Study On Pore Structure And Seepage Characteristics Of Loose Sandstone In High Water Cut Stage

Due to the characteristics of loose sandstone reservoirs,the pore parameters and seepage characteristics in the loose sandstone reservoirs will be changed during the process of water injection.In this paper,taking the Mingsan sandstone reservoir of Zhuangyi fault block as the study object,pore structure characteristics and seepage mechanics characteristics of sandstone reservoirs are analysed based on indoor displacement experiment combining with data of thin section,fluorescent films,scanning electron microscopy and mercury intrusion.In this paper,in addition to the conventional method of studying the pore and seepage flow,the CT scanning technique is introduced and the three-dimensional model of the pore diameter distribution before and after waterflooding is established to study the pore variation characteristics before and after flooding.Scanning the pore structure before and after water flooding in loose sandstone cores by CT scanning technique.the changes of porosity,pore size distribution,pore size range,face rate and grain size distribution were compared before and after water flooding.Then,the pore structure of the rock before and after water flooding is obtained.Three main pore structure changing characteristics can be summarized according to the results.First,the clay minerals in the coarse throat will be scoured by the injection water,which makes a slight increase in the porosity.Second,greater degree of fractures opening are developed,which makes an obvious increase in porosity.Third,kaolinite will swell when encounter water,which makes a decrease in the porosity for a rich content of kaolinite in this reservoir.Saturation and waterflooding efficiency change for different permeability.Based on the evaluation of waterflooding effect of typical unconsolidated sandstone reservoir.The pore structure characteristics and seepage characteristics of the unconsolidated sandstone during high water cut stage are verified.It provides the basis for the development of water flooding,pore throat change,dynamic prediction of reserves,prediction of water flooding development effect and water flooding recovery ratio in the high water cut stage.