Performance evaluation of a benign oil-based mud from non-edible sweet almond seed prunus amygdalus dulcis oil

Abstract

Oil based mud formulated with diesel is commonly used to drill unforgiving formations, such as shale, high pressure high temperature (HPHT), deep water and ultra-deep water, and to improve wellbore stability. However, the major shortcoming of this mud lies in its adverse environmental impact. They are non-biodegradable and highly toxic, thus leading to high cost of wastes treatment. A benign and biodegradable OBM was formulated from sweet almond seed oil (SASO) using Soxhlet Extraction Method. The SASO base oil was converted to SASO methyl ester through the process of transesterification. The possibility of applying this biodiesel–based drilling mud (BBDM) for drilling especially under HPHT and shale formations were examined. The results indicated that the rheology, filtration characteristics, electrical stability, thermal stability and shale swelling inhibition of the BBDM are comparable with those of the diesel OBM. The biodiesel has a flash point of 169 °C and is significantly higher than that of the diesel of 78 °C; indicating its ability to provide better fire safety than the diesel. The results also confirm that the biodiesel is non-toxic because it has significantly higher lethal concentration 50% (LC50) and effective concentration 50% (EC50) than those of the diesel. After 28 days’ period of biodegradation tests, the BBDM displayed 83% aerobic biodegradation with Penicillium sp., while the diesel OBM exhibited 25.2%. The low branching degree and absence of aromatics in the BBDM are the reasons for its higher biodegradation. The selected biodiesel is a naturally occurring seed oil; therefore, its use could be essential for drilling contractors and service companies owing to its great environmental acceptability.