胜利油田东营凹陷流体-砂岩相互作用期次及其识别标记

Study on Episodes and Identification of the Interaction of Geofluids with Sandstones in Dongying Half-graben,Shengli Oil Field

胜利油田东营凹陷主要储层砂岩自始新世形成以来经历了至少四期流体的活动,这四期流体与砂岩的相互作用通过矿物溶解、胶结及脉体充填等成岩事件而表现出来。作用过程中溶解作用使砂岩孔隙度增加,改善储层质量;而胶结作用通常使孔隙度减少,伤害储层或破坏储层,但早期胶结作用形成的粗晶碳酸盐矿物可以支撑格架颗粒,阻止后期的压实而导致孔隙"坍塌"。通过东营凹陷坨胜永断裂带和中央背斜及凹陷带沙三段(Es3)和沙四段(Es4)段储层砂岩薄片镜下观察,胶结物电子探针成分分析,综合其它资料得出:第一期流体与砂岩相互作用发生在孔店晚—沙四晚期,以方解石+石膏胶结为标志;第二期发生在沙三—东营(Ed)末,以粗晶"马鞍状"白云石为标志;第三期发生在馆陶(Ng)沉积时期,以微晶含铁白云石为标志;第四期发生在馆陶沉积之后,以铁白云石脉为标志。

The reservoir sandstones in Dongying Dongying Half-graben, Shengli Oil Field have undergone four episodes of interaction of geofluids with sandstone. Dissolution, cementation and micro-vein filling are the major diagenesis under fluid flows. Normally, the dissolution enhances the reservoir quality, while the cementation damages the reservoir quality. But some earlier carbonate cements like coarse ankerite support the skeleton grains and prevent the reservoir sandstones from porous ＂collapse＂. Based on the observation under microscope and probe analyses, four episodes Ⅰ , Ⅱ , Ⅲ and Ⅳ of geofluid activities have been identified for the study area.