The model and algorithm of a new numerical simulation software for low permeability reservoirs

Low permeability reserves occupy a large proportion in the remaining reserves all over the world. So it is urgent to research intensively the law of the seepage in the low permeability reservoirs. Fluid flow in the low permeability reservoirs deviates from the classic Darcy's law and instead conforms to the one of nonlinear seepage. According to this characteristic, a nonlinear seepage numerical simulation software has been developed. Unlike most mature commercial numerical simulation softwares at the present stage, the influence caused by the nonlinear seepage is specially considered. In this paper, a nonlinear seepage mathematical model is proposed. In addition, on the basis of practical field and laboratory experiment data, an ideal model of diamond inverted nine spot well pattern is also established. Under the same reservoir condition, the nonlinear simulation, conventional Darcy simulation and the simulation of threshold pressure gradient are also conducted. The simulation result shows that: in the low permeability reservoirs, nonlinear seepage dominates in a large scale of formation and the nonlinear simulation result shows excellent agreement with the production data. Therefore taking the nonlinear seepage into account is more suitable to reflect the percolation mechanism and development performance of low permeability reservoirs.