With special modifications, 20,000-ft SCR rig to tackle subsea wells located in up to 9,627 feet of water
When Shell Exploration and Production Co., as operator for the Perdido Regional Development Spar, decided to contract for a small-footprint, fit-for-purpose drilling rig in order to access 35 existing wells connected to the spar as well as to drill as many as nine additional wells from the spar itself, it chose Helmerich & Payne, Inc. (H&P), Tulsa, for the job.
With nearly four decades of platform drilling experience and more than two decades of experience working for Shell on a number of fixed and floating platforms both in the Gulf of Mexico and overseas, H&P assigned its Platform Rig 205 for the Perdido spar.
The self-erecting rig was modified for drilling, completions and well interventions specifically from a truss spar, and was mobilized to Perdido in summer, 2009. No stranger to drilling from both fixed and floating production facilities, H&P built Rig 205 in 2002. It was then used by Shell on its Cognac fixed and Ram Powell tension-leg platforms (TLP), both located in the deepwater Gulf.
Rig upgraded for spar topsides
According to Rig 205 superintendent Tom Freeny, the rig was upgraded due to the increased motion and acceleration forces affecting the Perdido spar, which is anchored in some 8,000 ft (2,383 m) of water. The rig’s drilling module is supported by a custom skid base that spans the spar’s 65-ft (19.8 m) capping beams and is designed to be assembled by the spar’s two pedestal cranes.
Rig 205 also has been upgraded in a number of other areas, Freeny said. These include draw works disc brakes, a 49-1⁄2-in. rotary table with PS-21 slips, a “Cyclone” Iron Roughneck, and a 16-3⁄4-in. x 5,000-psi BOP with setback dolly positioning, among others.
“Interfacing with Shell was required for installing and tying down several individual support packages,” he pointed out. These included a pipe rack module, with engines and the SCR house; a porch for the third mud pump, P-tanks, a diesel tank and four auxiliary mud tanks, among other attributes.
Helmerich & Payne’s offshore Rig 205 rests tightly atop the Perdido Spar.
Considerations for the design of a more robust hurricane tie-down system included anticipated spar accelerations due to high winds and sea states, said Freeny. For increased safety and environmental protection, the rig also features beefed-up systems for handling increased hook load and setback, as well as more user-friendly rig floor equipment to eliminate manual torque wrenches, hammers, etc.
The Perdido spar features the first application of wet tree, direct vertical access (DVA) wells from a spar-type floating production system. It is fitted with a single high-pressure drilling and completion riser suspended from the topsides for access to the 34 subsea trees, 22 of them located directly below the structure. This configuration will allow Rig 205 to use a surface blowout preventer (BOP) to drill, complete and later sidetrack those and subsequent individually drilled wells to 19,000 ft (5,795 m) or more.
Because the DVA configuration permits the rig to access a larger number of subsea completions, Shell anticipates the benefit of significant drilling and completions savings without loss of rig flexibility.
The rig also is equipped to install and intervene on the five electric submersible pumps contained in seafloor caissons that are used for the spar’s subsea separation and boosting system.
Close cooperation pays off
Freeny and his Rig Managers, Jimmy Welch and Tony Miller, were included in both preliminary planning and actual topsides design meetings by Shell, he said.
“It became necessary to add some unique features to the rig to meet Shell’s requirements,” said Freeny. “Without constant communications between both companies, working together as a cohesive team, there could have been delays. As it was, the rig was modified and ready for mobilization to the spar at the appointed time.”
Helmerich & Payne, Inc.
1437 South Boulder Ave., Tulsa, Oklahoma 74119
Tel: (918) 742-5531
Fax: (918) 742-0237