Abstract
Emulsifiers are a class of chemicals derived from fatty acids or their derivatives and used in water-in-oil based mud (OBM) in other words invert emulsion oil based mud. The role of an emulsifier in invert emulsion OBM is to lower the interfacial tension between water and oil to allow the formation of stable emulsion which is an essential quality of oil based mud. These emulsifiers surround the water droplets like an encapsulation with the fatty acid components extend into the oil phase and acts like a small osmatic cell allowing only water to pass through but not salts. Most of the commercially available emulsifiers are derived from Tall oil fatty acid (TOFA) which shows excellent emulsion stability even at harsh conditions. Our objective in this study is to make use of the huge quantity of used cooking/vegetable oil available in the kingdom and convert to an emulsifier suitable for the application in invert-emulsion OBM as vegetable oil contains a wide range of different fatty acids in the form triglycerides. A comparative study has been carried out by formulating invert-emulsion OBM using commercially available emulsifier and the emulsifier derived from used cooking/vegetable oil. Emulsifier (Arc-Eco-Mul) from used or waste vegetable oil has been synthesized by an in-house developed process. A series of different invert-emulsion OBM have been formulated with varying density using in-house developed product Arc-Eco-Mul as primary emulsifier. For comparison, a mud is formulated using commercial primary emulsifier. Mud properties such as density, rheology, API and HPHT filtration control tests have been conducted for fresh mud and for muds hot-rolled at 300degF and 500psi for 16h. It is observed from the laboratory experiments that the mud samples formulated using 12-ppb of Arc-Eco-Mul have similar rheological properties and better filtration control properties compared to the mud samples formulated using 12-ppb of commercial emulsifier. Most importantly, there is no phase separation in the filtrate collected from HPHT filtration control experiment, which showed a very stable emulsion formed by in-house developed Arc-Eco-Mul. Concentration screening experiments showed that only 6-ppb loading of Arc-Eco-Mul is required to achieve a mud with very good rheological and filtration control properties with high emulsion stability. The in-house developed Arc-Eco-Mul from used cooking/vegetable oil has similar properties as commercial additives that are currently used in the industry. This will open an avenue for recycling used cooking oil for oil and gas industry applications.
