Assessing potential impacts of CO2 upward migration on ...

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Assessing potential impacts of CO2 upward migration on drinking groundwater quality at the SECARB Phase

III early test site

GCCC Digital Publication Series #13-28

C. Yang S. D. Hovorka R. H. Trevino

Cited as: Yang, C., Hovorka, S.D., and Trevino, R.H., 2013, Assessing potential impacts of CO2 upward migration on drinking groundwater quality at the SECARB Phase III early test site: presented at the 2013 Carbon Storage RD Project Review Meeting, Pittsburgh, Pennsylvania, 20-22 August 2013. GCCC Digital Publication Series #13-28.

Keywords: Field study-Cranfield-MS; Monitoring-groundwater-USDW

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Assessing Potential Impacts of CO2 Upward Migration on Drinking Groundwater Quality at the SECARB Phase III Early Test Site

Changbing Yang, Susan Hovorka, Ramon Trevino

Gulf Coast Carbon Center, Bureau of Economic Geology, The University of Texas at Austin

10100 Burnet Rd., Austin, TX 78758, changbing.yang@beg.utexas.edu

1. Introduction

6. Results

This study was funded through the Southeastern Regional Carbon Sequestration Partnership’s (SECARB) Phase III research project by the

U.S. Department of Energy’s National Energy Technology Laboratory (DOE/NETL) under DE-FC26-05NT42590 and managed by the

Southern States Energy Board (SSEB). It was also partially funded by Water Research Foundation (Project No. 4265). We thank the

Denbury Resources Cranfield team and Denbury management for allowing us access to the field. Thanks are given to the Bureau of

Economic Geology research team, Bridget Scanlon, Pat, Mickler, J.P Nicot, Katherine Romanak, and Bob Reedy.

2. Cranfield shallow aquifer

Located 15 miles east

of Natchez, MS

Oil field was

discovered in 1940s

and abandoned in

Injection of CO2 for

EOR conducted since

Injection phase: inject CO2-saturated groundwater into target aquifer

Resting phase: let injected water react with aquifer sediments

Pulling phase: pump groundwater continuously to collect water samples

Yang, C., Samper, J., and Molinero, J., 2008. Inverse microbial and geochemical reactive transport models in porous media. Physics and Chemistry of the Earth, Parts A/B/C 33, 1026–1034.

Yang, C., Mickler, P. J., Reedy, R., Scanlon, B. R., Romanak, K. D., Nicot, J.-P., Hovorka, S. D., Trevino, R. H., and Larson, T., 2013. Single-well push-pull test for assessing potential impacts of CO2 leakage on groundwater quality in

a shallow Gulf Coast aquifer in Cranfield, Mississippi. International Journal of Greenhouse Gas Control, in press.

Yang, C., Romanak, K., Hovorka, S. D., Holt, R. M., Lindner, J., and Trevino, R., 2013. Near-surface monitoring of large-volume CO2 injection at Cranfield: Early field test of SECARB Phase III. SPE Journal 18, pp. 486–494.

4. Single-well push-pull test 3. Batch experiments

7. Concluding remarks

Results of batch experiments, the field controlled-release test, and

numerical modeling show that DIC and pH are sensitive to CO2 leakage

and may be used for detecting CO2 leakage at the Cranfield shallow

aquifer.

Dominant geochemical processes for ion mobilization may include

dissolution of carbonates and silicates and desorption/adsorption from

clay surfaces.

No obvious degradation in groundwater quality was observed in the batch

experiments and the field test.

Maximum concentrations of trace metals measured, such as As and Pb,

are much smaller than EPA-specified contamination levels.

The single-well push-pull test appears to be a convenient field-scale

controlled-release test for assessing potential impacts of CO2 leakage on

drinking groundwater resources.

The combined use of laboratory batch experiments, field-scale controlled-

release tests, and reactive-transport models provides a comprehensive

evaluation of potential impacts of CO2 leakage on groundwater chemistry.

Conducted to understand responses of

groundwater chemistry to CO2 leakage under

laboratory conditions

106 g of sedimentary samples and 420 ml

groundwater from Cranfield shallow aquifer

Bubbled with Ar for a week, then with CO2

for ~half year

Understanding potential impacts of CO2 upward migration on

underground drinking resources is a critical concern for geologic

carbon sequestration. A comprehensive groundwater study has

been conducted at the Cranfield shallow aquifer, Natchez, MS—

the SECARB Phase III early test site—using a combined

approach of laboratory batch experiment, single-well push-pull

test, and reactive-transport modeling to assess potential impacts

of upward migration of CO2 on groundwater quality.

Implementation:

Injection started : ~3,825 L water over 8 hours

Resting phase: ~55 hours

Pumping phase: ~15,142 L groundwater pumped out over ~11 hours

Onsite measurements

pH, alkalinity

conductivity

temperature

IC analysis

ICP-MS

analysis

DIC and stable

carbon isotope

of DIC

Water samples

5. Reactive-transport modeling

For this study we used CORE2D V4,

a code for modeling partly or fully

saturated water flow, heat transport,

and multicomponent reactive solute

transport under both local chemical

equilibrium and kinetic conditions.

Pros: easy to

do, low cost

disturbed

conditions

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Dissolution of silicates

Dissolution of carbonates

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1) Dissolution of carbonates

such as Ba, Mn, Sr

Mobilization of trace

metals dominated by

two mechanisms:

2) Desorption/adsorption

of metals such as As, Pb

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pH Alkalinity

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Dissolution of silicates

Dissolution of carbonates

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Modeled w/ surface complexes

2) Adsorption/desorption

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1) Carbonate dissolution Mobilization of

trace metals

Testing well

• Well was completed

with 2 PVC and

screened between

180 and 240 ft

• Depth of well: 240 ft

to surface

• Depth of water level:

90 ft to surface

12 field campaigns for groundwater sampling since August, 2008 On-site measurements: pH, temperature, alkalinity, water level

Lab analysis: Ag, Al, As, Ba, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Pb, Se, Zn, F-, Cl-, SO42-, Br-,

NO3-, PO4

3-, TOC, dissolved inorganic carbon (DIC), pH, alkalinity, VOC, 13C of DIC

Aquifer sediment

mineralogy analyzed

using XRD

Groundwater chemistry

dominated mainly by

silicate-mineral weathering

Testing well

Laboratory Scale

Field Scale

In order to interpret the batch experiment and the single-well push-pull

test in the field, we used a reactive-transport model for simulating

groundwater flow and solute transport coupled with geochemical

processes. The reactive-transport model consists of two sub-models: a

model of groundwater flow and solute transport, and a geochemical

model.

Groundwater-flow and solute-transport model: radius of the model domain is 25

m, and thickness is 7 m. The top and bottom boundaries are assumed to be no-

flow boundaries. Groundwater was injected into the aquifer through the testing

well during the injection phase and pumped out during the pulling phase.

Geochemical model: simulates geochemical processes (aqueous complexation,

mineral precipitation/dissolution, cation exchange reactions, and

adsorption/desorption) in the batch experiment and the push-pull test.

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