Large-scale subsurface seasonal heat storage for future value

I too extend my welcome. And, I extend thanks to the NSF for the support of this research at the Univ. of Utah. The concept of storing heat in the ground is certainly not new. Many, many cases have investigated heat to be stored underground. Getting the heat underground is somewhat of a problem, but the bigger issue is getting back that heat that has been put underground. It's really not "stored" if one can't recover the heat.

Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value May 19, 2020 Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Acknowledgements • The Workshop is enabled a Grant from the National Science Foundation via EAGER Grant Award 1912670 • Special thanks to the Idaho National Laboratory for early work, in which some of the authors participated, on thermal heat storage, referred to as GeoTES • The contributions and support of Peter Smeallie and Gen Green are appreciated • Opinions Expressed are Those of the Presenters Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Agenda 10:00 a.m. 10:15 a.m. 11:00 a.m. 11:30 a.m. 12:00 p.m. 12:15 p.m. 12:45 p.m. 1:15 p.m. 1:45 p.m. 2:30 p.m. Introduction Heat and Fluid Flow Calculations Operational Considerations Challenges of Sedimentary Basins Break Oil & Gas Industry Perspective Geochemical Considerations Surface Facilities Facilitated Discussion and Summary Adjourn John McLennan & Sidney Green Palash Panja & John McLennan John McLennan Rick Allis Richard Newhart Joe Moore Kevin Kitz Sidney Green Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Adequate Radiance or Other Temporal Heat Source Inadequate Radiance or No Other Temporal Heat Source Heat Exchanger Heat Exchanger Reservoir Supplies Colder Fluid and Stores Hot Fluid Reservoir Takes Colder Fluid and Provides Hot Fluid Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Sid Green - Introduction I too extend my welcome. And, I extend thanks to the NSF for the support of this research at the Univ. of Utah. The concept of storing heat in the ground is certainly not new. Many, many cases have investigated heat to be stored underground. Getting the heat underground is somewhat of a problem, but the bigger issue is getting back that heat that has been put underground. It's really not "stored" if one can't recover the heat. There are also many cases of heating the underground. For examples the oilsands oil recovery in Alberta, Canada, or the heavy oil recovery in Kern County, California. Or heating the earth for insitu oil shale recovery in Utah and Colorado that was considered in the 1970's and even later. There is much experience, in fact every day, injecting hot water or steam into the underground. And we can learn much for these activities. However, heating the ground is very different then storing heat. Injecting hot water or steam to heat the earth, where the water or steam becomes cooled, is in fact the opposite to some extent of storing heat. For storing heat underground, the intent is that the heat continues available to be recovered and used for some economic value. The earth may get heated in the process, but that itself isn't the objective of storing heat. There are many projects in the world recovering hot water or steam from naturally occurring hot formations. The so-called, geothermal energy recovery for direct heat applications or for electricity generation occur every day. This is a case of using the heat that is already in the earth, created over many, many years. We can learn much from these applications too; but that's also not storing heat. It's recovering heat that is already there. When one considers storing heat-for example via hot water or steam-one must remember that there really isn't much energy in a barrel of hot water or steam compared to a barrel of oil. Thus, being able to recover most of the heat that is stored, nearly all of what is injected, in a short time period becomes critical from an economic view. Also, one must remember that if a huge volume of rock mass is required to be heated it will take a long time and require a lot of heat. For example, the volume of rock of say some portion of the geysers reservoir in California, which took hundreds of thousands of years or longer to heat the rock. Such a concept of heating a large mass of rock isn't going to work from an economic point of storing and then recovering heat on a large scale. Not only is heating-cooling rock a slow process because of the low thermal conductivity of rock, but the amount of heat required to heat a large rock mass is huge. This workshop is about storing hot water deep in the earth. What is new is the consideration in a serious