Small CO2 EOR Primer

8/9/2019 Small CO2 EOR Primer

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Carbon DioxideEnhanced Oil Recovery

Untapped Domestic Energy Supply

and Long Term Carbon Storage Solution


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Introduction

As the United States grapples with the twin challenges

o reducing dependence on oreign energy sources and

reducing emissions o greenhouse gases, the topic o

carbon dioxide (CO2) enhanced oil recovery (EOR) has

received increased attention. In order to help inorm

the discussion, the Department o Energys National

Energy Technology Laboratory has published this

primer on the topic. Hopeully, this brie introduction

to the physics o CO2

EOR, the undamental engineering

aspects o its application, and the economic basis on

which it is implemented, will help all parties understand

the role it can play in helping us meet both o the

challenges mentioned above.

Disclaimer

Reference herein to any specific commercial product, process, or service by trade

name, trademark, manufacturer, or otherwise does not necessarily constitute or imply

its endorsement, recommendation, or favoring by the United States Government or

any agency thereof. Neither the United States Government nor any agency thereof,

nor any of their employees, makes any warranty, express or implied, or assumes any

legal liability or responsibility for the accuracy, completeness, or usefulness of any

information, apparatus, product, or process disclosed, or represents that its use would

not infringe privately owned rights.


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3

Untapped Domestic Energy Supply and Long Term Carbon Storage Solution

Table of Contents

The Basics of Carbon Dioxide EOR 4

Why It works 4

How It Works 6

How Much Extra Oil Gets Produced 8

Where Its Being Done 9

Screening Reservoirs for CO2

EOR 9

CO2

Availability 10

Anthropogenic CO2

Sources 11

US CO2

EOR Demographics 12

CO2

EOR Economics 13

Its Future Potential 14

Production Outlook 14

Tax Incentives 17

CO2

EOR and Sequestration 17

Sequestration Potential in Oil Reservoirs 18

What DOE is Doing 21

Whats Next? 23

Glossary 26

Contacts 30

Carbon Dioxide Enhanced Oil Recovery


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4


The Basics of Carbon Dioxide EOR

Why It Works

Why does injecting carbon dioxide (CO2) into the pore spaces o a rock help

move crude oil out? CO2

has two characteristics that make it a good choice

or this purpose: it is miscible with crude oil, and it is less expensive thanother similarly miscible uids. What does it mean to be miscible? Imaginethat you get oil on your tools while working on your cars engine. Water willget a little o the oil o, soap and water will do a better job, but a solventwill

remove every trace. This is because a solvent can mix with the oil, orm ahomogeneous mixture, and carry the oil away rom the tools surace. Fluidpairs like ethanol and water, vinegar and water, and engine degreasersand motor oil exhibit miscibility, that is, the ability o luids to mix in all

proportions (see page 26 or a glossary). As we know, oil and water dontmix, as they are immiscible; and as a result, completely removing oil romtools or engine parts requires a solvent.

We could use similar miscible solvents to clean the oil rom undergroundreservoirs, but since these products are rened rom crude oil and thereorerelatively expensive, it does not make economic sense to do so, regardless

o their eectiveness. The same goes or natural gas enriched with heavierhydrocarbons like propane; it is miscible with oil but it is also a valuablecommodity. However, underground deposits o CO

2are relatively inexpensive,

naturally occurring sources o the gas that can be extracted in large quantities,

making it a more sensible choice. I CO2produced by human activities can becaptured inexpensively, it could become

a source as well.

When we inject CO2

into an oil reservoir,it becomes mutually soluble with the

residual crude oil as light hydrocarbonsrom the oil dissolve in the CO

2and CO

2

dissolves in the oil. This occurs mostreadily when the CO

2density is high

(when it is compressed) and when the oil

contains a signicant volume o light(i.e., lower carbon) hydrocarbons (typically

a low-density crude oil). Below someminimum pressure, CO

2and oil will no

longer be miscible. As the temperatureincreases (and the CO

2density decreases),

or as the oil density increases (as thelight hydrocarbon raction decreases),the minimum pressure needed to attain


Oil and water orm separate

phases when mixed.

Oily suraces can be cleaned i a solvent is used

that is completely miscible with the oil.


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5


oil/CO2

miscibility increases. For this reason, oil eldoperators must consider the pressure o a depletedoil reservoir when evaluating its suitability or CO

2

enhanced oil recovery. Low pressured reservoirs may

need to be re-pressurized by injecting water (seepage 6 sidebar on waterooding).

When the injected CO2

and residual oil are miscible,the physical orces holding the two phases apart(interacial tension) e ectively disappears. This

enables the CO2

to displace the oil rom the rockpores, pushing it towards a producing well just as acleaning solvent would remove oil rom your tools.

Cross-section illustrating how carbon dioxide and water can be used to ush residual oil rom a subsurace rock ormation between wells

As CO2

dissolves in the oil it swells the oil and reducesits viscosity; aects that also help to improve theefciency o the displacement process.

Oten, CO2 oods involve the injection o volumeso CO

2alternated with volumes o water; water

alternating gas or WAG oods. This approach helpsto mitigate the tendency or the lower viscosity CO

2

to nger its way ahead o the displaced oil. Once theinjected CO

2breaks through to the producing well,

any gas injected aterwards will ollow that path,reducing the overall efciency o the injected uidsto sweep the oil rom the reservoir rock.



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6


How It Works

The physical elements o a typical CO2

lood operation can be used toillustrate how the process works. First, a pipeline delivers the CO

2to

the ield at a pressure and density high enough or the project needs(>1200 pounds per square inch [psi] and 5 pounds per gallon; or comparisonwater density is 8.3 pounds per gallon), and a meter measures the volumeo gas purchased. This CO

2is directed to injection wells strategically placed

within the pattern o wells to optimize the areal sweep o the reservoir. Theinjected CO

2enters the reservoir and moves through the pore spaces o

the rock, encountering residual droplets o crude oil, becoming misciblewith the oil, and orming a concentrated oil bank that is swept towards the

producing wells.

At the producing wellsand there may be three, our or more producers per

injection welloil and water is pumped to the surace, where it ows to a

centralized collection acility. The pattern o injectors and producers, whichcan change over time, will typically be determined based on computersimulations that model the reservoirs behavior based on dierent design

scenarios. A well maniold allows or individual wells to be tested to seehow much oil, gas and water is being produced at each location and i theconcentration o oil is increasing as the oil bank reaches the producing wells.

The produced uids are separated and the produced gas stream, whichmay include amounts o CO

2as the injected gas begins to break through

at producing well locations, must be urther processed. Any produced

CO2

is separated rom the produced natural gas and recompressed orreinjection along with additional volumes o newly-purchased CO

2. In

some situations, separated produced water is treated and re-injected,oten alternating with CO

2injection, to improve sweep efciency (the WAG

process mentioned earlier).

