scholarly journals Supplemental Material: Diverse gas composition controls the Moby-Dick gas hydrate system in the Gulf of Mexico

2021 ◽  
Author(s):  
Alexey Portnov ◽  
et al.
Keyword(s):  
Gas Chromatography ◽  
Gulf Of Mexico ◽  
Gas Hydrate ◽  
Velocity Model ◽  
Well Log ◽  
Gas Composition ◽  
Geothermal Gradients ◽  
Moby Dick ◽  
The Public

Information about the sources and processing characteristics of the public seismic, well log, and gas chromatography data; and time-depth conversion parameters, velocity model, and calculations of geothermal gradients.<br>

scholarly journals Supplemental Material: Diverse gas composition controls the Moby-Dick gas hydrate system in the Gulf of Mexico

2021 ◽  
Author(s):  
Alexey Portnov ◽  
et al.
Keyword(s):  
Gas Chromatography ◽  
Gulf Of Mexico ◽  
Gas Hydrate ◽  
Velocity Model ◽  
Well Log ◽  
Gas Composition ◽  
Geothermal Gradients ◽  
Moby Dick ◽  
The Public

Information about the sources and processing characteristics of the public seismic, well log, and gas chromatography data; and time-depth conversion parameters, velocity model, and calculations of geothermal gradients.<br>

scholarly journals Diverse gas composition controls the Moby-Dick gas hydrate system in the Gulf of Mexico

Geology ◽  
2021 ◽  
Author(s):  
Alexey Portnov ◽  
A.E. Cook ◽  
S. Vadakkepuliyambatta
Keyword(s):  
Gulf Of Mexico ◽  
Gas Hydrate ◽  
Seismic Data ◽  
Gas Composition ◽  
The West ◽  
Moby Dick ◽  
Basin Scale ◽  
Bottom Simulating Reflection ◽  
Marine Basins ◽  
Hydrate Stability

In marine basins, gas hydrate systems are usually identified by a bottom simulating reflection (BSR) that parallels the seafloor and coincides with the base of the gas hydrate stability zone (GHSZ). We present a newly discovered gas hydrate system, Moby-Dick, located in the Ship Basin in the northern Gulf of Mexico. In the seismic data, we observe a channel-levee complex with a consistent phase reversal and a BSR extending over an area of ~14.2 km2, strongly suggesting the presence of gas hydrate. In contrast to classical observations, the Moby-Dick BSR abnormally shoals 150 m toward the seafloor from west to east, which contradicts the northward-shallowing seafloor. We argue that the likely cause of the shoaling BSR is a gradually changing gas mix across the basin, with gas containing heavier hydrocarbons in the west transitioning to methane gas in the east. Our study indicates that such abnormal BSRs can be controlled by gradual changes in the gas mix influencing the shape of the GHSZ over kilometers on a basin scale.

scholarly journals Wave Propagation Characteristics in Gas Hydrate-Bearing Sediments and Estimation of Hydrate Saturation

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 804
Author(s):  
Lin Liu ◽  
Xiumei Zhang ◽  
Xiuming Wang
Keyword(s):  
Gas Hydrate ◽  
Clay Content ◽  
Clean Energy ◽  
Compressional Wave ◽  
Physical Parameters ◽  
Well Log ◽  
Log Data ◽  
Phase Velocities ◽  
Hydrate Saturation ◽  
Hydrate Bearing Sediments

Natural gas hydrate is a new clean energy source in the 21st century, which has become a research point of the exploration and development technology. Acoustic well logs are one of the most important assets in gas hydrate studies. In this paper, an improved Carcione–Leclaire model is proposed by introducing the expressions of frame bulk modulus, shear modulus and friction coefficient between solid phases. On this basis, the sensitivities of the velocities and attenuations of the first kind of compressional (P1) and shear (S1) waves to relevant physical parameters are explored. In particular, we perform numerical modeling to investigate the effects of frequency, gas hydrate saturation and clay on the phase velocities and attenuations of the above five waves. The analyses demonstrate that, the velocities and attenuations of P1 and S1 are more sensitive to gas hydrate saturation than other parameters. The larger the gas hydrate saturation, the more reliable P1 velocity. Besides, the attenuations of P1 and S1 are more sensitive than velocity to gas hydrate saturation. Further, P1 and S1 are almost nondispersive while their phase velocities increase with the increase of gas hydrate saturation. The second compressional (P2) and shear (S2) waves and the third kind of compressional wave (P3) are dispersive in the seismic band, and the attenuations of them are significant. Moreover, in the case of clay in the solid grain frame, gas hydrate-bearing sediments exhibit lower P1 and S1 velocities. Clay decreases the attenuation of P1, and the attenuations of S1, P2, S2 and P3 exhibit little effect on clay content. We compared the velocity of P1 predicted by the model with the well log data from the Ocean Drilling Program (ODP) Leg 164 Site 995B to verify the applicability of the model. The results of the model agree well with the well log data. Finally, we estimate the hydrate layer at ODP Leg 204 Site 1247B is about 100–130 m below the seafloor, the saturation is between 0–27%, and the average saturation is 7.2%.

