Subsea Equipment

With the search advancement for new oil and gas reserves in offshore fields located in regions increasingly distant from the coast, in deeper waters and geological formations, the technology of subsea production systems has undergone a strong advance. In this scenario, production systems need the two main areas of the ALFA Research Group, which are Artificial Lift and Flow assurance. Among the topics that comprise this area are boosting equipment, separation systems, valves and control equipment and others. Below are some of the most relevant themes explored by the research group.

a. Vertical Separator

Vertical Annular Separation and Pumping System (VASPS) utilizes both gravitational and centrifugal forces to separate gas from the production stream. VASPS is an innovative integrated two-phase subsea separation and pumping system, with a high separation capacity between the liquid and gas phases, even on the seabed. VASPS is a field-proven concept. It was operated for a short time until its first operational failure in 2001. VASPS was the operated from 2004 until 2008, that is, for almost four years without interruption when there was a failure in the electrical connector at the ESP (Electrical Submersible Pump).

The VASPS technology was developed in partnership with international oil companies (BP, Conoco, Agip, Mobil, and Baker Jardine) through a multi-client project. It began after initial studies in 1990. In 1997, the pre-submarine phase was developed in the PETROBRAS test field, located in Atalaia, Brazil. PETROBRAS developed R&D projects with the University of Campinas (UNICAMP) between 1994-1997 and 2000-2002, and this was central for the development of VASPS technology.

b. In-line Separator

In-line flow segregators based on axial induction of swirling flow have important applications in chemical, processing, and petroleum production industries. Compact oil–water–gas separators are often required in the processing industry but are essential in offshore petroleum production. A compact design is provided by the in-line axial hydrocyclone, which takes advantage of the pipe geometry of the incoming oil–water mixture. The segregation of gas bubbles and/or water droplets, dispersed into viscous oil by swirling pipe flow, may be beneficial by either providing a pre-separation mechanism (bubble and/or drop coalescer) or, in the case of water-in-oil dispersions, by causing a water-lubricated flow pattern to establish in the pipe (friction reduction).

The ALFA group has been working on this topic, contributing to innovative solutions, some of which are already patented for commercialization.

c. Subsea boosting

As deepwater fields mature, the reservoir pressure can become insufficient to drive the hydrocarbon to the surface as the pressure must overcome the significant weight of the overlying liquid column. Thus, the production decreases and, below a certain flow rate, the reservoir becomes uneconomical for operation and needs to be abandoned. To maintain the production plateau or enhance the hydrocarbon recovery, boosting systems are required to provide pressure support for the reservoir.

In remote fields with subsea tie-back, pressure boosting effectively allows tie-back distances to be increased. Increasing the flow rate could enhance economy by reducing the number of wells, and accelerated production could provide greater up-front financial returns. It may be possible to convert smaller marginal fields into an economically viable development. In addition to the operational advantages, placing the equipment on the seabed offers advantages in terms of size limitation, operational safety, and intervention costs.

In the last decade, the ALFA group has been working in this area with research projects for the main oil operators in Brazil, contributing to the development of this technology. Operational instabilities, thermal transients, degradation of viscous performance, and development of compact pumps are among the scientifically explored subjects in the work.