geothermal reservoir engineering

GEOTHERMAL RESERVOIR GEOTHERMAL RESERVOIR ENGINEERINGENGINEERING

INTERNATIONAL SUMMER SCHOOL ONGEOTHERMAL GEOCHEMISRTY

02-15 June 2003İzmir - TURKEY

Prof. Dr. Mahmut PARLAKTUNAMIDDLE EAST TECHNICAL UNIVERSITY

PETROLEUM AND NATURAL GAS ENGINEERING

June 11, 2003International Summer School on Geothermal Geochemistry

İZMİR JENARUM YAZ OKULU

RESERVOIR ENGINEERINGRESERVOIR ENGINEERING

Determination of well locations Planning and interpretation of well measurements (well logging, production rates, etc.) Determination of production mechanism Performance prediction studies of reservoir behavior



RESERVOIR ENGINEERINGRESERVOIR ENGINEERINGULTIMATE GOALULTIMATE GOAL

Determination of optimum production conditions to maximize

the heat recovery from the reservoir under suitable economic conditions



QUESTIONS TO BE ANSWERED QUESTIONS TO BE ANSWERED

Most suitable development plan of the reservoir Number of wells with well pattern Production rates of the wellbores Heat that will be recovered Change in reservoir temperature with time Enhanced recovery techniques to increase the heat recovery from the reservoir



STEPS STEPS

Define the physical processes and develop the conceptual model of the reservoir Determine the physical and chemical properties of reservoir rock and fluid Develop the mathematical and physical models of the reservoir with the help of existing data. Define initial and boundary conditions



SOME FACTORS SPECIFIC TO SOME FACTORS SPECIFIC TO GEOTHERMAL RESERVOIRSGEOTHERMAL RESERVOIRS

Relatively high reservoir temperatures Volcanic origin of rocks with highly fractured characteristics Chemical precipitation of solids within the reservoir during production Boiling of water within the reservoir and/or wellbore



GEOTHERMAL SYSTEMS GEOTHERMAL SYSTEMS

Required conditions A heat source A heat carrier (except HDR) Reservoir rock Caprock



GEOTHERMAL SYSTEMS GEOTHERMAL SYSTEMS

(Dickson and Fanelli, 1995)



GEOTHERMAL SYSTEMSGEOTHERMAL SYSTEMS

Vapor dominated systems Liquid dominated systems Geo-pressured reservoirs Hot dry rock (HDR)



ENERGY DENSITIES OF GEOTHERMAL ENERGY DENSITIES OF GEOTHERMAL SYSTEMSSYSTEMS



ASSUMPTIONSASSUMPTIONS

A hypothetical geothermal reservoir– Porosity = 20 %– Initial pressure = 47 bar– Initial temperature = 260 C– 7 bar pressure decline due to fluid production– The reservoir fluid is at either saturated liquid

or saturated vapor state



SCENARIOSSCENARIOS

Scenario-1– Originally water, remaining water

Scenario -2– Originally water, becoming steam

Scenario -3– Originally steam, remaining steam



PHASE DIAGRAMPHASE DIAGRAM



STEAM TABLESSTEAM TABLEST T P vliquid vsteam Hliquid Hsteam Hsb Sliquid Ssteam

(°C) (K) (bar) (m3/kg) (m3/kg) (kJ/kg) (kJ/kg) (kJ/kg) (kJ/kg K) (kJ/kg K)45 318.15 0.09582 0.0010099 15.280 188.35 2583.3 2395.0 0.6383 8.1661