CO2

injection wellheadProduction well pump jack

CO2

pipeline metering

Waterooding and

Residual Oil

When an oil reservoir is rst

produced, the pressure that exists

in the subsurace provides the

energy or moving the oil, gas

and water that is in the rock to the

surace. Ater a while, the pressure

dissipates and pumps must

be used to remove additional

volumes o oil. Depending on

the characteristics o the rock

and the oil, a considerable

amount o the original oil

in place may be let behind

(perhaps 60 percent or more) as

residualoil. Waterlooding is aprocess whereby water is pumped

down selected wells to push a

portion o the remaining oil out

o the rock towards the producing

wells. In most cases, CO2

enhanced

recovery operations take place in oil

reservoirs where this less expensive

waterooding option has already

been implemented, although the

remaining oil saturation in the

post-waterood reservoir is still

signicant, perhaps 50 percent o

the original oil in place.



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Compressor or compressing gas prior to re-injection

Well production maniold to allow

individual testing o wells

Separator or separating

produced uids (oil, water,

and gas)

In WAG injection, water/CO2

injection ratioshave ranged rom 0.5 to 4.0 volumes o water

per volume o CO2 at reservoir conditions.The sizes o the alternate slugs range rom0.1 percent to 2 percent o the reservoir porevolume. Cumulative injected CO

2volumes

vary, but typically range between 15 and

30 percent o the hydrocarbon pore volumeo the reservoir. Historically, the ocus in CO

2

enhanced oil recovery is to minimize the

amount o CO2

that must be injected perincremental barrel o oil recovered, especiallysince CO

2injection is expensive. However, i

carbon sequestration becomes a driver or

CO2 EOR projects, the economics may beginto avor injecting larger volumes o CO

2per

barrel o oil recovered, i.e., i the cost o theCO

2is low enough.

CO2

processing plant where the gas is collected or re-injection



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How Much Extra Oil Gets Produced

The production plot shown below illustrates how a eld can respond to CO2

injection. This example, or Shell Oils Denver Unit in the Wasson Field in WestTexas, shows oil and water production, and water and CO

2

injection, oversixty years. The primary production portion o the elds lie lasted rom 1938through about 1965. The oil production rate peaked in the mid-1940s andthen began to decline as reservoir pressure depleted. The operator initiatedpressure maintenance with water injection (waterooding) in 1965 and oilproduction rates responded quickly.

As the injected water began to break through at the production wells, thevolume o water produced also rose rapidly in the 1970s. By the end o 1982,the volumes o water injected and produced were considerably more thanthe volume o oil produced. About two years ater the operator initiated CO

2

injection in 1983, the oil production decline began to slow and eventuallyleveled o. At the end o 1998, one could determine the incremental oilattributable to CO

2EOR by calculating the cumulative dierence between the

projected decline rate without CO2

injection and the actual production rate.

In this example, the volumes o oil produced are signicant because theDenver Unit ood is large, with more than 2 billion barrels o oil originally inplace (OOIP) and a residual oil saturation ater waterooding o 40 percent.The typical well pattern is ten producing wells or every three injectors.Currently, the Denver Unit produces about 31,500 barrels o oil per day, owhich 26,850 is incremental oil attributable to the CO

2ood. The Wasson

Fields Denver Unit CO2

EOR project has resulted in more than 120 millionincremental barrels o oil thru 2008.

8


Plot showing oil production versus

time or primary, secondary

(waterood) and tertiary (CO2

EOR)

oil production periods or the Denver

Unit o the Wasson Field in West

Texas. Incremental oil production

due to EOR is represented by the

green area under the curve at right.

The Wasson Fields

Denver Unit CO2

EOR

project has resulted

in more than

120 million

incremental barrels

o oil thru 2008.



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9

Where Its Being Done

The United States leads the world in both the number o CO2

EOR projects and in the volume o CO2

EOR oilproduction, in large part because o avorable geology. The Permian Basin covering West Texas and southeasternNew Mexico has the lions share o the worlds CO

2

EOR activity or two reasons: reservoirs there are particularlyamenable to CO

2ooding, and large natural sources o high purity CO

2are relatively close. However, a growing

number o CO2EOR projects are being launched in other regions, based on the availability o low cost CO

2.

Screening Reservoirs for CO2

EOR

What kinds o reservoirs are most suitable or CO2

EOR? In theory, any type o oil reservoir, carbonateor sandstone, could be suitable

provided that the

minimum miscibility pressure can be reached, there isa substantial volume o residual crude oil remaining,

and the ability o the CO2 to contact the crude oil isnot hindered by geological complexity. Typically, areservoir that has undergone a successul wateroodis a prime candidate or a CO

2ood.

Most o the large reservoirs in the Permian Basinare carbonate ormationstypically limestone ordolomitethat produce rom depths o 3,000 to 7,000 eet, and have undergone extensive waterooding. Post-waterood recovery could be 30 to 45 percent o the OOIP, with relatively high residual oil saturation. A successulCO

2EOR project could add another 5 to 15 percent o OOIP to the ultimate recovery.

In addition, the Permian Basin reservoirs tend to eature

a low geothermal gradient (i.e., rate o increase intemperature with depth), which makes the pressurerequired or CO

2miscibility with the crude oil lower.

Geologically, these reservoirs also exhibit a high degreeo continuity between wells, and rock that is laterally andvertically uniorm, and has relatively high permeability.Operators interested in enhancing recovery through CO

2

EOR will screen their reservoirs to determine the bestcandidates based on rock and uid characteristics, pastproduction behavior and response to waterooding, anddetailed geological assessments. The screening criteriaused to identiy avorable reservoirs are reservoir depth, oil gravity, reservoir pressure, reservoir temperature, and oilviscosity. A number o analysts have developed ranges or these screening criteria (see table), which operators canuse to high-grade their reservoirs or urther detailed technical and economic assessments. Perhaps the most criticalactor or selecting candidates or CO

2EOR is a growing consensus among experts that more detailed geophysical

mapping o the remaining oil in a reservoir is needed, particularly in geologically heterogeneous ormations.In the 1980s the Department o Energy (DOE) helped develop sotware screening tools designed to quickly identiyhow key variables might inuence CO

2project perormance and economics prior to perorming a detailed numerical

simulation. One such tool, CO2-Prophet, was developed by DOE and Texaco. A number o other commercial screening

tools are now available.

Criteria or Screening Reservoirs or CO2

EOR Suitability

Depth, t < 9,800 and > 2,000

Temperature, F < 250, but not critical

Pressure, psia > 1,200 to 1,500

Permeability, md > 1 to 5

Oil gravity, API > 27 to 30

Viscosity, cp 10 to 12

Residual oil saturation aterwaterood, raction o pore space

> 0.25 to 0.30



Depiction o reservoir model used or simulation o CO2

ooding


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CO2

AvailabilityAlthough the large Permian Basin reservoirs were readily recognized asideal candidates or miscible looding through CO

2injection, it was the

ready availability o a low-cost source o CO2 that drove the Permian BasinsEOR boom in the 1970s and 1980s. The irst commercial lood occurredin Scurry County, Texas, in 1972, in what was known as the SACROC Unit(SACROC stands or Scurry Area Canyon Ree Operators Committee). For this

project, the operator (Chevron) recovered CO2

rom natural gas processingplants in the southern part o the basin (that would have otherwise beenvented) and transported the gas 220 miles or injection at SACROC.

