Statoil has received consent from the Petroleum Safety Authority to use the COSLInnovator mobile drilling facility for production drilling on the Troll field using the controlled mud level method.
The consent covers the use of COSLInnovator for production drilling on 8½in. sections in well 31/2-L-22 on the Troll field using the controlled mud level method.
Controlled mud level (also called dual gradient drilling – DGD) is a new technology, which Statoil has tested as a pilot project in another production well at Troll. The company now wishes to perform a new pilot study in order to implement improvements and experiences from the first pilot, before widespread deployment of the technology.
According to Statoil's application for consent, in time the controlled mud level method will allow wells to be drilled in depleted reservoirs when it is no longer possible to drill using conventional methods.
COSLInnovator is a semi-submersible drilling facility constructed at the Yantai Raffles Shipyard in China. The facility was issued with an Acknowledgement of Compliance (AoC) by the PSA in 2012, and has been on contract to Statoil on the Troll field since then.