IDDP drilling and well design Project definition for the Pre-Feasibility Report

1. IDDP drilling and well design • Project definition • for the Pre-Feasibility Report • Sverrir Thorhallsson • Orkustofnun, GeoScience Div. • Reykjavik, Iceland • June 25th , 2001 IDDP Drilling Technology Status of the pre-feasibility study Sverrir Thorhallsson Orkustofnun, GeoScience Div. Nesjavellir, Iceland March17th, 2002 s@os.is E-mail: s@os.is

2. IDDP • Major goal: To investigate the roots of a known geothermal system in Iceland by drilling 4-5 km into possible supercritical conditions > 374,15°Cand 221,2 bar (higher for brines) for the extraction of energy and minerals. • Integrate the engineering goals of the IDDP with scientific investigations to the mutual benefit of both. Dual pupose hole ! • The drilling challenge is to design a well and drill, by applying or modifying existing technology.

3. SAGA 1 • Cored pilot hole,then drill production hole. • Cored hole fulllength, then reamfor each casing string. • Spot cores taken in aproduction hole. • Production hole drilledand sidetrack for cores. • Spot cores at each casingshoe, continuous coringof bottom part >3500m.Flow test the well.Ream bottom part forproduction if promising.

4. Drilling challenges • Drilling in uncertain geological and reservoir conditions. • A well control program to allow safe drilling. • Design and materials to withstand the very high T&P. • Continuous coring 3500-5000 m in 350-500°C. • Well cleaning in greatly under-pressured reservoirs. • Straight hole drilling and maintaining well stability. • Cementing of very long casing strings. Cementing losses. • Maintaining adequate penetration rates (m/day). • Mud motors and logging while drilling for high T. • Cooling of well during drilling and logging. • Obtaining good core recovery.

5. IDDP Pre-Feasibility Study • Preparation of the drilling section of the IDDP pre-feasibility study is coordinated by a “Drilling Technology” working group. • Work on the FS is divided into 10 subtasks. • A Deep Vision - Orkustofnun ROS contract has been prepared for the FS and also subcontracts for three of the drilling tasks with Orkustofnun, VGK Consulting and Jarðboranir hf. • Work is ongoing and as will be discussed at the workshop. The group meets every two weeks. Nine months to go !

6. Working group: Drilling Technology • Bjarni Pálsson LV bp@lv.is • Guðmundur Ó. Friðleifsson, DV liasongof@os.is • Kristinn Ingason VGK kristinn@vgk.is • Matthías Matthíasson VGK matthias@vgk.is • Sverrir Þórhallsson, group leader OSs@os.is • Þorbjörn Karlsson HI • Þór Gíslason JB thorgi@jardboranir.is

7. The Engineer’s approach for the FS • Drilling target definition and est. of T & P, geology. • Safety – drilling conditions. • Number of casing strings, depths, diameters. Design. • Drilling / coring, any special req. or operations ? • Mud and cementing programme. • Methods to overcome problems – contingency planning. • Rig and mud system selection. • Information handling – science requirements. • Infrastructure. • Estimate cost and time.

8. Important equipment • Top drive, coring string and core barrels + bits. • Steering equipment to maintain well verticality. • Special hangers and anchors for “technical” string. • High temperature bits, cements and muds. • Stage tools for multiple cementing. • Logging instruments. • Early detection of hostile environments, T&P, gases, low pH fluids. • Specification of rig and mud system.

9. Work plan for the FS - Drilling

10. Estimates of T & P for well design • Boiling point – depth curve to the critical point. • Straight gradient below.

11. Casing Programme • The figure shows a concept sketch of the IDDP well. • 9 5/8” production csg. • 7” liner • The casing profile is similar to a conventional HT geothermal well, but with longer casing strings.

12. Casing programmes

13. IDDP well profile – 9 5/8” prod. csg.

14. Stages of drilling IDDP

15. Modelling of circulation temperatures B A t2 t1 Based on unsteady state heat flow from theformation into the well (A) and energy and massbalance calculations + engineering equitations ofheat flow for this geometry (B), a spreadsheet programwas developed (STAR) to calculate the circulationtemperatures for inside the drill pipe (t1) and annuls (t2). This allows e.g. the formation temperature,loss zones and time of formation cooling to be entered for each depthinterval in addition toinformation on the drill string. No correctionfactors or approximations are used. Main input is the pumping rate and temp.into the drill string. The spreadsheet calculates the temp.inside the DP and in the annulus from a common temp. at thebottom of the hole and then iterates until it reaches the knowninlet temperature.

16. Modeling of the circulation temperature - STAR Q=35 l/s Q=5 l/s Assuming for reservoir boiling point depth curve (BPD) to 3400 m and then 100°C/km gradient

17. Vestmannaeyjar – coring into hot lava 5 years after eruption,1978 4-6 mo. after eruption,1973 Ref. Þorbjörn Sigurbjörnsson, Sveinbjörn Björnsson

18. Drilling system

19. Stagnant and flowing temp. profile - modeling

20. Stagnant and flowing press. profile - modeling

21. Status summary • Well simulation: The well models have been developed for T & P prediction. Scenarios yet to be run. Reservoir ? • A casing program has been selected, but may be modified based on discussions during the workshop. Casing design status will be presented tomorrow. • The use of the Jötunn rig has been evaluated and results will be presented tomorrow. • Coring system is yet to be selected. For this workshop to give guidance. • Other planning work for the FS is ongoing and will be completed by the end of 2002. The Feasibility Report.