PTC Big Bore VR Lubricator Tool, Vetco, North Sea
Petroleum Technology Company successfully removed stuck valves from the VR profiles using high torque with the new VR Big Bore Lubricator. The BB Lubricator was developed to avoid a time consuming and costly intervention. The estimated savings are over £1 million.
A North Sea operating company had five wells with seized 4" Injection Non Return Valves (INRV) within the VR profile with 4" 10 UNS Thread The valves installed were no longer reliably holding pressure and had to be replaced with new surface annulus safety valves.
The standard PTC VR Lubricator has torque capability of 1500Nm (1106 lbf.ft). The challenge for PTC was to design a VR Lubricator with enhanced torque capabilities to break out the seized INRV’s.
PTC Big Bore VR Lubricator (BB lubricator) was developed with the capability of torqueing up to 3750Nm (2765 lbf.ft). The BB Lubricator has a stroke length of 962mm, whilst only requiring operating length of 723mm. Low torque can be applied from the back of the lubricator using a standard ratchet wrench. For torqueing above 1000Nm (737 ftl.lb) a hydraulic torque wrench is required to rotate the main body.
The BB Lubricator package was deployed with the plan to remove five INRVs over two weeks of operations (12-hour shifts). A single PTC field service engineer was able to safely operate the tool in the confined well bay. Once permits were in place the average operation time for the removal of each INRV’s was half a shift (6 hours). The break out torque values were 3270 Nm – 3633Nm.
The valves removed showed no sign of thread sealant, corrosion, or damage.
The alternative to the PTC intervention involved; setting a deep set plug, bleeding down the all tubing and annulus pressure before milling the seized INRV’s. The HSE, logistics and risks involved in the milling operation are far greater, than the case was with the used solution. The BB Lubricator based solution was efficient and cost effective, completing the work in 4 shifts at a total cost of approximately £100k. The cost of the milling operation would have been significantly higher.
Figure 1| shows the Torque Adapter, locked onto the Lubricator body; it provides a cradle and back-up function for the Torque Wrench.
Figure 2| shows the BB Lubricator during the site integration test at the PTC UK yard before initial deployment. The stack up length from the Gate Valve face to the back of the Lubricator was 1048.2mm (41.27"). For the deployment, the use of the spacer spool was required due to the length of the INRVs. Once the tool was fully retracted, the INRV would be housed within the spacer allowing for the gate valve to be shut.
Figure 3| shows BB Lubricator during rig up without the Torque Adapter installed. The tool can be operated without the Torque Adapter/Wrench up to 1000Nm (737 ftl.lb). For example if the tool was being used to set a plug or valve the Torque Adapter/Wrench would not be needed.
Figure 4| shows the BB Lubricator installed within a confined environment where standard lubricators would struggle to operate. Compact design of the BB Lubricator tool, Torque Adapter and Torque Wrench allows conducting operations even in crowded environments.