Abstract:

         When drilling in the marine gas hydrate bearing sediment, the encountered problems include gas hydrate dissociation at the bottom of hole and reformation within the pipeline, as well as the instability of wellbore. A properly designed drilling fluid is a solution to these problems. After tremendous experiments, a formulation of silicate drilling fluid with the addition of inorganic salt and kinetic gas hydrate inhibitor was proposed, and its performance has been evaluated. Finally, it is suggested that the silicate drilling fluid can not only meet the requirements of transporting debris and cleaning hole, but also can effectively inhibit the hydration of wellbore formation and the dissociation of gas hydrate bearing sediments, and the reformation of gas hydrate as well, so the drilling fluid can ensure the safety and efficiency of drilling in marine gas hydrate bearing sediments.

Key words: natural gas hydrate, marine gas hydrate bearing sediment, kinetic gas hydrate inhibitor, silicate drilling fluid