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Geologic Storage Formation
Classiications: Understanding Its
Importance and Impacts on CCS
Opportunities in the United States
September 2010
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Disclaimer
This report was prepared as an account o work sponsored by an agency o the United States
Government. Neither the United States Government nor any agency thereo, nor any o their
employees, makes any warranty, express or implied, or assumes any legal liability or responsibility
or the accuracy, completeness, or useulness o any inormation, apparatus, product, or process
disclosed, or represents that its use would not inringe privately owned rights. Reerence therein
to any speciic commercial product, process, or service by trade name, trademark, manuacturer, or
otherwise does not necessarily constitute or imply its endorsement, recommendation, or avoring by
the United States Government or any agency thereo. The views and opinions o authors expressed
therein do not necessarily state or relect those o the United States Government or any agency
thereo.
Cover PhotosCredits for images shown on the cover arenoted with the corresponding figures within this document.
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Geologic Storage Formation Classiications:
Understanding Its Importance and Impacts on CCS
Opportunities in the United States
September 2010
National Energy Technology Laboratory
www.netl.doe.gov
DOE/NETL-2010/1420
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Table of Contents
Executive Summary ____________________________________________________________________________ 10
1.0 Introduction and Background Geology_________________________________________________________ 11
1.1 Geologic Background_______________________________________________________________________________ 131.2 Igneous Rocks _____________________________________________________________________________________ 14
1.3 Metamorphic Rocks ________________________________________________________________________________ 16
1.4 Sedimentary Rocks_________________________________________________________________________________ 16
2.0 Characteristics of Storage Reservoirs and Confining Units_________________________________________ 20
2.1 Reservoir Properties _______________________________________________________________________________20
2.2 Sealing and Trapping Mechanisms ___________________________________________________________________21
3.0 Depositional Environments __________________________________________________________________ 24
3.1 Deltaic Reservoir Properties_________________________________________________________________________28
Deltaic Depositional Environment _______________________________________________________________________28
3.2 Carbonate Reservoir and Ree Reservoir Properties ____________________________________________________32
Carbonate Depositional Systems ________________________________________________________________________32
Reef Depositional System ______________________________________________________________________________33
3.3 Turbidites Reservoir Properties ______________________________________________________________________34
Turbidite Depositional System___________________________________________________________________________34
3.4 Strandplain Reservoir Properties ____________________________________________________________________36
Strandplain Depositional System ________________________________________________________________________36
Barrier Island Depositional System _______________________________________________________________________373.5 Alluvial and Fluvial Fan Reservoir Properties __________________________________________________________38
Alluvial Depositional Systems ___________________________________________________________________________38
Fluvial Depositional Systems____________________________________________________________________________38
3.6 Eolian Reservoir Properties _________________________________________________________________________40
Eolian Depositional Systems ____________________________________________________________________________40
3.7 Lacustrine Reservoir Properties______________________________________________________________________41
Lacustrine Depositional Systems_________________________________________________________________________41
Evaporites Depositional System _________________________________________________________________________42
3.8 Basalt Reservoir Properties _________________________________________________________________________42
4.0 The Road to Commercialization_______________________________________________________________ 44
References ____________________________________________________________________________________ 48
Section 1 References __________________________________________________________________________________48
Sections 2 and 3 References ___________________________________________________________________________48
Section 4 References __________________________________________________________________________________53
Table of Contents
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List of Figures
Figure 1-1. Schematic o CO2
rom a Thermoelectric Power Plant and Reinery being
stored in Various Geologic Formations. ___________________________________________________ 12
Figure 1-2. Formation and Distribution o Igneous Rock in the Earths Crust. _______________________________ 14
Figure 1-3. Cut and polished granite showing pink and white quartz crystals and black mica. _________________ 15
Figure 1-4. Basalt. ______________________________________________________________________________ 15
Figure 1-5. Distribution o Known Basalt Formations in the United States and Canada
Investigated by NETL. _________________________________________________________________ 15
Figure 1-6. Slate, a ine-grained, oliated, metamorphic rock that was ormerly shale. _______________________ 16
Figure 1-7. Schist a metamorphic rock where heat and pressure have elongated individual minerals. __________ 16
Figure 1-8. Environments or Weathering and Deposition o Rocks that can ProduceSedimentary Clastic Deposits.___________________________________________________________ 17
Figure 1-9. Environments or Formation o Carbonate Rocks. ___________________________________________ 17
Figure 1-10. Cut sandstone core rom Eolian deposit showing banding, ___________________________________ 17
Figure 1-11. Close-up o coral pink sandstone rom Eolian ormation, _____________________________________ 17
Figure 1-12. Course sandstone showing bedding planes. _______________________________________________ 18
Figure 1-13. Shale with parallel bands or layers. _______________________________________________________ 18
Figure 1-14. Etched limestone showing shells and calcareous debris rom Kope Formation, Ohio. ______________ 18
Figure 1-15. Map o Oil and Gas Fields Superimposed on Saline Basins o North America. _____________________ 19
Figure 1-16. Distribution o Known Coal Basins Investigated by NETL. _____________________________________ 19
Figure 2-1. Porosity in Rocks and Rock Permeability. __________________________________________________ 20
Figure 2-2. Microscopic Schematic o Rock Porosity and Permeability. ____________________________________ 21
Figure 2-3. Shale, sand, and anhydrite core rom Colorado and well-sorted beach sand. _____________________ 22
Figure 2-4. Capillary trapping o CO2. ______________________________________________________________ 23
Figure 2-5. Structural traps: (let) Anticline, (center) Fault, (right) Salt Dome as trap. _________________________ 23
Figure 3-1. Components o a Deltaic System. ________________________________________________________ 28
Figure 3-2. Mississippi River Delta, United States, Lobe Development over the Last 5,000 years. _______________ 28
Figure 3-3. Mississippi River Delta, United States. A Recently Developed Elongated Shaped
Delta that is River-Dominated. __________________________________________________________ 28
Figure 3-4. Nile River Delta, Egypt. A Lobe Shaped Delta that is Wave-Dominated. __________________________ 29
List of Figures
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Figure 3-5. Rhone River, France. A Wave-Dominated Elongated Delta.. ___________________________________ 29
Figure 3-6. Ganges/Brahmaputra River Delta, Bangladesh. _____________________________________________ 29
Figure 3-7. As Time, Heat and Pressure Increase during Coaliication, the Lignite Changes into
Bituminous and Finally Anthracite Coal. ___________________________________________________ 30
Figure 3-8. Structure o coal and the cleat system within. ______________________________________________ 31
Figure 3-9. Carbonate Depositional System. An idealized block diagram o carbonate depositional
environments based on Pennsylvanian carbonates in southeastern Utah. _______________________ 32
Figure 3-10. Groundwater zones. __________________________________________________________________ 33
Figure 3-11. Pinnacle Ree Development in Alberta. ___________________________________________________ 34
Figure 3-12. A. Coarse-grained, Sand-rich Turbidite System and B. Fine-grained, Mud-rich
Turbidite System. _____________________________________________________________________ 35
Figure 3-13. Strandplain Deposit along the South Carolina Coast. ________________________________________ 36
Figure 3-14. Strandplain near the mouth o the Kugaryuak River, Coronation Gul, Southwest
Kitikmeot Region, Nunavut, Canada. _____________________________________________________ 36
Figure 3-15. Barrier Island with Beach and Back Dune Areas. ____________________________________________ 37
Figure 3-16. Barrier Island along the Texas Coast. _____________________________________________________ 37
Figure 3-17. Badwater Fan, Death Valley, Caliornia. ___________________________________________________ 38
Figure 3-18. Large alluvial an between the Kunlun and Altun mountains, XinJiang Province, China. ____________ 38
Figure 3-19. Google Earth Image o Bhramapura River System, Bangladesh showing Braided
stream system depositing sediment rom the Himalayan Mountains. ___________________________ 39
Figure 3-20. Closer Image o Braided River Fluvial Depositional System. ___________________________________ 39
