Method and apparatus for recovering methane from hydrate near the sea floor

Abstract

Method and apparatus are disclosed for recovering natural gas from a hydrate deposit near or at the sea floor. A rigid dome structure, supported by a floating vessel and movable along the sea floor, is placed over the hydrate deposit. Heated sea water may be pumped from the floating vessel through headers and nozzles in the rigid dome structure. The heated sea water preferably fluidizes the marine sand containing hydrate, releasing gas in the hydrate. The gas is collected in the rigid dome structure and moved through a pipe to the floating vessel, where it may be processed through a turbo-expander and liquefied.

Description

[0001]This regular U.S. application claims priority to U.S. provisional application Ser. No. 61 / 437,099, flied on Jan. 28, 2011.BACKGROUND OF INVENTION[0002]1. Field of the Invention[0003]This invention relates to recovery of methane gas from hydrate deposits on and very near the seafloor. More particularly, a system including a dome structure for capturing the gas and a system of hot-water nozzles for fluidizing the sediments and releasing the gas is disclosed along with processing steps and apparatus to recover energy from and liquefy the released gas.[0004]2. Description of Related Art[0005]The dissociation of methane gas hydrate is represented by:(CH4·6H2O)solid→(CH4)gas+6(H2O)liquidThe energy value of the produced gas is ten times what is needed for the dissociation of the hydrate.[0006]A recent article (R. Boswell, Science, August, 2009) reports that the global resource of methane in gas hydrate deposits is commonly cited as 20,000 trillion m3. For reference, the annual natura...

AI Technical Summary

Problems solved by technology

In addition, bacteria in marine sediments naturally produce enormous volumes of methane when they feed on plant debris washed into the gulf from rivers and swamps.

However, the thickness of the hydrate stability zone in the GOM was determined to not significantly exceed 1000 meters because of temperatures too high for formation of gas hydrates.

The patent discloses how to harvest gas hydrates from solid concentrations of gas hydrates, but does not disclose how to harvest gas hydrates from the pore spaces of marine sands on the sea floor by fluidizing the marine sands.

This patent does not disclose a means to fluidize the marine sands and gas hydrates in the pore spaces of the marine sands on the seafloor to allow rapid dissociation and efficient, safe collection and transportation to the surface for expansion, cooling and storage

However, this patent does not provide a means to fluidize the marine sands and gas hydrates found in their pore spaces

Images