Abstract
The application of artificial lift in deepwater environments is constantly evolving due to a growing need for more sophisticated and robust completions that improve run-life expectancy and reliable deployment. The downtime associated with disruption of functionality while lowering a completion string in the well or dealing with a string stuck in hole can be a major concern because it can lead to an expensive workover or even well loss when fishing operations are unsuccessful. Because of this, most oil producer companies complete their wells only with field-proven or stringently qualified tools. That is the case of two subsea wells recently completed in the Atlanta field (14°API oil) with an electrical submersible pump (ESP) in more than 1,550 m water depth.
What makes the two initial wells unique to date are the large capsules (OD and length), high-power ESP and technology used to protect the lines going downhole. In the heart of each capsule there is a 1,500 HP ESP unit capable of pumping 12,000 bbl/d of viscous oil. Deploying such large systems inside 9⅝-in. capsules was already a great achievement. Nevertheless, the biggest challenge was to deal with the lines (two chemical injection, reservoir monitoring and hydraulic control) that had to go deeper than the ESP system. Even with the use of clamps, passing these lines outside of the capsule imposes a high risk of damaging them in the well's horizontal section or getting them stuck if the lines broke and wrapped between the capsule OD and the casing.
Overcoming this risk was possible through the implementation of a breakthrough idea that consisted in closing the bottom end of the 9⅝-in. capsule with a hydraulic retrievable packer instead of a torqued crossover, as is usually done in ESP capsules. The packer has the advantage that setting it doesn't create any relative movement of the feedthrough lines with respect to the capsule body, so all lines that must go deeper pass through without damage during closure of the capsule's bottom end. Splice subs above and below the packer make it even easier to pre-install the lines before shipping offshore.
Assembly was a breeze and the capsules were successfully pressure-tested to confirm there was no leakage before installing them in 11¾-in., 60.7-lb/ft casing at an inclination angle of 75°. All lines were commissioned and proven functional after finishing the completion job. These are the largest ESP capsules successfully installed in-well in Brazil and probably in the world with feedthrough lines crossing and protected inside the capsule. The creative concept can be extended to other wells and is very valuable to manage the risk of damaging the lines in ESP capsules.
