May 31, 2018

 

Problem Statement

The normally unmanned Erskine platform has a max POB of just 12 people, which makes labour intensive well interventions a major undertaking.

There has been three years of unsuccessful attempts to remove scale and replace key down-hole equipment.

Needed to ensure that the 2017 campaign was a success.

Aims

  • A 55-day well services campaign on the Chevron-operated Erskine platform to be delivered safely, on time and on budget.
  • The campaign involved work on three wells, including the change-out of a wireline retrievable safety valve and two lower manual master valve stem seals and bonnets.

Method

  • New approach using tools trailed onshore, but new to the market and not used downhole before, including an expandable mill, allowing intervention crew to pass through narrow restriction at surface then out into the tubing where it was opened up.

    Completed downhole well-data logging, followed by the setting of plugs in the well-necessary barriers to allow the change-out of the lower manual master valve and the replacement of a Pascon valve, which is used to control pressure to the safety valve.

    Other work included replacement of storm choke valves, downhole safety valves controlled by pressure, and well-data logging.

Impact

The well services campaign is the culmination of years of work and involved
the dedication of the Erskine team, Chevron well services, Base Business
Operations Support and business partners Altus, Welltec, GE Vetco and
Halliburton.

The well services work required Erskine to be maned for 55 days, split into a
14 and 41-day campaign from April to June 2017. With limited facilities on
the platform and a max of 12 people on board, including 5 emergency
response team core crew, this only allowed for 7 other crew to carry out the
complicated and labour intensive work.

Specialised equipment meant deck space was limited to team work and
collaboration was key. Working with wireline companies chevron changed
how teams worked in order to carry out 24 hour working, saving over 20
days offshore occupation and production losses.

The work was carried out safely and successfully, eliminating three significant
well anomalies, allowing the wells to return to full integrity. Completing all
three work scopes incident free was a great achievement by the whole team.
The first work scope was challenging, with the alternatives for reinstating the
down hole safety valve would have resulted in either a costly coiled tubing
campaign or a completion workover, which would have cost missions of pounds
to restore the integrity of the well.

Total hours saved – 21.75 working days

Total savings anticipated – £4.7M