Case Study of a CO –EOR Storage...

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The Weyburn CO2 Monitoring and Storage Project Case Study of a CO2–EOR Storage Project

(R.J. Chalaturnyk & K.E. Durocher)

Type of reservoir: Fractured carbonate reservoir at Enhanced Oil Recovery site

Location: Near the City of Weyburn, Saskatchewan, Canada Size of injection: 22 million tons of CO2 Project duration: Approximately 25 years (for all phases) CO2 Supplier: Dakota Gasification located in Beulah, North Dakota, U.S.A. Project status: Active Total cost: US $23 Million Funding partners: Various, including the Governments of Canada, the US, and

the EU and industry: EnCana Corporation, SaskPower, Nexen Canada, TotalFina Elf, Chevron Texaco, BP, Dakota Gasification Co., TransAlta Utilities Corp. and the Engineering Advancement Association of Japan.

Contact: Michael Monea, Executive Director Petroleum Technology Research Centre [email protected]

Asia-Pacific Economic Cooperation B-1 Building Capacity for CO2 Capture and Storage in the APEC Region

OVERVIEW OF THE WEYBURN CO2 MONITORING AND STORAGE PROJECT

This CO2 monitoring and storage project was essentially a field-demonstration made possible by

EnCana’s CO2 enhanced oil recovery (EOR) project being carried out at its Weyburn Unit. Located in the

southeast corner of the province of Saskatchewan in Western Canada, the Weyburn Unit is a 180 km2 (70

square mile) oil field discovered in 1954. The Weyburn field is part of the large Williston sedimentary

basin that straddles Canada and the US (Figure 1).

Figure 1: Relationship between the Weyburn Site (red spot), System Model, Regional Study, Williston Basin, and geographic boundaries (courtesy Sask. Industry & Resources).


The Weyburn site straddles the Canada-US border near Weyburn Saskatchewan. Approximately 5000 tonnes/day of CO2 are injected into the field as part of an EOR project by EnCana Corporation.

Water flooding was initiated in 1964, and significant field development

including the use of horizontal wells was begun in 1991. In September

2000, EnCana initiated the first phase (Phase 1A) of a CO2 enhanced

oil recovery scheme in 18 inverted 9-spot patterns. The flood will be

rolled out in phases into a total of 75 patterns over the next 15 years

(Figure 2). It is anticipated that as much as 20 to 25 million tonnes of

CO2 will be injected into the Midale beds over the lifetime of the

project, some 25 years.

Figure 2: EnCana’s Weyburn Unit and the timing and extent of the CO2 flood (data courtesy EnCana

Corporation).


The Weyburn CO2 Monitoring and Storage Project began in July

2000, as a major research project to study geological storage of CO2.

The program was launched by the Petroleum Technology Research

Centre (PTRC) located in Regina, Saskatchewan, in close

collaboration with EnCana Resources of Calgary, Alberta. Phase I of

project was funded by fifteen sponsors from governments and

industry, among them Natural Resources Canada, United States

Department of Energy, Alberta Energy Research Institute,

Saskatchewan Industry and Resources, the European Community

and ten industrial sponsors in Canada, the US and Japan. The

project employed about 22 research and consulting organizations

and about seventy technical and project personnel. A comprehensive

summary of the project, including priorities, results, and

interpretations, can be found in Wilson and Monea (2004).

The Weyburn Unit has proven to be an exceptional natural laboratory for the study of CO2 storage, partly because of extensive historical field and well data available, abundant core material and accessibility to the site. The project has proven that CO2-EOR is an economically viable option for not only extending the lifetime of a producing field. It also has demonstrated that anthropogenic CO2 leakage from the reservoir and seepage to the surface is negligible.

The Weyburn Unit has proven to be an exceptional natural laboratory

for the study of CO2 storage, based in part on the extensive historical

field and well data available, abundant core material and accessibility

to the site. The Weyburn monitoring and storage project has proven

that CO2-EOR is an economically viable option for not only extending

the lifetime of a producing field, but that the prognosis for

anthropogenic CO2 leakage from the reservoir and seepage to the

surface is negligible.

CO CAPTURE AND TRANSPORT2 Carbon dioxide used during the injection process at Weyburn is derived from the Great Plains Synfuels

Plant (GPSP) near Beulah, North Dakota, USA. The GPSP is the only commercial-scale coal gasification

plant in the USA and has been in operation since 1984. The GPSP gasifies lignite coal using the Lurgi

process. As a result, economically important gases, liquids, and by-products, including CO2, are produced

for consumer and industrial markets.

