Robust Artificial Lift Solution for Ultra-Deepwater Heavy Oil Atlanta Field

Abstract

Most of the artificial lift strategies in deepwater environments require sophisticated and robust solutions, aiming to improve the system's run life and reliability. Due to that, oil companies choose only trustable technology and field-proven solutions for artificial lift design. This is the case of Atlanta Field's artificial lift project, with electrical submersible pumps (ESP) installed at more than 1,550 m water depth, to produce heavy oil. For Atlanta Field, the ESP must handle high viscous oil and emulsions at high flow rates to be economically feasible. To achieve this goal, it was deployed one of the most powerful ESP in the world with 1,550 HP induction motor and more than one hundred pump stages into the well. This is the largest ESP in-well successfully installed in Brazil. The artificial lift strategy adopted for Atlanta Field was an in-well ESP as primary method and an artificial lift skid (ALS) installed on the seabed for back-up. When the primary method fails, there is no in-well ESP replacement, because of high costs involved with workover and the back-up system becomes the main one. When the back-up system fails, the replacement of the pumping module is done by an AHTS equipped with active compensate crane for subsea installation. In this way, replacement costs are much lower than those needed to replace pumps inside the wells. So far, this artificial lift strategy has proven to be reliable and project results will be discussed in this paper. Strategies to optimize production will be addressed and observations regarding free gas ESP pumping will be made. After a period producing, the in-well ESP have failed, and the ALS became the main system to produce both wells, as planned. The project faced some challenges with ALS operation, since there was an expressive flow restriction in the in-well ESP. Experimental tests were permeformed to better determine the pressure drop caused by the flow through the pump stages and to propose a solution to the production restriction. By-pass valves were adopted in the project to avoid the mentioned issue. The well ATL-4 was drilled in March 2019. As this operation requires a drill ship, it was decided to perform workovers in wells ATL-2 and ATL-3 to replace the in-well ESPs and install the by-pass valves in the well's production string.