四川盆地上三叠统马鞍塘组沉积相

Sedimentary facies of the Upper Triassic Ma'antang Formation in Sichuan Basin

上三叠统马鞍塘组是四川盆地最重要的勘探层系之一。通过12条露头和10口取心井的岩石学特征分析,结合480口钻井测井相分析和2500km二维地震测线解释,系统探讨了其沉积相类型、分布、相模式及其控制因素。结果表明,四川盆地上三叠统马鞍塘组由南向北依次发育礁滩相、潟湖相、潮坪相和三角洲相。礁滩相主要沿着盆地西部龙门山造山带分布,潮坪相和潟湖相主要分布于盆地中部,而三角洲相主要分布于盆地西北部和中部。3大因素控制着马鞍塘组沉积相的形成,即古地形平缓、碳酸盐生产率低和古基准面变化速率低。马鞍塘组发育鲕粒滩、生屑滩、生物礁和三角洲砂体4类储集层和澙湖相烃源岩,储集层与烃源岩纵向上有效配套,构成有效生储盖组合。

The Upper Triassic Ma＇antang Formation is the most important stratigraphic unit for petroleum exploration in Sichuan Basin. Based on the lithofacies analysis of 12 outcrops and 10 coring wells, the log facies analysis of 480 wells and the interpretation of 2D seismic survey line with 2500 km,the concerning types,distribution,facies model and controlling factors of sedimentary facies of the Ma＇antang Formation were systematically discussed in this paper. As a result,it is proposed that the Ma＇antang Formation includes four types of sedimentary facies from south to north： reef flat,lagoon,tidal flat and delta. The reef flat facies is distributed along the Longmen Mountain orogenic belt in the western margin of the basin;the tidal flat facies and lagoon facies are mainly located in the middle of the basin;while the delta facies is distributed chiefly in the northwestern and middle of the basin. Three factors are contributed to the formation of the sedimentary facies,including the flatpalaeotopography,the low productivity of carbonate and low velocity of palaeo-base level change. There are four types of reservoirs, namely oolitic bank, bioclastic bank, reef and deltaic sand body in the Ma＇antang Formation, and source rocks of lagoon facies. The above reservoirs and source rocks are well matched to constitute an effictive assemblage of source rock and reservoir.