The aim of the Iceland Deep Drilling Project (IDDP) is to
drill a 4-5 km deep exploration well into a high-
temperature geothermal system in order to reach 400-
600°C hot supercritical hydrous fluid. The main purpose
of the IDDP is to find out if it is economically feasible to
extract energy and chemicals out of hydrothermal
systems at supercritical conditions.
• The IDDP design premises were initially
assessed on basis of the presumed deep temperature
and pressure values at the depth of 5,000 m. Two
possibilities were considered, viz.:
Linear extrapolation from the established temperature
and pressure values pertaining to the critical point in
fresh water (374.15°C and 22.12 MPa)1, and
considered to exist at a depth of 3,500 m. Linear
extrapolation to 5,000 m depth yields a temperature of
about 550°C and 25 MPa pressure.
• Estimation based upon “Isochor” behaviour
would on the other hand yield 391°C and 26.7 MPa at a
depth of 5,000 m.
Three alternative temperature and pressure cases are
selected for assessing load and stress conditions in the
upper part of the anchor casing, the wellhead flange
and the wellhead master valve.
T= 500°C and P= 19,5 MPa (Linear)
T= 340°C and P= 14,5 MPa (Isochor)
T= 400°C and P= 22 Mpa
T= 20°C and P= 26.7 MPa
The casing design is based on the ASME Boiler and
Pressure Vessel Code, Section VIII, Div 2, Alternative
Rules. Addenda July 1, 2003, and ANSI and API
standards for flanges and valves. The design consisted
of the following:
• Design of anchor and production casings;
ensuring strength integrity; materials and couplings
• Selection of materials and pressure class for
wellhead master valve.
• Selection materials and pressure class for
wellhead master valve flanges.
The conclusion was to use thick K-55 grade steel for the
casings, except for the top 300 m of the anchor casing
where T-95 would be used due to its creep resistance.
The connections are Hydril 563 couplings and threads
for the anchor and production casing, Wellhead and
valves are to be of ANSI pressure Class 2500.