Thermal and visual time-series at a seafloor gas hydrate deposit on the Gulf of Mexico slope

2005 ◽  
Vol 233 (1-2) ◽  
pp. 45-59 ◽  
Author(s):  
I MACDONALD ◽  
L BENDER ◽  
M VARDARO ◽  
B BERNARD ◽  
J BROOKS
Keyword(s):  
Time Series ◽  
Gulf Of Mexico ◽  
Gas Hydrate ◽  
Hydrate Deposit

Potentially Large Subsurface Gas Hydrate Bodies in the Mexican Ridges, Southwestern Gulf of Mexico

2021 ◽  
pp. 1-29
Author(s):  
Papia Nandi ◽  
Patrick Fulton ◽  
James Dale
Keyword(s):  
Gulf Of Mexico ◽  
Gas Hydrate ◽  
Seismic Data ◽  
Poor Quality ◽  
Reflection Point ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
High Impedance ◽  
Acoustic Velocities ◽  
Seismic Images

As rising ocean temperatures can destabilize gas hydrate, identifying and characterizing large shallow hydrate bodies is increasingly important in order to understand their hazard potential. In the southwestern Gulf of Mexico, reanalysis of 3D seismic reflection data reveals evidence for the presence of six potentially large gas hydrate bodies located at shallow depths below the seafloor. We originally interpreted these bodies as salt, as they share common visual characteristics on seismic data with shallow allochthonous salt bodies, including high-impedance boundaries and homogenous interiors with very little acoustic reflectivity. However, when seismic images are constructed using acoustic velocities associated with salt, the resulting images were of poor quality containing excessive moveout in common reflection point (CRP) offset image gathers. Further investigation reveals that using lower-valued acoustic velocities results in higher quality images with little or no moveout. We believe that these lower acoustic values are representative of gas hydrate and not of salt. Directly underneath these bodies lies a zone of poor reflectivity, which is both typical and expected under hydrate. Observations of gas in a nearby well, other indicators of hydrate in the vicinity, and regional geologic context, all support the interpretation that these large bodies are composed of hydrate. The total equivalent volume of gas within these bodies is estimated to potentially be as large as 1.5 gigatons or 10.5 TCF, considering uncertainty for estimates of porosity and saturation, comparable to the entire proven natural gas reserves of Trinidad and Tobago in 2019.

Late Pleistocene–Holocene sedimentation surrounding an active seafloor gas-hydrate and cold-seep field on the Northern Gulf of Mexico Slope

2010 ◽  
Vol 278 (1-4) ◽  
pp. 43-53 ◽  
Author(s):  
Wesley C. Ingram ◽  
Stephen R. Meyers ◽  
Charlotte A. Brunner ◽  
Christopher S. Martens
Keyword(s):  
Gulf Of Mexico ◽  
Late Pleistocene ◽  
Gas Hydrate ◽  
Cold Seep ◽  
Northern Gulf Of Mexico

Gas hydrate and crude oil from the Mississippi Fan Foldbelt, downdip Gulf of Mexico Salt Basin: significance to petroleum system

2001 ◽  
Vol 32 (8) ◽  
pp. 999-1008 ◽  
Author(s):  
Roger Sassen ◽  
Stephen T Sweet ◽  
Debra A DeFreitas ◽  
J.Alejandro Morelos ◽  
Alexei V Milkov
Keyword(s):  
Gulf Of Mexico ◽  
Crude Oil ◽  
Gas Hydrate ◽  
Petroleum System

scholarly journals Characterization of Microbial Community Structure in Gulf of Mexico Gas Hydrates: Comparative Analysis of DNA- and RNA-Derived Clone Libraries

2005 ◽  
Vol 71 (6) ◽  
pp. 3235-3247 ◽  
Author(s):  
Heath J. Mills ◽  
Robert J. Martinez ◽  
Sandra Story ◽  
Patricia A. Sobecky
Keyword(s):  
Phylogenetic Analysis ◽  
Microbial Community ◽  
Gulf Of Mexico ◽  
Gas Hydrate ◽  
Phylogenetic Analyses ◽  
Active Fraction ◽  
Clone Libraries ◽  
Dna And Rna ◽  
Rna And Dna

ABSTRACT The characterization of microbial assemblages within solid gas hydrate, especially those that may be physiologically active under in situ hydrate conditions, is essential to gain a better understanding of the effects and contributions of microbial activities in Gulf of Mexico (GoM) hydrate ecosystems. In this study, the composition of the Bacteria and Archaea communities was determined by 16S rRNA phylogenetic analyses of clone libraries derived from RNA and DNA extracted from sediment-entrained hydrate (SEH) and interior hydrate (IH). The hydrate was recovered from an exposed mound located in the northern GoM continental slope with a hydrate chipper designed for use on the manned-submersible Johnson Sea Link (water depth, 550 m). Previous geochemical analyses indicated that there was increased metabolic activity in the SEH compared to the IH layer (B. N. Orcutt, A. Boetius, S. K. Lugo, I. R. Macdonald, V. A. Samarkin, and S. Joye, Chem. Geol. 205:239-251). Phylogenetic analysis of RNA- and DNA-derived clones indicated that there was greater diversity in the SEH libraries than in the IH libraries. A majority of the clones obtained from the metabolically active fraction of the microbial community were most closely related to putative sulfate-reducing bacteria and anaerobic methane-oxidizing archaea. Several novel bacterial and archaeal phylotypes for which there were no previously identified closely related cultured isolates were detected in the RNA- and DNA-derived clone libraries. This study was the first phylogenetic analysis of the metabolically active fraction of the microbial community extant in the distinct SEH and IH layers of GoM gas hydrate.

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