川南界市场—黄家场地区须家河组储集砂体成因类型及模式

Genetic type and pattern of reservoir sand bodies of Xujiahe Formation in Jieshichang-Huangjiachang area of southern Sichuan Basin

四川盆地南部界市场—黄家场地区须家河组总体为一套三角洲→湖泊沉积,研究区内砂体十分发育,但砂体非均质性强、成因复杂。本文以3条野外剖面、12口钻井岩心观察、83张薄片鉴定以及扫描电镜和岩心物性等资料分析为基础,结合最新资料和认识,通过精细的沉积微相分析和储集砂体的剖面结构解剖,探讨川南须家河组储集矿体的成因及模式。砂体成因类型主要包括:单一水下分流河道砂体、单一河口坝砂体、滨湖砂坝砂体、浅湖砂坝砂体、叠置型水下分流河道砂体、叠置型河口坝砂体、河口坝与水下分流河道组合类型(包括"坝上河"和"河上坝")。系统研究了形成于不同的水动力条件下,具有不同的岩性结构特征的不同成因类型砂体的储集性能。基于以上研究认识,建立了研究区砂体进积式和砂体退积式2种砂体成因模式。结果表明:研究区须家河组最有利储层发育的位置为河道的中下部,河口坝砂体的中上部;最为有利的储集砂体为砂体进积式下形成的叠置型水下分流河道和"坝上河",也是研究区今后主要的勘探目标。

Generally,Xujiahe Formation in Jieshichang-Huangjiachang area is composed of delt--＋lake sediments. Sand bodies in the study area are well developed,but the heterogeneity of the sand body is severe and its genesis is complex. This paper tried to explore its genesis and patterns. Under the guidance of sedimentary theories and methods and on the basis of observing three field outcrops and twelve drilling cores,analyzing eighty-three thin sections,SEM and analytical data of physical property, in combination with new information and new achievements obtained recently, the authors made a detailed analysis of sedimentary facies and dissection of section structure of the reservoir sand body,and found that the study area of Xujiahe is composed mainly of single underwater distributary channel sand,single-mouth bar sand,lake sand bar sand,shallow lake sand bar sand, superimposed distributary channel sand,superimposed mouth bar sand,and combination type of underwater distributary channel and mouth bar （including the ＂ river-over-bar ＂ and ＂ bar-over-river ＂）. Combined with physical property data,the authors systematically studied the accumulation performance of the sand bodies developed in different parts of the river, which are of different genetic types with different lithologic structural characteristics. On such a basis,this paper established two genetic models for sand bodies in the study area： one is the sand body prograding model and the other is sand body retrograding model. The results show that in the study area of Xujiahe, the most favorable places for the reservoir development are the middle-lower reaches of the river and the middle and upper parts of the mouth bar. The most favorable reservoir sand bodies for reservoir accumulation are the superimposed distributary channel and the ＂river-over-bar＂,and they also serve as the main exploration targets in the study area in the future.