The tight sandstone reservoir has a complex pore structure,high clay mineral content,and strong heterogeneity,which is highly susceptible to the influence of external fluids,that can damage the reservoir and restrict productivity.Taking the tight sandstone reservoirs of the second member of the Shanxi Formation(Shan2 Member)in the Zichang East area of Ordos Basin as an example,the sensitivity characteristics of the reservoir were analyzed and evaluated by using the methods of rock slice,cast slice,scanning electron microscope,X-ray diffraction,high-pressure mercury injection,and sensitivity evaluation experiment,etc.and the main influencing factors were analyzed in depth.The results show that the tight sandstone reservoirs of Shan2 member in the Zichang East area of Ordos Basin belong to the categories of weak speed sensitivity-medium strong speed sensitivity,strong water sensitivity,weak salt sensitivity-medium weak salt sensitivity(with the critical salinity ranging from 12.5 to 25 g/L),with local weak acid sensitivity,and with the overall performance of acid sensitivity improvement,no alkali sensitivity-weak alkali sensitivity.The main controlling factors affecting reservoir sensitivity are the quantity type and morphology of clay minerals(mainly kaolinite and illite),the type and distribution of carbonate cement(iron calcite and iron dolomite),the complex diversity of pore structure,and the heterogeneity of the reservoir.The research results are instructive for the optimal configuration of drilling fluid and the fracturing and acidizing technology in the study area.
sensitivitymain controlling factorstight sandstone reservoirs of Shan2 memberZichang East areaOrdos Basin
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