Study On The Fluid Mechanism Characterization Methods And The Well Test Theory Of Multicomponent Gas Flooding

Gas flooding is an important method to improve oil recovery.At present,many reservoirs produce a large amount of associated gas,which is an effective displacement medium.If fully utilized,it can not only improve oil recovery,but also improve resource utilization.However,with the development of multicomponent gas flooding,the oil-gas interaction mechanism and gas flooding dynamics become extremely complicated,which would challenge the characterization of oil-gas interaction mechanism and the dynamic inversion method.Therefore,aiming at solving the above problems,this paper integrates the application of seepage flow mechanics,phase equilibrium,numerical simulation,and computer science to conduct the following research work:Firstly,applying the phase equilibrium calculation method,the mass transfer rule,physical property change characteristics,and miscibility characteristics difference between multicomponent gas flooding and pure gas flooding are studied,which can clary the mechanism of multicomponent gas flooding.Considerining the mechanism of multicomponent gas flooding and applying numerical simulation technology,the distribution characteristics of pressure,mobility,and fluid storage capacity are obtained.Then,the ‘interface skin' technology is proposed to describe the additional pressure drop at the interface of different fluids,and the power-law-function model was established to characterize the spatio-temporal variation characteristics of the fluid mobility and storage capacity.The above two characterization models would provide an important theoretical support to the well test model estabilishment of injection-production well.Then,considering the distribution law of pressure,fluid mobility and fluid storage capacity in the process of gas flooding,four types of well teset model are proposed: the early injection well,the late injeciton well,the early production well,and the late production welltest model of gas flooding.At the same time,the sharp pressure drop at the interface of each zone,and the power-law variation characteristics of mobility and storage capacity are took into account in those four well test models.Then,the four nolinear models are solved by comprehensively applying the analytical,Laplace transform,and Stehfest numerical inversion methods.The seepage characteristics of those four well-test models were also studied.In addition,a systematic analysis of the main controlling factors affecting the characteristics of the bottomhole pressure curve is presented,which provides an important theoretical support to the parameter inversion of injection/production wells.Finally,aiming to eastablish the feature point matching method of pressure derivative curves,the relational expressions of the pressure derivative typical points and the well-test interpretation parameters have been successfully obtained by using the methods of parameter sensitivity analysis,extremum solving,and multivariable regression.And gas flooding dynamic evaluation method is further proposed.In addition,this method is applied to evaluate the sweep characterization and fluid properties by applying the numerical simulation of a typical volatile oil reservoirs,which provides an important reference for monitoring the dynamic development characteristics of gas flooding.In conclusion,based on the data of Kashagan field and the in-depth study of the interaction mechanism of multicomponent gas flooding,this paper puts forward a set of characterization methods and well testing theory which are suitable for multicomponent gas flooding.It provides method and theoretical support for dynamic monitoring of multicomponent gas flooding.