manner of high permeability and high porosity relatively homogeneous rock-something that would be found in a sedimentary basin. Water saturated rock is considered with the intent that the pore water would be the carrier of the heat into the reservoir storage tank, and out of the storage tank when the heat is recovered. Only a very small rock mass volume is required for significant heat storage, with the heat really stored in the water with the permeable and porous rock serving as the storage container. The rock-the rock matrix-does get heated as the storage tank is initially charged temperature wise, but because of the small rock mass volume, heating of this small amount of rock becomes practical. Once the reservoir storage tank is heated, it's all about injecting hot water and withdrawing the hot water. This workshop is about the reservoir-the storage container. However, we realize that the surface equipment, both for the solar heat collectors to heat the water on the surface and the conversion of the hot water heat for economy value are certainly a part of any project. But, here we are focusing on the reservoir. Surface equipment can be complicated with a number of options for the most economical application. But it is the reservoir that is really the least constrained. That's why here we are focusing on the reservoir; and here we are focusing on hot water. We understand the thermodynamics of water, and realize that at the same temperature, steam has about two and a half times the enthalpy of hot water per pound. But unfortunately, steam has over thirty-five times the volume of hot water per pound. Thus for steam storage, a reservoir storage tank would be required to be a much larger rock mass volume then for a hot water storage tank for the same heat energy stored. That larger rock mass volume would be a big consideration. Additionally, steam and rock interactions are likely to be even more complicated that for hot water, particularly steam dissolving silica in the rock over shorter periods of time. There is also the issue of the clean water required for the steam, and so forth. However, steam would be better-much better-for electricity generation versus hot water. But for here, we are focusing on hot water as a real possibility. Heat and Fluid Flow Calculations Palash Panja John McLennan Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value The Intellectual Legacy From Hydrology and Energy Engineering • Tsang, C.F., Goranson, C.B., Lippmann, M.J., and Witherspoon, P.A., "Modeling Underground Storage in Aquifers of Hot Water from Solar Power Systems," Lawrence Berkeley Laboratory, May 1977. • Miller, R.T., and Delin, G.N., "Analysis of Thermal Data and Nonisothermal Modeling of Short-Term Test Cycles," U.S. Geological Survey Professional Paper 1530-B, 2002. • Allis, R., Larsen, G., "Compatibility of Binary Geothermal and Solar PV Power Plants," GRC Transactions, Vol. 37, 673-678, 2013. • Wendt, D., et. al., "Geologic Thermal Energy Storage of Solar Heat to Provide a Source of Dispatchable Renewable Power and Seasonal Energy Storage Capacity," GRC Transactions, Vol. 43, 2019. Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value The Intellectual Legacy From Hydrology and Energy Engineering • Holbrook, J., "SedHeat Project," U.S. National Science Foundation, 2018. • Green, S., "Unlocking the Energy Elephant-a SedHeat Workshop- Closing Comments," NSF Sponsored Workshop, Univ. of Utah, March 14, 2017 • Green, S., "Geothermal Battery Energy Storage", SedHeat-ARMA Foundation Pre-Concept Meeting, San Francisco, June 24, 2017 • Dept. of Energy, "Geo Vision: Harnessing the Heat Beneath our Feet," www.osti.gov/seitchc. • McLing, T., et. al., "Dynamic Earth Energy Storage: Terawatt-Year, GridScale Energy Storage using Planet Earth as a Thermal Battery (GeoTES): Seedling Project Final Report," Idaho National Laboratory, INL/EXT-1954025, May 2019. Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value The Intellectual Legacy From the Oil and Gas Industry • Marx, J.W. and Langenheim, R.H., "Reservoir Heating by Hot Fluid Injection," Trans., AIME, 216, 312-15, 1959. • Diaz-Munoz, J., and Farouq Ali, S.M., "Simulation of Cyclic Hot Water Stimulation of Heavy Oil Wells," SPE 5668, 1975. • Prats, M. "Thermal Recovery," SPE Monograph Series Vol. 7, 1982. • Perkins, T.K., and Gonzalez, J.A., "Changes in Earth Stresses Around a Wellbore Caused by Radially Symmetrical Pressure and Temperature Gradients," SPEJ, April 1984. Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value The Intellectual Legacy - Computational Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value The Intellectual Legacy - Pilot Miller, R.T., and Delin, G.N., 2002 • May 1980, U. of Minnesota evaluated storing heated (150°C) water • Franconia-Ironton-Galesville aquifer (183 to 245 m deep) for space heating • System is a doublet-well injectionwithdrawal wells ~250 m apart Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Outline • Calculational Background • Homogeneous and Isotropic Reservoir • Homogeneous and Anisotropic Reservoir • Initial Charging of Reservoir • Summary • Concepts for Further Consideration Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Calculational Background Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Well Set-up and Reservoir Model Plots are Shown Along Mid-Height of Formation to Boundary - Temperature and Pressure at Particular Time At Mid-Height of Formation Temperature and Pressure with Time Vertical permeability = 1/10 horizontal permeability Cylindrical model also studied Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Base Parameters Parameters Formation Specific Heat of Rock (J/(kg-K) Thermal Conductivity (W/(m-K) Density (kg/m3) Horizontal Permeability, kx and ky (mD) Porosity (%) Initial Temperature (O C) Initial Pressure (MPa) Formation Thickness (m) 930 2.5 2000 100 15 120 12 110 Overburden and Underburden 770 1.05 2500 0.0001 2.5 120 12 70 Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Operating Schedule and Boundary Condition • Daily cycle (24 hrs.) Injection 8 hr Production 10 hr Constant Pressure BC Shut-In 6 hr Injection Rate = 40 kg/sec, Total Injection in 8 hrs. = 1152 tonne Production Rate = 32 kg/sec, Total Production in 10 hrs. = 1152 tonne Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Homogeneous and Isotropic Reservoir • Operation: Injection 8 hr Production 10 hr Shut-In 6 hr • Constant Pressure BC Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Effect of Number of Cycles kx = ky = 100 md • • • • Bottomhole temperature reaches 250OC during injection, drops during production. Produced water temperature constant at ~230OC after about 70 cycles. BHP varies +0.8 (injection) to -0.7 (production) MPa from reservoir pressure. During shut-in, pressure goes back to initial reservoir pressure at 12 MPa Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value h = 110 m Effect of Numbers of Cycles 228 165 • Reservoir temperature increases for ~20 meters after 100 daily cycles. • Reservoir became heated to near injection temperature to only ~3 meters. • After producing hot water, reservoir temperature is increased with each cycle. Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Effect of Number of Cycles • Initially, energy recovery increases drastically and then increases slowly • After 40 cycles, overall energy recovery increases asymptotically • Energy recovery in an individual cycle reaches about 95% after ~ 100 cycles • Mirrors Tsang et al., 1977 predictions • Attractive Storage Medium 95 93 90.4 88.2 77 Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Effect of Permeability • As expected, higher injection pressure d in lower permeability due to higher resistance to flow • During equalization, wellbore pressure returns to almost farfield reservoir pressure (12 MPa) • As expected, for permeabilities below ~50 md significant increase in drawdown Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Effect of Permeability • Pressure front in all cases reached boundaries maintained at 12 MPa • Difference between hydrodynamic and thermal fronts • Thermal front insensitive to permeability if the same mass of water injected (see for example, Marx and Langenheim, 1959) Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Effect of Specific Heat of Rock • Specific heat of rock has no effect on pressure during injection, production, shut-in • As expected, temperature increases less in rock with higher specific heat • Remember specific heat is amount of heat required to change temperature of 1 kg by 1 K (consider composite specific heat - water and rock) Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Effect of Formation Thickness • As expected, higher injection pressure is to inject into thinner reservoir • Higher temperature observed at same radial location for thin formation • Mixing front moves farther away from wellbore for thin formation • More losses to over- and underburden for thin formation • Greater extent may be advantageous for overcoming precipitation at thermal front Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Effect of Injection Rate • As expected, higher injection/drawdown required to inject/produce at higher rate • Mixing front moves farther in with greater volumes injected • Higher temperature observed at same radial location for higher injection