DE-FC26-06NT42963

Goal
The goal is to develop observational and experimental data that can provide a better understanding of the basic mechanisms at work in a methane hydrate reservoir that is under production. To this end, a thorough physical understanding of underlying phenomena associated with methane hydrate production will be acquired through unique multi-scale experiments and associated analyses. In addition, one or more mathematical models that account for the observed phenomena and provide insights that may help to optimize methane hydrate production methods will be developed.

Performers
Georgia Tech Research Corporation, Atlanta, Georgia 30332
Oak Ridge National Laboratory (ORNL), Oak Ridge, Tennessee 37831

Background
Gas hydrates constitutes an attractive and potentially large source of energy. A good assessment of methane production strategies and the subsequent design of production operations cannot be achieved without appropriate information on hydrate-sediment interaction and changes in the physical properties of hydrates during formation and dissociation. There are many gaps in our knowledge of gas hydrates that must be filled before we can develop technical and economically viable strategies for producing methane from gas hydrate reservoirs.

Methane hydrate production strategies will be affected by many factors. These include hydrate formation history within sediments (affects pore percolation and all forms of conduction), the hydrate itself within the pore space, subsequent gas production and recovery from porous networks, and the geomechanical evolution of the granular framework of the reservoir matrix during production. The prediction of gas recovery rates and volume of gas produced for different reservoirs as well as optimal exploitation design, rely on our understanding of the phenomena taking place during hydrate formation and dissociation. While temperature and pressure-controlled production approaches have been considered, all forms of energy mechanisms (including chemical and electromagnetic) and associated energy combinations within the reservoir should be explored as part of a broad search for optimal production strategies. The comprehensive physical understanding of ongoing processes must be properly captured in mathematical models that accurately describe the equilibrium and kinetic behavior of hydrates in sediments. These models can then be used to evaluate, design, and monitor/control gas production strategies. An accurate mathematical description is key, providing an accurate assessment of the production potential of hydrate deposits and the economic viability of their development. The interpretation of physical model results and the development of analytical models must recognize scaling conditions, similarity laws, and the coexistence of multi-scale processes. Finally, the availability of proper information and reliable models will support the assessment of the environmental impact of production operations in order to prevent the implementation of unacceptable production strategies.

Experiments will be conducted at several scales, beginning with 1-D (nanometer) focusing on single mineral substrates to 2-D (millimeter) porous networks in a single plane and concluding with a 3-D (meter) reservoir model using a sediment column. These experiments will look at physical (pressure), chemical, thermal and electromagnetic energies as well as some combinations of these energies. Different minerals will be used in 1-D experiments, different grain sizes in the 2-D experiments and different grain sized/sediment mixtures in the 3-D experiments. The main advantage of the proposed multi-scale approach is the identification of fundamental processes that can be recognized as possibly governing the macroscale process of methane production from hydrates.

Potential Impact
The data gathered here and the models developed may find application with other NETL methane hydrate projects, especially those involving computer reservoir simulations. This research will increase our understanding of the response of methane hydrates to production stimulation and the actions and reactions of released energy within the reservoir.

Accomplishments
The 1-D test chamber and associated instrumentation was built in the spring of 2007 and preliminary studies involved sequential tests using various pore fluids to simulate fresh to saline water. Data gathered during hydrate formation and dissociation include pressure, temperature, both mechanical and electrical impedance, and digital photography. Preliminary test results using the 1-D test chamber are available in the project’s yearly report (May 2007) [PDF-798KB]. Recently, analyses of freezing point depression and studies associated with hydrate contact bonding and strength have been done.

The 2D Chamber can be operated with either one or two 2-inch ID sapphire windows. It contains 6 accessible ports with electrical feed-through wires and optical feed-through. The cell is designed to withstand 30MPa gas pressure. A comprehensive FEM numerical simulation was conducted to verify the design of all components.

Based on the experienced gain with the 1-D cell and the versatility of this design, the 2-D pressure vessel chamber was designed and fabricated following a similar configuration to the 1-D cell, but with a more extensive set of feed throughs, ports and see-through sapphire end windows. Using the 2-D cell comparative studies have been completed on formation and dissociation in wetting versus non-wetting granular media.

