Multiphase Flow in Porous Media: Cake Formation During Extreme Drilling Processes

Abstract

The successful completion of a wellbore requires a low-permeable filter cake to be deposited on the wellbore walls to seal the porous formation exposed by the drill bit. The filtration processes triggered by the differential pressure between the drilling fluid in the borehole and the pore spaces of formation rocks are well known in both drilling operations and, of greater importance, in the subsequent production of oil. The filter cake acts as a barrier to prevent excessive drilling fluid loss into formation, and invasion of formation fluid. The presence of a filter cake also provides wellbore stability and reduces damage to the formation. Understanding cake formation and fluid flow through porous media is necessary for a successful drilling process. This need becomes even more important during extreme drilling, when pressure and temperature may exceed 35,000 psi and 500 °F. This work presents our effort to simulate the fluid flow and cake formation in extreme drilling processes. Earlier investigations were focused on single-phase flow phenomena in porous media; recent studies have emphasized multiphase (thermo-fluid) flow in porous media to closely mimic the actual drilling fluid composed of fine particles and viscous fluid. In the present study, the Eulerian–Eulerian approach for multiphase flow is employed to evaluate the fluid flow and cake formation patterns during ultra-deep drilling at high-temperature, high-pressure conditions. The rheology of the fluid has been published previously [14] and is repeated here for completeness. Two competitive sub-models were considered: the power-law and the Herschel–Bulkley models. The Herschel–Bulkley rheological model appears superior and best describes the non-Newtonian rheological behavior of drilling fluid due to the yield stress term present in this model.