origin of combustible gases in water-supply wells in north-central … · 2012-08-09 · revesz,...

Origin of combustible gases in water-supply wells in north-central

Pennsylvania -- isotopic data from 2005 during a time when there was no Marcellus

development or hydraulic fracturing activity

U.S. Department of the Interior U.S. Geological Survey

Kinga M. Révész,1 Kevin J. Breen,1 Alfred J. Baldassare,2 and Robert C. Burruss1 1. U.S. Geological Survey, 2. E C H E L O N Applied Geoscience Consulting

Presented at Stray Gas Incidence & Response Forum, Ground Water Protection Council, July 2012, Cleveland, Ohio

Revesz, and Others, 2010, Applied Geochemistry, v.

25, p. 1845–1859 and as an erratum, 2012, Applied Geochemistry

v. 27, p.361-375

USGS Research Origin of Stray Gas in Groundwater

Carbon and hydrogen isotopic evidence for the origin of combustible gases in water-supply wells in north-central Pennsylvania

Presented by K.M. Révész at Stray Gas Incidence & Response Forum, Ground Water Protection Council, July 2012, Cleveland, Ohio

I. About the site, where the problem occurred. II. Sample collections. III. About basic isotope principles. IV. Results and data interpretation. V. New drilling or fracturing in the area.

Outline of the talk


Methane (CH4) concentrations in well water

Valley-- GLACIAL OUTWASH AQUIFER of Quaternary age

Uplands-- Fractured BEDROCK AQUIFER -- Lock Haven Formation of Devonian age

Révész et al., 2012

Possible Origins of Methane in the Area (end members)

• Oriskany gas - thermogenic, local gas. • Pipe Line gas – thermogenic. • Microbial from possible landfill, or

natural decay of organic matter. • Devonian gas (shallow) - thermogenic. • Mixture of all above.


Sample collection and analyses

• Collections: – End member Gases: Oriskany, Pipe Line,

Storage gas. – Groundwater, containing natural gas and

possible background wells from the same aquifer.

• Analysis: – 13C of CH4 and C2H6; 2H of CH4; 14C of CH4

of some samples, Dissolved gas concentration, 2H and 18O of water, 13C of DIC, Alkalinity.


Delta notation

reference

referencesample

RRRδ −=C13

Where R = 13C/12C, Rreference= VPDB (Vienna PeeDee Belemnite)

Stable Isotope of elements and the delta notation

reference

referencesample

RRRδ −=H2

Where R = 2H/1H, Rreference= VSMOW (Vienna South Mean Ocean Water)

2H alternative name is D (deuterium). δ2H = δD

Carbon element, for example, has two stable isotopes, 13C and 12C, reflecting the number of neutrons in the atom. During compound production or reactions, the ratio of 13C/12C changes, because the two isotopically different atoms react at different rates. Therefore, isotope ratio measurements of an element can give information about the production of the compound, and the possible secondary reaction of the compound.


Microbial Methane production

1. Near-surface environment, marsh etc. CH4 production by fermentation pathway:

CH3COOH = CH4 + CO2 Isotope change: Intra-molecular fractionation: CH3 = δ13C in CH3

depleted in 13C; the C is enriched in COOH. Product: CH4 = is depleted in13C; CO2 = is enriched in13C. (DIC) Concentration change: CH3COOH decreasing CH4 and CO2 increasing (DIC) 2. Drift gas -old, covered by glacial drift deposit.

CH4 production by CO2 reduction pathway : CO2 + 4H2 = CH4 + 2H2O

Isotope change: CH4 = is depleted in13C; CO2 = is enriched in13C (DIC);

Concentration change: CH4 increasing, CO2 decreasing (DIC) 3. Minimal C2 and C3 production, they are very depleted in 13C.


– formed by thermal break down. 1. Higher hydrocarbons (C2; C3; etc.) are

present 2. δ13C of CH4 is closer to the isotope of

substrate it is produced from (more enriched than microbial).

3. C2 and C3 are more enriched in 13C than those in microbial natural gas, if there is any.

Thermogenic Methane production


2CH4 + 4O2 = 2CO2 +4H2O Concentration change: CH4 decreasing, CO2 (DIC) increasing.

13C isotope change: CH4 becomes enriched in 13C; CO2 (DIC) becomes depleted in 13C.

