In some production scenarios in offshore fields, artificial lift provided by pumping methods is potentially more productive than the equivalent gas lift application. However, pumping systems require a high initial investment and the long-term reliability is still subject to industry improvements. Moreover, the cash flow implications are significant during any period of stopped production and intervention due to pump failure. These can be minimized with an Electrical Submersible Pump (ESP) configuration that allows production bypass and pump retrieval without the removal of the Christmas Tree and the associated well completion set.
A prototype ESP with this functionality will be installed at 1,400 m water depth in Jubarte field phase 1 development, offshore Brazil, in 2005. The ESP will be incorporated into a purpose built subsea capsule, designed for installation adjacent to the Christmas Tree. For the first installation, a rig will be used. It is expected that subsequent running and retrieval operations will be performed by cable using a low cost vessel.
PETROBRAS intends to use this solution in all (fifteen) production wells of Jubarte field phase 2. There is also a possibility to use it in the Golfinho Field phase 2 development (four wells).
PETROBRAS has large estimated potential reserves of heavy oil in Brazilian offshore locations. Much of this oil is in deep and ultra deep waters. Producing heavy oil in deep waters is a challenge, not only to Petrobras but also to other operators worldwide. To overcome this challenge, PETROBRAS created a research program, PROPES (Offshore Heavy Oil Program), inspired by the well-known PROCAP successful strategy. The objective of PROPES is to develop new technologies to make the offshore production of heavy oil fields feasible. Among the projects in PROPES portfolio is the one presented by this paper, Pumping Module on the Seabed, which proposes a prototype test of heavy oil pumping downstream the Wet Christmas Tree (WCT) at the Jubarte field, by the end of 2005, within the scope of phase 1 development.
PETROBRAS was one of the pioneers in electrical subsea pumping in offshore applications. The Electrical Submersible Pump (ESP) installed in 1994 in the RJS-221 well was the first wet completion application ever. Since then, the number of new ESPs installed by PETROBRAS was modest. Other operators have been using ESPs more extensively, for instance, in the Lihua, Lufeng and Otter fields. However, recent heavy oil discoveries in deep waters and the need to produce marginal fields are making the ESP an attractive alternative in PETROBRAS field development plans.
In the production of some heavy oil fields offshore, artificial lift provided by pumping methods is potentially more productive than the equivalent gas lift application. Figure 1 shows a comparison among different lift methods for a typical offshore scenario with a 17° API oil, for the Jubarte field.
Figure 1 - Liquid flowrate for different lift methods in Jubarte (available in full paper)