Figure 3-21. Braided River Flowing on a previously Glaciated Flat near Peyto Lake, Ban
National Park, Canadian Rockies, Alberta, Canada. __________________________________________ 39
Figure 3-22. Block diagram o a meandering stream (A) and braided stream (B) showing lateral
migration o channel and point bar sequence and environmental relationships. __________________ 40
Figure 3-23. The Namib Desert Dune Ridge System. ___________________________________________________ 41
Figure 3-24. A Lacustrine Formation Being Deposited in a Hydrologically Closed System. _____________________ 41
Figure 3-25. Evaporite Deposits being ormed on the Caribbean Island o Bonaire. __________________________ 42
Figure 3-26. Major Internal Features o a Columbia River Basalt Group (North America) Lava Flow. ______________ 43
Figure 4-1. Matrix o NETL CO2
Geosequestration Projects and Depositional Environments. __________________ 47
List of Figures
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List of Tables
Table 3-1. Reservoir Depositional Classiication Schematic. ___________________________________________ 25
Table 3-2. Characteristics o Depositional Reservoirs. ________________________________________________ 26
Table 4-1. CO2
Geosequestration Projects with Lithology and Geologic Classiication. _____________________ 44
List of Tables
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List of Acronyms and Abbreviations
Acronym/Abbreviation Defnition
ARRA ________________________ American Recovery and Reinvestment Act o 2009
Big Sky_______________________ Big Sky Carbon Sequestration Partnership
Btu__________________________ British thermal unit
CBM _________________________ Coalbed Methane
CCS _________________________ Carbon Capture and Storage
CH4
_________________________ Methane
CO2__________________________ Carbon Dioxide
CaCO3
_______________________ Calcium Carbonate
DOE _________________________ U.S. Department o Energy
ECBM ________________________ Enhanced Coalbed Methane
EOR _________________________ Enhanced Oil Recovery
EPA _________________________ U.S. Environmental Protection Agency
GHG _________________________ Greenhouse Gas
GIS __________________________ Geographic Inormation Systems
HFC _________________________ Hydrofuorocarbon
LIP __________________________ Large Igneous Provinces
MGSC________________________ Midwest Geological Sequestration Consortium
MORB _______________________ Mid-Ocean Ridge Basalts
MRCSP _______________________ Midwest Regional Carbon Sequestration Partnership
MWh ________________________ Megawatt Hour(s)N
2O _________________________ Nitrous Oxide
NRDC ________________________ Natural Resources Deense Council
NETL ________________________ National Energy Technology Laboratory
OIB __________________________ Ocean Island Basalts
OOIP ________________________ Original Oil in Place
PCOR ________________________ Plains CO2
Reduction Partnership
ppm _________________________ parts per million
RCSP ________________________ Regional Carbon Sequestration Partnership(s)
RD&D ________________________ Research, Design, and DemonstrationSECARB ______________________ Southeast Regional Carbon Sequestration Partnership
SWP _________________________ Southwest Regional Partnership on Carbon Sequestration
TDS _________________________ Total Dissolved Solids
USGS ________________________ U.S. Geological Survey
WAG ________________________ Water Alternating Gas
WESTCARB ___________________ West Coast Regional Carbon Sequestration Partnership
List of Acronyms and Abbreviations
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Matrix of Field Activities in Different Reservoir Classes
High Potential Reservoirs Medium Potential Reservoirs
Lower orUnknownPotential
Reservoirs
Large Scale FieldTests
1 1 3 1
Small Scale Field Tests 3 2 4 1 2 2 5 1
Site Characterization 1 8 6 3 3 2 2 1
Deltaic
ShelClastic
ShelCarbonate
Strandp
lain
Ree
FluvialDeltaic
Eo
lian
Fluvial&Alu
vial
Turbidite
Coal
Basalt(LIP)
Notes:
The number in the cell is the number of investigations per depositional environment.
Large Scale Field Tests Injection of over 1,000,000 tons of CO2.
Small Scale Field Tests Injection of less than 500,000 tons of CO2.
Site Characterization Characterize the subsurface at a location with the potential to inject at least 30,000,000 tons of CO2.
Reservoir potentials were inferred from petroleum industry data and field data from the sequestration program.
Executive Summary
A need exists or urther research on carbon storage
technologies to capture and store carbon dioxide (CO2)
rom stationary sources that would otherwise be emitted
to the atmosphere. Carbon capture and storage (CCS)technologies have the potential to be a key technology
or reducing CO2
emissions and mitigating global climate
change.
Deploying these technologies on a commercial-scale
will require geologic storage ormations capable o:
(1) storing large volumes o CO2; (2) receiving CO
2at an
eicient and economic rate o injection; and (3) saely
retaining CO2
over extended periods. Eleven major
types o depositional environments, each having their
own unique opportunities and challenges, are being
considered by the U.S. Department o Energy (DOE) orCO
2storage. The dierent classes o reservoirs reviewed
in this study include: deltaic, coal/shale, luvial, alluvial,
strandplain, turbidite, eolian, lacustrine, clastic shel,
carbonate shallow shel, and ree. Basaltic interlow
zones are also being considered as potential reservoirs.
DOE has recently completed this study which investigated
the geology, geologic reservoir properties and conining
units, and geologic depositional systems o potential
reservoirs and how enhanced oil recovery (EOR) and
coalbed methane (CBM) are currently utilizing CO2. The
study looked at the classes o geologic ormations, and
their potential to serve as CO2
reservoirs, distribution,
and potential volumes.
This study discussed the eorts that DOE is supporting to
characterize and test small- and large-scale CO2
injection
into these dierent classes or reservoirs. These tests are
important to better understand the directional tendencies
imposed by the depositional environment that may
inluence how luids low within these systems today, and
how CO2
in geologic storage would be anticipated to low
in the uture. Although diagenesis has modiied luid low
paths during the intervening millions o years since they
were deposited, the basic architectural ramework created
during deposition remains. Geologic processes that are
working today also existed when the sediments wereinitially deposited. Analysis o modern day depositional
analogs and evaluation o core, outcrops, and well logs
rom ancient subsurace ormations give an indication o
how ormations were deposited and how luid low within
the ormation is anticipated to low.
The distribution o the dierent depositional environments
that NETL is investigating is presented below. The ield
activities are in various stages o investigation with
Executive Summary
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some completed and others just underway. Additional
investigations, including small- and large-scale injection
tests, will be needed to be completed on all o the dierent
depositional environments. This will provide the inormation
on the behavior and low o CO2
in the dierent reservoirs.
Reerring to the Distribution o Field Activities or CCS/
Geologic Storage matrix, characterization has not been
completed or a shel clastic, ree, and coal environments.
Small-scale injection tests (1,000,000 tons o CO2) have not been perormed on
deltaic, strandplain, shel carbonate, eolian, turbidite,
basalt Large Igneous Providences (LIP), and coal. Three
highly experimental reservoirs that are not included on
the matrix because they have not been investigated are
ractured shales, Mid Oceanic Ridge Basalts (MORB), andoshore turbidites.
Understanding the impacts o dierent reservoir
depositional classes on storage o CO2will support DOEs
eorts to develop the knowledge and tools necessary or
uture commercialization o carbon storage technologies
throughout the United States.
1.0 Introduction and Background
Geology
Geologic storage o CO2
is a complex issue involving a
number o variables, including capturing the greenhouse
gas (GHG) emissions rom stationary sources, developing
the inrastructure to transport the CO2, and selecting
underground reservoirs or CO2
storage. This desk
reerence is based in part on a DOE report, titled,
Depositional Systems or CO2
Geosequestration (DOE/
NETL-2009/1334 Olsen et al., 2009).
This desk reerence is intended to:
Assist with an understanding of basic geological
principles and terminology associated with potential
CO2
geologic storage in ormations.
Show the importance of geologic depositional
systems in determining the internal architecture o
such ormations, thus making it possible to predict
the behavior o the injected CO2.
Establish the importance of using the geologica
depositional system to assess existing and uture
research, design, and demonstration (RD&D) needs
related to storing CO2
in dierent depositiona
environments.
A goal o DOEs Research and Development (R&D)
program in carbon storage is to classiy the
depositional environments o various ormations that
are known to have excellent reservoir properties and
are amenable to geologic CO2
storage. Using lessons
learned rom the behavior o CO2
in reservoirs rom
previous geologic investigations and their known
depositional environments is important in developing
an understanding or similar depositional environments
being considered or storage, and predicting the
expected behavior o CO2
within these proposed
reservoirs without having to duplicate the time, eortand unds that were expended on the original projects
This is being accomplished through the implementation
o 28 CO2
injection ield projects in collaboration with
the Regional Carbon Sequestration Partnership (RCSP)
Initiative and 10 American Recovery and Reinvestment
Act o 2009 (Recovery Act) projects that are ocused
on the characterization o geologic ormation as sites
or possible commercial carbon capture and storage
(CCS) development. DOE has completed this review o
geologic depositional classiication system to bette
understand how the ield work being conducted
today ulills the need to test these dierent classes o
depositional systems and determine what uture R&D
projects are still needed.
