The Sedimentology and Stratigraphic Framework of the Bahariya Formation, Western Desert, Egypt

By

 C. A. Watkins¹, S. Metters¹, J. P. G. Fenton¹, Zeinab El Menshawy², Zakaraya Ahmed², J. Yule²

(1) Robertson Research International Ltd, N/A, Egypt (2) Khalda Petroleum Corporation, N/A, Egypt

 Reserves in the Cretaceous Bahariya Formation of the Western Desert, Egypt, are reservoired within challenging super-heterogeneous sediments. A recent study of the Bahariya Formation in the Khalda Concession, undertaken jointly by RRI and Khalda Petroleum, reviews depositional models and has generated a preliminary, high resolution sequence stratigraphic framework based on integrated biostratigraphic and sedimentological analyses. Detailed core description and palynological and micropalaeontological analyses were undertaken, with cuttings samples used to extend the intervals of investigation. Candidate stratal surfaces recognised in core were constrained in terms of facies and stratigraphic significance by biostratigraphic results and extrapolated to uncored intervals.

The Lower Bahariya Formation was deposited in an active coastal plain to shallow marine setting, dominated by estuarine channels with fringing tidal flats and lagoons. In contrast, the Upper Bahariya represents a low relief, relatively inactive coastal to shallow marine setting with heavily vegetated coastal plain deposits thinly interbedded with shallow marine limestones. A total of eight sequences were identified. Sequences BS10 to BS50 (in lower parts) are third order sequences (cf. Hardenbol et al., 1998), but the status of BS60 to BS80 is uncertain and may be of fourth order magnitude only.

The Bahariya Formation in the study area was deposited on a ramp margin with no significant shelf break, resulting in the development of dominantly Type 2 sequence boundaries. A notable exception is BS50, the base of which represents a Type 1 sequence boundary. Possible bypass and erosion at this surface may have important implications for future exploration.