库车前陆冲断带多尺度裂缝成因及其储集意义
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摘要
以库车前陆冲断带深层白垩系巴什基奇克组砂岩储集层为例,利用地表露头、岩心、薄片和成像测井等资料,运用工业CT、激光共聚焦、阴极发光、电子探针、扫描电镜等技术手段,基于裂缝开度大小对裂缝进行分级分类,系统研究库车前陆冲断带砂岩储集层天然裂缝类型、特征、成因、期次及形成序列等,并分析不同尺度天然裂缝的储集意义。库车前陆冲断带深层致密砂岩储集层天然裂缝可分为4级:百微米级以上宏观构造裂缝(Ⅰ级)切割单砂体,形成优势运移通道,提高储集层渗透率;十微米级—百微米级微细构造伴生缝(Ⅱ级)切割基质颗粒,连通基质大孔隙,改善渗流性能;微米级粒缘显微成岩缝(Ⅲ级)连通中小孔隙,改善孔隙连通网络,提高天然气运移充注效率;纳米级基质裂隙(Ⅳ级)沟通粒内微孔隙,扩大储集空间,增加储量规模。Ⅰ级与Ⅱ级构造成因裂缝主要发育有3期,其中早期和中期裂缝主要为半充填—充填,是油气大规模充注前的上新世早期以前形成,晚期开启裂缝与油气大规模充注同期或略晚,形成于上新世末期之后。裂缝网络对孔隙度贡献率较低,但在平行裂缝走向上,裂缝可以提高渗透率2~3个数量级。
Natural fractures in the deep Cretaceous Bashijiqike Formation sandstone reservoirs of Kuqa foreland thrust belt, NW China, are classified according to fracture aperture based on the data of outcrops, cores, thin sections and imaging logging, using industrial CT scanning, laser scanning confocal microscope(LSCM), cathodoluminescence(CL), electron probe, and scanning electron microscopy(SEM). The types, characteristics, genesis ages and formation sequence as well as reservoir significance of such natural fractures are examined. Four categories of fractures are classified. Category Ⅰ(aperture>100 μm) is macro structural fractures, which cut single sand body to form the dominant migration pathway, helping to increase the reservoir permeability. Category Ⅱ(aperture=10-100 μm) is associated micro structural fractures, which cut matrix grains to connect large matrix pores and improve the seepage performance. Category Ⅲ(aperture=1-10 μm) is micro digenetic fractures at grain edges, which connect medium and small pores to improve the pore network connectivity and the gas migration and charging efficiency. Category Ⅳ(aperture<1 μm) is nano-scale matrix fissures, which connect intragranular micro pores to expand the reservoir space, thereby increasing the reserves scale. Category Ⅰ and Category Ⅱ fractures were developed in three stages(early, middle and late). The early-and middle-stage fractures, predominantly half-filled–filled fractures, were formed before early Pliocene when extensive oil and gas charging had not occurred. The late-stage opened fractures were formed after the Late Pliocene, they were at the same time as or later slightly than extensive oil and gas charge. The fracture network has low contribution to porosity, but it can improve the permeability by 2-3 orders of magnitudes in the parallel direction of fractures.
Natural fractures in the deep Cretaceous Bashijiqike Formation sandstone reservoirs of Kuqa foreland thrust belt, NW China, are classified according to fracture aperture based on the data of outcrops, cores, thin sections and imaging logging, using industrial CT scanning, laser scanning confocal microscope(LSCM), cathodoluminescence(CL), electron probe, and scanning electron microscopy(SEM). The types, characteristics, genesis ages and formation sequence as well as reservoir significance of such natural fractures are examined. Four categories of fractures are classified. Category Ⅰ(aperture>100 μm) is macro structural fractures, which cut single sand body to form the dominant migration pathway, helping to increase the reservoir permeability. Category Ⅱ(aperture=10-100 μm) is associated micro structural fractures, which cut matrix grains to connect large matrix pores and improve the seepage performance. Category Ⅲ(aperture=1-10 μm) is micro digenetic fractures at grain edges, which connect medium and small pores to improve the pore network connectivity and the gas migration and charging efficiency. Category Ⅳ(aperture<1 μm) is nano-scale matrix fissures, which connect intragranular micro pores to expand the reservoir space, thereby increasing the reserves scale. Category Ⅰ and Category Ⅱ fractures were developed in three stages(early, middle and late). The early-and middle-stage fractures, predominantly half-filled–filled fractures, were formed before early Pliocene when extensive oil and gas charging had not occurred. The late-stage opened fractures were formed after the Late Pliocene, they were at the same time as or later slightly than extensive oil and gas charge. The fracture network has low contribution to porosity, but it can improve the permeability by 2-3 orders of magnitudes in the parallel direction of fractures.