Methane oxidation independent from production pathways


Oriskany gas wellsStorage gas obs. wellsStorage gas Inj. wells

Rock wells (GW)Outwash wells (GW)

Whiticar, 1999: Thermogenic Gas: δ13C=-50 to -20‰; δD= -275to -100‰ Microbial Gas:δ13C=-110 to -50‰; δD= -400 to -150‰

Révész, and Others, 2012 in Applied Geochemistry

C and H stable isotopes of CH4

The importance of the δ13C of ethane

Révész, and Others, 2012 in Applied Geochemistry

-80 -70 -60 -50 -40 -30delta

13CCH4 in per mill VPDB

-24

-20

-16

-12

-8

-4

0

d13 C

of D

IC in

per

mill

VPD

B

-80 -70 -60 -50 -40 -30delta 13CVPDB of CH4 in per mill

-360

-320

-280

-240

-200

-160

-120

-80

delta

2 Hvs

mow

of C

H4 i

n pe

r mill

Identifying secondary reaction; oxidation of methane

2CH4 + 4O2 = 2CO2 +4H2O

δ13C isotope change: CH4 becomes enriched ; CO2

(DIC) becomes depleted in 13C Concentration change: CH4 decreasing, CO2 (DIC)

increasing.


Bernard graph Oxidation and mixing curves

Modified from Révész et al., 2012

Microbial

Thermogenic with >0.1 percent ethane

Methane Signatures in Groundwater from Wells

Methane Signatures in GW Wells

Révész et al., 2012

New potential sources


δ13C of ethane, partial isotope reversal effect

δ13C of ethane could help further differentiate among thermogenic origin of combustible gases.

Fred Baldassare and others, GWPC, Atlanta, GA, September 2011

δ13C of CH4 and C2H6 in end member gas wells

Modified from Révész, et al., 2012.

Essential data to identify stray gas origins

1. Identify possible gas sources. 2. Create a baseline gas signature library. Determine

concentrations and δ13C - δ2H of CH4; and δ13C of higher hydrocarbons across the area from various source units.

3. Carry out site specific monitoring of natural gas in groundwater before (baseline), during and after drilling. (Concentrations and δ13C - δ2H of CH4; and δ13C of higher hydrocarbons). Determine the source(s) of stray gas in domestic-supply wells and identify gases from major and minor gas production zones across the area.

4. Monitor longer-term changes in methane presence/concentration as area develops (well density), and as the wells age (leakage from casing/grout seals) during and following gas production (decades).


“More likely causes of possible environmental contamination include faulty wells, and leaks and spills associated with surface operations. Neither cause is unique to shale gas. Both are common to all oil and gas wells and extractive activities” (RSSPC, RAE). “Combined gas (Révész et al 2010) and water (Osborn and McIntosh 2010) analyses can be carried out to understand the origin of gases in aquifers (RSSPC, RAE).

The Royal Society Science Policy Center, Royal Academy of

Engineering


Baldassare, A. J., Laughrey, C.D., McCaffrey, M, and Harper, J.A., Ground Water Protection Council Annual Forum, Atlanta, GA, September 2011. Accessed as presentation 19s at

http://gwpc.org/events/gwpc-proceedings/2011-annual-forum Bernard, B.B., Brook, J.M. and Sackett, W.M., 1976, Earth Planet. Sci. Lett.

31, 48–54. Coleman, D. D., 1994. American Gas Association, Operating Section

Proc., pp. 711–720. Osborn, S. G. and McIntosh, J. C.,2010, Appl. Geochem., 25, 456–471. Révész, K. M., Breen, K. J., Baldassare, A. J., and Burruss, R. C., 2010,

and as an Erratum, 2012 in Applied Geochemistry Vol. 27, p.361-375. Schoell, M., 1980., Geochim. Cosmochim. Acta 44, 649–661. The Royal Society Science Policy Center, The Royal Academy of

Engineering, June 2012, http://royalsociety.org/policy/projects/shale-gas-extraction/ ;http://royalsociety.org/policy/projects/shale-gas-extraction/report

References


http://royalsociety.org/policy/projects/shale-gas-extraction/

http://royalsociety.org/policy/projects/shale-gas-extraction/

http://royalsociety.org/policy/projects/shale-gas-extraction/report

origin of combustible gases in water-supply wells in north-central … · 2012-08-09 · revesz,...

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