The Deepwater Pipeline System on the Jolliet Project

Abstract

ABSTRACT This paper describes the design and installation of the deepwater pipeline system which transports the oil and gas production from Conocors Jolliet Field in the Gulf of Mexico. This pipeline system used 12 miles of flexible pipe and 42 miles of conventional rigid steel line pipe. The pipeline system has pipelines in water depths as deep as 1760 ft. and as shallow as 230 ft. The paper describes the installation of flexible pipe risers at the TLWP, the laying of flexible pipe through rough seafloor conditions, the installation of rigid steel pipes in 1400 ft. water depth, and a seafloor connection system to facilitate tie-in of future production. INTRODUCTION The deepwater pipeline system for Conocols Jolliet Project required the use of many different aspects of offshore pipelining. The project involved two distinctly different pipeline systems - a flexible pipeline system and a conventional rigidsteel line pipe system. Each system presented its own particular challenges. The complete pipeline system installed by Conoco for the Jolliet Project required the installation of a total of 54 miles of both steel and flexible pipe. The conventional steel line pipe system crossed 42 miles of varying sea bottom terrain. These pipelines started in 1080 feet of water and traversed through 1400-foot depths as the pipelines climbed up the continental slope to a fixed platform in 616 feet water depth. From there, the oil sales pipeline continued northward into slowly decreasing water depths to terminate with a subsea tie-in into an existing oil transportation system. These pipelines encountered a multiplicity of different situations: an undulating seafloor which created the potential for long pipeline spans, water depths to 1400 feet, rocky seafloor outcropping, pipeline crossings, subsea faults, laying lateral tap valves, deepwaterJ-tube riser pulls, and a subsea pipeline tie-in. The flexible pipeline system used relatively large 8 inch and 10 inch inside diameter flexible pipes in water depths to 1760 feet. A total length of about 12 miles of flexible pipe was installed. Catenary riser configurations were used by the flexible pipes at the Jolliet Tension Leg Well Platform (TLWP). These risers were installed throughpull tubes on the exterior of a column of the TLWP. The flexible pipe was laid around and, in some cases, over areas of rough local microtopography. The flexible pipes were connected to the steel pipelines and connected to an underwater connection skid using saturation divers working to depths of 1080 feet. GENERAL DESCRIPTION OF THE JOLLIET PROJECT The Jolliet Projectl accomplished a full-field development to extract oil and gas reserves from Green Canyon Block 184 in the Gulf of Mexico. The development consisted of a Tension Leg Well Platform (TLWP) in 1760 ft of water in Green Canyon Block 184 with 20 TLWP production wells, a Central Production Platform (CPP) in Green Canyon Block 52, a Drilling Platform (52A) which is part of Conoco?s Marquette Project and is bridge connected to the CPP, andintra-field and export pipelines.