高精度层序地层格架在扇三角洲体系储层精细对比中的应用——以泌阳凹陷赵凹油田为例

Application of High-Resolution Sequence Stratigraphic Framework to Detailed Correlation of Fan-Delta Sandstone Reservoirs:A Case Study from Zhaowa Oilfield of Biyang Depression

由于扇三角洲体系具有相变快、相带窄、多物源等特点,导致扇三角洲砂体储层的精细对比十分困难。根据地震、钻井等资料,建立了高精度层序地层格架,提出了以5级层序为框架、以点物源为中心的储层精细对比思路。赵凹油田储层精细对比研究表明,扇三角洲砂体的沉积类型明显受控于沉积体系域,湖扩张体系域以扇三角洲前缘河口坝和水下水道砂体为主,局部发育泥石流沉积;高水位体系域以三角洲平原辫状水道砂体为主。扇三角洲砂体的岩性、厚度及其分布明显受点物源的控制,在不同物源砂体的叠置区,根据主物源方向、砂体展布形态及岩性差异可以有效地区分出不同物源的砂体,并进行单砂层的对比。

Fan-delta system is characterized by rapid facies variation,narrow facies zone and multiple supply sources,which make it difficult for detailed correlation of fan-delta sandstone reservoirs.In this study,according to the integrated analysis of seismic sections and drillhole data,high-resolution sequence stratigraphic framework has been built up,and the thought for detailed correlation of reservoirs has been pointed out.The study results from Zhaowa Oilfield indicate that the development of fan-delta sandstones is related to the occurrence of depositional system tracts.Fan-delta front sandstones,especially mouth bars and subaqueous channels,are mainly developed in the lacustrine expanding system tract.While braided channel sandstones are mainly developed in the high-stand system tract.Debris deposits usually form in the lacustrine expanding system tract.Fan-delta sandstone,whose graine size,thickness and distribution are controlled by point supply source,can be effectively distinguished form the interbedded sandstones and mudstone areas based on the direction of main supply sources,distributing trend of sandstones and graine size.