石油与天然气地质 ›› 2018, Vol. 39 ›› Issue (3): 472-484.doi: 10.11743/ogg20180305

• 油气勘探 • 上一篇    下一篇

焦石坝区块五峰组与龙马溪组一段页岩有机孔隙结构差异性

何陈诚1, 何生1, 郭旭升2, 易积正3, 魏志红2, 舒志国3, 彭女佳1   

  1. 1. 中国地质大学(武汉) 构造与油气资源教育部重点实验室, 湖北 武汉 430074;
    2. 中国石化 勘探分公司, 四川 成都 610041;
    3. 中国石化 江汉油田分公司, 湖北 潜江 433124
  • 收稿日期:2017-11-15 修回日期:2018-04-11 出版日期:2018-06-28 发布日期:2018-06-21
  • 通讯作者: 何生(1956-),男,教授、博士生导师,油气地质。E-mail:shenghe@cug.edu.cn。 E-mail:shenghe@cug.edu.cn
  • 作者简介:何陈诚(1990-),女,博士研究生,非常规页岩气地质。E-mail:hechencheng@cug.edu.cn。
  • 基金资助:
    国家自然科学基金项目(41672139,41690134);国家“十三五”油气重大专项(2016ZX05034002-003,2017ZX05005001-008);中央高校基本科研业务费专项资金资助项目(CUGQYZX1707);高等学校学科创新引智计划资助项目(B14031)。

Structural differences in organic pores between shales of the Wufeng Formation and of the Longmaxi Formation's first Member,Jiaoshiba Block,Sichuan Basin

He Chencheng1, He Sheng1, Guo Xusheng2, Yi Jizheng3, Wei Zhihong2, Shu Zhiguo3, Peng Nyujia1   

  1. 1. Key Laboratory of Tectonics and Petroleum Resources Ministry of Education, China University of Geosciences (Wuhan), Wuhan, Hubei 430074, China;
    2. Exploration Company, SINOPEC, Chengdu, Sichuan 610041, China;
    3. Jianghan Oilfield Company, SINOPEC, Qianjiang, Hubei 433124, China
  • Received:2017-11-15 Revised:2018-04-11 Online:2018-06-28 Published:2018-06-21

摘要: 焦石坝区块五峰组和龙马溪组一段海相富有机质页岩中纳米有机孔隙十分发育,有机孔隙成为该页岩气储层的重要储集空间。应用场发射扫描电镜(FE-SEM)和ImageJ统计软件以及气体吸附测试,对五峰组和龙马溪组一段下部和上部3套页岩的20块样品有机孔隙结构(孔隙形状、数量、孔径分布)进行了观察和参数统计分析,并对有机质面孔率进行了计算。根据利用FE-SEM观察到的孔径分布在2~900 nm,主要在10~900 nm的有机孔隙特征发现五峰组、龙马溪组一段下部和上部页岩的纳米有机孔隙结构存在明显的差异性。五峰组页岩有机孔隙形状多为不规则棱角形,而龙马溪组一段页岩有机孔隙形状多呈椭圆形和近圆形。五峰组页岩样品孔径在10~50 nm有机孔隙相对最发育,其次是龙马溪组一段上部;而龙马溪组一段下部页岩样品孔径在50~900 nm的有机孔隙相对最发育,其次是龙马溪组一段上部。根据孔径主要在10~900 nm的6 1400余个有机孔隙的统计结果,页岩样品平均单颗粒有机质面孔率与有机碳含量(TOC)有粗略的正相关性,但五峰组页岩样品平均有机质面孔率相对略偏小。根据气体吸附孔径测定及分析,页岩样品中孔径在0.3~1.5 nm和2~10 nm范围的纳米孔隙发育程度与TOC具有明显的正相关性。焦石坝区块五峰组、龙马溪组一段下部和上部页岩有机碳含量的差异性、五峰组页岩处于挤压滑脱层底部且经历了更明显的分层滑脱改造以及改造引起的部分超压释放,可能是3个层位页岩有机孔隙结构差异性的原因。

关键词: 有机孔隙, 结构差异性, 面孔率, 页岩气, 五峰组, 龙马溪组, 焦石坝区块, 四川盆地

Abstract: Nanoscale organic pores are the dominant pores in the marine organic-rich shales of the Wufeng Fomration and the Longmaxi Formation's first Member in the Jiaoshiba Block,Sichuan Basin,which provide important reservoir space for shale gas.In this study,a combination of field emission scanning electron microscopy(FE-SEM),statistical analysis based on ImageJ software and gas adsorption test,was conducted to investigate structural characteristics of organic pores,such as pore shape,pore quantity,pore-size distribution.The surface pore rate of organic matter(OM)was calculated,based on 20 sample rocks from the three sets of shales in the Wufeng Formation and the lower and upper Longmaxi Formation's first Member.FE-SEM images show that the pore sizes are within a range of 2-900 nm,and significant variations exist for the nanoscale organic pore structures with the sizes of 10-900 nm among the chosen shale samples.Most of the organic pores in the Wufeng Formation shales are irregular polygons in shape,while elliptical and sub-rounded organic pores are observed in the Longmaxi's first Member.Organic pores with width of 10-50 nm are most popular in the Wufeng Formation shale samples,followed by the upper part of the first Member of the Longmaxi Formation,while the lower part of the first Member of the Longmaxi Formation mostly develop organic pores with the width of 50-900 nm,with the upper part of the Member ranked the second.Based on the statistic results over 61 400 organic pores with the size ranging from 10 nm to 900 nm in the shale samples,we observe that the average surface pore rate of OM for a single grain has a weak positive correlation with the total organic carbon(TOC)content,but the average surface pore rate of OM in the sample shales of the Wufeng Formation is relatively smaller than that in the Longmaxi Formation.The gas adsorption test and pore size measurement show that a good positive correlation between TOC content and nanometer pores with pore-sizes of 0.3-1.5 nm and 2-10 nm exists.Thus we may conclude that the structural differences of organic pores in the sampled shales are derived from the TOC content variation and the special location of the Wufeng Formation,the shales of which are located at the bottom of compressive decollement formations and had experienced layered decollement reconstruction which in turn results in partial gas release under overpressure.

Key words: organic pore, structure difference, surface pore rate, shale gas, Wufeng Formation, Longmaxi Formation, Jiaoshiba Block, Sichun Basin

中图分类号: