The final installment of Thisted-5

Composite intervention rig-up.

During 2017 WellPerform took part in the planning and execution of drilling the geothermal well Thisted-5. In October 2017, the well was completed and initially made into a production well to ensure sufficient cleanup.

During the summer of 2018 a well intervention was completed, and the well went into its final stage and was turned into an injection well. This was done by retrieving the production pump and installing a composite tie-back casing.

Thisted-5 was added to the geothermal plant in Thisted as a second injector, as the injection pressure had increased over the past in Thisted-3 and now started to become troublesome for the operational costs. Thisted-5 is therefore designed to be as cost efficient as possible, considering future operational costs:

  • The selection of the composite casing was made, not only to prevent corrosion, but in large because of the very low friction and thus lower pressure loss. Furthermore, the selected size of the tie-back casing was upscaled from initially being 7” to 10.6”, also to reduce pressure loss.
  • The reservoir section was drilled with special care to the formation, and a solid-free drilling fluid was used to avoid pore-blockages and formation damage.

Composite casing installed in the Thisted-5 well.

The installation of the composite casing is the first of its kind, for this type of application. The connections were glued together, and the connection and pipe body were custom-made as per the well-lifetime specifications. The process of gluing the joints together lasted for more than four days, as the glue had to build enough strength to carry the string-load prior to being run in the hole. A repair kit was kept at the site for emergency reparations of failed connections but never came in use as the string was run successfully with zero rejects.


The well will be brought into the geothermal circuit of the Thisted plant as an injector at the end of September 2018.

Should you have any questions or comments, you are more than welcome to contact Thomas Werge-Gross at