STAVANGER, Norway – Statoil (OSE:STL) has various schemes under way to extend production from the Gullfaks field in the Norwegian North Sea.
Gullfaks was the first field the company developed and operated. The field came onstream in 1986.
Production declined at the end of 2010 following overpressure in the formations above the reservoir. This was caused by injection rates that were too high, and integrity issues with certain wells. Injection had to be stopped, along with flow from 50 of the field’s 180 wells.
“In 2011 and 2012 we repaired the weak integrity wells and stabilized the injection of water,” said Gullfaks vice president of operations Gunnar Nakken. “Water injection is now carried out at a pressure that does not damage the overburden, while at the same time we are endeavoring to gradually increase total water injection rates by operating a greater number of injection wells.”
Over the past three months, there has been 97% regularity on the Gullfaks A platform.
To improve understanding of the overburden Statoil has compiled large volumes of data over the past few years, including optimized 4D seismic, core samples, and results of productivity and pressure tests. Additionally, seabed areas have been mapped – the Gullfaks field geology is complex due to the migration of oil and gas over several million years.
A new well design addresses the overburden issue, allowing production drilling to re-start on the Gullfaks B and C platforms.
Conditions are more complex in the area around Gullfaks A. New well paths have been devised to avoid high-pressure areas. And new long-term drilling programs are in place for all of the field’s platforms.
On the satellite field south of the main field, two new subsea templates and six additional wells are being installed in order to boost recovery by 46 MMboe, under a NOK 8.5-billion program ($1.5-billion). Offshore installation work will start next summer. Two drilling rigs are currently operating on the field.