The paper is based on experience gained during drilling in Potwar basin, on-shore Pakistan. The high cost of wells are primarily due to long drilling times resulting from extremely difficult drilling conditions, arising from abnormally high formation pressures. High pressure water inflows and loss circulations have led to premature abandonment of several wells on account of collapsed casing, bridging, caving, blowouts and cratering around the wells.
The post-Eocene Siwalik formations in the Potwar basin are notorious for abnormally high formation pressures and reversal of pressure regimes in the sedimentary sequence. Pressures close to geostatic have been encountered at shallow depths.
The aim of the paper is to take a close look at the mechanisms responsible for the generation of overpressure, identify problem areas, examine available options, keeping in view present drilling technology and equipment limitations, and finally recommend operational strategies to handle such situations.
Planning of wells, monitoring of drilling operations, selection of kick control procedures and wellbore integrity are considered to be critical factors for successful operations.