Abstract:

FDM (finite difference method) is the most commonly used method in the simulation of waterbase mudfiltrate invasion, which is on the basis of the filtration theory of oilwater twophase flow. The “mesh ladders” are used to approximate the boundary of the deviated wells in conventional orthogonal coordinate system. The mesh size must be diminished to get accurate results, which will extremely increase the computation. The nonorthogonal coordinate systems are introduced to solve the problem. The two kinds of unitary vectors in nonorthogonal coordinate systems can be transformed mutually to orthogonal forms with a set of selfcontained theoretical methods. It is convenient to simulate the models of deviated well or deviated formation in nonorthogonal coordinate systems. The simulation results also approve that the method will get better results with less computation.

Key words: mudfiltrate invasion, FDM, deviated well, nonorthogonal coordinate systems, numerical simulation