volume Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Homogeneous and Anisotropic Reservoir • Operation: Injection 8 hr Production 10 hr Shut-In 6 hr • Constant Pressure BC Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Effect of Horizontal Anisotropy (kx/ky) End of injection (30th cycle) on horizontal (x-y) plane (200 m x 200 m) at the mid-height • As expected, pressure front travels faster in x-direction as anisotropy increases • As expected, shape of isobaric contours becomes more elliptical • Pressure at wellbore during injection increases with horizontal anisotropy, recognizing 𝒌𝒌 = 𝒌𝒌𝒙𝒙 𝒌𝒌𝒚𝒚 Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Effect of Horizontal Anisotropy (kx/ky) Bottomhole pressure at mid-height of the formation • Equivalent permeability on horizontal plane (x-y) reduced with increasing anisotropy • Higher injection and lower production pressure for higher anisotropy. • Horizontal permeability anisotropies have similar effect on spatial distribution of temperature Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Initial Charging of Reservoir Charging cycle (24 hrs.) Injection 8 hrs Shut-In 16 hrs Daily cycle (24 hrs.) Injection 8 hrs Production 10 hrs For 30 days + Shut-In 6 hrs For 180 days Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Effect of Initial Charging 98 239 233 94 • Initial charging increases producing water temperature and energy recovery • With charging, produced water temperature increases (239OC vs. 233OC) • With charging, produced water temperatures vary less (0-10OC vs. 17-84OC) • With charging, after 180 cycles, energy recovery higher (98% vs. 94%) Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Summary Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Summary 1. For thick reservoir, significant temperature variations progress only ~20 meters from wellbore with pressure variations up to boundary 2. Temperatures stabilize after 20-30 cycles CONSEQUENCE - RAPID STABILIZATION - SMALLER FORMATION LATERAL EXTENT ADEQUATE - MULTIPLE INJECTION PRODUCTION UNITS IN PROXIMITY (INTERFERENCE NOT CONSIDERED) 3. As predicted by radial flow equations, lower permeabilities lead to higher pressure variations, with increasing pressures with cycles, with a large effect from 50 mD down to 20 mD CONSEQUENCE - PERMEABILITY SWEET SPOT - 50 mD - REDUCED PARASTIC LOADING, ADEQUATE RESISTANCE TO COLLAPSE Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Summary 4. As expected from radial flow relationships, reducing reservoir thickness from 110 meters to 50 meters pushed temperatures out an additional ~5 meters from wellbore. Additionally, lower reservoir thickness leads to much larger pressure cycles. Can be greater conduction into over- and underburden. CONSEQUENCE - DIFFICULT (?) TO FIND THICKER FORMATIONS, MORE CHANCE FOR EROSION (HIGHER VELOCITIES) WITH THINNER FORMATIONS, GREATER PENETRATION OF THERMAL FRONT Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Summary 5. As expected, higher injection rate has same effect on temperature and pressures as lower thickness reservoirs, pushing temperatures out ~5 meters more from the wellbore and producing larger pressure cycles CONSEQUENCE - PICK RATE TO OPTIMIZE HEAT RECOVERY AND PUMPING PARASITIC LOAD (Q∆P), ADEQUATE SURFACE PRESSURE TO MAINTAIN SINGLE PHASE, AVOID EXCESSIVE FRICTION, AVOID MECHANICAL FORMATION DAMAGE (FINES) - IN CONJUNCTION WITH THICKNESS Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Summary 6. Initial 30-day charging of reservoir without producing improves temperature of produced water and overall heat recovery. CONSEQUENCE - SUPERFICIALLY SOUNDS LIKE A GOOD IDEA. COMPLETELY DEPENDENT ON FLUID PUMPED AND ITS DEGREE OF UNDERSATURATION TO SILICA - HOW MUCH DISSOLUTION WILL THERE BE? WILL CONSDEQUENCES OF THIS LONG RESIDENCE TIME BE ALLEVIATED AFTER ONE (OR FEW) PRODUCTION CYCLES? Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Summary 7. As expected, horizontal permeability anisotropy has a significant influence on bottomhole pressure and temperature and their spatial distributions. Pressure and temperature contours become elliptical with anisotropy CONSEQUENCE - WE ALL KNOW THIS BUT RARELY DO THE RESERVOIR CHARACTERIZATION TO QUANTIFY IT (MAYBE INTERFERENCE TESTING HERE) AND LESS FREQUENTLY PUT IT IN SIMULATORS (UNCERTAINTY PARAMETER). IN A SITUATION WHERE WELL PLACEMENT IS CRITICAL UNDERSTANDING THE RESERVOIR IS ESSENTIAL Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Concepts to Advance Development • Run in reactive transport model now (CMG-STARS or similar) • Size reservoir accordingly and do pilot simulations • Multi-well simulations and evaluations of well placement and interference • Size pumping