Development of Stable Bentonite for Drilling Fluid Formulations Using Local Sources

Abstract

Drilling fluid is the key factor in drilling operation and accessing the oil and gas reservoirs. The future trends now are heading for a new development and alternatives to cut the expenses of drilling operation as low as possible. Bentonite is used as a viscofier, fluid loss control additive, and as a weighting material in water-based drilling fluids. The type of bentonite used in drilling fluid formulation is sodium bentonite which has high dispersion properties and high swelling capacity. Saudi Arabia has a huge bentonite clay deposit resources. This enormous amount of bentonite can be evaluated and enhanced in order to be used as drilling fluid and cementing additive. Bentonite natural resources from Khulays Area in North Jeddah, Saudi Arabia, was investigated and found to be calcium bentonite which is not suitable for drilling fluids, because it has low swelling capacity and bad rheological properties. In this study the local bentonite was fully characterized, chemical composition and physical properties were identified. A pure bentonite was extracted through simple designed purification process. Local bentonite was sodium activated using a new proposed of method of thermo-chemical upgrading process with soda ash, which proved to add a crucial affect in the activation process. The experimental work included measuring the rheological properties at low and HPHT of drilling fluid, suspension stability of bentonite, swelling, and filtration. The results obtained from this study showed that the properties of treated local bentonite developed through thermo-chemical upgrading, outperformed the commercial standard bentonite. The rheological properties enhanced and achieved the target of standard API specifications. Therefore, the obtained pure Ca-bentonite from natural deposit in Khulays area can be modified to Na-bentonite and sufficiently used in drilling fluid and cementing additives using thermal upgrading method.