Laboratory Experiments Provide New Insights into Underbalanced Perforating

TLDR

Underbalanced perforating is the primary method for removing perforation damage and maximizing productivity, with static underbalance—the wellbore to pore pressure difference—identified as a critical parameter through theoretical and laboratory core studies. We now report on a new series of laboratory experiments conducted on outcrop cores under more representative downhole conditions. The experiments revealed that previously neglected parameters significantly alter perforation productivity, showing that static overbalanced perforating can be as effective as underbalanced and suggesting a new strategy to reduce damage, thereby reshaping our understanding of damage removal mechanisms and informing future perforating job designs.

Abstract

Abstract Perforating underbalanced has become the primary means of removing perforation damage and maximizing productivity through a cased and perforated completion. The level of static underbalance (wellbore to pore pressure difference prior to perforating), considered the critical parameter in achieving acceptable productivity, has been investigated theoretically and experimentally through testing on outcrop and reservoir cores under laboratory conditions. We now report on a new series of laboratory experiments conducted on outcrop cores under more representative downhole conditions. Investigation of previously neglected parameters produced profound differences in perforation productivity. In some circumstances static overbalanced perforating proved to be as effective as static underbalanced perforating. The surprising results on underbalanced and overbalanced tests suggest a new approach to minimize perforating damage. Not only do these results impact our understanding of the mechanism of perforation damage removal, but they also have important implications for future design of perforating jobs.