Biodegradable Surfactants Aid the Development of Environmentally Acceptable Drilling-Fluid Additives

Abstract

Abstract The additives commonly used in oil- or synthetic-based drilling fluids were designed in past years with predominant focus on providing an efficient and economical function. For nearly 50 years, the industry has relied on organically-modified clays to provide viscosity and suspension to non-aqueous fluids. However, the conventional quaternary ammonium salts used to produce these additives have shown poor biodegradability, drawing scrutiny from some regulators. Environmental restrictions governing discharges to the waters of the North Sea have now motivated fluids providers to develop cost-effective additives that deliver performance and also reduce the environmental impact. New organic-modified clay viscosifier additives have been created using biodegradable quaternary ammonium salts. The salient features of the degradable surfactants used are similar to traditional quaternary ammonium salts, but the former include specific sites in their molecular architecture that allow them to be broken down by marine micro-organisms. When select compounds of this type are used to produce organophilic clays, the resultant materials offer functional performance comparable to traditional additives with the added benefit of providing suitable biodegradation for use in environmentally-sensitive areas. A large number of organic-modified clays were produced in the course of a laboratory study spanning a wide range of surfactants. Many of the compounds examined could be used to make viable viscosifier additives, but only a select few that were biodegradable could sufficiently modify the clay surfaces. Performance testing showed that the new clay-surfactant complexes can provide results comparable to a conventional organophilic clay in a paraffin-based invert emulsion system. While a slightly higher concentration of biodegradable clay was needed to obtain comparable yield point values, in one case the increase was less than three pounds per barrel.