An Evaluation of Sugarcane Bagasse as a Bentonite Rheology Modifier

Abstract

Kenya’s growing oil, gas, and geothermal exploration sectors have highlighted the need for more innovative, cost-effective, and sustainable solutions to enhance drilling operations utilizing locally sourced and competent materials. Present studies indicate there are substantial deposits of bentonite clay in Kenya, which can be utilized to replace imported bentonite. However, local bentonite does not meet American Petroleum Institute specifications for a drilling-grade clay. To address this, investigations on improving flow characteristics of locally sourced clays to match American Petroleum Institute criteria are ongoing. Successful findings could help in reducing overdependence on costly imported clay materials to Kenya and the region, and reduce overdependence on costly imported clay materials. This research builds on global efforts to enhance locally sourced bentonite with the aim of evaluating the need for such improvements and assessing current solutions for addressing the poor rheological properties of raw bentonite. One such solution explored is the use of sugarcane bagasse. Sugarcane bagasse is a sustainable, readily available, and underutilized material in many regions of Kenya. The study involved mineralogical and chemical analysis to establish the composition of local bentonite and the extent of treatment and beneficiation required to meet American Petroleum Institute (API) standards. A comparative analysis was conducted on bentonite suspensions treated with soda ash and reactivated with carboxymethyl cellulose before modifying with sugarcane bagasse. From several sample formulations and with varying concentrations, a final blend of 350ml deionized water, 30.0g raw bentonite, 5.0g soda ash, 1.0g carboxymethyl cellulose, and 1.50g sugarcane bagasse, showed promising results, closely aligning with API specifications. Mineralogical and chemical composition analysis was determined to closely relate with API standard criteria, thus, the short falls initiated appropriate treatment and modification with additives. The findings of this specific sample showed a measured pH value of 9.51 and the density of mud at 1.04g/cm3 against API recommended ranges of 8.50 to 10.50, and 1.04 – 1.15g/cm3 respectively. Even though the sample swelled six times its original volume, it recorded a swelling rate of 293.3% which was below the minimum API recommended value of at least 700%. The fluid loss was recorded at 7.0ml/30minutes producing a firm and thin cake of 0.2mm at 100psi which is consistent with the

recommended maximum fluid loss of 16m/30 minutes and maximum thickness of 1.6mm respectively for treated bentonite. The rheological properties were measured at pre-selected temperatures (25oC, 50oC, and 90oC) and at 100psi. At 25oC, it recorded an apparent viscosity of 35. 5mPa.s, and decreased to 22.5 mPa.s at 50oC and 90oC was found to be above the minimum API value of 15 mPa.s. At 25oC, the plastic viscosity was found to be 18mPa.s, decreased to 11mPa.s at 50oC and 90oC which are within and above the minimum API value of 11mPa.s. A gradual decrease of yield point was recorded as19, 9.8, and 7.2Pa at 25oC, 50oC, and 90oC respectively against a maximum API yield point value of 14Pa. Likewise, the yield point to plastic viscosity ratio recorded decreasing values of 1.2, 0.75, and 0.55Pa/mPa.s at 25oC, 50oC, and 90oC respectively against a maximum API value of 6Pa/mPa.s. The initial (10 seconds) and second (10 minutes) gel strength values were 12Pa (initial) & 22.5Pa (second), 8 & 14Pa, and 7.8 & 13Pa at 25oC, 50oC, and 90oC respectively, and were above the minimum API values of 0.19Pa (initial gel strength) and 0.38Pa (second gel strength). For shear stress and shear viscosity, the key parameters considered are 300 and 600rpm to represent low and high rotor speeds respectively. The shear stress values recorded at 25oC, 50oC, and 90oC decreased with an increase in temperature were 35, 23, and 19Pa (at 600rpm) and 21, 18, and 13Pa (at 300rpm). All these values are above the minimum API values of 1.89Pa (at 300rpm) and 2.84Pa (at 600rpm). To ensure proper mud circulation and cutting suspension in the wellbore, the shear viscosity values of 54, 40, and 24mPa.s (at 300rpm) and 42, 20, and 12mPa.s (at 600rpm) at 25oC, 50oC, and 90oC respectively which were above the minimum API values 40mPa.s (at 300rpm) and 55mPa.s (at 600rpm). The shear viscosities decreased as temperatures were elevated