is there really enough space to “put it back”? capacity estimation for geologic storage of co 2...
TRANSCRIPT
Is there really enough space to “put it back”?
Capacity Estimation for Geologic Storage of CO2
Susan Hovorka, Srivatsan Lakshminarasimhan, JP NicotGulf Coast Carbon Center
Bureau of Economic GeologyJackson School of GeosciencesThe University of Texas at Austin
Amount of CO2 to be sequestered
• 7 x 109T/year US emissions from stationary sources
• If spread evenly over US:30 cm/year at @STP
0.4 mm/year at reservoir conditions
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Sources dot size proportional to emissions
Sinks color proportional to thickness
… and collect data on areal extent,thickness, porosity, and permeabilitythat permit simple estimates of storage capacity for CO2
Assessing CO2 Storage Capacity In Brine-bearing Formations
Identify a porous and permeable rock volume in the subsurface
…That is below underground sources of drinking water
…and isolated from them and from escape to the atmosphere by one or more seals
If preceding steps are favorable, proceed to additional steps, includingmatching to sources, estimating cost, permanence, and risk/uncertainly
How much?
Options for Estimating Capacity
• Total pore volume x Efficiency factor (E)– Volume in structural and stratigraphic traps– solubility trapped– residual phase
• 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 (Vatsan)• Displaced water as a limit on capacity (JP)
What do people want to know when they ask for storage capacity?
• How much will go in?– Volumetric
approach – current state of art
– A focus on the two phase region: where is the CO2?
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
Reservoir Model Estimate Sweep Efficiency, Reservoir Volumetrics
• Model reservoir parameters as for hydrocarbons– Sand body
architecture– Petrophysics –
porosity, residual water saturation
– Input heterogeneity model sweep efficiency
• Unique elements– Rapid charge– Outside of trap– dissolution
PorosityFault planes
Sand/shale sequences
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
Capacity: Dissolution of CO2 into Brine –
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
HypothesisC
ap
acit
y
Heterogeneity
Seal
Low heterogeneity – dominated by buoyancy
Seal
High heterogeneity-poor injectivity
Seal
Just right heterogeneityBaffling maximizes capacity
Risk or Consequences Approach to Capacity
• How much will go in before unacceptable consequence occurs?
Capacity in a Geographically limited area
1-4
5-10
Well density
Closed Volume – Maximum Capacity May be Pressure Determined
Injection capacity
• Depth of formation• Injection pressure• Pore volume of formation
– Size of formation– Porosity
• Pressure gradientL
H
W
D
Vp = ΦV = ΦLWH
Injection Pressure and Depth
• Maximum injection pressure must be less than fracture pressure
• Fracture pressure estimated to linearly increase with depth of formation
• Fracture pressure in geo-pressure zone may increase non-linearly
Effect of Depth of formation
• Effect of the depth of formation almost entirely due to that of injection pressure
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 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
Effect of pressure gradient
• Ratio of injected to pore volume scales almost linearly with pressure gradient
• Scope for theory-based correlatory approach to estimating capacity
Fluid Displacement as a Limit on Capacity
• Rate of injection limited by displacement of one fluid by another
• Unacceptable displacement of brine
Open Hydrologic System
Confined/Unconfined AquifersSpecific Storage - Storativity
• Unconfined (or water table) aquifer: dewatering pore space
• Confined (artesian) aquifer: rock matrix and water volume expansion
• Specific storage is a measure of how much water can be released from storage
• All we know about production can be applied to injection (~)
Domenico and Schwartz (1990)
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
HydraulicConductivity
(ft/day)
Storativity[-]
Year 2000heads
Year 2050heads
Outcrop is ImpactedYear 2050 drawdowns
ConclusionsLooking at large volumes of CO2 storage in pore space previously filled only with brine, we examined four combinations of boundary condition and risk avoided: Structural or stratigraphic trap: CO2 spills out
of trap Open trap/volume: CO2 escapes from
volume Hydrologically closed basin: mechanical or
capillary entry pressure of seal is exceeded Hydrologically open basin: unacceptable
displacement of brine
Hydrograph from J-17 Well, Ft. Sam Houston
Graph shows water level oscillations from earthquake off west coast of Sumatra
9.0 magnitude on Richter Scale
Groundwater levels oscillated for 1 ½ hours with total amplitude of 2.6 feet
Quake occurred at 00:58 (UTC) on December 26
Courtesy of Geary Schindel Edwards Aquifer Authority