石油与天然气地质 ›› 2016, Vol. 37 ›› Issue (3): 341-353.doi: 10.11743/ogg20160306

• 油气地质 • 上一篇    下一篇

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

耳闯1,2, 赵靖舟1,2, 姚泾利3,4, 叶小闯5, 吴伟涛1,2, 白玉彬1,2, 邓秀芹3,4, 孙勃3,4   

  1. 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
  • 收稿日期:2015-12-10 修回日期:2016-04-20 出版日期:2016-06-08 发布日期:2016-06-22
  • 作者简介:耳闯(1982—),男,博士、讲师,沉积与储层、非常规油气地质。E-mail:erchuang@xsyu.edu.cn。
  • 基金资助:
    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)。

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

Er Chuang1,2, Zhao Jingzhou1,2, Yao Jingli3,4, Ye Xiaochuang5, Wu Weitao1,2, Bai Yubin1,2, Deng Xiuqin3,4, Sun Bo3,4   

  1. 1. School of Earth Sciences and Engineering, Xi'an Shiyou University, Xi'an, Shaanxi 710065, China;
    2. Shaanxi Key Lab of Petroleum Accumulation Geology, Xi'an, Shaanxi 710065, China;
    3. Research Institute of Petroleum Exploration and Deuelopment, PetroChina Changging Oilfield Company, Xi'an, Shaanxi 710018, China;
    4. National Engineering Laboratory for Exploration and Development of Low-Permeability Oil & Gas Fields, Xi'an, Shaanxi 710018, China;
    5. No.3 Gas Production Plant, PetroChina Changqing Oilfield Company, Xi'an, Shaanxi 710018, China
  • Received:2015-12-10 Revised:2016-04-20 Online:2016-06-08 Published:2016-06-22

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50 nm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2 μm以上,孔喉半径多集中在73.5 nm以下,但对渗透率起贡献作用的孔喉半径区间为73.5~735 nm,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-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-微米级孔隙-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-微裂缝-裂缝孔喉网络系统,构成源内石油向源外运移的路径。

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

Abstract: 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 utilizing methods including core description,field emission scanning electronic microscope,laser scanning confocal microscopy,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 sandstone contains residual primary intergranular pores,inter-crystals pores and secondary pores (the major type).Pore size is mostly larger than 2 μm and pore-throat size is less than 73.5 nm.However,pore-throats that contribute the most to improving 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 controlled 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:①nonameter-micrometer pores- fracture networks in organic-rich shale (acting as storage space and migration pathway within source rocks);②nanometer pore throat-micrometer pores-fracture networks in tight sandstones (acting as storage space of tight oil);③differential pore throat structure-microfracture-fracture networks between shale and tight sandstone(acting as migration pathway for oil from source rocks to outside reservoirs).

Key words: pore, pore-fracture network, shale, tight sandstone, Yanchang Formation, Ordos Basin

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