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Work Package 3

Leader: TNO

Other partners involved: ISOR, Acquit, BRGM, HS ORKA, IRIS, Statoil

Objectives

Develop cement and sealing technologies optimized for high-enthalpy geothermal applications in order to ensure casing protection and zonal isolation at elevated temperatures and pressures (up to 450°C and >100 bars). Assess the potential of using high temperature composite casings.

Improve current cement curing kinetics and performance by:

  • Build upon existing knowledge of operating steam injectors and oil producers at ~250°C and related cement testing for STAOIL’s SAGD wells in Alberta, CANADA

  • Develop alternative methods of cementing, i.e. reverse cementing or stage cementing and cement formulations with optimised curing kinetics to allow reduction of curing time from 5-7 days to 2 days.

  • Design cements with reduced supplementary pressure generated by the water in the cement sheath from currently >100 bar to ideally below 30 bar.

  • Determine limitations in curing and final performance of Portland cements at different temperature ranges reaching up to temperatures above 350°C.

  • Development of cements with low grade of shrinkage during curing. Examine alternatives to Portland cements, e.g. silicate-based sealants, calcium phosphate and geopolymers.

Reduce thermal strains and stresses in the wellbore by implementing a ductile layer between casing and cement

  • Conduct lab tests and numerical simulations for placing a ductile and/or compressive surface layer outside of the production casing that allows thermal expansion and shrinkage of the casing in axial direction (in and out of the flexible coupling developed in WP4) and reduces radial stress to avoid damage to the cement sheath (90% reduction of axial strain).

Design and test of high temperature composite casing (HTCC)

  • Qualification test program on prototype HTCC system to increase significantly the temperature limit of composite well materials and obtain verified applicability in high enthalpy geothermal systems in general.

Assess the performance of (hardened) cement and interfaces at representative P/T conditions by a combined experimental/modelling approach

  • Use existing FEM techniques to define requirements for cement blends in different locations of the well and to design and support mechanical testing of standard and new developed cements

  • Perform mechanical and chemical experiments on cements, cemented casings with and without ductile interlayer and/or expandable couplings developed in WP 4

  • Develop innovative (chemical and) mechanical models that are able to predict degradation of well barriers under these conditions supported by experimental tests

  • Generate quantitative requirements for mechanical properties of cement as function of position in the well, requirements for mechanical properties of a ductile intermediate layer also with respect to the design and positioning of flexible connectors developed in WP4.

The proposed experimental testing in WP3 will be conducted at lab facilities at TNO, Statoil, Acquit and IRIS.

 

Dernière mise à jour le 31.05.2016