Petrophysical analysis and pressure gradients reveal hydrocarbon potential in the Paleozoic pre-rift of the PTAH Oil Field, Egypt.

The PTAH oil field in Egypt's northern Western Desert offers considerable potential for hydrocarbon production. This research centers on the Shiffah formation and evaluates its petrophysical properties using data from four wells. The analysis involves wireline logs (including gamma-ray, density, neutron, sonic, and resistivity), core samples, pressure readings, and cross-plots. A combination of qualitative and quantitative techniques was employed to assess the formation's hydrocarbon-bearing capacity. The Shiffah formation primarily comprises sandstone, calcareous shale, and siltstone. Key petrophysical parameters such as shale volume, effective porosity, net thickness, and fluid saturations were mapped to evaluate variations across the field. Findings indicate that the reservoirs have an average shale content of 2.5%, an effective porosity of 11%, and an oil saturation averaging 47.84%. The net reservoir thickness ranges from 97.5 to 655 feet, with the net pay zones between 6.5 and 137 feet. These results underscore the potential for hydrocarbons within the field. Core analysis supports these findings, highlighting favorable horizontal and vertical permeability values. The correlation between well-log data and pressure information also aligns with production outcomes from Drill Stem Tests (DST). Among the wells, Ptah-1X exhibited the most promising petrophysical properties, whereas Ptah-4X was determined to be a dry well, with water saturation as high as 98%. Reservoir pressure analysis helped to pinpoint key fluid contacts, such as the oil-water contact (OWC). Pickett's plot was used to calculate formation water resistivity, yielding values between 0.0170 and 0.0176 across the four wells. This comprehensive evaluation of the Shiffah formation offers valuable insights into its hydrocarbon potential and guides future exploration and drilling.