东营凹陷古近系红层储层成岩作用及成岩相

综合利用钻井岩心、铸体薄片及物性资料对东营凹陷古近系孔一段—沙四下亚段红层储层成岩作用特征、成岩相及其对成岩圈闭的影响进行研究。结果表明:红层储层压实作用中等偏强;胶结物主要有碳酸盐、铁碳酸盐、石膏及硬石膏和自生石英等;胶结作用在砂体边缘强,砂体内部较弱,在断块下部较弱,断块上部较强;早期胶结作用抑制了压实作用的进行;溶蚀作用由砂体边缘向内部逐渐增强,由断块下部向上部逐渐减弱,主要是长石、碳酸盐胶结物及石英溶解。红层储层中发育压实成岩相、碳酸盐致密胶结成岩相、硫酸盐致密胶结成岩相、中等压实-溶蚀成岩相和强压实-溶蚀成岩相5种类型;不同成岩相储层物性及有效储层含量具有明显的差异,其空间配置关系控制了红层中成岩圈闭的发育。

Diagenesis and diagenetic facies of red beds reservoirs of Paleogene in Dongying depression

Based on the data of drilling cores, casting thin sections and physical properties, the characteristics of diagenesis, diagenetic facies and its influences on diagenetic traps of red beds reservoirs of the first member of Kongdian fromation (Ek₁) and the lower fourth member of Shahejie formation (Es₄^x) of Paleogene in Dongying depression were studied. The results show that compaction is moderate to strong, and cements are mainly carbonate, ferro-carbonate, gypsum, anhydrite and authigenic quartz. Dissolution mainly occurs as dissolving of feldspar, quartz and carbonate cement. Cementation is strong at the boundary belt and pinchout belt of sandstones and is weak at the middle part of sandstones. Strength of cementation in middle part of sandstones increases gradually from the lower part to the upper part of fault block. The early cementation restrained the compaction. Strength of dissolution increases gradually with the increasing of distance to interface of mudstone and sandstone and decreases gradually from the lower part to the upper part of fault block. Five types of diagenetic facies occur mainly:compaction diagenetic facies, dense carbonate cementation diagenetic facies, dense sulfate cementation diagenetic facies, medium compaction-dissolution diagenetic facies and strong compaction-dissolution diagenetic facies. The reservoir physical properties and effective reservoirs content of different diagenetic facies are obviously different. The space allocation of diagenetic facies controls the development of diagenetic traps in red beds.