Target Exploration Geothermal Gradients & Geothermal Gradient
Mapping Geothermal Production Potential Printing · Clean, renewable energy is of ever-increasing...
1
Mapping Geothermal Production Potential Rowan Kowalsky 1 , Craig Hartline 2 , Mark Walters 2 1: The Colorado College, 2: Calpine Corporation ABSTRACT Clean, renewable energy is of ever-increasing importance and attainability. A rapidly growing sector of this economy is geothermal power production. Geothermal power utilizes heat sources anomalously close to the surface of the Earth. Locating these heat sources, and quantifying how much ‘geothermal potential’ they have is an evolving process. By taking a closer look at the physics behind hot fluid flow in fractured mediums, we determine that the influential and measurable indicators of geothermal potential are permeability of the rock (k) and the temperature gradient( ℉ 100 ). Here, the geophysical method of measuring and analyzing temperature gradients is used to locate areas of high geothermal potential within The Geysers geothermal field owned by the Calpine Corporation in northern California. Two localized heat sources have been identified, but their temperature gradient signatures appear to be altered by fault structures that dramatically increase permeability along the fault planes. Locating these fault planes can dramatically increase the geothermal production potential of an area. GEOTHERMAL BACKGROUND DARCY VELOCITIES THERMAL PLUMES • To describe velocities of fluid moving through fractured rock, it is more useful to describe the average motion of the advancing front, rather than describe the instantaneous velocity for any smaller package. Darcy velocities are volumetric flow rates per unit area of the rock. RESULTS CONCLUSIONS The vertical velocity can be written; If describing water at equilibrium in the ground. To describe hot water conducting to the surface, we can write; The image below is a sketch of a thermal plume. This is a body of heated water that has begun to convect above a point source of heat. To apply conservation of mass, it is helpful to take a small, axisymmetric shell and assume flow in = flow out. The same amount of heat per unit time should pass through each of the shaded shapes, and that flux is related to the volumetric flux of the fluid. Integrating over the whole thermal plume will yield an expression for heat energy per unit time per unit area. A good Geothermal site requires three things; 1. A shallow heat source ( km scale ) 2. Fractured rock 3. Fluid For the rest of the poster, we will be exploring the physics of how heat is carried by water circulating through fractured rock. INFLUENTIAL VARIABLES Using the equations for Darcy velocity, conservation of mass, heat flux, and a modified advection-diffusion equation (not discussed here), a new equation describing thermal plumes can be written; Keeping in mind that ℎ can be described by; We see that the variables listed in red are the most influential in governing the plume. − 0 becomes squared in the heat flux equation. can vary over ten orders of magnitude. 2 2 governs the shape of the plume, and indicates how much the hot water has spread laterally or remained concentrated above the point source. Temperature gradient data ( ℉ 100 ) serves to measure the − 0 and the denominator of the ratio 2 2 describing the plume (which varies much more than the radius). Here are temperature gradient contours for The Geysers geothermal field located in northern California. The highest contour is 40 ℉ 100 . The southeast corner has concentrations of temperature gradient contours that match the surface expressions of thermal plumes. We would expect a point source to be directly beneath these plumes. However, the subsurface point source ( currently thought to be a spire of cooling magma named The Felsite) is mapped several kilometers to the east of where the thermal plumes surface. What can cause this to happen? Large fault planes that intersect thermal plumes can redirect the fluid, and consequently the heat. k values drop dramatically along active fault planes. The smaller black polygon is the area I was sent to map. I was looking for surface expressions of a large fault system believed to be redirecting the plumes. Before After Before and after images of my mapping area. The contacts between different types of rocks can be interpreted as fault zones when they suddenly change direction. Several of my new contacts fit this pattern, and all along the proposed locations of major fault planes (indicated by the dotted lines) If the geophysicists at The Geysers can accurately locate these fault planes at depth, the company can drill their production wells into those planes. This will maximize their energy output. Locating fault planes can also lower drilling costs, because the company doesn’t have to drill down as close to the point source. Image courtesy of Calpine Corporation Where − 0 is the temperature anomaly of the water in degrees Kelvin. Acknowledgments: “Chapters 4,6,9.” Geodynamics, by Donald L. Turcotte and Gerald Schubert, 3rd ed., Cambridge University Press, 2014. Forson, Corina; Sadowski, A. “Geologic Map of The Geysers Steamfield” Sep.2017 Hartline, Craig; Walters, M. The Geysers, Calpine Corporation. Middletown, CA Hartline, Craig; Dunlev, C; Forson, C. “3-D Model Building.” GRC, vol. 39, 15 Aug. 2016. Reid, Nathan.; Ossner, J. “Geologic History of Northern California” USGS 1976. Stephanie, Will, Tamara, and Dick for their help understanding physical concepts and checking my work Craig Hartline and Mark Walters for helping me map The Geysers and understand the subsurface.
Transcript of Mapping Geothermal Production Potential Printing · Clean, renewable energy is of ever-increasing...
Printing:This poster is 48” wide by 36” high. It’s designed to be printed on a large
Customizing the Content:The placeholders in this formatted for you. placeholders to add text, or click an icon to add a table, chart, SmartArt graphic, picture or multimedia file.
