Demonstration of Geothermal Energy Production Using Carbon Dioxide as a Working Fluid at the SECARB Cranfield Site, Cranfield, Mississippi

Transcription

1 Demonstration of Geothermal Energy Production Using Carbon Dioxide as a Working Fluid at the SECARB Cranfield Site, Cranfield, Mississippi Barry Freifeld, Lehua Pan, and Christine Doughty Earth Sciences Division, Lawrence Berkeley National Laboratory Steve Zakem, Kate Hart and Steve Hostler Echogen Power Systems Inc.

2 CO 2 Geothermal Use CO 2 as a working fluid instead of water. Take advantage of CO 2 s thermodynamic properties to improve system performance

3 Comparing CO 2 with water as a Heat Transmission Fluid Property Water CO 2 Chemistry Mobility Powerful solvent for Non-polar fluid, rock minerals, lots of poor solvent for Properties: dissolution green - favorable, and red - unfavorable rock minerals precipitation High viscosity, high density Low viscosity and moderate density Heat transmission Large specific heat Small specific heat Wellbore circulation Fluid losses Availability Power plant Small compressibility, modest expansivity Expensive and unwanted Widespread, limited in arid regions Higher capital costs, larger footprint Large compressibility and expansivity Credits for GHG mitigation GCS key enabling element More compact, lower capital cost

4 Prior research Donald Brown (LANL) A HOT DRY ROCK GEOTHERMAL ENERGY CONCEPT UTILIZING SUPERCRITICAL CO 2 INSTEAD OF WATER Twenty-Fifth Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, California, January 24-26, 2000 US Patent 6,668,554, granted Dec 30, 2003

5 Prior research used simplified models ignoring momentum and heat transport in the wellbores (isenthalpic decompression) K. Pruess Geothermics 35 (2006) T res = 200 C, P res = 500 bar, T inj = 20 C heat extraction mass flow Q M Energy extraction rate with CO 2 is approximately 50 % larger than with water (average of 75 MW(th) = 13 MWe) Relative advantage of CO 2 becomes larger for lower reservoir temperatures CO 2 inventory: 1.8 Megatonnes For 1,000 MWe, would require Megatonnes of CO 2

6 Combined Geological Carbon Sequestration/Geothermal Heat Extraction Enabling Elements Source of Geothermal Heat Denbury Resources Cranfield Site Jackson Dome Source of CO 2 Echogen Power Systems Equipment to Convert Heat to Electricity

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8 Cranfield CFU-31 US$36M Investment 3 Wells 3.2 km deep Injecting CO 2 since Dec 2009 BHT 127 C BHP 305 bar

9 Echogen Power Systems 25 kg/s commercialscale CO 2 heat recovery system

10 Geothermal Reservoir Simulation Tough 2 Simulation: T2Well/ECO2H Description Conservation of mass and energy Mass accumulation Mass flux Equation d dt M dv = F n dγ + q dv κ κ κ n n n Vn Γ Vn n κ M = φ S ρ X β κ β β β for each mass component F κ = X β ρ u κ β β β for each mass component SECARB Cranfield Demonstration κ Energy flux F = λ T + h ρ u β β β β Porous media Energy accumulation = ( 1 ) R R + κ M ϕ ρ C T ϕ ρ S U β Phase velocity u = k r ( P ρ g) β k µ β β β β β β β Commercial-scale 5-spot grid Energy flux Energy accumulation 2 1 u κ T β F = λ AρβSβ uβ hβ + z A β z 2 ( β ρβ β cos θ) β S u g q'' κ 1 2 M = ρβsβ Uβ + uβ β 2 Wellbore Phase velocity u u G L ρ ρ = C0 um + ud ρ ρ = m * m ( 1 SG C0 ) ρm SG ρg um * ( 1 S ) ρ ( 1 S ) G m L * m G u ρ * m d From: Pruess, Geothermics 35 (2006)

