Projects - BP Magnus RTU Upgrade

Tierney Strachan upgrades BP Magnus RTU equipment as part of the Magnus EOR Project

Magnus is the UK’s most northerly oilfield. Discovered in 1974 it lies 160km north-east of the Shetlands and came on stream in 1984. Magnus produced oil is transported through a 24in crude oil pipeline to the Ninian Central platform while gas is piped ashore using a joint pipeline linked to the Shell/Esso Far North Liquid and Associated Gas System (FLAGS), which runs to St. Fergus. The enhanced oil recovery (EOR) project involves the importation of gas from the West of Shetland developments Foinaven and Schiehallion and reinjection of the gas into the Magnus reservoir. The aim is to increase Magnus reserves and extend the field life to beyond 2015. The project also addresses environmental issues by significantly reducing flaring between the fields.

BP Magnus Platform

Magnus gas export pressure; temperature; flow and valve data was previously gathered by a Ferranti Mark 2A Remote Telemetry Unit (RTU) (see picture below) and passed through telecommunication equipment to Shell’s Real Time Management System (RTMS). This in turn provides data to the Aberdeen Operations Control Centre (AOCC) for monitoring of the FLAGS pipeline network.

The EOR project required a significant number of new data signals to the RTU equipment, and owing to the age and availability of parts for this system; the decision was taken to replace the RTU equipment with a more modern PLC based solution. To minimise offshore installation time, only the RTU electronics sub-racks (shown left) were replaced whilst retaining all existing field cable terminations. Maximum re-use of existing infrastructure allowed offshore installation and commissioning to be fully completed within 6 days.

Previous Ferranti Mark 2A RTU

The replacement system uses an Allen-Bradley SLC500 PLC with a Modbus serial connection to RTMS and a second Modbus serial link to the SGC metering database to obtain gas composition data. A number of hardwired digital and analogue signals are also interfaced by the PLC where 8 decade totalisers are provided. The PLC type selected offered a number of advantages over alternative equipment in that the PLC components are readily available with good future availability due to a large user base and has an extremely good support and proven reliability record. Tierney Strachan worked closely with AdRem Consulting, Wood Group; Stephen Gillespie Consulting (SGC) and Scomagg to prepare accurate detailed design information and provide a low risk; minimal installation time upgrade for the NLGP RTU installed on the Magnus platform.