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David H. Mason

Publications and source records attributed to David H. Mason.

7 recordsLinked to original sources
USGS2011

Laboratory formation of non-cementing, methane hydrate-bearing sands

Naturally occurring hydrate-bearing sands often behave as though methane hydrate is acting as a load-bearing member of the sediment. Mimicking this behavior in laboratory samples with methane hydrate likely requires forming hydrate from methane dissolved in water. To hasten this formation process, we initially form hydrate in a free-gas-limited system, then form additional hydrate by circulating methane-supersaturated water through the sample. Though the dissolved-phase formation process can theoretically be enhanced by increasing the pore pressure and flow rate and lowering the sample temperature, a more fundamental concern is preventing clogs resulting from inadvertent methane bubble formation in the circulation lines. Clog prevention requires careful temperature control throughout the circulation loop.

Conference Paper↗
USGS2008

Physical properties of repressurized samples recovered during the 2006 National Gas Hydrate Program expedition offshore India

As part of an international cooperative research program, the U.S. Geological Survey (USGS) and researchers from the National Gas Hydrate Program (NGHP) of India are studying the physical properties of sediment recovered during the NGHP-01 cruise conducted offshore India during 2006. Here we report on index property, acoustic velocity, and triaxial shear test results for samples recovered from the Krishna-Godavari Basin. In addition, we discuss the effects of sample storage temperature, handling, and change in structure of fine-grained sediment. Although complex, sub-vertical planar gas-hydrate structures were observed in the silty clay to clayey silt samples prior to entering the Gas Hydrate And Sediment Test Laboratory Instrument (GHASTLI), the samples yielded little gas post test. This suggests most, if not all, gas hydrate dissociated during sample transfer. Mechanical properties of hydrate-bearing marine sediment are best measured by avoiding sample depressurization. By contrast, mechanical properties of hydrate-free sediments, that are shipped and stored at atmospheric pressure can be approximated by consolidating core material to the original in situ effective stress.

Conference Paper↗
USGS2008

Physical property studies in the USGS GHASTLI Laboratory

One of the many challenges in studying methane hydrate is that it is unstable at typical surface pressure and temperature conditions. To enable methane hydrates and hydrate-bearing sediments to be formed, analyzed, and experimented with, the National Energy Technology Laboratory (NETL), and the U.S. Geological Survey (USGS) in Woods Hole, MA collaborated in the development of the Gas Hydrate And Sediment Test Laboratory Instrument (GHASTLI). Over the past decade, the USGS has been operating GHASTLI and collaborating in the development of new sample handling tools and procedures, in an effort to improve our ability to analyze methane hydrate in the lab. These tools will enable hydrate researchers to more confidently link field studies (for example geophysics or drilling) with theoretical and predictive studies, leading to a better understanding of the geological conditions and processes that control the growth and concentration of natural gas hydrates, how hydrates affect the properties of the host sediments, and how the hydrate-sediment system changes when hydrate dissociates and releases the previously bound gas. To date, GHASTLI has been used to measure natural samples from ODP Leg 164 (Blake Ridge off the U.S. southeast Atlantic margin), Leg 204 (Hydrate Ridge off the Pacific Northwest margin) and the Mallik well (Mackenzie Delta in northwestern Canada). Additional samples in the queue for analysis are from the Chevron Joint Industry Project Experiment in the Gulf of Mexico and most recently, from IODP Leg 311 off Vancouver Island. Several foreign nations have asked whether GHASTLI will be available to analyze samples that might be recovered during national drilling programs. The ability to perform lab testing of hydrates within sediments is one of the unique capabilities of GHASTLI that separates it from other simulators at NETL and elsewhere.

Fire in the Ice: NETL Methane Hydrate Newsletter↗
USGS2006

Physical properties of pressurized sediment from hydrate ridge

As part of an ongoing laboratory study, preliminary acoustic, triaxial strength, and electrical resistivity results are presented from a test performed on a clayey silt sediment sample recovered from Site 1249 at the summit of southern Hydrate Ridge during Ocean Drilling Program Leg 204. The test specimen was stored and transported in two different methane-charged pressure vessels until it was tested using the Gas Hydrate and Sediment Test Laboratory Instrument (GHASTLI). Although gas hydrate may have existed in the core section immediately after recovery, little (if any) hydrate was present in the specimen during testing. We therefore present background physical property results for sediment that may have hosted gas hydrate in situ. Because we consolidated the test specimen in increments beyond its in situ stress state, we are able to present properties representative of similar but deeper subbottom sediment. The increased consolidation stress also helped to mitigate some, but not all, types of disturbance caused by the recovery process. P-wave velocities from 1.54 to 1.74 km/s varied linearly with consolidation stress, σ′c, up to 970 kPa (equivalent to ~160 meters below seafloor). Electrical resistivity was periodically measured by a Wenner array and varied between 1.0 and 2.8 Ωm. These values reflect both the pore water salinity and soft, fine-grained texture of the sediment. Shear behavior is consistent with the induced normally consolidated behavior of clayey silt.

Report↗
USGS2004

Strength and acoustic properties of Ottawa sand containing laboratory-formed methane gas hydrate

Although gas hydrate occurs in a wide variety of sediment types and is present and even pervasive at some locations on continental margins, little is known about how it forms naturally. Physical properties of the resultant gas hydrate-sediment mixtures, data needed for input into models that predict location and quantity of in situ hydrate are also lacking. Not only do properties of the host materials influence the type and quantity of hydrate formed and whether a particular deposit may be an economic resource or a geohazard, the properties of the natural sediment are also subsequently changed by the formation of gas hydrate in the pore space. The magnitude of the change is primarily related to the amount and the weighted inter-particle distribution of the hydrate deposits in relation to the actual sediment grains. Our goal is to understand the interaction between natural sediments and gas hydrate formation in order to quantify physical properties that are useful to predictive models.

Book chapter↗
USGS2003

GHASTLI — Determining physical properties of sediment containing natural and laboratory-formed gas hydrate

Gas-hydrate samples have been recovered at about 16 areas worldwide (Booth et al., 1996). However, gas hydrate is known to occur at about 50 locations on continental margins (Kvenvolden, 1993) and is certainly far more widespread so it may represent a potentially enormous energy resource (Kvenvolden, 1988). But adverse effects related to the presence of hydrate do occur. Gas hydrate appears to have caused slope instabilities along continental margins (Booth et al., 1994; Dillon et al., 1998; Mienert et al., 1998; Paull & Dillon, (Chapter 12; Twichell & Cooper, 2000) and it has also been responsible for drilling accidents (Yakushev and Collett, 1992). Uncontrolled release of methane could affect global climate (Chapter 11), because methane is 15–20 times more effective as a “greenhouse gas” than an equivalent concentration of carbon dioxide. Clearly, a knowledge of gas-hydrate properties is necessary to safely explore the possibility of energy recovery and to understand its past and future impact on the geosphere.

Book chapter↗