Numerical simulation of multi-phase mud filtrate invasion and inversion of formation tester data

Mud-filtrate invasion takes place in permeable rock formations drilled with an overbalanced borehole. This phenomenon is of interest to numerous oilfield applications including drilling, reservoir simulation, reservoir stimulation, and well-log analysis. Electrical, electromagnetic, sonic, and nuclear measurements acquired with well-logging instruments are all influenced by mudfiltrate invasion.; This dissertation develops accurate and efficient algorithms for the numerical simulation of the phenomenon of mud filtrate invasion around an overbalanced borehole. Emphasis is placed on embedding geometry consistent with mud-cake buildup, multiple-bed rock formations, and deviated boreholes. Boundary and initial conditions for the simulation problem are enforced to replicate actual drilling environments, including the time-lapse process of mudcake buildup coupled to rock formation properties. Checks of numerical consistency and accuracy of the numerical simulation algorithm are performed against existing numerical and laboratory results. The simulation algorithms are used to perform an extensive sensitivity analysis to assess the influence of various drilling and petrophysical parameters on the phenomenon of mud-filtrate invasion. Results from this sensitivity analysis are used to construct parametric petrophysical models for the quantitative evaluation of wireline logs in terms of petrophysical parameters. Examples of such an assessment are presented for the petrophysical interpretation of electromagnetic induction logs. It is shown that the phenomenon of mud-filtrate invasion has a significant influence on electrical resistivity readings. In particular, simulation examples clearly show that the process of salt mixing between mud-filtrate and connate water is important to properly interpret induction logs in terms of in-situ fluid saturation.; A second component of the dissertation concerns the estimation of petrophysical properties from formation-tester measurements. Inversion algorithms are developed to approach such a problem. The algorithms account for the effect of mud-filtrate invasion and make use of a forward numerical model that correctly simulates the time-lapse behavior of 3D multi-phase fluid flow in the near wellbore region imposed by fluid pumpout. (Abstract shortened by UMI.)...