Geothermal Energy is the Ethical Energy Geothermal Energy is the Ethical Energy Source for the Future Source for the Future

Will GosnoldWill GosnoldDept. of Geology and Geological EngineeringDept. of Geology and Geological Engineering

Donald PoochigianDonald PoochigianDept. of Philosophy and ReligionDept. of Philosophy and Religion

Geothermal Energy Generation in Oil Geothermal Energy Generation in Oil and Gas Settings Conference March 13-and Gas Settings Conference March 13-14, 2006 Southern Methodist University14, 2006 Southern Methodist University

http://www.smu.edu/geothermal/Oil&Gas/presentations.htm

OutlineOutlineHeat flow and subsurface temperaturesHeat flow and subsurface temperatures

Thermal blanketing effect of shales and heat Thermal blanketing effect of shales and heat advection in regional groundwater flow advection in regional groundwater flow systems systems

ThermostratigraphyThermostratigraphy

Bottom hole temperatures and equilibrium Bottom hole temperatures and equilibrium temperaturestemperatures

Estimates of the energy resourceEstimates of the energy resource

21st Century Global Warming

Climate Simulations for IPCC 2007 Report

► Climate Model Sensitivity ~ 2.7ºC for 2xCO2 (consistent with paleoclimate data & other models)Source: Hansen et al., to be submitted to J. Geophys. Res.

The energy source we choose for the future must be as free as possible from detrimental environmental impact.

Normal continental heat flow regions Normal continental heat flow regions can have good geothermal resource can have good geothermal resource potential.potential.

The thermal blanketing effect of low The thermal blanketing effect of low conductivity rocks such as shales conductivity rocks such as shales focused distribution of heat by focused distribution of heat by advection in regional groundwater flow advection in regional groundwater flow systems enhance geothermal potential.systems enhance geothermal potential.

Heat FlowHeat Flow

Geothermal Map of North America, 2004

D. Blackwell and M. Richards, Eds.,

Most of the heat flow sites in Nebraska and South Dakota were drilled with funding from the US Department of Energy’s geothermal programs.

T-z profiles in Nebraska from DOE Geothermal Program

T-z profiles in South Dakota from DOE Geothermal Program

D.D. Blackwell, 2006

D.D. Blackwell, 2006

Favorable conditions for EGS resources are:Depths less than 7 kmTemperatures >150°C. There are at least 17 million km2 with these requirementsTotal thermal energy potential ix 8.6 x 1024Joules.

The EGS resource base for Texas alone (temperature above 150°C(300°F) and depths less than 7 km ) is 255,000 EJ, or 4.1x108 MW secs-20yrs.

If a recovery factor of 1% is used there is still 4.1x106

MW sec for 20 years available (the present installed electrical power capacity in Texas of 0.1x106 MWe).

The US Geological Survey has estimated the resource in the geopressured setting in Texas and Louisiana to be 1.74x1014 MW-20 yrs plus the dissolved gas (109 mcf).

The geothermal estimate of the USGS is in addition to the EGS component of the resource.

The dissolved gas geopressure also is an additional resource that would be otherwise uneconomical to produce.

Heat flow contours of South Dakota and Nebraska showing the effects of regional groundwater flow

The site at Burton, NE The site at Burton, NE provided the crucial provided the crucial piece of evidence for piece of evidence for groundwater flow as groundwater flow as the source of the the source of the thermal anomaly.thermal anomaly.

A simple geological profile tested a model of the thermal effects of water flow from the Black Hills eastward.

Geothermal Map of North America, 2004

D. Blackwell and M. Richards, Eds.,

QdT

dzKQ

dT

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T z Tz Q

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1

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T z Tz Q

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QdT

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QdT

dZK

T z TZ

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Thermostratigraphy is the application of Fourier’s law of heat Thermostratigraphy is the application of Fourier’s law of heat conduction to calculate temperature at depthconduction to calculate temperature at depth

Determine Q from equilibrium T-z and K.Determine Q from equilibrium T-z and K.Assume Q is constant, K and dz are knownAssume Q is constant, K and dz are known

Estimate geothermal energy in Estimate geothermal energy in ND and SDND and SD

Colors are temperature, contours are depth (m), lines are county boundaries

BHT’s and ObservationsBHT’s and Observations

Although BHT data are useful, they often Although BHT data are useful, they often do not indicate actual temperatures at do not indicate actual temperatures at depth.depth.

The example from the Williston Basin is The example from the Williston Basin is typical.typical.

qr = ρcvad(t-tref)

The energy resource in Joules is calculated by

Surfer© GRID routines were used to calculate the volume of the formation above the reference temperature, e.g. 90 °C

Madison Fm = 1476 EJ

Energy estimates for Energy estimates for the Williston Basinthe Williston Basin

Coal ~ 118 EJCoal ~ 118 EJ

Geothermal ~23 EJGeothermal ~23 EJ

Oil ~ 20 EJOil ~ 20 EJ

SummarySummaryNormal continental heat flow and subsurface temperatures Normal continental heat flow and subsurface temperatures characterize most of the region.characterize most of the region.

Thermal blanketing effect of shales and heat advection in Thermal blanketing effect of shales and heat advection in regional groundwater flow systems cause regional thermal regional groundwater flow systems cause regional thermal anomalies.anomalies.

Heat flow, thermal properties, and stratigraphy can be used to Heat flow, thermal properties, and stratigraphy can be used to determine subsurface temperatures with good accuracy.determine subsurface temperatures with good accuracy.

Bottom hole temperatures and equilibrium temperatures may Bottom hole temperatures and equilibrium temperatures may differ.differ.

Temperatures of 180 °C can be found in the deeper regions of Temperatures of 180 °C can be found in the deeper regions of the Williston Basin and temperatures greater than 90 °C occur the Williston Basin and temperatures greater than 90 °C occur widely in the basin. widely in the basin.

In general, the recoverable stratabound geothermal resource in In general, the recoverable stratabound geothermal resource in the region exceeds the energy that could be recovered from oil.the region exceeds the energy that could be recovered from oil.

Philosophical QuestionsPhilosophical Questions

How long will oil last?How long will oil last?

When does the world cross the threshold When does the world cross the threshold for disastrous climate change?for disastrous climate change?

What can the scientific community do?What can the scientific community do?

North Dakota morning commuteNorth Dakota morning commute

“If you consider it a sport to gather your food by drilling through 8 inches of ice and sitting there all day hoping that the food will swim by,you might live in North Dakota.” Jeff Foxworthy