Environmentally benign invert emulsion mud with optimized performance for shale drilling

摘要

Drilling muds having less environmental footprint are highly desired, especially for drilling into sensitive formation. In this research, an environmentally benign invert emulsion mud having Indian mango methyl ester (IMME) continuous phase was developed for shale drilling. The properties of the mud were tuned using nanoclay and gum acacia in order to minimize shale instability associated with rock-fluid interactions. The effect of nanoclay and gum acacia content on the rheological behavior and fluid loss of the developed mud was assessed. Furthermore, the thermal and mechanical stability of the mud were estimated. Results obtained with nanoclay and gum acacia were compared with the conventional bentonite and carboxymethyl cellulose additives. Muds containing nanoclay and gum acacia outperformed conventional additive-containing muds in all measures. The rheological properties, such as apparent and plastic viscosities, yield point and gel strength, of the mud formulated with gum acacia and nanoclay were remarkably enhanced. Moreover, the mud containing nanoclay and gum acacia was mechanically and thermally stable up to 100 degrees C. Particle size analysis of this mud confirmed the suitability of the additives toward shale plugging. The invert emulsion with the nanoclay and gum acacia achieved 95% weight recovery comparing with the conventionally used bentonite and CMC, which only achieved 64% weight recovery. Overall, the 40:60 (W/O) invert emulsion with IMME continuous phase and nanoclay and gum acacia additives portrayed ideal viscosity, rheology, fluid loss, particle size distribution and stability suited for shale drilling.