Numerical simulation of drilling fluid invasion in highly deviated wells

Key words:  highly deviated well  drilling fluid invasion  gravity  saturation  anisotropy  resistivity

Abstract:

Considering the influence of the gravity and the permeability anisotropy, the invasion pressure, fluid saturation and resistivity distribution in the highly deviated wells were numerically simulated with 3-D finite difference method on the basis of the filtration theory of oil-water two-phase flow. The simulation results show that the effect of gravity is generally slight if pressure difference between the borehole and the original formation is evident. Besides horizontal formation permeability ,the invasion is also affected by vertical .formation permeability and well deviation when formation permeability is anisotropic. The invasion of fresh drilling fluid resulted in the complex distribution of formation resistivity around the borehole. The resistivity of local flushed zone may be higher than the virgin zone resistivity and a low resistive zone appears in invading zone in the oil formation.