西湖凹陷某构造低渗储层成岩演化研究

Diagenetic evolution research on low permeability reservoirs of one structure in Xihu Sag

使用西湖凹陷某构造的常规岩石薄片、铸体薄片、扫描电镜及储层物性分析资料,利用视压实率、视胶结率和视溶蚀率等参数,定量研究了西湖凹陷某构造低渗储层成岩演化序列及孔隙演化过程。研究结果表明:(1)研究区低渗储层孔隙类型以次生溶蚀孔隙为主,粒间溶蚀孔是最主要的次生孔隙类型。(2)机械压实作用是储层低渗的主要因素,导致原始孔隙度损失达65%,溶蚀作用产生的次生溶蚀孔隙一定程度上使储层物性变好。(3)研究区处于中成岩阶段A2期和中成岩阶段B期,成岩演化序列为:(1)脆性颗粒破碎,塑性颗粒变形,局部绿泥石衬边胶结;(2)部分长石及岩屑早期溶解,早期石英次生加大;(3)碳酸盐胶结并交代石英、长石等,石英颗粒发生溶蚀作用;(4)碳酸盐、长石、岩屑等矿物溶蚀形成次生孔隙,石英次生加大;(5)晚期铁方解石少量胶结、交代。该研究成果可为西湖凹陷低渗气藏优质储层的预测与评价提供科学依据。

By using conventional rock thin sections,casting thin sections,scanning electron microscope and reservoir physical property analyses,combined with parameters such as apparent compaction rate,apparent cementation rate and apparent dissolution rate,this paper quantitatively researched the diagenesis sequence and pore evolution process of low permeability reservoir of one structure in Xihu Sag. The research results show that.（ 1） The predominant pore types of low permeability reservoir in Xihu Sag are secondary dissolution pores,and intergranular dissolution pore is the main type of secondary porosity.（ 2） Mechanical compaction effect is the main factor for low permeability,which results in 65% of primary porosity loss,and the dissolution of the secondary dissolution pores improves the reservoir property to some extent.（ 3） The reservoirs in the research area are at stage A2 of middle diagenesis phase and stage B of middle diagenesis phase. The diagenetic evolution sequence is as follows：（1）Brittle particles were broken with the plastic deformation of particles,and local chlorites were edge-cemented;（2）Parts of the feldspar and lithic were dissolved in early period,and quartzs of early period were with secondary overgrowth;（3）Carbonates were cemented and replaced by quartz,feldspar and so on,and quartz particles were dissolved;（4）The dissolution of carbonate,feldspar and cuttings resulted in secondary pores and secondary overgrowth of quartz;（5）Small quantities of iron calcite had cementation and metasomatism. The results can provide scientific basis for the prediction and evaluation of high quality reservoirs in low permeability reservoirs in Xihu Sag.