In 2000, the CO2 capture and transport process was initiated. CO2 is captured using a cold methanol

wash. The CO2 is recovered, compressed to a supercritical state, and transported at approximately 95%

purity to the Weyburn site via a 325 km pipeline. The cost of the pipeline was approximately $100 million


USD. The GPSP sees revenues of approximately $30 million/year on its CO2 sales to the Weyburn

Project (Dakota Gasification Co. and International Energy Agency websites).

PLANNING FOR CO INJECTION2

The primary objective of the project was to investigate the concept of geological storage of greenhouse

gases, particularly CO2. The scope of work focused on understanding the mechanisms of CO2 distribution

and containment within the reservoir into which the CO2 is injected and the degree to which CO2 can be

permanently stored. The technology, design and operating know-how obtained by the initiative could then

be applied in screening and selecting other CO2 storage sites and in designing and implementing

successful CO2 storage projects worldwide.

A secondary objective was the application of economic realities to

such an undertaking by predicting the point at which a CO2 storage

project reaches its economic limit. The application of customized

economic models to the various storage scenarios helped in

assessing not only cases of CO2 storage in conjunction with EOR

operations but also of CO2 storage in non-EOR situations such as

saline aquifers. This could provide extensive CO2 storage potential

beyond that of depleting oil pools.

The ultimate deliverable from Phase 1 of this project was a credible

assessment of the permanent containment of injected CO2 as

determined by formal risk analysis techniques including long-term

predictive reservoir simulations. Risk assessment will continue into

Phase 2 of the project and the results will help answer questions by

regulatory bodies as to the security of large volume CO2 storage not

only in the Williston Basin but also at other sedimentary basins where

CO2 storage is contemplated.

Asia-Pacific Economic Cooperation Building Capacity for CO2 Capture and Sto

The study wasdesigned to addressthe potential of CO2storage as a long-termoption for combatingclimate change. Itssecondary objectivewas to predict theeconomic limits of CO2storage. Weyburn wasintended to become amodel process thatcould be used to selectand screen technology,design, and operationparameters for futureCO2 storage projectsworldwide.

B-5 rage in the APEC Region

CHARACTERIZATION OF THE STORAGE FORMATION

The principal aim of geological characterization for the Weyburn site was to assess the integrity of the

geological container encompassing the Weyburn Unit for effective long-term storage of CO2. Data

obtained during this assessment was used to develop a three dimensional system model that includes

features and properties of an area extending 10 km beyond the CO2 flood extent. This provides the

geological framework for the risk assessment of the long-term fate of CO2 injected into the subsurface at

Weyburn (Figure 3).

Figure 3: Geological, hydrogeological, and structural model of the Weyburn site (courtesy Sask. Industry & Resources).


The Weyburn Oil Pool is a giant oilfield containing about 1.4 billion barrels of oil in place in limestone and

dolostone (Midale Beds) of Mississippian age. Carbonates of the Midale reservoir occur at about 1.5 km

in depth in the North-eastern portion of the Williston Basin. Williston is a sedimentary basin broadly

similar to the Illinois and Michigan basins of North America and numerous intracratonic basins that occur

elsewhere around the world.

Characterization of the Weyburn geological system for CO2 storage

targeted the delineation of primary and secondary trapping

mechanisms and the identification of any potential pathways of

preferential CO2 migration. To place these components within a

regional, or basinal, context, the geological framework was constructed

for a region extending 200 x 200 km around the Weyburn Field that

includes portions of Saskatchewan, North Dakota and Montana. Large-

scale studies such as this more effectively reveal basin hydrogeological

flow characteristics and the underlying tectonic framework that can

greatly influence depositional patterns of sedimentary packages and

fracture development.

The development of a comprehensive geological model for use in risk

assessment required a focused and highly integrated, multidisciplinary

approach. Lithostratigraphic mapping identified over 140 individual

surfaces from the Precambrian basement to ground surface. The

lithostratigraphic units were used to define larger flow packages, or

hydrostratigraphic units, that were mapped and characterized using

The Weyburn oil pool contains about 1.4 million barrels in place in limestone and dolostone. Carbonates occur at a depth of 1.5 km in the North-easterd potion of the Basin. Geological characterization of the Weyburn system targeted the delineation of primary and secondary trapping mechanisms and potential pathways for CO2 migration. A region extending 200 x 200 km around the Weyburn field was analyzed in order to understand the regional context for these parameters. In addition, lithostratigraphic mapping was used to define fluid behaviour within the basin.

extensive data analysis to provide fundamental information on fluid

behaviour within the basin as required by performance assessment.

