The Numerical Simulation of non-Darcy Flow for YuShulin Low Permeability Oilfield

Abstract

In this paper, a mathematical model for non-Darcy flow in low permeability oil reservoirs is developed, considering the threshold pressure gradient. The model is then discretized into difference equations and solved. FORTAN99 language is used to program the 3D three-phase numerical model for non-Darcy flow in the simulation software. FORTAN99 is used, because it is fast when performing huge engineering calculations. The pre and post processing system for the simulation software is developed using DELPHI language, because it has good interface with WINDOWS and has ability to manage databases. Numerical simulation is done in the simulation software combined with actual data from Yushulin low permeability oilfield. The effects of threshold pressure gradient, well spacing, and water injection modes are investigated. Results show that as the permeability increases from 1×10 -3 μm 2 to 12×10 -3 μm 2 , the sweep efficiency and the water displacement recovery also increases significantly. When the permeability of reservoir is fixed at 5×10 -3 μm 2 , the threshold pressure gradient increases as the well spacing decreases from 350m to 150m. Compared with the inverted nine spot water injection pattern, the sweep efficiencies for the line water injection pattern and the fivespot water injection pattern increase by 6.64% and 7.78%, respectively. The water displacement recoveries for them are increased by 2.94% and 3.57%, respectively.