Effect Of Clay Minerals On Flow In Low Permeability Reservoir

The 21st century is the century of natural gas.With the increasing emphasis on environmental protection and ecology,natural gas,as a clean and powerful energy,is attracting more and more attention.The proportion of natural gas in the world's energy structure is steady rising.However,conventional gas reserves are limited,and not enough to meet the huge market demand.Accelerating the development of unconventional natural gas resources is imminent.Tight gas occupies a large part of unconventional natural gas resources,but there is not any mature theoretical system for the the gas flowing law in low permeability reservoirs.Clay minerals which have a significant effect on the low permeability reservoir development are widely distributed in the formation.Therefore,it is great meaningful to study the effect of clay minerals in the low permeability gas reservoirs on the flow process in the reservoirs.In this paper,rich in clay minerals cores of S gas field are selected to carry out experimental and theoretical research.The main work done is as follows:1.Saturated weighing test,gas permeability test,X-ray diffraction experiment,constant pressure mercury injection experiment,casting sheet and scanning electron microscope experiment are carried out with a designed experiment method which is useful to low permeability cores and can protect clay mineral from damage in the process of experiment.On this basis,the porosity and permeability characteristics,pore-throat distribution,clay mineral content and clay mineral deposit morphology is analysed.2.The original conventional core flowing evaluation system is improved with the installation of a gas booster pump and a self-designed high-precision gas-water separation metering device,and the gas-water permeability testing are carried out.3.A percorlation network model is established to simulate the micro-flow process of gas and water from the statistical view,and the corresponding calculation software is programed.4.The studies show that different types and contents of clay minerals have different effects on the flow of gas fields.In terms of clay content,on condition that no clay mineral are damaged in illite-rich formation,where the total clay content in the formation increases as a percentage of the total mineral,the illite bridge blocked the throat or divide the throat into several,and the distribution of the throat of the reservoir is concentrated in the small throat part,making the reservoir property worse;in chlorite-rich formation,as the clay content in the formation accounts for the percentage of the total minerals Content of the increase,a large number of chlorite attached on the surface of pore and throat,improving the hydrophilicity of the rock.As a resulte,the capillary pressure of throat increase,which block the flowing of natural gas.In terms of clay types,on condition that no clay minerals are damaged,the degree of damage caused by chlorite and illite is similar.