Mature Field Development Geology of a Complex Estuarine-Shallow Marine Reservoir: Bahariya and Abu Roash “G” Formations, Western Desert, Egypt

Wehr, Fred¹, Ali Bakr¹, Tarek Mansoury¹, Nabil Sedky¹, Bill Campbell², Khaled Mowafi² (1) Apache Egypt, Cairo, Egypt (2) Khalda Petroleum Company, Cairo, Egypt

The Bahariya and Abu Roash “G” formations consist of a complex, mixed clastic-carbon-ate succession of Upper Cretaceous age in the Western Desert of Egypt. In the Khalda Ridge, Bahariya production started in 1986. By the time Apache acquired operatorship of the Khalda Concession in 2001, mature field production was in steep decline. Starting in late 2001, a series of field studies were undertaken to optimize waterflooding and provide infill drilling locations. These studies involved remapping and recorrelation, including detailed sequence stratigraphic correlations and core description, petrophysical analysis, and integration of reservoir engineering and production data into 3D geologic models.

The key to successful development in the Bahariya and Abu Roash has proven to be pre­dictive understanding of internal reservoir architecture guiding an aggressive drilling and recompletion program. Remaining oil potential in the Lower Bahariya is largely in incised channel systems at the top of the unit and in the basal part of the overlying Upper Bahariya. In the Upper Bahariya and Abu Roash “G” sands, hydraulic fracturing and pattern water­flooding are proving successful at building sustained production from thin-bedded, gener­ally poor-quality reservoirs.

To date 50 infill wells and numerous recompletions have resulted from these studies. The production decline in the mature fields in the Khalda Ridge has been reversed, with pro­duction currently above 2001 levels. At current activity levels, it should be possible to main­tain current production for at least three more years, providing a foundation for production growth from exploration and new field development.