Much of the 2000 km of 2D seismic data processed to refine the characterization of subsurface features

and basement tectonics were integrated with high-resolution aeromagnetic data to augment fracture and

regional fault delineation. Detailed geological studies performed on primary seals (those in contact with

the reservoir) and secondary seals (barriers to flow higher in the stratigraphic column) include core

descriptions, petrography, isotope geochemistry and fluid inclusion studies. Shallow hydrogeological

surveys defined the distribution and continuity of potable aquifers in near-surface sediments of the study

region. Analysis of remotely sensed imagery was used to determine whether structural elements

observed in the deep subsurface were related to linear surface features identified through air photo and

satellite imagery.


Other specialized studies undertaken included obtaining cores from selected strata above the reservoir

for petrophysical measurements, till sampling for soil gas characterization, and shallow aquifer

demarcation. Integration of these diverse data has provided a coherent and representative geological

model that can be tailored for use in risk assessment.

The geological setting at the Weyburn Field is highly suitable for long-term subsurface storage of CO2.

Primary seals enclosing the reservoir (including the overlying Midale Evaporite and a highly anhydritized

altered zone and the underlying Frobisher Evaporite) are observed to be highly competent. The seals

have very rare discontinuities. Most of the discontinuities formed shortly after deposition and are

completely healed with no visual evidence of fluid conductance. In addition, as part of the primary sealing

package, the Lower Watrous Formation forms a regionally extensive aquitard that effectively separates a

deep hydrogeological system (including the Midale Beds) from a shallower hydrogeological system

(Figure 4).

Characteristics of the Weyburn Midale Beds storage site that help to make it idea for long-term CO2 storage: • Location: approximately 1500 meters below the surface; • Thickness: Generally 20 meters thick; • Composition: lower, more voluminous Midale Vuggy beds are dominantly calcitic, upper

Midale Marly units are dominantly dolomitic, variable amounts of anhydrite and silicate minerals;

• Porosity: ranges from 5 to 35%, with the highest porosities in the Midale Marly; • Formation water composition: characterized as brine, with TDS values of approximately

50,000 to 100,000 mg/L; • Cap rock characteristics: several meters of anhydrite with rare discontinuities, overlain by

several thick and regionally extensive aquitards;

Overlying the Watrous Formation is over 1 km of predominantly clastic strata that contain several thick

and regionally extensive aquitards providing additional barriers to upward fluid migration. Aquifers

present within the shallow hydrogeological regime may have high flow velocities (m/yr) and are important

for scenario analysis of CO2 leakage. Within the Midale Beds however, low flow velocities (cm/yr) and

favourable flow directions suggest formation water is unlikely to be an effective transport mechanism for

dissolved CO2.


Figure 4: Reservoir characteristics of the Midale Beds of the Weyburn Unit, including bounding seals of the Midale and Frobisher Evaporite, and overlying Jurassic Watrous Formation (courtesy EnCana

Corporation).

Fracture zones and regional tectonic elements are present within the study region, yet none were found

to exhibit evidence of fluid conductance or influence over hydrogeological components. Salt dissolution

also has occurred within the risk assessment study region and may have induced fracturing of overlying

rocks, although with no apparent compromise of the geologic container. Overall, one of the most

important results from this work is the development of a tremendous geoscientific dataset pertinent to

understanding geological storage of CO2 in the Williston Basin and other sedimentary basins.


STORAGE POTENTIAL OF THE WEYBURN MIDALE BEDS The objectives within this area of the project were to demonstrate that the maximum CO2 storage capacity

that can be achieved physically and economically at a geological storage site can be estimated. Initial

predictions of how the CO2 flood would progress were based on flow simulations using an existing

reservoir model that had been constructed using the well-bore geology from the dense network of wells in

the Weyburn field (Figure 5).

Figure 5: Fence diagram of predicted CO2 saturation distribution for a 9 pattern reservoir simulation after 26 months of CO2 injection (courtesy Alberta Research Council).


