Abstract
This paper represents a challenging rig-less intervention in highly deviated wells with heavy oil that has always been a challenge to conventional electric line (e-line) that is not a valid intervention technique due to its inherent limitations in these harsh environments. Electric Coiled Tubing (E-CT) was utilized not only to achieve safer deployment of the guns, but also to allow real-time operations on three wells which were inaccessible due to heavy oil content and restricted e-line accessibility.
A case study is presented for a campaign performed using E-CT to convey the perforating string while pumping nitrogen (N2) to lift the well and achieve flowing under-balance to maximize perforation clean-up and minimize skin. Real-time readings from gamma ray, pressure and temperature sensors were used to accurately position the guns, generate the desired dynamic underbalance, and finally validate successful detonation based on pressure and temperature responses. This was achieved while N2 lifting and firing the guns to optimize the required under-balance value providing immediate feedback related to the production gain to determine the zonal contributions and maximize the economical production gains. Dynamic wellbore behavior software modeling was also used to predict the dynamic under-balance effect for maximizing perforation efficiency.
Deployment of E-CT was very challenging in terms of operational execution but was extremely beneficial for the safety of the pipe during such operations. A total of 13 runs comprising of milling, tubing cleaning and drifting were performed to remove the accumulated scales inside the production tubing and to ensure full accessibility to target intervals. Coiled Tubing (CT) dynamic modeling software was utilized to simulate the N2 rate needed to achieve the target underbalance while maintaining safe perforating parameters for the CT while firing the guns. As a result of software simulations, one of the three wells was then recommended for an acid wash treatment which achieved very effective results.
15 perforation runs were performed on the three wells re-perforating a total of 188 ft of interval, resulting in a production increase of more than 300%. This was a significant improvement compared to the previous campaign carried out in 2017 where perforating in static conditions showed no increase in production without work-over rig intervention. E-CT intervention also eliminated the need for waiting on rig schedule and avoiding deferred production.