DOE/NETL Methane Hydrate Projects
 
Hydrate Evolution in Response to Ongoing Environmental Shifts Last Reviewed 6/9/2014

DE-FE0013565

Goal
The goal of this project is to create models that will be used to improve forecasts of slope stability and pockmark development, which could prevent disruptions of hydrate reserves and possible release of hydrates into the atmosphere.

Performers
University of Oregon, Eugene, OR 97403-5219

Background
Natural gas hydrate reservoirs are dynamic systems that evolve gradually but can also decompose abruptly resulting in submarine slope failure and pockmark formation. Both the accelerated exploitation of unconventional hydrocarbon reserves and environmental changes can increase the potential for enhanced hydrate dissociation that could lead to methane release. Model simulations are capable of approximating bulk reservoir characteristics, but these efforts must be complemented and enhanced by more finely resolved treatments that account for underlying microscale effects. Emerging developments in our knowledge of deposit variability can lead to further advances in mechanical models of slope stability that have been restricted to describing interactions with laterally homogeneous or slowly varying hydrate reservoirs and rate-independent friction. More sophisticated and physically realistic models updated with information about slip instabilities along tectonic faults can be extended to include the dynamic feedback resulting from fluid pressurization, dilatancy, and phase changes. Studying essential physical interactions over a broad range of time- and length-scales can help researchers predict the potential of hydrate reservoirs to transform into geohazards that could threaten commercial infrastructure and damage environmental systems.

Impact
Methane hydrates in arctic and deep-water deposits are crucial components of potential future energy supplies and a potent store of greenhouse gases. As hydrates evolve in response to ongoing environmental shifts, researchers must evaluate the potential for hydrate resources to be transformed into geohazards. This project will markedly advance our understanding of how hydrate anomalies develop and the potential for environmental forcing to cause them to dissociate and disrupt sedimentary structures. The project models will improve forecasts of slope failure and the development of gas-escape features that would diminish hydrocarbon reserves, release greenhouse gasses, and pose threats to energy infrastructure.

Accomplishments
Researchers have made progress on the packing algorithm for the code and have begun to test it against actual porosity measurements. Model predictions will be compared to literature data of well-characterized sediments. Governing equations for a simple model of radially-symmetric flow, hydrate formation, and brine injection in porous conduit were derived and will be coded in MATLAB. 

Current Status (June 2014)
Researchers are examining the influence of sediment properties on gas solubility within the hydrate stability zone. A MATLAB code capable of generating three-dimensional random packings of spherical particles with prescribed particle-size distributions has been developed. The code can take two-dimensional slices through a synthetic porous medium and calculate porosity and specific surface area for planned future comparison against empirical data with the same particle-size distributions. At present, only two-dimensional approximations to the solubility calculation have been implemented. The team is also studying how slope stability within the hydrate stability zone can be affected using a preliminary model that determines the time over which a given magnitude of consolidation must occur to cause a slope to become unstable.

Project Start: 01/01/2014
Project End: 12/31/2015

DOE Contribution: $276,804
Performer Contribution: $ 71,740

Contact Information:
NETL – Sandy McSurdy (sandra.mcsurdy@netl.doe.gov or 412-386-4533)
University of Oregon – Dr. Alan Rempel (rempel@uoregon.edu or 541-346-6316)

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