近源湖盆砂砾岩储层次生溶孔成因探讨——以查干凹陷祥6井区为例

查干凹陷祥6井区砂砾岩储层发育蜂窝状次生溶蚀孔隙。通过对岩石薄片、阴极发光薄片及扫描电镜分析,结果表明,该孔隙主要由钙长石颗粒及碳酸盐胶结物溶蚀形成,少量长英质岩屑及石英颗粒边缘也有溶蚀迹象。荧光薄片及包裹体测温证实存在两期胶结作用,结合研究区热演化史研究结果,成岩演化规律与该湖盆主要发育的两期生烃历史、两期构造抬升剥蚀相对应。主要的成岩演化序列:压实作用为主(初次深埋)→长石颗粒大量溶蚀,少量石英次生加大,局部成藏(初次生烃)→第一期胶结(第一期构造抬升剥蚀)→第一期胶结物溶蚀,蜂窝状次生溶孔发育,局部成藏(再次深埋,二次生烃)→第二期胶结物胶结,少量石英质颗粒溶蚀(第二期构造抬升剥蚀)。

Discussion of Secondary Dissolved Pore Origin in Near Source Sandy Conglomerate Reservoir: A Case Study of Xiang 6 Well Area in Chagan Depression

The honeycomb-like secondary dissolved pores are well developed in Xiang 6 well area in one side of Maoxi fault in Chagan depression. Based on thin sections, SEM, and casting thin sections data, the secondary pores formed mainly due to dissolution of anorthite particles and carbonate cement as well as some felsic rock debris and quartz granule. Fluorescence chip and inclusion temperature verified the existence of two stages of cementations. Combining with the evolution of reservoir, we found that the diagenetic evolution corresponded to two hydrocarbon generations and two uplift denudations. The key diagenetic evolution sequences is as follows, Compaction(the first deep burial)-dissolution of a great deal of feldspar particles, little quartz overgrowth and partly accumulation(the first hydrocarbon generation)-the first cementation(the first uplift denudation)-dissolution of the first cement, development of honeycomb-like secondary dissolved pores and partly accumulation(the second deep burial and the second hydrocarbon generation)-the second cementation and dissolution of some quartz particles.