分频融合技术在致密砂岩储层预测中的应用——以川东北通南巴背斜侏罗系为例

Application of spectral decomposition and fusion technology in predicting of tight sandstone reservoirs:A case of Jurassic strata of Tongnanba anticline in northeastern Sichuan

为解决因波阻抗差异小导致的致密砂岩储层预测困难的问题,提出基于分频融合技术的河道刻画与储层“甜点”预测方法。该方法将目标砂体与地震频谱建立非线性映射关系,形成具有通频信息的混频数据体,并建立具有宏观地质意义的相控模型,进而开展高分辨率反演确定致密砂岩储层“甜点”分布。以通南巴背斜侏罗系千一段致密砂岩为研究对象,应用分频融合技术高精度刻画千一段沉积早期的河道分布。基于混频数据体的高分辨率反演结果表明,研究区千一段河道砂体孔隙度小于6%,背斜处孔隙度较高(4%~6%)。河道内砂体横向分布稳定,其中脆性砂体(自然伽马小于65 API)厚度变化较快,背斜处脆性砂体厚度一般大于20 m。储层预测结果显示千一段背斜带河道砂体具有厚度大、脆性好、孔隙度高、埋藏浅的特点,是千一段“甜点”发育区,也是未来致密储层改造的有利靶区。

In order to solve the difficult problem of tight sandstone reservoir prediction due to the small difference of wave impedance,this paper presents a prediction method for channel characterization and“sweet spot”based on the spectral de⁃composition and fusion technology.In this method,the nonlinear mapping relationship between the target sand body and the seismic spectrum was established to form a mixed data volume with direct frequency information,and a facies control model of macroscopic geological significance was constructed.In this way,the high-resolution inversion was performed to determine the distribution of“sweet spots”in tight sandstone reservoirs.By taking the tight sandstone in the Jurassic Qianyi Member of Tongnanba anticline as the research object,the early channel distribution of Qianyi Member was accu⁃rately described by spectral decomposition and fusion technology.The high-resolution inversion results based on mixed da⁃ta volumes reveal that the porosity of channel sand bodies in Qianyi Member is less than 6%,and the porosity at the anti⁃cline is high(4%-6%).The horizontal distribution of sand bodies in the channel is stable,where the thickness of the brittle sand bodies(with gamma-ray(GR)less than 65 API)changes rapidly and is generally more than 20 m at the anticline.The reservoir prediction results indicate that the channel sand bodies in Qianyi Member of the anticline belt feature large thick⁃ness,good brittleness,high porosity,and shallow burial depth,which are not only the“sweet spots”development areas in Qianyi Member but also favorable target areas for tight reservoir stimulation in the future.