鄂尔多斯盆地延长世湖盆中部长6段储层成岩特征

Diagenetic Characteristics and Pore Evolution from High-quality Reservoirs of Yanchang Formation in the Middle of Ordos Basin

鄂尔多斯盆地华庆地区延长组长6段储层砂岩属于湖盆中部的砂质碎屑流成因,主要经历了压实作用、胶结与交代作用、溶蚀作用和烃类侵位等成岩作用,目前处于中成岩阶段的A期。研究区的主要孔隙类型为粒间溶孔、粒间孔隙和粒内溶孔,以粒间溶孔为主。孔隙演化整体上呈减小趋势,其中压实作用和胶结作用是孔隙减少的主要成岩作用,使原始孔隙度损失将近90%,是研究区长6段储层成为特低孔特低渗储层的主要因素;溶蚀作用和烃类侵位对孔隙具有建设性作用,其中溶蚀作用决定了华庆地区长6段优质储层的发育状况,产生的次生孔隙占原生孔隙的15.9%。

The reservoir sandstones from Chang 6 oil-bearing interval of the Yanchang Formation in Huaqing area,Ordos basin,were the cause of sandy debris flow in the middle basin,which had experienced primarily the compaction,cementation and metasomatism,dissolution and the emplacement of hydrocarbons.And currently the sandstones ares in the diagenetic stage of A phase.Pore types of sandstones in the area were mainly intergranular dissolved pore,intergranular pore and intragranular dissolve pore,in which intergranular dissolved pore was primary.Porosity evolution decreasingly trended overall,in which compaction and cementation were major diagenesis reducing the original porosities of nearly 90%,and major factors of the studied area ultra-low permeability.However,dissolution and hydrocarbon emplacement played the constructive role of the porosity.Dissolution determined the development status of Chang 6 high-quality reservoir in Huaqing,which generated secondary porosities for 15.9% of primary porosities.