46 319.15 0.10086 0.0010103 14.560 192.53 2585.1 2392.6 0.6514 8.1481

47 320.15 0.10612 0.0010107 13.880 196.71 2586.9 2390.2 0.6645 8.1302

48 321.15 0.11162 0.0010112 13.230 200.89 2588.6 2387.7 0.6776 8.1125

49 322.15 0.11736 0.0010117 12.620 206.87 2590.4 2383.5 0.6906 8.0950

50 323.15 0.12335 0.0010121 12.050 209.26 2592.2 2382.9 0.7035 8.0776

51 324.15 0.12961 0.0010126 11.500 213.44 2593.9 2380.5 0.7164 8.0603

52 325.15 0.13613 0.0010131 10.980 217.62 2595.7 2378.1 0.7293 8.0432

53 326.15 0.14293 0.0010136 10.490 221.80 2597.5 2375.7 0.7422 8.0262

54 327.15 0.15002 0.0010140 10.020 225.98 2599.2 2373.2 0.7550 8.0093

55 328.15 0.15741 0.0010145 9.579 230.17 2601.0 2370.8 0.7677 7.9926

56 329.15 0.16511 0.0010150 9.159 234.35 2602.7 2368.4 0.7804 7.9759

57 330.15 0.17313 0.0010156 8.760 238.53 2604.5 2366.0 0.7931 7.9595

58 331.15 0.18147 0.0010161 8.381 242.72 2606.2 2363.5 0.8058 7.9431

59 332.15 0.19016 0.0010166 8.021 246.91 2608.0 2361.1 0.8184 7.9269

60 333.15 0.1992 0.0010171 7.679 251.09 2609.7 2358.6 0.8310 7.9108



SCENARIOSSCENARIOS

240

245

250

255

260

265

270

0 500 1000 1500 2000 2500 3000

Enthalpy (kJ/kg)

Tem

pera

ture

(°C

)

Scenario-1Scenario-2Scenario-3



Scenario-1Scenario-1 Initially at 260 C

hw1 = 1134.9 kJ/kg Vw1 = 1.275610-3 m3/kg Ew1=1.780 105 kJ/m3

After 30 years production hw2 = 1085.8 kJ/kg Vw2 = 1.2513 10-3 m3/kg Ew2=1.7355 105 kJ/m3

Energy produced from waterEw=4452.5 kJ/m3

Energy produced from rockEr=22857 kJ/m3

Total energy Ea= 27309.5 kJ/m3

83.7 % from rock




hw1 = 1134.9 kJ/kg Vw1 = 1.275610-3 m3/kg Ew1=1.780 105 kJ/m3

After 30 years production hs2 = 2800.4 kJ/kg Vs2 = 50.37 10-3 m3/kg Es2=1.1193 104 kJ/m3

Energy produced from water Ew-s=166180 kJ/m3


Total energyEa= 189670 kJ/m3

12.1 % from rock




hs1 = 2796.4 kJ/kg Vs1 = 42.13410-3 m3/kg Es1=1.3274 104 kJ/m3

Energy produced from steamEw=2080 kJ/m3


Total energy Ea= 24938 kJ/m3

91.7 % from rock

After 30 years production hs2 = 2800.4 kJ/kg Vs2 = 50.37 10-3 m3/kg Es2=1.1193 104 kJ/m3



Volume of reservoir to supply a 100 MW power station with steam for a period of 30 years

Eelec= 9.46 1016 J Ethermal= 59.46 1016 J (20 % efficiency)

Scenario 1V= 1.7319 1010 m3

Scenario 2V=0.2494 1010 m3

Scenario 3V=1.8967 1010 m3



Temperature measurementsTemperature measurements



Negative Temperature GradientNegative Temperature Gradient



Flowing wellFlowing well



Closed wellClosed well



Temperature ProfilesTemperature Profiles



Well Completion TestWell Completion Test

Injection of cold wtaer into the wellbore The two main parameters measured

Water loss Permeability



Water Loss TestWater Loss Test



ExampleExample



Pressure ProfilesPressure Profiles



PRESSURE TRANSIENT TESTINGPRESSURE TRANSIENT TESTINGBUILD-UP TESTBUILD-UP TEST

Time

Prod

uctio

n ra

te

tp

q = 0

q = Constant

Time

Pres

sure



PRESSURE TRANSIENT TESTINGPRESSURE TRANSIENT TESTINGBUILD-UP TESTBUILD-UP TEST

Time

Pres

sure

Slope is proportional toPERMEABILITY



PRESSURE TRANSIENT TESTINGPRESSURE TRANSIENT TESTINGDRAWDOWN TESTDRAWDOWN TEST

Time

Prod

uctio

n ra

te

q = Constant

Stabilized conditions

Time

Pres

sure



PRESSURE TRANSIENT TESTINGPRESSURE TRANSIENT TESTINGDRAWDOWN TESTDRAWDOWN TEST

Time

Pres

sure

Slope is proportional toPERMEABILITY



PRESSURE TRANSIENT TESTINGPRESSURE TRANSIENT TESTINGINTERFERENCE TESTINTERFERENCE TEST



TRACER TESTTRACER TEST

A tracer is an identifiable substance that can be followed through the course of a process

Tracers - Radioactive tracers: NaI, NH4Br, I131, Br82, H3

- Chemical tracers: NaCl, CaCl2,- Organic Dyes: Fluoresceine, Rhodamine-B, Methylene Blue- Conventioanl tracers are identified by conventional analytical methods such as CONDUCTIMETRY, SPECTROMETRY-Radioactive tracers are detected by the emitted radiation

geothermal reservoir engineering

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