According to the U.S. Environmental Protection Agency
(EPA), total GHG emissions were estimated at 7,100 million
metric tons (7,800 million tons) CO2
equivalent in the
United States in 2006. This estimate included CO
emissions, as well as other GHGs, such as methane (CH4)
nitrous oxide (N2O), and hydroluorocarbons (HFCs)
Annual GHG emissions rom ossil uel combustion
primarily CO2, were estimated at 5,600 million metrictons (6,200 million tons), with 3,800 million metric tons
(4,200 million tons) rom stationary sources. Carbon
dioxide stationary sources are largely related to powe
production (Carbon Sequestration Atlas o the United
States and Canada, 2008).
Carbon dioxide is a byproduct o the oxidation o
hydrocarbons and is generated rom the natura
decomposition o organic material, accelerated oxidation
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(burning o ossil hydrocarbons or biomass), and
geologic sources (e.g., volcanoes). Carbon dioxide is also
the product o decomposition o rocks, like limestone
(calcium carbonate [CaCO3]), in cement manuacturing.
Geologic storage o CO2, in underground ormations
as part o CCS, is one possible long-term/permanentstorage solution or the reduction o anthropogenic CO2
rom the atmosphere. This approach involves the capture
and stabilization o large volumes o CO2
in underground
carbon sinks (storage locations) (Baines and Worden,
2004). Some variants o these underground sinks are
shown in Figure 1-1, including the surace inrastructure
and the dierent types o reservoirs that are available.
Prior to implementing CCS, site developers and owners
will utilize the results rom existing storage projects to
develop risk assessments and business models or their
individual acilities. The existing data, developed byDOEs National Energy Technology Laboratory (NETL)
and others, will allow an individual site to be evaluated to
better deine the costs or geologic storage, determine
the type and quality o geologic sinks that are available
in the region, and evaluate the type and quality o
transportation inrastructure that is required.
NETL has pioneered and developed practices or the
evaluation, installation, and operation o CCS acilities.
These practices were developed to both help reduce the
costs o implementing CCS and to protect human health
and the environment rom adverse eects o CO2. CCS
will allow the viable use o coal-ired power plants whilehelping to stabilize climate changing CO2
emissions. Coal
uels the majority o power generation capacity in the
United States and in many other areas o the world. Coal
is an abundant domestic energy resource and the primary
source o baseload power generation in the United
States, generating 1,986 million megawatt hours (MWh) in
2008. At the 2008 rate o consumption, coal could meet
the United States needs or more than 234 years. Since
1976, coal has been the least expensive ossil uel used to
generate electricity when measured based on the cost
per British thermal unit (Btu [a unit o energy content]).
Although the cost o generating electricity rom coalhas increased, it is still lower than generating electricity
rom either natural gas or petroleum in most areas. The
number o coal-ired power plants is expected to increase
in the uture. Existing acilities can be retroitted with CCS
technology to allow or the continued use o coal without
emitting CO2
emissions into the atmosphere.
Figure 1-1. Schematic of CO2
from a Thermoelectric Power Plant and Refinery being stored in Various Geologic Formations.
(Adapted from original figure, courtesy of Dan Magee, Alberta Energy Utilities Board, Alberta Geologic Survey, 2008.)
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In the oil and natural gas industry, the injection o CO2
underground has been occurring or approximately our
decades. As discussed later in this document, CO2
is used
to extract previously unrecoverable oil and increase oil
and gas production. This has resulted in millions o dollars
o additional revenue to local and state economies. Inthis application, CO2
is considered a commodity.
Although it is also important to consider non-geologic
actors or successul large-scale deployment o CCS
technologies, including geographic location (source to
sink matching), economic actors, public acceptance,
and the capture portion o CCS, this report ocuses on
evaluating the depositional environment o potential
geologic reservoirs or uture CCS projects.
1.1 Geologic Background
There are three major types o rock that uture
developers o CCS projects might target or storage
ormations, including: igneous, metamorphic, and
sedimentary. Each major type o rocks was ormed
under dierent conditions, and their potential or CO2
storage varies based on the necessary criteria o:
Capacity,which is based on the porosity or openings
within a rock, oten called pore space.
Injectivity,which is dependent on the permeability
or the relative ease with which a luid or gas can
move within the pore space(s) o a rock.
Integrity, or the ability to conine a luid or gas
within a geologic unit, is o primary importance,
because without impermeable seals, luids will take
the path o least resistance and move to a lower-
pressure area, including the surace.
The answers to questions concerning capacity,
injectivity, and integrity can be learned, in part, by
reservoir characterization o the ormations in the
area o the proposed geologic storage site. Reservoir
characterization is an evolving science that integrates
many dierent scientiic disciplines (geology, geophysics,
mathematical modeling, computational science, seismic
interpretation, well log and core analysis, etc.) in order to
build a conceptual model o a ormation. The decision
to select a particular geologic unit or geologic storage
usually depends on having a detailed understanding o
the reservoir characteristics and the behavior and ate o
the injected luids and their impact on the geologic strata
receiving the luids. Critical actors include: economic
analysis o the location o the site, the distance rom the
CO2 source to the site, the depth o the reservoir (whichinluences drilling and injectivity o CO2), the volume o
CO2
that the site can contain, the trapping mechanism
and sealing capacity, and the ultimate ate o the
What is Supercritical CO2?
Carbon dioxide can be stored in either a gas phase or in
a liquid (supercritical) phase. The volume to store gas in
a gas phase is huge compared to storage in the liquid
(supercritical) phase. To get CO2
into a supercritical phase
requires that the gas be compressed.
I the CO2
is injected into the reservoir as a liquid the
area near the well is cooled but at some distance rom
the wellbore the liquid takes on the temperature o the
reservoir. CO2
injected at depths below approximately
800 meters (2,600 eet) is at a pressure and temperature
that will allow the CO2
to remain as a supercritical luid.
By maintaining the pressure as presented in the igure
below, the volume required or geologic storage is a
raction o what is required or lower pressures.
Illustration of Effect of Pressure on CO2. (Image courtesy of
CO2CRC www.co2crc.com.au/imagelibrary/)
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stored CO2. Many o these issues will be aected by the
dierent classes o reservoirs that are being targeted or
injection.
Time plays an important role in the ormation o reservoirs,
because rocks have been ormed, eroded, and reormedmany times in the history o the Earth beore reaching the
present coniguration o continents and oceans. Reservoirs
are strongly aected by these changes. Processes such as
compaction o the rock, dissolving and enlarging pore
spaces, or illing these pore spaces with sediments or new
minerals rom solution alters the amount o porosity and
permeability o potential CO2
storage reservoirs.
Most CO2
geological storage targets are sedimentary
rocks (clastics and carbonates), where CO2
storage is in
the pore space between grains, which are most oten
illed with undrinkable saline water. Igneous ormations,which cover more o the Earths surace than sedimentary
ormations, oer potentially great geologic storage sites
because o their total volume both on continents and
under the oceans, but are mostly untested. Coalbeds are
a group o rocks that are considered both sedimentary
and metamorphic and have their own unique properties.
The most important storage mechanism or coal is its
preerential ability to adsorb CO2
directly on its surace.
This situation diers rom other sedimentary and igneous
ormations where the CO2
occupies the pore space. It is
anticipated that CO2 will be injected as a supercriticalluid in the majority o reservoirs. To better understand
how these rocks are ormed and their potential or CO2
storage, brie discussions o the dierent rock types are
summarized in the next three sections.
1.2 Igneous Rocks
Igneous rocks (rom the Latin ignis, ire) are ormed by
the solidiication o cooled magma (molten rock). All
rocks on Earth originated rom igneous sources. Igneous
rocks make up approximately 95% o the upper part o
the Earths crust. Elevated planetary temperatures during
the Earths ormation produced widespread melting that
continues today. The melt originates deep within the
Earth and is seen in the crust near active plate boundaries
or hot spots. Igneous rocks have unique compositions,
because the same elements orm dierent minerals
and dierent rock types based on the temperature and
pressure o the magma when they solidiy.
Figure 1-2 shows the ormation and distribution
o igneous rock at divergent plate boundaries and
subduction zones (where convergent plate boundaries
meet). The movement o these dierent plates is
called plate tectonics. The system is powered by heat
convection as hot magma moves upward toward the
Earths crust and then lows out (cools) away rom the
divergent plate boundary. Cooler rock tends to sink and
gets pulled down into large convection cells. The crust
loats on the mantle (83% o Earths volume) o melted
rocks that extends down about 2,900 kilometers.
Figure 1-2. Formation and Distribution of Igneous Rock in the Earths Crust. (Fichter, 2000.)
