Characteristics And Seepage Parameter Characterization Of Water Invasion Layer In Shale Matrix

Under the background of the gradual shift of world energy to new energy,shale gas has entered a stage of rapid development.At present,multi-stage fracturing of horizontal wells is mainly used in the exploitation of shale gas,but there is a problem that the flowback rate of fracturing fluid is very low,and a large amount of fracturing fluid is retained in shale reservoir to form water invasion layer.At present,there is little research on water invasion,and there is insufficient understanding of the micro seepage mechanism of shale gas in water invasion.It is imperative to study the water invasion of shale matrix.This thesis studies the water invasion of shale matrix through three scales: micro mechanism analysis,core experimental analysis and reservoir macro simulation.firstly,the micro mechanism of gas-water two-phase migration in the water invasion of shale matrix is preliminarily explored,slit pores with different pore diameters are constructed,silica is used as the wall of pores and hydroxylated,It is used to simulate the characteristics of inorganic pores in shale.Shale gas seepage is simulated in different driving forces,different water saturation and different pore diameters by molecular dynamics method.The analysis of the simulated data shows that the smaller the pore of shale matrix,the more vulnerable shale gas is to the influence of pore water during transportation;Secondly,the relevant characteristics of water invasion layer of shale matrix are studied.Through the simulation experiment of water invasion law,the selected shale rock samples are simulated,and then CT scanning is carried out,and the scanned image is processed,so as to observe the relevant characteristics of water invasion of shale matrix;Finally,the numerical model is constructed to simulate the shale reservoir,complete the dimensionless thickness characterization of the water invasion layer of the shale matrix,and simulate and analyze the parameters such as the thickness of the water invasion layer,the permeability of the water invasion layer and the water saturation of the water invasion layer,so as to obtain the influence law of different seepage parameters on the productivity.The research results of this thesis provide a certain theoretical basis for the study of gas-water two-phase seepage related problems in shale matrix,and have a certain guiding significance for the improvement of gas-water two-phase productivity prediction method of fractured horizontal wells considering complex fracture network.