DE-FC26-06NT42960

Goal
The goal of this project is to improve the understanding of regional differences in gas hydrate systems from three perspectives: as an energy resource, as a geohazard, and as a long-term influence on global climate.

Performers
Rice University
University of Houston - Houston, TX

Background
Heterogeneity in the distribution of gas hydrate accumulations impacts all aspects of research into gas hydrate natural systems. The challenge is to delineate, understand, and appreciate these differences at the regional scale, where differences in in-situ concentrations are relevant to the importance of gas hydrate as a resource, geohazard, and factor in the carbon cycle. Some of the key questions that remain unanswered are:

• Why do regional heterogeneities in gas hydrate distribution occur?
• How can we detect them remotely?
• Where are concentrated gas hydrate accumulations likely to be found?
• How will heterogeneities affect strategies for production of natural gas from hydrates?
• How would different distributions respond to temperature perturbations?

Potential Impact
This project will result in enhanced understanding of:

• the processes controlling the behavior of the marine hydrate system,
• the potential viability of proposed methodologies for the production of natural gas from methane hydrates and,
• improved safety practices during offshore drilling through a better understanding of seafloor and wellbore stability in the presence of hydrates.

The work may also result in advanced methodologies for remote quantification of hydrate accumulation through novel techniques for evaluation of geophysical imaging.

Accomplishments
Phase 1 of this study was brief in duration and focused on the full development of a revised statement of work for subsequent project phases that incorporated advances and new data produced since the applicant’s proposal was received. The development occurred through detailed planning and discussion with NETL personnel as well as through cooperation with other ongoing NETL funded research projects. In addition, the performers reviewed and selected the appropriate data sets for use in this study. This component of the effort was completed in March 2007. The performer provided a detailed plan for conducting activities under the project. Following provision of this information, a formal statement of project objectives and associated budget was negotiated between Rice and DOE to carry out the Phases 2 – 5 of the project.

Phase 2 of the project initialized in June 2007. Work under the remaining project phases (2-5) involves sustained efforts within five specific research areas over the course of the project. The value of the work under each area will be evaluated at the end of each year long phase before being continued to subsequent phases. Work to date under Phase 2 has included the following results:

• Participation in the DOE-NETL Peer Review of Methane Hydrate Research and Development Sept 18-20, 2007 in Golden CO. Researchers presented results to date and planned efforts in each of the five major research areas within the project as well as providing descriptions of overall project progress and management strategy.
• Initiated efforts in measuring iodine concentrations in the pore waters from various hydrate systems. This data will be used in conjunction with organic carbon and metal profiling for use in trying to constrain models for gas hydrate formation.
• Completed 1-D analysis of the perceived affect of the oxidation of methane by sulfate on gas hydrate accumulation and the value of the data as an indicator of methane flux. This work resulted in development of a theorized relationship between the sulfate-methane transition (SMT) and average gas hydrate saturation (AGHs) for systems dominated by methane migration from deeper sources. The relationship is explained by a one-dimensional numerical model that simulates gas hydrate accumulation in marine sediments. Higher methane fluxes result in shallow SMT depths and high AGHS, while lower methane fluxes result in deep SMTs and low AGHS.
• Initiated numerical modeling of potential methodologies for production of natural gas from hydrates by first exposing the numerical simulator to hydrate reservoir simulation exercises of increasing complexity as defined by the separate DOE-NETL funded effort referred to as the Hydrate Code Comparison Study. Work on the code comparison problems is intended to strengthen the overall code capabilities prior to using the model for comparative evaluation of potential production methodologies.
• Initiated assessment of the geomechanical properties of sediments from hydrate areas through laboratory experiments at Rice and comparison of the laboratory permeability measurements with NMR logging data. Efforts are underway to compile sediment strength properties from existing studies for the sediment properties database.
• First-order numerical models of seafloor stability are being constructed with sensitivity analyses planned to identify the conditions that drive failure.

Summary
This study will address these issues with an integrated cross disciplinary research team that will:

• Collect key data concerning hydrocarbon fluxes at key study sites;
• Use these and existing data to build numerical models that can explain gas hydrate variance at these sites;
• Simulate how natural gas could be produced from hydrate locations under different production strategies;
• Collect sediment property data required for constraining fluxes, production simulations, and assessing sediment, seafloor and wellbore stability in areas of hydrate occurrence
• Investigate enhanced methods for remotely quantifying heterogeneities in gas hydrate and free gas distributions.

While this effort generally focuses on the key study sites where the team has access to data and key parameters that can be measured or constrained, the ultimate aim is to produce methodologies and models that are universally applicable to assessing the resource and/or geohazard potential of any hydrate accumulation.

Beginning with Phase 2 and continuing throughout the remainder of the project the effort will work toward the collection of data and the development of conceptual models that explain the variation in gas hydrate concentration. The performers will construct numerical models that explain and predict regional-scale gas hydrate heterogeneity in two and three dimensions with a minimal number of “free parameters.” These models will then be used to simulate hydrocarbon production from various types of gas hydrate systems, in order to establish the most promising resource characteristics from a commercial standpoint. The same models will also be employed to simulate how different gas hydrate systems respond to perturbations in their stability conditions—most importantly, temperature changes—in order to assess the potential impacts of hot drilling fluids on seafloor stability and well stability. The performers will also develop geophysical approaches that enable remote quantification of heterogeneous gas hydrate accumulations so that they can be characterized with minimal drilling and coring costs.

Current Status
Phase 1 has been completed and Phase 2 work was initiated in June 2007 based on the finalized statement of work. The remaining project effort includes four one-year phases (Phases 2-5) which will consist of ongoing efforts in each of the research areas outlined in the summary section above. Efforts within Phase 2 are well underway and the progress and overall value of results from the effort within each of the five major research areas and the project as a whole will be formally evaluated at the end of the 12 month Phase 2 when it is reached in mid June 2008. Accomplishments to date from project Phase 2 are summarized in the Results section above and full detail can be found in the quarterly progress reports for the project (links to project reports is provided in the Additional Information section below).

Project Start: October 1, 2006
Project End: April 30, 2010

DOE Contribution: $1,270,153
Performer Contribution: $448,099

Contact Information:
NETL – Rick Baker (richard.baker@netl.doe.gov or 304-285-4714)
Rice University – Dr. George Hirasaki (gjh@rice.edu or 713-348-5416)

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].

2008 ICGH Paper - Relating Gas Hydrate Saturation to Depth of Sulfate-Methane Transition [PDF]

2008 ICGH Paper - Effect of Overpressure on Gas Hydrate Distribution [PDF]

2008 ICGH Paper - Production Strategies for Marine Hydrate Reservoirs [PDF]

Topical Report [PDF-3.92MB] - June, 2008

Quarterly Report [PDF-1.68MB] - January 1, 2008 - March 31, 2008

Quarterly Report [PDF-429KB] - October 1, 2007 - December 31, 2007

Quarterly Report [PDF-417KB] - July 1, 2007 - September 31, 2007

American Journal of Science Article [PDF-1.66MB] - June, 2007

Quarterly Report [PDF-395KB] - April 1, 2007 - June 30, 2007

Kick-off meeting presentation [PDF-701KB] - January 9, 2007