equipment and do basic economics • Consider unintended consequences - thermal cyclicity and degradation of caprock, potential for fines production • Engineering design to de-risk Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Concepts to Advance Development • Thermal front lags. Operationally important consideration for well siting, to avoid injectate capture by natural fractures and to find adequately extensive, high permeability formation with significant net height • In all cases, heat recovery after finite number of cycles was high, over 90% per cycle and, long-scale energy storage of daily to weekly or even seasonal cycles seems possible (geochemistry excluded) 95 93 90.4 88.2 77 Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Appendix Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Heterogeneous Reservoir • Operation: Injection 8 hr Production 10 hr Shut-In 6 hr • Constant Pressure BC Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Effect of Heterogeneity x-y plane (200 m x 200 m) at mid-height 99.9 mD 99.5 mD 94.5 mD 86.7 mD End of injection (30th cycle) 100 mD • Pressure at wellbore higher for higher standard deviation. • Heterogeneity in permeability has less effect on temperature profile Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Effect of Heterogeneity • Drawdown pressures increase with increasing heterogeneity due to low average permeabilities • Shut-in pressure after each cycle reaches far-field reservoir pressure (12 MPa) • Injection and production pressures almost stabilized after 10 cycles of operation Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value CMG-STARS versus TOUGHREACT Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Reservoir Geometry and Numerical Model USER'S GUIDE of TOUGH2-EGS-MP: A Massively Parallel Simulator with Coupled Geomechanics for Fluid and Heat Flow in Enhanced Geothermal Systems Yi Xiong, Perapon Fakcharoenphol, Shihao Wang, Philip H. Winterfeld, Keni Zhang, Yu-Shu Wu Petroleum Engineering Department, Colorado School of Mines December 2013 Figure 6.11. Schematic diagram of injection-production system in vertical fracture injection occurs at I, production at P. (Pruess et al.,1999) the U.S. Department of Energy "Development of Advanced Thermal-HydrologicalMechanical-Chemical (THMC) Modeling Capabilities for Enhanced Geothermal Systems" under Contract No. DE-EE0002762 and by Foundation CMG TOUGH2-EGS is developed based on the framework of TOUGH2 and TOUGHREACT by integrating the EOS3 of TOUGH2 family with geomechanics and reactive geochemistry effects. Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Comparison Figure 6.14 Comparison between CMG-STARS and TOUGH2-EGS: production fluid temperature of the vertical sweep in a vertical fracture problem: no heat gain from surrounding rock Figure 6.15 Comparison between CMG-STARS and TOUGH2EGS: production fluid temperature of the vertical sweep in a vertical fracture problem: with heat gain from surrounding rock Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Subsurface Infrastructure Operational Considerations and Well Layouts John McLennan May 19, 2020 Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Overall System Requirements • Injection Wells to Deliver Hot Water to the Thermal Storage Reservoir • Production Wells to Produce Stored Hot Water from the Thermal Storage Reservoir from Electrical Generation (or Direct Heat) • Production Wells to Produce Formation Water to the Solar Plant (or equivalent) for Heating • Injection Wells to Discharge Thermally-Exhausted Water Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Schematic Storage-Production Unit Nominal Outer Composite Radius of "Influence" High Deliverability Hot Water Producer Nominal Thermal Front Hot Water Injector Feed Water Producer (Supply Water to be Heated ) and Injector (Discharged Water) 2r*e Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Hot Water Production Hot Water Producer What are the Requirements? • High Deliverability • Facilitates Lifting Fluid with Phase Change or Pumping • Avoid Scaling - Will be a Reduction in Pressure But Temperature High • Unrestricted but Supported Contact with Formation (Screens) Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value What are the Considerations? • Multiple Formations • Crossflow • Fines Production and "Hot" Spots • Partial Completion • Moving Silica-Saturated Fluid to Surface •… Distance Above Datum (m) Hot Water Production: Geologic Nuances Temperature (°C) Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value What are the Considerations? • Multiple Formations • Crossflow • Fines Production and "Hot" Spots • Partial Completion • Moving Silica-Saturated Fluid