引文
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[2]吴林,管树巍,任荣,等.前寒武纪沉积盆地发育特征与深层烃源岩分布:以塔里木新元古代盆地与下寒武统烃源岩为例[J].石油勘探与开发,2016,43(6):905-915.WU Lin,GUAN Shuwei,REN Rong,et al.The characteristics of Precambrian sedimentary basin and the distribution of deep source rock:A case study of Tarim Basin in Neoproterozoic and source rocks in Early Cambrian,Western China[J].Petroleum Exploration and Development,2016,43(6):905-915.
[3]张惠良,张荣虎,杨海军,等.超深层裂缝-孔隙型致密砂岩储集层表征与评价:以库车前陆盆地克拉苏构造带白垩系巴什基奇克组为例[J].石油勘探与开发,2014,41(2):158-167.ZHANG Huiliang,ZHANG Ronghu,YANG Haijun,et al.Characterization and evaluation of ultra-deep fracture-pore tight sandstone reservoirs:A case study of Cretaceous Bashijiqike Formation in Kelasu tectonic zone in Kuqa foreland basin,Tarim,NW China[J].Petroleum Exploration and Development,2014,41(2):158-167.
[4]刘春,张惠良,韩波,等.库车坳陷大北地区深部碎屑岩储层特征及控制因素[J].天然气地球科学,2009,20(4):504-512.LIU Chun,ZHANG Huiliang,HAN Bo,et al.Reservoir characteristics and control factors of deep-burial clastic rocks in Dabei zone of Kuche Sag[J].Natural Gas Geoscience,2009,20(4):504-512.
[5]LIU Chun.Characteristics and origin of microfracture in lower Cretaceous tight sandstone from Kuqa foreland basin,NW China[R].SPE 114164,2013.
[6]丁文龙,王兴华,胡秋嘉,等.致密砂岩储层裂缝研究进展[J].地球科学进展,2015,30(7):737-750.DING Wenlong,WANG Xinghua,HU Qiujia,et al.Progress in tight sandstone reservoir fractures research[J].Advances in Earth Science,2015,30(7):737-750.
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[8]昌伦杰,赵力彬,杨学君,等.应用ICT技术研究致密砂岩气藏储集层裂缝特征[J].新疆石油地质,2014,35(4):471-475.CHANG Lunjie,ZHAO Libin,YANG Xuejun,et al.Application of Industrial Computed Tomography(ICT)to research of fractured tight sandstone gas reservoirs[J].Xinjiang Petroleum Geology,2014,35(4):471-475.
[9]詹彦,侯贵廷,孙雄伟,等.库车坳陷东部侏罗系砂岩构造裂缝定量预测[J].高校地质学报,2014,20(2):294-302.ZHAN Yan,HOU Guiting,SUN Xiongwei,et al.Quantitative prediction of tectonic fractures of Jurassic Sandstones in the eastern Kuche Depression[J].Geological Journal of China Universities,2014,20(2):294-302.
[10]屈海洲,张福祥,王振宇,等.基于岩心-电成像测井的裂缝定量表征方法:以库车坳陷ks2区块白垩系巴什基奇克组砂岩为例[J].石油勘探与开发,2016,43(3):425-432.QU Haizhou,ZHANG Fuxiang,WANG Zhenyu,et al.Quantitative fracture evaluation method based on core-image logging:A case study of Cretaceous Bashijiqike Formation in ks2 well area,Kuqa depression,Tarim Basin,NW China[J].Petroleum Exploration and Development,2016,43(3):425-432.
[11]赵文韬,侯贵廷,孙雄伟,等.库车东部碎屑岩层厚和岩性对裂缝发育的影响[J].大地构造与成矿学,2013,37(2):603-610.ZHAO Wentao,HOU Guiting,SUN Xiongwei,et al.Influence of layer thickness and lithology on the fracture growth of clastic rock in east Kuqa[J].Geotectonica et Metallogenia,2013,37(2):603-610.
