کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
6435540 1637181 2013 13 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Investigation on the geochemical dynamics of a hydrate-bearing pockmark in the Niger Delta
ترجمه فارسی عنوان
بررسی دینامیک ژئوشیمیایی یک قطب هیدرات کششی در دلتای نیجر
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات زمین شناسی اقتصادی
چکیده انگلیسی

A joint industrial project with IFREMER and Total provides insights into the tectonic setting and the geochemistry of a large active pockmark offshore W-Africa in the Niger Delta. The study combines both geophysical (seismic) and geochemical data to infer the dynamics of a 300 m wide pockmark located at 667 m water depth. Two Calypso cores, one at the centre and one outside the pockmark, along with three box-cores, two inside the pockmark and one outside, were collected to study the geochemistry of gas hydrates, carbonates and pore waters. Two seismic lines, a 3D high resolution random line and a 2D high resolution seismic line, provide a good description of the plumbing of the system. The integrated results depict a very active pockmark characterized by several gas charged-bodies, a well identified BSR marking a hydrate accumulation zone, charged from deeper sources via a network of faults. Hydrates and carbonate concretions have been detected inside the pockmark while only the latter has been found outside. The hydrate analyses show that the hydrate-forming gases are of thermogenic origin, albeit overwhelmingly composed of methane. Pore-water analyses reveal the occurrence of anaerobic oxidation of methane coupled with sulphate reduction at shallow depth (∼200 cm). The chloride concentration profile exhibits both values lower than that of seawater which is inherent to hydrate dissociation after core recovery and positive anomalies (values 7% higher than that of seawater background) at the lowermost part of the core. The latter evidence suggests current or recent hydrate formation at this area. The carbonate dating provides additional temporal information and indicates that this pockmark has been active since ∼21 kyr.

► Seismic surveys and geochemical analyses allow the study of a hydrate-bearing pockmark. ► 2D and 3D seismic shows a BSR, faults and hydrocarbon reservoirs. ► Geochemical analyses highlight AOM-process occurrence and carbonate precipitation. ► Gas source identification was possible and a migration pathway was proposed. ► Carbonate U/Th dating indicates that the large pockmark has been active since 21 kyr.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Marine and Petroleum Geology - Volume 43, May 2013, Pages 297-309
نویسندگان
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