Total in a World First with Subsea Gas/Liquid Separation
Begun in December 2007, development of the Pazflor oil field 150 kilometers offshore Angola is one of the biggest projects currently operated by Total. A number of technological challenges — including subsea gas/liquid separation, a world first — are being met to bring the field on stream successfully.
On January 30, 2011, the Acergy Polaris finished installing the three subsea separation units (SSU) for the Pazflor project, in 800 meters of water in Block 17 offshore Angola. The flagship innovation of the project, these units constitute a world first in terms of technology.
For Pazflor is the first-ever project anywhere to deploy a development plan based on gas/liquid separation at the mudline spanning several reservoirs. This milestone technological innovation is what will make it possible to meet the challenge of producing the heavy, viscous oil contained in three of the four reservoirs in this gigantic development in the Angolan deep offshore.
The Pazflor oil field comprises four reservoirs. One of them, Acacia was formed around 25 million years ago in the Oligocene and contains light oil. The other three — Perpetua, Zinia and Hortensia — are younger, dating from the Miocene, just five to seven million years ago. They contain more problematic oil that is heavier and much more viscous.
Subsea gas/liquid separation is the key to the economics of producing these challenging reservoirs, making Pazflor a deepwater trailblazer.
The subsea production system for Pazflor’s three Miocene reservoirs includes three subsea separation units. Each one consists of four retrievable packages: a gas-liquid separator, two hybrid pumps to boost the liquids, and a manifold to distribute the effluents to the separator and pumps. Purpose-designed for Pazflor, the hybrid pumps are yet another world first. They combine multiphase stages, compatible with the presence of gas in the liquid, and a centrifugal stage, to improve efficiency.
The SSUs are the culmination of several years of R&D work and a rigorous qualification program to ensure the optimum efficiency and reliability of this vital production equipment. Fabrication, completed in 2010, entailed nearly 350,000 man-hours of work.
With our newfound proficiency in subsea separation technology, combined with a standard production loop, we have demonstrated that we were right to decide to develop two types of oil with very different properties that require two separate subsea production systems.
Both systems will be connected to a single Floating Production, Storage and Offloading (FPSO) vessel. After departing South Korea on January 18 this year, the Pazflor FPSO is currently at sea, en route for Angola.