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01 February 2019, Volume 40 Issue 1 Previous Issue    Next Issue

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Petroleum Exploration Achievements and Future Targets of Tarim Basin TIAN Jun 2019, 40 (1):  1-1.  doi: 10.7657/XJPG20190101 Abstract ( 343 )   PDF (300KB) ( 774 )   Save Ever since the foundation of Tarim Oilfield Company on April 10, 1989, great achievements have been obtained in 3 major fields: Kuqa foreland depression, carbonate rocks and clastics in the platform region with the cumulative proved oil and gas reserves amounting to 2.88 billion tons (equivalent). Tarim oilfield has become the major source area for the West-to-East natural gas transmission project and the third large oil and gas field in the mainland China. During the past 30 years of exploration practice, geological understandings about the foreland Kuqa depression, Southwest depression, carbonate rocks in the platform region and clastics in the platform region were continuously deepened, and the source rock, reservoir-cap rock assemblage, structure style, trap and reservoir model were identified for the 3 petroleum systems such as Kuqa depression, platform region and Southwest depression. The remaining exploration potentials of Tarim basin are enormous. The fine exploration should be carried out in the Kelasu tectonic belt of Kuqa depression, clastics in the western Tabei uplift, Ordovician Yijianfang formation in Tabei—Manxi area. The researches and exploration of Qiulitage tectonic belt in Kuqa depression, Jurassic series in the northern tectonic belt, Ordovician deep series in the platform region, Cambrian subsalt strata and piedmont area in the Southwest depression should be strengthened and the strategic breakthrough can be made Related Articles | Metrics

Discovery of Kelasu Subsalt Deep Large Gas Field, Tarim Basin YANG Haijun, LI Yong, TANG Yangang, LEI Ganglin, ZHOU Lu, ZHOU Peng 2019, 40 (1):  1-1.  doi: 10.7657/XJPG20190102 Abstract ( 178 )   PDF (300KB) ( 349 )   Save Kelasu tectonic belt is located in the northern Kuqa depression and the discovered subsalt large-deep gas field in the tectonic belt belongs to ultra-deep high-pressure gas fields with low-porosity high-yield fractured sandstones. Up to now 22 oil and gas reservoirs have been discovered in the gas field, which are the major production areas for natural gas in Tarim basin. There was no significant breakthrough after the discovery of Kela 2 gas field in 1998. Since 2006, the research of the deep zones in Kelasu tectonic belt has been strengthened, and in Aug., 2008 commercial gas flows were gained from the Cretaceous Bashijiqike formation in the Well Keshen-2 which is located in the Keshen-2 structure of Keshen area and the daily gas production was 40×104 m3, marking a great breakthrough has been gained. Then over 10 years of study, technological breakthroughs have been made on foreland basin exploration technology, petroleum geological theory and production practice, which provides guidance for the discovery of the Kelasu subsalt deep large gas field. The researches on trap identification in complex mountain areas, reservoir forming mechanism and hydrocarbon accumulation, speedy drilling and reservoir reformation effectively support the efficient exploration and development of the Kelasu subsalt deep large gas field Related Articles | Metrics

Subsalt Structural Styles of Keshen Section in Kelasu Tectonic Belt HOU Guiting1, SUN Shuai1, ZHENG Chunfang1, TANG Yangang2, ZHOU Lu2, MO Tao2 2019, 40 (1):  1-1.  doi: 10.7657/XJPG20190103 Abstract ( 126 )   PDF (300KB) ( 582 )   Save The exploration and development practices in the Cretaceous Bashijiqike formation of the Kelasu tectonic belt in Kuqa depression reveal that the fractures are featured with vertical zonation, which are possibly constrained by neutral surfaces of anticlines. It is necessary to rebuild the structural style of the Kelasu tectonic belt because the present model for structural style classification cann’t explain the vertical zonation of fractures. Selecting the Keshen section of the Kelasu tectonic belt as the study area, taking the interlimb angle of fold as the main element and combining with the fault combination configuration, the paper rebuilds the subsalt structure styles of the Keshen section in the Kelasu tectonic belt on the basis of 3D seismic interpretation. The results show that the structural styles of the Keshen section can be divided into 2 types such as gentle fold and open fold according to the interlimb angle of fold; according to the fault combination configuration, the gentle fold is further divided into double-thrust gentle fold, back-thrust gentle fold and recoil gentle fold, and the open fold is divided into double-thrust and back-thrust open folds. The structures to the north of the Keshen fault are imbricate fault anticlines made up of open and gentle folds, and the structures to the south of the Keshen fault are imbricate structures of gentle-fold faulted anticline. The distribution of fractures is closely related to the interlimb angle, the thickness and the distribution range of tension fissure zones in the open folds are much larger than those in the gentle folds, and faults has an influence on the distribution of the fractures around them. The classification of the structural style provides a foundation for the further study on the fracture development and genetic mechanism of different structural styles Related Articles | Metrics

