Research On Seepage And Gas Supply Mechanism Of QX Fracture-porous High-pressure Gas Reservoir

The QX gas reservoir is a carbonate high-pressure fracture low-permeability gas reservoir.The fracture distribution of the reservoir is complex.The results of the conventional standard seepage method test cannot reflect the actual conditions of the reservoir,the stress sensitivity is strong,the gas supply mechanism is unclear,and water flooding It is easy to rush along the crack,and studying the complex seepage mechanism of such gas reservoirs is of great significance to the development of technology policy.For this purpose,the oilfield company started the project to analyze the pore structure of the stratum.Based on the composition of the pore throat,the standard method and the high temperature and high pressure phase infiltration experiment,the high pressure stress sensitive experiment under the reservoir overburden pressure,and the high temperature and high pressure gas supply were carried out.The mechanism and the impact of these seepage mechanisms on development provide basic parameters for the subsequent development of the gas field.This paper uses a combination of experimental and theoretical simulations to conduct research.CT and nuclear magnetic methods were used to study the composition and fracture of the pore throat in the reservoir.Five sets of gas-water phase infiltration experiments were carried out under standard conditions and high temperature and high pressure conditions(95.5 MPa).The effects of high temperature and high pressure on the two-phase percolation were evaluated.In the actual stress(165 MPa)constant,the whole-diameter core pore volume compression coefficient measurement experiment and permeability stress sensitivity experiment were carried out in 6 groups;different pore-permeability combinations were produced.Under the innovative 16-group experiment of full-diameter core series gas supply mechanism.The numerical simulation method was used to establish a single well mechanism model.Considering the high-pressure phase infiltration and the stress-sensitive simulation of the production dynamics under the difference of pore-permeability distribution in the inner and outer regions,the gas supply mechanism of the gas well was studied.The main results of this paper are as follows:(1)The pore permeability of the QX gas reservoir is poor,and the existence of cracks has become the main reservoir space and seepage channel.(2)The results of phase infiltration test show that the fractured reservoir is the main seepage channel of the fluid,and the better the physical properties,the lower the water-flooding efficiency;the high-pressure phase infiltration results show that the recovery degree is lower under real reservoir conditions.(3)Stress-sensitive experiments show that with the increase of net effective stress,the compressive coefficient decreases gradually,the reservoir stress sensitivity is moderately weak,and the pore-type reservoir has irreversible damage degree.(4)The test results of gas supply test and numerical simulation results show that the degree of reserve utilization depends mainly on the physical properties of near wells,and the near-well low permeability will limit the use of reserves.