DOE/NETL METHANE HYDRATE PROJECTS
 
Mechanisms for Methane Transport and Hydrate Accumulation in Coarse-Grained Reservoirs Last Reviewed 12/24/2013

DE-FE0013919

Goal
The project goal is to evaluate whether the transport of methane, and the specific mechanism by which it is transported, are the primary controls on the development of persistent, massive hydrate accumulations in deep sediments below the seabed. The dissolved methane flux and time required to develop the accumulations observed at WR 313 by long-distance updip migration will be studied and defined within the scope of this research. Researchers will also determine whether there is enough methane in the dissolved phase in the fine-grained sediments to form the observed hydrate deposits or whether a gas phase is present and, if so, what the conditions are for three-phase equilibrium.

Performers
University of Texas at Austin, Austin, TX 78713-7726
Ohio State University, Columbus, OH 43210
Lamont-Doherty Earth Observatory (Columbia University), Palisades, NY 10964

Background
Massive hydrate deposits, defined as thick (>5 feet) accumulations of high hydrate saturation (>50 percent), have been encountered in many regions worldwide. This project will focus specifically on accumulations found at Walker Ridge Block 313 in the northern Gulf of Mexico during the Gulf of Mexico Gas Hydrate Joint Industry Project Leg 2. Hydrates may be thought of broadly within a petroleum systems framework, requiring a methane source, migration mechanisms, a reservoir, and an appropriate seal. Hydrate reservoirs and seals are defined by thermodynamics rather than buoyancy as in the case of conventional oil and gas. Hydrates form most easily within coarse-grained sediments within the methane hydrate stability zone, the depth interval in which pressure and temperature favor hydrate as the stable phase. Methane sources may include microbial activity as well as thermogenic sources. The focus will be on migration mechanisms in marine hydrate reservoirs as they represent some of the least understood processes in hydrate systems, but at the same time represent a crucial link between methane generation sites and hydrate reservoirs.

Potential Impact
Successful completion of this project will provide valuable insight into conditions necessary for the development of massive gas hydrate accumulations and the role of free gas in their persistence. This, in turn, will advance understanding of the transport and fate of methane in the subsurface; carbon cycling associated with hydrates; and role of a free gas phase in the formation and persistence of hydrate deposits.

Accomplishments
This is a new project awarded on October 1, 2013.

Current Status (December 2013)
Project personnel have begun modifying an existing reservoir model for hydrate formation and dissociation in porous media (Sun and Mohanty, 2006). The methane equilibrium calculation will be modified to include changes in methane solubility due to dissolved salt following the method of Handa (1990). The mass conservation calculation will be modified to include sedimentation, burial, and changes in porosity over time following the method of Bhatnagar et al. (2007). The initial conditions will be modified to allow specification of heterogeneous properties (e.g., porosity) throughout the model domain. The boundary conditions will be modified to allow specification of seafloor sedimentation rate and fluid flux.

Project Start: October 1, 2013
Project End: September 30, 2017

Project Cost Information:
DOE Contribution: $1,679,137
Performer Contribution: $448,001

Contact Information
NETL – John Terneus (John.Terneus@netl.doe.gov or 304-285-4254)
University of Texas at Austin – Hugh Daigle (daigle@austin.utexas.edu or 512-471-3775)

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