The technical success o this project, coupled with the high oil prices o thelate 1970s and early 1980s, led to the construction o three major CO

2pipelines

connecting the Permian Basin oil elds with natural underground CO2

sources

located at the Sheep Mountain and McElmo Dome sites in Colorado and

Bravo Dome in northeastern New Mexico (see map). Construction o thepipelines spurred an acceleration o CO

2injection activity in Permian Basin

elds. Today, operators inject more than 1.6 billion cubic eet per day o

naturally-sourced CO2

into Permian Basin oil elds to produce 170,000 barrelso incremental oil per day rom dozens o elds.


Location o Current CO2

EOR Projects and Pipeline Inrastructure


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But even with CO2

sources just a ew hundred miles away, the cost o delivering and injecting the CO2

is signicant.Industry has spent more than $1 billion on 2,200 miles o CO

2transmission and distribution pipeline inrastructure

in support o CO2

ooding in the Permian Basin. Typically, it costs $0.25-0.75 per thousand cubic eet to transportCO

2to West Texas elds rom the sources to the north. With a substantial CO

2pipeline and distribution inrastructure

in place, Permian Basin operators have spread the costs among several large elds, and the inrastructure in these

anchor elds in turn has helped reduce the cost o delivered CO2 to smaller elds in the basin. Still, analysts haveestimated that there is as much as 500 million cubic eet (25,974 metric tons) per day o pent-up demand or CO2

inthe basin rom oil eld operators seeking to implement economic CO

2EOR projects. Additional natural CO

2resource

has been discovered in the Arizona-New Mexico region and may be developed i the economics remain avorable.To the east, Denbury Resources, a Plano, Texas-based independent, is developing a similar inrastructure inMississippi, Louisiana, and southeastern Texas. Denbury owns a large natural CO

2resource at Jackson Dome,

Mississippi, which it describes as the largest CO2

resource east o the Mississippi River. Jackson Dome already eedsCO

2to EOR projects Denbury operates in Mississippi and Louisiana. Denbury plans to build a major extension rom

the southern terminus o its existing CO2

pipeline in Louisiana to deliver CO2

or injection at the Hastings Field inTexas. The company is also negotiating with industrial plants along the pipeline route, including our proposedgasiication plants ed by coal or petroleum coke, to secure additional supplies o captured anthropogenic

(man-made) CO2 or EOR projects in all three states.

Anthropogenic CO2

SourcesMuch discussion has centered on methods to reduce or eliminate CO

2emissions rom industrial sources due to

concerns over CO2

as a greenhouse gas. Prominent in this discussion are concepts to capture and saely andpermanently store anthropogenic CO

2in underground ormations, a process known as sequestration. In CO

2EOR

projects, all o the injected CO2

either remains sequestered underground or is produced and re-injected in asubsequent project, making the notion o using captured anthropogenic CO

2or EOR in places ar removed rom

natural sources o CO2

a likely possibility. Companies have already launched several examples o this approach.

For years, ExxonMobil Corp. has sold CO2 rom its La Barge, Wyoming gas processing acility to area oil producers or usein CO

2EOR projects (see map). The company currently captures 4 million metric tons o CO

2per year or this purpose.

Another major CO

2EOR project using industrially sourced CO

2is located at Weyburn oil eld, a Williston basin reservoir

just across the U.S. border in Saskatchewan, Canada. EnCana Corp., a Canadian company, injects about 95 million cubiceet (4,935 metric tons) per day o CO

2into Weyburn, a 55-year-old eld, to recover an incremental 130 million barrels o

oil via miscible or near-miscible displacement. The CO2

is sourced rom the lignite-red Dakota Gasication Companysynthetic uels plant in North Dakota, and delivered via a 205-mile pipeline. EnCana estimates that as much as 585 billioncubic eet (30 million metric tons) o CO

2will be permanently sequestered underground through the project, while

boosting the synuels plants revenues by about $30 million per year and extending the Weyburn elds lie by20 to 25 years.

Other industrially sourced CO2 EOR projects are in the ofngas well. Independent producers Sandridge Energy Inc. andOccidental Petroleum Corp. are developing a $1.1 billionnatural gas processing plant in West Texas that will captureabout 265 billion cubic eet (13.5 million metric tons) o CO

2

per year or use in CO2

EOR operations. Proposals to captureCO

2rom coal-red power plants, ethanol plants and other

industrial processes, and use it to supply EOR projects, arebeing considered or unding in a number o states.


Conversions

1 metric ton o CO2

equals 545 cubic meters at standardconditions o 14.7 psi and 70 F

1 metric ton o CO2

equals 19.25 thousand cubic eet (Mc)at standard conditions o 14.7 psi and 70 F

The average American car emits about seven metric tonso CO

2per year


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US CO2

EOR DemographicsProduction rom all United States CO

2EOR projects grew to 240,000 barrels

per day in 2008, according to the Oil & Gas Journals biennial survey. CO2

EOR production has jumped signicantly since the early 1980s (see graph).At the same time, the demographics o CO2

EOR operators have changed.Prior to the early 1990s, almost all CO

2injection was undertaken by a small

group o major oil companiesAmerada Hess, Amoco, ARCO, Chevron,

Exxon, Mobil, Shell, and Texaco. A proactive technology transer programled by DOEs National Energy Technology Laboratory in the 1990s helpedto transer their CO

2development concepts to the rest o the industry. That

eort, together with a shit in major company investment overseas, led to

the current situation where independent producers dominate the roster oCO

2EOR operators (see table).

The SACROC Unit, where commercial CO2

EOR got its start, is now in the

hands o an independent. Kinder Morgan CO2 Company, which is thesecond largest producer o oil in Texas and one o the nations largestowners and transporters o CO

2, has more than tripled SACROC production

since acquiring a majority interest in the unit in 2000.

One o the most active CO2

EOR operators is another independent producer,

Occidental Petroleum (Oxy). Oxy operates more than hal o the current CO2

oods in the Permian Basin and is one o the dominant producers o CO2

EORoil, and the largest oil producer in Texas.

