Study On The Physical Simulation Of Water Invasion Mechanism Of Ultra-high Pressure Fractured Gas Reservoir

With the deepening of oil and gas exploration,high-pressure and ultra-high pressure oil and gas reservoirs have gradually become important exploration areas for oil and gas resources development.Significantly different from conventional gas reservoirs,ultra-high pressure fractured gas reservoirs have characteristics such as large reservoir burial depth,uneven fracture distribution,serious heterogeneity and strong reservoir stress sensitivity in geology and development.During the development and production process of gas reservoirs,water intrusion is active and the side and bottom water invades the gas reservoir along the cracks,resulting in a rapid increase in water cut-up and rapid decline in production.Gas reservoirs may even be flooded and discontinued,which seriously affects development effect of gas reservoirs.In view of the outstanding problems in the development of the ultra-high pressure fracture gas reservoir,based on the analysis of the water intrusion mechanism and the influencing factors of the water intrusion in the ultra-high pressure fractured gas reservoir,this paper carried out various experimental studies,such as reservoir physical pore structure analysis,stress sensitivity test,gas-water phase infiltration,water intrusion and so on.We have mainly achieved the following results:(1)The analysis of microscopic pore structure characteristics of reservoir cores shows that the reservoir core is dense and no obvious large pore space,the micro cracks are relatively developed.In addition,the pore throat radius is small;The pore throat radius and pore volume distribution are "dumbbell type".(2)The stress sensitivity test results of the matrix core and the fracture core under formation conditions shows that the six test cores have strong stress sensitivity and the stress sensitivity of the fracture core is slightly stronger than that of the matrix core;The reservoir stress sensitive damage to core permeability is permanent and irreversible,the irreversible permeability damage rate of fracture core is much higher than that of matrix core;Core non-dimensional permeability and effective stress are basically in accordance with exponential function relationship.(3)The water flooding experiment and flow characteristics test results of different crack-matrix distribution modes(matrix-crack;crack-matrix;large crack connected;micro-crack)under high temperature and high pressure conditions show that the water flooding efficiency is not overall high,which is serious affected by large cracks;The matrix-fracture distribution mode plays a decisive role in water flooding efficiency and the displacement efficiency of different matrix-fracture cores from high to low is:micro-crack type,matrix-crack type,crack-matrix type,large crack connected type.(4)According to the different fracture distribution patterns,combined with the non-Darcy flow characteristics of the fractured gas reservoir and the gas-water two-phase seepage law,the gas-water two-phase flow productivity equations with different matrix-fracture models considering the permeability stress sensitivity are established.The sensitivity analysis of the factors of the fracture gas reservoir capacity is carried out.Through the above research results,the water intrusion mechanism of ultra-high pressure fractured gas reservoirs is clarified.In addition,some theoretical and technical support is provided for formulating efficient development plans and reasonable water control measures.