TLP tests new deepwater drilling technique
Vincent Roes
Shell
Scott Dickinson
Signa Engineering
James May
Smith Services
As reservoir depletion becomes commonplace in existing Gulf of Mexico fields, the oil and gas industry needs new tools and techniques to deal with the resulting challenges. Shell has identified managed pressure drilling (MPD) as one of the key technologies in support of efficient continued development of their deepwater GoM projects.
Shell selected its Mars TLP as the test bed for a new MPD technique called dynamic annular pressure control (DAPC). The operator deployed the system to solve lost circulation and hole instability problems, which brought a previous sidetrack attempt to an unsuccessful conclusion. It required a good bit of clever engineering to apply the technology in a TLP environment, with simultaneous drilling, production, and construction activities. Shell has successfully drilled the first planned MPD well using automated pressure control in the deepwater Gulf, using the first rotating control device ever installed on a TLP rig.
“The Mars project was ‘serial number one’ for planned MPD techniques in deepwater offshore applications,” Vincent Roes, Shell’s drilling superintendent for Mars and Ursa TLP rig operations, says. “We have challenges that need novel solutions, so we’re driving ahead to address them - these new solutions are a paradigm shift from how we have operated in the past.”
Practical considerations fostered the technology developments that made deepwater MPD possible. With five TLPs in up to 4,000 ft of water in the GoM, Shell and its subcontractors aim to build on the strong performance of the existing TLP assets.
Shell and its contractors had to plan for every scenario associated with MPD drilling on a TLP. Shell invested $300-$400,000 in this project before it sent equipment out to the Mars rig. With costs so high, Ross says, the key was to develop an automated pressure control system that could be trusted under difficult circumstances, to achieve difficult objectives cost effectively.
“This project is not only about improving ROP or saving time - it’s bigger than that. In our mature fields we are developing techniques to address the issues related to severe depletion, in some cases up to 7,000 psi. Novel approaches like MPD are promising developments, which will allow us to continue to drill through these depleted zones without experiencing the lost circulation problems that commonly occur under these circumstances,” Roes says.
Shell developed a technology deployment staircase to address the challenges of TLP redevelopment, and the operator identified MPD as a key component in the plan. Shell R&D developed the DAPC system used on the Mars platform and @balance LLC provided it. “We see it as a key component in developing our capability to efficiently sidetrack the existing TLP wells, through the depleted sands,” Roes says.
With 80-plus TLP wells available to sidetrack in the GoM, Shell’s MPD opportunities are significant. However, because MPD techniques are ideal for narrow pore pressure / fracture gradient situations, and potentially applicable to HPHT conditions, the range of potential opportunity is much larger.
The Mars TLP is in Mississippi Canyon block 807.
Adapting MPD systems to a TLP’s unique requirements required special attention to riser, BOP stack, and rotating control device design and layout. Constant rig movement, limited vertical space, and wellhead vertical movement made engineering the system tougher than usual.
“Isolating the blowout preventer and rotating control device from rig floor movement was critical to reduce stress on the tubulars,” Scott Dickinson, senior project engineer at Signa Engineering, says. “An entirely new design was created for use on the Mars TLP.”
To make the system work on the TLP, the team landed the drilling riser lower than usual, and devised a modified bell nipple overshot, bell nipple, and trip nipple. These components provided the vertical clearance necessary to fit a rotating control device (RCD) into the riser system 15 ft below the rig floor, between the BOPs and the bell nipple overshot. With its 100% remote operation, the Smith Services HOLD 2500 RCD was one of few rotating heads in the industry that the team could readily adapt to the Mars TLP operation.
“The HOLD 2500 RCD was designed with rig floor safety in mind; the goal was to keep personnel above the rig floor by making latching and unlatching the tool’s clamp an entirely remote operation,” James May, Smith Services’ senior engineering advisor, says. “Other systems will unlock the clamp remotely, but still require personnel on the BOP to manually operate secondary clamps or remove hoses. There’s simply no way to manually work with a clamp on a head made up into a riser system.”
Shell worked closely with Smith Services and Signa Engineering to develop the riser stack design around the RCD. “This really was the potential deal breaker,” Dickinson says. “Without a remote RCD, there was no way to load stripper elements through the riser stack. Smith Services put quite a bit of engineering muscle to the task to ensure that when the RCD and riser stack arrived at the rig on time, they would perform as required.”
Through long hours and several tweaks to the RCD and riser stack design, the system arrived at the Mars platform in late January. The team designed, fabricated, and fitted the stackup to the head in 16 days.
Upon start of the project, the RCD and riser stack performed as promised, stabilizing the BOP, containing the drilling fluid, and allowing stripper elements and the trip nipple to load through the rotary table. Shell successfully drilled the first MPD sidetrack on the Mars TLP platform in late March.
The rotating control device and custom riser stack on the Mars TLP rig allowed Shell to drill the Gulf of Mexico�s first managed pressure drilling sidetrack from a TLP.
Reservoir dynamics and simple economics point to MPD becoming a common practice in the GoM in the future. “As more deepwater projects are depleted, using RCDs to maximize production from existing wellbores will become much more common in the Gulf,” Dickinson predicts.
“Increasing riser stack design options while enhancing rig safety is what the HOLD 2500 RCD was built for, and the Mars TLP project is a good example of what can be accomplished with equipment developed to be flexible from the start,” May says.
The team believes that lessons learned from this project will play an important role in future reservoir exploitation.
“The time for MPD is right,” Roes says. “This is one of Shell’s most exciting projects in the Gulf of Mexico, and there’s a lot of excitement within the offshore teams. We’re really getting ‘out of the box’ and trying something different.”•