Major U.S. CO2

Operators (OGJ Biennial EOR Survey 2008)

CompanyMiscibleProjects

LocationsIncrementalProduction(MBO/D*)

Occidental 29 TX, NM 90.2

Hess 6 TX 25.3

Kinder Morgan 1 TX 24.2

Chevron 4 CO, TX, NM 21.3

Denbury Resources 13 MS, LA 17.8

Merit Energy 7 WY, OK 13.6

ExxonMobil 2 TX, UT 11.7

Anadarko 4 WY 9.0

Whiting Petroleum 3 TX, OK 6.9

ConocoPhillips 2 TX, NM 5.5

12 otherindependents

28 TX, OK. UT, KS, MI 14.9

Total 99 240.4

* thousand barrels o oil per day

A proactive technology

transer program led by

NETL in the 1990s helped

to transer their CO2

development concepts to

the rest o the industry.



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CO2

EOR Economics

Implementing a CO2

EOR project is a capital-intensive undertaking. It involves drilling or reworking wells to serve as

both injectors and producers, installing a CO2

recycle plant and corrosion resistant eld production inrastructure, andlaying CO

2gathering and transportation pipelines. Generally, however, the single largest project cost is the purchase

o CO2. As such, operators strive to optimize and reduce the cost o its purchase and injection wherever possible.

Higher oil prices in recent years have signicantly improvedthe economics o CO

2EOR. However, oil eld costs have

also increased sharply, reducing the economic margin

essential or justiying this oil recovery option to operatorswho still see it as bearing signicant risk. Both capitaland operating costs or an EOR project can vary over arange, and the value o CO

2behaves as a commodity,

priced at pressure, pipeline quality, and accessibility, so it is

important or an operator to understand how these actorsmight change. Total CO

2costs (both purchase price and

recycle costs) can amount to 25 to 50 percent o the costper barrel o oil produced. In addition to the high up-rontcapital costs o a CO

2supply/injection/recycling scheme,

the initial CO2

injection volume must be purchased well in

advance o the onset o incremental production. Hence,the return on investment or CO

2EOR tends to be low,

with a gradual, long-term payout.

Illustrative Costs and Economics o a CO2

EOR Project

Oil Price ($/Barrel) $70

Gravity/Basis Dierentials, Royalties andProduction Taxes

($15)

Net Wellhead Revenues ($/Barrel) $55

Capital Cost Amortization ($5 to $10)

CO2

Costs (@ $2/Mc or purchase;$0.70/Mc or recycle)

($15)

Well/Lease Operations and Maintenance ($10 to $15)

Economic Margin, Pre-Tax ($/Barrel) $15 to $25

U.S. CO2

EOR Production



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Given the signicant ront-end investment in wells, recycle equipment, andCO

2, the time delay in achieving an incremental oil production response,

and the potential risk o unexpected geologic heterogeneity signicantlyreducing the expected response, CO

2EOR is still considered to be a risky

investment by many operators, particularly in areas and reservoirs where it

has not been implemented previously. Oil reservoirs with higher capital costrequirements and less avorable ratios o CO

2-injected-to-incremental-oil-

produced will not achieve an economically justiable return on investmentwithout advanced, high-efciency CO

2EOR technology and/or scal/tax

incentives or storing CO2.

Its Future Potential

While CO2

EOR has demonstrated signiicant success over nearly our

decades, signicant potential remains or additional growth in productionrom this process. This potential is urther enhanced by the possibility o

using captured anthropogenic CO2

in elds that are good candidates orCO

2EOR but ar rom natural CO

2source reservoirs.

CO2

EOR has increased recovery rom some oil reservoirs by an additional4 to 15 percentage points over primary and secondary recovery eorts thatcan account typically or about 30 to 35 percent o OOIP. However, some pilotprojects have reported incremental recovery o as much as 22 percent, and

studies have suggested that new game-changing technology innovationsthat bolster the efciency o CO

2oods or enhance geophysical mapping o

residual oil pockets could push total ultimate oil recovery in some reservoirsto more than 60 percent o OOIP. CO

2EOR currently is responsible or about

4 percent o U.S. oil production, displaying a long-term growth trendthat stands in stark contrast to the long-term decline trend or U.S. oilproduction overall.

Production Outlook

In its 2009 Annual Energy Outlook the Department o Energys EnergyInormation Administration (EIA) notes that the long-term decline in U.S.

crude oil production has slowed over the past ew years as drilling activityresponded to higher oil prices. Looking out to 2030, EIA orecasts thatoverall U.S. onshore oil production will increase to 3.8 million barrels perday rom 2.9 million barrels per day in 2007, due in part to the increased

application o CO2

EOR (see graph). This increase helps boost Lower 48oil production high enough to oset a attening o the growth curve rom

Signicant potentialremains or additional

growth in oil production

rom this process.



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deepwater oil production. EIAs assessment assumesthat anthropogenic CO

2will be available at a cost

rom just under $1 to just over $3 per Mc, deliveredto the eld.

The projected rapid take-up o new technology,coupled with higher oil prices, could make a big

dierence in the outlook or CO2EORs contribution

to uture U.S. oil production. Certainly, the volumeo stranded oil let behind in U.S. reservoirsater conventional primary and second recovery

techniques is massiveas much as two-thirds oall the oil discovered in the United States resides inthis category (see remaining oil pie chart). However,laboratory tests, and a ew selected eld projects

show that signiicant increases in CO2

EOR oilrecovery efciency are possible.

Domestic crude oil production by source 1990-2030

(million barrels per day)

Large volumes o domestic oil remain stranded ater primary/secondary recovery.



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16


A 2009 study by Advanced Resources International (ARI) or DOE assessedthe role that best practices CO

2EOR technologies could play in U.S. oil

recovery. ARI noted that introducing best practices technology to regionswhere it is currently not yet applied, lowering risks by conducting research,

pilot tests and ield demonstrations in geologically challenging ields,

providing state production tax incentives, ederal investment tax credits,and royalty relie, and establishing low-cost, reliable, CO

2supplies, could

result in an additional 85 billion barrels o technically recoverable oil romthe 400 billion barrels o oil remaining in large reservoirs across 11 basins.

However, many actors play a role in the suitability and economics o

CO2

EOR applicationsnot the least o which are the price o oil and thecost and availability o CO

2. Consequently, there can be a substantial gap

between a technically recoverable resource and a proven reserve volumebooked to an oil companys balance sheet. Still, the study points to the

signiicant potential o CO2 EOR to contribute to the nations uture oilsupply. Increasing the volume o technically recoverable domestic crude oilcould help reduce the Nations trade decit and enhance national energysecurity by reducing oil imports, add high-paying domestic jobs rom the

direct and indirect economic eects o increased domestic oil productionand help to revitalize state economies and increase ederal and staterevenues via royalties, and corporate income taxes.