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There are two types o igneous rocks: intrusive and
extrusive. In particular, extrusive types oer some
unique potential or CO2
storage. Their high porosity
and mineralogy oer opportunities or high volume
storage and reactive chemistry that could convert the
CO2 into solid carbonates and essentially trap the CO2 inthe rocks orever.
IntrusiveIgneousRocks(plutonic) are ormed rom
magma that cools and solidiies within the Earth. The
most common intrusive rocks are granite (Figure 1-3),
which vary considerably in color depending on the
minerals present. These rocks may be ractured and
have low porosity and permeability, making them
unlikely targets as storage ormations.
Extrusive Igneous Rocks (volcanic igneous rock)
are produced when magma exits and cools quicklyoutside o, or near, the Earths surace. The quickcooling means that mineral crystals do not have muchtime to grow, so these rocks have a ine-grained or
Figure 1-5. Distribution of Known Basalt Formations in the United States and Canada
(in yellow) Investigated by NETL (2008).
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Figure 1-3. Cut and polished granite showing pink
and white quartz crystals and black mica.
Figure 1-4. Basalt. (Courtesy of USGS Rock Library.)
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even glassy texture. Hot gas bubbles are oten trappedin quenched lava, orming a bubbly, vesicular textureand lots o porosity. In particular, basalts (Figure 1-4)are extrusive igneous rocks that oer opportunitiesor CO
2storage. Figure 1-5 shows the geographic
extents o basalt ormations in the United States.
1.3 Metamorphic Rocks
Metamorphic rocks are ormed rom pre-existing
rocks (igneous, sedimentary, or other metamorphics).
Metamorphic rocks are created rom these pre-
existing rocks through processes that generate heat
and pressure resulting rom deep burial and tectonic
(mountain building) activity (Figures 1-6 and 1-7). For
the most part, metamorphic rocks are o little interest as
geologic targets or CO2
storage due to their low porosity
(little pore space between sediment grains) and lowpermeability (near zero interconnectivity o these pore
spaces that allows luids to low through the rock).
Figure 1-6. Slate, a fine-grained, foliated, metamorphic rock
that was formerly shale. (Courtesy of USGS Rock Library.)
Figure 1-7. Schist a metamorphic rock where heat and pressure
have elongated individual minerals. Elongated quartz crystals
are white in photo. (Courtesy of USGS Rock Library.)
However, a metamorphic rock that has some potential
or CO2
storage potential is anthracite coal. Anthracite
has progressed through three stages o coaliication.
Anthracite coal is classed as metamorphic rock, based
on the temperatures and pressures required to orm this
dense coal rom soter sedimentary coal. Anthracite isnot an abundant orm o coal and represents a relatively
small opportunity or CO2
storage.
1.4 Sedimentary Rocks
Sedimentary rocks are ormed rom ragments o pre-
existing rocks that are transported and held together
(cemented) through natural agents, such as chemical
precipitation rom solution or secretion by organisms.
Over geologic time, weathering or erosion o rock
ormations at a higher elevation produces sedimentthat is carried by water, wind, ice, and gravity to lower
elevations and deposited as sands and silts intermixed
with organic materials as sedimentary deposits. The
various environments in which this takes place are
depicted in Figure 1-8 or clastic (consisting o ragments)
rocks. A comparable schematic representation o the
depositional environments or carbonates is provided in
Figure 1-9 .
Clastics, like sandstone (Figures 1-10, 1-11, and
1-12) and shale (Figure 1-13), are deposited as
sand, silt, gravels, or with organic materials onbeaches (tidal lats, shels, and barrier islands), in
river channels (luvial), in lagoons and swamps,
in desert dunes (eolian) (Figure 1-11), in lakes
(lacustrine), or as oshore submarine ans (turbidite).
These deposits can orm ans, sand bars, deltas,
braided or meandering streams, or dunes, each
having a distinct depositional pattern and a unique
internal architecture that controls luid low within
the reservoir body (see Figure 1-8). Bituminous coal
is also an important sedimentary rock that oers
opportunities or CO2 storage and enhanced coalbedmethane (ECBM) recovery.
Carbonate rocks (Figure 1-9) are the product o
both biological and chemical systems (e.g., corals
ormed in rees, oyster shell banks, or as chemical
precipitates) (Figure 1-14). They are also classiied
as sedimentary rocks. Carbonate deposition occurs
in seawater and is highly dependent on water
depth and sunlight, which allow organisms to grow.
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Figure 1-8. Environments for Weathering and Deposition of Rocks that can Produce
Sedimentary Clastic Deposits. (Courtesy of Professor L. S. Fichter, 2000.)
Figure 1-9. Environments for Formation of Carbonate Rocks. (Courtesy of Professor
L. S. Fichter, 2000.)
Figure 1-10. Cut sandstone core (cut horizontal) from Eolian
deposit showing banding. (Courtesy of Ken Hammond, USDA
Rock Library.)
Figure 1-11. Close-up of coral pink sandstone from Eolian
formation where sand grains have been rounded and lightly
cemented together. (Courtesy of Professor Mark Wilson.)
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Most corals that are ree orming species live in
shallow water. At shallow water depths, the primary
carbonate orming species are microscopic size,
one-cell plankton. Carbonate sediments ormed
in oshore basins and in oceans are the result o
tiny shells driting down and accumulating as thick
ooze on the sealoor. The ooze is transormed into
carbonate shale or chalk over time. Carbonates also
include a subclass o rocks, called evaporates,
which include salts, gypsum, and anhydrite that are
ormed when saline water evaporates, leaving layers
o dense, low permeability salts that oten orm
seals to other high permeability ormations. Water
has reacted with carbonate rocks in some areas to
create porosity and permeability (solution channels)
making these rocks o interest or CCS.
Both clastic and carbonate rocks possess geologic
storage potential because o the relatively high porosity
and permeability developed during their ormation.
However, the unique changes that occur as sediments
are transormed into todays rock determine the exact
nature and potential o a clastic or carbonate reservoir
or luid low and storage. Changes that occur ollowing
deposition are termed post-deposition or diagenetic
changes and can impact the porosity and permeabilityo the rock and have some impacts on the injectivity,
luid low, and capacity o the ormations. Understanding
these changes and their impacts on storage is critical
to transerring the results o DOEs ield projects to
other portions United States that have similar types o
depositional environments.
Figure 1-14. Etched limestone showing shells and calcareous debris (calcium
carbonate) from Kope Formation, Ohio. (Courtesy of Jim Stuby.)
1 .0 I ntrod u cti on a nd B a ckg rou nd Geol og y
Figure 1-13. Shale with parallel bands or layers. (Courtesy of
USGS Rock Library.)
Figure 1-12. Course sandstone showing bedding planes originally
deposited horizontally. (Courtesy of USGS Rock Library.)
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During the development o the regional
characterization or geologic storage sites,
NETL through its regional carbon sequestration
partners (RCSPs) identiied and examined the
location o potential injection zones in dierent
basins throughout the United States and Canada.Initial resource estimates were calculated or
the primary storage ormations and have been
reported in the 2008 version o the Carbon
Sequestration Atlas o the United States and
Canada. These estimates are reined as NETL and
the RCSPs continue to validate storage potential
in each respective region. Conservative estimates
o storage potential in North America show the
potential or hundreds o years o CO2
storage in
deep geologic ormations bearing saline luids
and oil and gas. These geologic ormations and
reservoirs are made up o the dierent geologicclasses discussed in this report.
These sedimentary ormations contain layers o
porous or ractured rocks that are saturated with
brine, oil, and gas. Brine is a highly saline solution
that contains appreciable amounts o salts that
have either been leached rom the surrounding
rocks or rom sea water that was trapped when
the rock was ormed. The U.S. EPA has determined
that a saline ormation used or CO2
storage must
have at least 10,000 parts per million (ppm) o
total dissolved solids (TDS, - salts), compared to
sea water, which currently has approximately
34,000 ppm o TDS. Most drinking water supply
wells contain a ew hundred ppm or less o TDS.
Any higher concentrations in drinking water
would have an unacceptable, salty taste (Price,
Allen, and Unwin). Oil and gas reservoirs are
oten saline ormations that have proven traps
and seals allowing oil and gas to accumulate in a
trap over millions o years. With the exceptions o
multiple manmade wellbores, there is little reason
to believe that these same ormations would leaki the oil and gas was replaced with CO
2. Many
oil and gas ields containing stacked ormations
(dierent reservoirs) have characteristics that
make them excellent target locations or geologic
storage, including good porosity. The regions
o various sedimentary basins where saline
ormations, oil and gas ields, and unmineable
coal seams that have been assessed or storage
potential are shown in Figures 1-15 and 1-16.
Figure 1-15. Map of Oil and Gas Fields (red) Superimposed on Saline Basins
(blue) of North America. (NATCARB, 2008.)
