Gas Hydrates – Occurance, Production and Economics

Gas hydrates are crystalline compounds stable under particular conditions of low temperature and high pressure. Relatively large quantities of methane can be trapped in small volumes of hydrates, which represent a substantial in-situ natural reserve and ressource in the shallow crust.

In order to recover natural gas from this resource, it is necessary to dissociate the water structure and remove the gas. This is the reason why a new method is put forward:

Hot Solvent Stimulation after Hydraulic Fracturing, with a method called S.T.S.F. The technique resembles Acid Fracturing but replaces Acid by Hot Solvent for the hydrate dissociation. Moreover, the method can be improved by drilling a second production well in order to control the solvent flow in the fracture and the gas production. The shape of the fracture can be either horizontal or vertical depending on the depth and the in-situ stresses.

The following paper describes the development and applications of a heat transfer model, as well as the flow through the dissociated zone by leak-off from the fracture. The analytical solution, obtained through the introduction of some simplifying assumptions, has two main advantages: it can be used without any digital computing equipment and can be easily handled by field engineers.

Graphical results indicate that with S.T.S.F. method gas production and the energy efficiency ratio are three times as high as with any method.

The paper ends with an attempt to analyse the economics of natural gas production from gas hydrates, assuming a satisfactory method of hydrates recovery.

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