Risk Evaluation Technique for Tubing-conveyed Perforating (SPE 152419)

High-pressure wells are susceptible to gunshock damage when they are perforated with inappropriate gun systems. This paper presents a simulation tool that predicts Tubing Conveyed Perforating gunshock loads reliably. This tool enables completion engineers to evaluate the sensitivity of gunshock loads to changes in gun type, charge type, shot density, tubing size and length, use of shock absorbers, rathole length, and placement of packers, among others. When planning perforating jobs in high-pressure wells, engineers strive to minimize the risk of equipment damage due to gunshock loads. The software described here helps engineers to identify perforating jobs that have a risk of gunshock related damaged, such as bent tubing and unset packers. When predicted gunshock loads are large, changes to the perforating equipment or job execution parameters are sought to reduce gunshock loads and the associated damage risk. We compare software predictions with high-speed pressure gauge data for each perforation job. Gauge pressure data shows that predicted wellbore pressure transients are accurate both in magnitude and time. Peak sustained pressure amplitudes at the gauges are on average within 10% of software simulated values, both for gun underbalanced and gun overbalanced conditions. For cases where shock absorbers were used, residual deformations of crushable elements correlate well with the peak axial loads predicted by the software. The software is able to simulate perforating job designs in a short time, which allows engineers to optimize perforation jobs by reducing gunshock loads and equipment costs. The ability to predict and reduce gunshock induced damage in perforating operations is very important because of the high cost associated with high-pressure deepwater operations. With the software tool described in this paper engineers can optimize high-pressure well perforation designs by minimizing the risk of gunshock related damage and the associated rig time losses.