Geothermal
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1. What is the average of temperature increas- es with depth within Earth?
25^oC/km
2. What are the decent re- sources of geothermal?
Hydrothermal systems containing water in pores and fractures with sufficient permeability to pro- duce fluids in adequate volume.resence of hydro- carbons
3. Is it true or false, higher temperature and lower pressure in hydrother- mal resources can cre- ate conditions where steam and water, or steam alone, are contin- uous phases.
TRUE
4. What is the other name for steam-alone geot- hermal fields?
"vapor-dominated"
5. What are the parts in ge- othermal system?
(1) geopressured-geothermal systems that con- tain water with somewhat elevated temperatures (above normal gradient) and with pressures well above hydrostatic for their depth, (2) magmatic sys- tems, with temperature from 600 to 1,400°C, and (3) hot dry rock (HDR) geothermal systems, with temperatures from 200 to 350°C.
6. There is one more re- cent addition to the classes of geothermal resource, known as what?
"enhanced geothermal systems" (EGS).
7. Granite, granodiorite, quartzite, greywacke, basalt, and volcanic tuff.
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What are the typical rock types in geother- mal reservoirs?
8. What are the proper- ties of geothermal for- mations, compared to most oil/gas reservoir?
1. Hot (production intervals from 160°C to above 300°C)
2. Hard (240 + MPa compressive strength) 3. Abrasive (quartz content above 50%)
4. highly fractured (fracture apertures of centime- ters)
5. underpressured 9. Is it true or false,
the condition of geot- hermal reservoirs are easy--rate of penetra- tion and bit life are typi- cally high
false -- false
10. What is the type of well for typical geothermal exploration?
Large-diameter, production-size well
11. What is the dis-
advantage from this Hard-rock PDC well?
It's expensive
12. What is the other type of goethermal explo- ration that has cheap- er cost than produc- tion-size wells?
Drilling slimholes; because the rigs, casing and cementing, crews, locations and driliing fluid re- quirements are all smaller
13. What kind of bit that is used in geothermal drilling?
Hard-rock PDC
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14. What is the most used geothermal drilling flu- ids?
Water/bentonite mixture with possible polymer ad- ditives
15. Between oilfield and ge- othermal casing, there is a different. What is it?
With the cement itself because of the requirement high temperature in geothermal reservoir.
16. What kind of cement that is used?
Standard class G cement with addition of retar- dants, approx. 40% silica flour, 4% bentonite and 1% CaCl2
17. In geothermal reservoir, what is the function of tracers?
To determine the connectivity between injection and production wells.
18. There are several meth- ods of stimulation used in geothermal, what are they?
Swabbing, Coil Tubing and liquid nitrogen, Com- pressed Air, Foaming Agents, Decompression, Pumped Wells, Curtailments, Injection
19. Define swabbing! This technique involves lowering a swab down the well, below the water or mud line.
20. What iS the function of foaming agent?
Foaming agents help reduce the weight of the wa- ter column by emulsifying air or nitrogen in the liquid, thus keeping the gas entrained in the liquid and providing greater lift.
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