辽中南洼C构造区沙三段致密油成藏特征

Accumulation characteristics of tight oil of three section of Shehejie Formation in C structure area of south of Liaozhong Sag

针对致密油成藏特征复杂的问题,通过调研国内外对致密油的研究,利用测井、录井和分析化验资料对渤海海域致密油进行初步厘定,分析辽中南洼C构造区沙三段致密油成藏的主控因素。结果表明:研究区沙河街组致密砂岩主要位于扇三角洲前缘和外前缘相带,砂体类型多,主要有水下分流河道、河口砂坝以及前缘席状砂;整体表现厚层砂(砾)岩夹薄层泥岩或者砂泥互层特征。研究区沙三段上部发育广覆式分布的优质烃源岩与下伏致密砂岩储层大面积直接接触或指状互层接触,形成上源下储和“三明治”型的源储配置类型。沙三段致密油油藏属于储集层经过复杂成岩过程先致密化然后在生烃增压或超压等形成的源储压差作用下晚期(5 Ma)充注成藏的特征。研究区致密油成藏储层孔隙度下限为7%,剩余压力越高和源储接触面积越大,其含油性越好,含油饱和度越高。源储压差的不同、源储直接接触面积和储层物性三因素耦合控制致密油的成藏与分布。该研究成果对辽中南洼致密油的勘探具有重要指导意义。

Be aimed at the problem of complex characteristics of tight oil accumulation,on the basis of investigation and research on tight oil at home and abroad,using logging data,and test data for the preliminary determination of the Bohai sea tight oil,analysis of the tight oil reservoir characteristics of three section of Shehejie Formation of C tectonic zone in south of Liaozhong Sag.The results show that the tight sandstone of Shahejie Formation in the study area is mainly located in the fan delta front and outer front facies belt,and there are many types of sand bodies,mainly including underwater distributary channel,estuary bar and front sheet sand;It is generally characterized by thick sand(gravel)rock mixed with thin mudstone or sand mud interbedding.In the upper part of the third member of Shahejie Formation in the study area,high quality hydrocarbon source rocks that are widely distributed directly contact the underlying tight sandstone reservoir in a large area or finger shaped interbeds,forming the source reservoir configuration type of“sandwich”and“upper source lower reservoir”.The tight oil reservoir in the third member of Shahejie Formation is characterized by the late(5 Ma)filling and accumulation of the reservoir under the pressure difference between the source reservoir and the reservoir formed by the hydrocarbon generation pressurization or overpressure after the complex diagenetic process.The lower limit of porosity of tight oil reservoir in the study area is 7%.The higher the residual pressure is,the larger the contact area between the source and reservoir is,the better the oil bearing property and the higher the oil saturation are.The three factors of the source reservoir pressure difference,the direct contact area of the source reservoir and the physical property of the reservoir control the formation and distribution of the tight oil.The results have important guiding significance to tight oil exploration in south of Liaozhong Sag.