Using aged oil to produce drilling-fluid lubricants

Abstract

Aged oil is a product of oil and gas treatment and contains components such as oil, water, mud, sand, polymers, and surfactants. Normally, aged oil is mixed back into a crude-oil dehydration and separation treatment system to extract crude oil or treated separately using methods such as electric field dehydration, centrifugal separation, thermochemical dehydration, or biological treatment, amongst others. These methods all require the removal of water, mud, sand, etc. from the aged oil, which can be difficult and costly to treat, making a low-cost treatment method highly desirable. In this study, a resource utilization and treatment method for aged oil was proposed wherein aged oil was used as the base oil to produce lubricants for drilling fluids. This method exploits the emulsifying stability of aged oil and avoids the difficulties of removing mud, sand, and water from it. Through experiments, the components and concentration of the lubricant were optimized, and its performance was evaluated. The emulsifier used for developing lubricants based on aged oil was alkylphenol polyoxyethylene ether (OP-4), the wetting agent was sodium dodecylbenzenesulfonate (ABS), and the stabilizer was sodium carboxymethyl cellulose (Na-CMC). The optimal formula was determined to be 100 mL drilling fluid, 3 mL aged oil, 1.5 g OP-4, 0.15 g of ABS, and 0.015 g Na-CMC. The density, apparent viscosity, and sticking coefficient of the system mud cake satisfied the requirements of enterprise standards after the lubricant was added to the bentonite-based slurry. Consequently, using aged oil as a base oil to develop lubricants for drilling fluids was shown to be a feasible resource-utilization scheme and a viable processing method for achieving value-added aged oil.