Investigation of rheological properties of methane hydrate slurry with carboxmethylcellulose

Abstract

As offshore oil and gas accumulate in deep water environments, the formation of gas hydrates in water-based drilling mud has become a critical safety problem in drilling operations. In this work, rheological experiments on methane hydrate slurry with carboxymethylcellulose (CMC) are performed with a 0.2%–0.5% CMC concentration, 0.97%–8.49% hydrate concentration, and 27–368 s−1 shear rate. It is confirmed through experiments that hydrate slurry with CMC is a pseudoplastic fluid, whose apparent viscosity decreases with the increase in shear rate and is in a laminar flow regime. The shear-thinning behavior of hydrate slurry with CMC is assumed to be attributed to the shear-thinning behavior of carrier fluids (CMC aqueous solution) and the breakage of agglomerated hydrate particles induced by external shear force. Experimental results reveal that the increase in both hydrate and CMC concentrations in hydrate slurry can decrease its non-Newtonian index and induce shear thinning. Moreover, under a constant shear rate condition, the higher the hydrate and CMC concentration, the higher is the apparent viscosity of the hydrate slurry. The non-Newtonian index and consistence factor of the methane hydrate slurry are correlated as functions of the hydrate concentration and CMC concentration. An empirical Herschel–Bulkley-type rheological model as a function of shear rate, hydrate concentration, and CMC concentration is developed based on experimental data. Moreover, the developed model is validated through additional experiments; the maximum discrepancy is found to be 8.9%.