A Highly Inhibitive Vegetable Oil-Based Drilling Fluid

This study aims at finding a more environmentally friendly and efficient oil-based drilling fluid to reduce drilling costs, to minimize the negative effects of the drilling fluid on the environment, to enhance the safety and quality of drilling operation, and to provide a new green drilling fluid solution. It was well known that vegetable oil-based drilling fluids formulated with base fluids such as peanut oil, soybean oil and castor oil have low ecotoxicity, good lubricity and high inhibitive capacity in stabilizing clay formations, and can be used to replace diesel oil-based drilling fluid. In laboratory experiments a vegetable oil-based drilling fluid was formulated with modified cottonseed oil as the base fluid and other oil-based drilling fluid additives. Laboratory evaluation results showed that the vegetable oil-based drilling fluid has strong capacity in inhibiting clay hydration and swelling, good high temperature stability, strong salt and bentonite contamination resistance, as well as excellent reservoir protection performance. Two well-times of successful use of this drilling fluid in Tuha oilfield showed that the drilling fluid performed very well: it effectively stabilized the borehole wall against collapse, ensuring the optimal and fast drilling of the wells and the safety of the drilling operation. Oil-on-cuttings was tested for its toxicity and the results conformed to the relevant standards. The vegetable oil-based drilling fluid has properties equivalent to those of a diesel oil-based drilling fluid and can be used to replace traditional oil-based drilling fluids in the future.