DOE/NETL Methane Hydrate Projects
Characterizing Baselines and Change in Gas Hydrate Systems using Electromagnetic (EM) Methods Last Reviewed June 2017

DE-FE0028972

Goal
The overall objectives of this work are (i) advance understanding of hydrate electrical conductivity as a function of sediment type and fluid content; (ii) quantify the conductivity changes associated with hydrate dissociation induced by increasing temperature or decreasing pressure; and (iii) collect baseline data sets in the field to illustrate the capabilities of the Vulcan instrument system, calibrate the relationship between conductivity inversions and well logs, and provide quantitative constraints on hydrate volume in situ.

Phase 1 objectives: Understand the effect of grain size on methane hydrate conductivity. Assess the impact on methane hydrate conductivity of dissociation associated with (a) decompression and (b) increased temperature. Image the electrical conductivity structure of 2 or 3 prospects in the Gulf of Mexico (GoM) using the Vulcan marine Controlled Source ElectroMagnetic (CSEM) system.

Phase 2 objectives: Interpret the Vulcan inversions to obtain quantitative estimates of total hydrate volume.

Phase 3 objectives: Complete the integration of field interpretations, laboratory conductivity studies, and any available logging/coring results. Publicize results and facilitate commercial application of the technology.

Performers
The Regents of the University of California – San Diego (UCSD), Scripps Institute of Oceanography, La Jolla, CA 92093

Collaborators
United States Geological Survey (USGS), Menlo Park, CA 94025
Lawrence Livermore National Laboratory, (LLNL), Livermore, CA 94551

Background
In order to clarify the processes by which gas hydrate deposits are formed, maintained, and evolve within geologic systems, it is important to develop tools other than drilling, seismology, and geochemistry to study hydrate systems, both in the field and in the laboratory. Much progress has been made in our understanding of hydrate systems using the existing tools, but adding electrical conductivity cannot fail to increase our understanding of gas hydrate systems. Combined with appropriate models obtained from laboratory studies, CSEM measurements can help quantify the saturation and total volume of hydrate within a known or suspected deposit. By adding geometrical constraints obtained from seismic reflection data, tradeoffs between total volume and peak saturation can be resolved. Currently our laboratory models are limited to pure hydrate and hydrate+sand. It is important to expand this library to include silt and fluids to the list. Basic data such as these will also improve the interpretation of resistivity well logs. A critical part of the proposed work is to use laboratory measurements to characterize and quantify changes in electrical conductivity of hydrate systems during dissociation induced by production (lowering pressure) or environmental change (increasing temperature). Combined with repeat field measurements to collect CSEM data, observed changes in conductivity can thus be interpreted in terms of changes in hydrate volume and extent. It is possible that climate- or production-induced changes in hydrate content may generate a more observable signal in electrical conductivity than in seismic properties.

Impact
By examining the role of grain size and fluids, the work proposed here will expand the application of our data to more complicated natural systems, and will help take the interpretation of well logs from a largely qualitative approach to something more quantitative. By collecting field data in locations where logging while drilling (LWD) data have already been collected, and coring data are likely to be collected in the future, we can further refine our ability to improve the interpretation of logs.

Accomplishments (most recent listed first)

  • Researchers from LLNL and USGS collected a baseline set of electrical conductivity data from the conductivity cell, which was recently refurbished and installed at the USGS Gas Hydrate Laboratory at Menlo Park.

Current Status (June 2017)
In preparation for the collection of CSEM data in the Gulf of Mexico (GOM), UCSD began testing the Vulcan transmitter and receiver instrumentation systems. Researchers are also looking at extending the length of the towed receiver array system from 1,000 meters to 1,500 meters in order to get the required penetration over the Walker Ridge area in the GOM. Team members are coordinating with researchers at the University of Texas and Ohio State with regards to survey locations and tow line orientations. The research cruise to collect the CSEM data over methane hydrate prospective areas in the GOM is scheduled for June 26 to July 5 aboard the R/V Point Sur.

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

Project Cost Information
Phase 1 – DOE Contribution: $366,579, Performer Contribution: $180,484
Phase 2 – DOE Contribution: $116,986, Performer Contribution: $101,616
Phase 3 – DOE Contribution: $49,841, Performer Contribution: $80,399
Planned Total Funding–DOE Contribution: $533,406, Performer Contribution: $362,499

Contact Information:
NETL – Skip Pratt (skip.pratt@netl.doe.gov or 304-285-4396)
UCSD, Scripps Institute of Oceanography – Steve Constable (sconstable@ucsd.edu or 858-534-2409)

Additional Information:

Quarterly Research Performance Progress Report [PDF] January - March, 2017