Journal
MARINE AND PETROLEUM GEOLOGY
Volume 134, Issue -, Pages -Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.marpetgeo.2021.105330
Keywords
Marine CSEM; Submarine gas hydrate; Black sea; Rotational invariant
Categories
Funding
- German Federal Ministry of Education and Research (BMBF) [03G0819A, 03SX320A, 03G0856A]
- German Federal Ministry for Economic Affairs and Energy (BMWi) [03G0819A, 03SX320A, 03G0856A]
- European Union
- China Scholarship Council
Ask authors/readers for more resources
The Black Sea has extensive indicators of methane hydrates, and marine controlled-source electromagnetics (CSEM) is a suitable method for investigating hydrates. CSEM data collected in the Black Sea reveal resistive layers indicating potential gas hydrate saturations, with comparisons to seismic data and other experiments providing further insights.
The Black Sea is known to have extensive direct and indirect indicators of methane hydrates. Since the resistivity of the seafloor increases significantly in the presence of gas hydrates or free gas, marine controlled-source electromagnetics (CSEM) is a suitable method for the investigation of hydrates. We have collected CSEM data in a channel-levee system of the Danube paleo-delta (Bulgarian sector) at water depths of about 1500 m. The working area is within the gas hydrates stability zone and seismics suggests the presence of gas hydrates. The CSEM data were acquired with stationary receivers and a novel mobile, dual polarization transmitter system, and interpreted in terms of rotational invariants by means of 1-D inversions at common midpoints (CMP) to generate pseudo 2D resistivity sections. The inversion results reveal two resistive layers at shallow depths of 60-120 mbsf and greater depths of 270-400 mbsf. A comparison with seismics shows a good correlation of the shallow layer with high amplitude reflections and a velocity anomaly. The deeper layer can be tied to the current bottom simulating reflector (BSR). The comparison to a second CSEM experiment, which was conducted by the BGR (Federal Institute for Geosciences and Natural Resources, Germany) shows a good agreement of the derived sections down to a depth of about 350 m. Based on salinity and porosity models derived from boreholes in the Black Sea, we apply Archie's law to estimate potential gas hydrate saturations of up to 23% for the shallow resistor and up to 7% for the deeper layer. Differences are evident at depths greater than 450 m, where we see a conductive layer not evident in the BGR section. This deeper conductor could be evidence for increasing salinities of pore fluids at greater depths, which were previously found in DSDP drilling cores.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available