Optimizing Drilling Performance By Wellbore Stability Evaluation And Directional Drilling Practices

Abstract

Abstract In this paper we present data from several offshore wells, which have experienced wellbore stability related problems, especially over intervals with higher angles of deviation. We performed a wellbore stability evaluation for several angles of deviation using log, core and drilling data from all the existing wells, in order to predict the optimum drilling parameters to be used in the next wells to be drilled in this area. The answers provided by this study included properties such as, recommended mud-weights (minimum & maximum) as a function of angle of deviation, rock strength, and pore pressure. The determination of the rock strength along with the optimum mud-weight windows improved overall the drilling performance by minimizing washouts, loss of circulation, and optimizing casing design by elimination of unnecessary casing strings. Moreover, improvement of bit performance was achieved by using the predicted rock-strength values. As a result, drilling time and well construction costs were reduced significantly.