LAUSR

Abstract Rheological and filtration properties of water based muds play vital roles to have a good drilling efficiency in high pressure high temperature (HPHT) environments. However, there are many occasions where controlling the variation of mud properties due to disintegration of additives is barely possible, resulting in stuck pipe, kick incident or even loss of wells. Although there have been many studies in the past indicating the application of nanosilica in improving the flirtation control of water base muds, there are almost no studies on the significant reduction of the yield point which may cause a huge decrease in cutting carrying capacity of muds and rate of penetrations. The aim of this study is to propose an approach to improve the filtration control of water based muds using nanosilica while maintaining the rheology by using a cationic surfactant. The results obtained from zeta potential measurements indicated that bentonite and nanosilica particles are both negatively charged at different ranges of pH, which would result in reduction of the yield point of the mud samples containing nanosilica. This issue was resolved by employing a cationic surfactant and following certain procedures. Filtration tests conducted under LPLT and HPHT conditions indicated that adding modified nanosilica into the mud samples creates a thin and low permeability filter cake without having any negative impacts on the rheology.