Potential Technically

Recoverable

Incremental Oil

with best practices

CO2

EOR Technology


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Tax IncentivesIt is important to recognize that much o the CO

2EOR development that has

occurred in the U.S. might not have happened (or might not have happenedas quickly) without the introduction o tax credits and other scal incentivesto help oset the large nancial risks. As a means to help boost domestic oilproduction, the ederal tax code has had some sort o incentive or tertiaryrecovery since 1979, when crude oil was still under ederal price controls.Incentives were codied with the U.S. Federal EOR Tax Incentive in 1986, andCO

2EOR production growth subsequently grew rapidly. This incentive is a

15 percent tax credit that applies to all costs associated with installing a CO2

ood, the purchase cost o CO2, and CO

2injection costs.

In addition, eight states have introduced some orm o tertiary oil productiontax incentives related to the value o the incremental oil produced. Texas,which produces more than 80 percent o all U.S. CO

2EOR oil, provides a

severance tax exemption on all the oil produced rom a CO2-ooded reservoir.

CO2

EOR and SequestrationBeyond its potential to augment U.S. oil production, CO

2EOR is getting

intensive scrutiny by industry, government, and environmental organizationsor its potential or permanently storing CO

2. The thinking goes that CO

2EOR

can add value by maximizing oil recovery while at the same time oering abridge to a reduced carbon emissions uture. CO

2EOR eectively reduces the

cost o sequestering CO2

by earning revenues or the CO2

emitter rom sales

o CO2 to oil producers.

Many experts look to geologic sequestration as one o the best alternativesor dealing with carbon emissions. The CO

2EOR industry is an industry

with a proven track record o saely injecting CO2

into geologic ormations.EOR operations account or 9 million metric tons o carbon, equivalent toabout 80 percent o the industrial use o CO

2, every year. Although about

20 percent o CO2

used in EOR comes rom natural gas processing plants,the majority used or EOR comes rom natural underground sources anddoes not represent a net reduction in CO

2emissions. However, industrial

carbon capture and storage (CCS) oers the potential to signicantly alterthis situation.

Because o the cost o naturally sourced CO

2roughly $10-15 per metric

tona CO2

ood operator seeks to recycle as much as possible to minimizeuture purchases o the gas. All o the injected CO

2is retained within the

subsurace ormation ater a project has ended or recycled to subsequentprojects. Ater years o experience with CO

2oods, oil and gas operators

are condent that the CO2

let in the ground when oil production ends andwells are shut in will stay permanently stored there, assuming the wells areproperly plugged and abandoned.

The CO2EOR industry

is an industry with

a proven track record

o saely injecting

CO2

into geologic

ormations.



18/32

EOR could be an enabling

catalyst or large-scale

sequestration eforts.

18


One major oil industry operation that provides an example o suchpermanence is StatoilHydros Sleipner CO

2project in the North Sea o

Norway. The company is developing a large gas eld and must strip outCO

2rom the produced gas stream that is about 9 percent CO

2by volume.

Norways imposition o a tax on emitted carbon o $200 per metric

tonlater reduced to $140 per metric tonled StatoilHydro to compressthe captured CO

2and inject it into a deep saltwater ormation below the

seabed. The project, initiated in 1996, required an $80 million investmentbut has resulted in a tax savings o $55 million per year. Regular monitoringo the subsurace shows that the ormation is retaining the injected CO

2.

CO

2EOR technology and equipment needs parallel those envisioned

or sequestration, with similar surace inrastructure and wells, similarhandling o supercritical (high pressure/low temperature) CO

2, and

comparable subsurace simulation and characterization tools (well logs,three-dimensional (3-D) seismic, petrophysical analysis, etc.). The biggestdierences between the two are intent (minimizing CO

2use in EOR vs.

maximizing it or sequestration) and regulatory concerns (monitoring,verication, and accounting o the CO

2over the very long term).

Sequestration Potential in Oil ReservoirsWhat is the potential or sequestration o CO

2rom EOR operations? The

total volume o CO2

consumed by U.S. CO2

EOR to date has been about11 trillion cubic eet (560 million metric tons). That pales in comparison withtotal U.S. CO

2emissions rom industrial sources alone o about 100 trillion

cubic eet (5,090 million metric tons) per year. However, that does not mean

that the potential demand or CO2 or EOR will be insignicant; EOR couldbe an enabling catalyst or larger scale sequestration eorts.For example, a study by Montana Tech University ound that CO

2ooding o

Montanas Elm Coulee and Cedar Creek oil elds could result in the recoveryo 666 million barrels o incremental oil and the storage o 2.1 trillion cubiceet (109 million metric tons) o CO

2. All o the CO

2required or the ood

could be supplied by a nearby, coal-red power plant, and would equateto 7 years o the plants CO

2emissions. Furthermore, installation o a

pipeline and CO2

capture equipment or the project could provide the basicinrastructure or subsequent storage o CO

2in other oil elds and in saline

ormations and unmineable coal seams elsewhere in the state.

A comparison o two maps in the National Energy Technology LaboratorysCarbon Sequestration Atlas o the United States and Canada showsconsiderable overlap o the respective regional capacities or CO

2storage

in oil and natural gas elds and the major sources o CO2

emissions.

DOEs Regional Carbon Sequestration Partnership Initiative is the worlds mostcomprehensive eld program dedicated to the assessment and validationo carbon sequestration technologies in saline ormations, oil elds and



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19


CO2

Storage Resource Estimates

by Regional Carbon Sequestration

Partnership (RCSP) orOil and Gas Reservoirs

RCSPBillion

Metric Tons

Trillion

Cubic Feet

BSCSP* 1.5 29

MGSC* 0.4 8

MRCSP* 8.4 165

PCOR* 24.1 473

SECARB* 31.1 611

SWP* 65.0 1,277

WESTCARB* 7.7 151

TOTAL 138 2,714

North American oil feld distribution and calculated capacities

North American CO2

source distribution

Source: Carbon Sequestration Atlas o theUnited States and Canada, DOE/Ofce o

Fossil Energy/NETL, November 2008.


* RCSPs:

BSCSPBig Sky Carbon SequestrationPartnership

MGSCMidwest Geological SequestrationConsortium

MRCSPMidwest Regional CarbonSequestration Partnership

PCORPlains CO2

Reduction Partnership

SECARBSoutheast Regional CarbonSequestration Partnership

SWPSouthwest Partnership on CarbonSequestration

WESTCARBWest Coast Regional CarbonSequestration Partnership


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20


coals seams. DOE has been leading the eorts o the RCSPs to identiy thevolumes o carbon dioxide that could be stored in oil felds throughout theUnited States and Canada (see table).

The RCSPs are carrying out DOE-unded R&D ield projects designed to

validate and develop the potential or carbon capture and storage withintheir respective areas. A number o these projects combine CO2

storage withEOR. Ten feld projects are being supported throughout the United Statesand Canada. Seven o the projects have completed injection operationswhile three are injecting with plans to complete injection by the end o 2010.

