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Thebes Formation Unconventional Resource Assessment, Gulf of Suez, Egypt


The Gulf of Suez in Egypt contains more than 80 conventional oil fields with reservoirs from Precambrian up to Quaternary age. To date, these fields have all been conventional resources. This abstract will take part of the Gulf of Suez sequence within the fields of GUPCO (Gulf of Suez Petroleum Company) and present a work process for unconventional resource assessment of Thebes formation within one of these areas.

Thebes formation is a Late Eocene Pre-rift mega sequence succession and plays an important role in the conventional system of Gulf of Suez, not only as one of the important source rocks, but also a fractured carbonate reservoir in multiple fields. Thebes formation mainly represent a massive fossiliferous limestone, nummulitic with flint and thin interbeds of marl, from marine sublittoral depositional setting overlain by unconformity surfaces at the top and bottom.A series of chance maps were made to represent the Charge, Reservoir, and Producibility potential within the study area. The objective was to identify a sweet spot within the area where an unconventional development might be successful.

Charge was evaluated using the outputs from a petroleum system model. Generated oil generation mass was used to indicate best saturation with hydrocarbons. Transformation ratio was used as a proxy for retention.

Reservoir thickness was used as the proxy for reservoir effectiveness where thicker reservoir had a higher chance of containing multiple intervals for good potential intervals and, therefore, multiple completions.

The influences on Producibility were considered to be constant over the area, so the same chance was applied across the area.

The chance maps for these three Element were compiled to identify a sweet spot area.

Volumetric assessment was done over the sweet spot by extracting the inputs for volumes and chance of success for the calculation directly from the geological and chance maps. The recoverable resources were calculated using EUR/well and well density. The Eagle Ford was used as an analogue. A volumetric assessment of in-place volumes was done as a cross check of the recoverable resources.

In the probabilistic volumes, the range of the well density has been enlarged to include a scenario where multi-lateral completions will be done at multiple levels within the thick Thebes formation. This gives a substantially larger well density than normally seen in unconventional plays where this possibility does not exist.