In order to ensure safe drilling in deep water and marine gas hydrate bearing sediments,the needed characteristics of drilling fluid system were analyzed.Moreover,the effect of different agents on hydrate formation and the low-temperature rheology of designed polyalcohol drilling fluid were tested,respectively.The results show that clay can promote gas hydrate growth,while modified starch and polyalcohol can inhibit hydrate formation to some extent,and PVP K90 has a good performance on hydrate inhibition.The influence of clay on low-temperature rheology of polyglycols drilling fluid is notable.Therefore,the clay-free polyalcohol drilling fluid is suitable for deep water and marine gas hydrate drilling under optimal conditions.
