These projects are described in outline below.
The 42″ Asgard Transport pipeline runs some 684km from Asgard B Platform to the landfall site at Kalstø, Rogaland, Norway. The ERB (Export Riser Base) consists of 28″ pipe with four 14″ risers from the platform. The 28″ pipe runs 500m and then expands to 42″.
The RFO (Ready For Operation) pig developed in 1999 was run from the land fall site to the receiver on the ERB, ie 684km of 42″ line reducing down to 28″ for the last 500m. The RFO pigging tasks involved waterfilling the pipeline for hydrotest and dewatering with a glycol train.
Therefore the pig needed to be able to: –
- reduce from 42″ to 28″, whilst keeping the dP to a minimum in the 28″ line;
- provide the best possible seal along the entire pipeline.
Based on this the Asgard RFO Pig was developed, using: –
- FTL Seals Technology Limited suspension design which keeps the pig exactly on the centreline of the pipeline;
- Normal disc type seals, but with Buckle inducers to allow the seals to fold up into the 28″ line. This was based on our previous work on upheaval buckling and in conjunction with Arne Vingerhagen, Jim Cordell and Chris Kershaw.
Note that the supporting function and the sealing function have been essentially separated here. This provided Statoil with an excellent dewatering run in the line with the lowest ever measured volume of water in glycol.
This year we are looking at using these same pigs for the operational case in the opposite direction (28″ up to 42″ in gas). The issues are recovery of seals after permanent set and compressible effects at the expansion to 42″ due to the sudden drop in friction.
RST Projects Limited in Musselburgh, Edinburgh required to build a test loop for testing their pig data logger, the SAAM unit. Pipeline Research Limited was contracted to provide a conceptual design of the facility based on previous experience with testing and with such facilities. A concept was devised; initial sources of components were sourced and passed to RST Projects for implementation.
The Norne Heidrun pipeline runs 160km from Norne to Heidrun in a flow bundle. Initially, the pig is launched vertically into a 10″ riser, for about 1km. Exit from the riser connector, into 10″ x 16″ expansion section, through a check valve and through and wye piece. In addition there was a 5D bend on the 16″ line. The challenge was to come up with a suitable pig and sealing system to allow dewatering with Glycol on this pipeline.The main challenges were: –
- Overcoming the permanent set in the seals and allowing expansion from 10″ to 16″ with out loss of seal…solution provided by Pipeline Research Limited;
- Correct design of the seal to allow buckling in 10″ and full seal in the 16″…Solution provided by Pipeline Research Limited;
- Negotiating the 16″ wye and the 16″ bends (one demands a long pig, the other a shortened down pig).
Besides providing the basic sealing solution for this pig that fixed the pig body dimensions from an early stage, Pipeline Research Limited are involved in the testing of the pig at Krst’ in Norway. Thanks to the correct seal selection at the outset, this became a matter of optimising from an early stage.
The Gullfaks Satellites Phase II pig development was a fast track Multidiameter pig development for Statoil. This demanded that in order to short track the testing, the right components were required to be on site when testing begun so that the correct solution could be converged on. Pipeline Research Limited provided the design of the main 14″ sealing disks that were again design to buckle in the smaller lines and seal correctly in the 14″ line.
Additionally, modeling of the pig as a whole in the 14″ line allowed a stable pig to be developed. We have since learned that this pig has been used successfully in the pre-commissioning of this pipeline.
Study into the feasibility of using dual diameter pigs to pre-commission the planned Kvitebjorn pipeline. The pigs are also required to operationally pig the line, and to act as batching pigs for the inspection pigging of the line.
A base case dual module pig was proposed for the job. Several challenges were addressed such as the compressible effect at the expansion between the two line sizes, design criteria for the connector between the two modules and wear/permanent set of the seals after negotiating the small diameter pipeline.