The Influence of Water-Base Mud Properties and Petrophysical Parameters on Mudcake Growth, Filtrate Invasion, and Formation Pressure

摘要

The work described in this paper models the complete invasion process quantitatively with a finite-difference invasion simulator that includes the dynamically coupled effects of mudcake growth and multiphase, immiscible filtrate invasion. A fully coupled mudcake growth model is assumed and the flow rate of filtrate invasion is determined from both mud parameters and rock formation properties. Specific parametric representations of the assumed invasion model are based on previously published laboratory experiments on mudcake buildup. As part of the numerical validation of the simulator, we reproduced available experimental data and obtained very good agreements. The influence of several mud and petrophysical parameters on both mudcake growth and filtrate invasion is quantified with a sensitivity analysis. These parameters include mudcake permeability, mudcake porosity, mud solid content, relative permeability, capillary pressure, formation permeability, cross flow between adjacent layers, and gravity segregation. Our simulations reveal the physical character of invasion profiles taking place under realistic petrophysical conditions. Results also characterize formation pressure changes and pressure supercharging observed during wireline formation testing.