组合静校正解决方案及在页岩气地震勘探中的应用

Combined static correction solution and its application in shale gas seismic exploration

山地、丘陵等复杂地区的高程变化大,地表出露岩性复杂,风化层厚度不均匀、表层速度在空间上亦有明显差异,高速层底界厚度变化剧烈、深度不稳定,导致地震资料存在严重的静校正问题,引起反射同相轴畸变.常规方法处理后的最终成像结果上,同相轴的横向展布不能准确与实际地层相对应,这在页岩气勘探开发中问题尤为严重.因为页岩气勘探开发主要以水平井为主,水平段大多在1000~2000 m,而有效页岩厚度在10~30 m左右,由静校正问题引起的目标层位成像不准是首先需要解决的问题.为此,本文采用表层模型约束首波法三维层析静校正+基于时窗迭代的最大能量地表一致性剩余静校正+基于目标层的沿层最大相关剩余静校正技术方案,比较好地解决了复杂山地地表不同岩性引起的静校正问题,文中详细说明了上述方法的基本原理,处理步骤、关键参数组合方案及相互影响等,并展示了组合静校正技术在南方山地页岩气地震勘探中的应用效果,钻井已证实本文方法的有效性,用该结果预测的井轨迹与实际钻井位置的误差很小,完全保证水平井在顶、底板之间穿行,大大提高了钻井工程的成功率.

In complex areas such as mountains and hills,due to the large elevation changes,the surface covering soil layer or limestone is exposed,which causes uneven thickness of the weathering layer and large lateral varies of the surface velocity.In addittion,the thickness of high-velocity layer bottom boundary changes drastically and the depth is unstable.The above surface factors have serious impacts on the acquisition of field seismic data,and the obtained seismic data have serious static correction problems,which cause distortion of the reflection events.As a result,the lateral distribution of the events cannot be accurately matched with the actual formations in the final result by applying the conventional processing procedure.Correspondingly,this is a particularly serious problem in the exploration and development of shale gas.Because the exploration and development of shale gas is mainly based on horizontal wells,the horizontal section is mostly 1000~2000 m,and the effective shale thickness is about 10~30 m.The inaccurate imaging of the target horizon caused by it is the first problem to be solved.For this reason,this paper proposes to use the constrained tomography static correction+maximum energy residual static correction+inter-layer residual static correction technical solution to better solve the static correction problem caused by different lithologies in complex mountainous areas.The paper states the basic principles,key parameters and their inter-relationships,processing flow in detail.Well drilling approved that the predictive position of horizontal well is matched to exact drilling with a little errors,which guarantees the bit can drill on roof and floor stably and more precisely.The practical application to shale gas in south china has achieved good results.