GEM, a multi-phase, multi-component compositional reservoir

simulation model, was used to predict the CO2 storage capacity in the

Weyburn Unit reservoir. The approach taken in modeling the size and

complexity of 75 EOR patterns was to start with fine-grid single-pattern

simulations and end with a coarse-grid 75-pattern simulation. The

reservoir simulation model was validated by both lab-scale and field-

scale simulations. Predictions were then made for the CO2 distribution

and storage capacity at the end of EOR (estimated for the year 2033).

The final CO2 distribution provided the initial conditions for the risk

analysis model of the geosphere to assess the potential CO2 leakage

and migration, including from near wellbore zones. The CO2 inventory

and CO2 distribution at the end of EOR, for the entire 75 patterns, was

modeled following EnCana’s field operating guidelines as closely as

possible. It was found that an estimated of 23.3 million tonnes (MT) of

CO2 can be stored in the reservoir at the end of EOR. Of that figure,

7.08 MT (30.5%) would be stored in the gaseous phase, 10.25 MT

(44.2%) in oleic phase and 5.87 MT (25.3%) in aqueous phase (Figure

6). There will not be a free supercritical CO2 gas phase present in the

reservoir after 5000 years.

Flow simulations of the CO2 flood using an existing reservoir model was initially conducted. The model was based on well-bore geology from the dense network of wells. A multi-phase, multi-component compositional reservoir simulation model was used to predict the CO2 storage capacity in the Weyburn Unit reservoir.

Figure 6: Distribution of injected CO2 across the 75 injection patters for the Weyburn Unit, including the final distribution at the end of EOR (Base EOR Case). Data courtesy Alberta Research Council.


A geochemical model was used to provide a preliminary assessment

of the amount of CO2 that would be stored in the reservoir through a

variety of geochemical trapping mechanisms. The geochemical

modeling used formation and injection fluid compositions, detailed

mineralogical assessments of each of the major flow units in the

reservoir, and evaluation of mineral kinetic data. Integrating these

results over the entire reservoir yields a total of approximately 45.15

MT with 22.65 MT, 0.25 MT and 22.25 MT of CO2 potentially stored

through solubility, ionic and mineralogical trapping mechanisms,

respectively. The most critical assumptions in this calculation are that

there is sufficient supercritical CO2 for reaction in each of the flow units

and that complete/significant reaction of the silicate minerals will occur

over 5,000 years.

It was found that an estimated 45.15 million tonnes of CO2 can be stored in the reservoir, of which 22.65 MT would be stored in through solubility, 0.25 MT through ionic and 22.25 MT through mineralogical trapping mechanisms. An economic model based on the predicted CO2 storage and EOR performance was applied economic constraints to CO2 storage. The economic model has the capability to calculate CO2 capture, transportation and storage costs in addition to the conventional economic evaluation of an EOR process.

With the prediction of CO2 storage capacities and EOR performance,

an economic model was used to apply economic constraints to the

CO2 storage cases. This storage economic model has the capability to

calculate CO2 capture, transportation and storage costs in addition to

the conventional economic evaluation of an EOR process. The model

can be run either for stand-alone CO2 storage options (e.g. depleted

oil or gas reservoirs, saline aquifers, etc.) or storage in conjunction

with CO2 EOR projects. The objective of the storage economics model

was to guide geological storage decisions where estimates of the

maximum amount of CO2 that can be physically stored are required,

as well as how much of that CO2 is actually economically stored, under

different gas credits assumptions.


MONITORING A variety of seismic and geochemical sampling methods have been used to monitor the CO2 injection

process and characterize the reservoir between boreholes. Seismic imaging of the CO2 in the subsurface

has been accomplished primarily by time-lapse 3D multi-component surface seismic reflection imaging

complemented by time-lapse and static borehole (VSP and crosswell) seismic surveys and passive

seismic monitoring. Rock/fluid property measurements, combined with reservoir simulation and production

history matching including seismic constraints, were used to calibrate the seismic observations to known

CO2 injection volumes and to update the reservoir simulation model mentioned above.

The geochemistry of produced oil, gas, and brine has been regularly monitored and analyzed for a broad

range of chemical and isotopic parameters to infer injection-related chemical processes within the

reservoir and to track the path of injected CO2. This analytical work is supported by model calculations

and laboratory studies on geochemical reactions. Soil gas sampling is designed to detect injected CO2

that may have escaped from the reservoir and percolated to the surface.