Influences of Indosinian Structures on Later Structural Deformation and Sedimentation in Piedmont of Western Kunlun Mountains CHENG Xiaogan1,2, WU Hongxiang1,2, LI Yong3, CHEN Hanlin1,2, ZHANG Fengqi1,2, SHI Jun3 2019, 40 (1):  1-1.  doi: 10.7657/XJPG20190104 Abstract ( 108 )   PDF (300KB) ( 191 )   Save The Indosinian structures exert important controls on the structural deformation in the late stages and sedimentation during Jurassic to Cretaceous in the piedmont of the western Kunlun Mountains in the southwestern margin of Tarim basin. It is very difficult to identify the structural features during Indosinian period in the study area due to the strong reworking since Cenozoic. The middle segment of the western Kunlun Mountains where the tectonic activity was relatively weak is selected to be the study object. Based on the comprehensive study on field outcrop, drilling and seismic data, fold thrust belts were developed in the piedmont of the western Kunlun Mountains and a series of thrust faults and the anticlines with steep north and east flanks and gentle south and west flanks were formed, which may be related to the N-NE compression resulted from the continental collision between the Late Triassic Tarim plate and Qiangtang terrane. These Indosinian structures were reactivated due to the compression during the Late Himalayan movement, resulting in the superimpositions of the anticlines of two periods and the coincidence of structural highs. Therefore, the structural framework during the Indosinian movement significantly constrained the structural deformation during the Late Himalayan movement. The paleostructure during the Indosinian period laid a foundation for the paleotopographic framework of Mesozoic and played an important control action on the sedimentation during Jurassic to Cretaceous. The NW-SE trending paleohigh controlled by deep-burial thrust faults during Indosinian is the main factor resulting in the differences in distribution and physical properties of Cretaceous reservoir Related Articles | Metrics

Physical Simulation of Multi-Period Dissolution in Cretaceous Reservoirs of Kelasu Tectonic Belt, Kuqa Depression ZHANG Ronghu1, ZENG Qinglu1, LI Jun2, SHE Min1, YU Chaofeng1 2019, 40 (1):  1-1.  doi: 10.7657/XJPG20190105 Abstract ( 75 )   PDF (300KB) ( 123 )   Save There are lots of disputes on the pore genesis and its preservation mechanism in deep-ultra-deep reservoirs in petroliferous basins. Taking the ultra-deep Cretaceous Bashijiqike formation in the Kelasu tectonic belt of Kuqa depression in Tarim basin as an example, the paper makes an in-depth discussion. High-temperature high-pressure dissolution simulation experiments are performed to study the dissolution characteristics of the formation fluids under 3 different diagenetic environments. The results show that during the early diagenesis supergene period, the dissolution of CO2-rich meteoric freshwater was very significant, which was easy to dissolve feldspar or carbonate minerals and quartz was a little bit difficult to be dissolved. During the early diagenetic shallow-medium burial period, alkali dissolution in saline environment took the second place, and quartz, potassium feldspar and albite suffered from the dissolutions of different degrees. During the middle diagenesis period the dissolution of organic acid was weak, which was characterized by the dissolutions along fractures, gypsum dissolution and calcite precipitation. The dissolutions during the early diagenesis period are dominant. The surface porosities of reservoir residual intergranular pores and intragranular dissolved pores range from 2% to 4%, accounting for 50%~80% of the total reservoir porosity. For the reservoir with the burial depth over 5 500 m, the experimental simulation of the dissolution can reasonably explain the causes of the dissolved pores, which helps to fully understand the genesis of the ultra-deep high-quality reservoirs in the Kelasu tectonic belt and provides basis for the study on deep-ultra-deep reservoirs with multi-period of tectonic movements of the foreland thrust belts in the western basins of China Related Articles | Metrics

