基于全方位地下局部角度域成像的页岩气储层各向异性预测

Full azimuth subsurface local angle domain imaging based anisotropy characterization for shale gas reservoir

宽方位地震数据是叠前地震各向异性预测的基础数据之一,如何处理和分析宽方位地震数据是预测的关键.传统分扇区处理无法获得地下真正角度域信息,存在信息丢失问题.为保证地下方向、分辨率以及成像的正确性,使用全方位地下局部角度域分解与成像技术,直接在地下局部角度域中以连续的方式进行地震数据成像分解,得到两个互补的全方位角度道集:倾角道集和反射角道集,成像精度提高,各向异性发育方向和强度预测更可靠.全方位成像与反演一体化技术流程在四川盆地涪陵页岩气储层表征中初步应用,为提高非均匀储层成像质量和裂缝预测精度提供有效手段,对于页岩气储层甜点预测、水平井钻井轨迹和压裂方案优化等具有重要意义.

Wide azimuthal seismic data acquisition is the basis of anisotropy characterization. Furthermore, the data processing and analyzing procedure are critical to ensure good results. Nowadays, the popular processing procedure for wide azimuthal seismic data is sectoring. However, sectoring processing could not get the real subsurface angel information and would leak geological information because of its intrinsic defects. Using a new local angle domain imaging method in the paper, two type angle gathers can be generated： directional angle gathers and reflection angle gathers, which can make the subsurface imaging correctly with valid direction and resolution. On base of the full azimuth local angle domain decomposition and imaging, anisotropy orientation and intensity can be characterized better by residual, move-outs （RMO） and amplitude versus angle with azimuth （AVAZ）. The integrated full azimuthal imaging and inversion work flow is applied to shale gas reservoir anisotropy characterization of Fu-ling acreage in Sichuan basin and effective results are obtained. The predicted anisotropy orientation and intensity properties would be beneficial to identifying ＂sweet spot＂, the horizontal well deployment and hydraulic fracturing option.