致密储层水平井外裂缝与地层界面远探测声波测井响应特征研究  

Response characteristics of acoustic reflection imaging logging of fractures and formation interfaces outside horizontal wells in tight reservoirs

作　　者：张梦生 刘鹏 范华军[1] 李振[3] 赵浩 姜京伟 冯周[2] 王克文[2] 李雨生 武宏亮[2] ZHANG MengSheng;LIU Peng;FAN HuaJun;LI Zhen;ZHAO Hao;JIANG JingWei;FENG Zhou;WANG KeWen;LI YuSheng;WU HongLiang(National Key Laboratory of Petroleum Resources and Engineering,China University of Petroleum(Beijing),Beijing 102249,China;PetroChina Research Institute of Petroleum Exploration and Development,Beijing 100083,China;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu 610059,China)

机构地区：[1]中国石油大学(北京)油气资源与工程全国重点实验室,北京102249 [2]中国石油勘探开发研究院,北京100083 [3]成都理工大学油气藏地质及开发工程全国重点实验室,成都610059

出　　处：《地球物理学报》2024年第6期2439-2454,共16页Chinese Journal of Geophysics

基　　金：中国石油天然气集团有限公司科学研究与技术开发项目"高精度深探测成像测井系列处理技术研究"(2021DJ4002);"斯通利波测井探测器及刻度关键技术研究"(2022DJ3908)资助。

摘　　要：致密砂岩和页岩等非常规储层中常发育有密集小尺度和高角度裂缝.这些裂缝一方面起到增加储层渗透性的积极作用,另一方面在油气开采、水力压裂、注二氧化碳等过程中,它们又可能引起水平井孔套变和邻井压窜等风险.因此,考察这些裂缝的水平井远探测声波测井响应特征,以及进一步利用远探测方法识别这些裂缝具有重要研究意义.本文构建了致密储层水平井外存在裂缝的三维数值模型,并开展了正演模拟研究.结果表明,当裂缝与井孔夹角较小时,井孔内接收器主要接收裂缝反射波.当夹角大于某临界值后,接收波形主要为来自裂缝两个端点的散射波,它们分裂为两个波包.进一步提出广义SH散射波概念,即声源的偏振方向与裂缝走向平行的横波,它总是代表了所有方位上散射能量最强的方位.水平井外同时存在裂缝和强声阻抗地层界面是更为普遍的情况.相关模拟结果表明,裂缝散射波的主要能量集中在广义SH散射波上.随着地层界面和裂缝走向差异的增大,裂缝对应的广义SH散射波更容易识别.最后,通过一口水平井远探测实例验证了正演模拟结论的准确性.本文研究对识别和评价非常规储层水平井外小尺度裂缝具有重要理论意义.Dense small-sized and high-angle fractures are commonly developed in unconventional reservoirs,such as tight sandstone and shale reservoirs.These fractures play a positive role in increasing the permeability of the reservoir,but also play a negative role in causing horizontal casing deformation and inter-well frac-hit during oil and gas production,hydraulic fracturing,CO2 injection,etc.Therefore,it is of great significance to investigate the response characteristics of horizontal well acoustic reflection imaging logging for these fractures,and further identify these fractures using reflection imaging methods.This paper establishes a three-dimensional numerical model of fractures outside the horizontal well of a tight reservoir,and the forward modeling is carried out.The results indicate that when the angle between the fracture and the borehole is small,the received waveform in the borehole is mainly the fracture reflected wave.When the angle exceeds a certain critical value,the received waveform is mainly the scattered waves from the two endpoints of the fracture.And the scattered waves split into two wave packets.The concept of generalized scattered SH wave is proposed,which is a transverse wave with source polarization direction parallel to the fracture strike.It represents the direction where the scattered wave has the strongest energy.The presence of fractures and strong acoustic impedance formation interfaces outside horizontal wells is a more common situation.The simulation results indicate that,the main energy of the fracture scattered wave is concentrated on the generalized scattered SH wave.As the differences between the formation interface and the strike of fractures increase,the generalized scattered SH wave corresponding to the fractures are easier to identify.Finally,the accuracy of the forward simulation was verified through a reflection imaging example of a horizontal well.This study has important theoretical significance for identifying and evaluating small-scale fractures outside horizontal wells

关 键 词：水平井 远探测声波测井 裂缝 地层界面 散射波 广义SH散射波 

分 类 号：P631[天文地球—地质矿产勘探]