鄂尔多斯盆地上古生界盒8段南北储层差异性对比

Difference comparison between southern and northern sandstone reservoirs of Upper Paleozoic He 8 Member in Ordos Basin

鄂尔多斯盆地上古生界盒8段为盆地北部的主力含气层位,在盆地南部也有不同程度的含气显示,但不具规模,储层发育程度是制约盆地南部天然气勘探的主要因素。为了搞清盆地南部储层发育和分布规律及南北储层差异性,以普通岩石薄片、铸体薄片鉴定、扫描电镜观察、物性资料分析为研究手段,对鄂尔多斯盆地上古生界盒8段南北储层的岩石学特征、孔隙类型、孔渗特征、成岩作用进行了对比研究,分析了储层控制因素。研究表明:相对于北部,南部盒8段砂岩杂基质量分数高,成分成熟度低;储集空间北部以晶间孔和次生溶孔为主,而南部主要为次生溶孔和微裂缝,南部的孔渗较北部差;虽然成岩时序南北相当,但成岩强度存在明显差异,南部地区环边绿泥石发育局限;长石蚀变、自生高岭石、微晶石英少见、溶解较弱。储层物性主要由沉积作用和成岩过程中的压实作用、胶结作用和溶解作用控制。

Upper Paleozoic He 8 Member is the main gas-bearing layer in the northern Ordos Basin.There are hydrocarbon shows in the south to varying degrees,but there is no scale of production.The degree of reservoir development is the main factor to restrict the gas exploration in the south.To understand the development and distribution of southern reservoir and the reservoir difference between the southern and northern reservoirs of Ordos Basin,this paper studied the characteristics of petrology and pores types,porosity and permeability and diagenesis of Upper Paleozoic He 8 Member sandstone reservoir in southern and northern Ordos Basin based on the analysis of common and casting thin slice,scanning electronic microscope and physical property.The result shows that the southern sandstones have higher matrix and lower compositional maturity than that in the north.The main type of porosity is intercrystal pore and secondary dissolved pore in the northern district,but the secondary dissolved pore and microfracture are in the southern district.The porosity and permeability in the north is lower than that in the south.Although the diagenesis sequence in south and north is equivalent,the diagenesis strength is different.There is local grain-coating chlorite development in the southern district.The feldspar,authigenic kaolinite and microcrystal quartz are rarely distributed with weak dissolution.The reservoir physical property is controlled by compaction,dissolution and cementation during the sedimentary process and diagenesis.