English (United States)
Select a Language

    Asia Pacific

  1. English (AU)


  1. English (US)


  1. English (UK)
Case Study

Offshore compression concept selection

offshore compression project

Helping the client in its decision-making process to select between brownfield module and greenfield platform options for offshore compression upgrades.

The Situation 

Gas production was declining and compression was required to maintain export rates supplying strategic refining and LNG facilities LNG. Prolonged shutdown of offshore facilities was economically and politically problematic so robustness of execution was paramount within the decision making process.


Advisian provided engineering, consulting, construction and cost estimation services and assisted its client through the concept selection, pre-FEED and FEED transition phases of the project.

Concept Selection Phase

The objective was to select between brownfield module and greenfield platform options for offshore compression. A single project team (led from the UK) leveraged front-end expertise from the UK, regional expertise and construction expertise from Houston to perform high-level engineering, construction and cost estimation analysis. Key to the success of the six-week study was use of Quality Decision Management (QDM) to frame, narrow and select between the concepts. The project culminated in a joint Advisian-Client workshop selecting a greenfield solution, which was subsequently adopted by our client and recommended within its stage gate processes. Owing to the success of the concept selection phase and the use of QDM, the Pre-FEED phase was sole-sourced to the same Advisian project team.

Pre-FEED Phase

The Pre-FEED scope was segregated between brownfield and greenfield for schedule, construction and cost estimate reasons. There were two key goals:

  • Greenfield: Get our client to market (ITT) as quickly as possible; and 
  • Brownfield: Reduce schedule and construction risk by defining engineering and construction to “FEED level” and by integrating the project into our client’s area planning process to expedite critical-path offshore activities.

The QDM process was continued throughout Pre-FEED to progressively assess and close-out Tier 2 and 3 decisions. A decision-based schedule was developed to inform the Pre-FEED schedule and to ensure work was structured in the most efficient manner.


The scope comprised modifications at the hub facility to support a new bridge-linked compression platform. Advisian performed engineering, construction analysis, construction sequencing and cost estimation to a level commensurate with FEED. Critical to the project was close liaison with Client Area Planning to sequence the work scopes in line with planned asset Turnarounds (TARs) and to engineer modifications to minimize TAR scope.

The full brownfield scope included: 

  • Piping and vessel modifications to facilitate low pressure operation
  • Equipment relocation, replacement and reinstatement
  • Bridge landing structural strengthening
  • Assessment of bridge installation and installation guide
  • Pipe rack and cable installation
  • Systems integration
  • Construction sequencing and work pack generation
  • Engineering and Construction review workshops to align the project with the wider client organization
  • Multiple offshore visits to the offshore facilities

The project was successfully completed on budget, six weeks ahead of schedule and with significant quantities of work moved outside of a TAR.


  • A new compression platform bridge-linked to existing facilities.

To expedite the FEED ITT process, Advisian recommended our client engage the market using a functional specification, rather than a more typical scope of work. The functional specification was completed in less than five weeks and this advanced our client’s project schedule by 6 to 8 weeks.


Advisian successfully assisted its client through their stage gate processes and to FEED kick-off. The project schedule was significantly advanced by using a functional specification to engage the FEED and EPCI market. 

Meaningful amounts of brownfield engineering and construction analysis were conducted to reduce TAR scope, expedite critical-path offshore works and provide technical feasibility confidence to our client.