Figure 1-16. Distribution of Known Coal Basins Investigated by NETL.
(NATCARB, 2008.)
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2.0 Characteristics of Storage
Reservoirs and Confining Units
Reservoir characterization, as applied in this report, is
based on the hypothesis that what is learned rom the
depositional environment o a reservoir can be used todevelop a geological/reservoir model. The model will
describe (in part) the characteristics and perormance
o another reservoir deposited in the same type o
depositional environment. In general, three types/
groups o reservoirs have been historically evaluated or
potential geologic storage o CO2: depleted oil and gas
reservoirs, deep coalbeds unavailable to conventional
mining, and saline ormations. Additionally, research is
being perormed to evaluate the potential or geologic
storage in ractured basalts andshales.These reservoirs
are made up o multiple depositional environments and
have been grouped together based on their reservoir
content and geology.
The characteristics o geologic ormations or reservoirs
that help make them potential geologic storage targets
include: porosity; permeability; adequate volume or
storage; seals; and a trapping mechanism(s) to conine the
CO2or sae, long-term storage. Porosity and permeability
are primarily dependent on the depositional system and
post-depositional processes or diagenesis.
Most geologic storage targets are sedimentary rocks
where CO2
storage is trapped in the pore space between
grains. Igneous ormations have great potential or CO2
because o their huge expanse, but have only recently
started to be studied as potential storage reservoirs.
Coalbeds are a group o rocks that have their own unique
properties (cleats) that control luid paths and a rock
matrix where physical adsorption in the matrix would be
the principal means o capturing CO2.
2.1 Reservoir Properties
Rocks are oten not as solid as they appear to the naked
eye. Microscopically, there are voids or pore spaces among
the sediment grains orming a rock, not unlike the space
surrounding marbles in a jar. Porosity is the irst essential
element o a reservoir, shown schematically in Figure 2-1
and microscopically in Figure 2-2. Permeability, which
involves the interconnectedness o the individual pores,
is the second essential element (Figures 2-1 and 2-2).
Permeability is the capacity o a rock to transmit luids
through interconnected pores on a microscopic scale.
Permeability depends on the size and shape o the pores,
especially the pore throats (narrow channels between
pores) that control interconnections, and the extent o
these interconnections.
2.0 Characteristics of Storage Reservoirs and Confining Units
Figure 2-1. Porosity in Rocks and Rock Permeability.
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2.0 Characteristics of Storage Reservoirs and Confining Units
There are predictable trends in porosity and permeability
in reservoirs related to the depositional environment
where sediments were deposited. Reservoirs associated
with delta ormations, rivers and lood plain deposits
(luvial), submarine canyons and slumpsdeltas in deep
water (turbidites), and carbonate rees are known or
their good porosity and permeability. Rock units ormed
by windblown sand (eolian) both along sea shores and in
deserts are also good reservoirs. Diagenesis over millions
o years tends to alter the trends initially established by
their depositional pattern. However, paths o luid low
ollow the path o least resistance. For the most part theyare predictable. Thus, injected CO
2would be anticipated
to abide by the reservoirs internal architecture. The
reservoir is not one large uniorm sand box, but rather has
deined boundaries and barriers initially deined by the
depositional environment in which it was deposited.
Both porosity and permeability (generation, magnitude,
and distribution) dier considerably between igneous,
metamorphic, and sedimentary (clastic and carbonate)
reservoirs. Diagenetic changes can create or destroy the
original porosity and permeability, or create barriers toluid low. Porosity, usually caused by racturing and/or
dissolution o the original rock matrix, is oten reerred
to as secondary porosity. In some cases, the secondary
porosity considerably increases the porosity o the rock
matrix and is the primary mechanism or luid storage
and luid low. Geologic storage o CO2, regardless
o other actors, must have suicient areal extent
and reservoir volume to hold large volumes, possibly
requiring several stacked ormations (oten deposited
over hundreds o thousands o years or millions o years
within the same named ormation) and their respective
trapping mechanisms and seals.
2.2 Sealing and Trapping MechanismsSince the density o CO
2is less than saline water, it tends
to loat upward; thereore, a seal (requently called the
caprock) above the storage unit is required. Seals have
to signiicantly retard the movement o luids (Couples
2005). Without a seal, hydrocarbons (oil) generated
at depth would have long ago migrated toward the
surace and either biodegraded to heavier oil or escaped
to the atmosphere. In the same manner, injected CO
will not remain in a storage reservoir unless adequate
seals are present. Analysis o seals involves assessment
o their thickness, lateral extent, permeability, andgeomechanical properties (rock mechanics), such that
their eectiveness can be quantiied. Factors that may
inluence the integrity o a caprock include lithology
(type o sediment), thickness, burial depth, ductility
Figure 2-2. Microscopic Schematic of Rock Porosity and Permeability.
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2.0 Characteristics of Storage Reservoirs and Confining Units
(ability to stretch or low without breaking), permeability,
and lateral continuity (Allen and Allen, 2005). Clays,
claystones, shales, chalks, and evaporites ormed by
evaporation o salt water, such as gypsum, anhydrite,
and halite, are avorable lithologies or sealing (Grunau,1987). A rock that has been drilled rom a deposit that
was laid down at the bottom o a shallow lake over a
ew tens o thousands o years is shown in Figure 2-3
(let). Individual bands o ine clay (dark brown) are
visible, as well as courser sand (light tan), a high organic
content ine sediment (decomposition o years o algae
growth - black layer), a grey/white layer o salt (the
lake dried out), ollowed by more sediment deposited
in the lake in more recent time. Fluid low would be
anticipated to low horizontally through the small zones
i the permeability is high enough but would be greatly
restricted rom moving vertically because o the bedding
plains (ine shale and anhydrite) layers. Fluid low wouldbe anticipated to be higher in the course sand layer than
in the layers composed o iner silt and clay. This shale
core, i thick enough, may be a seal or geologic storage.
Well-sorted beach sand is shown in Figure 2-3 (right)
would make an excellent reservoir; reservoirs are rarely
as uniorm except on a small scale o less than inches as
depicted with this photo.
Figure 2-3. Shale, sand, and anhydrite core from Colorado (left)and well-sorted beach sand (right). (Courtesy of USGS.)
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2.0 Characteristics of Storage Reservoirs and Confining Units
Figure 2-4. Capillary trapping of CO2
occurs in narrow pore
throats, which prevents the CO2
from migrating up from
the larger pores in the rock matrix. The strength of capillary
trapping depends on the width of the pore radii and on the
interfacial tension at the interface between the two fluids
(water and CO2). (CO
2Capture Project, 2009.)
Figure 2-5. Structural traps: (left) Anticline, (center) Fault, (right) Salt Dome as trap. (Modified from Petroleum Research
Institution Website, 2008.)
Trapping mechanisms are primarily stratigraphic or
structural depending on the physical processes by which
they isolate an area or ormation. Stratigraphic traps are
the result o lithology (rock type) changes. Common
stratigraphic sealing units are thick layers o shales orevaporites, which unction as hydraulic resistant seals,
as shown on microscopic level in Figure 2-4. Structural
traps can be divided into three orms: anticline trap, ault
trap, and salt dome traps. Anticline traps are ormed by
olding, causing isolation o reservoirs in high points
(Figure 2-5 let). Anticlinal traps are important in
petroleum exploration and could just as easy be or
geologic storage. Fault traps are ormed by aulting
with parallel rock sections moving so that impermeable
rock types trap the migrating luids within a reservoir
(Figure 2-5 center). Salt dome reservoirs are ormed by
salt domes or diapirs intruding into sedimentary layers
and isolating areas along the lanks o the salt structure
(Figure 2-5 right).
I both the seal and storage unit outcrops at some
extended distance rom where the CO2
is injected, the
seal may not provide containment or the time period
necessary or CO2storage.
Seals have been classiied into two main types:
Membranesealsthatrelyoncapillaryprocesses.
Hydraulic resistance sealsthatrely onlowleakage
rates (Brown, 2003).
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3.0 Depositional Environments
The majority o geologic units being considered or
geologic storage are sedimentary, having been ormed
in reshwater lakes or saline oceans, known as basins.
The current rock ormation (reservoir) architecture isthe result o millions o years o sediment deposition
in these basins. The orientation o the original deltas,
beaches, rees; how the basins were illed; and what has
happened in the intervening time since the deposition
(called diagenetic alteration) inluence the low o luids
like CO2.
