下二门油田梨树凹区扇三角洲沉积特征研究

Sedimentary Characteristics of Fan Delta in Lishuwa Area Xia'ermen Oilfield in Biyang Sag

泌阳凹陷下二门油田梨树凹区南部核桃园组三段Ⅲ-Ⅳ砂组发育扇三角洲沉积,位于盆地东南方向盆地陡坡带,物源供给能力弱,发育范围小,其沉积特征具有自己的特色。在综合分析盆地构造形态、物源、水动力条件等的基础上,确定了砂体的形态与分布,并总结了下二门油田梨树凹区沉积模式。研究表明,下二门油田梨树凹区扇三角洲沉积受间歇洪水作用,河流改道能力弱,河道发育方向稳定,砂体平面呈扇状和伸长型,但砂体主要受水下分流河道作用控制,砂体分布单一,数量少,连通性差,具备独立的水动力系统;该研究区扇三角洲在垂向由下向上发育一套退积和进积地层,平面上扇三角洲平原分布范围小,河口坝不发育,砂体与扇三角洲前缘与东北东南方向不具备渗透性的砾岩和杂砂岩相接触形成岩性封闭。

H3Ⅲ-Ⅳsand group of the Hetaoyuan Formation is located in the steep slope zone in the southeast of the basin,deposit in the fan delta is in the south part of Lishuwa Area of Xia'ermen Oilfield in Miyang Depression.Its source supply is weak and the developmental area is small,therefore,the sedimentary environment has its own characteristics.On the basis of comprehensive study of structural configuration,resources,hydrodynamic conditions and so on,the shapes and distributions of the sand bodies are determined and the sedimentary mode of the area is determined.The research shows that the fan delta sediment of the research area is subject to the intermittent floods;the ability for the rivers to change the developmental direction was weak and stable.The sand bodies are fan-shaped or extended in the plane,but they are mainly controlled by the underwater distributary channels,and their distributions are simple and small with connectivity and independent hydrodynamic systems;in the fan delta a set of regressive and progressive strata are developed vertically from the bottom to top,in the plane the fan delta plain is distributed over a small area,there is no river mouth bar,and a lithologic trap is formed by the sand bodies,the fan delta front and the impermeable conglomerates and greywackes in the northeast and southeast.