The Abandoned Works Program, SW Ontario: identifying the sources of

leaking formation waters and natural gases

J. Potter, M. Skuce, F.J. Longstaffe, T. Carter, L. Fortner

The University of Western Ontario

The Ministry of Natural Resources

The Problem:Potentially >22,000 leaking wells in the

province that have not been fully recorded The Abandoned Works Program was set up by the Ministry

to confront this problem and establish a remediation program

Plugging a well that has good records can cost ~$10,000 but “problematic” wells have been known to exceed the $250,000 mark before successfully sealed

Abandoned Works

Which formation is source of the sulfur water/oil/gas?

Where do plugs need to be set to confine the aquifers?

Which formations are competent for setting of plugs?

Where has casing corrosion likely occurred?

SURFACE SEDIMENTS

SHALE

SALTY WATER IN SANDSTONE

SHALE

LIMESTONE

SANDSTONE

DOLOMITE

SHALE

LIMESTONE

PRODUCTION FORMATION

SHALE

OIL/GAS

INTERMEDIATE CASING

PRODUCTION CASING

PRODUC TION TUBING

ANNULUS

PACKER

TYPICAL WELL CONSTRUCTION

HOLE

CEMENT SHEATH

PERFORATIONS

FRESH WATER

SURFACE CASING

SURFACE SEDIMENTS

SHALE

SALTY WATER IN SANDSTONE

SHALE

LIMESTONE

SANDSTONE

DOLOMITE

SHALE

LIMESTONE

PRODUCTION FORMATION

SHALE

OIL/GAS

INTERMEDIATE CASING

PRODUCTION CASING

PRODUC TION TUBING

ANNULUS

PACKER

TYPICAL WELL CONSTRUCTION

HOLE

CEMENT SHEATH

PERFORATIONS

FRESH WATER

SURFAC E CASING

The Aim:Identifying fluids from specific horizons

are there any differences between stratigraphic levels are any differences geographically related can we differentiate between these reservoirs and what

they may show with regard to origin

Characterise the geochemical and isotopic compositions of natural gases and waters from SW Ontario reservoirs and aquifers, and use this knowledge to determine the source(s) of gases/waters leaking from abandoned wells.

Analyses being done:Geochemical analysis of waters

O and H-isotopes (water)S and O-isotopes (sulphate)

C-isotopes (DIC)Sr in water

C and H-isotopes (natural gas)

(from Singer, Cheng, and Scafe 1997)

Water well records - MOE

Petroleum Well Records - MNR

What can stable isotopes of natural gases tell us?

Utilising methane isotope results can provide us with a glimpse of how these gases were formed and subsequently

altered

Whiticar (1999)now d2H

What can stable isotopes of natural gases tell us?

Methane and higher hydrocarbon isotopic compositions can be modified by a number of processes (main processes being): degree of thermogenic “cooking” mixing of reservoirs microbial methanogenesis microbial oxidation

The d13C and d2H differences between methane (C1) and higher hydrocarbons (C2+) can provide valuable information including those diagnostic features that we are looking for and.. how they were formed and subsequently altered due to

mixing, fluid infiltration and microbial interaction

-300 -280 -260 -240 -220 -200 -180 -160 -140 -120 -100

-60.0

-55.0

-50.0

-45.0

-40.0

-35.0

-30.0

-25.0

-20.0

A2 carb

A1 carb

Guelph

Thorold

Grimsby

Whirlpool

Trenton

Black River

Cambrian

d2HCH4 ‰ (VSMOW)

d13C

CH4

‰ (VP

DB)

Carbon- and hydrogen-isotope results of methane – all results

incr. microbial influence

incr. thermogenic maturity

-300 -280 -260 -240 -220 -200 -180 -160 -140 -120 -100

-260

-240

-220

-200

-180

-160

-140

-120

-100

A2

A1

Guelph

Thorold

Grimsby

Whirlpool

Trenton

Black River

Cambrian

d2HCH4 ‰ (VSMOW)

d2HC2H

6 ‰ (VSMOW)

Hydrogen-isotope results of methane and ethane

incr. microbial influence?

incr. thermogenic maturity

Carbon- and hydrogen-isotope results of methane Cambrian

-300 -280 -260 -240 -220 -200 -180 -160 -140 -120 -100

-60.0

-55.0

-50.0

-45.0

-40.0

-35.0

-30.0

-25.0

-20.0

Cambrian - Oxford

Cambrian - Kent

Cambrian - Perth

d2HCH4 ‰ (VSMOW)

d13C

CH4

‰ (VP

DB)

