鄂尔多斯盆地延长组长7油层组页岩-致密砂岩储层孔缝特征  

Characterization of pores and fracture networks in organic-rich shale and tight sandstone of the Chang-7 member,Triassic Yanchang Formation,Ordos Basin

作　　者：耳闯[1,2] 赵靖舟[1,2] 姚泾利[3,4] 叶小闯 吴伟涛[1,2] 白玉彬[1,2] 邓秀芹[3,4] 孙勃[3,4] 

机构地区：[1]西安石油大学地球科学与工程学院,陕西西安710065 [2]陕西省油气成藏地质学重点实验室,陕西西安710065 [3]中国石油长庆油田分公司勘探开发研究院,陕西西安710018 [4]低渗透油气田勘探开发国家工程实验室,陕西西安710018 [5]中国石油长庆油田分公司第三采气厂,陕西西安710018

出　　处：《石油与天然气地质》2016年第3期341-353,共13页Oil & Gas Geology

基　　金：陕西省自然科学基金项目(2013JQ503);陕西省教育厅重点科研项目(15JS092);国家科技重大专项(2011ZX5018001;2011ZX05001;2011ZX05044)

摘　　要：鄂尔多斯盆地三叠系延长组长7油层组是富有机质页岩和致密砂岩共生发育的富油层位，富有机质页岩既是生油层又是储层，并为致密砂岩提供油源。揭示页岩储层和致密砂岩储层之间的孔缝特征，对认识页岩油和致密油赋存空间和运移机理具有重要意义。综合岩心描述、场发射扫描电镜、激光共聚焦显微镜、核磁共振实验、高压压汞和低温吸附实验等手段，定性描述和定量表征相结合，刻画了富有机质泥页岩和致密砂岩储层中的孔隙类型和孔径大小。富有机质泥页岩孔隙类型包括粒间孔、粒内孔、有机质孔，页岩中孔隙的孔径范围总体分布在50nm以下。页岩中的裂缝包括水平缝、低角度缝、高角度缝和近直立缝。致密砂岩储层孔隙类型包括剩余原生粒间孔、晶间孔和次生孔，且次生孔是主要的孔隙类型。致密砂岩孔隙直径多在2um以上，孔喉半径多集中在73．5nm以下，但对渗透率起贡献作用的孔喉半径区间为73．5—735nm，致密砂岩中同样发育微裂缝和高角度裂缝。页岩和致密砂岩孔隙的形成和演化均受沉积作用和成岩作用的影响，成岩作用流体和烃类流体的运移和充注将页岩和致密砂岩构成了有机整体。延长组长7油层组页岩一致密砂岩系统中存在3类孔缝网络和石油运移路径：①页岩内纳米一微米级孔隙一裂缝网络，形成页岩油的存储空间和石油源内运移的路径；②致密砂岩内纳米级喉道和微米级孔隙的孔隙网络系统，形成致密油的存储空间；③页岩和致密砂岩间差异孔喉结构一微裂缝一裂缝孔喉网络系统，构成源内石油向源外运移的路径。Chang-7 member of the Triassic Yanchang Formation is rich in oil and composed of organic-rich shale and tight sandstone. The shale serves both as source rock to nearby tight sandstone and as reservoirs. An improved appreciation of pores and fracture networks in the shale and tight sandstone reservoirs is of great significance to understand storage space characteristics and migration mechanisms of shale oil and tight oil. Through qualitative description and quantitative chara- cterization, pore types and pore size of the organic-rich shale and tight sandstone were studied by comprehensively utili- zing methods including core description,field emission scanning electronic microscope,laser scanning confocal microsco- py, nuclear magnetic resonance, high pressure Hg injection, and low-temperature thermal adsorption. Organic-rich shale contains intragranular pores,intergranular pores and organic pores, with most pore size less than 50nm. It also contains micro-fractures. Horizontal, low angle, high angle and vertical fractures can all be observed in the shale. The tight sand- stone contains resi dual primary intergranular pores, inter-crystals pores and secondary pores （ the major type）. Pore size is mostly larger than 2 ~xm and pore-throat size is less than 73.5 nm. However, pore-throats that contribute the most to im- proving permeability are those ranging between 73.5 nm and 735 nm. Microfractures and high angle fractures can also be spotted in the tight sandstone. Forming and evolution of pores both in shale and tight sandstone are suggested to be con- trolled by sedimentation and diagenesis. Migration and charging of diagenetic fluids and hydrocarbon fluids worked toge- ther to forge organic-rich shale and tight sandstone into an organic whole. The study also distinguishes three kinds of pore and fracture networks and pathway of oil migration in shale and tight sandstone of the Chang-7 member：（~）nonameter-mi- crometer pores- fracture networks in organic-rich shale （acting as storage space and migratio

关 键 词：孔隙 孔-缝网络 泥页岩 致密砂岩 延长组 鄂尔多斯盆地 

分 类 号：TE122.2[石油与天然气工程—油气勘探]