Experimental lab approach for water based drilling fluid using polyacrylamide friction reducers to drill extended horizontal wells

Abstract

Horizontal and multilateral wells increase continuously and are considered as a mechanical stimulation method for enhancing reservoir performance. However, drilling these wells is challenging with the conventional circulation technology because of the existence of significant pressure loss. Hence, Friction Reducers (FR) may offer a solution to this problem.The objectives of this paper are: (1) to present the possibility of using polyacrylamide based FRs in water base drilling fluids to replace oil based drilling fluids used to drill long lateral sections; (2) to show the optimal pH values of the newly developed FR water base drilling fluids; and (3) to present the effect of FR on both drilling fluid rheological performance and shale inhibition at optimal pH values. Two commercial groups of FR were used in this study, anionic FR (AFR) and cationic FR (CFR). Lab experiments were conducted initially to obtain the effect of pH on the FRs with water and with bentonite by using a low pressure and high temperature rheometer and a Zeta potential analyzer. The rheological properties of formulated Water Based Fluid (WBF) with and without anionic FRs were measured at temperatures ranging from 120° F to 180° F. The zeta potential was also measured to investigate the capability of using anionic FRs as shale inhibition in WBF.The experimental results reveal that the isoelectric point of CFR is at pH value of 8.5 and this CFR charges negatively above pH 8.5. With increasing pH, the viscosity of CFR decreases and there is rise in shear stress of bentonite with CFR. There are obvious effects of pH on anionic FRs with bentonite due to the attraction of negative carboxylate group on AFR surface to positive edge of bentonite. This attraction is a good indicator that anionic FRs can be used as shale inhibition. The optimal pH of using AFR with WBF is from 8.5 to 9.5 for better WBF system stability. The results also reveal that AFR supports thermal stability of the formulated KCl polymer WBF. Furthermore, the formulated WBF with AFR minimize formation damage due to having lower API and high pressure and high temperature filter loss. Zeta potential measurements indicates the initial concentration of AFR used in WBF without KCl for shale stabilization is 18 pptg (0.72 lbm/bbl).This study introduces a promising alternative WBF which could be used to replace oil based drilling fluids when drilling long lateral sections. This proposed approach is important for the oil and gas industry not only for cost effectiveness but also to avail environmental concerns.