An investigation on environmentally friendly biodiesel-based invert emulsion drilling fluid

As one blend of monoalkyl esters of fatty acids, biodiesel has a potential to serve as the external phase of drilling fluid due to its abundant sources, great safety, low toxicity, and excellent biodegradability. There are some investigations on designing of biodiesel-based drilling fluids, but most of them are about water-free system instead of emulsion system which is the most commonly used. In this paper, a biodiesel-based invert emulsion drilling fluid (BBDF) was prepared and its properties were evaluated. The results revealed that this drilling fluid has high electrical stability, acceptable rheological parameters, and satisfactory filtration property. After hot-rolling at 120 °C for 16 h, these properties are still able to meet the operational requirements for drilling engineering. BBDF can tolerate 10 % sea water, or 15 % drilling solid. Due to its excellent lubricity, low toxicity, and great biodegradability, it is suitable to be used in extended reach drilling, directional drilling, or horizontal drilling. The biodiesel and emulsifier in this drilling fluid system are both produced from waste cooking oil. This may promote the waste recycled and utilized in a more effective and integral way. Some economic analysis and discussion were also made, indicating the cost feasibility of BBDF. Evidently, biodiesel-based drilling fluid has a considerable value for further investigation.