Hydrocarbon Inclusion Characteristics of Jurassic Ahe Formation and Analysis on Petroleum Accumulation in Dibei Gas Reservoir of Kuqa Depression ZHANG Baoshou1, YANG Haijun1, ZHANG Nai2, ZHAO Qing1 2019, 40 (1):  1-1.  doi: 10.7657/XJPG20190106 Abstract ( 92 )   PDF (300KB) ( 155 )   Save Two periods of hydrocarbon inclusions are observed in the Jurassic Ahe formation of Dibei gas reservoir, including the hydrocarbon inclusions of period Ⅰ with yellow fluorescence and the inclusions of period Ⅱ with blue fluorescence. The analysis on the optical characteristics and components of the inclusions shows that the inclusions of period Ⅰ are mature intermediate oil and those of period II are mature-over mature light condensate oil. On the basis of oil-source rock correlation, it is considered that the major source rocks of the two periods of hydrocarbon inclusions are the Triassic lacustrine source rocks in Yangxia sag. The results of temperature measurement, capture depth calculation and burial history restoration for the conclusions indicate that the inclusions of period Ⅰ formed during the early-medium deposition period (17—10 Ma) of the Miocene Kangcun formation, and the inclusions of period Ⅱ formed in the late deposition period of the Miocene Kangcun formation to the medium deposition period of the Kuche formation (10—5 Ma). The Yiqikelike tectonic belt deposited rapidly since Miocene, resulting in the multi-period and continuous reservoir accumulation Related Articles | Metrics

Structural Deformation Styles and Tectonic Evolution Characteristics in Eastern Kuqa Depression ZHANG Wei, XU ZhenpingZHAO Fengquan, WU Shaojun, HUANG Cheng, ZHANG Xueqi 2019, 40 (1):  1-1.  doi: 10.7657/XJPG20190107 Abstract ( 116 )   PDF (300KB) ( 219 )   Save Through analyzing geological maps, seismic section and drilling data, the tectonic deformation styles of the eastern Kuqa depression are studied. The study results show that the structures in the eastern Kuqa depression have some geometric features: banding along N-S orientation, segmentation along W-E orientation and zonation vertically. Taking the gypsum-mudstone layer of the Paleogene Jidike formation as a barrier, 4 layers such as structural layer above gypsum-mudstone, gypsum-mudstone layer, structural layer under gypsum-mudstone and basement are classified. The shrinkage distortion and the plastic deformation of the gypsum-mudstone are dominant in the study area, and the tectonic styles and distributions of the upper structural layer, gypsum-mudstone layer and lower structural layer are significantly different. The upper structural layer is dominated by thrust faults and constricted folds, the gypsum-mudstone layer by plastic deformation structures and the lower structural layer by nappe imbricate structures dominated by thrust faults. The structures in the eastern Kuqa depression display an obvious characteristic of segmented deformation, which can be divided into 4 structural segments, i.e., Yixi-Eastern Qilitage, Yiqikelike-Dina, Tuziluoke-Dina and Tugerming-Yangbei, whose differences are manifested in the distribution of the linear fold belt on the surface of the upper structural layer, the plastic deformation style of the gypsum-mudstone layer and the deformation differences of the lower structural layer. The sections of structural evolution indicate that the eastern Kuqa depression experienced 3 evolution processes including extensional faulted-depression-depression basin in Mesozoic, bending transitional basin in Paleogene and regenerated foreland basin from Neogene to Quaternary. The present structures in the depression were mainly formed in the depositional period of Kuqa formation. Related Articles | Metrics

Tectonic Transformation Characteristics of Subsalt Thrust Belts in Kuqa Foreland Basin NENG Yuan1, LI Yong2, XIE Huiwen2, SHI Kuitai3, REN Chenghao4 2019, 40 (1):  1-1.  doi: 10.7657/XJPG20190108 Abstract ( 91 )   PDF (300KB) ( 200 )   Save Kuqa basin is a Mesozoic-Cenozoic salt-bearing foreland basin developed in the piedmont area of the southern Tianshan Mountains. Influenced by orogenesis, pre-existing structures in the basement and salt rocks, Kuqa foreland basin is characterized by belts along N-S orientation and segments along W-E orientation, leading to the forming of different styles of tectonic transfer zones in Kelasu salt-bearing foreland thrust belt in the northern part of the basin. Based on the latest data of 2D and 3D seismic, drilling and field outcrops, the paper analyzes and summarizes the deformation styles and tectonic transfer characteristics of the foreland thrust belt in Kuqa foreland basin. The study results show that Kuqa foreland basin is featured with vertical stratification and deformation from the southern Tianshan Mountains to the interior of the basin, and the subsalt thrust belts are mainly distributed in the area from the southern Tianshan Mountains to Baicheng sag, which can be divided into 3 deformation zones, i.e., vertically uplifting fault-fold zone, inclined thrust wedge-like zone and nearly-horizontal compressing detachment zone according to their transfer styles. The subsalt thrust belt is divided into 6 structural segments such as Wushi segment, Awat segment, Bozi segment, Dabei segment, Keshen segment and Kela-3 segment, where 4 types of transfer zones are developed, namely strike slip type, margin type, growth type and complex type. In conclusion, the E-W trending, first-order transfer zones are dominated by complex type and strike-slip type, controlling the distribution of main tectonic zones. The margin type and strike slip type are the dominant of subordinate tectonic transfer zones, controlling the distribution of different tectonic segment. And most of the third-order transfer zones belong to growth type, which controls the distribution of local structures Related Articles | Metrics

Distribution of Tectonic Fissure Zones in Subsalt Deep Faulted-Anticline Reservoirs in Kelasu Tectonic Belt ZHOU Lu, LI Yong, JIANG Jun, LI Mei, MO Tao, LI Xiangyun 2019, 40 (1):  1-1.  doi: 10.7657/XJPG20190109 Abstract ( 78 )   PDF (300KB) ( 297 )   Save Kelasu tectonic belt is the key area for natural gas exploration in the Tarim basin, and its main gas-bearing series are the Lower Cretaceous Bashijiqike formation where tectonic fissures are generally developed, which is considered as the key factor for the high and stable deliverability of low-porosity sandstone reservoirs. Based on the study of the characteristics of tectonic fissure development and fissure zone distribution in the subsalt deep faulted-anticline reservoirs of Kelasu tectonic belt, the paper studies the relationship between the fissure zone combination and its deliverability, identifies that the reservoir fractures are dominated by unfilled-half-filled high-angle fractures which are mainly tensile fractures or tensile shear fractures and are characterized by zonal distribution with the fracture zone width and interval of 10~40 m and 10~50 m, respectively. According to the differences in genesis and distribution of fracture zones, 3 types of reservoir fracture zones are classified, i.e., E-W trending fracture zone, N-S trending fracture zone and netlike fracture zone. According to the characteristics of reservoir fracture development and fracture zone spatial combination, the reservoir can be divided into 3 kinds of regions, namely Class Ⅰ high-deliverability region, Class Ⅱ medium-high deliverability region and Class Ⅲ low-deliverability region Related Articles | Metrics

A Dumpflood Coupling Calculation Model of Fractured-Vuggy Reservoirs in Halahatang Oilfield JIANG Tongwen1, XIAO Yang2,3, LIU Zilong23, LUO Shenchao1, ZHANG Liying2,4, WANG Dun1 2019, 40 (1):  1-1.  doi: 10.7657/XJPG20190111 Abstract ( 97 )   PDF (300KB) ( 209 )   Save Water injection is needed in the middle and late development stages of the fractured-vuggy reservoirs in the Halahatang oilfield. The research on self-flow water injection in China is still in its preliminary stage, lacking a complete dumpflood flow model and a development effect optimization software. Starting from the key nodes such as partial perforated water layer, perforation hole, water valve and fracture-vug complex and so on, a flow model is established for fractured-vuggy water layer—fracture-vug complex unit. The software COMSOL is used to simulate the flow of these key nodes, the flow equations of each node are coupled to establish a system-wide flow coupling model, and the numerical simulation and verification are carried out by using Eclipse. The comparative verification results show that the dumpflood numerical simulation model proposed in this paper can be used to predict the self-flow water injection volume and formation pressure variation trend of fractured-vuggy reservoirs, which could provide references for dumpflood design optimization Related Articles | Metrics

