An analysis of formation damage during the drilling of deviated wells

Abstract

Filtrate losses and filter cake properties of drilling fluids are of concern in the oil industry because they alter near well bore permeability and can reduce well productivity. Therefore, it is desirable to accurately characterize filtration process during oil well drilling. A mathematical model for analyzing mud filtration in deviated wells was developed in this study. The model determined solid pressure distribution within cake, cake thickness, cumulative volume of filtrate and extent of invasion under different conditions. Results show assumptions of isotropy in previous studies greatly overestimate the magnitude of the damage. It was also confirmed that mud filtration tend to be higher in deviated than in vertical wells. The model was validated with experimental data.