四川盆地川中YTB地区沙溪庙组二段沉积微相研究

Sedimentary microfacies of the second member of Shaximiao Formation in YTB area of central Sichuan Basin

四川盆地川中YTB地区沙溪庙组二段致密河道油气显示频繁,发育多条叠置河床,砂体存在由沉积微相变化引起的储层横向非均质性,沉积微相精细刻画难度大,从而难以精准预测天然气的纵、横向分布与产能。为此,结合测井、录井和岩心资料,根据地震响应特征,选取波形聚类和均方根振幅属性预测沉积相带;通过多属性融合技术提高沉积微相识别精度。地震相分析结果表明:①YTB地区侏罗系沙溪庙组二段是一套曲流河沉积,主要发育河床、堤岸及河漫等三种亚相,其中河床亚相主要发育边滩和河道微相,堤岸亚相分为决口扇和天然堤微相,河漫亚相主要发育河漫滩微相;②边滩的储层物性最好,天然堤次之。针对沙溪庙组沉积微相的研究结果能有效指导和支撑致密河道砂岩气藏的勘探、开发,所提的多属性融合技术对四川盆地其他地区沙溪庙组沉积微相的精细刻画具有借鉴意义。

In the YTB area of the central Sichuan Basin,oil and gas frequently show in the tight channel of the second member of Shaximiao Formation,where multiple overlapping riverbeds are developed,and the sand body features lateral heterogeneity of reservoirs caused by sedimentary microfacies change.As the accurate characterization of the sedimentary microfacies faces great difficulties,it is difficult to accurately predict the vertical and horizontal distributions of natural gas,as well as its productivity.Therefore,according to the characteristics of seismic response,the waveform clustering and root-mean-square amplitude attributes are selected to predict sedimentary facies zones given the logging data and core data.The recognition accuracy of sedimentary microfacies is improved by multi-attribute fusion.The results of seismic facies analysis show that:①the second member of Jurassic Shaximiao Formation in the YTB area is a set of meandering river deposits,where three sub-facies are mainly developed,i.e.,riverbed,bank,and flood plain.Among them,the riverbed mainly develop microfacies of marginal banks and channel,and the bank can be divided into microfacies of crevasse splay and natural levee.②The reservoir physical property of the marginal bank is the best,followed by the natural levee.The research results of sedimentary microfacies in Shaximiao Formation can effectively guide and support the exploration and development of tight channel sandstone gas reservoirs,and the proposed multi-attribute fusion technique can provide a reference for the fine characterization of the sedimentary microfacies of Shaximiao Formation in?b C other areas of the Sichuan Basin.