基于walkaround VSP的裂缝检测方法及应用  

Fracture detection method based on walkaround VSP and its application

作　　者：陈占国[1] 陈林[1] 张卫红[1] 

机构地区：[1]中国石油化工股份有限公司石油物探技术研究院,江苏南京211103

出　　处：《石油物探》2015年第6期745-754,共10页Geophysical Prospecting For Petroleum

基　　金：国家科技重大专项项目"煤层气井中地球物理勘探技术研究"(2011ZX05035003)资助

摘　　要：研究油气储层裂缝发育情况是降低油气勘探风险,有效开发油气资源的重要任务之一。研究了利用walkaround VSP资料下行qP波的振幅、速度和极性方位各向异性特征分析裂缝参数的方法和流程。其中通过反褶积和伪透射系数(pseudo transmission coefficient,PTC)处理消除了上覆地层对振幅的影响;通过计算与各向异性有关的局部速度避开炮点高程和偏移距及上覆地层对旅行时的影响;提出的相对极化角方法校正了偏振极性受炮点位置的影响;最后通过最小二乘椭圆拟合方法分析了qP波的振幅、速度和偏振极性随方位的变化特征,统计了储层的裂缝走向和发育情况。应用结果表明,3种属性分析的结果吻合度较高,且和横波分裂方法的分析结果一致,从而证明该方法可靠性较高,是一种通过walkaround VSP预测裂缝的有效方法。Research on the development of reservoir fractures is to reduce exploration risk and effectively develop hydrocarbon reservoirs. The analysis method and workflow on fracture parameters are studied by using the amplitude, velocity and polarity azimuthal anisotropy of down-going qP wave from walkaround VSP data. The impact of overlaying formations on the ampli- tude is removed by deconvolution and pseudo-transmission coefficient （PTC） processing. The impact of shot point elevation, o{fset and overlaying formations on travelling-time is avoided by calculating local velocity related with anisotropy. The impact of shot position on the polarization of polarity is corrected by the proposed relative polarization angle method. Finally, we ana- lyze the variation characteristics of the amplitude,vdocity and polarity azimuthal anisotropy of clown-going qP wave via azi- muth by least square ellipse fitting method. Moreover, the statistics of fracture strike and development in reservoirs is carried out. The application indicates that the analysis results of the attributes match with each other and are consistent with the re- suits obtained from S-wave splitting method, which proves the higher reliability of the method and is effective for fracture prediction by walkaround VSP data.

关 键 词：walkaround VSP裂缝 各向异性 振幅 速度 极性 

分 类 号：P631[天文地球—地质矿产勘探]