Polygonal faults in Eocene carbonate reservoir, Abu El-Gharadig Basin, Egypt

Interpretations of high resolution three-dimensional (3D) seismic data and well logs indicate that the fine-grained carbonates of the middle Eocene Apollonia Formation in the Abu El-Gharadig Basin (Western Desert, Egypt) is deformed by the polygonal fault system. The 3D seismic data cover an area of about 1,100 km(2) including the JDT gas field, where the Apollonia Formation includes gas-bearing reservoir intervals with high porosity and low permeability. The results show that the polygonal faults have no preferred dip or strike directions. They have lengths ranging from 123 to 3,800 m, fault throws up to 100 m and dips of 27 degrees-88 degrees. Fault traces are approximately linear in vertical cross-section producing a series of horsts and grabens. We used this data to interpret and geometrically characterize the polygonal faults in a fine-grained carbonate reservoir unit, and we show the faults influence the fluids flow in the reservoir. The increase in the formation pore pressure mechanism is the proposed mechanism for the initiation of the polygonal fault system in the Abu El-Gharadig Basin.