Halliburton’s Ernst Schnell discusses a recent collaboration between Halliburton’s casing equipment team and a Scandinavian operator, which helped develop a rigless method for plugging a well through the Xmas tree.
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Rigless AbandaSystem schematic. Image from Halliburton. |
Time is money. In offshore operations time is a lot of money. Looking for ways to operate more efficiently and lower costs is essential to ensuring the viability of offshore operations, especially when market conditions are as challenging as they’ve been over the past two years.
Halliburton and a Scandinavian operator recently collaborated to develop a new rigless, time-saving method for setting controlled-volume abandonment plugs. Unlike a conventional plugging operation that requires extra personnel and complex logistics, the rigless AbandaSystem entails a AbandaSpool cement spool, connecting to the Xmas tree, a wireline-deployed packer to serve as a base, and two AbandaPlug wiper plugs to land on the packer and isolate the cement to prevent contamination.
The AbandaSpool cement spool is a plug container body equipped with three plug-release plungers and a manifold with six plug valves.
Atop the retrievable packer is a seal-bore landing profile adapted for a specialized lower wiper plug. An optional water injection valve can be added to the bottom of the packer to act as a check-valve to prevent flowback from the well; this valve can also be configured for specific pressure overbalance to ensure that the cement and not the valve is holding the pressure.
The lower AbandaPlug wiper plug is rubber and has a seal mandrel on bottom to land on the packer’s seal-bore, creating a seal and acting as a base for the following cement slurry. This wiper plug includes a shear disc designed to burst at 1000–4000psi, depending on well requirements; this allows testing the seal of the cement plug after it’s cured. If the plug does not hold above the required pressure, the shear disc will burst and open a path for pressure to bleed off below, indicating failure.
The upper AbandaPlug wiper plug is a conventional plug to separate the cement from the displacement fluid.
Candidate wells for this method should have confirmation of a reliable cement barrier in the annulus, acceptable injection rates and pressures by running an injection test, and that a packer can be run and set in the tubing by running a caliper log in the tubing.
The packer is run on a wireline connected to the AbandaSpool cement spool — this speeds up the operation and reduces rig downtime. The wiper plugs are installed and released from the AbandaSpool cement spool. Pumping and displacement of cement follows a conventional casing cement operation. When landing the lower wiper plug, which seals in the top of the packer, the crew must focus on limiting pumping pressure to avoid exceeding the shear disc threshold.
After waiting on cement to achieve sufficient compressive strength, a cement pressure test is performed at the required pressure, exceeding the shear disc threshold to ensure a reliable confirmation of the cement plug.
The rigless AbandaSystem method can be applied to a range of casing and tubing sizes. The packer used in the operations thus far is available for tubing ranging 4.5-7in.
Placing the cement plug without using the retrievable packer is another option. The lower wiper plug can be modified with an elastomer seal bottom sub to land in any geometry.
The four operations performed to date have saved the operator 1-2 days of rig time per plug. The current regulations in the North Sea require a cement barrier plug to be tagged with drillpipe; where this is not a requirement more time can be saved.
The next challenge Halliburton and the operator are working on is adapting this novel method for subsea wells, as the potential cost savings will be even greater compared to platform wells.
Ernst Schnell is the cementing technology & business development manager for Eurasia, Europe and Sub-Saharan Africa at Halliburton. He was trained as a chemical engineer at the Karlsruhe Institute of Technology in Germany and has his Master of Laws in Oil & Gas Law from the Robert Gordon University. His career has been internationally focused, taking him from Nigeria, to the UK, the Netherlands and Angola. Ernst joined Halliburton in 2012.
M. Olsen et al.: “Improved Through-Christmas-Tree P&A Plug Placement with New Innovative Cementing Methodology”, SPE Paper No. SPE/IADC-184653-MS, SPE/IADS Drilling Conference and Exhibition, The Hague, The Netherlands, 14-16 March 2017.
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