苏里格气田东区致密砂岩储层特征

Reservoir characteristics of tight sandstone in the eastern Sulige Gas Field

鄂尔多斯盆地苏里格气田具有低孔低渗透特征,发育最为典型的致密砂岩储层。基于苏里格气田东区二叠系下石盒子组、山西组及太原组取心资料,结合电镜扫描、铸体薄片等技术手段对致密砂岩储层地质成因、岩石学特征、储集空间类型及储层物性特征进行实验和统计分析。研究结果表明:苏里格气田东区致密砂岩储层主要地质成因为埋深大导致强压实作用所致;孔隙演化过程主要受压实作用和矿物胶结作用影响;储层粘土矿物中高岭石含量较高,且易脱落并堵塞孔喉,片状伊利石和绿泥石充填孔隙形成分割喉道,其他矿物镶嵌胶结及蒙脱石强水敏性等因素使储层渗透性降低;另外,由于原生孔隙不发育,岩石颗粒分选差,粘土矿物充填粒间孔隙,也降低其渗透性;致密砂岩储层储集空间类型主要为岩屑溶孔、晶间孔及长石溶孔。

The Sulige Gas Field in Ordos Basin has the characteristics of low permeability and low porosity,which is the most typical tight sandstone reservoir in China. According to core data from the Lower Shihezi Formation,Shanxi Formation and Taiyuan Formation of Permian system in the eastern Sulige Gas Field of Ordos Basin,experimental observations and statistical analysis were carried out on tight sandstone reservoir from the respects of geological genesis,petrological characteristics,reservoir space types and reservoir physical properties by using scanning electron microscopy,casting thin section analysis and so on. This research shows that the main reason for the formation of tight sandstone reservoir in the eastern Sulige Gas Field is strong compaction caused by deep burial depth. The reservoir pore evolution process is mainly influenced by compaction and authigenic cementation. The kaolinite has the highest content among all the clay minerals,which is easier to fall off and fill the intergranular pore and thus plugs the pore throat. The flaky illite and chlorite can fill pores,which leads to the formation of tubular throat or the segmentation of the throat. The cementation of other minerals and the strong water sensitivity of montmorillonite reduce the gas permeability. In addition,the proportion of primary pore is very low. The rock particle sorting is poor and the clay minerals fill the intergranular pores,which leads to complex relationship between pore and permeability and the reduction of the formation permeability in tight sandstone gas reservoir. The tight reservoir space are mainly lithic dissolved pore,the intercrystal pore and feldspar dissolved pore in the eastern Sulige Gas Field.