The ability to predict and reduce large perforating gunshock loads and the associated risk of damage and nonproductive time is very important because of the high cost of most wells, especially deepwater high-pressure wells.
The aim of this paper is to present the most current (as of 2014) capabilities in simulation software to predict perforating gunshock loads produced by hollow carrier guns. This is a joint effort between operators and service companies to promote the discussion on dynamic gunshock modelling. The end goal of this paper is to communicate to a broader audience of oil and gas companies the most current knowledge on predicting perforating wellbore dynamics and the associated gunshock loads and to look ahead for future developments in dynamic gunshock modelling.
Both low- and high-pressure wells are susceptible to gunshock damage when they are perforated with inappropriate gun systems and/or under adverse conditions. As of 2014, there are several software tools available to predict gunshock loads. These software tools help engineers identify perforating jobs with significant risk of gunshock damaged, such as bent tubing and unset or otherwise damaged packers, gun damage, wireline weak-point pull-offs, etc. When the predicted risk of gunshock damage is large, engineers can make changes to the perforating equipment or job execution parameters to reduce gunshock loads and the associated risk of equipment damage and nonproductive time. With the available gunshock software, engineers can also evaluate the sensitivity of gunshock loads to changes in the perforating equipment, such as: gun type, charge type, shot density, tubing size and length, rathole length, and placement/setting of packers and shock absorbers.
In this paper, we describe the main sources of gunshock loads. We present examples showing typical loads on tubing and packers, and we elaborate on the load levels that can lead to equipment damage. Simulation examples included in this paper also illustrate how to reduce gunshock loads by modifying the equipment used. We illustrate how small changes that cost very little to implement can lead to a large reduction in both gunshock loads and the associated job failure risk.