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Abstract

AAPG Bulletin, V. 104, No. 9 (September 2020), P. 1877-1901.

Copyright ©2020. The American Association of Petroleum Geologists. All rights reserved.

DOI: 10.1306/02262019036

Pressure coring operations during The University of Texas-Gulf of Mexico 2-1 (UT-GOM2-1) Hydrate Pressure Coring Expedition in Green Canyon Block 955, northern Gulf of Mexico

Carla Thomas,1 Stephen C. Phillips,2 Peter B. Flemings,3 Manasij Santra,4 Helen Hammon,5 Timothy S. Collett,6 Ann E. Cook,7 Tom Pettigrew,8 Mike Mimitz,9 Melanie Holland,10 and Peter Schultheiss11

1Institute for Geophysics, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas; [email protected]
2Institute for Geophysics, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas; [email protected]
3Institute for Geophysics and Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas; [email protected]
4Institute for Geophysics, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas; [email protected]
5Institute for Geophysics and Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas; [email protected]
6US Geological Survey (USGS) Central Energy Resources Science Center, Denver Federal Center, Denver, Colorado; [email protected]
7School of Earth Science, The Ohio State University, Columbus, Ohio; [email protected]
8Pettigrew Engineering, PLLC, Milam, Texas; [email protected]
9Geotek Coring, Inc., Salt Lake City, Utah; [email protected]
10Geotek, Ltd., Daventry, United Kingdom; [email protected]
11Geotek, Ltd., Daventry, United Kingdom; [email protected]

ABSTRACT

In May 2017, The University of Texas Hydrate Pressure Coring Expedition Gulf of Mexico 2-1 (UT-GOM2-1) drilled two adjacent holes in Green Canyon Block 955 in the deep-water Gulf of Mexico as part of The University of Texas at Austin and US Department of Energy Deepwater Methane Hydrate Characterization and Scientific Assessment. Expedition operations included testing two configurations of a rotary pressure-coring tool in a gas hydrate–bearing formation. In the first hole, an extended core barrel (cutting shoe) configuration of the Pressure Coring Tool with Ball Valve (PCTB-CS) was deployed, and in the second hole, the PCTB face bit configuration (PCTB-FB) was deployed. The PCTB-CS successfully recovered and maintained pressure for only one core out of eight deployments. A series of incremental modifications were made during and after the PCTB-CS deployment period that impacted the operations of the subsequent PCTB-FB deployments. Thus, in the second hole, the PCTB-FB successfully recovered and maintained pressure within the hydrate stability zone for 11 cores out of 13 deployments. The PCTB cored gas hydrate–bearing sandy silt interbedded with non–hydrate-bearing clayey silt within the main reservoir. The PCTB also recovered long intervals of unbroken, high-quality core with preserved sedimentary structures. We recovered one pressure core 130 m (437 ft) above the main hydrate reservoir in the silty clay. Pressure coring is the only available technology for recovering intact cores from sediment that is normally disturbed by gas expansion, dissolution, or dissociation; this allows a wide range of scientific measurements to be obtained with minimal disturbance to the core sediment fabric. Analysis of pressure cores has the potential to illuminate the in situ properties, gas saturation, and gas composition of a wide range of reservoirs including unconventional shale systems.

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