to Surface •… Distance Above Datum (m) Hot Water Production: Geologic Nuances Temperature (°C) Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value After Miller and Delin, 2002, and modified from Muecke, 1978 Hot Water Production: Geologic Nuances What are the Considerations? • Multiple Formations • Crossflow • Fines Production and "Hot" Spots (rates may not be high enough) • Partial Completion • Moving Silica-Saturated Fluid to Surface •… After Guo et al., 2014 Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Hot Water Production: Geologic Nuances What are the Considerations? • Multiple Formations • Crossflow • Fines Production and "Hot" Spots (rates may not be high enough) • Partial Penetration and Completion • Moving Silica-Saturated Fluid to Surface •… After Tsang et al., 1977 Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Hot Water Production: Geologic Nuances What are the Considerations? • Multiple Formations • Crossflow • Fines Production and "Hot" Spots (rates may not be high enough) • Partial Penetration and Completion • Moving Silica-Saturated Fluid to Surface •… • Should the injection/production temperature be reduced to 200°C (pumping and reduced dissolved silica)? • Handling silica at the surface? • Other precipitates? • More coming up (Moore coming up) Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Hot Water Injection: Geologic Nuances What are the Considerations? • Similar Completions Considerations to Production Well • Careful Development of Reservoir • How to Establish Equilibrium? • Do You Need to Move Fluid Continuously • Interference Nominal Thermal Front Hot Water Injector Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Hot Water Injection: Geologic Nuances • What Hydrodynamic Front versus are the Considerations? Front •Thermal Similar Completions Considerations • Hot and Cold Well Fluid Moving to Production Crossing a of •Outwards/Inwards Need to be High Capacity Because Scale Potential Steep Thermal Gradient Do You Need to Move Fluid • •Precipitation/Dissolution? Continuously • What Wins? • How to Establish Equilibrium? • Interference Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Cold Water Supply and Discharge: Geologic Nuances High Deliverability Hot Water Producer Hot Water Injector Feed Water Producer (Supply Water to be Heated ) and Injector (Discharged Water) Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Cold Water Supply and Discharge: Geologic Nuances What are the Considerations? Bringing Colder Water to Surface for Heating • Similar Completions Considerations to Other Wells • Producing at Same Time as High Deliverability Hot Water Injection Hot Water Producer • Interference and Outwards Extension of Hot Water Zone? Hot Water Injector • Progressive Warming Feed Water Producer (Supply of "Cold" Water Source Water to be Heated ) and Injector • Surface Scaling? (Discharged Water) Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Cold Water Supply and Discharge: Geologic Nuances What are the Considerations? Bringing Colder Water from Surface After Heat Exchange • Similar Completions Considerations to Supply Well • Injecting at Same Time as High Deliverability Hot Water Producer Hot Water Production • Interference and Inwards Gradient? Hot Water Injector • Progressive Cooling Feed Water Producer (Supply of "Cold" Water Source Water to be Heated ) and Injector • Silica Scaling? (Discharged Water) Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Other Considerations Disposable or Sacrificial Zones • Sliding Sleeves Activated with Coiled Tubing or Dropping Balls and Pressure • Mechanically Blocks Off and Opens New Zone • Cost but May be Justified Modified After Guo et al., 2014 Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Other Considerations Nomadic Units • If Injectivity or Productivity Downhole is Irrecoverably Lost • Migrate Borefield • That Requires Cheaper Drilling Options and Slimhole Coiled Tubing May be Option Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value More Elegant and Less Expensive Well Plans After Wendt et al., 2019 Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value Synopsis • Geochemical Considerations are Prominent • Necessary to be Able to Drill and Complete Wells Cheaply, Even if Inclined - This is Not Out of the Question But Need to Move Significant Volumes of Fluid • Completion Duality Desirable • Application of Careful Engineering and Computation to Mitigate Geochemical and Parasitic Losses • Possibly Back Off of the Temperature • Sacrificial and Disposable Wellbores, Completion Components, Zones • Are There Unintended Consequences? Large-Scale Subsurface Seasonal Solar Heat Storage for Future Value [e-mail]