Lignosulfonate Stabilized Emulsions in Oil Well Drilling Fluids

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 hrine-base fluids. This paper is con-cer:zed with the surface active properties of the lignosulfonates, the characteristics of lignosulfonate sta-hilized emulsions, and their application to oil well drilling. Lignosulfonates in solution may be regarded as subcolloidal, high molecular weight polyelectrolytes. They do not possess the hydrophobic-hy-drophilic molecular structure or other attributes of the McBain "colloidal electrolyte." In general, lignosulfon-ates are not effective in lowering surface or interfacial tension of water solutions, but certain sodium ligno-sulfonates when used in combination with alk«line brines may lower inter-facial tension. Lignosulfonates stabilize emulsions hecause the lignosulfonate molecule is adsorbed at the oil-water interface, establishing a high order electroki-netic 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.