石油与天然气地质 ›› 2022, Vol. 43 ›› Issue (5): 1087-1101.doi: 10.11743/ogg20220507

• 油气地质 • 上一篇    下一篇

川南地区下古生界五峰组-龙马溪组含气页岩岩心裂缝特征及其页岩气意义

施振生1(), 赵圣贤2, 赵群1, 孙莎莎1(), 周天琪1, 程峰1, 施少军3, 武瑾1   

  1. 1.中国石油 勘探开发研究院, 北京 100083
    2.中国石油 西南油气田分公司 页岩气研究院, 四川 成都 610051
    3.中国石油 吉林油田分公司勘探开发研究院, 吉林 松原 138000
  • 收稿日期:2022-03-10 修回日期:2022-07-19 出版日期:2022-10-01 发布日期:2022-09-02
  • 通讯作者: 孙莎莎 E-mail:shizs69@petrochina.com.cn;sunss69@petrochina.com.cn
  • 第一作者简介:施振生(1976—),男,博士、高级工程师,细粒储层地质学。E?mail: shizs69@petrochina.com.cn
  • 基金项目:
    中国石油“十四五”科技重大专项(2021DJ1901);国家科技重大专项(2017ZX05035-001)

Fractures in cores from the Lower Paleozoic Wufeng-Longmaxi shale in southern Sichuan Basin and their implications for shale gas exploration

Zhensheng Shi1(), Shengxian Zhao2, Qun Zhao1, Shasha Sun1(), Tianqi Zhou1, Feng Cheng1, Shaojun Shi3, Jin Wu1   

  1. 1.Research Institute of Petroleum Exploration and Development,PetroChina,Beijing 100083,China
    2.Research Institute of Petroleum Exploration and Development,Southwest Oil & Gas Field Company,PetroChina,Chengdu,Sichuan 610051,China
    3.Exploration and Development Research Institute of Jilin Oilfield Company,PetroChina,Songyuan,Jilin 138000,China
  • Received:2022-03-10 Revised:2022-07-19 Online:2022-10-01 Published:2022-09-02
  • Contact: Shasha Sun E-mail:shizs69@petrochina.com.cn;sunss69@petrochina.com.cn

摘要:

裂缝直接影响页岩储层特性和页岩气井单井测试产量。通过岩心和露头宏观裂缝描述、偏光显微镜和场发射扫描电镜微裂缝观察发现,川南地区五峰组-龙马溪组含气页岩宏观裂缝和微裂缝发育,可划分为顺层缝和非顺层缝。宏观裂缝中,顺层缝主要为页理缝和层间滑移缝,非顺层缝主要为斜交缝和垂直缝。微裂缝中,顺层缝主要为页理缝,非顺层主要为生烃增压缝、成岩收缩缝和溶蚀缝。含气页岩的裂缝以顺层缝为主,75 %的宏观裂缝和87 %的微裂缝均为顺层缝。裂缝密度和分布受埋深控制,埋深大于3 500 m地区裂缝集中发育于龙一1(1-3)小层,而埋深小于3 500 m地区裂缝集中发育于龙一1(1)小层。且随着埋深增加,宏观裂缝和微裂缝的密度均增大,部分井中埋深大于3 500 m含气页岩井宏观裂缝密度是其他埋深小于3 500 m同层含气页岩的10倍。页岩有机碳含量和层理类型也影响含气页岩的裂缝密度,高总有机碳含量的条带状粉砂型和砂-泥递变型水平层理页岩裂缝密度最大。裂缝发育有利于优质页岩段形成,埋深小于3 500 m地区优质页岩段主要发育于龙一1(1)小层;埋深大于3 500 m地区优质页岩段发育于龙一1(1-3)小层,部分井龙一2亚段底部由于成岩收缩缝发育,也成为优质页岩段。

关键词: 微裂缝, 宏观裂缝, 含气页岩, 五峰组, 龙马溪组, 四川盆地

Abstract:

Fractures are closely linked to the reservoir capacity of shale intervals, therefore also have a direct control over the test results of wells drilled into the intervals. A macro delineation based on cores and outcrops observation are combined with polarized microscopic and scanning electron microscopic images of samples to reveal the characteristics of fractures in the gas-bearing shale intervals of the Wufeng-Longmaxi Formations, southern Sichuan Basin. It shows that the shale intervals have highly-developed bedding-parallel and non-bedding-parallel macro and micro fractures, of which the bedding-parallel fractures take dominance and account for 75 % of the total macro fractures and 87 % of the total micro fractures. For macro fractures, the bedding-parallel fractures are generally foliation fractures and inter-layer sliding fractures, and the non-bedding-parallel fractures are oblique and vertical. For micro fractures, the bedding-parallel fractures are dominated by foliation fractures, while the non-bedding-parallel fractures are mostly fractures caused by abnormal pressure from hydrocarbon generation, diagenetic contraction fractures, and dissolution fractures. The density and distribution of the fractures are largely controlled by burial depth with the 3 500 m serving as a dividing line. For intervals below the line, fractures are mostly developed in the L1(1-3) layer; for intervals above the line, fractures are concentrated in the L1(1) layer. Density of both macro and micro fractures increases with increasing burial depth. There are wells showing that density of macro fractures in shale intervals below the line is ten times higher than those above the line. The fracture density is also controlled by TOC content and bedding types, which is well illustrated by shale intervals with high TOC content and bedding of striped siltstone type and graded (siltstone to claystone) type also having the highest fracture density. As fractures are essential to the reservoir capacity of shale intervals, the L1(1-3) and L1(1) layers contain the best quality shale intervals. However, with diagenetic contraction micro-fractures well developed, the bottom of the L1(2) also hosts some quality shale intervals.

Key words: micro-fracture, macro fracture, gas-bearing shale, Wufeng Formation, Longmaxi Formation, Sichuan Basin

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