Forming Mechanism and Development Measures of Constant-Volume Fractured-Vuggy Carbonate Oil Reservoirs DENG Xingliang, LUO Xinsheng, LIU Yongfu, HUANG Lamei, XIONG Chang 2019, 40 (1):  1-1.  doi: 10.7657/XJPG20190112 Abstract ( 102 )   PDF (300KB) ( 255 )   Save Constant-volume carbonate reservoirs are mostly distributed around branch faults and dominated by cavernous reservoirs which are characterized by weak formation energy, rapid drop of formation pressure, small controlling range of single well and no yield of formation water. The comprehensive analysis shows that with the stop of tectonic movement and hydrocarbon charging, the formation water under the water-oil contact in the branch faults was in a relative static state after hydrocarbon accumulation, calcite separated from the formation water and plugged the early fluid migration paths under the water-oil contact, oil and gas sealed the spaces above the water-oil contact and finally constant-volume reservoirs with no water formed. Based on the study of the dynamic and static characteristics of constant-volume reservoirs and reservoir development practices, the paper presents 2 development measures such as multiple targets in one well and water-injection oil production Related Articles | Metrics

Management of Abnormal Wellbore Plugging in Abnormal-High Pressure Gas Wells, Keshen Gas Field NIE Yanboa, WANG Hongfenga, WANG Shengjuna, ZHU Songbaia, WANG Yimina, YANG Xinyingb 2019, 40 (1):  1-1.  doi: 10.7657/XJPG20190113 Abstract ( 128 )   PDF (300KB) ( 228 )   Save With the development of the Keshen gas field, the number of plugged wells is gradually increasing, and the degree of plugging is becoming more and more serious, which has affected the safe and stable well production and restricted the efficient development of the gas field. Therefore, aiming to the current situation of wellbore plugging and combined with well production performance, in-situ plugging removal situation and systematical analysis of wellbore returns, it is considered that the main factors causing wellbore plugging are scale plug and sand plug, and the plugging mode is divided into three types: scale plug, sand plug and sand-scale mixed plug. According to the characteristics of the three plugging modes and wellbore integrity, four targeted measures are proposed：applying acidizing unplugging technology in the scale plugging wells, applying coiled tubing technology in the sand plugging wells, applying coiled tubing and acidization in the sand-scale mixed plugging wells and replacing pipe string in the pipe string breaking wells. The actual results show that the application of the four measures can effectively dredge the plugged wellbores and meanwhile reduce the production cost Related Articles | Metrics

Characteristics and Distribution of Seepage Barrier in Massive Homogeneous Sandstone Reservoirs CHEN Yuan1, ZHOU Fei1, WANG Weiwei1, SUN Haihang1, JIAO Cuihua2 2019, 40 (1):  1-1.  doi: 10.7657/XJPG20190114 Abstract ( 84 )   PDF (300KB) ( 165 )   Save Regarding the CⅢ reservoir in Tazhong-4 oilfield of Tarim basin and on the basis of core and logging data, 3 types of argillaceous, calcareous and argillaceous-calcareous seepage barriers are characterized. Based on the core observation, lithological and physical property analysis, logging response analysis and forming mechanism study of the seepage barriers, a classification standard is established for the different seepage barriers within reservoirs. Taking the parallel seepage barrier model as the basis of geological model and combining with the production performance, fully occluded, partially occluded and non occluded interwell seepage barriers are classified according to the influences of the barriers on reservoir fluid flowing in the study area, and the vertical and horizontal distribution laws of the barriers are verified. Vertically the seepage barriers of different intervals have different impacts on fluid flowing, and horizontally the seepage barriers are very developed in the northwest of the study area. Fully understanding the reservoir seepage barrier characteristics, distribution and impact on fluid flowing will provide an important geological basis for remaining oil potential tapping and oil recovery improvement Related Articles | Metrics

