地震沉积学技术在库车坳陷南斜坡白垩系砂体尖灭线识别中的应用

Identification of the Cretaceous sandbody pinchout line in the south slope of Kuqa Depression,China,via seismic sedimentology

库车坳陷南斜坡白垩系地层为扇三角洲、三角洲、湖泊相沉积,钻井显示三角洲前缘和滨-浅湖砂坝砂体储层发育,但规模性油气发现较少;已发现的圈闭类型主要为地层圈闭和岩性圈闭,其勘探难点在于对薄层砂岩尖灭线的精细刻画。利用地震沉积学90°相位转换技术解决同相轴与岩性的对应关系问题,利用Wheeler域转换技术解决同相轴的穿时问题,结合地层等时切片技术刻画薄层砂岩尖灭线。将该技术应用于英买1三维工区白垩系舒善河组并取得较好的结果,相较于利用原始地震数据提取属性以及沿层切片预测薄层砂体的结果具有明显优势。勘探实践揭示,三角洲前缘以及滨-浅湖砂坝砂体的尖灭区域油气显示丰富,是地层、岩性油气藏发育的有利区带,因此砂体尖灭线的识别技术对推动库车坳陷地层、岩性油气藏的勘探具有重要意义。

The Cretaceous strata in the south slope of Kuqa Depression,China,include fan and normal deltas,and lake facies deposits,with drilling data revealing the developed delta front and sand bar of a shore-shallow lake.However,large-scale oil and gas reservoirs are rare,with the main Cretaceous traps consisting of stratigraphic and lithologic traps.The primary exploration difficulty lies in the high-resolution characterization of the thin sandstone pinchout line.Here the 90°-phasing technique in seismic sedimentology was employed to improve the seismic sedimentation analysis by refining the correlation between stratigraphic events and their lithologic characteristics.Wheeler domain transformation was adopted to solve the diachronism of the events.The stratigraphic isochronous slicing technique was used to depict the thin-layer sandstone pinchout line.The methods were tested using 3D seismic data from the Yingmai1,China,and application to the Cretaceous Shushanhe Formation yielded significant sedimentological improvements over the conventional extraction of seismic attributes from the raw seismic data and slices along the target layer.Seismic exploration has commonly identified the delta front and pinchout area of the sand bar of shore-shallow lakes as oil-and gas-rich zones,which are favorable for the development of stratigraphic and lithologic reservoirs.The proposed identification methodology for refining the pinchout line of thin sandstone layers is therefore of great significance for the exploration of stratigraphic and lithologic reservoirs in Kuqa Depression