Current Status
Additional experiments using the 1-D cell are ongoing in order to further refine the kinetic model. This includes studies of time-dependent hydrate formation and dissociation with both wetted and non-wetted surfaces, and experiments of contact level dissociation under different driving forces.

The study of formation and dissociation of hydrates in porous networks is underway. This work intends to provide insight into emergent phenomena that do not develop in the 1-D mineral surface system, and to introduce transport effects on hydrate dissociation in a controlled manner. A tentative test matrix has been designed to account for the various combinations of minerals, fluids, and energy forms to be tested. After hydrate formation within the 2-D monolayer, dissociation will be initiated and produced methane will be extracted from the center simulating a production well. The radial propagation of the dissociation front will be continuously monitored. Different sensor spacing and geometries will be investigated to obtain optimal data for inversion/modeling purposes. Data fro m the 2-D experiments were used to facilitate the development of a coupled thermodynamic and transport model for hydrate dissociation in sediments.

Granular monolayer system for 2-D studies - Prototype. Instrumentation ports can be seen in the glass substrates. Instrumentation will include multiple thermocouples, electrodes, and high resolution digital images.

Hydrate formation in wetting and non-wetting glass bead bed

Georgia Tech has developed and tested its new intrinsic kinetic model, which includes an experimentally-based pressure curve as an input which better reflects regulation of gas flow during the experiments. In addition, the properties of the gas are calculated using a Peng-Robinson equation of state in order to better capture the cooling effect of the chamber during gas evacuation. Simulation and experimental results for both 3-mm and 9-mm hydrate films have been completed. The new model does a better job in predicting the conditions inside the pressurized chamber within the kinetically-controlled dissociation regime for thinner hydrate film. For the thicker 9-mm film dissociation occurs at equilibrium until the film is about 3-mm thick. Results of these experiments can be found in the quarterly progress report for the period ending December 2007.

Development of a comprehensive numerical simulator has been initiated based on the robust Code_Bright Platform. This platform will allow simultaneously solving of all transport, mass balance and energy balance equations taking into consideration the inherent behavior of the sediment using the simple yet robust Cam-clay model. Analytical developments using the 1-D and 2-D cells will be incorporated in this simulator.

In July 2008, after presentation to DOE of successful project progress toward stated goals and objectives, this project entered into the third of its four project performance periods.

Project Start Date: October 1, 2006
Project End Date: September 30, 2010

Project Cost Information:
Phase 1 - DOE Contribution: $155,320, Performer Contribution: $49,170
Phase 2 - DOE Contribution: $184,260, Performer Contribution: $63,401
Phase 3 - DOE Contribution: $187,670, Performer Contribution: $60,003
Phase 4 - DOE Contribution: $260,336, Performer Contribution: $71,935
Planned Total Funding (if project continues through all project phases):
DOE Contribution: $787,586, Performer Contribution: $244,509

Contact Information:
NETL – John Terneus (John.Terneus@netl.doe.gov or 304-285-4254)
Georgia Tech – Carlos Santamarina (jcs@gatech.edu or 404-894-7605)

Additional Information
In addition to the information provided here, a full listing of project related publications and presentations as well as a listing of funded students can be found in the Methane Hydrate Program Bibliography [PDF].

Kick-off meeting presentation [PDF-2.43MB] - January 9, 2007

Technology Status Assessment [PDF-212KB] - May 2007

Quarterly Progress Report – October-December 2006 [PDF-96KB] - January 2007

Quarterly Progress Report – January-March 2007 [PDF-93KB] - March 2007

Yearly Report  [PDF-798KB] - May 2007

Quarterly Progress Report – April-June 2007 [PDF-975KB] - July 2007

Quarterly Progress Report – July-September 2007 [PDF-82KB] - November 2007

Quarterly Progress Report – October-December 2007 [PDF-429KB] - December 2007

Special Report – Pressure-Temperature Evolution During Thermal Stimulation [PDF-241KB] - December 2007

Quarterly Progress Report – January-March 2008 [PDF-2.01MB] - April 2008

Quarterly Progress Report – July-September 2008 [PDF-1.82MB] - October 2008