松辽盆地王府凹陷泉三、四段浅水三角洲沉积特征及模式

The shallow-water delta deposits from the 3rd and 4th members of the Quantou Formation in the Wangfu depression, Songliao Basin:Sedimentary characteristics and associated model

在岩心观察的基础上,结合测井、地震和区域背景资料分析,认为王府凹陷泉三、四段沉积时期普遍发育浅水三角洲沉积。由于受地形、古气候和水动力条件等多重因素的影响,研究区发育的浅水三角洲在沉积构造、沉积序列、微相类型、三角洲内部结构以及地球物理响应特征等方面呈现出与经典三角洲不同的沉积特征:具有建设性三角洲沉积特征,平面上呈网状,前缘相带延伸较远。具有相对发育的水下分流河道,河口砂坝欠发育;垂向上发育多次间断正韵律。紫红色泥岩大面积展布,生物扰动强烈。砂岩中发育强水动力浅水沉积构造,Gilbert型三角洲的3层结构不明显。浅水三角洲识别出两个亚相和7个微相。研究区具有良好的生储盖配置关系,利于岩性油气藏的形成,其中水下分流河道和分流河道砂体储层物性好,为最有利储层。

The shallow-water delta deposits are of widespread occurrence in the 3rd and 4th members of the Quantou Formation in the Wangfu depression,Songliao Basin. Different from the classical deltas,the shallow-water delta deposits in the study area have the features of constructive delta deposits,developed subaqueous distributary channel,vertically interrupted normal rhythems, widespread purplish red mudstones with highly bioturbated structures,highly hydrodynamic shallow-water sedimentary structures,and indistinct three-layer structures of the Gilbert-type deltas. Two sedimentary subfacies are discriminated, including the delta plain and delta front subfacies,and seven sedimentary microfacies are recognized,including the subaqueous distributary channel,subaqueous crevasse splay,interdistributary bay,distributary channel,crevasse splay,natural levee and floodplain microfacies. Because of near the hydrocarbon-generating depression,the overlying Qingshankou Formation dark mudstones and shales may serve as the excellent cap rocks. The subaqueous distributary channel and distributary channel sandstones reservoirs are believed to be favourable hydrocarbon reservoirs.