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Geologic Sequestration: the Big Picture Estimation of Storage Capacity or How Big is Big Enough. Susan Hovorka, Srivatsan Lakshminarasimhan, JP Nicot Gulf Coast Carbon Center Bureau of Economic Geology Jackson School of Geosciences The University of Texas at Austin. - PowerPoint PPT Presentation
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Geologic Sequestration: the Big Picture
Estimation of Storage Capacity or How Big is Big Enough
Susan Hovorka, Srivatsan Lakshminarasimhan, JP NicotGulf Coast Carbon Center
Bureau of Economic GeologyJackson School of GeosciencesThe University of Texas at Austin
Presented to TXU Carbon Management ProgramIAP for CO2 Capture by Aqueous Absorption Semi-annual meeting,
Pittsburg, May 7, 2007
Large Volumes in the Subsurface NETL National Atlas Estimate
Space for 1,014 to 3,370 109 metric tons of CO2
Saline Aquifers Coal
156 - 183109 metric tons of CO2
92 109 metric tons of CO2
Oil and gas reservoirs
http://www.netl.doe.gov/publications/carbon_seq/atlas/index.html
Amount of CO2 to be sequestered
• 7 x 109 T/year US emissions anthropogenic CO2
• If spread evenly over US as CO2:3 cm/year at @STP
0.04 mm/year at reservoir conditions
Sources dot size proportional to emissions
Sinks color proportional to thickness
3.9 shown here
Options for Estimating Capacity
• Volumetric approach: Total pore volume x Efficiency factor (E)– Free CO2 volume in structural and stratigraphic traps– Trapped CO2 residual phase
• Volume dissolved• Volume that can be stored beneath an area
constrained by surface uses or by other unacceptable risks – well fields, faults
• Pressure limits as a limit on capacity• Displaced water as a limit on capacity
Vol
umet
ricR
isk-
base
d
Volumetric Approach
• How much will go in?– Volumetric
approach – current state of art
– A focus on the two phase region: where is the CO2?
Risk or Consequences Approach to Capacity
• How much will go in before unacceptable consequence occurs?
Fluid Displacement as a Limit on Capacity
• Rate of injection limited by displacement of one fluid by another
• Unacceptable displacement of brine
Total Pore Volume
• Total pore volume = volume of fluids presently in the rock = porosity x thickness x area.
• Not all volume is usable:– Residual water– Minimum permeability cut off– Sweep efficiency
• bypassing and buoyancy
Heterogeneity – Dominant Control on Volumetrics
Structural closure
3-D SeismicStratal Slice
Ambrose (2000) 1000 ft
Reservoir heterogeneity – more important in injection than
production
Cornelius ReservoirMarkham No.
Bay City No. field
Tyler andAmbrose (1986)
Stacked Closure
Higher volumessummed though multiple
zones
Efficiency in Terms of Use of Pore Volume – by-passed volume
Tom Daley LBNL
CO2 Saturation Observed with Cross-well Seismic Tomography at Frio
By-passed volume
Hypothesis Capacity is Related To Heterogeneity
Ca
pac
ity
Heterogeneity
Seal
Low heterogeneity – dominated by buoyancy
Seal
High heterogeneity-poor injectivity
Seal
Just right heterogeneityBaffling maximizes capacity
Options for Estimating Capacity
• Volumetric approach: Total pore volume x Efficiency factor (E)– Free CO2 volume in structural and stratigraphic traps– Trapped CO2 residual phase
• Volume dissolved• Volume that can be stored beneath an area
constrained by surface uses or by other unacceptable risks – well fields, faults
• Pressure limits as a limit on capacity• Displaced water as a limit on capacity
Capacity: Dissolution of CO2 into Brine –
Volumetrically a big unknown
1yr
5 yr
30 yr
40 yr
130 yr
330 yr
930 yr
1330 yr
2330 yr
Jonathan Ennis-King, CO2CRCJonathan Ennis-King, CSRIO
Rapid Dissolution of CO2 in Field Test – a significant factor in
reducing plume size Frio CO2 injection (Oct. 4-7/04)
5.5
6.0
6.5
7.0
4-Oct-04 5-Oct-04 6-Oct-04 7-Oct-04 8-Oct-04
Time
pH
1
10
100
1000
10000
Fe
(mg
/L)
pH
Fe
Yousif Kahraka USGS
Within 2 days, CO2 has dissolved into brine and pH falls, dissolving Fe and Mn
Options for Estimating Capacity
• Volumetric approach: Total pore volume x Efficiency factor (E)– Free CO2 volume in structural and stratigraphic traps– Trapped CO2 residual phase
• Volume dissolved• Volume that can be stored beneath an area
