New Kinetic Model to Characterize the Filter Cake Formation and Fluid Loss in HPHT Process

Abstract

Abstract Drilling muds are used in oil, gas, and geothermal well drilling, and fluid loss and filter cake formation are critical issues related to successful operations. Also, the filter cake formation and fluid loss are affected by high pressure and high temperature (HPHT) in the borehole. Rate and total fluid loss from drilling mud can affect the performance of the drilling mud and well safety. Hence, it is critical to quantify not only the rate of fluid loss process but also the changes in the filter cake formation during the fluid loss process. Past studies have assumed that the permeability and solid fraction in the filter cake remained unchanged during the formation of the cake and the fluid loss was directly propositional to the square-root of time (API Model). In the experimental part of this study, fluid loss tests were performed for 420 minutes on 2 percent and 8 percent bentonite drilling muds at 100 psig pressure and 100°C temperature. A new kinetic hyperbolic model was developed based on satisfying the basic governing conditions during fluid loss and assuming that the permeability and solid content during the filter cake formation changes with time, temperature and pressure. The new kinetic model was verified with results from various HPHT fluid loss studies reported in the literature and HPHT experiments performed during this study. The new kinetic model prediction was also compared to the API model, and it predicted both short-term (up to 30 minutes) and longterm fluid losses very well. Hence, the new kinetic model can be used to better model the filter cake formation and filter loss in real time as functions of changes in permeability and solid content in the filter cake.