Pre-drill pore pressure prediction using seismic velocities for prospect areas at Beni Suef Oil Field, Western Desert, Egypt

Abstract

Pre-drill prediction of formation pore pressure from surface seismic survey is very important for drilling, production, and reservoir engineering because it affects drilling operations and well-planning processes. If it is not properly evaluated, it can lead to numerous drilling problems such as dangerous well kicks, lost circulation, blowouts, stuck pipe, excessive costs, and borehole instability. Pre-drill pore pressure estimation has been obtained from transform models using seismic interval velocities. However, the accuracy of this estimate of pore pressure is directly related to the reliability of these interval velocities. Bulk density was estimated from seismic interval velocity and transit time. Normal pore pressure gradient is estimated from the slope of a trendline that is generated from logarithm transit times versus depth. Overburden pressure at any depth was calculated from the integration of the average interval bulk densities and thicknesses above that depth. Pore pressure has been obtained from overburden pressure and observed interval velocities using modified Eaton's equation. 154 CDPs were used along 28 seismic lines at Beni Suef basin, Western Desert, Egypt, to accomplish the purpose of this study. Two velocity reversal zones showing abnormally high pore pressure were detected and correlated to Abu Roash and Bahariya Formations. Moreover, pore pressure gradient maps were established for these two zones to predict the possible horizontal fluid flow (migration paths) for the proposal of prospects with lower pressures and less drilling risks.Finally, it is possible to calculate and recommend the required heavier mud weight to drill.

Assessment of mudstone compaction in exploration wells in the Rovuma Basin, offshore Mozambique

“…However, abnormally compacted mudstones are revealed by having a higher porosity at a given depth. Rapid burial of mudstones is usually the main cause of overpressured mudstones, but chemical compaction caused by the diagenesis of clay minerals may also contribute (El-Werr et al., 2017). Finding these abnormal mudstones intervals is a key to identifying zones of overpressure.…”

“…A major challenge for deep-water wells is related to overpressure, where drilling of high-pressure sediments may cause significant time delay in drilling, due to excessive pressure kicks, borehole instability, or stuck pipe incidents, and may even cause a complete loss of the well if not accurately predicted (Zhang, 2011; El-Werr et al., 2017). In some cases, drilling overpressured sediments has been reported to induce geological disasters (Davies et al., 2007).…”

Source rock evaluation and petroleum system modeling of the East Beni Suef Basin, north Eastern Desert, Egypt

“…Although the East Beni Suef Basin constitutes the major portion of Beni Suef Basin (Zahran et al, 2011), most of the published work focused on the West Beni Suef Basin (Makky et al, 2014;Khalil et al, 2016;Abd El-Gawad et al, 2017;Abdel-Fattah et al, 2017;El-Werr et al, 2017;Elanbaawy et al, 2017;Shehata et al, 2018aShehata et al, , 2018bShehata et al, , 2019Sakran et al, 2019;Edress et al, 2021), while little has been published on the East Beni Suef Basin (Abd El-Aal et al, 2015;Saber and Salama, 2017;Salem and Sehim, 2017;Tahoun et al, 2017;Rabeh et al, 2019) with no detailed focus on the hydrocarbon source potential and basin modeling.…”

Integration of mud logging and wire-line logging to detect overpressure zones: a case study of middle Miocene Kareem Formation in Ashrafi oil field, Gulf of Suez, Egypt

“…The abnormal pressure zones are due to the quick compaction of shale sediments, which is considered as one of the very important conditions to create these zones. The generation of abnormal pressure in the pore spaces happens if a pressure seal (impermeable barrier) is present, and fluids trapped and cannot escape (El-Werr et al 2017). The abnormal pressure must be controlled to prevent dangerous problems such as stuck drill pipes and blowout of wells during drilling operation (Danenberger 1993).…”