Reduction of the Probability of Occurrence of Differential Pressure Sticking Through the Use of Diesel on Water Based Drilling Fluids

Abstract

The drilling campaign on Pad C of the Tiputini Field, located on the Oriente Basin, Ecuador, started with the first exploratory well TPTC-002. Pressure tests performed on the M1 sandstone of the Napo Formation determined that the average reservoir pressure (Pr) was 1921 psi. Ten months later, Pr averaged 846 psi. This increased the risk of differential pressure sticking, event that indeed occurred while drilling the well TPTC-016. By using the “Bow-Tie” methodology as a predictive tool to analyze risks, and taking into account the preliminary studies that describe this phenomena, a solution was found for stablishing an additional barrier with the use of diesel on the water-based drilling fluid. Diesel was used in order to extend the ‘half value time’ and to decrease the friction coefficient between the mud cake and pipe.