? T008045

-300 -280 -260 -240 -220 -200 -180 -160 -140 -120 -100

-60.0

-55.0

-50.0

-45.0

-40.0

-35.0

-30.0

-25.0

-20.0

Black River - Lambton

Black River - Essex

d2HCH4 ‰ (VSMOW)

d13C

CH4

‰ (VP

DB)

Carbon- and hydrogen-isotope results of methane Lower Ordovician Black River

-300 -280 -260 -240 -220 -200 -180 -160 -140 -120 -100

-60.0

-55.0

-50.0

-45.0

-40.0

-35.0

-30.0

-25.0

-20.0

Trenton - Lambton

Trenton - Essex

Trenton - Kent

Trenton - Elgin

d2HCH4 ‰ (VSMOW)

d13C

CH4

‰ (VP

DB)

Carbon- and hydrogen-isotope results of methane Middle Ordovician Trenton

-280 -260 -240 -220 -200 -180 -160 -140 -120 -100

-60.0

-55.0

-50.0

-45.0

-40.0

-35.0

-30.0

-25.0

-20.0

Whirlpool - Haldimand

d2HCH4 ‰ (VSMOW)

d13C

CH4

‰ (VP

DB)

Carbon- and hydrogen-isotope results of methane Lower Silurian Whirlpool

-300.0 -280.0 -260.0 -240.0 -220.0 -200.0 -180.0 -160.0 -140.0 -120.0 -100.0

-60.0

-55.0

-50.0

-45.0

-40.0

-35.0

-30.0

-25.0

-20.0

Grimsby - Norfolk

Grimsby - Elgin

Grimsby - Thorold - Norfolk

d2HCH4 ‰ (VSMOW)

d13C

CH4

‰ (VP

DB)

Carbon- and hydrogen-isotope results of methane Lower Silurian Grimsby

-300.0 -280.0 -260.0 -240.0 -220.0 -200.0 -180.0 -160.0 -140.0 -120.0 -100.0

-60.0

-55.0

-50.0

-45.0

-40.0

-35.0

-30.0

-25.0

-20.0

Thorold - SW Norfolk

Thorold - NE Norfolk

d2HCH4 ‰ (VSMOW)

d13C

CH4

‰ (VP

DB)

Carbon- and hydrogen-isotope results of methane Lower-Mid Silurian Thorold

-300 -280 -260 -240 -220 -200 -180 -160 -140 -120 -100

-60.0

-55.0

-50.0

-45.0

-40.0

-35.0

-30.0

-25.0

-20.0

Guelph - Lambton - Sombra

Guelph - Lambton - Enniskillen

Guelph - Huron - Goderich

Guelph - Huron - South Huron

d2HCH4 ‰ (VSMOW)

d13C

CH4

‰ (VP

DB)

Carbon- and hydrogen-isotope results of methane – Middle Silurian Guelph

-280 -260 -240 -220 -200 -180 -160 -140 -120 -100

-60.0

-55.0

-50.0

-45.0

-40.0

-35.0

-30.0

-25.0

-20.0

A1 - Lambton

A1 - Kent

d2HCH4 ‰ (VSMOW)

d13C

CH4

‰ (VP

DB)

Carbon- and hydrogen-isotope results of methane Upper Silurian A1 unit

-300 -280 -260 -240 -220 -200 -180 -160 -140 -120 -100

-60.0

-55.0

-50.0

-45.0

-40.0

-35.0

-30.0

-25.0

-20.0

A2 -Lambton

A2 - Kent

d2HCH4 ‰ (VSMOW)

d13C

CH4

‰ (VP

DB)

Carbon- and hydrogen-isotope results of methane Upper Silurian A2 unit

-300 -280 -260 -240 -220 -200 -180 -160 -140 -120 -100

-60

-55

-50

-45

-40

-35

-30

-25

-20

Unknown - Vienna

A2 carb

A1 carb

Guelph

Thorold

Grimsby

Whirlpool

Trenton

Black River

Cambrian

d2HCH4 ‰ (VSMOW)

d13C

CH4

‰ (VP

DB)

Our first unknown sample! The $250,000 question.

