RIASSUNTO
ABSTRACT
The Occidental consortium, partly in conjunction with Texaco, has constructed in water depths up to 475 feet, a 226 mile system of 16, 18, 24, 30, 36 and 48 inch oil, gas and treated water deballast pipelines in the North Sea, which, as of the end of 1979, has transported more than 300 million barrels of oil. Incorporated in this system are various subsea connectors including 13 Hydrocouples, four Cameron collet connectors, several flanges and swivels and three hyperbaric connections. Developments over the past two years have included the field installation of three deep water risers together with special subsea WYE connections for potential future users. This paper describes the salient features and history of the system, and highlights some of the problems encountered together with the methods and techniques of the solutions undertaken. Some of the topics included in the paper are:
Erection of the World's deepest field installed riser.
Existing and future WYE piece installations.
pipeline provisions for future booster platforms.
Pressure testing, leak detection and repairs.
Sub sea connections.
Span corrections and pipeline protection.
Terminal SPM system and lines.
Inshore approaches and shore pulls.
Contingency repair capabilities.
INTRODUCTION
The Piper Field was discovered on UK North Sea Block 15/17 in January 1973. Shortly after the test of the first appraisal well at a combined rate of 32,000 barrels per day in March 1973, the search for a terminal to receive the oil was initiated. The Orkney island of Flotta was chosen from a short list of nine locations, and pipe was ordered for the 127 mile, 30 inch main oil line (MOL) The majority of the pipeline was laid in 1974 utilizing two conventional lay barges and two trench barges. A twin system of 36 inch deballast and 48 inch loading lines was laid to each of the two single point mooring towers which were being installed in Scapa Flow. A 36 inch effluent line was installed south of Flotta to disperse treated deballast water.
The Claymore Field was discovered on Block 14/19 in May of 1974, and after several appraisal wells, plans were made to link the platform to the piper-Flotta trunkline. A seven mile, 30 inch spur line was laid between the Claymore Platform location and a TEE in Block 14/14 during 1975. A 22 mile, 16 inch gas line was laid between piper and Claymore during 1976 to provide means for injecting Piper gas into the Claymore producing formation.
During 1978, the OXY Group, in conjunction with Texaco, installed a gas conservation pipeline system to deliver piper and Tartan gas to the Total Frigg /St Fergus system via the MCP-Ol compressor platform. An 11.5 mile, 18 inch spur connects Tartan to piper and a 33.5 mile, 18 inch line connects Piper to MCP-Ol. During 1979, Texaco laid a 16.5 mile, 24 inch oil line from Tartan to Claymore to effect delivery of Tartan crude to the Flotta trunkline. This system is the first such system installed and producing in the North Sea.