Statoil's efforts toward deploying a 'subsea factory' by 2020 are advancing, and the anticipated seabed processing systems are expected to yield greater production efficiency, improved recovery rates, and a reduced environmental footprint, executives said recently in Houston.
Components already are in various stages of being installed on different fields, primarily offshore Norway, Margareth Ovrum, Statoil's executive vice-president of technology for projects and drilling, told reporters during a Nov. 20 media briefing. Statoil has more than 500 subsea wells.
"We are going longer, deeper, colder," Ovrum said. Offshore platforms likely will not be feasible in some places for future developments. She envisions at least part of the subsea factory concept eventually being applied to projects in the Gulf of Mexico, Brazil, Tanzania, and the Arctic.
Statoil advocates subsea processing for both brownfield and greenfield projects, and its brownfield projects focus on increased recovery rates from Norwegian Sea reservoirs.
"I believe the subsea factory is the most interesting project in my career," Ovrum said, vowing not to retire until the subsea factory concept has been turned into reality. "This is my baby, and we are working very hard," she said with a laugh. Ovrum has worked for Statoil for 32 years.
Tasks required for a complete system include single and multiphase pumping, gas compression, separation of gas and liquids, produced water reinjection, and seawater injection.
Statoil's subsea factory is building on a toolbox of multiphase pumping and water separation installations from the late 1990s.
"In the early 2000s, we turned to the space industry for subsea materials," to deal with high-pressure, high-temperature conditions, Ovrum said.
Progress outlined
Statoil is on schedule to apply subsea compression on Asgard field, which it operates on the Norwegian continental shelf about 120 miles offshore.
A 1,800-tonne compression module was installed on Asgard this year after being sanctioned in 2011. Start up is scheduled for 2015. A smaller subsea compression project sanctioned for Gullfaks South also is scheduled for start up in 2015.
"As of 10-15 years ago, no one could imagine having a complete compressor on the sea floor," Ovrum said, adding that "real estate was improved" so that the Asgard compressor is completely flat on the seabed. She calls the project "the world's first subsea compression."
Ovrum estimates the Asgard subsea compressor will increase recovery by up to 280 million boe.
Statoil's analysis showed pressure in the Midgard and Mikkel gas reservoirs was becoming too low to sustain their ability to produce to Asgard B in future years.
"Moving compression to the seabed gives both improved energy efficiency and lower costs compared with keeping it on a platform," Ovrum said. "The closer to the well we compress the gas, the higher the efficiency and the production rates."
Lars Hoier, senior vice-president of technology for development and innovation, said a short-term focus for Statoil is increased oil recovery rates.
Industry's average recovery factor worldwide is 35%, Hoier said, adding Statoil's recovery factor in 2011 was 50%, and the company aims to achieve 60% average recovery worldwide.
"This is really a tough ambition," Hoier said. Statoil is investing billions of dollars to better understand reservoir flow patterns and achieve optimal drain for more efficient wells, he said.
The company's medium- and long-term goals include using a complete subsea factory production hub and transporting market-quality oil and gas to an onshore site. That could involve greenfield developments transporting gas 490 miles and 30 miles away for heavy oil.
Geir Tungesvik, senior vice-president, drilling and well technologies, said the use of steerable drilling liner (SDL) has simplified drilling in unstable formations and improved the recovery rate from mature fields.
Baker Hughes Inc. is working with Statoil on second-generation SDL, Tungesvik said, estimating that the first use of SDL on a field gave Statoil access to an additional 350,000 bbl. Statoil also is developing new strategies and standards for subsea horizontal trees and vertical trees, he said.
