LAPS Compression Feasibility Study

A gas producer intended to install an offshore compression system for the Lancelot Area Pipeline System (LAPS), with the aim of extending the life of the production assets. This would also provide the potential to attract third-party stakeholders into utilising the production system by offering a full range of operations.

Project Overview

As part of the rationalisation of Southern North Sea (SNS) infrastructure, an options review identified that offshore compression would be a viable proposition.

OSL carried out a feasibility study for installing an offshore compressor with a design throughput of 70 MMSCFD and the ability to deliver the gas at full National Transmission System pressure into Bacton terminal. As part of the study, OSL conducted an evaluation of the existing onshore and offshore LAPS facilities and identified feasible options for satisfying the commercial and technical aspects.

The most attractive solution was presented based on the best compromise between gas production rate, CAPEX, OPEX, operational availability and schedule.

Key Aspects of Delivery

• Process assessment
• Subsea routing and tie-in study
• Structural analysis
• Mechanical design
• Design of compression module and liaison with potential compressor suppliers
• RAM study
• Flow assurance to determine the flow regimes, pipeline liquid hold-ups and back out
• Provision of cost estimate and schedule.

Clever Thinking®

OSL demonstrated that by utilising a single caisson support structure and a single compression train, the total installed costs were estimated to be substantially less than those for a more traditional Self Installing Platform arrangement.

Also, a 3m diameter caisson driven into the seabed approximately 15 meters away from the existing platform would allow no clashes with subsea obstructions. Support of the caisson was provided by the existing jacket structure in the horizontal direction with the use of a brace truss frame connected into the main jacket legs. This resulted in minimal impact on the existing jacket structure.

Benefits to Client

• Increase in recoverable reserves due to the reduction in field pressures.
• Extension of the cessation of production date (CoP).
• Attractive to Third-Party field developments to feed into the LAPS network by offering a full range of arrival pressures.