No abstract

The FPSO P-58 is located in a deepwater field and produces pre and post salt reservoirs. The artificial lift method selected for two post salt wells is the mudline ESP, where the equipment is installed in a submarine skid. The main advantage of this technology is to reduce intervention costs due to cheaper vessels. The concept was developed and tested in two Petrobras projects: Espadarte and Cascade-Chinook fields.Some of the challenges are related to the need for horizontal positioning of the equipment, due to the dimensions involved. This impacted the method of assembly and installation of the ESP in the capsule, as well as design of the protectors. The Mudline ESP has two pumps powered electrically in parallel and arranged in series hydraulically. In this project, the equipment has evolved in relation to the previous installations, in particular the inclusion of chemical injection, access to hot stab and the capability to receive a flow homogenizer.The system will begin operation in 2015 and it is expected that its runlife will be similar to the standard equipment installed in the well, but with lower intervention costs. Possible improvements for the next projects are the use of sensors on both pumps and the installation of the system with even simpler and cheaper vessels.Since the assembly of the pump and the whole skid is done onshore, the process can have a better control and supervision. Also, an integration test is performed before the system installation, which allows a complete evaluation of its performance.

This paper provides a general overview of the subsea Electric Submersible Pump ESP skid boosting system, and describes the technologies introduced to make the ESP system more robust, the resources brought together to move the required assembly tasks to a controlled onshore facility, the equipment validation program, and the initial experiences in installation and operation of the system.Production of the 17°API heavy oil from Jubarte requires some means of artificially lifting fluids to surface. The high installation and intervention costs associated to subsea ESPs has prompted an operator to search for alternate boosting systems. The mudline ESP skid provides a solution for more cost-effective boosting of fluids to surface in deepwater fields.The experiences gathered and results obtained with the operation of MOBO (Modulo de Bombeio, which is Portuguese for pumping module) ESP systems in the Jubarte and Golfinho fields have encouraged the operator to develop new ways for producing oil from these offshore fields using techniques to reduce considerably the installation and workover time and cost. In this way, the development of Jubarte Phase III uses a different arrangement for the mudline ESP, with the equipment installed in a horizontal skid instead of a vertical module. The skid comprises two horizontal ESP systems connected hydraulically in series and powered electrically in parallel by a medium-voltage drive located in a floating production, storage, and offloading (FPSO) platform. This setup reduces the size of the subsea assembly and allows use of a vessel of opportunity for deployment instead of a rig.The subsea ESP skid concept was developed and tested on two previous occasions: an extended well test in Espadarte offshore Brazil and a production module in the Cascade-Chinook development in the Gulf of Mexico. In this new project, the equipment has evolved in relation to the previous installations, with a new and larger ESP system, the inclusion of chemical injection, access to hot stab, and the added capability to install a flow homogenizer.The skid system design aims at improving economics for production of heavy oil fields while also addressing ESP run life concerns in these low gas volume fraction and high boost pressure deepwater applications.

Production in reservoirs located in deep and ultra-deep water that contain waxy crude oils faces a huge obstacle imposed by the low temperatures of the environment. When the waxy crude oil is subjected to a temperature below the Gelation Temperature, as in the case investigated in the present work, it exhibits a variety of non-Newtonian features: elasticity, plasticity, viscous effects, and time-dependency, which renders to this material a highly complex behavior. A crucial feature that is frequently ignored when the determination of the yield stress is being carried out is the timedependency nature of these materials. We demonstrate that this character has a significant impact on the measurement of the yield stress and, therefore, values obtained from a protocol that neglects time-dependency can be substantially different from a more careful procedure.