As trade curiosity in hydrocarbon exploration offshore East Africa will increase, consideration is popping to frontier areas within the area such because the West Indian Ocean. At first look, this space appears to be like like a barren oceanic crust with little potential, however there’s tantalising proof to recommend in any other case. CGG geoscientists have been sifting via the proof to re-evaluate alternatives offshore East Africa and within the West Indian Ocean.
The finest indication marine frontier area has exploration potential is the presence of continental crust, the place there is a chance for working petroleum programs to develop in thick sedimentary basins. In this setting, the perfect likelihood for continental crust is the incidence of micro-continents.
Legacy geophysical and geological information recommend that oceanic crust is pervasive all through the West Indian Ocean, forming the Comoros and Glorioso Islands, Mauritius and far of the submarine ridge between Mauritius and the Seychelles. However, plenty of latest investigations present overwhelming proof for the existence of slivers of continental crust within the West Indian Ocean.
An instance of a micro-continent on this area is the Seychelles Bank, the place exploration wells drilled in 1981, about 120 km west of the principle islands, proved the presence of a working petroleum system with oil exhibits and a mature Lower-Middle Jurassic supply rock.
Robertson Plate Kinematics reconstruction fashions of the West Indian Ocean present the complexity of the poly-phased break-up of Gondwana, and recommend that there could also be many extra continental fragments much like the Seychelles Bank scattered over the area.
Further hints to the existence of continental crust come from more moderen geophysical and geological information. Studies on refraction seismic and gravity information in 2013 point out that the continental platform on which the principle Seychelles Islands are positioned might lengthen additional to the west and south-west. To the south, proof can also be constructing for Mauritius, with gravity survey evaluation indicating an anomalously thick crust of 25-30 km in comparison with the 5-10 km thick surrounding oceanic crust. This was supported by a geological examine that confirmed that zircons discovered on Mauritius have been of continental origin with various ages of 660-1971 Ma.
To the west, the same story is creating for the Comoros. Detrital zircons have been discovered there in 2017, giant sandstone xenoliths have been discovered on the Comoran island of Anjouan and sandstone inclusions in lavas on Grande Comore and Mohéli. In addition, tar balls discovered on Grande Comore have been matched to a Jurassic supply rock via geochemical evaluation.
These observations are supplemented by offshore seismic reflection information acquired west of the Comoros islands and east of the Davie Fracture Zone that present tilted fault blocks with stratal progress at depth, demonstrating the presence of a rifted continental part on this space. Furthermore, the complete extent of the Davie Fracture Zone was questioned in 2016, which might suggest that the Madagascan continental shelf extends additional north of the island and probably so far as the Comoros.
CGG will step up the hunt for micro-continents with a brand new 2D multi-client regional survey.
(Source and picture: CGG)
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