地震裂缝综合预测技术在川西致密砂岩储层中的应用

APPLICATION OF INTEGRATED SEISMIC FRACTURE DETECTION TECHNOLOGY IN TIGHT SAND RESERVOIRS IN THE WESTERN SICHUAN BASIN

川西BMM地区侏罗系沙溪庙组储层为河流相低孔低渗致密砂岩,裂缝控制了储层的储渗空间和井的产能。针对研究区为窄方位三维P波地震数据,直接用于地震裂缝检测存在的不足,提出了解决这一问题的实用处理方法。在各向异性理论和实际井资料合成的方位AVO理论记录指导下,从三维方位数据体中提取地震波反射振幅、速度和高频衰减参数,并利用其方位变化特征来预测裂缝各向异性。为了消除岩性横向变化对裂缝检测的不利影响,减少多解性,从沉积相分析入手,描述河流的空间分布,利用砂岩和泥岩伽马值的差异,通过反演技术,建立砂岩储层的空间分布模式,然后进一步估计砂体的裂缝发育情况以及含流体性。预测效果获得了新钻井的验证,取得了很好的经济效益。

The reservoirs of Jurassic Shaximiao Formation in BMM area of the western Sichuan Basin are tight channel sand with low permeability and low porosity.The reservoir space and well deliverability are controlled by fractures.In view of the problems occurred when directly using narrow azimuthal 3D P-wave to detect fractures in the study area, a practical method is presented to solve these problems.Under the guidance of anisotropic theory and azimuthal AVO composite seismogram from real well data,seismic attribute parameters such as amplitude,velocity and high frequency attenuation are extracted from the 3D data cube,and their azimuthal variations are used to predict the anisotropy of fractures.In order to eliminate the influences caused by lateral lithologic variation on fracture detection and to alleviate ambiguity of interpretation,the spatial distribution of the channels are delineated according to sedimentary facies,and the spatial distribution pattern of the sandstone reservoirs are determined with inversion technology based on gamma ray contrast between sandstone and shale.Fracture development and fluid saturations of the sandstones are further estimated.The prediction results are verified in the newly drilled wells and remarkable economic benefits have been achieved.