Opening isolation valve without nitrogen
- Max. pressure 4,072 psi
- Max. deviation 85°
The completion design for an well offshore Trinidad was based on a gravel-pack technique commonly utilized for this type of well. It incorporated an isolation valve between the screens and the production packer to isolate the producing formation from later, up-hole operations such as pressure integrity testing.
Nitrogen was used to reduce the hydrostatic pressure in the tubing during pressure tests. However, in order to cycle the isolation valve with nitrogen, it had to be bled-off at least eight times, resulting in a nitrogen supply capacity considered too challenging to pursue.
In-country availability of large diameter coiled tubing and large capacity portable nitrogen tanks was very limited, causing unacceptable risk of delay to first production.
To actuate the isolation valve in an under-balanced situation, the operator chose to use a Well Stroker® with surface read out capabilities combined with a Well Key®. A successful System Integration Test (SIT) was completed where the Well Stroker opened the isolation valve using 6,000 lbf at 2,500 psig under-balance and another using 3,750 lbf at 1,150 psig under-balance.
Both mechanical actuations were done without damage to the valve. Offshore, the valve was successfully opened mechanically in the nitrogen environment and Welltec’s e-line solution is now the operator’s primary plan for these completion designs.
On the first attempt, the 4.56” isolation valve was successfully opened with a force of 2,000 lbf in a nitrogen environment with an under-balance of 1,000 psig.
The operation was achieved in a complex environment with a number of special safety, environmental and space constraints.
Two world’s firsts were accomplished in preparation for and during this operation: first, the process to open a 4.56” isolation valve in an 85° deviated wellbore while under-balanced 1,000 psig and second, the SIT with pressure below the isolation valve, simulating under-balanced conditions.
These achievements further the proven capabilities of Welltec® to deliver novel, value adding solutions.