11 T2Well We solve the 2-phase momentum equation using the Drift-flux model (DFM) one integrated system two different sub-domains viscous flow in the wellbore governed by the 1D momentum equation 3D flow through porous media in the reservoir is governed by a multiphase version of Darcy s Law. Connected at well/reservoir interface We use multiphase version of Darcy s Law

12 30-yr simulation results Strong thermosiphon Mass flow rate 5 kg/s 25 kg/s 75kg/s 100kg/s Wellbore feature 7 in 7in* 4 in 7 in 7in* 4 in 7 in 7 in WHP (MPa) WHT ( o C ) Energy (MW) Injection production WHP pro (MPa) WHT pro ( o C) Energy (MW) * No heat exchange in wells

13 Surface Equipment of Operation and Monitoring of CO 2 Thermosiphon 13 US DOE Geothermal Office eere.energy.gov

14 Instrument F3 well with fiber-optic DTS sensor and quartz pressure temperature sensors. 14 US DOE Geothermal Office eere.energy.gov

15 Monitoring and Control System at F3 15 US DOE Geothermal Office eere.energy.gov

16 Flow Iron Producer to Injector 16 US DOE Geothermal Office eere.energy.gov

17 Heatric Exchangers for Cooling CO 2 17 US DOE Geothermal Office eere.energy.gov

18 Operations control center and systems monitoring 18 US DOE Geothermal Office eere.energy.gov

19 Operational Issues producing solids and other items CO 2 Hydrates Uncooperative Winds Plugged Filter 19 US DOE Geothermal Office eere.energy.gov

20 Data Collected DTS fiber-optic temperature logs of F2 and F3 well Quartz pressure and temperature from the reservoir interval in F2 and F3 Fluid pressure and temperature at the outlet of the F3 production tubing Differential pressure across the 100 μ filter unit Emerson Micromotion Coriolis measurement of the fluid mass flux rate and density Pressure and temperature at the Coriolis flowmeter exit Pressure and temperature downstream of the recirculation pressure control valve Pressure and temperature at the outlet of the heat exchangers and inlet to F1 Set point for vent valve Set point for pressure control valve 20 US DOE Geothermal Office eere.energy.gov

21 Thermosiphon Tests at Cranfield 21 US DOE Geothermal Office eere.energy.gov

22 Data Collected

23 Modeled flow rates were much higher than measured. 6 kg/s vs 2 kg/s Modeled injection pressures (F1) were much lower than observed.

24 Lens of clay in uniform layers Layer 2 Layer 5 Layer 6 clay

25 The permeability heterogeneity has big impacts on the siphon performance xy## -- k xy of clay in layer 2= ## md z## -- k z of clay in layer 2 = ## md C56 with clay lens in layer 5 & 6 (k=0.1 md) Low permeability zones have big impacts on the siphon performance, either around F3 in Layer 2 or between F2 and F3 in Layer 5&6. Vertical permeability of clay in Layer 2 has little impacts. Clay lens in Layer 5 & 6 greatly change the behave at later time when the permeability around F3 in layer is not very small (e.g., 50 md) because they reduces the pressure support from F1. Such effect is not significant when the permeability around F3 in layer 2 is already very small (e.g., <=10 md).

26 Conclusions The thermosiphon was set up but was not self-sustaining Water production was higher than predicted (18% observed, 4% predicted) The water produced is thought to have acted as a brake on the system although more work is needed to understand the data For more details on the model see Pan et al., Fully coupled wellbore-reservoir modeling of geothermal heat extraction using CO 2 as the working fluid, Geothermics 53 (2015) 26 US DOE Geothermal Office eere.energy.gov

27 Acknowledgments This work was funded by the Assistant Secretary for Energy Efficiency and Renewable Energy, Geothermal Technologies Program of the U.S. Department of Energy under Contract No. DE-AC02-05CH The authors would like to thank Denbury Resources for support during the CO 2 /Geothermal test and for more than six years of commitment in supporting research at the Cranfield Site. Special thanks to Sue Hovorka for her efforts in facilitating the field operations. 27 US DOE Geothermal Office eere.energy.gov

28 Thanks for your attention. Any questions?