北部湾盆地涠西南凹陷在流沙港组一段湖底扇中发现了储量较大的油气资源,为了查找出不同油田湖底扇开发效果差别较大的原因,依据岩心、分析化验资料、测井和地震资料,将研究区湖底扇划分为富砾型和富砂型2种湖底扇,并从岩石学特征、粒度、沉积构造和砂体厚度等沉积特征进行了对比分析.研究认为,古地貌和物源供给类型是造成其沉积特征差异的主要原因.同时总结出了2种湖底扇的沉积模式,重力滑塌是富砂型湖底扇主要的触发机制,构造运动是富砾型湖底扇主要的触发机制.2种湖底扇都具有良好的生储盖组合,但富砾型湖底扇由于物性较差,勘探有利方向是寻找次生孔隙发育带;富砂型湖底扇由于储层物性较好,勘探有利方向是寻找有效圈闭.%Large oil and gas resources have been found in sublacustrine fans of the 1st member of Liushagang Formation in the Weixinan Sag, Beibu Gulf Basin. The sublacustrine fans in the study area were divided into conglomerate?rich and sand?rich types through the analyses of assay, core, logging and seismic data in order to clarify the reasons for different development effects of sublacustrine fans in different fields. The main reasons for different sedimentary characteristics include ancient landforms and provenance supply. Two kinds of sedimentary models of sublacustrine fans were summarized. Gravity slumping was the main trigger mechanism for sand?rich sublacustrine fans while tectonic movement was the main trigger mechanism for conglomerate?rich sublacustrine fans. Both had a good source-reservoir-caprock assemblage. However, due to poor physical properties, the favorable exploration direction for conglomerate?rich sublacustrine fans was to find secondary porosity develop?ment zones. Sand?rich sublacustrine fans were suitable to host effective traps due to better physical properties.
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