The Midwest Geological Sequestration Consortium (MGSC) has evaluatedthe potential or CO

2storage in a sandstone oil reservoir in the Loudon

feld o Fayette, Co., Illinois, and is currently conducting another test in theSugar Creek feld near Madisonville, Kentucky and a third injection test inMumord Hills, Indiana. The Southeast Regional Sequestration Partnership(SECARB) is testing the potential or CO

2storage in Denburys Cranfeld Unit

near Natchez, Mississippi. The Plains Carbon Dioxide Reduction Partnership(PCOR) continues to carry out research associated with monitoring the ateo CO

2in a pinnacle ree in Northeastern Alberta. Other RCSPs projects

are in the Aneth Field in Utah; Permian Basin in Texas; the Williston Basinin North Dakota. The DOE also supports Encanas Weyburn project inSaskatchewan, Canada. Details about these feld projects can be oundonline at (http://www.netl.doe.gov/technologies/carbon_seq/index.html).A 2008 study by INTEK or DOE sought to test the economics o a potentiallinkage between the most likely candidate CO

2EOR reservoirs and their most

likely matching industrial CO2

sources. The study concluded that as much as30 trillion cubic eet o CO

2or 5 billion cubic eet per day at peak rates o

injectioncould ultimately be stored under this scenario, with a resulting

incremental increase in U.S. oil production o 5.5 billion barrels over 25 years.

Another study carried out by Advanced Resources International (ARI) orDOE-NETL concluded that CO

2EOR could provide a large, value-added

market or the sale o CO2

emissions rom new coal-fred power plantsabout 7.5 billion metric tons between now and 2030. It puts the value othat market at $260 billion.

Sales o captured CO2

emissions would help deray some o the costs oinstalling and operating CCS technology. These sales, in turn, could supportearly market entry o as many as 49 one-gigawatt installations o CCStechnology in the coal-fred power sector, according to the ARI study.

At the same time, concluded ARI, the ensuing CO2

EOR boom would unlockan additional 39-48 billion barrels o oil prior to 2030, while building aCO

2transportation inrastructure suitable or subsequent transport o

CO2

or sequestration in deep saline ormationswhich are likely to havethe biggest ultimate CO

2storage potential o all underground options.

The synergies between CO2

EOR and CO2

sequestration may be strongenough to help both eorts happen aster. And there are clear energy,environmental, and economic benefts or America in that kind o uture.



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R&D Objective (Perormer)

Evaluate and enhance carbon

dioxide ooding through sweepimprovement (Louisiana State).

ImproveCO2

ooding sweep using

CO2

gels (SBIR-RTA Systems Inc.)

ConductCO2

injection tests in

the Citronelle oileld in Mobile

County, AL to improve the

reliability o computer simulations

o oil yield rom CO2-EOR and

calculations o sequestration

capacity (University o Alabama

at Birmingham).

Determinetheeconomicandtechnical easibility o using CO

2

miscible ooding to recover oil in

a Lansing-Kansas City ormation

oileld in central Kansas (U. Kansas).

Employmolecularmodeling

and experiments to design

inexpensive, environmentally

benign, CO2-soluble compounds

that can decrease the mobility

o CO2

at reservoir conditions

(U. Pittsburgh).

Developaneuralnetworkmodelor CO

2EOR (University o Louisiana

at Laayette).

Developanovel,lowcost

method to install geophones

or CO2

monitoring (SBIR-Impact

Technologies).

21


What DOE is Doing

The Department o Energys Petroleum R&D Program aims to reducethe technology and cost barriers to increasing recovery rom mature

conventional oil reservoirs. There is also a signiicant e ort targetingunconventional oil resources such as extra heavy oil, oil and tar sands,oil shale, and oil in unconventional reservoirs (like the ractured BakkenShale o North Dakota).

Several trends highlight the need or continued research into ways toimprove recovery rom conventional domestic oil reservoirs.

Energydemandcontinuestogrow,andtheneedtoslowthegrowthinoil

imports or economic and energy security reasons remains strong.

Onshoredomesticoilproductionisdeclining,buttherearesignicantamounts

o oil let in conventional reservoirs in mature oil elds.

Economicextractionoftheseresourceswillrequireresearchtoprovidefora

better understanding o the geologic nature o these reservoirs as well as newtechnologies or cost-eectively producing the oil. Yet the operators that are

largely responsible or onshore domestic oil production are or the most partindependent producers who do not invest in R&D.

NETL is investigating the potential or recovering incremental oil

rom the Citronelle Field in Alabama using carbon dioxide EOR.The irst stage is developing an improved understanding o the

geology using state-o-the-art interpretation techniques. Fields like

Citronelle can demonstrate the potential or recovering domestic oil

using carbon dioxide captured rom industrial sources.



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22


The need or ederal investment in scientic data collection and technologydevelopment is driven by the ollowing acts:

Whileenhancedoilrecoveryhasbeensuccessfullyappliedinsomeareaswhere

circumstances are avorable (e.g., Permian Basin), in many other areas perceived

risk keeps it just beyond reach. The development and demonstration o newEOR technologies and new ways to apply existing EOR technologies can help

to accelerate its application.

InmatureeldsthatarethetargetsofEOR,smallproducersfacechallengesthat

are unique to their situationlow productivity wells, high water cuts, aginginrastructure and tight regulatory constraints. These operations are oten low

margin and are not targeted by the larger service companies R&D eorts.

Currently there are 26 unded projects in petroleum R&D portion o NETLsprogram that have either just been completed or are scheduled to continue

through 2012. O these, seven projects are directed at problems relatedspecically to CO

2

EOR. In addition to these extramural projects, an eortunded through the program instituted by Section 999 o the Energy PolicyAct o 2005 aims to evaluate the potential or near-miscible CO

2ooding

in midcontinent reservoirs where circumstances preclude re-pressuring tominimum miscibility pressure. Another project is looking at ways to increasethe viscosity o injected CO

2to improve sweep efciency.

Together, these projects orm a portolio that is balanced and responsive to theissues acing operators. The data, technologies and tools developed throughthis portolio will help industry make decisions and optimize operations in

ways that will advance the goal o environmentally sustainable CO2

EOR.

NETL is demonstrating carbon dioxide

ooding EOR in the Hall-Gurney feld in

Russell, Kansas, using carbon dioxide

recovered rom a nearby ethanol plant.


Cross-section through the pilot test area o the Citronelle Field shows the challenge o geologiccomplexity in felds where CO

2ooding is being considered. Well B-19-10 #2 is the CO

2injection well.


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23


The potential o

CO2

EOR is not so

much a matter o

whether but o

when.


Whats Next?

The potential impact o CO2

EOR is not so much a matter o whetherbut o when. The process works, there is plenty o residual oil in many

reservoirs, and there is plenty o carbon dioxide available rom a varietyo sources. The speed with which CO

2EOR is applied to recover the oil

in U.S. oilelds, will depend on economic decisions that in turn dependprimarily on the:

Priceofoil

Costofcapital(interestrates)andcapital

inrastructure construction (drilling, gasprocessing, pipelines)

Costofcarbonemissiontaxes,orconversely,

the value o carbon sequestration credits

Costofcarbondioxidecapturefromanthropogenic sources

Pilotprojectresults

Speedoftechnologyadvancementand

dissemination

These actors can be hard to predict.Nevertheless, as the regulatory picture begins

to become clearer, more CO2

EOR projects arelikely to be implemented.

