重力流水道砂体孔隙演化特征与质量预测——以歧口凹陷歧南斜坡区沙一中亚段为例

Porosity evolution and quality prediction of sand bodies of gravity flow channel:Study of sand bodies in the middle Member 1 of Shahejie Formation in Qinan slope,Qikou sag

重力流沉积砂体多具有非均质性强的特征,优质储集层分布是其核心研究内容。以歧口凹陷歧南斜坡区沙一中亚段重力流沉积砂体为研究对象,在已有认识的基础上,运用地震沉积学研究和成岩作用数值模拟方法,构建构造背景下的沉积、成岩一体化孔隙度预测模型,为重力流砂岩储集层质量评价及预测提供了依据。研究区沙一中亚段主要发育三种沉积微相(水道中心、水道边缘和水下漫溢),沉积学研究表明,储集层物性受沉积作用和成岩作用双重控制,原始储集物性上重力流水道中心储集层物性最好,水道边缘次之,水下漫溢物性最差;平面上,沙一中亚段发育南北两个次生孔隙发育区。处于主水道相区的低斜坡区,尽管埋深大,但溶蚀作用强,晚期胶结作用弱,孔隙度仍可达12%以上。重力流水道的孔隙演化与油气成藏过程密不可分,处于生烃中心的重力流水道中心是增储上产的主要目标。

Gravity flow sedimentary sand bodies always have characteristics of heterogeneous type and the distribution of high quality reservoirs is the core research content.Taking the gravity flow sedimentary sand bodies of the middle Member 1 of Shahejie Formation in Qinan slope area of Qikou sag as the research object,based on the existing knowledge,the seismic sedimentology and the numerical simulation method of diagenesis is used to construct the prediction model of sedimentary and diagenetic integrated porosity under the tectonic setting.In this paper,the conclusion provided the basis for the quality evaluation and prediction of gravity sandstone reservoir.There are three sedimentary microfacies in the middle Member 1 of Shahejie Formation of the study area:the center of the waterway,the edge of the waterway and the overflow of the water.Research of sedimentology shows that the physical properties of reservoirs are controlled by sedimentation and diagenesis.In terms of the original reservoir physical properties,the property of gravity flow channel central reservoir is the best,the waterway edge is the second,and the waterway overflows is the worst.In plane,at the middle Member 1 of Shahejie Formation,there are two secondary porosity developmental areas in the north and south.In the low slope area of the main waterway phase region,the buried depth is large,the dissolution is strong,late cementation is weak,and the porosity can reach more than 12%.The pore evolution of the gravity flow channel is inseparable from the hydrocarbon accumulation process,and the center of gravity flow channel in the hydrocarbon generation center is the main target of increasing production and storage.