Gas Hydrates

Taking the heat out of the burning-ice debate.

 

This academically reviewed FactBook by A.T. Kearney Energy Transition Institute, “Gas Hydrates,” presents key concepts; the status of exploration and production technologies; the status of research, development, and demonstration (RD&D); and the environmental and safety challenges associated with the potential exploitation of this resource.

One of a series of academically reviewed FactBooks on energy sources and technologies published by the A.T. Kearney Energy Transition Institute, a non-profit energy transition research organization established in 2011, this publication seeks to provide stakeholders with a balanced, unbiased assessment of gas hydrates and the tools to understand them.

From hazard to resource

In addition to tight gas, shale gas, and coalbed methane, a fourth type of unconventional reservoir is showing promise: gas hydrates, a chemical compound resembling ice, in which water molecules form a solid lattice around gas molecules. Although methane is not the only type of gas that can be trapped in this way, it is by far the most common in nature. As a result, the terms “gas hydrate” and “methane hydrate” are often used interchangeably.

Historically, gas hydrates have been viewed as a threat to oil and gas operations. It is only since the 1970s that naturally occurring gas-hydrate accumulations started to be envisioned as a potential source of energy. For this reason, most technologies associated with the recovery of gas hydrates are still at an early stage of development.

Viable exploration and production technologies for sand-rich sediments

Among the various types of deposits, gas hydrates hosted in sand-dominated sediments both within permafrost and offshore stand out as the only resources with any prospect of being recovered in the near term. In-place resources in sand-rich sediments could amount to up to 1,200 tcm of gas.

Contrary to what is commonly believed, these deposits can largely be identified using existing exploration technologies, with small adjustments. For production, which requires the dissociation of the hydrate structure, stakeholders widely agree that depressurization is the most efficient technology for producing gas hydrates from sand reservoirs, whereas interest in CO2-CH4 exchange production techniques has lost momentum.

Long(er)-duration production tests are needed

Dissociation of the hydrate structure is not the only challenge in gas-hydrate production. The recovery phase also raises several problems, such as sand and water production, flow-assurance issues, and harsh operating environments. These issues are familiar to the oil and gas industry, but their convergence creates an unprecedented challenge that may threaten the economic viability of gas-hydrate recovery.

Another threat relates to uncertainties concerning geomechanical stability and subsidence arising from prolonged gas-hydrate production. This underscores the need for long-duration production tests.

Aside from this concern, gas-hydrate recovery should not face any major environmental impediment. However, natural gas-hydrate dissociation issues as a result of climate change should be considered separately.

Asia at the forefront of this new gas frontier

In the absence of long-duration production trials, assessments of the economics of gas-hydrate production remain highly speculative. Important parameters such as well spacing, production profiles, and expected recovery rates remain unknown, since models have not been calibrated. RD&D, therefore, remains vital.

While it seems very unlikely that gas hydrates could be competitive in gas-rich regions, energy independence and energy security concerns, especially in Asia, could help to make the case for gas-hydrate developments—with revolutionary consequences for the energy sector.

 

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