There is also an important public relations and regulatory aspect to thespeed with which CO

2ooding spreads beyond its current boundaries.

Although the places CO2

ooding will be applied are by denition placeswhere oil has already been produced and people are amiliar with oil

production activities, in some o these areas the concept o carbon dioxideinjection is not well understood. It is important that stakeholders (citizens,investors, regulators, landowners, elected representatives) understand the

science behind CO2

ooding, so that decisions can be made based on acts.Some potential stakeholder questions are listed below.

Wont the carbon dioxide be released when the oil is produced?

No. Any CO2 that is produced along with oil and natural gas is captured andre-injected. The company operating the EOR project bought the CO

2and

expects to re-inject it i any is produced, to maximize its value. It only hasvalue when it is used to remove oil rom the rock ormation underground,

so there is a strong economic motivation to collect it or re-injection, eitherin the current project or another. When a CO

2EOR ood is nished, the CO

2

that remains underground, stays there. Monitoring eorts can be put into

place to make sure that is true.

Insulated CO2

source

wellhead


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24



Wont the carbon dioxide leak rom underground and causeproblems?

No, this is very unlikely. For well-selected, designed and managed geologicalstorage sites, experts calculate that the rock ormations are likely to retainover 99 percent o the injected CO

2

or over 1000 years. At the Weyburn

Project in Weyburn, Saskatchewan, Canada has determined that thelikelihood o any CO

2release is less than one percent in 5,000 years. There is a

strong economic motivation or the operating company to ully understandthe geology o the subsurace reservoir beore it makes a multi-million

dollar investment in inrastructure and pumps millions o dollars o CO2

underground. The investors want to know where it is going more thananyone does.

How about the pipelines on the surace, cant they leak?

Yes, any pipeline can leak. But just as with natural gas pipelines (whichcriss-cross the nation and are commonplace in practically every residential

neighborhood), there is a strong economic (and regulatory) motivation oroperators to keep them rom leaking.

How about the old wells in an old oileld, cant they leak?

Yes, but again there is a strong economic (and regulatory) motivationto make sure that the casing in these wells is still strong, that it is wellcemented in place, and that there is no opportunity or communication

between the deep ormation being ooded and any shallower ormationsat lower pressure. The loss o CO

2

to unintended places costs money andreduces the efciency o the process. Every year, natural gas is reinjectedat high pressure into gas storage elds around the country, particularly in

northeastern states. These elds, many o which are located in populatedareas, are developed in the same way that CO

2projects are developed,

by careully checking old wells to prevent leakage, monitoring them aterinjection has begun, and repairing or replacing them i necessary.

But isnt the carbon dioxide that is being injectedsupercritical? That sounds dangerous.

Supercritical is a term physicists use to dene the physical state o a substance;

it has no negative connotation. Carbon dioxide can exist as a gas (what youexhale with each breath), as a liquid (similar to the liquid nitrogen that youremember rom science class experiments), and as a solid (the dry ice thatyou sometimes nd keeping ice cream cold), depending on its temperature

and pressure. At high pressure and low temperatureas a supercriticaluidCO

2has properties midway between a gas and a liquid. I the conditions

changed to room temperature and pressure, the supercritical CO2

uid would

shit to the gas phase and dissipate, just as dry ice does.


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25



Cant injecting carbon dioxide into the old oil elds causeearthquakes?

No. Oil companies have been injecting CO2

in West Texas or decades andhave not caused any earthquakes. Large volumes o water have beenre-injected into oil ields all over the country without any evidence o

the injection having caused earthquakes.

There are a number o places online where additional inormation can beobtained about CO

2EOR and CO

2sequestration.

Some useful links:National Energy Technology Laboratory (http://www.netl.doe.gov/index.html)

Natural Resources Deense Council (http://www.nrdc.org/energy/eor.pd)

Kinder Morgan (http://www.kne.com/business/co2/)

Oxy (http://www.oxy.com/Pages/deault.aspx)

Denbury Resources (http://www.denbury.com/)

Enhanced Oil Recovery Institute (http://eori.gg.uwyo.edu/)


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26



Glossary

API gravity Crude oil is commonly reerred to in terms o its API

gravity, a reerence established by the American Petroleum Institute

that relates the density o a crude to the density o water at standardconditions. The API scale inverts and increases the numerical value ospecic gravity (e.g., oil with a specic gravity o 0.93 relative to water

has an API gravity o 20, while an oil with a specic gravity o 0.83 hasan API gravity o 40). A light, less dense crude with lighter weighthydrocarbons has a higher API number than a heavy crude oil. I acrudes API gravity is less than 10, it is heavier than water and will not

loat. Mathematically API gravity has no units, but is reerred to asdegrees API.

areal sweep Percentage o the total oil reservoir geographical area

which is within the area being swept o oil by a displacing uid, as inthe case o a water ood or carbon dioxide ood. Combined with the

verticalsweep, it provides a measure o the total volumetricsweep othe reservoir.

carbonate rock Sedimentary rock ormed primarily rom calciumcarbonate (CaCO

3) deposited in a marine environment; most

commonly limestone. Many o the carbon dioxide oods ound in

the Permian Basin o West Texas are in oil reservoirs in carbonateormations deposited during the Permian Period.

casing The tubular steel pipe that is used to line the wellbore as a wellis drilled. Casing is cemented in place by pumping cement down theinside o the casing and up the annulus between the outside o the

casing and the wall o the hole. It comes in a variety o diameters andas a well is drilled, smaller and smaller diameter strings o casing areplaced concentrically into the well and cemented in place, orming aprotective barrier between deep and shallow rock ormations.

density A measure o how much mass is contained in a unit volume o

a substance. It can be expressed in kilograms per cubic meter, grams

per cubic centimeter, pounds per gallon, or other units. Oil densityexpressed relative to that o water, and natural gas density expressedrelative to that o air, at standard pressure and temperature conditions,

is termed oil specic gravity and gas specic gravity.

