Deepwater Comoros Oil Legs
Why the Comoros should cook oil where Mozambique cooked gas — a question of burial, heat, and time.
Oil is cooked, not found. The trick is not to overcook it.
The science behind oil generation is geochemistry — and it is as complex and delicate as every chef knows: cooking time, temperature and the quality of the starting materials all shape the result. Oil can be made very slowly, like cooking sous vide, at low temperature over millions of years; or in a flash at elevated temperature — but with the likelihood of overcooking, or “cracking”, if the oils generated cannot escape.
In the Mozambique Channel, the source rock responsible for the area's giant gas fields is thought to be Permian–Triassic (200–250 million years old), resting on continental basement. Today it is deeply buried — ca. 8–10 km — at temperatures of ca. 200 °C that have prevailed for millions of years, in part because continental crust is more radioactive than oceanic crust, given its granitic composition rich in potassium feldspar and uranium.
At this depth, source-rock maturity is overmature for both oil and gas. Deep burial and heavy overburden, paired with higher temperatures, overcooked the original organic matter — so today the products are mainly dry methane gas (C1).
By comparison, the Comoros has less overburden — only ca. 3,500 m of sediment above basement — and deeper water, ca. 3,000 m, providing less insulating rock above. The basement is oceanic, and so not as radioactive. The likely result: a more perfectly cooked outcome — squarely in the sous vide sweet spot for oil, not gas. Slow cooking, not overcooking.
Both models place the Lower Cretaceous in the oil window today.
PseudoWell_1 burial-history and temperature models. Colour scale: blue (cool) to red (hot), °C. In both the off- and on-structure settings, the base of the Lower Cretaceous lies in the oil window today.
The two burial-history charts model a geothermal rift setting in the Comoros — an off-structure setting and an on-structure setting. In both, the base of the predicted Lower Cretaceous section sits today in the oil window, at peak oil maturity — the conditions that should yield oil legs in deepwater Comoros.