Challenges Due to Uncertainty with Class VI Permitting Due to Uncertainty with Class VI Permitting ... Jan 22-24, 2013 . GWPC 2013 Underground Injection Control Conference . ... and

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Challenges Due to Uncertainty with Class VI Permitting

Andrew Duguid and Philip Jagucki, Schlumberger Carbon Services Ryan Choquette, Tenaska, Inc

Jan 22-24, 2013 GWPC 2013 Underground Injection Control Conference

Outline

● Taylorville Energy Center (TEC) ● Burden of proof required to construct (Regulatory Uncertainty) ● Lowest USDW (Geologic Uncertainty) ● Well Design (Geologic Uncertainty) ● Infinite AoR (Regulatory, Planning and Design, and Geologic Uncertainty) ● Annular Pressure (Regulatory and Permitting Process Uncertainty) ● Summary

Taylorville Energy Center

A proposed 716-megawatt (gross) 602-MW (net) coal-fed Integrated Gasification Combined-Cycle power plant with Carbon Capture and Storage

Geologic Column

Geologic Unit Estimated Depth (feet)

Lowermost USDW 250 Secondary Confining Unit (New Albany Shale) 1800

Secondary Confining Unit (Maquoketa Shale) 2500

St. Peter Sandstone 3100 Primary Upper Confining Unit (Eau Claire Shale) 5000

Mount Simon Sandstone Injection Interval 5615

TD – Total Depth 7200 Lower Confining Unit (Basement Granite) 7200

Well Penetrations in the Area

● No wells penetrate to the Mt Simon in the vicinity of TEC

● The closest offset well

with modern logs and test data is in Decatur, IL (~30 miles away)

Burden of Proof to Construct?

In fields without existing wells that penetrate the entire column the requirements in the Class VI regulation would seem to require a stratigraphic test well. ● (3) Information on the geologic structure and hydrogeologic properties

of the proposed storage site and overlying formations, including: (iii) Data on the depth, areal extent, thickness, mineralogy, porosity,

permeability, and capillary pressure of the injection and confining zone(s); including geology/facies changes based on field data which may include geologic cores, outcrop data, seismic surveys, well logs, and names and lithologic descriptions;

(iv) Geomechanical information on fractures, stress, ductility, rock strength, and in situ fluid pressures within the confining zone(s);

● (6) Baseline geochemical data on subsurface formations, including all USDWs in the area of review;

Burden of Proof to Construct?

Instead of a strat well, the system can be engineered so that uncertainty in the data or lack of site-specific data prior to drilling can be overcome to receive a permit to construct. Overestimated AoR ● Conservative ● Based on four wells

instead of two ● Will be updated after

construction and prior to injection

Geologic Uncertainty

● Sparse data could lead to the St Peter Sand being the lowest USDW

● It is not necessary

or always possible to know for sure where the lowest USDW is prior to drilling

Handling Geologic Uncertainty Through Well Design

● Engineering multiple casing strings can be used to make up the “surface casing” and overcome uncertainty in the depth of the lowest USDW.

● Section 146.82 (b) (2) gives us

this flexibility. “Surface casing must extend through the base of the lowermost USDW and be cemented to the surface through the use of a single or multiple strings of casing and cement.”

Possible Infinite AoR

-60.96 m

-944.88 m ρu = 1003 kg/m3 Pu=8.69 MPa

Pif =19.38 MPa

-1905 m Pio = 19.62 MPa

ρi = 1135 kg/m3

St Peter Formation

Mt Simon Formation

Injectors

50 psi

100 psi

200 psi

300 psi

400 psi

500 psi

600 psi

Pressure Perturbation – Plan View

Distance, meters

2,000 × 2,000 m 6,560 × 6,560 ft

11 miles

9 miles 6 miles 4.6 miles

3.7 miles 3 miles 3 wells, each injecting

1 Million tonnes per year

Pressure perturbation at the end of 30 years of continuous injection

Pressure Perturbation

11 miles

9 miles

6 miles

4.6 miles

3.7 miles

3 miles

1.55 Miles 13.98 Miles

Infinite AoR -- Questions

● How are cut-off points set? ● Is the AoR a sensible

calculation in areas with no penetrations of the injection formation or caprock?

● Can an pressure-based

“asymptotic” AoR be used to look for penetrations and a CO2-based AoR be used for monitoring?

The Agency also recognizes that calculations may result in an asymptote, or that in some physical settings the formation pressure will contribute to an AOR that extends over great distances. Under current State and Federally implemented rules, the problem of infinite asymptotes has been addressed by setting cut-off points when the slope of the pressure curve flattens. It is not EPA's intent that operators "chase asymptotes" when no real potential endangerment resulting from the well exists. (Federal Register Vol. 53, No. 43, July 26, 1988)

§ 146.88 Injection well operating requirements– Annular Pressure

“The owner or operator must maintain on the annulus a pressure that exceeds the operating injection pressure, unless the Director determines that such requirement might harm the integrity of the well or endanger USDWs.”

Concerns

● May cause a leak in the casing ● May damage the cement isolation capacity ● May damage the surrounding formation

EXAMPLE ● Injection pressure at the top

of the well of 2000 psi ● Surface temperature of 50°f

and a gradient of 1°f per 100ft ● Annular fluid 10% KCl with

a gradient of 0.46 psi/ft ● Annular pressure 100 psi above

injection pressure at the top of the well

● A fracture pressure gradient of 0.8 psi/ft

● Injection depth 7000 ft ● Variable CO2 density and gradient

based on constant densities over 100-foot intervals calculated using REFPROP [Lemmon et al., 2007]

Annular Pressure

Summary

● Uncertainty comes in the UIC process comes from multiple sources: ―Geology ―Limited Existing Data ―Regulation ―Permitting Process

● Engineering design can be used address uncertainty by relying on: ―Flexibility In the Regulation ―Factor’s of Safety ―Robust Design