Numerical Study Of Multiple-stage Fractured Horizontal Well In Tight Oil Reservoirs Based On Embedded Discrete Fracture Model

As a kind of unconventional resource,tight oil reservoirs hold greatly abundant geological reserves and development potential.As the recoverable reserves of conventional reservoirs becoming less and less,it is an urgency to exploit and develop tight oil reservoirs for the demand of oil and gas resources from economic development.Compared to the conventional reservoirs,the unconventional reservoirs hold the following three characteristics,that is,complex geologic condition for forming reservoirs,strong formation heterogeneity,and low permeability.In order to obtain commercial oil and gas flow,the technology of multiple-stage hydraulically fractured horizontal well is oftern adopted.And numerical simulation is one of the main methods to predict the dynamic deliverability behaviors.Compared to the conventional reservoirs,multiple-stage hydraulically fractured horizontal well leads to the emergency of complex fracture networks.Duing to the local grid refinement,the traditional fracture modeling can hardly characterize the complex fracture networks,while the embedded discrete fracture model(EDFM)can avoid it sot thay it's abled to enhance the operational efficiency and be applied to the reservoirs with densely and randomly distributed natural fractures.Based on that,this paper did some research on the embedded discrete fracture model applying to the tight oil reservoirs,which is of importance in theoretical value and application prospect.Based on the extensive literature review on the fracture modeling,at the background of typical tight oil reservoirs,the research on the numerical simulation of multiple-stage hydraulically fractured horizontal well in tight oil reservoirs with embedded discrete fracture model and finite difference method is developed.The main research results are as follows:(1)Based on the analysis of the flow characteristics,the 2D/3D seepage mathematical model of multiple-stage hydraulically fractured horizontal well in tight oil reservoirs is developed,where the effect of gravity and stress sensitivity are considered.Besides,at the base of EDFM,the coupled mathmatical model of multiple-stage hydraulically fractured horizontal well in tight oil reservoirs is also developed.(2)Based on the model developed above,the semi-implicit difference scheme of embedded discrete fracture model of multiple-stage hydraulically fractured horizontal well in tight oil reservoirs is developed with finite difference method using rectangular mesh.(3)Aimed at increasing the operation speed and decreasing the memory occupancy,the linear algebraic equation system solver is created based on the symmetric successive over relaxation-preconditioned conjugate gradient method(SSOR-PCG)whose convergence rate is much faster.(4)On the computer with Windows 7 operation system,the simulator of embedded discrete fracture model of multiple-stage hydraulically fractured horizontal well in tight oil reservoirs is developed with the MATLAB platform.The simulator can do simulation work on the multiple-stage horizontal well dynamic behavior in 2D/3D homogeneous tight oil reservoirs considering different distribution of natural fractures.The simulato's codes are readable and flexible,and can be re-exploited.The results are identified with the numerical solution of commercial software,KAPPA Saphir.(5)Based on the simulator above,the pressure distribution and dynamic deliverability behaviors of multiple-stage hydraulically fractured horizontal well in tight oil reservoirs are analyzed under different influential factors and the parameters' sensitivity is analyzed too.Finally one field case is analyzed with the simulator.The outcome is identified with the practical field data.The numerical simulation method and technique of embedded discrete fracture model of multiple-stage hydraulically fractured horizontal well in tight oil reservoirs provide an important theoretical guidance for the prediction of dynamic deliverability behaviors of multiple-stage hydraulically fractured horizontal well.