基于多方位非零偏三分量VSP的储层裂缝检测

Reservoir fracture detection based on multi-azimuth 3C non-zero offset VSP

非零偏三分量VSP记录中普遍存在着由下行纵波转换而来的下行横波,它们携带着所经过地层的裂缝信息,可以用来检测储层裂缝。针对多个裂缝系统同时存在的情况,在横波分裂理论和前人研究的基础上提出了基于多方位非零偏三分量VSP资料研究储层裂缝的方法。该方法分为3个步骤:一是通过水平旋转、垂直旋转和上、下行波波场分离等预处理,获得研究裂缝所需的高质量下行横波;二是进行横波分裂处理,获得独立的快、慢横波记录和初步的裂缝发育方位;三是对快、慢横波记录进行可靠性分析,剔除不合理数据,最终获得裂缝发育方位和快、慢横波时差,评估裂缝密度。辽河油田HW潜山构造带HG-2井多方位三分量VSP资料储层裂缝检测结果与成像测井结果总体上一致,且与井旁构造有着合理的对应关系,验证了该方法的可靠性。

There is plenty of down-going S-wave converted from down-going P-wave in the records of 3C non-zero offset VSP,which carries the fracture information of the formations passed by and can be used for fracture detection.In the present case of fracture systems coexistence,based on the S-wave splitting theory and the previous research result,we proposed reservoir fracture prediction method based on multi-azimuth non-zero offset 3C VSP data.Firstly,horizontal rotation,vertical rotation,up-going & down-going wavefield separation,and such kind of preprocessing was carried out to obtain high-quality down-going S-wave for fracture detection.Secondly,S-wave splitting was proceeded to achieve the seismic record of fast S-wave and slow S-wave as well as primary fracture development azimuth.Thirdly,reliability of fast & slow S-wave moveout was analyzed and the unreasonable data was rejected.After the above three steps,the fracture development azimuth and fast & slow S-wave moveout were identified,and the fracture density was evaluated.The method was applied to the multi-azimuth 3C VSP data of well HG-2 at HW buried hill structural belt in Liaohe Oilfield.The application result is basically coinciding with imaging logging data and has reasonable corresponding relationship with wellside structure,which proved the reliability of the method.