Efficient cement placement possible with Magneto-Rheological Blended Cement for effective well barriers - potentially saving £4million annually
NZTC has worked in partnership with WellSet P&A AS to develop a new barrier material, Magnetorheological Blended Cement (MRBC), with instantly controllable rheology in changing from a fluid state to a viscoelastic state.
This offers benefits in well plug and abandonment, intervention, and construction. Magnetic particles are blended into cement: the application of a magnetic field aligns particles to enhance cement displacement efficiency and immunity to gravitational migration, leading to more accurate cement placement and better cement integrity for water shut-off, as well as offering the potential to set shorter abandonment plugs. Traditionally, gravitational pulls cause cement to slump and move away from the location it was intended to act as a barrier.
MRBC is an innovative material that requires the transmission of an electromagnetic field downhole through carbon steel casing.
Improving the placement of cement in the annulus and preventing repeat cement jobs could save one day of rig time for each application.
A combined system enables low-cost access to existing subsea wells. A single package integrates well control barriers and fluid circulation/injection facilities, resulting in continuity, flexibility, reduced multi-operation interfaces and technical options when re-entering subsea wells.
Phase one of the project was established to prove the concept through a feasibility study and sought to examine:
- The optimal MRBC blend formulations for annulus barrier plugs.
- How electromagnetic (EM) field can be effectively transmitted through carbon steel casing.
- The electrical requirements for the electromagnetic fields.
- How to maximise MRBC displacement efficiency.
Phase one was completed successfully with the outcome that an EM field can be transmitted through a carbon steel casing to provide an annular barrier in a wellbore.
Phase two sought to:
- Use downhole technology to effectively transmit an EM field into a single annular space through carbon steel casing will be developed, tested on surface, and qualified for use in a pilot well.
- Assess the feasibility of the use of MRBC as a barrier medium in multiple annuli.
- Develop downhole technology to facilitate the deployment of MRBC barriers ‘thru-tubing’ ready for full scale testing on surface.
Physical testing proved that MRBC can introduce an instantaneous well barrier with no possibility to slump downhole or encounter common problems during curing such as gas or fluid migration. MRBC was shown to have equal or greater compressive strength compared with a standard cement slurry and furthermore provides a pressure retaining barrier while still in an unset state.
In phase two, MRBC was developed and tested in a realistic environment to show that it can form an instantaneous well barrier which is impervious to gravity and remains in place throughout the curing process. Computational simulations were first analysed to determine the key design criteria necessary to delivery an electromagnetic field strong enough to activate MRBC through an unperforated casing joint. Lab analysis was conducted to develop MRBC formulations which were then tested to prove that it would withstand a differential pressure.
Full rheology testing was completed, including fresh state and hardened state properties to analyse and compare against a standard oilfield cement slurry.
Lessons learned / Next steps:
With patent applications filed, WellSet intends to develop suitable blends of MRBC with associated placement techniques and downhole tools to facilitate the use of MRBC as an effective annular barrier medium both for water shut-off and well plug and abandonment (P&A) applications. Once commercialised, this material can act as an ‘enabler’ for rigless P&A operations, significantly reducing the cost of well P&A.
This study proved that MRBC is pumpable and has a compressive strength equal to or higher than a standard slurry.
This technology proves that a magnetic field can be generated in a casing x casing annulus to activate a MRBC slurry and form an instantaneous barrier which can be held in place throughout the curing cycle. Furthermore, by ensuring that no slumping or channelling can take place, MBRC technology enables accurate determination of the location of the barrier in the wellbore. The pressure testing results prove that a suitable length of activated MRBC can hold a full-length dual barrier above without failing. By allowing a physical base to be set within a casing x casing annulus above which a full-length barrier can be supported, the MBRC technology ensures no slumping or channelling can take place and delivers a higher quality annulus barrier than current state of the art methods.
- The concept of using MRBC as a well barrier material behind un-perforated carbon steel casing has been fully validated.
- Full-scale testing has proven that MRBC can function as a successful well barrier material, delivering an effective bond in an annular space between two casing strings.
- It has been shown that the power requirements required for downhole activation of MRBC can be met using industry standard wireline reels.
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