应用压汞实验方法研究致密储层孔隙结构——以准噶尔盆地吉木萨尔凹陷芦草沟组为例

Study on the pore structure of tight reservoir by using method of mercury injection——A case study of the Lucaogou Formation in Jimsar sag,Junggar Basin

随着常规油气资源勘探瓶颈期的到来,致密油气藏越来越成为勘探开发研究的重点。为了进一步揭示致密储层微观孔隙结构特征及其对储层渗流能力的影响,运用常规压汞与恒速压汞方法,结合铸体薄片、扫描电镜等多种技术手段对准噶尔盆地吉木萨尔凹陷芦草沟组致密储层的孔隙结构特征进行综合分析。结果表明:研究区芦草沟组致密储层孔隙以溶蚀与胶结综合作用下形成的粒内溶孔、半充填孔、粒间溶孔、晶间孔隙与晶内溶孔为主;依据常规压汞曲线分布位置、形态,兼顾孔隙度、渗透率及表征孔喉大小、分选、连通的各类参数,将储层划分为5大类进行分类评价。研究区储层喉道半径与孔喉配置关系较常规储层差别较大,储层渗流能力主要由喉道半径分布与孔喉半径比分布控制,而孔喉半径比呈现的双峰特征指示储层具有2种孔隙类型的组合,该类型的储层应成为该区未来勘探开发的重点。

With the advent of bottleneck of the conventional oil and gas resource exploration,tight oil and gas reservoirs are becoming more and more important for exploration and development. In order to further reveal the micro pore structure characteristics and their influences on reservoirs seepage,conventional mercury injection and constant velocity mercury injection method were applied to analyze comprehensively pore structures of tight reservoir in the Lucaogou Formation of Jimsar sag in Junggar Basin combining with casting thin section analysis,scan electron microscope observation and other means.The experimental results indicate that under dissolution and cementation conditions,the main pore type in the research area is characterized by intragranular dissolved pore,half filling pole,intergranular dissolved pore,intercrystal pore and intracrystal pore. Five types of the reservoirs were divided and evaluated respectively,on the basis of the conventional mercury injection curve distribution and its morphology,the porosity and permeability and the parameters characterizing pore throat size,sorting and connectivity. The configuration between pore throat and pore and the pore throat radius of the reservoir in the study area are different from those of conventional reservoir. Reservoir seepage is controlled by both pore throat radius distribution and pore-throat ratio distribution. The bimodal distribution of pore-throat ratio indicates a combination of two types of pores in the reservoir,which suggests a potential target that should be emphatically developed in this area.