Statoil, the Norwegian oil and gas company, were partners in the Nam Con Son development in Vietnam. The development was for a 26in. x 362km gas pipeline from an offshore platform to the onshore terminal. The pipeline included an asymmetrical wye piece for a future field tie-in.

The produced gas was expected to generate substantial levels of condensate that would have to be removed at regular intervals. The clients preferred method of condensate removal was to run spheres, as this would provide easier handling and also allow multiple spheres to be loaded ready for automated launching. However, the use of spheres would pose several problems, as wye connections are generally not sphere friendly and can cause spheres to “stall” due to a loss of seal and drive.

Pigtek were awarded a contract by Statoil to provide consultancy and engineering services for pig and sphere proving trials. This involved working closely with Statoil engineers to review existing wye and sphere technology to evaluate capabilities.

The Statoil and Pigtek team re-engineered the internal features of the wye and sphere flow tees to make them pig and sphere friendly. Single and Dual Module Pigs were also designed to provide optimum performance through these features. Our scope of work also included the design of “wet buckle” pigs for contingency measures.

The following stage of development was to test the pigs and spheres through the newly designed system. To achieve this, a full scale trials rig was designed and produced. The majority of pipework, including pig traps and sphere tee were manufactured in the UK. The full size wye piece was manufactured in Norway using transparent GRP to enable the behaviour of the pigs and spheres to be viewed as they passed through the wye.

All trials were conducted at the purpose built Statoil test site at Kårstø, Norway. As a result of the trials, technical data was obtained on equipment performance that enabled a full specification for pigs and spheres to be produced.