[12]王珂,戴俊生,贾开富,等.库车拗陷A气田砂泥岩互层构造裂缝发育规律[J].西南石油大学学报(自然科学版),2013,35(2):63-70.WANG Ke,DAI Junsheng,JIA Kaifu,et al.Research on development regularity of structural fractures in sand-mud interbed of A gas field,Kuqa Depression[J].Journal of Southwest Petroleum University(Science&Technology Edition),2013,35(2):63-70.
[13]张惠良,张荣虎,杨海军,等.构造裂缝发育型砂岩储层定量评价方法及应用:库车前陆盆地白垩系为例[J].岩石学报,2012,28(3):827-835.ZHANG Huiliang,ZHANG Ronghu,YANG Haijun,et al.Quantitative evaluation methods and applications of tectonic fracture developed sand reservoir:A Cretaceous example from Kuqa foreland basin[J].Acta Petrologica Sinica,2012,28(3):827-835.
[14]王振宇,陶夏妍,范鹏,等.库车坳陷大北气田砂岩气层裂缝分布规律及其对产能的影响[J].油气地质与采收率,2014,21(2):51-56.WANG Zhenyu,TAO Xiayan,FAN Peng,et al.Distribution rule of fractures and their effect on deliverability in sandstone reservoirs,Dabei gas field,Kuqa foreland basin[J].Petroleum Geology and Recovery Efficiency,2014,21(2):51-56.
[15]张福祥,王新海,李元斌,等.库车山前裂缝性砂岩气层裂缝对地层渗透率的贡献率[J].石油天然气学报,2011,33(6):149-152.ZHANG Fuxiang,WANG Xinhai,LI Yuanbin,et al.The contribution of fractures of Kuqa foreland fractured sandstone gas reservoirs to permeability[J].Journal of Oil and Gas Technology,2011,33(6):149-152.
[16]王珂,戴俊生,商琳,等.曲率法在库车坳陷克深气田储层裂缝预测中的应用[J].西安石油大学学报(自然科学版),2014,29(1):34-39.WANG Ke,DAI Junsheng,SHANG Lin,et al.Reservoir fracture prediction of Keshen gasfield in Kuqa Depression using principal curvature method[J].Journal of Xi’an Shiyou University(Natural Science Edition),2014,29(1):34-39.
[17]王珂,戴俊生,张宏国,等.裂缝性储层应力敏感性数值模拟:以库车坳陷克深气田为例[J].石油学报,2014,35(1):123-133.WANG Ke,DAI Junsheng,ZHANG Hongguo,et al.Numerical simulation of fractured reservoir stress sensitivity:A case from Kuqa depression Keshen gas field[J].Acta Petrolei Sinica,2014,35(1):123-133.
[18]卢华复,贾东,陈楚铭,等.库车新生代构造性质和变形时间[J].地学前缘,1999,6(4):215-221.LU Huafu,JIA Dong,CHEN Chuming,et al.Nature and timing of the Kuqa Cenozoic structures[J].Earth Science Frontiers,1999,6(4):215-221.
[19]王招明.试论库车前陆冲断带构造顶蓬效应[J].天然气地球科学,2013,24(4):671-677.WANG Zhaoming.Discussion of ceiling effect in foreland thrust belt of Kuqa Depression[J].Natural Gas Geoscience,2013,24(4):671-677.
[20]刘春,张荣虎,张惠良,等.塔里木盆地库车前陆冲断带不同构造样式裂缝发育规律:证据来自野外构造裂缝露头观测[J].天然气地球科学,2017,28(1):52-61.LIU Chun,ZHANG Ronghu,ZHANG Huiliang,et al.Fracture development of different structural styles in Kuqa foreland thrust belt:From outcrop observation of structural fracture[J].Natural Gas Geoscience,2017,28(1):52-61.
[21]范高尔夫-拉特T D.裂缝油藏工程基础[M].秦同洛,译.北京:石油工业出版社,1986:31-41.VAN COLF-LATS T D.Fundamentals of fractured reservoir engineering[M].QIN Tongluo,Trans.Beijing:Petroleum Industry Press,1986:31-41.
[22]刘春,张荣虎,张惠良,等.致密砂岩储层微孔隙成因类型及地质意义:以库车前陆冲断带超深层储层为例[J].石油学报,2017,38(2):150-159.LIU Chun,ZHANG Ronghu,ZHANG Huiliang,et al.Genetic types and geological significance of micro pores in tight sandstone reservoirs:A case study of the ultra-deep reservoir in the Kuqa foreland thrust belt,NW China[J].Acta Petrolei Sinica,2017,38(2):150-159.