致密砂岩储层微观孔喉特征及其对储层物性的影响OA

The pore-throat characteristics of tight sandstones have strong heterogeneity,and there are various factors controlling the reservoir's physical properties.In view of the problems of unknown pore-throat characteristics and complex influencing factors of physical properties in Chang 81 Submember tight sandstone reservoir in Maling area of Ordos Basin,the microscopic pore-throat characteristics of tight sandstone reservoirs and their effects on reservoir's physical properties were studied from the aspects of pore-throat distribution and pore-throat structure characteristics through the experiments of high-pressure mercury injection,constant velocity mercury injection,and nuclear magnetic resonance.The results show that the flow performance of the tight sandstone reservoir in the study area is mainly influenced by the large and medium pore-throats(>0.2 μm),which are the main contributors to permeability.The micropore and small pore throat(<0.2 μm)occupy the main space and are the primary contributors to porosity.The average volume proportion of micropores measured by the nuclear magnetic resonance experiment is 30.08%;that of small pores is 20.31%,medium pores 32.85%,and large pores 16.76%.The average volume proportion of micropores measured by the high-pressure mercury injection test is 44.25%,and that of small pores is 25.55%,medium pores 23.47%,and large pores 6.73%.The results of nuclear magnetic resonance and high-pressure mercury injection experiments are consistent in trend.It is suggested that nuclear magnetic resonance experimental methods be adopted in the study of pore-throat distribution characteristics to avoid core destruction.The physical properties of tight sandstone reservoirs,especially permeability,are mainly controlled by throats,while porosity is influenced by both pores and throats in a similar way.