innovative design of high temperature geothermal wells · geothermal wells ingolfur thorbjornsson...
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The GeoWell project has received funding from the European Union’s
Horizon 2020 research and innovation programme under grant agreement
No 654497
The DEEPEGS project has received funding from the European Union’s
Horizon 2020 research and innovation programme under grant agreement
No 690771
Innovative design of high temperature geothermal wellsIngolfur Thorbjornsson
Head of Geothermal Engineering
Iceland GeoSurvey
Reaching deeper – higher temperatures – harsh chemistry
Simplified model of high temperature system with two feed zones
Temperature rise - thermal expansion
Mitigation of thermal expansion in surface equipment by using thermal expansion loops is common practice in geothermal fields
Designed to prevent damages and displacement of the pipes
Geothermal Well reaching 2-4 km down is drilled and cemented in place – no compensation for thermal expansion??
Same physics applies for materials on surface as downhole
Photo: Gunnar S. Kaldal
High Temperature - Thermal expansion damages of Casing during warm up
Photo: ISOR HS-ORKA Photo: Thorbjornsson
Due to high axial load, the constrained casing either collapse – bulge, or deform locally
And if the need for cooling the well down!
Coupling failures due to high tensile load during cooling from deformed casing segment
Photo: ISOR-IDDP1Photo: ISOR-IDDP1
Flexible couplings
• Allow displacement that compensate for
thermal expansion of the casing
• Stress in the casings will be within the elastic
range
• No plastic strains are therefore generated
• If wells need to be shut-in or quenched with cold
water for maintenance, no axial tension is
generated if the well cools down again
Mitigation
• The Flexible Coupling is designed according to applicable standards, API (American Petroleum Institute) and ISO standards
• Designed with conventional API BTC threads
• Made of L80 material (for K55 and L80 casings)
• Allows clearance for cementing
Flexible couplings
Mitigation
Flexible couplings – function
LT
~12m
• Casings with Flexible coupling are run in hole
with same procedure as normally done
• The couplings remain in their open position
during casing installation
• The gap length LT is fixed for design
temperatures in each case
• When the casing warms up it expands and the
Flexible couplings close without generating
plastic strains in the casing
Main load cases of couplings
• Installation:
• make-up torque
• axial tension (self weight)
• Operational:
• axial compression due to thermal expansion
• axial tension due to cooling
• burst and collapse pressures (radial and hoop loads)
• additional bending
• The Flexible Coupling is designed so that when the casing expands thermally it reaches 70-80% of casing material yield strength without generating plastic deformations
σb-σb
σth
σw
σth
Flexible couplings – Designed and tested
Testing of Flexible Couplings
Testing results:
Tight up to 110 bar (with pressurized water, open position)
Can hold load up to 3000 KN (as build)
Sliding not affected by bending
Sliding force constant with repeatable sliding.
In total 4 full size 9,5/8 Flexible Couplings tested
Photo: Thorbjornsson
Photo: Thorbjornsson
Conclusion
✓ Current design standards for casing design do not prevent plastic deformation of casings due to thermal expansion
✓ Flexible Couplings for high-temperature geothermal wells aim to eliminate these forces by allowing displacement of every casing segment (~12m)
✓ Flexible Couplings have been in development in the EU funded H2020 project GeoWell (and further developed in H2020 project DEEPEGS)
✓ It is our hope that the new solution, Flexible Couplings, can in part solve problems involved in designing and drilling for geothermal wells, conventional as well as high temperatures
Photo: Gunnar S. Kaldal
THANK YOU
www.isor.is