Geology and Petroleum Exploration Play Concepts of the Central Atlantic Conjugate Margins (Nova Scotia – Essaouira-Agadir Morocco): Similarities and Differences

Abstract

The Atlantic margin of Morocco extends over 3000 km of coastline. It is one of the oldest existing passive margins, and is partly conjugate to the Scotian margin of North America. Today the Scotian Basin encompasses an area of over 300 000 km2 beneath the continental shelf and slope, and includes up to 20 km thickness of sedimentary rocks in its deepest areas south and east of Sable Island. Because of their key positions within the Central Atlantic Ocean, and their promising hydrocarbon potential, both margins were, and still the object of extensive research programs and industrial exploration studies. The main objective of this paper is a comparative study of the Atlantic conjugate margins of Morocco and Nova Scotia using the example analogues of the Scotian Basin and Essaouira-Agadir Basin. We focused mainly on the similarities and differences in the general geology, geodynamic evolution, salt tectonics, play concepts, and then petroleum systems in both basins.

The sedimentary fill of the Mesozoic-Cenozoic conjugate marginal basins, Scotian Basin and Essaouira-Agadir Basin, shows a very similar depositional and structural history, especially during their Triassic and Jurassic evolution. Salt movements are well expressed from Early Jurassic to Late Tertiary forming similar salt-related features (pillows, diapirs, canopies, toe) in both basins.

Both the Nova Scotian and Moroccan margins show evidence for elements of working petroleum systems. The Scotian Basin has proven petroleum systems with past production from the Cohasset-Panuke oil fields, ongoing gas production from the Sable Sub-basin and the Deep Panuke gas field, all on the shallow Scotian Shelf. Like the Scotian Basin, the Essaouira-Agadir Basin has proven petroleum systems in the onshore part of the basin with minor oil and gas production in the Sidi Rhalem, Toukimt and Meskala fields. Recently, exploration focus shifted to the deep water on both conjugate margins because of the impressive hydrocarbon discoveries and high success rates in deep water of other circum-Atlantic basins such as the Gulf of Mexico, offshore Brazil and West Africa, and recently Northwest Africa (Mauritania).

Offshore domain of the two homologue basins is still underexplored, only very few deep water wells were drilled in both basins until now. Five play concepts were proven in the Scotian Basin; Early-Middle Jurassic carbonates and sandstones; Oxfordian–Tithonian; Berriasian-Valanginian-Hauterivian; Hauterivian-Barremian; and Aptian-Albian-Cenomanian. While only five wells were drilled in offshore Essaouira-Agadir Basin; Pre-Albian, Salt-related structures during Cenomanian-Turonian and Tertiary stratigraphic play were tested. The main play concepts within the Essaouira-Agadir offshore segment are Salt diaper and Tertiary amalgamated channel play in the inboard area, the Lower Cretaceous Subsalt plays and the Toe thrust play outboard. One major difference between the two basins fill occurred during Cretaceous time where an upwelling process resulted in the deposition of organic rich sediments in Moroccan side. This has probably contributed to the existence of a Cretaceous petroleum system in Morocco especially where adequate burial is bringing into maturity this source rock.

Ongoing detailed studies and analyses are directed by super-major companies such as Shell and BP (Offshore Nova Scotia) and Kosmos, Chevron, BP and Cairn (Offshore Morocco) in both margins to get a better understanding of their hydrocarbon potential.

AAPG Datapages/Search and Discovery Article #90226 © 2015 European Regional Conference and Exhibition, Lisbon, Portugal, May 18-19, 2015