Pressure coring a Gulf of Mexico deep-water turbidite gas hydrate reservoir: Initial results from The University of Texas–Gulf of Mexico 2-1 (UT-GOM2-1) Hydrate Pressure Coring Expedition
“…We set a constant seafloor temperature of 4°C and a constant basal heat flux of 50 mW/m 2 . This simulates a BHSZ at 460 mbsf at the ridge, close to the observation of 468 mbsf at GC 955 (Flemings et al., 2020). There is no flux of heat and fluid across the lateral sides of the domain.…”
Section: Testing the Conceptual Model With 2d Numerical Simulationssupporting
Methane hydrate is a crystalline, ice-like substance that is formed under high pressure and low temperature conditions along continental margins where sufficient methane is present (Sloan & Koh, 2007). Methane hydrate sequesters a vast amount of carbon globally, with the current estimate between ∼500 and 2,500 Gt (10 15 g) of carbon and ∼5-22% of the Earth's total organic carbon (
“…We set a constant seafloor temperature of 4°C and a constant basal heat flux of 50 mW/m 2 . This simulates a BHSZ at 460 mbsf at the ridge, close to the observation of 468 mbsf at GC 955 (Flemings et al., 2020). There is no flux of heat and fluid across the lateral sides of the domain.…”
Section: Testing the Conceptual Model With 2d Numerical Simulationssupporting
Methane hydrate is a crystalline, ice-like substance that is formed under high pressure and low temperature conditions along continental margins where sufficient methane is present (Sloan & Koh, 2007). Methane hydrate sequesters a vast amount of carbon globally, with the current estimate between ∼500 and 2,500 Gt (10 15 g) of carbon and ∼5-22% of the Earth's total organic carbon (
“… Figure 1 CT scan images of pressure cores at different times and scales. Figure ( a ) is a sectional view of a portion of core H005 5FB-3 scanned on board soon after the drilling of the pressure core, May 2017 29 ; figure ( b ) is a sectional view of the same pressure core scanned with the industrial CT scanner (the remaining segments of the 30-cm long pressure core after three cuts), Dec 2019; figure ( c ) is an overview of the mini-core (Sample #3, Feb 03, 2020) drilled from the left-hand portion of the core shown in ( b ); figure ( d ) is high-resolution image of the portion of Sample #3 (noted as D on c : Jan 31-Feb 03, 2020); figure ( e ) is high-resolution image of the portion of Sample #3 (noted as E on c : Feb 03–05, 2020); and figure ( f ) is high-resolution image of the portion of Sample #3 (noted as F on c : Feb 05–07, 2020). Scales in ( a ) and ( b ) are provided by the ruler; ( d ), ( e ), and ( f ) share the same scale bar; ( d ), ( e ), and ( f ) show raw CT images on the right and the same image with hydrate false-colored in blue.…”
Section: Resultsmentioning
confidence: 99%
“…The deposit is composed of interbedded sandy silt and clayey silt layers 57 . The hydrate saturation in sandy silts at this site ranges from 79 to 93% as determined by collecting the amount of gas during pressure core degassing and the pore water salinity is close to the seawater concentration 29 , 58 . Additional information about the pressure core such as the drilling process can be found in Ref.…”
Section: Introductionmentioning
confidence: 96%
“…However, there have been no direct observations of pore-scale hydrate occurrence in never-depressurized natural cores to support such interpretations on hydrate pore habits, mainly due to the technical complexity. This challenging task now becomes possible, as reported in this study, because of the recent development of the pressure core technique 20 – 29 and high-resolution micro-CT visualization of methane hydrate 30 , including previous CT studies on pressure cores at core scale 31 , 32 and high-resolution studies on THF and Xenon hydrate 33 , 34 in the laboratory.…”
Section: Introductionmentioning
confidence: 99%
“…Additional information about the pressure core such as the drilling process can be found in Ref. 28 , 29 . We developed a set of tools that allows sub-sampling mini-cores from the pressure core for micro-CT scans 59 , which we applied to core H005 5FB-3.…”
Both intra-pore hydrate morphology and inter-pore hydrate distribution influence the physical properties of hydrate-bearing sediments, yet there has been no pore-scale observations of hydrate habit under pressure in preserved pressure core samples so far. We present for the first time a pore-scale micro-CT study of natural hydrate-bearing cores that were acquired from Green Canyon Block 955 in UT-GOM2-1 Expedition and preserved within hydrate pressure–temperature stability conditions throughout sub-sampling and imaging processes. Measured hydrate saturation in the sub-samples, taken from units expected to have in-situ saturation of 80% or more, ranges from 3 ± 1% to 56 ± 11% as interpreted from micro-CT images. Pore-scale observations of gas hydrate in the sub-samples suggest that hydrate in silty sediments at the Gulf of Mexico is pore-invasive rather than particle displacive, and hydrate particles in these natural water-saturated samples are pore-filling with no evidence of grain-coating. Hydrate can form a connected 3D network and provide mechanical support for the sediments even without cementation. The technical breakthrough to directly visualize particle-level hydrate pore habits in natural sediments reported here sheds light on future investigations of pressure- and temperature-sensitive processes including hydrate-bearing sediments, dissolved gases, and other biochemical processes in the deep-sea environment.
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