Tfrom text, just click the Bullets button on the Home tab.
If you need more placeholders for titles, make a copy of what you need and drag it into place. PowerPoint’s Smart Guides will help you align it with everything else.
Want to use your own pictures instead of ours? No problem! Just rightChange Picture. Maintain the proportion of pictures as you resize by dragging a corner.
Mapping Geothermal Production PotentialRowan Kowalsky1 , Craig Hartline2 , Mark Walters2
1: The Colorado College, 2: Calpine Corporation
ABSTRACTClean, renewable energy is of ever-increasing importance and attainability. A rapidly growing sector of this economy is geothermal power production. Geothermal power utilizes heat sources anomalously close to the surface of the Earth. Locating these heat sources, and quantifying how much ‘geothermal potential’ they have is an evolving process. By taking a closer look at the physics behind hot fluid flow in fractured mediums, we determine that the influential and measurable indicators of geothermal potential are permeability of the rock (k) and the temperature
gradient(℉
100𝑓𝑡). Here, the geophysical method of measuring and analyzing
temperature gradients is used to locate areas of high geothermal potential within The Geysers geothermal field owned by the Calpine Corporation in northern California. Two localized heat sources have been identified, but their temperature gradient signatures appear to be altered by fault structures that dramatically increase permeability along the fault planes. Locating these fault planes can dramatically increase the geothermal production potential of an area.
GEOTHERMAL BACKGROUND
DARCY VELOCITIES
THERMAL PLUMES
• To describe velocities of fluid moving through fractured rock, it is more useful to describe the average motion of the advancing front, rather than describe the instantaneous velocity for any smaller package. Darcy velocities are volumetric flow rates per unit area of the rock.
RESULTS
CONCLUSIONS
The vertical velocity can be written;
If describing water at equilibrium in the ground. To describe hot water conducting to the surface, we can write;
The image below is a sketch of a thermal plume. This is a body of heated water that has begun to convect above a point source of heat. To apply conservation of mass, it is helpful to take a small, axisymmetric shell and assume flow in = flow out.
The same amount of heat per unit time should pass through each of the shaded shapes, and that flux is related to the volumetric flux of the fluid. Integrating over the whole thermal plume will yield an expression for heat energy per unit time per unit area.
A good Geothermal site requires three things;1. A shallow heat source ( km scale )2. Fractured rock3. Fluid
For the rest of the poster, we will be exploring the physics of how heat is carried by water circulating through fractured rock.
INFLUENTIAL VARIABLES
Using the equations for Darcy velocity, conservation of mass, heat flux, and a modified advection-diffusion equation (not discussed here), a new equation describing thermal plumes can be written;
Keeping in mind that 𝑄ℎcan be described by;
We see that the variables listed in red are the most influential in governing the plume.𝑇 − 𝑇0 becomes squared in the heat flux equation. 𝑘 can vary over ten orders of
magnitude. 𝑟2
𝑦2governs the shape of the plume, and indicates how much the hot water
has spread laterally or remained concentrated above the point source.
Temperature gradient data (℉
100𝑓𝑡) serves to measure the 𝑇 − 𝑇0 and the denominator of the
ratio 𝑟2
𝑦2describing the plume (which varies much more than the radius).
Here are temperature gradient contours for The Geysers geothermal field located in northern California. The highest contour is
40℉
100𝑓𝑡. The southeast corner has
concentrations of temperature gradient contours that match the surface expressions of thermal plumes.
We would expect a point source to be directly beneath these plumes. However, the subsurface point source ( currently thought to be a spire of cooling magma named The Felsite) is mapped several kilometers to the east of where the thermal plumes surface.
What can cause this to happen? Large fault planes that intersect thermal plumes can redirect the fluid, and consequently the heat. k values drop dramatically along active fault planes. The smaller black polygon is the area I was sent to map. I was looking for surface expressions of a large fault system believed to be redirecting the plumes.
Before
After
Before and after images of my mapping area. The contacts between different types of rocks can be interpreted as fault zones when they suddenly change direction. Several of my new contacts fit this pattern, and all along the proposed locations of major fault planes (indicated by the dotted lines)
If the geophysicists at The Geysers can accurately locate these fault planes at depth, the company can drill their production wells into those planes. This will maximize their energy output. Locating fault planes can also lower drilling costs, because the company doesn’t have to drill down as close to the point source.
Image courtesy of Calpine Corporation
Where 𝑇 − 𝑇0 is the temperature anomaly of the water in degrees Kelvin. Acknowledgments:“Chapters 4,6,9.” Geodynamics, by Donald L. Turcotte and Gerald Schubert,
3rd ed., Cambridge University Press, 2014.Forson, Corina; Sadowski, A. “Geologic Map of The Geysers Steamfield” Sep.2017Hartline, Craig; Walters, M. The Geysers, Calpine Corporation. Middletown, CA
Hartline, Craig; Dunlev, C; Forson, C. “3-D Model Building.” GRC, vol. 39, 15 Aug. 2016.Reid, Nathan.; Ossner, J. “Geologic History of Northern California” USGS 1976.Stephanie, Will, Tamara, and Dick for their help understanding physical concepts
and checking my workCraig Hartline and Mark Walters for helping me map The Geysers and understand
the subsurface.
