DOE/NETL Methane Hydrate Projects
Impact of Clays on the Compressibility and Permeability of Sands During Methane Extraction from Gas Hydrate Last Reviewed June 2017

DE-FE0028966 / DE-FE0026166

Goal
The goal of the project - being jointly performed under projects with Louisiana State University (DE-FE0028966) and the US Geological Survey (DE-FE0026166) - is to provide a quantitative basis for reservoir models to account for the impact of clays and other fine-grained material ("fines") on reservoir compressibility and permeability, two key factors in controlling the flow of gas and fluids toward a gas hydrate production well.

Performers
Louisiana State University (LSU), Baton Rouge, LA
US Geological Survey (USGS), Woods Hole, MA

Background
The quantity of methane potentially recoverable from gas hydrate is large enough to motivate federally-supported production tests in several countries, which in turn motivates studies of reservoir production efficiency. Evaluating long-term production well viability involves modeling permeability evolution in the reservoir sediments around the production well because processes reducing the flow of gas into the production well also reduce the long-term economic viability of the well. Fine particles, such as clays, exist nearly ubiquitously in the permafrost and marine settings that typically host gas hydrate, and fines reacting to fluid flow by migrating and clogging pore throats can reduce flow toward the production well. Many fines are sensitive to variations in pore-fluid chemistry, swelling in reaction to in situ pore brine being displaced by fresh water liberated from hydrates during dissociation.

Additionally, fine particles tend to collect at gas/water interfaces created by the multiphase flow of gas and water. Thus, as methane and fresh water flow from the hydrate-dissociation front toward the production well, fine particles in the reservoir sands, interbedded fine-grained layers, and seal layers can be swelled, migrated (or both), potentially clogging pathways and limiting flow to the production well.

Impact
This project is expected to result in both increases in fundamental scientific understanding of hydrate system behavior during production and site specific impacts related to specific potential production sites offshore India by the National Gas Hydrate Program (of India) - NGHP.

Site-specific impact: Results from this research directly inform DOE-funded reservoir modeling work being undertaken for the most promising NGHP field sites. Sediment compressibility and permeability are two of the three highest-priority parameters (the third being sediment strength) for DOE’s reservoir modeling in preparation for an NGHP production test.

Ongoing work at Japan’s Advanced Industrial Science and Technology laboratory (AIST) and USGS on NGHP pressure cores is not designed to quantify how compressibility and permeability in the presence of hydrate change as the in situ pore-water brine continues to be displaced by the gas and fresh water produced during hydrate dissociation. The pressure core studies are also unable to distinguish whether the compressibility and permeability changes are due to the swelling or the migration of fines. This specific research fills that need, providing modelers at DOE and elsewhere with information on how reservoir compressibility and permeability are likely to evolve over time in the NGHP areas of interest.

Fundamental issues of global impact: To benefit production assessments of hydrate-rich systems elsewhere in the world, this research includes a systematic study of common fines and their impact on compressibility and permeability over a controlled range of concentration in sandy sediment. The matrix of experiments covering the range of common fines and fines concentration in sands will be used to build a results database that can be used to estimate property changes in hydrate-bearing sand targeted for production. The database would be most useful once a site has been cored, with XRD analysis to reveal the fines types and concentrations.

A second global scientific impact of the research will be enhanced understanding of fracturing due to breaking clogs that form due to fines migration. Quantifying the controlling parameters for this phenomenon provides guidance on a reservoir’s permeability evolution; in addition to providing a mechanism for explaining permeability drops and rebounds that may occur during production, clog fracturing has the potential to cause long-term permeability increases as fractures remain at least partly open once formed by this process.

Accomplishments (most recent listed first)

  • Acquired and completed index property analyses on conventional core material from India’s 2015 National Gas Hydrate Field Program (NGHP-02). Completed development/acquisition of equipment needed for microfluidic visualization of NGHP-02 fines.
  • Completed liquid and plastic limit tests (basis for electrical sensitivity) for end member fines using deionized water, brine, and kerosene.
  • Initiation of sedimentation tests to evaluate impact of salinity on sediment fabric.
  • Completion of initial compression tests on fines in a variety of pore fluids focused on dependence of compressibility on pore water salinity.
  • Completed fabrication of initial 2D micromodels and associated imaging systems for use in assessment of migration of fines, potential for clogging, and impacts on system permeability.

Current Status (June 2017)
Efforts at USGS will shift from micromodel equipment acquisition to performance of micro-visualization experiments using NGHP-02 samples and investigation of the mechanical contribution of NGHP-02 fines to clogging through use of imaging and measurement of the evolution of pressure and flow parameters. LSU researchers will move into investigation of the impact of pore fluid chemistry on clogging potential of endmember fines, as well as 3D visualization of clogging and clog fracturing, and investigation of the dependence of these on endmember fine types.

Project Start: October 1, 2016
Project End: September 30, 2019

DOE Contribution: $338,289 (LSU - $269,473; USGS – $68,816)
Performer Contribution: $86,888

Contact Information
NETL – Richard Baker (richard.baker@netl.doe.gov)
LSU – Dr. Shengli Chen (shenglichen@lsu.edu) and Dr. Jongwon Jung (jjung@lsu.edu)
USGS – Dr. William Waite (wwaite@usgs.gov)

Additional Information:

Louisiana State University Quarterly Research Progress Report [PDF] April - June, 2017

Louisiana State University Quarterly Research Progress Report [PDF] January - March, 2017

Louisiana State University Quarterly Research Progress Report [PDF] October - December, 2016