Gas-Water Production Dynamics Of Multi-Stage Fractured Horizontal Wells In Tight Gas Reservoirs

Both the reserves and production of the tight gas reservoir occupy a considerable proportion in China’s natural gas energy structure.With the increase in demand for natural gas resources and the improvement of exploration and development technologies,unconventional oil and gas reservoirs such as tight gas reservoirs have received extensive attention in the field of oil and gas development and have become the focus of current research.To accelerate the development of such gas reservoirs is of great strategic significance in protecting national energy security and promoting economic and social development.The tight gas reservoirs are mostly low-porosity-extra low-permeability tight sandstone reservoirs featured with high water saturation and low natural productivity,which require reservoir stimulation to obtain industrial gas flow.The horizontal well multi-stage fracturing technology is currently the most effective way to increase the production of such gas reservoirs.In general,non-linear seepage phenomena such as slippage,stress sensitivity,high-speed non-Darcy,etc.often occur in the development of stimulated tight gas reservoirs.Therefore,it is of great theoretical and practical value to comprehensively study the gas-water production dynamics of multi-stage fracturing horizontal wells in tight gas reservoirs under different reservoir parameters,fracture parameters,etc.for the development of such gas reservoirs.This paper comprehensively applies advanced seepage mechanics,numerical simulation,gas reservoir engineering to make a thorough and in-depth research about the gas-water production dynamics of fractured horizontal well in tight gas reservoirs.This research has made the contributions as follows:(1)According to the characteristics of tight sandstone gas reservoirs,a discrete fracture numerical model considering gas slippage effect,pressure-dependent permeability of artificial fractures and non-Darcy flow was developed.(2)The governing equations of fluid flowing in porous medium were decouped to solve unknown parameters of pressure and saturation.Based on unstructured triangular meshes,the FEM was used to discretize the pressure equations,and the FEM-FVM was used to discretize the saturation equations,so that a nonlinear gas-water two-phase numerical model was developed.(3)The IMPES method and the Newton iteration method were employed to solve the numerical model established in(2).And the FEM-FVM numerical simulator for tight gas reservoirs was developed with the help of MATLAB.(4)The production performances of muti-stage fractured horizontal well under constant bottom-hole pressure in a tight gas reservoir was calculated by the simulator.And the effects of fracture networks model,reservoir properties,hydraulic fractures parameters,and seepage mechanism on gas well productivity had been analyzed in detail.The numerical model established in this paper is of great guiding significance to study the production performance of fractured horizontal well in tight gas reservoir and to realize the reasonable and effective development of unconventional tight gas reservoir with multi-stage fractured horizontal well.