沧东凹陷孔二段页岩中基于岩心裂缝观测的构造裂缝规模解析  

Mathematical analysis of structural fracture scale in shale based on core fracture observation of the second member of Kongdian Formation in Cangdong Sag

作　　者：马存飞 孙文静 曾令鹏 韩文中[2] 詹远 杜争利 时战楠 MA Cunfei;SUN Wenjing;ZENG Lingpeng;HAN Wenzhong;ZHAN Yuan;DU Zhengli;SHI Zhannan(School of Geosciences in China University of Petroleum(East China),Qingdao 266580,China;Dagang Oilfield Company,PetroChina,Tianjin 300280,China;Tarim Oilfield Company,PetroChina,Korla 841000,China)

机构地区：[1]中国石油大学(华东)地球科学与技术学院,山东青岛266580 [2]中国石油大港油田分公司,天津300280 [3]中国石油塔里木油田分公司,新疆库尔勒841000

出　　处：《中国石油大学学报（自然科学版）》2023年第4期1-11,共11页Journal of China University of Petroleum(Edition of Natural Science)

基　　金：国家自然科学基金项目(42172153,41802172,41830431)。

摘　　要：以沧东凹陷孔二段页岩中的构造裂缝为研究对象,重点利用岩心资料,采用岩心观测、数学解析和软件拟合等研究手段,开展裂缝类型识别、构造裂缝规模计算及其影响因素分析等研究工作。根据孔二段页岩岩心上构造裂缝实测数据,采用基于最小二乘法的椭圆拟合方法建立代表性构造裂缝纵剖面和平剖面的椭圆标准方程,获得裂缝椭球中轴和短轴,进而根据三角形相似原理计算裂缝椭球长轴,由此建立代表性构造裂缝的椭球标准方程。岩心上其他构造裂缝规模与代表性构造裂缝规模进行类比计算。结果表明:孔二段页岩中裂缝类型包括构造裂缝和非构造裂缝,其中构造裂缝包括张裂缝和剪裂缝;建立的椭球标准方程反映其规模处于米级别,其水平延伸长度介于0.13~4.55 m,平均值为1.15 m,纵向延伸长度为0.20 m,开度为0.58 mm;而非构造裂缝包括层理缝、层面缝、白云岩化缝和泄水缝。孔二段页岩中构造裂缝规模影响因素包括断层、岩性、层厚和埋深,其中断层控制了构造裂缝的产状,且随着距断层距离的增加,构造裂缝的平均水平延伸长度减小;富含碳酸盐矿物或长英质矿物的页岩岩性脆性强,构造裂缝更容易产生和扩展,因而灰云质页岩中构造裂缝的平均水平延伸长度最大,其次是长英质页岩;当页岩岩性一定时,构造裂缝的平均水平延伸长度随着层厚的增加而增大,两者具有良好的正相关关系;当页岩埋深增大时,围岩压力增大,裂缝难以产生和扩展,构造裂缝的平均水平延伸长度有减小的趋势。This paper focuses on the investigation of structural fractures in the shale core of the second member of Kongdong sag.Through core observation,mathematical analysis,and software fitting,the research includes fracture type identification,structural fracture scale calculation and analysis of influencing factors.Using measured data of structural fractures on the shale core,ellipse standard equations of longitudinal section and horizontal section of representative structural fractures are established using the ellipse fitting method based on the least square method.By calculating the major axis of the fracture ellipsoid using the principle of triangle similarity,the ellipsoid standard equation for representative structural fractures is obtained.Comparison of other structural fractures on the core with the representative structural fracture reveals that the shale of the second member of Kongdian Formation consists of structural fractures and non-structural fractures.Structural fractures include tensile fractures and shear fractures.The established ellipsoid standard equation reflects that their scale is in the meter range,their horizontal extension length is between 0.13-4.55 m with an average of 1.15 m,their longitudinal extension length is 0.20 m and opening is 0.58 mm.Non-structural fractures include bedding fractures,bedding plane fractures,dolomitization fractures,and drainage fractures.The influencing factors on the scale of structural fractures include faults,lithology,layer thickness and buried depth.Faults control the occurrence of structural fractures,with a decrease in the average horizontal extension length as the distance from the fault increases.Shale with a higher content of carbonate minerals or felsic minerals tends to be more brittle,resulting in easier generation and expansion of structural fractures Thus calcareous or dolomitic shale exhibits the largest average horizontal extension,followed by felsic shale.When the shale lithology remains constant,the average horizontal extension length of struct

关 键 词：裂缝数学解析模型 裂缝长度 影响因素 孔二段页岩 沧东凹陷 

分 类 号：TE122[石油与天然气工程—油气勘探]