Polyhydroxy gemini surfactant as a mechano-responsive rheology modifier for inverted emulsion drilling fluid

Due to particularity of inverted emulsion, inverted emulsion drilling fluid (IEDF) always has poor mechano-responsive rheology, which greatly restricts its application in the petroleum industry. This study reports the effectiveness of a novel polyhydroxy gemini surfactant (PGS) in responsive rheology modification for inverted emulsion. PGS is prepared by amidation between dimer fatty acid and diethanolamine at a molar ratio of 1 : 2. Rheology tests show that PGS can effectively improve emulsion shear thinning and thixotropic performance as well as viscoelasticity. Modification with PGS is more significant for emulsion at higher volume fraction. Based on various investigations including morphology, stability, interfacial properties, and linear fitting of rheological data, reasonable deductions and probable mechanism are proposed. The interfacial accumulation of PGS makes interfacial film gel-like and droplets attractive. The sensitive attraction enables droplets to exhibit time-dependent and shear-sensitive flocculation depending on outer mechanical conditions, resulting in mechano-responsive rheology of emulsion. In addition to acting independently, PGS is also synergistic with organophilic clay, which suggests the potential use of PGS as a high-performance rheology modifier not only for clay-free, but also for traditional IEDFs.