The ability to seismically detect changes in the Weyburn reservoir

induced by CO2 injection was clearly demonstrated at the Weyburn site

(Figure 7). Corroborating evidence provided by rock property

measurements, log-based synthetic seismic modelling, and reservoir

simulation/ production history matching all indicate that the primary

effect observed by P-wave seismic monitoring is CO2 saturation There

are also smaller off-trend anomalies that suggest that channelling of the

CO2 is occurring in some areas. There is no evidence from either the

time-lapse seismic or the soil gas sampling for migration of measurable

amounts of CO2 into the overburden or to the surface.

CO2 flood movement was predicted using flow simulations in an existing reservoir model. Monitoring was based on a number of seismic and geochemical sampling methods. It was possible to seismically detect changes in the Weyburn reservoir. The observations made by seismic sampling were corroborated through rock property measurements, log-based synthetic seismic modeling, and reservoir simulation/ production history matching.

Geochemical monitoring has identified two important reservoir chemical

reactions associated with the injection process: CO2 dissolution (CO2 +

H2O ↔ H2CO3) and carbonate mineral dissolution (H2CO3 + CaCO3 ↔

Ca2+ + 2HCO3-). The path of injected CO2 can be traced geochemically

due to distinct isotopic signatures associated with the injected CO2

(δ13Cinjected value of –21 ‰) versus the reservoir pre-injection HCO3 (δ13C

= -6 to –20 ‰). Reaction of CO2 with the formation water results in a

more acidic water (i.e., lower pH) with increased total inorganic carbon

content (TIC, lowering the δ13C of HCO3).


The more acidic brine drives carbonate mineral dissolution, resulting in higher pH, δ13C of HCO3, and

increased [Mg2+], [Ca2+], TIC, and alkalinity in the water (Figure 8).

Figure 7: Comparison of time-lapse seismic results and reservoir simulations after approximately 2 years of CO2 injection. Anomalies are associated with the highest concentrations of CO2 in the reservoir. These anomalies are spatially associated with CO2 injector wells (after D. White, Geological Survey of Canada).


CO2 seepage to the surface was measured using relatively inexpensive soil gas surveys. Anomalously high helium and radon concentrations can indicate possible pathways for CO2 migration to the biosphere. Soil and groundwater surveys, often considered the last line of defence, are very important to the public due to possible water and soil contamination issues. Soil anomalies will not be found for successful CO2 storage projects.

Injected CO2 seepage to the surface should be measurable using

relatively inexpensive soil gas surveys. To this end, a number of soil

gases (e.g., CO2, H2S, He, Rn) concentrations and fluxes were

measured from pre-injection through to the end of Phase 1.

Anomalous CO2 fluxes and concentrations were correlative with

higher biogenic activity near depressions and lineaments.

Helium and radon concentrations, where anomalously high, can be

correlated with a deeper source than the soil, and possible locate

structures that are communicating with deeper stratigraphic units.

Such structures may be potential pathways for CO2 migration to the

biosphere.

Soil and shallow groundwater surveys are often viewed as a “last line of defence” and of high public

interest as potable water contamination and soil chemistry issues for local rural residents. Ironically, the

most successful CO2 storage project will mean that a measurable soil anomaly will never be found. Future

surveys at the Weyburn site may concentrate on local and regional lineament surveys, abandoned well

surveys, and the detection and quantification of different chemical compounds, such as mercaptans.

Figure 8: Geochemical anomalies (warmer colours) associated with carbonate mineral (predominantly calcite) dissolution after approximately 30 months of CO2 injection: total alkalinity and Ca2+

concentrations in produced brine. Sampled wells shown by black dots (courtesy the University of Calgary).

LONG-TERM PREDICTIONS

Identification and evaluation of the risks associated with geological storage of CO2 within the Weyburn

reservoir and assessment of its ability to securely store CO2 was of paramount importance. Risk assessment embodies the overall process of risk analysis and risk evaluation. Risk analysis involves

the systematic use of project information to identify sources of potential CO2 leakage and to estimate their

probability and magnitude. Risk evaluation examines the acceptability of these risks considering the


needs, issues and concerns of stakeholders. These are described in more detail in Module 9:

Performance Assessment: Planning for and Mitigating Potential Leakage and Remediation Issues.

