Case Story: Dynamic Underbalance Applied With Gun Hanger Technology in Mature Field
Authors: Patino Jorge , Gainza Fausto , Cosios Gustavo 
Published: September 2016

Abstract
Mature fields provide a good opportunity for oil producers because many of these fields contain reserves that can be recovered economically with a representative return on investment (ROI). Optimal production from perforated zones is always the goal; however, minimizing/preventing formation damage during a perforation event can present challenges.
This paper presents a case study wherein an operator perforated an interval using static underbalance (UB) and dynamic underbalance (DUB) techniques to achieve oil production with minimal formation/skin damage and perforation tunnel cleanup. Both techniques were used with gun hanger technology in an artificial lift completion, providing oil production that exceeded the operator's expectations.
Technology advancements have provided renewed opportunities for hydrocarbon production from wells in mature fields. One such advancement includes application of a surging effect that uses an atmospheric chamber and creates DUB immediately after a perforation event. The surge chamber creates an instantaneous in-situ negative pressure in the wellbore that surges and cleans the perforated interval (Haggerty et al. 2012). This helps improve the well inflow conditions and effectively reduces the formation damage normally generated by the perforation event (Poveda et al. 2015), which is further increased with the control fluid change when the production pipe is removed with tubing-conveyed perforating (TCP) systems.
Another advancement uses an electronic firing head (EFH) that can be programmed for a wide range of applications with different actuation times (up to 18 days). This EFH can also be reset up to fifteen times without locking the electronic system.
The perforating gun string can be set on depth using an automatic-release gun hanger (ARGH) system. The ARGH helps run the electrical submersible pump (ESP) to the design depth as part of the well completion.
The ESP is electrically tested while running in the well with the production pipe and electric cable. Once on depth, the operational pump test is conducted while evacuating the well-control fluid. This provides the designed UB as the initial condition for firing the perforating guns, which induces the interval oil production.
The ARGH hydraulic system provides sufficient time for all designed effects in the formation. The purpose is to minimize the formation damage and provide optimized production.
The well can be put on production at the end of the sequence steps designed with the ESP because the well is prepared in advance. This can help save up to two days of completion setup time in a pipe-conveyed perforating operation.
The complex processes involved in these operations have been simulated with industry tested and proprietary software programs. These programs helped confirm the desired effects can be achieved in production intervals to obtain the greatest oil production in optimal conditions.
The simulations also account for the physical effects on the ESP, pressure and temperature sensors, and casing or liner installed in the well.