1. Exploration and Development Research Institute,Changqing Oilfield Company,PetroChina,Xi'an 710021,China 2. Beijing Energy Technology Co.,Ltd.,Beijing 100012,China
Based on the comprehensive utilization of drilling data,logging data and 2-D seismic data,the authors hold that the tight reservoir of Yanchang Formation in Heshui area of Ordos Basin has developed a complex fault system consisting of strike-slip faults,fault damage zones and small-scale fractures,which together affect the heterogeneity and flow capacity of underground reservoirs,thus having an important impact on oil and gas production.So faults,fault damage zones and natural small-scale fractures should be treated as a system to analyze the fracture characteristics of ultra-low permeability reservoirs.The authors hold that only considering small-scale fractures is obviously not comprehensive.This understanding has important implications for the study of fractures in ultra-low permeability reservoirs in Ordos Basin.
Zeng L B, Shi C G, Wang Y K , et al. The pressure sensitivity of fractures and its development significance for extra low-permeability sandstone reservoirs in Ordos Basin[J]. Engineering Sciences, 2007,9(11):35-38.
Yang K W, Shi C E, Wan X L , et al. Study on the difference between the natural fractures in Chang 8 and Chang 6 reservorirs in Ordos Basin and its influence on the development of the reservoirs[J]. Journal of Xi'an Shiyou University:Natural Science Edition, 2008,23(6):37-41.
Huang F Z, Han Z Y . Influence of well pattern and fracture system adaptability on water injection development in ultra-low permeability reservoirs—Taking Chang 6 reservoir development of Yan 25 area in Ansai oilfield of Ordos Basin as an example[J]. Journal of Shengli College China University of Petroleum, 2010,24(3):12-13.
Zhao Z F, Chen C H, Fan F L . Analysis of the natural fracture effectiveness in Longdong area of Ordos Basin[J]. Petroleum Geology and Oilfield Development in Daqing, 2014,33(6):91-94.
Zhao X Y, Zeng L B, Jin B G , et al. Discussion on optimal injection pressure of fractured low-permeability sandstone reservoirs——A case sudy from Wangyao Block in Ansai Oilfield,Ordos Basin[J]. Oil & Gas Geology, 2015,36(5):855-861.
Zeng L B, Zheng C B . Origin of the regional fracturing in Yanchang epoch,Shanganning basin,significance for geology of oil and gas[J]. Regional Geology of China, 1999,18(4):391-396.
Zhang L Y, Fan K, Liu J D , et al. Quantitative prediction of distribution of tectonic fractures in the Yanchang formation in the Zhenyuan-Jingchuan area,Ordos Basin[J]. Journal of Geomechanics, 2006,12(4):476-484.
Zeng L B, Li Z X, Shi C E , et al. Characteristics and origin of fractures in the extra low permeability sandstone reservoris of the Upper Triassic Yanchang formation in the Ordos basin[J]. Acta Geologica Sinica, 2007,81(2):174-180.
Nan J X, Wang S R, Yao W H , et al. Micro-fractures in extra-low permeability reservoir of Yanchang formation in Ordos Basin[J]. Lithologic Reservoirs, 2007,19(4):40-44.
Zeng L B, Gao C Y, Qi J F , et al. Fracture distribution and seepage of ultra-low permeability sandstone reservoirs in Longdong area of Ordos Basin[J]. Sci China Ser D-Earth Sci, 2008,38(s1):41-47.
Zhou X G, Zhang L Y, Fan K . Characteristics and distribution of tectonic fractures in Chang 61 low-permeable reservoir in Wuqi area in Ordos Basin[J]. Journal of Jilin University:Earth Science Edition, 2008,38(1):43-49.
Zhou X G, Zhang L Y, Huang C J , et al. Palaeo stress judgement of tectonic fractures in Chang 61 low permeable reservoir in Yanhewan area,Ordos Basin in main forming period[J]. Geoscience, 2009,23(5):843-851.
Wang R F, Sun W . A study on micro cracks in super-low permeability sandstone reservoir of the Upper Triassic Yanchang formation in the Ordos Basin[J]. Geological Review, 2009,55(3):444-448.
Liang X W, Han Y L, Wang H H , et al. Fracture characteristics and geological significance of Upper Triassic Yangchang formation in Jiyuan area,Ordos Basin[J]. Lithologic Reservoirs, 2009,21(2):49-53.
