“点-线-面-体”三维等时融合技术刻画海底扇沉积微相

Three-dimensional isochronous integration technique for depicting microfacies of submarine fans

南海西部琼东南盆地陵水北坡海底扇储层岩性细,物性差,且其低渗的成因不明、甜点储层展布不清。为了弄清海底扇沉积特征,在野外海底扇露头层理结构与岩性组合的基础上,结合地震沉积学的小波分频解释技术和沿层等时切片技术,形成“点-线-面-体”三维等时地层切片体,然后融合具有岩性指示意义的纵波阻抗体,形成三维等时岩性体对海底扇进行等时岩性刻画。研究表明海底扇发育3条主体水道,其水动力强,分选好,储层物性好。主水道的侧翼、前缘、边部发育漫溢天然堤、决口扇、前缘决口扇,其水动力弱,分选差,泥质含量高,物性差。经钻井证实,陵水北坡海底扇横向储层变化差异大,三维等时岩性体刻画精度高。

The submarine fan reservoirs on the northern slope of the Lingshui Depresion of the Qiongdongnan Basin in the western South China Sea consist of fine clastic sediments with poor physical properties,and the occurrance of sweet reservoirs remains unclear.In order to clarify the sedimentary characteristics of submarine fans,this paper takes both the outcrop stratification and lithological association as the guidance,combine the wavelet division frequency interpretation of seismic sedimentology together with the isochronous slicing technique along layers to form the three-dimensional isochronous stratigraphic slice consisting of“point”,“line”,“plane”and“body”.Longitudinal wave impedance,as an effective lithological indicator,are integrated with lithology to form a three-dimensional isochronous depositional system of submarine fans.The study suggests that there are three major waterways formed by strong current,in which filled by the sediments with high sorting and good reservoir properties,while on the flank sides and front edges,such as the overflow natural levee,crevasse fan,and leading edge crevasse,reservoir properties are usually poor due to weak hydrodynamics and poor sorting.It has been confirmed by drilling that the reservoirs on the northern slope of the Lingshui Depression have rapid changes in lithology,and the accurate description of three-dimensional isochronous sandbody is critically important.