RePlug®: a novel cement material for petroleum wells

The last 100+ years have provided essential developments in cementing, innovations that have made petroleum drilling- and well operations safer. However, micro-cracks, micro-annuli and poor bond-logs are still a concern, and harsh chemicals accentuate these problems. Once these pathways for fluids are open, they stay open or widen to cause leaks unless we engage major costly repairs.

Our cement ingredient RePlug® is based on environmentally safe mineral products. RePlug® works by reacting minerals with fresh-, salty water, and/or CO2 to metamorphose minerals into pores and cracks that would otherwise be pathways for leaks from petroleum reservoirs. RePlug® is a “green” product on the Norwegian HOCNF list and is very safe in use, both for personnel and the environment. The addition of these mineralogical materials into ordinary cement blends cause the matrix to self-heal when any water is present in the set cement. Self-healing works with water only. It is accelerated if the cement is exposed to harsh chemicals like CO2 into the formation water. The self-healing mechanism also benefits from increasing temperatures in the well. The blends created with RePlug® have been found to be more than 100 times more impermeable than the minimum requirements on the Norwegian Continental Shelf. The cost saving potential is significant as it is easy to blend and mix using conventional equipment, making it suitable for large-scale deployment by use of ordinary cementing infrastructures/equipment, operations, and procedures as well as techniques.

Well Barrier Acceptance Criteria (WBAC), as applied by regulators world-wide, are better met by RePlug®.

RePlug® has been tested to full scale in active petroleum wells, both behind casing and in-hole as a part of permanent plugging for abandonment of wells. The product has the potential to ease the worry of immediate and future damage in well operations that are performed in CCS-wells or adjoining wells crossing the same reservoirs. In addition, it will be useful in areas with known sour wells, vibrations, earthquakes, and for just knowing that the future integrity of the well is improved from current technology. RePlug® aids modern well planning that require new wells to have a P&A focus during construction phase as the new blends with lower CO2-footprints are beneficial for well integrity over the lifespan of wells. Reducing the risk of having to perform any operation more than once saves potential future CO2 emissions and -costs from unnecessary rig work.

Permanent well barriers should “provide long term integrity with an eternal perspective”. By applying RePlug®, self-healing occurs as the material sets, and will continue until the reactive material is completely depleted, which may take thousands of years.

RePlug® can also be used for applications in the concrete industry

ReStone collaborates with SINTEF, Heriot Watt University and University of Maryland to develop and test our products. We are also collaborating with major international oilfield service companies, as well as the Norwegian Research Council and Innovation Norway.

CT scans of small cores (2,5*4 cm) of RePlug blends before (a) and after (b) 4 weeks of ageing in seawater and supercritical CO2 at elevated pressures and temperatures. Red dots are pore spaces in the blend, and the (b) scan shows how the outer mantle of the core is sealed off, protecting the inner cement, and new minerals are formed on the surface of the core, sealing off potential micro annuli.