致密砂砾岩有效储层主控因素——以松辽盆地南部A断陷为例

松辽盆地南部深层下白垩统登娄库组、营城组和上侏罗统沙河子组广泛发育致密砂砾岩,是该区主要的储层。深层致密砂砾岩气藏显现良好的勘探前景,正确认识该类储层是有效开发其油气资源的前提条件。文中应用地质、化验分析和地球物理等方法,以松辽盆地南部A断陷为例,从沉积相带展布、成岩相类型、构造作用等方面,探讨了该区深层致密砂砾岩有效储层形成的主控因素。结果表明:有利沉积相带多发育在扇三角洲前缘亚相和辫状河三角洲前缘亚相;有利成岩相多发育在三角洲前缘水下分流河道,致密强压实相、致密压实-硅质胶结相、致密压实-含方解石胶结相为有利隔层;穹窿、断鼻等构造附近有利于该类储层微裂缝和溶蚀作用的发生,对储层物性具有明显的改善作用。

Main controlling factors of tight sandy conglomerate effective reservoir: a case study of A Fault Depression in southern Songliao Basin

Both the Denglouku Formation and Yingcheng For,mation of Lower Cretaceous and Shahezi Formation of Upper Jurassic have extensively developed tight sandy conglomerate,which are the main reservoirs in the southern Songliao Basin.In recent years,the exploration of deep tight sandy conglomerate gas reservoirs presents a promising prospect in this area.The right way to recognize these gas reservoirs is the precondition of gas exploring and utilizing.By combining geology,geophysical laboratory analysis with geophysics,this paper elaborates the main control factors of tight sandy conglomerate reservoirs from the sedimentary facies distribution,diagenetic facies types,and structure in A Fault Depression of southern Songliao Basin.The results show that frontal subfacies of the fan delta and braid river deltas are the favorable precipitation facies.More favorable diagenetic facies are developed in the delta front underwater distributarv channel.The strong dense compaction diagenetie facies,dense compaction-siliceous cementation diagenetic facies,and dense compaction-containing calcite cement diagenetic facies are the favorable barrier beds.Near the dome structure and broken nose structure are helpful to micro fractures and denudation of the deep tight sandy conglomerate reservoirs,which significantly improves the reservoir properties.