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Flexible Coupling

Flexible Coupling

Within ÍSOR, Iceland GeoSurvey, a novel patented technology of Flexible Couplings for casings in geothermal wells has been in development since the year 2015. Its goal is to mitigate casing failures in production casings of geothermal wells, thereby increasing reliability of the downhole structure.

By allowing displacements of each casing joint in the production casing, the risk of casing failures as a result of constrained thermal expansion is minimized by limiting thermal straining of the casing material.

Research and development of Flexible Couplings:

  • Design, prototyping (9 5/8”) and testing at ambient temperatures within the EU H2020 supported project GeoWell (2016-2019).
  • Prototype design for larger diameter casings (13 3/8”), build and testing, as well as field testing in a geothermal well in Iceland within the EU H2020 supported project DEEPEGS (2015-2019).
  • Market analysis, risk analysis and testing in relevant environment in a surface experiment demonstration by connecting to a HT geothermal well in Iceland within the GEOTHERMICA supported project GeConnect (2018-2021).
  • Casing technology for increased well integrity for superhot wells in the EU Horizon Europe project COMPASS (2022-2025).

Downhole logging data from Icelandic high-temperature geothermal wells shows that casing failures have been found in approximately 1 in 4 wells.

  • Around 1 in 10 wells have shown casing tensile failure.
  • Constrained thermal expansion of cemented casings results in damaged casing material and can lead to severe casing failures.
  • Increased structural integrity is assured by allowing movement of each casing joint instead of generating excessive forces.
  • Leads to more secure downhole structure and increases likelihood of successful project saving millions in investment cost and future revenues.
  • The patented Flexible Coupling is a solution that improves well integrity by allowing expansion of the casing.
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Related projects

COMPASS: casing & cementing of deep wells
Completed2022

COMPASS: casing & cementing of deep wells

ON Power

The project concerns the preparation for deep drilling and aims at solutions so that casings can withstand the strain that arises when high-temperature wells heat up. This is to be done, among other things, by examining cementing with "foam cement", a light and flexible cement that reduces the load on the casing. A method will be developed for releasing the pressure that builds up between casings (ÍSOR), corrosion protection by cladding will be specially examined, and corrosion tests will be carried out at the surface and down the well with a logging wire (ÍSOR). An integrated casing system designed to withstand supercritical conditions (including the use of expansion joints) will be tested in experiments at SINTEF in Norway, which also handles the simulation of boreholes.

RESULT: enhancing reservoirs in urban areas
Completed2020

RESULT: enhancing reservoirs in urban areas

TNO

For green cities (mission Horizon Europe), geothermal energy is expected to be used widely in urban areas for heating instead of fossil fuels. Geothermal utilisation in urban areas can be complex, even though the geothermal systems are relatively well known. The main aim is to demonstrate the possibility of a 30–100% increase in the main geothermal use for heating in urban areas in the northern part of the EU. RESULT achieves this by applying 1) optimisation methods and drill-and-learn approaches, 2) model calculations and uncertainty assessment, 3) using the best technology, 4) optimising methods for different conditions in Europe. The innovations will be 5) used in the design and drilling of doublet wells in the Netherlands.