民丰洼陷盐下深层天然气储层特征

Reservoir characteristics of deep-seated gas under gypseous-salt rock in Minfeng Sag

通过镜下微观特征观察及储层孔渗特征统计分析认为,民丰洼陷沙四段膏盐岩层影响了砂砾岩体的成岩作用,致使膏盐岩层上下地层成岩作用特征存在较大差异。膏盐岩层之上地层属于正常成岩作用,而膏盐岩层之下地层处于欠压实状态,原生孔隙得以保存;同时膏盐岩层对酸性地层水起到中和与封隔过用,限制了次生孔隙的发育;微裂缝增强了孔隙连通性,构成了深层天然气储层独特的成岩作用过程。

Based on observation of microscopic feature and statistical analysis of reservoir porosity and permeability characteristics,it is pointed out that gypseous-salt rock in the fourth member of Shahejie Formation influenced the diagenesis of glutenite body and resulted in larger difference between diagenesis feature a-bove and under gypseous-salt rock.Diagenesis above gypseous-salt rock was normal while strata under gypseous-salt rock were uncompacted,and primary pore was well preserved.The gypseous rock neutralized formation water and served as seal beds,as a result,secondary porosity was restricted.Microfracture enhanced connexity of pore spaces and constituted unique diagenesis procedure in deep-seated gas reservoir.