km,the area of microemulsion formed increased first and then decreased,and reached the maximum when Km = 2. The nano-microemulsion oil displacement agent was prepared using the microemulsion dilution method. The particle size distribution and interfacial tension were measured by laser scattering system and spinning drop interface tensiometer,respectively. The results show that the average particle size is 149.0 nm when the concentration is 0.25 %,and the minimum interfacial tension is 1.780 44 mN/m when the concentration is 0.3 %. The properties of the nano microemulsion oil displacement agent were evaluated in the laboratory. The results show that it had good dispersion stability at different temperatures. The maximum foam height is 140 mm when the concentration is 0.5%;the maximum emulsification efficiency is 55.0% when the concentration is 0.3%;the maximum oil displacement efficiency is 88.39% when the concentration is 0.2%;when the concentration is 0.3%,the total oil recovery factor is 86.78%.

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    Numerical Simulation of Fracture Propagation Pattern in the Presence of Gravel

    WANG Tao, CHENG Leiming, XIANG Yuankai, CHENG Ning, WANG Bo, ZHOU Hang
    Xinjiang Oil & Gas    2023, 19 (1): 42-48.   DOI: 10.12388/j.issn.1673-2677.2023.01.007
    Abstract104)      PDF (4977KB)(52)       Save

    Large-scale hydraulic fracturing is the essential technology for cost-effective and efficient development of tight sandy conglomerate reservoirs. Gravel parameters are considered the key factors that influence the hydraulic fracture geometry. The existence of gravels can make it even harder to complete fracturing stimulation. The complex fracture geometry,high tortuosity,and shorter supporting fracture length make it difficult to achieve the designed fracture conductivity. In this research,the continuous-discontinuous element method (CDEM) was applied to establish a 2D full fluid-solid coupling fracture propagation model to explore the influence of stress difference,gravel content,and flow rate on the fracture propagation geometry. The numerical simulation results show that:the multi-phase media hydraulic fracturing model based on the CDEM method can accurately simulate the overall fracture propagation geometry under the influence of gravel;the fractures will divert and generate a tortuous fracture when meeting high strength gravel;in reservoirs with high stress,hydraulic fractures tend to pass around the gravel and then divert to the direction of the maximum horizontal principal stress;in the presence of gravel,the fracture propagation will shape a high-pressure zone and generate more micro-fractures,thus increasing the stimulated reservoir volume. This study lays a theoretical basis for optimization of the fracturing design of conglomerate reservoirs.

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