Higher fluid loss volumes and suspension capability are the critical shortcomings of water-based muds. It can promote problems during drilling operations. The rheological and filtration properties of all drilling muds have been continually considered the essential characteristics for a successful drilling operation. Various irreversible problems are directly associated with drilling fluids rheological and filtration properties such as differential sticking, formation damage, borehole instability and uncontrollable formation fluids intrusion to the wellbore. Drilling fluid is closely associated with the complications or solutions of the mentioned problems. The control of such properties is of paramount importance, especially at high temperature conditions of the wellbore. This study aims to formulate a low-solid drilling fluid for better performance by replacing bentonite in conventional fluids with an equal amount of xanthan gum and tapioca starch. The effects of tapioca starch on rheological and filtration characteristics of water-based muds (WBMs) in static conditions have been investigated at different temperatures and pressures. Various mud blends were prepared containing tapioca starch (TS) and polyanionic cellulose (PAC) in the presence of xanthan gum (XG) at different replacement levels. The impact of tapioca starch on rheological and filtration characteristics were evaluated using rheometer, filterpress (LPLT and HPHT) and scanning electron microscope (SEM). The presence of tapioca starch significantly improved rheological and filtration characteristics of water-based muds (WBMs) and revealed that the low solid blends unveiled an obvious shear thinning behavior. Shear stress (σ) versus shear rate (s−1) data of optimized mud samples was best fitted to the Power Law model with R2 of 0.99. The flow behavior index was decreased from 0.47 to 0.21, while the consistency index was increased from 0.31 to 4.45 with the addition of tapioca starch. Rheological properties were improved with the starch concentration and were found within the American Petroleum Institute (API) recommended range. Filtrate volume for the samples containing tapioca starch in 14 ppb was found 4 ml at a temperature of 212 °F. Filtercake thickness was measured 0.27 mm with the maximum concentration of tapioca starch. SEM images confirmed the tapioca starch showed a slick and compact filtercakes at the temperature of 212 °F. This research helps to encourage the use of biodegradable and renewable additives in drilling fluids for the exploitation and production of hydrocarbons.
ASJC Scopus subject areas