Publications

Five wells were drilled to produce gas from a sandstone formation with gross intervals of 314-696 ft. The operator required underbalanced perforating to improve perforation clean-up and avoid formation damage from the wellbore fluid. Underbalance (UB) perforating was carried out in previous campaigns with a modular gun system conveyed on wireline, allowing the perforation guns to be dropped into the rat-hole after firing. However, this technique couldn't be implemented for these cases due to a high deviation angle and limited rat-hole length. Several options were available, such as the Coiled Tubing (CT) live-well deployment system and modular gun with detaching system. However, these options increase the risk and rig time requirements. Therefore, Tubing Conveyed Perforating (TCP) shoot and pull was selected as the primary technique with the risk of formation damage during well kill operation. To minimize formation damage, a Relative Permeability Modifier (RPM) was pumped to reduce fluid loss and allow the well to be killed with minimal or no damage. RPM was selected as it is a solids-free fluid compatible with the formation that doesn't require a post-clean-up operation, potentially saving 2-3 days of rig-time. The TCP gun was run with a circulation sub, allowing oil-based fluid to be pumped above the circulating valve to create a 600 psi underbalance on the first well while the rest of the wells were perforated overbalanced. Once the TCP gun was fired, oil-based fluid was circulated with the brine, and RPM was placed into the formation to create a +/-300 psi overbalance condition. Once the well was killed, the TCP gun was pulled safely to surface. The RPM successfully reduced fluid loss in all five wells, where the highest static loss rate encountered after perforating was 160 bbl/hr, which was reduced to 7 bbl/hr after the RPM was pumped.