Laboratory Studies in Support of Characterization of Recoverable Resources From Methane Hydrate Deposits

Project Number

ESD05-048

Last Reviewed Dated

Thu, 05/10/2012 - 12:00

Goal

The project is bringing new laboratory measurements and evaluation techniques to bear on the difficult problems of characterization and gas recovery from methane hydrate deposits.

Performer(s)

Lawrence Berkeley National Laboratory, Berkeley, CA 94720

Background

LBNL is performing laboratory tests to provide data to support the characterization and development of methane hydrate deposits. Major areas of research underway include hydrologic measurements, combined geomechanical/geophysical measurements, and synthetic hydrate formation studies.

HYDROLOGIC MEASUREMENTS

Relatively little research has been done to experimentally determine permeability (a measure of the resistance to fluid flow through a medium) in hydrate-bearing sediments (HBS) or relative permeability (the effect of another phase that interferes with flow) in a three phase—hydrate/water/gas—system where the hydrate habit (how the hydrate occupies space) is not well understood. The presence of hydrate in the pore space will hinder flow and alter the gas/water capillary pressure, affecting the relative amounts of each phase present in the pore space. Numerical models account for relative permeability in a hydrate/water/gas system based on estimations and idealizations; however, these estimations are not currently based on measurements.

LBNL is performing experimental tests to provide data that will allow for numerical inversion of relative permeability relationships. In performing these inversions, LBNL has found that unique relative permeability functions have not been obtainable without knowledge of how hydrate affects capillary pressure functions. In hydrate-bearing porous media, pore geometry, surface wettability, interfacial tension, and fluid phase saturations affect capillary pressure. LBNL has developed a technique to continuously measure gas/water capillary pressure in hydrate-bearing porous media, and is making measurements to understand this important effect.

GEOMECHANICAL/GEOPHYSICAL MEASUREMENTS

It is important to understand the effect of hydrates on the geomechanical strength of hydrate-bearing sediments because offshore oil and gas development requires placement of equipment on the seafloor. The strength of the sediments will change with the amount of hydrate present, and the relationship between sediment strength and hydrate abundance is poorly understood. Numerical simulators have been constructed that can compute the effects of hydrate formation or dissociation on sediment strength, but they depend on measurements of these strength parameters.

LBNL is performing tests on samples containing methane hydrates in order to better understand and measure the geomechanical behavior of oceanic HBS as they undergo thermo-mechanical changes. Concurrent x-ray computed tomography (CT) scanning to quantify sample uniformity and observe failure modes, and geophysical (acoustic) property measurements are being made in an attempt to relate the stress in the samples to field measureable properties.

SYNTHETIC HYDRATE FORMATION STUDIES

LBNL is developing, testing, and refining concepts and techniques for the formation of hydrate bearing samples for laboratory use and testing that are more representative of naturally occurring hydrate-bearing sediments.

IMPACT OF THIS RESEARCH

Primary benefits of this lab-based research are improved empirical relationships between experimental and theoretical relative permeability, which will result in improvements to hydrologic and reservoir engineering applications, and determination of the envelope of HBS stability under conditions typical of those associated with the construction and operation of offshore platforms.

Accomplishments (most recent listed first)

First confirmation that CT x-ray scanning can be used to differentiate hydrates from water-ice.
Construction and operation of a field-portable CT scanner.
Development of techniques for production of hydrates of desired saturation in a porous medium; measuring capillary pressure and relative permeability in HBS; a more rapid technique for estimating relative permeability and capillary pressure relationships; and simultaneously measuring geomechanical and geophysical properties of hydrate-bearing sediments while investigating sample structure using CT.
Development of new tools for the study of geomechanical/geophysical properties of HBS CT scanned samples of national interest, and provision of data to researchers performing other tests on field-collected hydrate-bearing samples.
Completion of preliminary study of migration tendencies of hydrate within sediment samples under stable conditions within the hydrate stability zone and initiation of efforts to study this phenomenon.
Completion of experimental study analyzing the effects of water flooding of hydrate cemented sand samples using resonance measurements and identifying the implications for measurement of sample physical properties.
Completion of experimental studies that analyzed various hydrate formation techniques and their ability to generate samples with uniform hydrate distribution within the host sediments.
Dissemination of project findings through publication of journal articles and presentation at technical/scientific conferences.

X-ray image of relative permeability vessel (top), indicated changes in saturation over time at 4 locations during a waterflood of an hydrate-bearing sample (left), and characteristic hydrate saturations from 9 tests (right).

Gas relative permeabilities for dry, moist, frozen, and hydrate-bearing sand as a function of gas saturation for three porous media at three initial water saturations, and model predictions.

Measured and modeled water saturation for a single drainage step (green dot to red dot).

Triaxial test results (top right), density (from x-ray CT-top left) and wave velocities (bottom) for shakedown tests on tetrahydrofuran hydrate-bearing sand samples.

Current Status

Activity under this FWP is complete. Information documenting the results of the effort can be found in the many published papers cited in the Methane Hydrate Program – Projects Reports Bibliography [PDF]. New work in this research area is ongoing at LBNL under ESD12-011.

Project Start

Tue, 07/01/2003 - 12:00

Project End

Mon, 12/31/2012 - 12:00

DOE Contribution

$1,690,000

Performer Contribution

Contact Information

NETL – Richard Baker (Richard.Baker@netl.doe.gov or 304-285-4714)
LBNL –Timothy J. Kneafsey (tjkneafsev@lbl.gov or 510-486-4414)

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]. Additional LBNL hydrate-related publications can also be found on the LBNL Gas Hydrate Publications webpage [external site].

Project Report - Effect of Water Flooding on Hydrate Cemented Sand Samples [PDF-534KB] - July, 2010

Project Report - Hydrate Formation Method Evaluation [PDF-1.93MB] - July, 2010

Project Report - Hydrate Migration Study [PDF-1.51MB] - July, 2010

FY2009 Annual Report [PDF-387KB]

Quarterly Progress Report – January - March 2008 [PDF-498KB]

2008 Hydrate Peer Review [PDF-4.49MB]

Fire in the Ice article [PDF-942KB] "Understanding Methane Hydrate Behavior Using X-Ray Computed Tomography" by Tim Kneafsey, George Moridis, Barry Freifeld, Liviu Tomutsa and Yongkoo Seol (Lawrence Berkeley National Laboratory), and Chuck Taylor (National Energy Technology Laboratory) - Winter edition 2005, pg. 1