Tian Y M, Shi Z J, Song J H , et al. Characteristics of fractures in the sandstone reservoirs of Yanchagn formation in Southeastern Ordos Basin[J]. Journal of Geomechanics, 2009,15(3):281-288.
Deng H C, Zhou W, Jiang W L , et al. Genetic mechanism and development periods of fracture in Yanchang and Yan'an formatin of Western Mahuangshan block in Ordos Basin[J]. Journal of Jilin University:Earth Science Edition, 2009,39(5):811-817.
Fan H C, Huang Z L, Gao G , et al. Fracture development characteristics of Chang 4+5~ Chang 6 oil formation and its control on crude oil migration and accumulation in Hujianshan area of Ordos Basin[J]. Journal of Oil and Gas Technology(J. JPI), 2011,33(1):11-17.
Wang Q Y, Zheng R C, Liang X W , et al. Feature and genesis of the reservoir fractures of Upper Triassic Yanchang formation in Jiyuan area,Ordos Basin[J]. Journal of Chengdu University of Technology:Science & Technology Edition, 2011,38(2):220-228.
Gao J W . Paleotectonic stress field simulation and analysis of favorable zones of fractured reservoirs in Nanniwan area of Ordos Basin[J]. Journal of Yanan University:Natural Science Edition, 2011,30(2):31-34.
Bao Z W, Ji W R, Qiao S H , et al. Study on Fracture of sandstone reservoir in Zhidan area of central north Shaanxi Slope in Ordos[J]. Journal of Yanan University:Natural Science Edition, 2012,31(2):74-77.
Cui J J, Zhu H F, Li X G , et al. Characteristics and control factors for the Chang 6 fractured-type reservoir in the west Fuhuang prospecting District,Ordos Basin[J]. Acta Geologica Sichuan, 2012,32(3):295-298.
Li Z, Tang J, Zhang Y P , et al. Fracture characteristics of Chang 8 reservoir of Yanchang formation in Xiasiwan area,Ordos Basin[J]. Lithologic Reservoirs, 2012,24(5):65-70.
Liu W G, Zhou L F, Gao S J . Fracture characteristics of the Triassic Yanchang Formation in the midwest of Ordos Basin[J]. Lithologic Reservoirs, 2012,24(6):66-71.
Wu X B, Chen Y D, Gao H , et al. The study of fracture system and significance of Wuqi Chang 6 super-low permeability oil reservoir in Ordos Basin[J]. Xinjiang Geology, 2014,32(5):514-517.
Liu X J, Yang S D, Xie G , et al. The study of relationship between fracture characteristics and yield of Chang 8 section in Heshui area,Ordos Basin[J]. Petroleum Geology and Recovery Efficiency, 2014,21(6):57-60.
Zhao X Y, Zeng L B, Wang X D , et al. Differences of natural fracture characteristics and their development significance in Chang 6,Chang 7 and Chang 8 reservoir,Ningxian-Heshui area,Ordos Basin[J]. Chinese Journal of Geology, 2015,50(1):274-285.
Zhang X L, Liu X, Chen Z B , et al. Fracture characteristics and stages of Yanchang Formation in Huangling area of southeastern Ordos Basin[J]. Science Technology and Engineering, 2015,15(19):10-14.
Ma S, Lin W, Wang Q C , et al. Shear fracture direction and mechanical characteristics of the middle Yanchang Formation,southern Ordos Basin,China[J]. Chinese Science Bulletin, 2016,61(21):3049-3063.
Wang J Y, Ju W, Shen J , et al. Quantitative prediction of tectonic fracture distribution in the Chang 71 reservoirs of the Yanchagn Formation in the Dingbian area,Ordos Basin[J]. Geology and Exploration, 2016,52(5):966-973.
Liu Y, Xie R C, Wu C Y , et al. Fracture identification of Tight Reservoir in Chang 6,south of Ordos Basin[J]. Sichuan University of Arts and Science Journal, 2017,27(2):29-32.
Wang B L, Zhou W, Deng H C , et al. Quantitative evaluation of fracture distribution of Chang 9 member in Honghe oilfield,Ordos Basin[J]. Xinjiang Petroleum Geology, 2013,34(6):653-656.
Yao Z H, Zhang M S, Zeng L B , et al. Analysis of the faults in the northern Ordos BaSIN,Northwest China[J]. Petroleum Exploration and Development, 2003,30(2):20-23.
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Kim Y S, Peacock D C P, Sanderson D J .Fault damage zones[J]. Journal of Structural Geology, 2004,26:503-517.