Transcript Slide 1

Geothermal Energy is the Ethical Energy
Source for the Future
Will Gosnold
Dept. of Geology and Geological Engineering
Donald Poochigian
Dept. of Philosophy and Religion
Geothermal Energy Generation in Oil
and Gas Settings Conference March 1314, 2006 Southern Methodist University
http://www.smu.edu/geothermal/Oil&
Gas/presentations.htm
Outline
Heat flow and subsurface temperatures
Thermal blanketing effect of shales and heat
advection in regional groundwater flow
systems
Thermostratigraphy
Bottom hole temperatures and equilibrium
temperatures
Estimates 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.
Heat Flow
Normal continental heat flow regions
can have good geothermal resource
potential.
The thermal blanketing effect of low
conductivity rocks such as shales
focused distribution of heat by
advection in regional groundwater flow
systems enhance geothermal potential.
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
km
Temperatures
>150°C.
There are at least
17 million km2 with
these requirements
Total 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
provided the crucial
piece of evidence for
groundwater flow as
the source of the
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.,
Q
dT
K
dz
n
zi Q
Ki
Thermostratigraphy is the application of Fourier’s law of heat
conduction to calculate temperature at depth
T ( z)  T0  
i 1
dT
Q
K
dZ
Q
dT
K
dz
Determine Q from equilibrium T-z and K.
Assume Q is constant, K and dz are known
n
Zi
T ( z)  T0   Q
i 1 Ki
Estimate geothermal energy in
ND and SD
Colors are temperature, contours are depth (m), lines are county boundaries
BHT’s and Observations
Although BHT data are useful, they often
do not indicate actual temperatures at
depth.
The example from the Williston Basin is
typical.
The energy resource in
Joules is calculated by
qr = ρcvad(t-tref)
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
the Williston Basin
Coal ~ 118 EJ
Geothermal ~23 EJ
Oil ~ 20 EJ
Summary
Normal continental heat flow and subsurface temperatures
characterize most of the region.
Thermal blanketing effect of shales and heat advection in
regional groundwater flow systems cause regional thermal
anomalies.
Heat flow, thermal properties, and stratigraphy can be used to
determine subsurface temperatures with good accuracy.
Bottom hole temperatures and equilibrium temperatures may
differ.
Temperatures of 180 °C can be found in the deeper regions of
the Williston Basin and temperatures greater than 90 °C occur
widely in the basin.
In general, the recoverable stratabound geothermal resource in
the region exceeds the energy that could be recovered from oil.
Philosophical Questions
How long will oil last?
When does the world cross the threshold
for disastrous climate change?
What can the scientific community do?
North 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