Reducing Geopressure Related Non-Productive Drilling Downtime: A Case of Recent Proposed HPHT Deep Exploration Well, Onshore-Shelf, Niger Delta Basin, Nigeria

Poorly predicted abnormal pressure has contributed to drilling non-productive downtime in most exploration fields in Niger Delta Basin. However, several advances have been made to improve pressured-related non-productive downtime during drilling. Despite the advances, it has become more critical during pre-drill geopressure prediction. This study has estimated Eaton’s and Bower’s prediction models ahead of the drilling bit in a recent drill campaign. The aim is to reduce non-productive downtime for a proposed 1000ft untested hydrocarbon reservoir (Kulon XII deep well) in the Onshore/Shelf, Niger Delta Basin. The study projected the accuracy level of Eaton’s or Bower’s prediction model ahead of drilling the Kulon XII deep well. Offset well result closest to the proposed High Pressure, High Temperature (HPHT) Kulon XII deep exploration well confirmed that pore pressure prediction at shallow depths (less than 11,750ft) confirmed that Eaton’s model predicted pore pressure below hydrostatic gradient, while Bowers model at same condition overestimated it. At depths greater than 12,000ft, the Eaton and Bowers prediction model matched with the measured pore pressure. Both models were used to predict pore pressure at deeper intervals of the proposed well. The predicted pore pressure profile from the offset well revealed the onset of mild overpressure at depths greater than 11,900ft. Therefore, the seismic velocity was scaled by a factor of +/- 5% to determine the mud weight that will be required for drilling of the Kulon XII deep well in order not to experience kick at depths greater than 13,000ft.