Dynamic Underbalance Applied with Gun Hanger Technology for Early Oil Production with Artificial Lift System
Authors: Patino Jorge , Gainza Fausto , Cosios Gustavo 
Published: August 2016

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 in which an operator utilized a holistic aproach of a gun hanger in conjunction with artificial lift perforating solution to address formation fluid compatibility challenges while optimizing the perforations and perforation tunnel cleanup. This solution incorporated an advanced technical design with mechanical hardware.

By designing a perforating solution using both static underbalance (UB) and a dynamic underbalance (DUB) technique to achieve oil production with minimal formation/skin damage and marrying this solution with gun hanger technology in an artificial lift completion, has resulted in oil production exceeding the operator's expectations.

Technology advancements have provided renewed opportunities for hydrocarbon production from operator wells in mature fields. One used advancement includes application of a surging effect that uses an atmospheric chamber and creates Dynamic Under Balance immediately after a perforation event. The surge chamber creates an instantaneous in-situ negative pressure in the wellbore that provides a localized differential pressure that cleans the perforations (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. 2013). By addressing formation fluid compatibility challenges, one could reduce the formation damage normally generated by the kill fluid introduced in the shoot and pull operation with tubing-conveyed perforating (TCP) systems.

To acheve this, another design advancement is to use 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 be reset up to 15 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 to position the perforating string, detached from the completion string (ESP) to avoid shock loads from the perforating event interfering with ESP 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 static Under Balance 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 2 days of completion setup time in a pipe-conveyed perforating operation with the fluid change and the consequent formation damage.

The complex processes involved in these operations are carefully simulated with industry tested and proprietary software programs. These programs help to confirm the desired effects can be achieved in production intervals to obtain the best 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.