CONDUCTOR DRILLING SYSTEM ADDRESSES …claxtonengineering.com/wp-content/uploads/2016/01/...the mud...
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CONDUCTOR DRILLING SYSTEM ADDRESSES STABILITY, COST, AND HEALTH & SAFETY ISSUES IN THE NORTH SEA. When Hess Corporation approached Claxton Engineering for support with a conductor drilling system, it was exactly these challenges that it was hoping to overcome. Hess was scheduled to install a 40" conductor for Phase 3 of the South Arne development in the Danish sector of the North Sea. During previous drilling operations using 26" conductors, the company had encountered drill string vibration issues when drilling the top hole. Hess proposed an alternative conductor drilling system that effectively runs the conductor and the bottomhole assembly in tandem. Replacing the relatively light drill string with heavier conductor strings helps to reduce vibrations and prevent hole collapse. Hess asked Claxton to develop a suitable design for a very large system that could be delivered quickly. Claxton’s in-house project and design team put together a functional design specification for the conductor drilling system within days of the kick-off meeting, which Hess signed off with www.claxtonengineering.com Drilling top holes offshore in soft soil and relatively shallow water can present a multitude of challenges. Most notably, soft soil can render traditional drilling techniques ineffective, as the newly drilled holes collapse before casing can be installed. The soil conditions in combination with a lack of weight above the drill bit can also mean that there is little to dampen drilling vibration. These undampened vibrations can shake drilling equipment to the point where dropped objects occur with serious health and safety implications. Conductor Running and Installation Tool (foreground). Dual Bore Centralizer (background)
Transcript of CONDUCTOR DRILLING SYSTEM ADDRESSES …claxtonengineering.com/wp-content/uploads/2016/01/...the mud...
CONDUCTORDRILLING SYSTEMADDRESSES STABILITY,COST, AND HEALTH &SAFETY ISSUESIN THE NORTH SEA.
When Hess Corporation approachedClaxton Engineering for support with aconductor drilling system, it was exactlythese challenges that it was hoping toovercome.
Hess was scheduled to install a 40"conductor for Phase 3 of the South Arnedevelopment in the Danish sector of theNorth Sea. During previous drillingoperations using 26" conductors, thecompany had encountered drill stringvibration issues when drilling the top hole.Hess proposed an alternative conductor
drilling system that effectively runs theconductor and the bottomhole assemblyin tandem. Replacing the relatively lightdrill string with heavier conductor stringshelps to reduce vibrations and preventhole collapse. Hess asked Claxton todevelop a suitable design for a very largesystem that could be delivered quickly.
Claxton’s in-house project and designteam put together a functional designspecification for the conductor drillingsystem within days of the kick-offmeeting, which Hess signed off with
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Drilling top holes offshore in soft soiland relatively shallow water can presenta multitude of challenges. Most notably,soft soil can render traditional drillingtechniques ineffective, as the newlydrilled holes collapse before casing canbe installed. The soil conditions incombination with a lack of weight abovethe drill bit can also mean that there islittle to dampen drilling vibration. Theseundampened vibrations can shakedrilling equipment to the point wheredropped objects occur with serioushealth and safety implications.
Conductor Running and Installation Tool (foreground). Dual Bore Centralizer (background)
the mud pressure. A centralizer was alsoincorporated lower in the conductordrilling system to reduce deviation of thebottomhole assembly during drilling.
An upper and lower stem act asinterfaces between the hanger and thebottomhole assembly/coarse threadsafety joint, and a 75⁄8" regular lift toolprovides the interface with the upperstem for handling the conductor drillingsystem–bottomhole assembly.
The conductor drilling system also usesa casing running tool screwed directlyinto the top of the casing string thatforms a seal above the hanger. Mud isthen pumped through the casing runningtool and forced through the mud motor,thereby generating torque at the drill bit.
As the conductor drilling system bottomhole assembly penetrates the soil, anew joint of conductor is added to thetop by removing the casing running tooland torqueing in the new joint. Oncethe system is at total depth, the coarsethread safety joint is engaged theconnection between the landing ringand the hanger is sheared, and thebottom hole assembly retrieved.
minimal alterations. The design workthen ramped up and the whole systemdelivered in about three months.
“Claxton is not just an engineeringcompany that makes one or twoproducts,” explains Greg Brown, seniordesign engineer, Claxton Engineering.“We have expertise across many parts ofthe oil and gas industry and can providesolutions quickly. We are very responsiveand often work to very tight schedules.The conductor drilling system was basedon existing technology. The mainchallenge was its scale – we had neverbeen asked to apply the technology to a40" conductor. The sheer size was a testin itself; handling the system, getting itonto machines, even finding machineslarge enough to do the work.”
THE SYSTEM
The conductor drilling system comprisesa hanger and landing ring whichsupports the weight of the bottomholeassembly, transfers the mud pressureload to the conductor as well as resistingthe torsion generated by the mud motor,and providing an effective seal against
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Conductor Running and Installation Tool during loading
Dual Bore Centralizer during testing phase
TIME AND COST SAVINGS
By adding weight above the drill bit, thenew system reduced vibrations, enablingHess to successfully drill to depth (350 m)in one day without incident. Before usingthis system, drilling speeds had to belimited to minimise vibration and ensurethe wellbore was properly cleaned.
“Rig costs are very high, so every hourspent not penetrating is very costly,” explains Charles Youell, senior engineer,Claxton Engineering. “The system alsoenables Hess to combine two processesby running the casing while drilling. Aswell as saving time, the system instantlystabilises the top hole and mitigates therisk of it collapsing.”
FOLLOW-ON WORK
Following the successful delivery of theconductor drilling system, which includeddesign support during the trial andinstallation phases and supply of tertiaryequipment, Hess asked Claxton foradditional support. This includedproviding a dual-bore centralizer, J tool,swage, drilling and running tool interface,installation tool, false rotary table andbrushing tool.
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Stack Up testing at Weatherford'sTest Rig in Aberdeen
Upper section of the conductor drillingassembly during interface testing
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