Study On Water Production Law And Productivity Prediction Of Tight Sandstone Gas Reservoir In Western Sulige Gas Field

Natural gas is clean and pollution-free and has become a mainstream energy source.Tight sandstone gas production accounts for about 1/4 of China’s total natural gas production.The reserves are abundant,widely distributed,and have broad development prospects.The Sulige Gas Field is one of the main tight sandstone gas producing areas in China,but the gas wells in the western area of the Sulige Gas Field generally produce water,which seriously affects the productivity of the gas wells.This paper analyzes the special seepage mechanism of Suxi,and conducts research on water production law and gas well productivity.The mineral composition and clay composition of the reservoir were analyzed by X-ray,the core pore structure and formation water distribution were tested by NMR,a new method for judging the mobility of formation water was proposed based on NMR.The development horizon can be optimized according to the water production risk and hydrolock damage,the non-steady-state method is used to test the gas-water relative permeability characteristics with stress-sensitive conditions,and the steady-state method is used to test the gas-water relative permeability laws with different displacement pressure.Based on the experimental rules,a productivity model for fractured horizontal wells is established that takes into account the slippage effect,high-speed non-Darcy,stress sensitivity,time-varying relative permeability,and time-varying fracture conductivity.The research results show that:(1)the Suxi Gas Field has low porosity and low permeability.The mineral composition is dominated by quartz and contains a variety of clay minerals.The pores are dominated by micropores and small pores;the residual water saturation is generally high,and there is no fixed irreducible water saturation value.As the production pressure difference increases,part of the formation water is movable.(2)After the stress sensitivity occurs,the seepage capacity of gas and water is reduced,the water changes more obviously,and the residual water saturation is basically unchanged.The greater the displacement pressure difference,the lower the residual water saturation and residual gas saturation,the wider the two-phase seepage area.As the water saturation increases,the relative permeability of the gas phase decreases more rapidly.(3)Studies have shown that slippage effect and stress sensitivity have little effect on the productivity of gas wells.Considering the mobility of formation water,gas flow is affected by both production pressure difference and water phase flow.There is production Pressure difference,after the pressure difference value is exceeded and the negative effect of water phase flow is greater than the positive effect of pressure difference increase,and productivity decreases with the increase of production pressure difference.(4)In the life cycle of a gas well,the fracture conductivity varies with time The fracture parameter design is based on the principle of not affecting the productivity of the gas well,and the optimal value of the fracture half-length,the ratio of permeability to matrix permeability,and fracture width is obtained.The research results are of great significance for realizing the water control development of gas wells in the west area of Sulige Gas Field and reducing the influence of water flow.