Patent ID: 8678514

Claim:
A method for converting hydrates buried in a water bottom into a marketable hydrocarbon composition, the method comprising: excavating hydrate, using an underwater excavator, from the water bottom, creating hydrate cuttings and mixing the excavated hydrate cuttings comprising water and bottom particles to form a pipeline transportable hydrate containing slurry; lifting the slurry by means of a slurry lifting assembly comprising an underwater mixing chamber connected to the excavator, in which a chilled hydrocarbon carrier liquid is added to the slurry to convert the hydrate containing slurry into a chilled transportable methane containing intermediate product having a temperature below 0 degrees Celsius, through a riser conduit to a topsides vessel floating at the water surface, wherein the riser conduit comprises a lower section, an intermediate section, and a thermally insulated upper section, and wherein the mixing chamber is connected between the intermediate and upper sections of the riser conduit; transporting the chilled transportable methane containing intermediate product through the thermally insulated upper section of the riser conduit to the topsides vessel, wherein the temperature of the chilled intermediate product is maintained below the ambient temperature of the surface water surrounding the topsides vessel; separating the slurry in a slurry separation assembly at or near the topsides vessel, and arranged between the lower and intermediate sections of the riser conduit, into a transportable methane containing intermediate product and a tailings stream; transporting the transportable methane containing intermediate product to a facility in which the intermediate product is converted into a marketable hydrocarbon composition; and, wherein the slurry lifting assembly comprises a slurry pump, which is actuated by the tailings stream.