Study on high performance gas hydrate inhibitor in deepwater drilling fluid

Key words:  deepwater  drilling fluid  gas hydrate  kinetic hydrate inhibitor  inhibition mechanism  combination of inhibitors

Abstract:

An innovative kinetic hydrate inhibitor SDH was prepared based on the optimization of molecular structure. The inhibition characteristics of SDH were experimentally investigated in ultra high pressure and low temperature condition of ultra deepwater by utilization of a simulating device for the inhibition assessment of gas hydrate. The kinetics of hydrate formation in the presence of SDH was investigated based on the pressure-temperature curve and the variations of pressure and temperature with time. The results indicate that the kinetic process of hydrate formation in the presence of SDH can be divided into three periods:hydrate nucleation, slow growth and significant formation. SDH is effective in controlling hydrate growth by steric hindrance effect due to the adsorption on the surface of hydrate crystals under the optimum dosage of 1.0%. The inhibition property of SDH and NaCl mixed system was also tested, and the mixed system could strongly hinder hydrate formation. In a simulation environment (2℃, 30MPa) at 3.0km water depth, the combination of 1.0% SDH and 10% NaCl can prevent the hydrate formation at least 12hours under stirring, which can not only meet the demand of hydrate control in ultra deepwater drilling, but also reduce the cost.