Methane Hydrates Research Program
Methane hydrate—molecules of natural gas trapped in an ice-like cage of water molecules—represents a potentially vast methane resource for both the United States and the world. Recent discoveries of methane hydrate in arctic and deep-water marine environments have highlighted the need for a better understanding of this substance as a natural storehouse of carbon and a potential energy resource. Methane hydrate science has advanced steadily over the past decade, and commercial-scale production of natural gas from methane hydrate deposits is growing more viable at each step. Experimental, modeling, and field-based studies are underway to advance our understanding of this fascinating resource.
The Natural Gas Hydrate Research and Development Program supported by the U.S. Department of Energy’s Office of Fossil Energy focuses on assessing gas hydrate as a future energy resource and as a dynamic constituent of the global environment. The program has found success both in Alaska and in the Gulf of Mexico in recent years, where drilling programs have demonstrated safe operations, validated a new approach to gas hydrate exploration based on integration of direct geophysical detection with assessment of components of gas hydrate petroleum system, and furthered the understanding of gas hydrate reservoir response to both depressurization and chemical exchange. The Fossil Energy program continues to pursue a series of in situ testing projects designed to investigate and characterize gas hydrate reservoir behavior.
At present, depressurization (accomplished by the evacuation of the wellbore and the removal of moveable fluids from the gas hydrate-bearing reservoir via standard pumping methods) is the most widely favored approach for the production of gas from gas hydrate reservoirs. Depressurization benefits include overall simplicity, with recent field tests and numerical modeling techniques that have returned positive results. To supplement this research into gas hydrate production, NETL R&IC investigate the potential of an alternative production method including CO2-CH4 exchange, employing the injection of CO2, a process that can simultaneously release CH4 while sequestering the CO2 in solid and stable CO2 hydrate (http://www.netl.doe.gov/technologies/oil-gas/FutureSupply/MethaneHydrates/rd-program/ANSWell/co2_ch4exchange.html).
Production from gas hydrates faces significant challenges, such as geomechanical changes caused by hydrate dissociation. Specifically, the dissociation of gas hydrates could affect the structural integrity of unconsolidated hydrate-bearing sediments. Understanding the geomechanics of hydrate-bearing sediments is crucial in addressing potential geohazards caused by global warming. To quantify the response of hydrate-bearing soils under stress, it is essential that an analysis is completed using a suitable constitutive model.
In natural hydrate systems, permeability affects methane flux to the ocean; gas hydrate and free gas distribution; gas hydrate concentration and accumulation; and gas production efficiency from hydrate reservoirs. Permeability is a critical property for investigating hydrate-bearing sediments as a potential energy resource and as a risk to global climate change or large-scale submarine instabilities.