Study On Productivity Evaluation Of Dissolved Gas Drive In Volume Fractured Horizontal Wells In Tight Oil Reservoirs

The tight oil test area of QC Oilfield has achieved effective production by adopting the method of "horizontal well + volume fracturing + depletion development".At present,the formation pressure has dropped below the saturation pressure,and the natural gas is separated from crude oil.The elastic expansion of the dissolved gas is an important displacement energy for EOR in the later stage of production.However,the traditional productivity prediction model is difficult to accurately describe the oil-gas two-phase flow process of volume fracturing horizontal wells in tight oil reservoirs,so it is urgent to make further research.This thesis analyzes the production performance characteristics and production law of tight oil reservoirs in QC well block,and establishes a productivity prediction model of oil-gas two-phase flow in volume-fractured horizontal wells.Finally,the model is verified and applied.Firstly,according to the production performance characteristics of horizontal wells,this thesis summarizes three types of production characteristic modes of QC typical tight oil reservoirs.Based on the production characteristic model,the production law is studied by using three-dimensional geological model and numerical simulation model,the relationship between production dynamic characteristics and elastic energy is clarified,and the elastic energy characterization method is established through the material balance equation to quantitatively evaluate the development potential of dissolved gas elastic energy.Secondly,for the dissolved gas drive stage of tight oil reservoir,based on the traditional trilinear flow model,establishing a two-phase productivity prediction model of oil and gas in volume fractured horizontal wells which considering stress sensitivity and starting pressure gradient.The nonlinear partial differential equations are linearized by introducing pseudo differential pressure function,perturbation transformation and Laplace transformation.The average pressure function is established by combining the Marschet approximation formula and the material balance equation.The semi analytical solution of production under constant pressure is obtained by using the steady state stepwise iterative method.Finally,using MATLAB software to compile the productivity prediction module,and selecting the actual production data for model verification and productivity prediction.The effects of reservoir rock parameters,fluid high-pressure physical properties and artificial fracturing parameters on productivity in dissolved gas drive stage are studied.The research results of this thesis have a certain guiding role for productivity prediction and fracture parameter optimization in the dissolved gas drive stage of volume fracturing horizontal wells in QC tight oil reservoirs,which is of great significance for later development scheme adjustment and efficient development.