Synthesis of a modified fatty acid as rheology modifier and its application

Key words:  rheology modifier  modified fatty acid  weak gel  organoclay-free  oil based drilling fluid

Abstract:

A modified fatty acid (MFA) as the rheology modifier was synthesized which can replace organoclay in oil based drilling fluid (OBM). The influence of MFA on the rheological properties of the emulsions was investigated and three-interval thixotropy was analyzed. The effect of MFA on the microstructure of the emulsion was studied by Cryo-scanning electron microscope (cryo-SEM). And the influence of MDA on oil-water interfacial rheology was characterized by the interfacial rheometer, through which the function mechanism of MFA was analyzed. Also, the applicability of MFA in the high-density OBM was evaluated. It is found that MFA could enhance the emulsion viscosity especially the low-shear-rate viscosity. Emulsions containing MFA present good thixotropic property and a honeycomb structure could be observed. MFA could considerably improve the storage modules of oil/water interfaces and interfacial film strength, which is favorable for the emulsion stability. And MFA adsorbs at the oil-water interfaces, which establishs a three-dimensional network structure in the water-in-oil emulsions through hydrogen bonding. In this way, the “weak gel” structure and gel strength of the emulsionsare enhanced. Compared with OBMs containing the organoclay, organoclay-free OBMs using MFA show superior rheological performance and larger electrical stability.