Subsea Tree Accumulation Circuit Replacement
Project
Subsea Tree Accumulation Circuit Replacement
Location
Gulf Of Mexico
Water Depth
2,100m
Project Type
IRM
Project at a glance
A tree manufacturer experienced slower than expected closure times of their tree valves when a well was flowed at maximum capacity. Based on prior experiences this issue was attributed to a failure in the existing compensation and transfer barrier accumulators. In order to prevent a need to retrieve the tree it was requested that the entire circuit, including compensators, be replaced subsea.
Challenge
The accumulator circuit replacement consisted of:
- Design and fabrication of project specific tooling, including a skid containing replacement transfer barrier and compensation accumulators with a 20 year design life
- Cutting of existing super duplex hydraulic tubing
- Installation of overshot tools onto existing hydraulic tubing
- Tie in of new accumulator skid to overshot assembly
- Flush and pressure test system followed by function testing of the tree
Highlights
Subsea 7 provided the customer with an initial solution within eight weeks. This included the design, build and testing of project specific tooling to fit within very tight space constraints without interfering with nearby hydraulic circuitry.
Value to the Client
By replacing the hydraulic circuitry subsea, the cost of hiring a drillship to pull a well completion and tree was avoided. In addition to the lost revenue of production downtime.
Technology and Innovation
Each piece of equipment used in this project was new including:
- ROV operable tubing saw - designed to provide a quick clean cut without damaging nearby tubing which was as close as 1.5 inches away
- Tubing end preparation tool – designed to clean any burs left on the cut section of pipe
- Tubing overshot tool – designed to connect and seal to cut sections of ½ super-duplex tubing without failure up to 7,500 psi
