It is widely acknowledged that complex well completions involving highly deviated, extended-reach horizontal applications often direct the operator to choose coiled tubing as the optimum conveyance tool. This method provides the flexibility to run long and heavy guns, create static/under balance or spot fluids. However, due to the length and weight of guns used, a much larger dynamic load acts on a coiled tubing assembly, thereby requiring a comprehensive understanding of dynamic phenomenon in these applications. Consequently, numerical modeling for accurate prediction of pre-job coiled tubing perforating designs is critical to mitigate risk and ensure successful deployment in a cost-effective manner.
This paper focuses on several aspects of coiled tubing perforating: procedures, best practices, successful deployment, lessons learnt and most importantly, the modeling tools that are used to design and optimize a coiled tubing job. The modeling software utilized in this work is an engineering and scientific tool that simulates the dynamic response of a cased or uncased wellbore, its contents, and the porous rock formation to the energy released by gas-generating and stored pressure sources. Further, the tool successfully models the perforating event beforehand to mitigate risk and predict the viability of the process. The model is used to ensure the coiled tubing can be successfully deployed, manage/mitigate gun shock, recover the guns, etc.
Subsequently, the case histories presented in this study further emphasize the significance of careful job planning and the related modeling that is integral to the success of critical coiled tubing deployments. The first case history deals with the live well deployment of guns to perforate the upper section of a failed completion. Concerns about shock loading and inflow were successfully modeled in the software. Iterations of the model were run to monitor inflow and various underbalance scenarios. The outcome was a successful deployment and recovery of one thousand six hundred feet of perforating guns. In the second case of a complex HPHT well, concerns about shock loading and the effect of high volume in flow were modeled in the software to ensure a successful operation. The effect of shock on the coil and the completion were successfully modeled, resulting in two successful deployments. In another case, two subsea coiled tubing jobs using propellants are presented. The concern was the effect of the propellant on the coiled tubing and the completion. Extensive modeling enabled us to size the gun system and the proper amount of propellant to prevent issues. The results from the case histories and the insight provided by the dynamic modeling software illustrate that, irrespective of the complexity of the perforating job, careful job planning complemented by advanced dynamic modeling are critical to successful deployment of a coiled tubing perforating job.