Lowest d13CCH4 observed so far.Mix of near surface microbial CH4 + thermogenic?

d13CCO2 = -20‰

microbial CH4 fermentation – terrestrial

microbial CH4 CO2 –reduction -

mainly marine

incr. maturity

-300 -280 -260 -240 -220 -200 -180 -160 -140 -120 -100

-260

-240

-220

-200

-180

-160

-140

-120

-100

Unknown

A2

A1

Guelph

Thorold

Grimsby

Whirlpool

Trenton

Black River

Cambrian

d2HCH4 ‰ (VSMOW)

d2HC2H

6 ‰ (VSMOW)

Hydrogen-isotope results of methane and ethane

incr. maturity

Microbial input?

d2H results for unknown outside all fields

-220.0 -200.0 -180.0 -160.0 -140.0 -120.0 -100.0

-220.0

-200.0

-180.0

-160.0

-140.0

-120.0

-100.0

ThoroldGrimsbyTrentonBlack RiverCambrian

d2HCH4 ‰ (VSMOW)

d2HC2H

6 ‰ (VSMOW)

Inverse trend

Normal trend

1:1

Hydrogen-isotope results for methane vs ethane in the Black River and Trenton pools

In most thermogenic gas reservoirs d2HCH4 < d2HC2H6 but here we observe a diagnostic feature where d2HCH4 ~ d2HC2H6

A series of diagnostic features have so far been identified:

The Cambrian gases are generally the most thermogenically matureWith decreasing age of reservoir, in general, a thermogenic trend to less mature gases is observed

The Ordovician Black River and Trenton natural gas samples have distinct d2H values for CH4 and C2H6 that are easily recognisable

- they are = or slightly inversed.

The Silurian Whirlpool and Thorold samples are immature with respect to the Grimsby reservoir of the same age in the same area.

- they also sit slightly off the thermogenic trend- more data required – geographically controlled?

SUMMARY OF ISOTOPIC DATA FOR THE NATURAL GASES

A series of diagnostic features have so far been identified:

SUMMARY OF ISOTOPIC DATA FOR THE NATURAL GASES

The Silurian A1 Salina Group samples in the Lambton area overlap the Guelph samples from this region but can be distinguished by lower d13CC2H6 values. Samples from the Kent area are very different, sitting on the thermogenic trend

The large Silurian Guelph sample dataset clearly shows a microbial input in samples from the Lambton area. Samples from Huron are also distinguishable from other reservoirs but do not show quite a shift to low d13CCH4 values

- distinctly high d13CC2H6 and d13CC3H8 values relative to other reservoirs

The Silurian A2 Salina Group samples in the Lambton and Kent areas do not show the “Lambton anomaly” – a possible time constraint on fluid/microbial interaction in the reservoirs in the Lambton area?

- caution, only 3 samples!

-20 -15 -10 -5 0 5-140

-120

-100

-80

-60

-40

-20

0

Dundee

Columbus

Lucas (Detroit River Group)

Salina F unit (*subcrop)

Salina A2 carbonate

Salina A1 carbonate

Guelph/Salina A1 carb

Guelph

Rochester/Irondequoit

Thorold/Grimsby

Trenton-Black River Group

Cambrian

δ18O‰ (VSMOW)

δ2H‰

(VSM

OW)

LMW

L

Water isotope data

Shallow aquifers (<250m)

Deep aquifers (~500 - 1200m)

FURTHER WORK

Continue sampling of abandoned well fluids, as and when required, will provide an ongoing test of this geochemical tool.

Fill in the gaps: - more samples from the Appalachian side of the Algonquin Arch- stratigraphic horizons of interest with respect to geographic locality – Lambton looks v. interesting for e.g.

create a user-friendly platform to input gas and water isotope analyses and statistically analyse the results of unknowns vs knowns to ultimately identify the unknown reservoir. SIARS seems to be a good statistical tool at present

Critically analyse and interpret all these data to confirm observed patterns and ascertain how these reservoirs have been produced/modified and/or show migration/mixing

Acknowledgments

As always: LSIS – Kim, Li and Lisa for help on the GC, Picarro, Gasbench and TC/EA

Paul and Wendy at GGHatch, UofO for help with sulphur isotope analyses

Scott Mundle at UofT for keeping us entertained in the field… even if it is his fault that we have to stand out there for an hour at a time freezing or melting!... Lee thanks for arranging the coldest/hottest/post-tornado blowiest days for heading out into the backwoods!