Case History—Combining Extreme Overbalance and Dynamic Underbalance Perforating Techniques in Ecuador

Abstract

The effective combination of propellants to generate a high-pressure pulse to create micro fractures has been proven to be successful in a number of wells in Ecuador.Recently, the inclusion of surge chambers in the bottom hole assembly has been proven to provide improved cleanup of the perforation tunnels created by jet perforators. This minimum surge pressure across the formation results in a dynamic underbalance that improves well productivity. Owing to the improved cleanup, there is a better path between the reservoir and the wellbore, which has demonstrated a more than 50% increase in well productivity. The ability to delay the opening of the chambers after gun detonation is critical in creating a dynamic surge from reservoir to wellbore, thus enhancing the dynamic flow and removal of fluids and solids from the perforation tunnels.This combination of overbalance and dynamic-underbalance immediately after perforating has also provided a method for cleaning perforation tunnels, even when perforating overbalanced with wireline-conveyed guns.This technique has been highly successful in the East Basin of Ecuador, especially now that near-wellbore stimulation techniques to clean the perforation tunnels can be achieved with wireline-conveyed guns instead of using a rig to provide tubing-conveyed perforating (TCP) services to create optimum conditions during perforating. This combination of techniques provides an effective solution at a reasonable cost that optimizes reservoir connectivity with the wellbore, significantly increasing the productivity index.However, for these techniques to be used successfully and create the necessary conditions to remove debris damage from the perforation tunnels, it is imperative that the software models and simulations be provided by experienced and well-trained engineers.Prior to the job, the service is modeled using state-of-the-art software simulators to predict the dynamic forces acting on the wellbore. When the job is executed, fast-gauge memory recorders are used to capture the pressure and temperature data at the time of the perforation event to validate the modeling. This technology has demonstrated great success in Ecuador by improving well productivity by as much as 50% when compared to other nearby wells in the field.