This document summarizes characteristics of shale gas resources and provides a case study of the Utica Shale gas play in Quebec, Canada. Shale has very low permeability and requires advanced stimulation techniques like hydrofracturing to produce gas commercially. The document outlines geochemistry applications to characterize shale maturity, richness, and sorption properties. For the Utica Shale, geochemistry studies found the shale contains dry, thermogenic natural gas with 95% methane. Estimated gas-in-place and a transformation ratio suggest significant gas resources that could be economically produced.

1. Shale Gas Resource Evaluation and
Its Geochemistry Application
Daniel Acker/GettyImage
A Case Study of
Utica Gas Shale in Quebec, Canada
By : Yulini Arediningsih
www.cleanBizAsia.com
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2. Outline
Fast facts
Characteristics of gas shales
Challenges
Application of Geochemistry
Utica Shale Gas System, Quebec, Canada
Conclusions
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3. Fast Facts
Due to its huge volume and very low
Shale is the most common sedimentary rocks
permeability, shale gas extraction processes
having very low permeability.
become complex requiring enormous
Gas shale plays triple functions as gas self- advanced stimulation techniques such as
producer, trap and storage, with lack of migration hydrofracturing, steam injection and etc. to
Shale gas becomes an alternative gas supply to improve their fracture system so they can
substitute conventional gas whose production has flow at commercial rate.
recently declined.
Currently, Montney Fm. and Horn River Basin in
Western Canada have produced 1 Bcf of their
total 240 Tcf recoverable resource. Other
potential gas shale plays i.e. Colorado Group
(AB, SK), Utica Group (QC) and Horton Bluff
Group (NB).
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Source www.bbc.co.uk

4. Characteristics of Gas Shales
Low matrix permeability < 0.01md, low matrix porosity
<9%. To enable shale producing gas, favorable conditions
Types of gas produced can be biogenic, thermogenic needed are :
gas and mixed gas. High gas generation that are governed by :
geochemical characteristics of the shale such as
Gas generated in shale is stored as :
maturity, organic content,
predominantly sorbed gas in organic fraction
or kerogen;
High gas preservation, that are controlled by
free gas within micro (<2nm) to meso-sized(2- rock properties of the shale such as
50nm) pore spaces and shale fractures; large volume with sufficient thickness;
and dissolved gas in formation water natural extensive natural or induced fracture
pores and fractures of shale. permeability and porosity with sufficient
gas saturation;
lithological heterogeneity within the shale
interval providing internal source – storage
rock with good sealing
Source : Bustin and Clarkson, 1998 4

