Prediction of Formation Pressure Gradients of NC98 Field-Sirte Basin-Libya

The prediction of formation pore pressure and fracture pressure gradients is a significant step towards the drilling plan. In this study, the formation pressures of twelve wells from NC98 field-Sirte Basin (Waha Oil Company) were calculated by employing empirical methods, Eaton’s equations, that depend on the real drilling and well-logging data. Regarding the results, the normal pore pressure in the NC98 field in Sirte basin is 0.437 Psi/ft, and it is extending from the top of the wells in the investigated area to 7,000 ft. A subnormal to normal pore pressure zone is noticed in the interval of 7,000 ft. to 9,000 ft. Then, slightly subnormal to somewhat abnormal (overpressure) region is seen from 9,000 ft. to 11,200 ft. Beyond to that depth and down to the top of the reservoir, the overpressure zone was clearly observed. Based on the results, the casing setting depth and the equivalent mud weight were simply determined for the area of study.