四川盆地安岳地区须二段储层特征及有利区地震预测

地质研究成果表明,上三叠统须家河组蕴藏着巨大的天然气资源,是四川盆地重要的勘探开发层系。从测试情况看,须二上亚段为安岳地区天然气主产层段之一,其储集砂岩体分布主要受沉积微相控制,非均质性强,单层砂岩体厚度薄,准确地预测高孔隙度砂岩储层有利区带至关重要。为此,以高分辨率三维地震资料为基础,结合高分辨率层序地层学,进行了单井层序的划分;通过井—震资料结合标定层序界面及储层位置并建立了等时地层格架;在等时格架内利用优选出的能反映高孔砂岩的敏感地震属性——AVO梯度G属性及地震波形特征,分析了该区须二上亚段沉积微相的平面展布情况,进而精细刻画出了水下分流河道,结合该区储层裂缝发育情况,最终实现了对高孔隙度砂岩储层的有利区分布预测。实钻结果表明,其预测成果为安岳地区须家河组气藏的进一步勘探开发和降低开发风险提供了重要的基础资料。

Characteristics of T3x2 gas reservoirs and seismic prediction of play fairways in the Anyue area,Sichuan Basin

A geologic study reveals that the Upper Triassic Xujiahe Fm has a large natural gas resource potential and is a major exploration and development target in the Sichuan Basin. Testing results show that the upper interval ofT₃x² (the 2^nd member of the Xujiahe Fm) is one of the major pay zones in the Anyue area, the distribution of reservoir sandbodies is mainly controlled by sedimentary microfacies with strong reservoir heterogeneity, and thin single sandbody, thus the accurate prediction of play fairways of sandstone reservoirs with high porosity is critical to gas exploration and development. Therefore, high resolution 3D seismic data in combination with high resolution sequence stratigraphy were used to divide sequences in a single well. The well seismic correlation method was used to calibrate reservoir horizons and establish an isochronous stratigraphic framework. Within this framework, sensitive seismic attributes revealing sandstones with high porosity, i.e. the G attribute of AVO gradient and seismic waveform, were employed to analyze the plane distribution of sedimentary microfacies of the upper interval ofT₃x² and finely describe the underwater distributaries. Play fairways of sandstone reservoirs with high porosity were finally predicted based on these results and in combination with the distribution of fractures in the reservoirs. Real drilling data revealed that the prediction results are accurate and provide reference for promoting further exploration and development of the Xujiahe Fm gas reservoirs in the Anyue area and lowering such a development risk there.