Large Onshore Gas Plant Reconfiguration Project

A large 2-year Completions and Commissioning service to support the reconfiguration of an onshore gas plant to receive gas from a new offshore platform and process for transfer to the UK’s Gas Network.

Large Onshore Gas Plant Reconfiguration Project image


The client’s facility is based on the East Yorkshire coast and services a partially depleted offshore gas field that was converted for storage and serviced one other offshore gas field that had ceased production. A new offshore development required a new 48km 20inch gas export, and 3inch methanol injection pipelines which to be connect to the existing processing facilities.

This required the connection of this pipeline to new reception facilities (pig catcher and ESDV), new pipe racks that enabled the connection to the existing Train A slug catcher. The existing storage field reception facilities were then reconfigured to connect to the then dormant field gas slug catcher.

The project required an upgrade of the storage field compressor from a 2-barrel 2 stage configuration to single barrel 2 stage configuration with new lube oil and aftercooler packages. The project also saw the overhaul of the terminal’s methanol recovery and LP flash gas systems required to achieve emissions targets and reduce the amount of offsite methanol/water treatment.

The principal contractor executed the project from Engineering through to Mechanical Completion. The client’s project team required support of a Commissioning Specialist company to:

  • Execute oversight on handover from the principal contractor.
  • Plan and execute pre-commissioning and dynamic commissioning.
  • Support handover to Client operations for start-up and ongoing production.

The Challenge

Provision of a completions and commissioning support service to cover a rapidly changing multi-phase delivery, including Commissioning Test Procedure writing, completions delivery, FAT support, pre-commissioning, and dynamic commissioning execution.

The pressure on the client to have the facility ready in time for first gas from the new offshore field development operator was significant.

Poor Engineering design from the principal contractor who was removed from the project before finalization of the design.

COVID 19 hit the UK with forced blended working from home and working at site under tight restrictions.

The engineering and COVID challenges resulted in significant changing of priorities (including phasing and sequencing) resulting in significant MoC activity without any drop in expectations on cost efficiency, productive delivery, and agile problem solving from OCCMS.

The Solution

Completions and Commissioning services to support the client’s new project objectives over 3 execution phases and a total of 11 sub-scopes as follows:

Handover and familiarisation

  • Planning & Preparation
  • Commissioning Execution – Phase 1 (Part 1) – Storage Field Export
  • Commissioning Execution – Phase 1 (Part 2) – Storage Field Export

Planning & Preparation – Phase 2 – New Field Connection Free Flow

Planning & Preparation – Phase 3 – LP Compression

Commissioning Execution - Phase 2 – New Field Connection Free Flow Start-up

  • Commissioning Execution – Phase 3 – Methanol Recovery

Commissioning Execution – Phase 3 (Part 1) – LP Flash Gas

Commissioning Execution – Phase 3 (Part 2) – LP Export Compressor

Handover to operations, Start-up support & Project close out.

The above structure was worked with the client to de-risk delivery due to the challenges as given in the previous section and to align with associated delays in the New Field Development Free Flow start-up target date.

By working with the Process Group, the LP flash gas and export compression scopes were able to be moved off the critical path in the schedule. This enabled the team to utilize the new float produced by this change with more cost efficiency despite the challenges from the Engineering delivery. This also allowed the team to work with greater flexibility and agility in managing the uncertainties and potential self-isolation of key resources during key delivery periods.

OCCMS’s Professional Contract Model (PCM) approach provided the ability to adapt at pace to the changes in delivery phases and the knock-on scope and sub-scope changes all under appropriate MoC processes and controls. This approach also ensured OCCMS could also adapt at pace to emerging scope also derived from the known challenges and worked mitigations. This included:

  1. E&I punch kill and red-line MU team.
  2. Management and technical oversight of the pipeline hydrotesting.
  3. Interface management with the New Field development offshore facility operator for integrated dynamic commissioning of the telecoms system coving both onshore and offshore.

The Outcome

At the time of writing of this case study the project had just completed phase 2 planning and preparation and had commenced execution of the critical phase 2 Completions, Commissioning and Start-Up support scope.

Delivery of a successful plan and prep phase resulted in the team being ready on time and within budget for execution. This was demonstrated through the delivery of the following key activities and associated deliverables:

Key Phase 2 P&P Activities

  • Re-alignment of logic with new phases
  • Re-alignment of schedule with new phases
  • Re-alignment of resource plan to new phases
  • Orbit™ fully populated and validated for use
  • Interface management (P&P only) o/s telecoms
  • Oversight of Pipeline Hydrotest Contractor
  • Using remaining schedule float and budget to set-out requirements for phase 3 in advance.
  • MC Handovers from Construction, E&I punch kill & Red-Line MU team mobilized, management of preservation and set-up of Temporaries.

Associated Deliverables

  • Phase 2 Commissioning Logic Diagram
  • Phase 2 Activity Plan
  • Phase 2 Commissioning Resources Plan
  • Phase 2 and 3 Completions Work Packages
  • Pipeline Hydrotest Completion Report
  • Phase 3 Commissioning Logic
  • Phase 3 Budget Estimate
  • Ready for Phase 2 Commissioning Certificate(s)

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