Gas Injection EOR at Mid-Late Development Stage in Condensate Gas Reservoirs CHEN Lei, LUO Ji, RAO Huawen, FENG Xinluo, KANG Aihong, LE Xiao 2019, 40 (1):  1-1.  doi: 10.7657/XJPG20190115 Abstract ( 139 )   PDF (300KB) ( 247 )   Save Currently the formation pressure in Kekeya condensate gas field has dramatically declined, which is close to or lower than the maximum retrograde condensation pressure, resulting in many wells idle or unable to produce due to the increases of precipitated condensate oil around wellbores and flowing resistance. For this kind of condensate gas reservoir, it is urgent to study whether the gas injection can effectively improve the recovery rate and the development effect. Based on the investigation, indoor dry gas injection into condensate oil extraction experiment, long core displacement experiment and combined with the field injection test results, the paper evaluates and analyzes the feasibility of gas injection EOR at the mid-late development stage in the condensate gas reservoirs. The results show that with the increase of the injected gas volume, the condensate oil extraction effect is significantly enhanced and the fluidity of the condensate oil is obviously improved; gas injection is carried out when the formation pressure is higher than the maximum retrograde condensation pressure and the recovery rate of condensate oil can be improved by 10%~25%; but when the formation pressure is lower than the maximum retrograde condensation pressure, the improvement of the recovery rate of gas injection is very limited. Partial sand bodies with small scales in Kekeya condensate gas field have good sealing capabilities, in which the formation pressure is close to the maximum retrograde condensation pressure. Injection-production parameter optimization, injection-production ratio control and gradual pressurization according to the actual field situation can effectively avoid gas channeling and improve the development effect of the gas reservoirs Related Articles | Metrics

Application of TTI Anisotropic Prestack Depth Migration Technology in Complex Mountain Areas of Kuqa Depression WU Chao, XU Anming, SHANG Jiangwei, CHEN Weili, ZHU Jing, ZHANG Guowei 2019, 40 (1):  1-1.  doi: 10.7657/XJPG20190116 Abstract ( 110 )   PDF (300KB) ( 285 )   Save The complex mountain areas in Kuqa depression are characterized by complicated surface and underground conditions, large elevation difference, developed mountains and many gullies. The Paleogene gypsum salt rock suffered from serious deformation with large variations in thickness. The post-salt layer is high and steep and thrust imbricated faults are developed in the pre-salt target zone, resulting in low signal-to-noise ratio and poor image effect of seismic data. Over many years of research on seismic data processing in complex mountain areas, TTI anisotropic prestack depth migration technology has been developed for relief surfaces. The small smooth datum is used in prestack depth migration modeling. Thickness, time and velocity for static correction are calculated through microlog constrained tomography inversion and high-precision velocity model for shallow layers is established. A reasonable model is established for mid-deep layers by comprehensively using the data of surface outcrop, gravity-magnetic-electronic method, geology and drilling. The qualities and accuracies of the velocity models are improved by using TTI anisotropic parameter extraction and grid tomogrqaphic imaging technology. Based on the TTI anisotropic prestack depth migration processing in the complex mountain areas of Kuqa depression, the signal-to-noise ratio and imaging quality are significantly improved, which lays a foundation for regional geological study and trap identification Related Articles | Metrics

