Synthesis of a Hydrate Inhibitor and Its Application in Drilling Fluids for Ultra-Deep Water Drilling

In ultra-deep water drilling, the formation of natural gas hydrates aways endanger the safety of drilling and production. The development of excellent kinetic hydrate inhibitors (KHI) which are compounded with thermodynamic is of great importance to the effective inhibition of gas hydrates in ultra-deep water drilling. Using 4-acryloyl morpholine and N-vinylpyrrolidone to copolymerize in different molar ratios to produce kinetic gas hydrate inhibitor ACNs. The reaction conditions are optimized through single-factor method, the reaction products are analyzed by IR, SEM and gel permeation chromatograph, and the properties of the products are evaluated by methane-hydrate simulation (MHS) test and tetrahydrofuran (THF) inhibition performance test. Through the evaluation and test, the best ACN is selected, and is compared with other KHIs. The best ACN is then compounded with thermodynamic gas hydrate inhibitors to produce a gas hydrate inhibitor for use in drilling fluids for drilling in areas with water depth of more than 2,000 m and with narrow safe drilling windows. XXXX found in studies that the best ACN can be obtained when AIBN is used as the reaction initiator and let the monomers react under 65 ℃ for 6 h, and 2% ACN (4∶6) has the optimum inhibition. The formulation of the gas hydrate inhibitor is 2%ACN + 1%KHI-1 + 35%glycol + 5%NaCl. The density of the gas hydrate inhibitor is 1.078 g/cm³, and the initial crystallization time of the gas hydrate inhibitor measured at −25 ℃with THF method is 32 min. The drilling fluid tested has a density of 1.150 g/cm³, a high temperature high pressure filtration rate of less than 17 mL, and a percent shale cuttings recovery in hot rolling test of greater than 82%, satisfying the relevant requirements for the drilling fluid.