API gravity = 141.5 131.5SG

where SG = specic gravity at 60 F

SGoil

=density o oil

density o water


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27


heterogeneous Consisting o dissimilar elements or parts; nothomogeneous. Heterogeneous rock ormations are not uniorm interms o their properties but instead vary widely both vertically andlaterally. This variation can result in poor sweep efciency as reservoirs

are looded with water or carbon dioxide, and less than optimal

recovery o remaining oil.

high water cut When an increasingly high percentage o the totalluid produced rom a well is water rather than oil (perhaps as highas 99 percent or greater). This tends to be the case as water loods

reach the end o their economic lie.

hydrocarbon pore volume The pore volume o a porous, sedimentaryrock is that portion o a unit volume o the rock that is pore spacerather than solid mineral constitutents (oten in the range o 10, 20 or

30 percent). The pore volume is naturally lled with uids: water, oiland gas. The hydrocarbon pore volume is that portion that is lled withhydrocarbons, rather than water.

interacial tension A phenomenon at the surace separating twoimmiscible liquids caused by intermolecular orces. The tendency oan interace to contract in order to minimize the interacial area leads

to a state o tension. Reducing interacial tension allows uids to mixmore intimately and can allow a displacing uid to more eectivelymove a displaced uid.

light hydrocarbons Lower molecular weight hydrocarbons (ewercarbons). Methane (CH

4) is the lightest hydrocarbon. Other parafnic

series hydrocarbons (ethane, butane, propane, etc.) each successivelyhave one additional carbon atom. High density (low gravity) crude oilstypically contain molecules with many carbon atoms.

maniold A system o pipes and valves that allow or the comingling and/or redirection o owing uids rom many individual wells at a central

production processing acility.

metric ton Also reerred to as a tonne, is a measurement o mass equalto 1,000 kg or 2204.6 pounds, or approximately the mass o onecubic meter o water. A U.S. ton is a measurement o mass equal to2000 pounds. Carbon dioxide is oten measured in metric tons. One

metric ton o carbon dioxide is equal to a volume o 556.2 cubic meterso the gas at standard conditions o temperature and pressure.



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28


minimum miscibility pressure The minimum pressure at which a crudeoil will be miscible with carbon dioxide at reservoir temperature.

miscibility The condition where two luids can be mixed in all

proportions; where there is no interace between them.

original oil in place The volume o oil originally in place in a reservoirbeore production commences, expressed as a total volume at suraceconditions o temperature and pressure (typically in stock tank barrels

in the U.S.). Oil in place must not be conused with oil reserves, whichare the technically and economically recoverable portion o the oilvolume in the reservoir. Recovery actors or oil elds around the world

typically range between 10 and 60 percent o the original oil in place.

permeability The ability o a rock to allow uids (oil, water, and gas) to

ow through it by virtue o the interconnectivity o its internal porosity.Fluids move through reservoir rock and into a well due to a pressuregradient (higher pressure out in the reservoir compared to the pressureat the bottom o the well). Higher permeability rock will allow a higher

ow rate, all other things being equal. Permeability is a constant in theow equation or uid ow through porous media, with units known asDarcies.

primary production Oil production that is driven by the natural pressureo the reservoir, beore any energy is added through water injection

(secondary production or secondary recovery) or post-wateroodenhanced oil recovery processes like carbon dioxide injection (tertiaryrecovery).

reservoir The rock ormation and its uid contents o water, oil, and gasthat make up a hydrocarbon accumulation in the subsurace. An oil

reservoir generally is bounded by seals, either structural barriers likeaults or lithological barriers like low permeability rocks, that act to trapthe hydrocarbons and prevent their migration over geologic time.

residual oil The oil that remains in a reservoir ater primary, secondary or

tertiary production (or all three) has taken place. Typically expressed asa percentage o the pore volume.

reworking wells The act o re-entering a well bore ater the well has

been producing or some time, generally using a drilling or workoverrig, to eect repairs or otherwise enhance the ability o the well toproduce at commercial rates.



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29


sandstone A sedimentary rock composed mainly o sand-size mineralor rock grains. Sandstones can result rom a variety o depositionalenvironments and can exhibit a range o values or permeabilityand porosity. Most sandstone is composed o quartz and/or eldspar

because these are the most common minerals in the Earths crust.

secondary recovery Oil production that is driven by water injectionin a waterood.

supercritical conditions Combined conditions o temperature andpressure that place a substance at a point above its critical point.When in a supercritical state, a substance can exhibit properties o

both a liquid and a gas (e.g., it may diuse through solids like a gas,and dissolve materials like a liquid).

tertiary recovery Oil production that is post-waterood and driven byenhanced oil recovery (EOR) processes like carbon dioxide injection(other processes include chemical and thermal).

viscosity Measure o the internal resistance o a uid to being deormedby either shear stress or extensional stress. With common uids and

terminology, viscosity is though o as thickness (e.g., water is thin,having a lower viscosity, while honey or molasses is considered asthick, having a higher viscosity. Viscosity describes a uids internalresistance to ow and may be thought o as a measure o uid riction.

In general, heavier crudes are highly viscous and thus more difcult todisplace using a lower viscosity uid (like water, or carbon dioxide).

waterooding The practice o pumping (injecting) water into selectedwells in an oil ield, in order to sweep remaining oil rom the rockormation and push it towards producing wells were it can be pumped

to the surace. Waterlooding is typically (but not always) initiatedsome time ater a ield has been signiicantly depleted under theprimary production phase.

well pattern The pattern o wells in a eld; their location relative to each

other and the spacing (drainage area per well) that pattern implies.In a waterood or carbon dioxide ood, the pattern can also indicatethe ratio o injectors to producers and their relative position to oneanother.



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30


Contacts

Strategic Center for Natural Gas and Oil (SCNGO), NETL

Director, SCNGO

John R. [email protected]

Exploration & Production Technology Manager

Albert B. Yost II304-285-4479

[email protected]

Ultradeepwater and Unconventional ResourcesTechnology Manager

Roy [email protected]

Department of Energy Headquaters

Of ce o Oil and Gas Resource ConservationGuido Dehoratiis Jr.202-586-7296

[email protected]

Of ce o Future Oil and Gas Resources

Olayinka (Yinka) Ogunsola

[email protected]



31/32

Photo credits

Cover: wellhead (Denbury Resources), pump jack(NewsOK)

Page 6: pipeline (Kinder Morgan), wellhead (Kinder Morgan)

Page 7: plant (Hess Corp.), maniold (Denbury Resources), separator (Whiting Petroleum Corp.),

compressor (Steve Melzer)

Page 23: wellhead (Kinder Morgan)

Page 24: pipeline construction (Denbury Resources), wellhead (Denbury Resources),

maniold (Denbury Resources), dry ice (www.EduPic.net)

Page 25: plant (Denbury Resources)


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1450 Queen Avenue SWAlbany, OR 97321-2198

541-967-5892

2175 University Avenue South,Suite 201

Fairbanks, AK 99709907-452-2559

3610 Collins Ferry RoadP.O. Box 880

Morgantown, WV 26507-0880304-285-4764

626 Cochrans Mill Road

P.O. Box 10940Pittsburgh, PA 15236-0940

412-386-4687

13131 Dairy Ashord,Suite 225

Sugarland, TX 77478281-494-2516

WEBSITE: www.netl.doe.gov

CUSTOMER SERVICE: 1-800-553-7681

Documents

Small CO2 EOR Primer