Matruh Basin: Hydrocarbon Plays in an Inverted Jurassic-Cretaceous Rift Basin in the Northern Western Desert of Egypt

By

 Adel R. Moustafa¹, Ahmed N. El-Barkooky², Asem Mahmoud³, Ahmed M. Badran⁴, Mohamed A. Helal⁴, Magda Nour El Din⁴, Hosam Fathy⁴

(1) Ain Shams University, Cairo, Egypt (2) Cairo University, Cairo, Egypt (3) BAPETCO, Cairo, Egypt (4) Shell Egypt, Cairo, Egypt

 Matruh basin is a large Jurassic-Early Cretaceous passive rift in the northern Western Desert with a unique NNE-SSW orientation inherited from reactivated Paleozoic fabric. Eastwards dipping and thickening Jurassic/Lower Cretaceous syn-rift sediments contain excellent reservoir/source rock combination. TOC values are up to 10% in the Jurassic, 5% in the Lower Cretaceous, and 75% in some coal seams. Two main rifting phases are recognized in the Jurassic and Early Cretaceous. In the early stage of Jurassic rifting, fluvio-lacustrine conditions with frequent subaerial exposure deposited red beds associated with minor volcanicity. Block faulting and tilting controlled the distribution of fluvial deposits. Basinal conditions prevailed in the Middle-Late Jurassic. Resumed rifting in the Early Cretaceous deposited thick mature sands with excellent reservoir quality.

Late Cretaceous-Early Tertiary positive tectonic inversion of the basin formed NNE-oriented fault-propagation folds dissected by NW-oriented normal faults. The latter dissect the Upper Cretaceous post-rift rocks and die out in Albian clastics whereas the rift-parallel NNE faults dissect the underlying syn-rift rocks. The NNE-oriented folds form excellent structural traps in four fields in the basin producing mainly gases with some oil and condensates. Combination traps at the western flank of the basin include syn-rift sands derived from nearby Paleozoic highs and deposited at the Paleozoic-Mesozoic unconformity within gently dipping, down-faulted areas. Total discovered gas reserves in the basin are about 3 tcf. However, several structural traps have yet to be tested and other reservoir units represent the future for hydrocarbon plays in the basin.