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蔡家庙-八珠地区位于鄂尔多斯盆地陕北斜坡带的中部偏西,延长组长7层位分为长71、长72、长733个砂层组。研究区延长组长7储层岩性以细粒岩屑长石砂岩和长石岩屑砂岩为主,主要粒径0.095~0.25mm,最大粒径0.55mm,分选以中等-好为主,颗粒呈次圆-次棱状,胶结类型为以孔隙式胶结为主,加大-孔隙式次之,常见长石、石英次生加大。填隙物含量平均为15.2%,填隙物以水云母、硅质、碳酸盐为主,其中水云母含量最高,平均为9.5%;胶结类型以孔隙式为主。孔隙类型以长石溶孔为主,残余粒间孔次之及少量的晶间孔、微裂隙。孔隙结构以大孔中喉与中孔、中小喉为主。成岩作用主要有压实作用、胶结作用、压溶作用、溶解作用及交代作用。压实作用中由于颗粒会发生破裂进而产生一定数量的微裂缝,对低渗储层储集物性的改善具有积极影响。
The Caijiamiao-Baizhu area is located west of the northern slope of the northern Shaanxi Ordos Basin. The 7th member of the Yanchang Formation is divided into a long 71, a long 72, and a long 733 sand layers. The lithology of No.7 Reservoir in Yanchang Formation of Yanchang Formation in the study area is mainly composed of fine-grained feldspar feldspathic sandstone and feldspathic lithic sandstone with the main particle size of 0.095-0.25mm and the largest particle size of 0.55mm. The medium- Particles were sub-round - second prismatic, cemented type to the main type of pore cement, increased - followed by the pore, common feldspar, quartz secondary increase. The average content of interstitial material is 15.2%. The interstitial material is mainly aqua mica, siliceous and carbonate. The content of aqua mica is the highest, averaging 9.5%. The type of cementation is mainly pore type. The pore types are mainly feldspar dissolved pores, followed by a small amount of intergranular pores and micro-cracks. Pore structure in the large hole in the throat and the hole, small throat based. Diagenesis is mainly compaction, cementation, pressure solution, dissolution and account of the role. In the compaction, the fracturing of particles will produce a certain number of micro-fractures, which will have a positive effect on the reservoir property improvement of the low-permeability reservoir.