Diffusion And Flow Mechanisms Of Shale Gas Through Matrix Pores And Gas Production Forecasting

With the continuous exploitation of oil and gas resources,the production of major oil and gas fields has increased and moisture content has risen.among which shale gas is currently one of the most closely watched resources,but currently China's shale Gas development is still unsatisfactory,stemming from unclear theoretical understanding.First,the understanding of shale reservoirs,including pore types,gas-water distribution,etc.;second,understanding the mode of occurrence because of different types of shale matrices The mechanism of gas adsorption is also not the same,especially with the presence of water,the adsorption mechanism becomes more complicated;Third,the understanding of the gas transmission law of shale gas is not clear,shale pore structure is complex,as small as nano-scale Matrix pores,cracks as large as millimeters,coupled with stress sensitivity,adsorption and desorption,and the effect of real gas effects,make the transmission law more complicated.This study is mainly divided into three aspects.First,based on the theory of shale reservoir formation,the characteristics of gas-water distribution and the law of shale water saturation were analyzed,including “causation of ultra-low water saturation”.The pores of the layers are initially filled with water.Due to the organic-hydrocarbon-drainage effect,there is only a small amount of irreducible water in the organic pores,while the inorganic pores generally have higher water saturation.Second,the types of shale gas adsorption are analyzed in different pore matrices.the adsorption of organic pores is mainly based on the gas-solid interface,while the inorganic pore is gas-liquid adsorption,and the adsorption model is established;the apparent permeability model of different pore shapes is deduced and sensitive The factor analysis shows that the sensitive of stress and the effect of adsorption on permeability have a great effect on permeability,while the effect of real gas can be ignored.Finally,a numerical model of shale gas is established and solved by finite difference method.According to shale gas productivity forecasting curve,analysis of sensitive factors have been studied,stress-sensitive shows at early period of production,late-stage shows effects of desorption,similarly the impact on the yield of real gas effects can be ignored.