5. Application of Geochemistry
What can be solved by applying Geochemistry studies :
Characterization of shale source rocks including thermal maturity, source rock richness
and kerogen typing based on
plots of TOC and data from Rock-Eval Pyrolysis analysis
direct visual kerogen characterization
vitrinite reflectance
Sorption/desorption characteristics
Geochemical modeling of hydrocarbon generation and preservation
Gas play type (biogenic, thermogenic or mixed)
Carbon isotopes analysis for maturity and gas potential
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6. Challenges
GIP estimation of shale gas resources is difficult mainly because of complex nature of gas storage
between free gas and sorbed gas in nano to micro scale shale porosity
Mass balance calculation to estimate GIP needs careful consideration
Understanding the geochemistry of stored gas will make better approach in estimating economic of
shale gas potential
Poor understanding on how organic geochemical characteristics (such as TOC, organic material,
vitrinite content) controls gas adsorption/sorption capacity in the shale kerogen
However we have better knowledge on
vitrinite content and methane adsorption capacity showing positive correlation (Bustin and
Clarkson, 1998)
methane adsorption capacity can be controlled by increase in micro porosity due to thermal
maturity (Levy et al, 2007)
Shales with higher maturity, their maceral compositions tend to give a significant impact on
methane adsorption capacity (Chalmers and Bustin, 2007).
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7. Utica Shale Gas Play, Quebec, Canada
STATUS UPDATE :
(Summarized from Lavoie et al (2011)) :
Located in St. Lawrence Lowlands,
southern of Quebec
Exploration started in April 2008 so far 30
(Lavoie et al, 2011)
wells have been drilled
The main target :
interval depth 1000-2000m of medium to
deep thermogenic shale gas play (zone #2)
calcareous and organic-rich Middle
Ordovician Utica shale
OGIP estimates : 120 -160 Bcf/section,
overall giving significant Tcf amount of its
total GIP accumulation.
Factors of gas quality, the shale fracture
network that can be hydrofractured, its
strategic location and high gas demand
have elevated the prospective status
play to contingent resources/reserves.
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8. Utica Shale Gas Play, Quebec, Canada
GEOLOGY AND STRATIGRAPHY
The Utica shales is typically calcareous and rich in organic materials deposited in
marine environment overlying the massive Trenton limestone during the Taconic Orogeny.
Complex monoclinal and SW/NE trending normal fault system surrounding the potential
area appears to have created favorable fracture network to ease hydro-fracturing process.
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9. Utica Shale Gas Play, Quebec, Canada
GEOCHEMISTRY STUDIES
This good TR estimate may provide confidence in applying the
Samples analysed are from low maturity Utica shales to provide mass-balance approach for the calculation of OGIP.
an estimation of TOCoriginal for transformation ratio (TR) and
kerogen type estimation (see next figure)
Thermal maturity, measured in reflectometry-vitrinite
equivalence (Ro eq.), varies between 1 and 4% from the
northwest toward the southeast.
TOCpresent day : 1 and 6% (samples from the south to northeast
of the Utica shale play) suggesting a mature to dry natural gas
and condensate type.
Shales with TOC of 4 and 6% have a lower maturity level
(between 0.5 to 1.0% Ro eq.)
The Utica shales are type II based on data of maturity (%Ro)
and HI
TR is estimated to be 75% (1% TOCpresentday over 4% TOCoriginal) (Lavoie et al, 2011)
signifying that large quantities of natural gas in the system have
been generated from the kerogen.
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10. Utica Shale Gas Play, Quebec, Canada
GAS GEOCHEMISTRY
Overall, gas type in the St. Lawrence Lowlands range from
low maturity (wet) to high-maturity (dry) thermogenic gas.
GC analysis of main target zone (medium to deep
thermogenic play) contains gas with 95% methane. Toward
shallower thermogenic zone located on the north shore of the
St. Lawrence River, the gas become less mature containing
higher ethane and propane.
Data of ethane carbon isotopes and gas wetness from the
Utica shale gas wells are plotted within a isotope rollover
anomaly zone as represented by data from the Barnett,
Haynesville, and Marcellus prolific gas shales. This signifies
promising future potential of the Utica gas shale.
The isotopic data from the Utica shale gas wells also
suggest that :
(Lavoie et al, 2011)
all gas encountered is thermogenic generated from the
same source rock,
Indication of increasing maturity trend
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11. Conclusions
Understanding the geochemistry of stored gas will make better approach in estimating economic
of shale gas potential
GIP estimation of shale gas resources is difficult mainly because of complex nature of gas
storage between free gas and sorbed gas in nano to micro scale shale porosity
Application of geochemical techniques and analyses such as kerogen typing (S2 vs TOC plot)
and ethane isotopes, in the Utica Shale gas data provides positive contribution on understanding
the gas resources in the Utica Shale. The results suggest the shale contain a mature to dry
natural gas and condensate type.
More importantly, good estimate of TR value from TOCpresent day vs TOCoriginal data provide
confidence in applying the mass-balance approach for the calculation of OGIP.
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12. Cited References
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Articles #40382 (2009). Adapted from oral presentation at AAPG Annual Convention, San Antonio, Texas, April 20-23.
Bustin, R.M. and Clarkson, C.R., 1998: "Geological Controls on Coalbed Methane Reservoir Capacity and Gas Content"; The International Journal of
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Colorado, February 10–12, 2008, Society of Petroleum Engineers, SPE 114167
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Columbia, Canada, International Journal of Coal Geology, 70, 223-239 Shale Gas consortium
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Gas
Lavoie, J.Y. , Marcil, J.S., Dorrins, P.K., Lavoie, J., and Aguilera, R., 2011 Natural-Gas Potential in the St. Lawrence Lowlands of Québec: A Case
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Levy JH., Day SJ., Killingley J.S, 1997, Methane capacities of Bowen Basin coals related to coal properties, Fuel, 76(9), 813- 819
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Geologic and PetrophysicalCharacterization of Unconventional Shale-Gas Reservoirs, SPE 131350
Pittsburgh, C.B., Kieschnick, RSr., Lewis, R.E., Waters, G., 2006, Producing Gas from Its Source, Oilfield Review, Autumn, p.36-49
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