Case Studie
June 19, 2018

Case Study: Modular efficiency

ExxonMobil were seeking a cost-effective solution to conduct plug and abandonment (P&A) activities on 22 wells on the Jotun B platform.

The challenge

The scope of work set out for the project specified:

  • The unit had to be lightweight and have as small a footprint as practicable
  • The unit required to be installed onto existing derrick footings
  • Have low POB requirements
  • Capable of workover and drilling operations
  • Comply with temporary equipment standards and be fit for use in the Norweigan Continental Shelf
  • Mast self-erecting in part due to crane height limits

The solution

Petro Well Services AS (PWS) tendered with Halliburton recommending the provision of a modular unit solution for P&A operations. Off ering a concept design for a new breed of modular unit (Optimus), the proposal was accepted, developed and implemented over 14 months, providing:

  • A unit capable of drilling, P&A and workover operations with a hoisting system of 350Te pull
  • Low power consumption capable of running unit independently with portable power generation and minimal power integration to platform services
  • Easy interface with rig F&G, PA, platform general essential power and UPS supply requirements
  • Installed utilising specially designed interface beams between the Optimus and Jotun B.
  • Unit designed for full integration with existing or standalone mud system and pressure control unit
  • Extensively automated unit reducing exposure to injury
  • Low footprint and standalone modular unit capable of installation in 12T lifts
  • Compliance with latest relevant standards – incl. NORSOK Z015, DNVGL-OS-E101 and other applicable NORSOK standards
  • Low POB operations with multi-skilled team (5 dayshift and 5 nightshift with a further 2 at build stage)
  • Quick mobilisation, installation and interface integration to the platform
Interface beams of the Optimus rig


PWS successfully delivered and now operate a low cost, low POB, standalone P&A, drilling and workover unit, that can be promptly deployed, commissioned and integrated with an off shore platform. All targets set out by ExxonMobil were fulfi lled on time. All phases from design through to build, installation and commissioning were completed with no incident.

Current performance demonstrates tripping upto 30 super singles per hour with no LTI’s or reportable incidents throughout the build, commissioning and operations phases off shore and well ahead of planned schedule.

Self erecting hinged mast

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