In summer 2019, scientists from the USGS Gas Hydrates Project travelled from Woods Hole to the University of Texas (UT) to lead a deep-biosphere study of the microbiological communities associated with gas hydrate.
USGS Scientists Participate in a Gulf of Mexico Gas Hydrate Pressure Coring Project
This article is part of the August-September 2019 issue of the Sound Waves newsletter.
Study samples were retrieved from hundreds of meters below the seafloor of the northern Gulf of Mexico (GOM) during a 2017 gas hydrate pressure coring project led by the University of Texas with support from the U.S. Department of Energy (DOE).
Why pressure core a methane gas hydrate reservoir?
Methane gas hydrate, or simply “gas hydrate” here, is a solid form of methane and water that is stable at the elevated pressures and reduced temperatures found in sediments of permafrost and marine continental slopes. A given volume of gas hydrate can release up to 180 times that volume of methane gas at standard temperature and pressure. The USGS Gas Hydrate Project leads research into the environmental and energy implications of natural gas hydrate deposits.
Research on gas hydrate-bearing reservoirs often relies on seismic surveys, other geophysical imaging, and borehole logging, but critical properties such as reservoir permeability (how easily fluids and gas can flow through the reservoir during extraction of methane) can only be studied by making direct measurements on reservoir sediments. Conventional coring of reservoir sediments during ocean drilling programs allows the sediments to depressurize, destroying the gas hydrate, so the international gas hydrate community now recovers hydrate-bearing sediments using pressure coring. Pressure cores retain the pore pressure sediments experienced when they were in the seafloor (in situ pressure), and are cooled immediately after retrieval. Hydrate-bearing sediments retrieved by pressure coring can be tested at high pressure to extract information about in situ properties in the seafloor reservoir.
Gas Hydrate Research in the Northern Gulf of Mexico
The USGS Gas Hydrates Project has been participating in gas hydrate research in the northern Gulf of Mexico for two decades. Since 2000, the USGS has collaborated with DOE, Minerals Management Service (now the Bureau of Ocean Energy Management, BOEM), international partners, and an industry consortium to conduct extensive geophysical site surveys, site selection, and then drilling for expeditions in both 2005 (JIP I) and 2009 (JIP II). Timothy Collett (Central Energy Resources Science Center) was the scientific lead for the 2009 JIP II effort, which was the first to investigate the gas hydrate reservoir at Green Canyon Lease Block 955 (GC955). Logging-while-drilling at GC955 during JIP II revealed a 25 meter-thick interval filled with thin (15 to 120 centimeter-thick) gas hydrate-bearing sands interbedded with fine-grained muds. In 2013, Seth Haines (Central Energy Resources Science Center) and Patrick Hart (Pacific Coastal and Marine Science Center) conducted a detailed seismic survey at GC955. Pressure coring was conducted at the site in 2017 as part of the northern Gulf of Mexico hydrates investigation (GOM2), which is sponsored by DOE and led by Peter Flemings (UT). Timothy Collett served as a technical advisor aboard the drill ship during GOM2.
USGS Gas Hydrate Project Participation in GOM2 Science
Ongoing USGS research for GOM2 supports the goals of characterizing the physical and chemical properties of the gas hydrate reservoir and investigating the origin of methane stored in gas hydrate at GC955. Following the completion of the drilling expedition, USGS Gas Hydrates Project scientists Junbong Jang and William Waite (Woods Hole Coastal and Marine Science Center; WHCMSC) participated in the post-cruise dockside pressure core analysis at Port Fourchon, Louisiana in summer 2017. Building on the findings from those analyses, the USGS proposed to transport and analyze two 1.2-meter-long pressure cores at the WHCMSC Hydrate Pressure Core Analysis Laboratory (HyPrCAL), one of only three facilities in the U.S. that can routinely conduct suites of physical properties measurements on pressure cores. The cores arrived at WHCMSC in late 2018, and a collaboration planned for fall 2019 with researchers from UT, the Georgia Institute of Technology (Georgia Tech), and University of New Hampshire, will assess permeability of hydrate-bearing sediments and conduct benchtop-production tests to extract methane from the sediments.
The USGS has also helped organized a GOM2 study to better understand the microbial consortium in the gas hydrate reservoir. Microbial markers retained in the pressure cores can distinguish between methane generated within the hydrate reservoir and methane that has migrated to the reservoir from other locations. In summer 2019, Junbong Jang, assisted by William Waite and Sheng Dai (Georgia Tech), worked with UT researchers Stephen Phillips, Joshua O’Connell, and Addison Savage to mate the USGS biological chamber with four pressure cores stored at UT and to extract subsamples for microbiological analyses. Microbiologists Jennifer Glass (Georgia Tech), Rick Colwell and Jessica Buser (Oregon State University), and Brandi Reese (Texas A&M, Corpus Christi) curated the biological samples and prepared them for analysis. Some samples are being held at in situ gas hydrate stability conditions for extended incubation studies at Georgia Tech. Other samples will have DNA and RNA extracted for sequencing at Texas A&M Corpus Christi to establish which microbial communities were present in situ and identify the microbial functionality of those communities with a particular focus on whether they were methanogens capable of producing the methane stored in the GC955 gas hydrate.
Other Contributions to Pressure Coring Analysis
Pressure coring is now routine during gas hydrate resource studies that involve retrieval of hydrate-bearing sediments by drilling into reservoirs. Until recently, however, it has not been possible to routinely transport pressure cores to or within the U.S. Based on an engineering design from J. Carlos Santamarina (then at Georgia Tech) and with funding from DOE, the USGS Gas Hydrate Project organized the construction and U.S. Department of Transportation certification process for pressurized storage and transport chambers that are compatible with the community’s pressure core manipulation equipment. The USGS completed several chambers in 2017 and successfully used them for the first time in 2018 to transport pressure cores from UT to HyPrCAL at WHCMSC. Other U.S. and international laboratories are now adopting the same manufacturing and certification process to build additional pressure core chambers for upcoming projects, thereby expanding the number of research groups that can work with these critical samples. In preparation for anticipated pressure coring in the Alaskan North Slope gas hydrate reservoir through a collaboration with DOE, the Japan Oil, Gas and Metals National Corporation (JOGMEC), and British Petroleum Exploration (BP), the USGS will build eight more pressure core storage chambers in 2020.
The USGS Gas Hydrates Project work with pressure cores is supported by an Interagency Agreement with DOE (DE-FE0023495). This report was prepared as an account of work sponsored by an agency of the United States Government. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.