Effect of Basin Geometry on Locating Promising Hydrocarbon Traps: Tiba Natrun - Kattaniya Inverted Basin, Northern Western Desert (Egypt)

By

 Adel R. Moustafa¹, Mohamed Abd El-Aziz², Waleed Gaber³

(1) Department of Geology, Ain Shams University, Cairo 11566, Egypt (2) Qarun Petroleum Company, Cairo, Egypt (3) Shell Egypt, Cairo, Egypt

 The Tiba Natrun - Kattaniya basin is a Jurassic-Early Cretaceous rift basin bounded on the north by ENE-oriented faults linked by NE- and WNW-oriented transfer faults. Late Cretaceous-Early Tertiary inversion of the basin due to WNW-ESE shortening involved a component of right-lateral slip on the ENE-oriented faults. The ENE- and NE-oriented faults at the rift boundary were predominantly reactivated by reverse slip leading to enormous uplift of the hydrocarbon source rocks from the depocenter of the basin. In contrast, continuous subsidence of the WNW-oriented rift segments (e.g. at Tiba Natrun sub-basin) allowed hydrocarbon maturation and expulsion from potential source rocks.

Intra-basin structures formed by inversion include NE-oriented folds and reverse faults forming excellent hydrocarbon traps (e.g. El-Ahram, Qarun, N. Qarun, SW Qarun, and N. Harun oil fields). Thick, syn-inversion Eocene rocks were deposited in a foredeep basin lying south of the highly inverted area allowing maturation of Cretaceous source rocks. Extensive exploration in the area indicates that hydrocarbon traps in the highly inverted part of the basin are not suitable sites for hydrocarbon accumulation due to halting hydrocarbon maturation (as a result of inversion) and lack of trap integrity (breaching by erosion, absence of top seal, high fracturing, etc.). Intra-basin hydrocarbon traps are the best prospects within the inverted basin. Continuously subsiding parts of the basin at the WNW-oriented rift segments are also promising areas for hydrocarbon maturation and expulsion into updip structural traps.