ConocoPhillips Bespoke Tension Deck for Judy P-20 ConocoPhillips were in the planning phase of drilling three additional wells on the Judy platform - P20 being the first well. The Judy Platform was initially built to accept skid off drilling packages from the then, latest drilling rigs, however improvements in jack up technology meant the Maersk Inspirer with the extended reach cantilever could access all wells conventionally on the Judy Platform. Well P20 was in excess of 100 ft/30meters from the Inspirer s hull/barge therefore the rig s hook load was reduced significantly if used in conjunction with the inspirers own riser tension system. It was at this stage that ConocoPhillips instructed Claxton to design/analyse/fabricate/ Install & commission the P20 Riser Tension System on a fast track basis. The Tension system would enable ConocoPhillips to tension the conductor and additionally support the weight of the BOP and well control equipment thus reducing any potential buckling loads. Original plans were for a 300 tonne Safe working Load, however once project procurement/fabrication had commenced - a required Safe Working Load of 400 tonnes was requested. The system was capable of applying 400 tonnes load however the structure s final certified load capability was 380 tonnes. The Claxton-designed tension cartridge. Shown with transportation frame, also supplied by Claxton. ConocoPhillips design brief required a compact modular package - whereby the installation phase would not allow for the potential to work under loads or around open deck hatches.
Design Features Modular design enabling three main lifts for ease of installation- without the need to work under suspended loads. System installation allowed for the deck hatch cover to be removed whilst always maintaining a substantial barrier around the opening. The system includes a work-deck allowing ease of riser connection make-up. Tension deck allowed full drift capability for large diameter riser connections & wellheads to pass through. Modular design enabling three main lifts for ease of installation- without the need to work under suspended loads. System installation allowed for the deck hatch cover to be removed whilst always maintaining a substantial barrier around the opening. The system includes a work-deck allowing ease of riser connection make-up. Tension deck allowed full drift capability for large diameter riser connections & wellheads to pass through. Complete supply: Claxton also designed and supplied a self-contained HPU, able to be positioned within a 50ft radius of the tensioning deck. Design Verification Verification of the system prior to mobilisation was paramount. Verification was through load testing of the 4 off Cylinders (pressure tested and pull tested to 150 tonnes each e.g. 1.5 times swl see (fig A) Load testing of the Tension deck to 475 Tonnes. The Cylinders were also function tested (fig B) Full NDT of all load bearing areas.
Installation Phase 1 2 First Load Spreader beam positioned on platform skid beams (shown in red). Second Load Spreader beam positioned on platform skid beams central to deck hatch. 3 4 4 off Support Spools installed Tension cartridge is lowered and installed in one platform crane lift. Total Installation time: 12 hours
Operational Phase A crew of 4 Claxton Service technicians was used for complete tension system installation and riser make up. User friendly controls enabled the rig s drilling crew to monitor and adjust the system after HP riser installation. Claxton personnel were utilised to de-mobilize the system from the P20 well. Demobilization was optimised achieved by ensuring the tension cartridge transportation frame was ready on deck with all certification in place. A view across the system showing the riser connector and spreader beam support spools. All cylinders fully retracted in readiness to lift tension cartridge. The design allowed either the rig s blocks or platform crane to pick up cartridge and lower into the transportation frame and secure for backload. After the cartridge was removed the rig s deck hatch was replaced. Once the spreader beam support spools were removed the skid load spread beams were moved to a position accessible to platform crane in readiness for backload. A full view of the installed system and riser.
The Bespoke Tension Deck performed as expected in the field and enabled the Judy wells to be drilled conventionally. Claxton has subsequently provided bespoke tension systems for a number of major rig owners and operators. Dannie Claxton, Technical Director The Maersk Inspirer - the rig s extended skid out capability (pictured) meant all the wells on Judy could be reached via conventional jack up drilling.