Geological storage of CO2 is a developing technology and as

such, does not have a sufficient knowledge base from which to

extract historical data on all leakage risks. Consequently, the

risk analyses conducted in Phase I of the Project focused on

assessing storage system performance or behaviour to increase

the understanding of crucial processes and will form a critical

component of the final risk assessment in Phase II. This risk

assessment process will ultimately mature into a framework that

considers social, economic and political factors associated with

geological storage; evaluates the risks associated with a

geological storage reservoir; and assesses the effectiveness of

remedial actions that can be taken to minimize both near-term

and long-term probabilities and consequences arising from CO2

leakage. Equally important, this process will provide the basis

for communication about the existence, nature, form, magnitude

and acceptability of risks associated with the storage of CO2.

As geological storage of CO2 is a developing technology, it does not have a sufficient knowledge base from which to extract historical data on all leakage risks. Consequently, the risk analyses conducted focused on assessing storage system performance to increase the understanding of crucial processes and will form a critical component of the final risk assessment. This risk assessment process will ultimately mature into a framework that takes into consideration all important risk assessment and evaluation factors. Sensitivity analyses illustrated that parameters with uncertain values were greatly influencing estimates of EOR performance. Probabilistic risk assessment supplemented the original analysis to cope with parameter uncertainty.

Sensitivity analyses conducted using the sophisticated Eclipse

300 (E300) reservoir simulator and other models invariably

pointed out that estimates of EOR performance were strongly

influenced by some parameters whose values were quite

uncertain. Consequently, a supplementary program of

probabilistic risk assessment was adopted to make available a

systematic method that could cope with parameter uncertainty. A

generalized performance assessment model, CQUESTRA-I

(CQ-I), employing simplifying assumptions and a compartmental

model approach, and characterized by analytical solutions, was

developed for the probabilistic risk analyses. Early CQ-I

simulations confirmed that wells and their integrity strongly

influence leakage from the storage reservoir; that the Midale

Marly permeability controls CO2 leakage rates into boreholes;

and that storage within the geosphere is greatly enhanced where

there is aquifer fluid flow above about 1 m/yr in any upper aquifer

zones (e.g., Manville Aquifer).


Synthesis of all available well information within the injection area of the project provided the performance

assessment studies with ranges of well types and their associated transport properties. Cement

degradation models incorporating sulphate attack, mechanical fatigue, carbonation and leaching have

provided wellbore cement hydraulic conductivities for most well types. For historical injection and

production pressures within aging wellbores, modeling has predicted minimal impact on the sealing

capability of the wellbores over the life of the EOR project.

To build confidence in the performance assessment predictions provided by CQ-I and E300, a focused

benchmarking study was undertaken. For the simple “No Wells” case, E300 and CQ-1 simulations have

shown that the dominant CO2 mass transfer process within the Midale Beds beyond the 75 EOR patterns

is almost exclusively intra-bed and that no CO2 ever reaches the Watrous Formation or higher formations

(Figure 9).

Figure 9: For the “no wells” case of the Benchmarking Study, CO2 migration from the predictions using

the Eclipse 300 simulator. CQUESTRTA-1 simulations provided similar results for CO2 migration prediction (data courtesy Monitor Scientific).


For the “Annulus Well” case where flow is restricted to the annulus of the wellbore, the simulation

approach adopted by CQ-I and E300 are significantly different, but demonstrate reasonable agreement

with regard to mass of CO2 leaking through the borehole annulus. E300 predicts 0.11% and CQ-1

predicts 0.35% after 5,000 years. Results for the “Borehole Well” case assuming complete degradation

of an abandonment plug leading to creation of an open borehole has shown that mass flux of CO2 into the

wellbores is likely controlled by the Marly permeability.

Performance assessment studies to date have shown clear support for the conclusion reached within the

geological characterization studies – the geological setting at the Weyburn Field is highly suitable for

long-term subsurface storage of CO2. These studies have highlighted the significant capacity of the

geosphere region surrounding the reservoir to effectively store CO2 and prevent its migration to the

biosphere. The performance assessment studies have also clearly identified wellbores as a potential,

primary CO2 leakage pathway to the biosphere in the Weyburn Field.

KEY RESULTS • Enhanced Oil Recovery (EOR) using an anthropogenic CO2 sweep is an economically viable option

to extend the lifetime of a producing oilfield near the end of its primary or secondary production

cycle.

• The detailed geological, hydrogeological, and structural model has been established as a crucial

step. All relevant data can be inserted and assessed given this framework.