Each type o geologic ormation has dierent
opportunities and challenges. While geologic ormations
are ininitely variable in detail, they have been classiied
by geologists and engineers in the petroleum industry by
their trapping mechanism, the hydrodynamic conditions(mechanical orces that produce), lithology (physical
characteristics), and more recently by their depositional
environment (how they were ormed). The depositional
environment inluences how ormation luids are held in
place, how they move, and how they interact with other
ormation luids and solids (minerals). These properties
may allow the ormation to be labeled as reservoirs,
which in a broad sense permits the containment o
liquids or gases. For the purposes o geologic storage,
the geologic ormation/reservoir classiication system
has been expanded to include unconventional reservoirs,
such as coalbeds, and igneous ormations, such as
stacked basalts. By understanding the depositional
environments o potential reservoirs, correlations can be
drawn rom similar depositional environments around
the world. This could potentially eliminate some o the
site-speciic characterization requirements or similar
depositional systems. The reservoir classiication scheme
developed or CO2
storage, based on depositional
environments, is presented as Table 3-1. For some
systems like granite an igneous rock or metamorphic
rocks there is little or no porosity or permeability except
occasional racture systems, which are oten solutionilled with other minerals, leaving them with little or no
storage potential these system are not discussed in this
document. The reservoirs internal architecture governing
low characteristics, potential chemical reactions, and
geomechanical processes rom the injection o CO2
into
dierent types o reservoir depositional environments
are summarized in Table 3-2.
For luid low in porous media, knowledge o how
depositional systems ormed and directional tendencies
imposed by the depositional environment can inluence
how luids lows within these systems today and how
CO2
in geologic storage would be anticipated to low
in the uture. Although diagenesis has modiied luidlow paths in the intervening millions o years, the basic
architectural ramework created during deposition
remains. Geologic processes that are working today also
existed when the sediments were initially deposited.
Analysis o modern day depositional analogs, evaluation
o core, outcrops, and well logs rom ancient subsurace
ormations provide an indication o how ormations
were deposited and how luid low within the ormation
is anticipated to low.
Compartmentalization is graded on how eective the
bales between adjacent areas o deposition are. This isdependent on the permeability o the material and the
amount o luid low.
3.0 Depositional Environments
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RockClassifcation
Lithology
Geoscienc
eInstituteorOilandGasRecovery
Re
searchClassifcationin1991
DOEsOilReservoir
Classifcationrom1
990s
SequestrationFormationClassifcat
ion2010
Sto
rage
Seals
Sedimentary
Clastic
Reservoirs
Delta
Delta/Fluvial-Dominated
ClassIReservoirs
De
ltaic
Delta/Wave-Dominated
Delta/Tide-Dominated
Coal/Shale
Shales
(fneterrigenousmaterialsclays
aswellasromcarbonates)
DepositedinLacustrine,Fluvia
l,Alluvial,Near
ShoreandOpenOceanMarine
Environments
Delta/Undiferentiated
Fluvial
Fluvial/BraidedStream
Class5Reservoirs
Flu
vial
Fluvial/MeanderingStream
Fluvial/Undiferentiated
AlluvialFan
Alluvial
Strandplain
Strandplain/BarrierCores
andShoreaces
Class4Reservoirs
Stran
dplain
Strandplain/BackBarriers
Strandplain/Undiferentiated
Turbidites
Slope-Basin
Class3Reservoirs
Turbidite
Basin
EolianW
indBlown:Clasticsand/orCarbonates
Eo
lian
LacustrineL
akeDeposited:Clastics,Carbonates,Evaporites
Lacu
strine
Evaporites
(romvariousLithologyDepositedinAridSettings)
Shel
Shel
Carbonate
Reservoirs
Carbonate
(>50%
Carbonate
contentbut
cancontain
Terrigenous
materials
sand,feldspar,
non-carbonate
bouldersand
evaporites)
Peritidal
Dolomitization
MassiveDissolution
Other
ShallowShel/
Open
Dolomitization
Class2Reservoirs
Shallow
Shel
MassiveDissolution
Other
ShallowShel/
Restricted
Dolomitization
MassiveDissolution
Other
Ree
Dolomitization
Ree
MassiveDissolution
Other
ShelMargin
Dolomitization
MassiveDissolution
Other
Slope-Basin
Other
Igneous
Basalts
Basaltic
Intero
wZones
Granitic
Metamorphic
Table3-1.ReservoirDepositionalClassiicationSchematic.
3.0 Depositional Environments
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Table 3-2. Characteristics of Depositional Reservoirs.
Classification
Primary Flow
Direction of
Injected Fluids
Composition
Characteristic
Deposition
Pattern
Potential CO2
Interactions
Chemical
Interactions
with CO2
Compartmentalization1
Deltaic
Parallel to
stream or deltaaxis when
deposited.
Fluids low
in high
permeability
paths
Ranges rom course
sand in channelbottoms to ine
clays in seals, but
ormed within
predictable ranges
o deposition or
types o deltas
Dependent on
delta type and
where within
delta.
Interactiondependent
on carbonate
content and
clay barrier
(shales) within
Moderate
chemical
reactivity
depending on
clays
Depends on where
in depositional
environment
Coal
Parallel to axis
o least stress
imposed by
diagenesis
on the cleat
network
Highly variable
content with
organic content
showing remains o
plant materials, as
well as various clays
and sand
Highly variable,
but deposited
in layers
Adsorption
dominates
Adsorption
dominates, but
little chemical
reactivity
Controlled by cleat
network
Shale
Flow direction
controlled bydiagenesis ater
deposition.
Little low- low
porosity and
permeability
Mostly ine tovery ine clays,
ine sand, organic
matter, and/or
ine carbonate
ragments
Deposited
as layers inlow low
environments
causing drapes
over higher
permeability
larger sediment
Forms seals
Slow chemical
reactions with
clays in shale
Few compartments,
orms seals and barriers
within and between
other ormations.
Fluvial
Parallel to axis
o stream when
deposited.
Fluids low
in high
permeability
paths
Ranges rom course
sand in channel
bottoms to ine
clays in seals, but
ormed within
predictable ranges
o deposition or
rivers
Fining upward
in channel
Interaction
dependent
on carbonate
content and
clay barrier
(shales) within
Moderate
chemical
reactivity
depending on
clays
Highly variable
depending on where
within luvial system
Alluvial
Parallel to
axis o alluvial
an when
deposited
Wide mix o
poorly sorted
materials, size, and
composition
Fan thinning to
distal end
Highly
variable
based on rock
composition
Highly variablebased on rock
composition
Little
StrandplainParallel to
beach ront
Principally quartz
sands
Parallel to the
beach and
perpendicular
to the beach
Little
interaction
Little chemical
reactivity as
mostly quartz
sand
Moderate
Turbidite
Parallel to axis
o deposition
o an
Variable
composition and
ranges rom iner
carbonate, sand,
ine clays to very
ine clays
Repeated
layers o ining
upward. Fine
materials
toward distal
end
Interaction
dependent
on carbonate
content
Chemical
reactivity
dependent
on carbonate,
quartz sand,
and clay
composition
Highly
Eolian
Parallel toprevailing
wind direction
at time o
deposition
Mostly well-
rounded quartz
sands, ew ines
Patterndepends on
dune type, but
within dune
type are usually
consistent
Little
interaction
Little chemical
reactivity as
mostly quartz
sand
Highly
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Classification
Primary Flow
Direction of
Injected Fluids
Composition
Characteristic
Deposition
Pattern
Potential CO2
Interactions
Chemical
Interactions
with CO2
Compartmentalization1
Lacustrine
Parallel tohorizontally
depositional
bedding plane
Flow direction
controlled by
diagenesis ater
deposition.
Little low
Fine clays, silt,
sand, organics,
windblown ines,
evaporites, and
carbonates
Highly layered
depositional
pattern, oten
relecting
seasonal
variations
Interaction
dependent
on carbonate,
evaporite,
and clay
content
within
Highly variable
dependent on
composition o
rock.
Highly layered
Shelf Clastic
includingBarrier Island
Highly variable
and controlled
by diagenesisater deposition
Mix o terrestrial
material (quartz,
clays, etc.) and
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nature o the deposits is dependent on the type o riverand the climate. Sediments in luvial dominated delta
environments are usually described as ining upward,
meaning that coarse sediments are on the bottom and
ine material is deposited on top. These types o deltas
tend to orm ingers o delta ront sands and the general
distribution o major sands tends to be perpendicular to
the shoreline. The lower delta plane channels become
more numerous as they divide into smaller distributaries.
Figure 3-1. Components of a Deltaic System. (Coleman and
Prior, p. 139, 1982.)
Figure 3-2. Mississippi River Delta, United States, Lobe
Development over the Last 5,000 years. (Wikipedia, 2010;
and Frasier, 1967.)