Fracability Evaluation of Deep-Burial Fractured Sandstone Gas Reservoir in Kuqa Depression ZHANG Hui, YIN Guoqing, WANG Zhimin, WANG Haiying 2019, 40 (1):  1-1.  doi: 10.7657/XJPG20190117 Abstract ( 101 )   PDF (300KB) ( 217 )   Save The deep-burial fractured sandstone reservoir in Kuqa depression has experienced strong compressional structure deformation, which is characterized by high magnitude of in-situ stress, strong anisotropy and widely developed of natural fractures. The in-situ stress on natural fracture surface seriously impacts the permeability and fluid flowing in the reservoir. To optimize fracturing stimulation program for gas wells，a research on fracability evaluation is conducted in terms of four geomechanics parameters including in-situ stress, shear-to-effective normal stress ratio on natural fracture, rock brittleness and fracture toughness for the deep-burial fractured sandstone reservoir in Kuqa depression. Based on rock mechanics testing, stress field modeling and analysis of the influence of shear deformation ability of natural fractures on gas well performance after fracturing, a fracability index evaluation model suitable for the fractured tight sandstone with high stress is established. Compared with other fracability models based on rock brittleness and fracture toughness, the new model considers the influences of present in-situ stress and natural fracture on fracturing effect, which is more sensitive to the well-to-well and layer-to-layer fracabilities in the fractured tight reservoir with strong stress, and can be used to optimize fracturing interval, determine perforation location, select injection pressure and optimize pump injection procedure, etc. The fracability evaluation technology has been successfully applied in 30 gas wells in Kuqa depression, which provides basis for quantitative fracturing program optimization in the gas wells which need to be stimulated Related Articles | Metrics

Logging Evaluation for Sandstone Reservoirs in Bashijiqike Formation of Keshen Area, Kuqa Depression XIN Yi1, TANG Jun2, LUO Zhenyuan1, BIE Kang1, TANG Baoyong1, LI Xiaolong1 2019, 40 (1):  1-1.  doi: 10.7657/XJPG20190118 Abstract ( 79 )   PDF (300KB) ( 126 )   Save The Bashijiqike formation in the Keshen area of the Kuqa depression in the Tarim basin has an average burial depth of more than 6 000 m, which belongs to deep-burial low-porosity and ultra-low permeability sandstone reservoirs. The variations of the reservoir lithologies have significant influences on logging responses and reservoir physical properties such as porosity and permeability. The elemental capture spectrum logging and micro-resistivity imaging logging are used to accurately characterize lithologies, and the logging evaluation parameters that can reflect mineral compositions and rock particle distribution are selected, and according to particle sizes the models for porosity and permeability calculation in the Keshen area are established to improve the accuracy of reservoir physical property evaluation. The logging parameters that can characterize the petrological characteristics of the reservoir are extracted by introducing the concept of lithology-lithofacies. Based on the data of elemental capture spectrum logging and imaging logging and the comprehensive consideration of lithology, grain size and sedimentary structure, a reservoir lithology-lithofacies division standard is established for the Bashijiqike formation in the Keshen area. The application of the method in the reservoir evaluation in the Keshen area has gained good results, which could provide references for the evaluation of low-porosity, low-permeability reservoirs with large lithology variations Related Articles | Metrics

Three-Facies Fusion Velocity Analysis and Complex Trap Identification on the Basis of Prestack Depth Migration XU Anming, WU Chao, PAN Yangyong, SHANG Jiangwei, CHEN Weili, HU Chunlei 2019, 40 (1):  1-1.  doi: 10.7657/XJPG20190119 Abstract ( 94 )   PDF (300KB) ( 184 )   Save Keshen 3D seismic area is located in the eastern Kelasu tectonic belt of Kuqa depression, whose surface topography is high and steep with intense fluctuation and complex underground structure, leading to the low signal-to-noise ratio of seismic data and large errors in prestack time migration processing. In order to improve the image quality of target zone and make contact relationship more clear, prestack depth migration is performed. But limited by the precision of the prestack depth migration model, the structural configuration obtained from prestack depth migration processing is different from the actual one. A velocity model of prestack depth migration is proposed to improve the accuracy of structure mapping, which can be used to convert the prestack depth migration data to time domain. Meanwhile, 3-facies fusion velocity analysis of lithofacies, seismic facies and stress facies is carried out. Finally, variable velocity mapping is used to identify complex traps. This method have some advantages such as accurate depth migration data homing, high accuracy of 3-facies fusion velocity field and mature variable velocity mapping technique etc., which can improve the precision of trap identification. The actual drilling data has proved the identified traps in the Keshen 3D area. The study lays a foundation for oil and gas discovery and exploration in the mountain areas of the Kelasu tectonic belt. Keywords: Related Articles | Metrics