• The production history, and world-class database associated with a well-integrated monitoring and

modeling program has allowed careful consideration of the interaction of injected CO2 with in situ oil,

brine, and rock.

• Time lapse seismic surveys and geochemical monitoring has proven to be effective tools to monitor

the location and influence of injected supercritical CO2 on the reservoir components.

• Short-term reservoir models are constrained by historical production data and monitoring programs.

Long-term predictive models show reservoir storage capacity for injected CO2 will meet and exceed

expected injection volumes.

• Long-term risk assessment suggests that movement of injected CO2 in the subsurface will be

dominated by intra-bed lateral migration, and that little or no injected CO2 will reach the surface over

the next 5000 years.


BIBLIOGRAPHY Baubron, J-C., 2004. Soil gas velocity and flux modeling using long term Rn monitoring; a new tool for

deep CO2 escape detection; GHGT-7: Seventh International Conference on Greenhouse Gas Control Technologies, Vancouver, B.C., September 2004.

Durocher, K., Bloch, J., Perkins, E., Hutcheon, I., Shevalier, M., Mayer, B., and Gunter, W., 2004. Mineralogical characterization of the Weyburn reservoir, Saskatchewan, Canada: Are mineral reactions driving injected CO2 storage; GHGT-7: Seventh International Conference on Greenhouse Gas Control Technologies, Vancouver, B.C., September 2004.

Jimenez, J.A., Chalaturnyk, R.J., and Whittaker, S.G., 2004. A mechanical earth model for the Weyburn CO2 Monitoring and Storage project and its relevance to long-term performance assessment; GHGT-7: Seventh International Conference on Greenhouse Gas Control Technologies, Vancouver, B.C., September 2004.

Khan, D.K., and Rostron, B.J., 2004. Regional hydrogeological investigation around the IEA Weyburn

CO2 monitoring and storage project site; GHGT-7: Seventh International Conference on Greenhouse Gas Control Technologies, Vancouver, B.C., September 2004.

Moreno, F.J., Chalaturnyk, R.J., and Jimenez, J.A., 2004. Methodology for assessing integrity of

bounding seals (wells and caprock) for geological storage of CO2; GHGT-7: Seventh International Conference on Greenhouse Gas Control Technologies, Vancouver, B.C., September 2004.

Perkins, E., 2004. Geochemical modeling and monitoring: The IEA GHG Weyburn CO2 monitoring and

storage project; GHGT-7: Seventh International Conference on Greenhouse Gas Control Technologies, Vancouver, B.C., September 2004.

White, D., 2004. Geophysical monitoring and verification of CO2 movement: Results from the IEA Weyburn CO2 monitoring and storage project; GHGT-7: Seventh International Conference on Greenhouse Gas Control Technologies, Vancouver, B.C., September 2004.

White, D.J., Burrowes, G., Davis, T., Hajnal, Z., Hirsche, K., Hutcheon, I., Majer, E., Rostron B., and

Whittaker, S., 2004. Greenhouse gas sequestration in abandoned oil reservoirs: The International Energy Agency Weyburn pilot project; GSA Today: v. 14, No. 7, p. 4–10.

Whittaker, S.G., 2004. Investigating geological storage of greenhouse gases in Southeastern

Saskatchewan: The IEA Weyburn CO2 monitoring and storage project; in Summary of Investigations 2004, Saskatchewan Industry and Resources, v. 1.

Wilson, M. and Monea, M. 2004. IEA GHG Weyburn CO2 Monitoring & Storage Project Summary Report

2000-2004; GHGT-7: Seventh International Conference on Greenhouse Gas Control Technologies, Vancouver, B.C., September 2004, v. 3, 273 p.

Zhou, W., Stenhouse, M.J., Arthur, R., Whittaker, S.G., Law, D.H.-S., Chalaturnyk, R.J., and Jazrawi, W.,

2004. The IEA Weyburn CO2 Monitoring And Storage Project - Modeling of the long-term migration of CO2 from Weyburn; GHGT-7: Seventh International Conference on Greenhouse Gas Control Technologies, Vancouver, B.C., September 2004.


INTERNET LINKS The Weyburn CO2-EOR Project: http://www.co2captureandstorage.info/project_specific.php4?project_id=70 http://www.ptrc.ca/ http://www.encana.ca/index.html Coal gasification process at Beulah, North Dakota: http://www.co2captureandstorage.info/project_specific.php4?project_id=119 http://www.dakotagas.com/company/process.htm


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