Figure 3-3. Mississippi River Delta, United States. A Recently
Developed Elongated Shaped Delta that is River-Dominated.
Photo taken by the ASTER Instrument on the Terra Satellite,
May 24, 2001. (Courtesy of NASA.)
3.1 Deltaic Reservoir Properties
Deltaic Depositional Environment
Deltas are composed o clastics, which are rock ragments
rom original geologic units that are re-deposited. There
are several groups o deltaic reservoirs, luvial (river)-
dominated, wave-dominated, tide-dominated, and
undierentiated deltas (Fowler, Rawn-Schatzinger, et al.,
1995). Each o these dierent depositional environments
will have distinctive luid low patterns due to their
internal architecture. The components o a delta
system are presented in Figure 3-1. Deltaic reservoirs
are created by stream or river ed systems that deposit
sediments rich in organic matter into standing bodies
o water (lakes, bays, lagoons, oceans, etc.), resulting
in an irregular expansion o the shoreline. These deltas
and rivers meander (move laterally) over time basedon the amount and type o deposition, river low, and
looding (Figure 3-2). In general, all deltas are marked
by a thickening wedge o sediment at the interace o
land and water. This is ormed by the rapid inlux and
deposition o sediment at a rate that exceeds its removal
and redistribution by wave and tidal action.
A luvial-dominated delta environment is associated
with streams and rivers eroding sediments and rocks,
the transportation, and deposition o sediments
(Figure 3-3). The upper delta plane is the area where
luvial, lacustrine (lake), and swamp sediments occur. The
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A tide-dominated delta is where sedimentation at
the delta ront is controlled by the high and low tides
(Figure 3-6). Multiple small-olded ridges are developed
in a linear pattern parallel to the direction o tida
currents, which may be perpendicular or parallel to the
delta ront. The lower delta plain will have extensive tida
lats where mud is deposited. The tidal-dominated delta
Other depositional eatures include levees, which
are long and narrow ridges on either side or between
streams and can develop bays between the channels.
In addition, marshes and swamps are usually extensive
between the bays and channels. The preerential low
through this depositional environment is along theancient river channels.
A wave-dominated delta environment is associated with
large waves that run over the top o spits or sand bars
and down the landward side Figure 3-4 and Figure 3-5.
The sands tend to be reworked into numerous coastal
barriers that are orientated roughly parallel to the
shoreline. Wave-dominated deltas have a broad outer
mound o beach material separated by crescent-shaped
troughs. A coarsening upward sequence is produced
through wave-dominated delta growth, but the sands o
the upper part o the sequences should show low-anglecross bedding and planar bedding through wave action
on beaches, and some onshore-directed cross bedding
rom dunes in the shoreace zone. Clear channels are
not as evident as river-dominated deltas and sediment
is deposited more parallel to the shore than away rom
the shore and the channel low is oblique or parallel to
the shore.
Figure 3-5. Rhone River, France. A Wave-Dominated
Elongated Delta. Flooding in Southern France, the
worst in decades carried sediment tinting the otherwise
black Mediterranean Sea a bright blue. (Photo from
Terre MODIS Satellite, NASA Earth Observation Collection,
December 1, 2003, courtesy of NASA.)
Figure 3-4. Nile River Delta, Egypt. A Lobe Shaped Delta
that is Wave-Dominated. North is top of image. Photo
taken from MISR Satellite, January 30, 2001. (Courtesy
of NASA.)
Figure 3-6. Ganges/Brahmaputra River Delta, Bangladesh.
This is a Tidal-Dominated Delta - the Largest Inter-Tidal
Delta in the World. North is top of image. (Photo from
MISR Satellite, November 6, 1994, courtesy of NASA.)
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adsorption capacity is based on the exposed surace
area o the coal, which is usually governed by diagenetic
processes. Coal seams tend to have low permeability
and the majority o the porosity and permeability is the
result o racturing/cleats (Figure 3-8). One issue that is
still being investigated is coal swelling in the presenceo CO2, which may reduce or cuto the low o CO
2or
methane.
Shale, the most common type o sedimentary rock, is
characterized by thin, horizontal layers o rock with low
permeability in both the horizontal and vertical direction.
Shale is composed o ine clay particles that are packed
so closely together that luids cannot move between the
particles. Clays are naturally occurring materials made
up o ine-grained minerals derived rom igneous rocks.
Fluid low is governed by ractures that could be ormed
ater deposition and other diagenetic processes. Ingeneral, vertical luid low is negligible when compared
to horizontal luid low occurring along the bedding
plane suraces. Most o the luid is transmitted along
ractures parallel to the horizontal bedding planes. In
many cases, because o the low permeability o shale
it is considered a caprock or sealing ormation or other
types o reservoirs.
Many shales contain 1 to 2% organic material in the ormo hydrocarbons, which provide an adsorption substrate
or storage similar to coal seams. Additional research
is needed to ocus on achieving economically viable
CO2
injection rates, given shales low permeability. It is
possible that this research may lead to the conclusion
that it is not easible to use ractured, organic-rich shales
as reservoirs or geologic storage.
Currently, these tight organic rich shales are being
developed as gas and oil shale plays, such as the Marcellus
Shale, and are a signiicant contributor to the domestic
natural gas resource. The shale is artiicially ractured toallow the release o the natural gas. This may provide a
potential storage reservoir or CO2
once the natural gas
has been removed.
Figure 3-8. Structure of coal and the cleat s ystem within. The frequency of
cleats is generally higher in coal than in the shale layers separating coalbeds.
Cleats provide the pathway for f luids to move through the coal. ( Tremain et al.,
1994; Dallegge and. Barker, 2009.)
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3.2 Carbonate Reservoir and Ree
Reservoir Properties
Carbonate Depositional Systems
Most carbonate material comes rom the growth anddemise o organisms that live in oceans on continental
shels. The organisms make their hard parts out o
carbonate by extracting calcium and magnesium ions,
and CO2
rom seawater. Over 90% o carbonates ormed
in modern environments are thought to be the skeletal
remains o biological organisms that ormed under
marine conditions avorable or their growth. These
conditions include light, temperature, salinity, substrate,
and presence/absence o clastics high in silicon.
The main controls on carbonate sedimentation are
tectonic movement and climate (Tucker and Wright,1990). The organisms that are the biological building
blocks o carbonate rees have speciic tolerances to
light, temperature, and water depth. Sea level changes
associated with mountain building and glaciers cause
sea transgression and regression that can control
sedimentary deposits that may cover carbonate
generating systems. The wide variety o depositional
environments possible or carbonate deposits is shown
in Figure 3-9.
Four aspects o carbonate deposition dier rom clastic
sedimentation: (1) shallow water marine carbonate
buildups are similar through geologic time; (2) they orm
in situ in shallow water with warm tropical conditions;
(3) carbonate muds are extensively preserved during
compaction; and (4) early diagenesis eects that occurjust ater deposition. Carbonate buildups have been
accumulating in dierent locations or approximately
545 million years (Demicco and Hardie, 1994).
Shapes o carbonate deposits include:
1) Isolated banks with lat tops and walls that slope
steeply down into the ocean. A modern example is
the Bahamas Bank.
2) Continental shel deposits. Modern examples are
the shelves o the Belize (Belize) and Great BarrierRee (Australia).
3) Ramp-like shelves that slope into shallow ocean
basins. A modern example is the southern shel o
the Arabian Gul.
Figure 3-9. Carbonate Depositional System. An idealized block diagram of carbonate depositional
environments based on Pennsylvanian carbonates in southeastern Utah. (Modified from Chidsey, 2007.)
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As compared to clastic sedimentation, carbonate
sedimentation is much more inluenced by aulting,
racturing, precipitation, and solution channels ater
initial deposition. In carbonates, there are ar ewer
recognizable trends in direction o luid low imposed
by the initial deposition system (ree, shallow shel, etc.).Most o the trends in luid low are the result o changes
to the rock occurring ater deposition (Budd, et al., 1995).
There are three carbonate depositional environments
that are being considered or geologic storage: Peritidal,
Shallow Shel/Open, and Shallow Shel/Restricted.
Peritidal carbonate depositional environments are
deined as the area between the highest tide to the
area exposed during the lowest tide. The term peritidal
is generally used to describe a variety o carbonate
environments associated with low-energy tidal zones,
especially tidal lats (Folk, 1973). The orientation and sizeo these depositional environments is based on the size
o the tides and the luctuation o sea levels. Ancient
peritidal carbonates commonly orm stratigraphic
traps or hydrocarbons as a result o onlap and olap
geometries, creating pinch-out structures (Shinn, 1983a).
