SPE-180311-MS Finite Element Modeling to Determine Perforating Gun Collapse Failure Modes and an Engineered Solution
G. G. Craddock (Halliburton) | Jim Wight (Halliburton) | Kevin Harive (Halliburton)
SPE Deepwater Drilling and Completions Conference, 14-15 September, Galveston, Texas, USA
2016. Society of Petroleum Engineers
Three-dimensional (3D) finite element analysis (FEA)-based shock software is the next step in downhole shock modeling. This software uses a finite element and a fluid tool that simulates gun behavior on gun strings and adjoining tools, including perforation and subsequent stress conditions. By examining temporal stress predictions at element locations, failures can be estimated based on these numbers. On a recent perforating operation, there was an undesired event that resulted in a collapse of the spacer section within the perforating string. The event flattened spacers, but did not ruptured them, resulting in not damage to other sections. This event highlights how localized dynamic forces could be over looked in the present 1D industry dynamic modeling software. As part of the planning process, the current industry standard shock software was used to simulate the string and predict the likelihood of failure. The models showed no failure flags; additionally, post-operation models did not predict the downhole events that occurred. As part of the investigation into the events, this modeling shock software was used to provide a more detailed model of the event. These models provide a full 3D representation of the string and allow a much more detailed understanding of the pressures and stresses during the perforating event. The models clearly showed the string design was not optimized for the localized dynamic event and there was a risk of collapse. Pressures were plotted as a function of time at locations on the outside of the spacers, safety spacer, and loaded guns. The results showed pressures outside the spacers, which exceeded static threshold values and lasted for extended durations. Other regions, such as the safety spacer, did not show this effect at above static threshold magnitudes. As well as being able to reproduce the collapse event , work was taken a step further to examine mitigation designs that could be used to help prevent these types of issues. It was possible to test several of these designs using the 3D FEA-based shock software to validate their functionality..