深埋海相页岩储层特性及其原位条件下脆性评价  

CHARACTERISTICS AND BRITTLENESS EVALUATION OF THE DEEP-MARINE SHALE UNDER IN SITU CONDITIONS

作　　者：曾波[1] 宋毅[1] 杨子叶 黄浩勇 姚志广 岳文翰 桂俊川 徐尔斯 赫建明[3,4] ZENG Bo;SONG Yi;YANG Ziye;HUANG Haoyong;YAO Zhiguang;YUE Wenhan;GUI Junchuan;XU Ersi;HE Jianming(Shale Gas Research Institute,PetroChina Southwest Oil&Gasfield Company,Chengdu 610051,China;PetroChina Southwest Oil&Gasfield Company,Chengdu 610051,China;Key Laboratory of Shale Gas and Geo-engineering,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国石油西南油气田分公司页岩气研究院,成都610051 [2]中国石油西南油气田分公司,成都610051 [3]中国科学院地质与地球物理研究所,中国科学院页岩气与地质工程重点实验室,北京100029 [4]中国科学院大学地球与行星科学学院,北京100049

出　　处：《工程地质学报》2022年第3期956-965,共10页Journal of Engineering Geology

基　　金：中国石油天然气集团有限公司重大现场试验项目“深层页岩气有效开采关键技术攻关与试验-深层页岩气体积压裂技术现场试验”(资助号:2019F-31);中国石油天然气股份有限公司重大专项“西南页岩气体积改造技术提升攻关与现场试验”(资助号:2021CGCGZ005)。

摘　　要：储层压裂改造是非常规能源开发的关键核心技术,近年来我国川西南页岩气区块储层埋深已经突破了4000 m,部分储层埋深已经接近5000 m的深度范畴,这些深埋海相页岩储层的开发与3500 m以浅区相比差异较大,其独有特性对于储层改造工程形成挑战。储层压裂改造中起到控制性作用的是储层岩石的物理力学特性,岩石脆性是其中之关键指标。国内外学者提出多个岩石脆性指标评价方法,矿物成分、力学性质、应力-应变曲线特征、硬度测试以及能量理论等等,但是对于深埋储层岩石在原位条件下的脆性评价,则由于实现难度较大而鲜见相关成果。在实验室模拟储层温压条件下在原位钻取岩石样品实施三轴压缩力学试验获得全应力-应变曲线,其峰前与峰后的应力-应变信息有效反映了原位条件下储层岩石的峰值破坏前后的内在材料属性以及变形破坏过程,通过获取多个储层岩芯峰前以及峰后的弹模计算获得脆性指数K_(1)和K_(2),其值能够反映应力-应变后的弹性变形能量、峰后破裂能量以及冗余能量的关系,该脆性指数的最显著特点是能够反映出深埋页岩储层在原位条件下的温度和压力条件下的材料行为属性,从而能够对深埋海相页岩储层进行原位条件下的脆性评价。本文基于对我国龙马溪页岩储层中龙一层位中1~4小层及其下伏五峰组的页岩原位条件下的脆性评价,对比实际压裂工程现场压裂产气效果讨论了原位条件下的脆性评价的重要性。Hydraulic fracturing is the key technology in the exploitation of unconventional resources,such as shale gas.Depth of the shale reservoir in the southwestern area of Sichuan Basin has breached 4000 m and some blocks even are approaching 5000 m.There are great differences in the exploitation of such reservoirs due to the challenge in situ conditions in the deep subsurface.Brittleness of the reservoir rock under the in situ conditions plays very important role in the hydraulic fracturing of the reservoir.Shale samples were collected from the borehole and in situ conditions were recorded on the drilling site.The standard rock specimens were prepared,having a height to diameter ratio of 2.0 and a diameter of 50 mm.Triaxial compression experiments under in situ conditions were carried out in the laboratory to obtain the complete stress-strain curves.Brittleness index based on the complete stress-strain curves under in situ conditions were used here for the evaluation of brittleness of the reservoir rocks.Brittleness of four sub-layers of the Longmaxi shale and underlying Wufeng shale were estimated using the brittleness index under in-situ conditions.Results of the brittleness values of the reservoir rocks were studied and the comparison with the fracturing results of the real reservoirs is carried out.The results of brittleness evaluation under in situ conditions agree well with the fracturing operation on the drilling site.

关 键 词：深层海相页岩 储层特性 原位脆性 全应力-应变曲线 

分 类 号：TE122[石油与天然气工程—油气勘探]