Brutus Export Pipelines - Improvement Opportunities and Challenges in Deepwater Pipeline Installation

Abstract

Abstract This paper details the design effort and reports on the opportunities for significant improvements that were undertaken to minimize the cost and schedule of the Brutus pipeline installation and commissioning efforts. Export pipeline installation and commissioning often fall on the critical path for floating host installations. Given the existing economic conditions at the time of Brutus first oil, and the rate at which the initial wells were to be produced, accelerating first oil became a significant driver for the project. This paper will describe the methods and techniques utilized to ensure that the export pipelines did not drive the first oil date. Additionally, throughout design and execution of the project, the team was confronted with several challenges. These challenges were often self-imposed while attempting to provide innovative, cost effective solutions that would show continuous process improvements over Shell's previously benchmarked deepwater projects. Throughout this paper, significant technical challenges that were overcome in theprocess delivering overall cost and schedule improvements will be highlighted.a Furthermore, this paper would not be complete without mentioning the unexpected challenges that arose throughout the project cycle. In particular, the challenges that were faced when the project was confronted with the identification of a transit fatigue crack in a pipe joint during offshore installation are discussed. The efforts that were required to combat the fatigue crack concerns, notably the identification, on-shore testing, and final offshore pressure testing that was required to prove up the pipe that was potentially affected are also discussed. Introduction The Brutus Tension Leg Platform (TLP) is located in 2980 FSW in Green Canyon Block 158. Two export pipelines, a 20/18-inch dual diameter crude oil line and a 20/18-inch dual diameter natural gas line, transport the processed hydrocarbons to existing shallow water platforms. These pipelines connect to existing infrastructure at shallow water platforms. The 25.5 mile long crude oil line transports oil from the Brutus TLP in GC 158 to Shell Offshore's South Timbalier 301 "B" platform, in 335 fsw, where the line ties into the existing Amberjack system. The 23.9 mile natural gas pipeline transports sales quality gas from Brutus to Shell Gas's Ship Shoal 332 platform, in 435 fsw, where it connects to the Manta Ray Gas Gathering System and to the Transcontinental Gas Pipeline system. Both the oil pipeline and the gas pipeline have a maximum allowable operating pressure (MAOP) of 2220 psig. Location, Routing and Bathymetry Figure 1 depicts the routing of the lines from the Brutus TLP to the shallow water platforms. The Brutus TLP was designed as a deepwater hub, allowing for multiple future subsea tie-backs. The potential future locations of the subsea developments were considered while routing the export pipelines from the TLP. The oil and gas lines are routed in a north northwesterly direction while departing the TLP to provide access for a potential subsea development to the north of the TLP. Additional catenary riser baskets have been strategically placed along the hull pontoon for use in tie-ing back the future subsea prospects.