High-pressure wells are susceptible to gunshock damage when they are perforated with inappropriate gun systems. This paper presents a simulation methodology to predict Tubing Conveyed Perforating (TCP) gunshock loads reliably. This methodology 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 methodology described herein helps engineers to identify perforating jobs that have a risk of gunshock related damaged, such as bent tubing, damaged automatic gunstring release systems, 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 risk.
When fast-gauges are run we compare software predictions with high-speed pressure gauge data from the actual perforating jobs. 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 simulated values when the reservoir flow response is well represented. When shock absorbers are used, residual deformations of crushable elements correlate well with predicted axial loads. The methodology described herein allows engineers to evaluate perforating job designs in a short time, which in turn allows the optimization of perforating 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 deepwater operations. With the methodology described in this paper engineers can optimize well perforating designs by minimizing the risk of gunshock induced damage and potential rig time losses.