成岩作用对储层致密化的影响差异及定量表述

苏里格气田苏77区块二叠系下统山西组二段发育自北向南的曲流河，各气层组沉积特征比较一致。但是山西组二段山21、山22亚段气层组比山23亚段气层组储层经历了更强的压实、胶结作用，残余粒间孔所剩无几，加之后期扩容性成岩作用程度不够，次生孔隙发育有限，使得山21、山22气层组成为平均孔隙度不足7%，平均渗透率小于0.3×10-3 μm2的致密储层，与平均孔隙度为7.7%、平均渗透率为1.74×10-3 μm2的山23气层组相比储层渗流能力较差。为了衡量成岩作用程度的强弱，利用视压实率、视胶结率和视溶蚀率的方法来定量分析孔隙度的变化。综合分析认为，研究区山21、山22气层组储层处于中等压实、较强胶结和强溶蚀水平，与山23气层组相比这两个气层组压实、胶结作用丧失的孔隙度远远大于溶蚀、破裂增加的孔隙度，其现今孔隙度只保留到5.48%，成为储集性能较差的致密储层。

Different Influences and Quantitative Description of Effect of Diagenesis on Reservoir Densification: Case study of tight sandstone in Su77 block,Sulige gas field

Meandering rivers developed from north to south formed the second member of the lower Permian Shanxi formation （P₁ s ₂） in Su77 block， Sulige gas field. The sedimentary characteristics of each gas?bearing member were consistent. The first and second members are tight sandstone reservoirs with low levels of residual intergranular and secondary pores due to intense compaction and cementation， with an average porosity less than 7% and average permeability less than 0.3×10-3 μm2. These members are less permeable than the third gas?bearing member of P₁ s ₂ （average porosity 7.7%； average permeability 1.74×10-3 μm2）. The change in porosity was quantitatively analyzed in the present study as functions of the apparent rates of compaction， cementation and dissolution in order to measure the degree of diagenesis. The calculations indicate that the first and second gas?bearing members of P₁ s ₂ suffered medium compaction， less intense cementation， and intense dissolution. Compared to the third gas?bearing member of P₁ s ₂， the reduction in porosity caused by compaction and cementation was much greater than the increase by dissolution and rupturing in the other members， which are poor reservoirs， currently with a porosity of only 5.48%.