Types of fluid-related features controlled by sedimentary cycles and fault network in deepwater Nigeria

Tania Marsset (1) , L. Ruffine (1) , Aurelien Gay (2) , S. Ker (1) , E. Cauquil (3)

1 GM - Unité Géosciences Marines
2 Géosciences Montpellier
3 Total E&P

The seismic characteristics of focused fluid-related features such as pockmarks and carbonate build-ups on the Nigerian continental slope have been investigated using complementary seismic data sets (reprocessed 3D exploration data and 2D Very High Resolution hull-mounted and near-bottom seismic data) coupled with the results of previous studies (sedimentological, geotechnical and geochemical analyses). The results show different types of fluid-related features within the hemipelagic phase of long duration (∼1 Myr) Turbidite/Hemipelagic cycles. They are the product of the disturbance of the hosting sediments following two main distinct processes: (1) no or low sediment deposition caused by fluid escape associated with seafloor settlement (benthic fauna, carbonate precipitation, gas hydrate formation) and (2) post-depositional erosion, caused either by fluid release (dewatering from underlying features such as channels and upward migration from a deep source) or by collapse (destabilisation of gas hydrates). The temporal evolution reveals a decrease in fluid flow during the hemipelagic deposition as witnessed by the decrease in methanogenic activity and by gas hydrate destabilisation. The spatial distribution of fluid-related features seems to be controlled by the type of fault (small fault or structural lineament).

Mots clés: Niger delta; Fluid flow; Pockmark; Gas hydrates; Methane-derived carbonate; Fault network; Sedimentary cycles

Domaines: Géophysique [physics.geo-ph]

Tania Marsset, L. Ruffine, Aurelien Gay, S. Ker, E. Cauquil. Types of fluid-related features controlled by sedimentary cycles and fault network in deepwater Nigeria. Marine and Petroleum Geology, 2018, 89, pp.330-349. ⟨10.1016/j.marpetgeo.2017.10.004⟩. ⟨hal-01685513⟩