MASS-WASTING INDUCED SHIFTS OF THE BASE OF THE GAS HYDRATE STABILITY ZONE: EXAMPLES FROM THE OFFSHORE NIGER DELTA BASIN, NIGERIA
Abstract
Mass-wasting episodes lead to significant changes in the pressure and temperature regimes within shallow marine sediments and induce variations in the thickness of the gas hydrate stability zone. These variations are marked by vertical migrations of bottom-simulating reflections that typically mark the base of the hydrate zone. Using exploration seismic data from the Offshore Niger Delta, this study presents two examples involving the vertical migration of the base of the gas hydrate stability zones induced by mass-wasting events. The first is related to a slope failure surface along the forelimb of an active thrust-cored anticline with considerable bathymetric relief. Sediment removal has induced both a decrease in overburden pressure and an incursion of cooler temperature flux in strata in the anticline and led to a migration of the base of the gas hydrate stability zone to deeper levels. The second case is related to a recent erosional event that has led to sediment removal along a seafloor channel course. Evidence of ongoing migration of the base of the gas hydrate stability zone to deeper levels is provided by the lateral termination of a BSR along channel wall, its absence beneath the channel bottom and its apparent downward bend close to the channel fringes. Apart from unroofing hydrate systems and releasing free gas into the ocean and possibly the atmosphere, mass-wasting events on the seafloor, represent significant drivers influencing the formation of gas hydrates in shallow subsea sediments and the thickness and depths of the gas hydrate stability zone.
References
Adeleye, M. A., Yekeen, K. O. & Amidu, S. A. 2020. Seismic stratigraphic analysis for hydrocarbon exploration in the Beta Field, Coastal Swamp Depobelt, Niger Delta. Geology, Geophysics & Environment. 46 (4): 259–271. https://doi.org/10.7494/geol.2020.46.4.259 DOI: https://doi.org/10.7494/geol.2020.46.4.259
Aminu, M. B. & Ojo, S. B. 2018. Application of spectral decomposition and neural networks to characterise deep turbidite systems in the outer fold and thrust belt of the Niger Delta. Geophysical Prospecting. https://doi.org/10.1111/1365-2478.12569. DOI: https://doi.org/10.1111/1365-2478.12569
Aminu, M. B. & Ojo, S. B. 2021. Multiple Bottom Simulating Reflections in the Deepwater Niger Delta: Seismic Character and Inferred Gas Supply Dynamics. International Journal of Scientific Research and Engineering Development. 4(3), 316-327.
Aminu, M. B. & Ojo, S. B. 2024. Seafloor Morphology and Potential Gas Hydrate Distribution in the Offshore Niger Delta. International Journal of Advanced Geosciences, 12(1), 17-26. DOI: https://doi.org/10.14419/wwajt225
Andreassen, K., Mienert, J., Bryn, P. & Singh, S. C. 2000. A double gas hydrate related bottom simulating reflector at the Norwegian continental margin, in: Holder G. D., Bishnoi, P. R., (Eds.), Gas Hydrates: Challenges for the Future, Annals of the New York Academy of Science 912, 126-135. https://doi.org/10.1111/j.1749-6632.2000.tb06766.x DOI: https://doi.org/10.1111/j.1749-6632.2000.tb06766.x
Avbovbo, A.A. 1978. Tertiary lithostratigraphy of Niger Delta. American Association of Petroleum Geologist Bulletin 62, 295-306. https://doi.org/10.1306/C1EA482E-16C9-11D7-8645000102C1865D . DOI: https://doi.org/10.1306/C1EA482E-16C9-11D7-8645000102C1865D
Baba, K. & Yamada, Y. 2004. BSRs and associated reflections as an indicator of gas hydrate and free gas accumulation: an example of accretionary prism and forearc basin system along the Nankai Trough, off central Japan. Resource Geology 54, 11-24. https://doi.org/10.1111/j.1751-3928.2004.tb00183.x DOI: https://doi.org/10.1111/j.1751-3928.2004.tb00183.x
Bangs, N. L. B., Musgrave, R. J. & Trehu, A. 2005. Upward shifts in the southern Hydrate Ridge gas hydrate stability zone following postglacial warming, offshore Oregon. Journal of Geophysical Research 110, B03102. https://doi.org/10.1029/2004JB003293 DOI: https://doi.org/10.1029/2004JB003293
Bangs, N. L., Hornbach, M. J., Moore, G. F. & Park, J.-O. 2010. Massive methane release triggered by seafloor erosion offshore southwestern Japan. Geology 38, 1019-1022. https://doi.org/10.1130/G31491.1 DOI: https://doi.org/10.1130/G31491.1
Bilotti, F. & Shaw, J. H. 2005. Deep-water Niger Delta fold and thrust belt modeled as a critical-taper wedge: The influence of elevated basal fluid pressure on structural styles. American Association of Petroleum Geologist Bulletin 89, 1475–1491. https://doi.org/10.1039/C0EE00203H . DOI: https://doi.org/10.1306/06130505002
Boswell, R., Collett, T. S., Frye, M., Shedd, W., McConnell, D. R., & Shelander, D. 2012. Subsurface Gas Hydrates in the Northern Gulf of Mexico. Mar. Pet. Geology. 34 (1), 4–30. https://doi.org/10.1016/j.marpetgeo.2011.10.003 DOI: https://doi.org/10.1016/j.marpetgeo.2011.10.003
Brooks, J. M., Bryant, W. R., Bernard, B. B. & Cameron, N. R. 2000. The nature of gas hydrates on the Nigerian Continental slope. Annals of the New York Academy of Sciences 912, 76 - 93 DOI: https://doi.org/10.1111/j.1749-6632.2000.tb06761.x
Burke, K., 1972. Longshore drift, submarine canyons and submarine fans in development of Niger Delta: American Association of Petroleum Geologist Bulletin 56, 1975-1983. https://doi.org/10.1306/819A41A2-16C5-11D7-8645000102C1865D . DOI: https://doi.org/10.1306/819A41A2-16C5-11D7-8645000102C1865D
Copyright (c) 2024 FUDMA JOURNAL OF SCIENCES
This work is licensed under a Creative Commons Attribution 4.0 International License.
FUDMA Journal of Sciences
