Perforation Spacing Optimization for Well Integrity

Abstract Small spacings between the perforation tunnels may exacerbate the failure behind the completion by connecting the failure zones in adjacent perforations. These instabilities threaten the integrity of the perforated intervals of the wellbore. It is common to evaluate the stability of perforation tunnels to optimize the perforation orientation, interval and planned drawdown pressure to avoid solid production, but the effect of the perforation spacing is usually ignored. Here, a workflow is presented for optimizing the phasing and shot density of the perforation tunnels to minimize the risk of formation failure in the completion zone. This is done using a series of numerical simulations designed to calculate the zone of impact developed around a single perforation with different orientations and downhole pressure and temperature conditions. Thereafter, a pragmatic approach is used to compare the simulation results against the calculated minimum spacing correspondent to different perforation designs (phasing and shot density). The proposed workflow introduces a practical approach to optimize the perforation phasing and shot density from the formation stability and completion integrity point of view. This geomechanical approach combined with the classic perforation design conducted by production and completion engineers reduces the risks of well integrity failure for its expected life span.