Lignosulfonate Stabilized Emulsions in Oil Well Drilling Fluids

Abstract

Abstract Oil in water emulsions have become important in oil well drilling fluids. Lignosulfonates, prominent among various stabilizing agents, have been used successfully for several years in both lime-base and brine-based fluids. This paper is concerned with the surface active properties of the lignosulfonates, the characteristics of lignosulfonate stabilized emulsions, and their application to oil well drilling. Lignosulfonates in solution may be regarded as subcolloidal, high molecular weight polyelectroyltes. They do not possess the hydrophobic-hydrophilic molecular structure or other attributes of the McBain "colloidal electrolyte." In general, lignosulfonates are not effective in lowering surface or interfacial tension of water solutions, but certain sodium lignosulfonates when used in combination with alkaline brines may lower interfacial tension. Lignosulfonates stabilize emulsions because the lignosulfonate molecule is adsorbed at the oil-water interface, establishing a high order electrokinetic charge and also a semi-rigid film. Lignosulfonate stabilized emulsions are stable in high concentrations of inorganic electrolytes, stable to heat, freezing, and to mechanical action. Drilling fluids with lignosulfonate stabilized emulsions may be prepared to control water loss independent of bentonite or organic colloids such as starch. Such fluids may possess low viscosity, low weight, and low water loss simultaneously. These fluids have low mud-making properties and are unaffected by the usual inorganic contaminants, yet if desired may be adjusted to raise viscosity and gel to form high weight muds. A more complete understanding of the lignosulfonate and their potentialities may well aid in the development of drilling fluids designed to cope with certain of the many problems encountered in oil well drilling. Introduction Emulsion muds may be defined as water-base drilling fluids to which oil had been added and subsequently emulsified. These muds are relatively new to oil well drilling, the literature being rather meager until about 1949. Field use in recent years has brought emulsion muds into prominence as important and useful drilling fluids, but full knowledge of their potentialities is yet to be realized.