Numerical Study Of Fractured Horizontal Well Production Behaviors In Shale Gas Reservoirs Based On Finite Volume Method

Compared with the conventional natural gas resources,the shale gas reservoir is a typical unconventional natural gas resource,and its pore structure is usually dominated by micro-nano-pore.Considering the development of natural fractures and the developing way of fracturing horizontal wells in shale gas reservoirs,the pore structure of shale gas reservoirs usually has multi-scale characteristics and the transport ways of gas in different pore media present different behaviors.The gas in the shale gas reservoirs is usually stored in both free and adsorbed states.In summary,the traditional Darcy's law cannot accurately describe the transport way of gas in the multi-scale porous media.Therefore,in order to accurately understand the seepage characteristics of shale gas reservoir development and realize the efficient development of shale gas reservoir,a set of numerical simulation method for accurately describing the production behaviors of fracturing horizontal well during shale gas exploitation are urgently needed,which reveals the dynamic development characteristics of shale gas reservoir,realizes the macroscopic numerical simulation of multi-fracturing horizontal well in shale gas reservoir,and provides theoretical guidance for the development of shale gas reservoir.Based on the extensive research on the production behaviors of fractured horizontal wells in shale gas reservoirs,the production behavior simulation of fracturing horizontal well in shale gas reservoirs are developed.The main research results are as follows:(1)The apparent permeability model and effective porosity model of shale gas reservoirs with different influencing factors are established,including slip flow,Knudsen diffusion,surface diffusion,adsorption layer effect,rock mechanics effect,adsorption and desorption of gas,and real gas effect on gas transport in shale gas reservoir.(2)Based on the unstructured grid system and the universality and flexibility of numerical discretization theory of two-point flow approximation with finite volume method(TPFA-FVM),a fully implicit iterative method for three-dimensional seepage model of shale gas reservoir is established and achieve it in the MATLAB programming environment.(3)Considering the complicated seepage characteristics of fractured horizontal wells in shale gas reservoirs,an unstructured 3D PEBI grid for multi-stage fracturing horizontal well is established,which can be used for the realization of TPFA-FVM numerical simulation program in shale gas reservoirs.(4)The influence of gas transport mechanism on gas well production is quantitatively analyzed by using the single porosity model of shale gas reservoir.The influence of fracture interference phenomenon with different hydraulic fracture length and inclination on gas well production is analyzed by double porosity model.The effects of different transfer factors on the production performance of the gas well are studied by using the triple porosity model of shale gas reservoir.The research results of this paper deepen the understanding of the gas migration mechanism,adsorption and desorption phenomena,the shape of hydraulic fracture,and transfer factor in shale gas reservoirs.And the method of production behavior analysis of fractured horizontal well in shale gas reservoir are preliminarily formed,which lays a foundation for efficient development of shale gas reservoir.