Gas Hydrate Harvesting

Abstract

A harvester (10) with warm water spray jets (11) that fluidizes and releases gas hydrates from seafloor sand and soil. The released gas hydrates float into the harvester (10) and are then transferred through a hydrate slurry pipe (14) to a separation vessel (18). Dissociation of the gas hydrates into methane gas occurs in the separation vessel (18) from its lower pressure than the seafloor and the optional use of heat. The liberated methane gas flows upward in a gas vent pipe (27) to a topside vessel (30) for storage from the pressure of the submerged separation vessel (18). Alternatively, the vent pipe can be fed directly into an available natural gas pipeline. Crude oil collected in the separation vessel (18) can be separated and pumped to a topside vessel (30) for storage and use in a refinery. No other processing is required to produce commercial quality natural gas harvested directly from gas hydrates on or near the seafloor.

Description

BACKGROUND OF INVENTION[0001]1. Field of the Invention[0002]This invention relates to the harvesting of solid gas hydrates within marine sand and soil on or near the surface of the seafloor. More specifically, a method and apparatus to release and capture solid gas hydrates by fluidizing marine sand and soil materials on the seafloor using high pressure warm water spray jets. The gas hydrates are then transported in a liquid slurry to a separation vessel for dissociated into methane gas for commercial use as natural gas.[0003]2. Prior Art[0004]It is widely agreed that harvesting of gas hydrates from the seafloor would solve the world's energy problems. In a recent article by Ray Boswell of the National Energy Technology Laboratory (Science Magazine, August 2009), he stated that the global resource of methane in gas hydrate deposits is commonly cited as 20,000 trillion m3. However, the challenge of reaching and working at the depth of these deposits on the seafloor has limited progre...

AI Technical Summary

Problems solved by technology

However, the challenge of reaching and working at the depth of these deposits on the seafloor has limited progress towards harvesting this vast energy source.

However, the harvesting of gas hydrates using current drilling technology is limited to deposits of gas hydrates that lie several hundred feet below rock or shale type formations on the seafloor.

Considering the enormous potential of harvesting gas hydrates to meet the world's energy needs, no prior art satisfactorily addresses the significant challenge of efficiently removing the vast deposits of gas hydrates buried within seafloor sediment consisting of sand, soil, decayed marine life, etc.

With seafloor sand and soil having a very low thermal conductivity, it is also not practical or efficient to heat the seafloor or seawater near the seafloor since no significant heat transfer into gas hydrates buried within seafloor sand and soil would occur.

This discloses how to harvest gas hydrates from solid concentrations of gas hydrates, but does not disclose how to harvest gas hydrates from sand and soil on the seafloor where the most significant amounts of gas hydrates reside.

However, this patent does not disclose a means to fluidize the seafloor sand and soil to release gas hydrates from their pore spaces to allow efficient heat transfer into the gas hydrates.

However, this patent does not provide a means to fluidize the seafloor sand and soil to release the gas hydrates from their pore spaces.

The presence of hot water above the seafloor sand and soil without fluidization of the sand and soil will not provide sufficient heat transfer to dissociate the gas hydrates into methane gas.

Additionally, this patent does not disclose any means of movement on the bottom of the seafloor to allow harvesting of gas hydrates over wide areas and instead is anchored in one position.

However, this patent does not provide a means to release gas hydrates from the pore spaces of seafloor sand and soil with no moving parts such as high pressure warm water spray jets and instead relies on the impractical use of mechanically driven mining equipment at great depths on the seafloor.

However, this patent relies on a flexible cover to capture the released methane gas without any structural strength to avoid collapse of the flexible cover from variations of up and down currents on the seafloor either naturally or artificially occurring.

Additionally, this patent relies on mechanical equipment being operated up to a mile below the sea surface to move the cover and mine the gas hydrates which is not practical or reliable.

Additionally, it does not address how to harvest gas hydrates safely and economically from seafloor sand and soil.

However, this patent addresses gas hydrates in strata reservoirs below the surface of the sea floor and does not provide a means to harvest gas hydrates from the seafloor sand and soil.

However, this patent does not disclose how to harvest the abundant source of gas hydrates from seafloor sand and soil on the seafloor.

However, this patent is only applicable to concentrations of gas hydrates in reservoirs that can achieve an electro-conductive path and are only accessible using conventional drilling technology in reservoirs under the sea surface.

This patent does not provide a means to harvest gas hydrates from marine sand and soil on the seafloor.

Gullapalli, Jones, and Moridis (U.S. Pat. No. 7,537,058 discloses a depressurization method to recover gas hydrates from existing wells relying on the use of existing drilling technology and practices, but does not address a way to recover gas hydrates from marine sand and soil on the surface of the seafloor.

Only gas hydrates immediately adjacent to the electrical probes would be dissociated into methane gas due to the low thermal conductivity of the seafloor sand and soil, therefore this patent does not provide a practical, economical means to harvest gas hydrates from marine sand and soil on the seafloor.

In summary, no prior art discloses the use of fluidization of marine sand and soil on the seafloor as an efficient means of releasing, and collecting gas hydrate crystals from within the seafloor sand and soil for efficient harvesting and dissociation into methane gas.

The use of only existing drilling technology to harvest gas hydrates, as is now being promoted by the US Department of Energy, severely limits the potential of harvesting gas hydrates and significantly increases the cost and complexity of harvesting gas hydrates.

This is in stark contrast to other energy sources such as crude oil that requires refining and associated additional energy losses and the additional, negative impacts on green house gases.

Images