These carbonate units have usually undergone changes
to the rock, including racturing that causes secondary
porosity.
Shallow shel open and restricted carbonates describe
the original carbonate rocks that were deposited either
in shallow waters on open shelves, restricted lagoons,
deeper water on the shel margin, or basin slopes as
precipitates. As aorementioned, changes in the rock
signiicantly impact the porosity and permeability o the
rock over time, which also aects reservoir quality both
or oil and gas accumulation and or potential capacity
as a CO2
storage reservoir. The low patterns o water
above (vadose zone) and below the water table (phreatic
zone) are shown in Figure 3-10; this is important to
understanding how secondary porosity controls luid
movement.
Reef Depositional System
The geometry o a ree basin and its tectonic history
aect the porosity, permeability, and development o
carbonate reservoirs (Klovan, 1974). Ree development
corresponds to the overall history o a basin, which is
related to tectonic movements and the rise and all o sea
level. Similar controls aect recent and ancient rees and
allow or analogies between depositional settings with
similar eatures. For example, pinnacle rees developed
in response to gradual and continual subsidence, withthe rees growing upward to obtain light as the sea leve
Figure 3-10. Groundwater zones. Flow may be through
pore network s, or fractures . Dissolution and mixing
occurs in the vadose zone and the lower phreatic zones.
(Tucker and Wright, 1990, pp 337.)
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rises. The development o pinnacle rees ound in Alberta
is illustrated in Figure 3-11. The restricted basin had
barriers that limited water circulation, which prevented
development o more massive rees that result rom
higher amounts o nutrients.
Isolated banks and rees orm on small up-aulted blocks
related to early opening o ocean basins, along the
margins o uplited continental margins, and as ringing
rees on volcanic islands. The huge ancient carbonate
continental shel that rimmed the North American
continent during the (Cambrian-Ordovician period, 100
million years BP) is an example o a shel deposit on a
stable, passive margin.
3.3 Turbidites Reservoir PropertiesTurbidite Depositional System
Turbidites are downslope gravity lows operating at
water depths o greater than 150 eet and orm slope,
shel, and basin deposits. Much like alluvial deposits that
occur at the base o many mountain ranges, these are the
subsea equivalent, but originate at the margin between
shallow water shel and deeper basins at the continental
margins, as shown in Figures 1-8 and 1-9. They can be
composed o both clastic- and carbonate-derived rock.
Major rivers do not stop at ocean boundaries, they cancontinue hundreds o miles out to sea as subsurace
rivers (turbidity lows), across the continental shel,
and travel down submarine canyons to the basin loor.
Large luvial inputs beyond river deltas are enhanced
during loods o major rivers; the larger low volume o
sediment-laden (i.e. turbid) water scours storm shels
and lagoons, becoming more and more turbid, carrying
dense, sediment-rich water into the ocean where it lows
downhill. Turbidites occur in both submarine canyons
and on the continental slope. On slopes, they can low
downslope, orming a submarine an that looks a little
like an underwater delta. The place o origin on thecontinental shel oten reills with sediment and is later
scoured o again, causing another layer to be deposited
at the base o the slope. Two dierent shaped o
turbidites are ormed based on the velocity o the low,
the sediment size, the width o the coastal plane and
the basal slope angle (Figure 3-12). Turbidites tend to
Figure 3-11. Pinnacle Reef Development in Alberta. (Alberta Energy Utility Board, 2004.)
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become stacked rom repeated sequences o deposition
down canyons or rom scouring o the continental slope
and many orm at nearly the same point o origin.
Since the low o sediment is mostly water, turbidite
sediment is well sorted when deposited on the basinloor. Turbidites can be divided into coarse-grained
(more sand) and ine-grained (more mud and less sand)
lows where the sand and mud produced dierent
sediment distribution patterns and a dierent interna
architecture as a result. As compared to many other slow
geological processes, sand and mud lowing down a
submarine canyon causes heavier sediment to all out
aster and lighter sediment to travel arther. Turbiditesthat separated rom their place o origin on the edge o
the continental slope and then deposit on the basin loo
Figure 3-12. A. Coarse-Grained, Sand-Rich Turbidite (brown) System, B. Fine-Grained, Mud-Rich Turbidite (brown) System. (Bouma, 2000.)
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are thickest at the base o the slope and thin as they move
outward into the basin (Pratson, et al., 2000). Turbidites
at the base o the submarine canyon tend to become
stacked rom repeated sequences o deposition. The
preerential luid low path within a turbidite is parallel
to the axis o the mass low (LaBlanc, 1972).
3.4 Strandplain Reservoir Properties
Strandplain Depositional System
Coastal strandplain and barrier island deposits are
laid down along a shoreline where wave and tidal
orces dominated the transport o sediments (Rawn-
Schatzinger and Lawson, 1994). Strandplains typically
are created by the redistribution o coarse sediments
by waves and long-shore currents on either side o awave-dominated delta. Tectonics and sediment supply
rate control the thickness, lateral extent, and ormation
o strandplain deposits (modern analogs are shown as
Figures 3-13 and 3-14).
Strandplain deposits are ormed by sediments moving
outward into a sea (the sea level elevation is alling). The
shoreace builds seaward and is shaped by waves and
currents, which spread out in broad continuous stacked
beach deposits along coastlines (DOE/Bartlesville
Project Oice, 1994). Two orms o strandplain sand-rich and mud-rich are distinguished by sediment
type. Sand-rich strandplain deposits are continuously
deposited parallel and perpendicular to the shoreline
and have higher permeability. The sands within mud-
rich strandplains are not continuous in the perpendicular
direction to the shoreline and have low permeability.
Lagoonal deposits (muds and ine silt that orm shale)
are usually not associated with strandplains because the
waves moved ine sediment up the coast and oten out
to sea. A strandplain with dozens o old beach ridges
seen in Figure 3-14 rom Kitikmeot Region, Nunavut,
Canada can be dated back about 10,000 years whenthe last glaciers in the area retreated. At the end o the
last glaciation, the beach level can be seen in the low,
dark cli line at the oot o the slope o the plateau. The
resulting clean sand is oten well sorted and has high
permeability and porosity. Preerential luid low is in the
direction paralleling the axis o the deposit.
Figure 3-13. Strandplain Deposit along the
South Carolina Coast (infrared satellite image).
Note the linear sand ridges building toward the
ocean as the strandplain builds through sand
brought by long-shore currents. The layered
appearance results from the accumulation
of new strandlines. (Hayes, 1989.)
Figure 3-14. Strandplain near the mouth of the Kugaryuak
River, Coronation Gulf, Southwest Kitikmeot Region, Nunavut,
Canada. (Reproduced with the permission of Natural Resources
Canada 2010, courtesy of the Geological Survey of Canada.
Photo 2002-377 by Daniel Kerr.)
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Barrier Island Depositional System
The depositional processes that inluence barrier island
ormations are a combination o wave/tidal action and
long-shore currents (DOE/Bartlesville Project Oice,
1994). Sediments are normally carried along the coast by
currents; commonly the source o the sediments is romdeltas. Wave action sorts the sediments based on grain
size and will deposit the larger sized particles on the
sea side o the barrier island irst and smaller particles
later. The deposition is based on the amount o energy
generated by tidal inluences, the strength o currents,
and the strength o the waves. During storms, iner
grained sediment may be carried up and over the barrier
island to be deposited in the mudlats and lagoons on
the land side o the barrier island.
Figure 3-15. Barrier Island with Beach and Back Dune
areas visible, South Carolina. (Photo courtesy of RichardSchatzinger, Consulting Carbonate Sedimentologist.)
Figure 3-16. Barrier Island along the Texas Coast with oceanto the left, shoreline, beach and dune ridges, mudflatsand lagoon before marshes on mainland on right of photo.(Photo Courtesy of the University of Texas.)
Two modern analogs o barrier island deposition are
shown in Figures 3-15 and 3-16. Barrier islands are easily
susceptible to storm degradation, which can erode the
sand, move the sand in the direction o the current and
waves, and overtop the island (they are unstable land
masses). Ancient barrier island deposits encounteredthe same orces (McCubbin, 1982) and preerential luid
low (highest permeability) within the (Cole, et.al., 1994
barrier island ormations is highly variable and controlled
by changes to the rock ater deposition.
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3.5 Alluvial and Fluvial Fan Reservoir
Properties
Alluvial Depositional Systems
Alluvial depositional systems, like most depositionalsystems, are gravity driven. In general, an alluvial
sediment source comes rom higher elevations, such
as mountains, and is deposited in valleys. The sediment
source and depositional l
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