Drilling through highly sensitive shale areas with challenging well profiles, including highly deviated and extended long reach, require the use of an oil-based mud (OBM). However, environmental legislation restricts the discharge of drilling waste/cuttings especially when the cuttings are contaminated with OBM. Therefore, a more environmentally acceptable drilling fluid system is required. The palm oil derivative drilling fluid system is one of the alternatives to meet the challenge.
Joint development was carried out in Kuala Lumpur and Houston with the goal to develop a high-performance synthetic-based drilling fluid. Three esters of interest were evaluated for possible use as the external phase of an invert emulsion. The testing conducted with the esters included elastomer compatibility testing, base oil viscosity, drilling fluid properties and Leptocheirus 10-day bioassays. A series of tests were also conducted with the blend of ester and paraffin and a blend of ester and mineral oil. Fluids were successfully formulated with a minimum number of components including organophilic clay, emulsifier, calcium chloride brine and barite. Several systems were tested for property changes in response to weight up or contamination with simulated drill solids, seawater or cement. Most systems exhibited acceptable changes in fluid properties. Fluids were observed to be stable up to the test aging temperature of 250°F (121°C). Based upon the tests completed, a more environmentally friendly synthetic oil-based drilling fluid has been developed.