constrained by surface uses or by other unacceptable risks – well fields, faults
• Pressure limits as a limit on capacity• Displaced water as a limit on capacity
Capacity in a Geographically limited area
1-45-10
10-30
>30
Wells perSq km
Role of Risk: Traps available you assume faults sealing and/or well completions acceptable
Structural closure
Do Not Need Structure to Limit Plume Size – Role of Kv/Kh
Seal
Kv <<<Kh
Weak layering allowsrapid vertical migration=
Large spread beneath seal
Seal
Kv <Kh
Effective horizontal baffling layers limitvertical rise – avoid spread below
seal
Kh= Horizontal permeability Kh = vertical permeability. Related to rock fabric,Interpreted from sedimentary depositional environment
Options for Estimating Capacity
• Volumetric approach: Total pore volume x Efficiency factor (E)– Free CO2 volume in structural and stratigraphic traps– Trapped CO2 residual phase
• Volume dissolved• Volume that can be stored beneath an area
constrained by surface uses or by other unacceptable risks – well fields, faults
• Pressure limits as a limit on capacity• Displaced water as a limit on capacity
Nearly Closed Volume – Maximum Capacity May be Pressure Determined
Injection Pressure and Depth
• Maximum injection pressure must be less than fracture pressure
• Fracture pressure estimated to linearly increase with depth of formation
• Volume injected below fracture pressure increases with depth
Maximum CO2 injected (Vi) for Given Pore Volume (Vp)
• Closed domain at several porosities and several different sizes leading to a range of brine-filed volumes Homogeneous geological formation, dimensions 10,000 ft x 10,000 ft x 1000 ft, and permeability 10 md, depth 7000 ft. Maximum pressure set at 75% lithostatic.
10% porosity
20% porosity
30% porosity
Effect of Depth of formation
• Effect of the depth of formation almost entirely due to that of injection pressure
Effect of pore volume (contd)
• Best fit over entire data suggest linear (blue) scaling • Ratio of injected to pore volume is about 1.5 %
Vi = 0.01481 Vp
Options for Estimating Capacity
• Volumetric approach: Total pore volume x Efficiency factor (E)– Free CO2 volume in structural and stratigraphic traps– Trapped CO2 residual phase
• Volume dissolved• Volume that can be stored beneath an area
constrained by surface uses or by other unacceptable risks – well fields, faults
• Pressure limits as a limit on capacity• Displaced water as a limit on capacity
Open Hydrologic System
Fluid Displacement From an Open Hydrologic System
0
100
200
300
400
500
600
700
800
0 250 500 750 1000
Time from Start of Injection (years)
To
tal W
ate
r F
lux
(M
m3 /y
r)
0
100
200
300
400
500
Inje
cti
on
Ra
te (
Mt
CO
2/y
r)
Injection rate
Total water flux at 30 km
Total water flux at 100 km
Output of an analytical model. Total means across the boundaries Vb1 and Vb2. Note: vertical axes are approximately equivalent (500 tons of CO2 is 500 t / 0.6 t/ m3 = 833 m3 of displaced water)
Carrizo-Wilcox System in Central Texas
From Dutton et al., 2003
SENW
Lee Co. Fayette Co. Colorado Co.
Youngerformat ions
Older formations
Base of potable water
Topgeopressured
zone
Faults
Faults
Ground surface
Carrizo
0
-2,000
-4,000
-6,000
-8,000
-10,000
-12,000
-14,000 Vertica l scale greatly exaggerated
0
0
40 mi
40 km
Calvert Bluff
Simsboro
Hooper
College StationWell Field
CO2 Injection
Fate of a Pressure Pulse in a Confined Aquifer
0
50
100
150
200
250
300
350
400
450
500
2000 2010 2020 2030 2040 2050
Calendat Year
Pro
du
ced
/In
ject
ed V
olu
me
(mil
lio
n m
3)
All Pumping
Pumping from Simsboro (L5)
CO2 Injection
Year 2000heads
Year 2050heads
Conclusions• Volumetric approach: DOE assessment shows
more than adequate space– Free CO2 volume in structural and stratigraphic traps– Trapped CO2 residual phase
• Volume dissolved – Significance and rate uncertain
• Volume that can be stored beneath an area constrained by surface uses or by other unacceptable risks - What are key risks?
• Pressure limits as a limit on capacity – Similar volume to that used in volumetric approach 1.5 % of pore volume useful, increases with depth
• Displaced water as a limit on capacity – minor in large basins