After many years in services well structures may become unstable due to corrosion of the conductor, surface and production casings. Many of these areas are unseen and corrosion can go unnoticed. To prevent potential structural failures, which in many cases can lead to disastrous consequences, casings need to be strengthened and protected from further corrosion. Densit provides complete solutions for reinstatement of the well integrity using UHPC (Ultra High Performance Cementitious) material.

Densit UHPC material provides structural integrity of the well conductor and casings, together with effective protection against corrosion. These benefits are usually achieved without any adverse effects on production rates.

The relatively small size of Densit’s inspection, cleaning, mixing, pumping and materials handling equipment, means that all work can be carried out from either workboat, barge or platform.

As part of Densit’s comprehensive well integrity services, the well clamps and cement top on the well are removed and the annulus cleaned using high pressure water jetting to remove any flaking rust, debris, marine mud and surface contamination, then flushed with water.

The well annulus is then visually inspected using a down hole camera. Condition, size and depth of the annulus between the conductor and surface casing, as well as the annulus between the surface casing and production casing are evaluated.

Hose sizes and an estimate of the quantity of Densit UHPC material to be used and prepared for injection into each annulus is determined. Any small holes in the casings can be easily accommodated due to the unique self sealing characteristics of Densit UHPC material.

Once inspection and cleaning is complete, the hose is inserted into the bottom of the annulus and Densit UHPC material is injected the hose is retracted as the level inside the annulus rises.

The progress of the Densit UHPC material in the annulus is closely monitored by the down hole camera until it reaches the surface and then the operation is complete. Although Densit UHPC material is continuously mixed and pumped, the small batch sizes allow for maximum flexibility during operations, such as shallow wells and the minimisation of waste. Typically, most wells can be completed within one working shift.

Due to the very high early strength development of Densit UHPC materials, wells can be returned to full service within 24 hours of completion of grouting.

Densit UHPC materials are characterised by their extreme strengths and durability whilst at the same time being pumpable up to several hundreds meters in 2 to 4 inch flexible hoses allowing for a swift and easy installation offshore.

Due to the highly viscous behaviour of the mixed materials, there is no risk of washing out of cement particles or grout dilution when cast subsea, or in a water filled member or annulus. The Densit UHPC material will displace any water due to its extremely viscous nature and the very high material density.

Densit UHPC material is more than just a filling material. The ultra high strength and durability, combined with no shrinkage after injection, keeps the Densit UHPC material in contact with the steel surface.o

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John Gronbech is General Manager, Densit Asia Pacific Sdn Bhd, Sabah, Malaysia. www.densit.com