Comparative study of bentonite and Ikwo clay for oil-based drilling mud formulation

Abstract

As the demand for energy rises, drilling activities and the use of drilling mud by oil and gas industries keep increasing, leading to large consumption and high importation cost of drilling mud materials. The study is conducted to replace high cost of drilling mud materials (bentonite) which is a burden on the companies and our economy at large, with respect to foreign exchange challenge. Locally sourced drilling mud material, clay precisely, from Ebonyi State, particularly Ikwo clay, is yet to be explored as alternative to commercial bentonite. The specific objective of this study is to analyse and compare Ikwo clay in replacement to commercial bentonite as viscosifiers for formulating oil-based drilling mud. The driving motivation is to utilize local content (Ikwo clay) which is in abundance and has remained unprocessed substitute for bentonite. The clay undergoes activation using sulfuric acid (H2SO4) following conventional procedures. XRF spectrophotometers determine chemical compositions and functional groups of bentonite and clay samples. Oil-based muds are separately formulated using bentonite and Ikwo clay additives. The mud weight, pH, apparent viscosity, plastic viscosity, yield point, and gel strength of the respective muds are evaluated. The interactive effects of the process variable on viscosities of each mud sample are determined, and the viscosity of the respective muds was optimized using the Central Composite Design (CCD) tool of Design Expert software (version 12) based on RSM. Activation of the local clay improved its properties, as results of the chemical composition revealed that Ikwo clay contains exchangeable cation like potassium ion (K+)) and an essential metal (iron (iii) ion (Fe3+)), with the presence of alumina signifying its suitability in terms of plasticity and swelling ability. The Ikwo clay mud had a higher sample mud weight than the bentonite mud, which indicates that Ikwo clay can manage formation pressure and improve wellbore stability. The optimum viscosities of the oil-based muds with bentonite and Ikwo clay additives are obtained at 15.49 cP and 18.82 cP, respectively. The optimum values are realized at a bentonite/Ikwo clay dosage of 8 wt%, a temperature of 313 K and a mixing time of 35 min. The novelty of Ikwo clay compared to imported bentonite is its ability to offer structural stability to drilling mud (Rana et al., 2020). This feature is used to control wellbore instability during drilling operations. Ikwo clay is a good fit for bentonite replacement as a viscosifier in formulating drilling mud.