川西北厚坝地区油砂储层特征及成岩作用分析

Oil sand reservoir characteristics and diagenesis in Houba area, northwestern Sichuan

龙门山断裂带前缘厚坝地区中侏罗统沙溪庙组油砂矿是一类典型的非常规油气资源。据野外露头和钻井岩心的宏观与微观研究,探讨了厚坝地区油砂的储层特征及成岩作用特征。研究认为,储层岩石类型以中—粗岩屑石英砂岩和岩屑砂岩为主;储集空间以残余粒间孔及粒间溶孔为主,粒内溶孔较少,裂缝较发育,具有中高孔、中渗的特点;储层成岩作用主要包括压实作用、胶结作用及溶蚀作用。溶蚀作用与绿泥石胶结作用对孔隙的保存均起积极作用,其中溶蚀作用多发生于不稳定颗粒边缘及颗粒内部,形成大量次生溶孔;绿泥石胶结作用可提高岩石的抗压实强度,从而使原生孔隙得以保存。压实作用与钙质及硅质胶结作用对孔隙均起破坏作用,为储层形成的不利因素。

Oil sand of Middle Jurassic Shaximiao Formation in Houba area in the frontier Longmen Mountain is one of the most typically important unconventional resources. Based on crop and core observation, this paper discussed the reservoir characteristics of oil sand and its diagenesis in Houba area. The result shows that the reservoir sandstones are mainly medium-coarse grained sublitharenite and litharenite, the main pore types are residual intergranular pores and intergranular dissolved pores, and fractures are common. The sandstone reservoir has the characteristics of medium- high porosity and medium permeability. Diagenesis includes compaction, cementation and dissolution, and dissolution and chlorite cementation are constructive for the preservation of pores. Dissolution generally developed within grain and boundary of unstable grain, and formed great number of secondary dissolved pores. Chlorite cementation can improve the rock compaction resistance. Compaction, carbonate cementation and quartz overgrowth cause damages to thereservoir pores.