For its Snøhvit development in the Barents Sea, Statoil ASA decided to use “dry” premium connections to eliminate all chemical discharges to the ocean from the casing and tubing installation.
After evaluating and testing the TenarisBlue Dopeless technology, Statoil selected it for use on all the strings to be run in this development. Statoil applied the dopeless technology using a variety of sizes and grades ranging including 14-in. 82.2 lb/ft N-80; 9 5/8-in. 53.5 lb/ft P-110; 10 3/4-in. 60.7 lb/ft P-110; 7 5/8-in. 33.7 lb/ft L-80 Cr13; 7-in. 32 lb/ft L-80, L80 Cr13 and Cr25 superduplex.
The harsh environment of the Hammerfest area tested the resistance of the dopeless connections to corrosion. All the products supplied for this project were finished and shipped in dry condition from Tenaris’s mills in Japan, Mexico, and Italy, and were stocked at the company’s Polarbase Hammerfest. So that the materials could endure the climatic conditions (including temperatures dropping to -40° C.), Tenaris developed a thread protector design that seals tight against the pipe body and keeps the connection dry.
Although the main driver for the use of this technology was the reduction of the environmental footprint in this pristine area, other factors were also considered:
- An improved working environment in terms of occupational health hazards at the onshore base, as well as at the rig. The dopeless connection allows the implementation of totally hands-off pipe handling to be much more feasible than traditional doped connections.
- Reduced handling: No removal of storage dope onshore, no application of dope onshore or offshore.
- Safety issues: Fewer operations on the pipe lead to less potential for injuries. No dope applications on the rig floor.
- More efficient running, handling on the rig: The handling and running of pipe on the rig is easier and faster than with traditional connections.
One of the strings was particularly challenging. For the 25% chrome liner on a CO2 injection well, there was no field experience with use of the dopeless system because this is a specialty pipe with high galling tendency (due to its high chrome-nickel content). Both parties agreed to test the TenarisBlue dopeless liner connections to validate that they would work properly. The alternative to the dry solution was to use API modified thread compound, but this product contains dangerous chemicals that have been banned from use in the Barents Sea.
Tests of the connection in validated the dopeless design for high chrome alloys. The string was installed in February 2005 with no rejects and a maximum running speed of 10 joints/hr.
Currently, the third well is being drilled at Snøhvit and all casing and tubing liners have been safely installed.