Numerical Simulation Theory And Methods Of Fractured Horizontal Well

Fractured horizontal well technology has been one of the most important techniques forthe reservoir exploration and exploitation. Doing research on the production performance offractured horizontal well is helpful to the optimization of horizontal well and fracturedistribution, which can enhance the oil production and recovery. There are many flow patternsin the flow simulation of fractured horizontal well. Choosing the proper grid technique andcoupling method according to the different flow patterns in different regions, is a challengingtask of important theoretical value. With different flow regulations in different regions, thereservoir is divided into four parts: region far away from the well, fracture region, nearwellbore region, and horizontal wellbore. An integral method is applied to derive the flowequations of the reservoir regions. First, accounting for the radial flow nature in the nearwellbore region, orthogonal curvilinear grid systems are used in the wellbore region, andrectangular grid systems are used in the remaining regions of the reservoir. Thetransmissibility of each grid type and the coupling model of hybrid grid system are derived.Second, for reservoirs with isotropy permeability distribution, the flow nature near thewellbore is elliptical. The reservoir region can be divided into elliptical grids in the nearwellbore region and rectangular grid systems in the remaining regions of the reservoir. Thesplit of the reservoir system generates irregularly shaped blocks at the border of differentregions. Simplified equivalent approach is developed to handle the transmissibility of theirregular blocks. Then, the pressure drop model of variable mass flow in the horizontalwellbore, which can be coupled with the near wellbore model and reservoir model of hybridgrid, is obtained. The coupled model of the hybrid grid system all above is resolved byorthomin iterative method with factorization preconditioner. The numerical model is used tosimulate the production performance of different fracture parameters in five point hybrid wellpattern and row well pattern. The results show that, the lower the isotropy coefficient, thesmaller the vertical permeability. It results in the lower recovery. The production contributionof fractures varies with its location. The water cut of the fracture nearest to the injection wellraises rapid, which is disadvantage to the water injection. The production performance offractured horizontal well can be improved by shorting the length and lowering the flowconductivity of the fractures near the injection well. For regions far away from the injection well, the fracture length, the fracture number, and the flow conductivity of the fractures can belarger to improve the production ability of the fractured horizontal well.