Hydrogeochemistry of shallow gas accumulations in fractured Devonian black shales Jennifer McIntosh, Department of Hydrology and Water Resources, University of Arizona, Tucton, AZ 85721
NY PA
rch
OH
0
All egh eny Val Fro ley nt and R id ge
Fin
dla yA
Upper Devonian organic-rich shale
WV
KY
860
840
7000
820
780
800
760
740
3)
C1 / [C2 + C3]
3000
Sampled formations for gas and waters:
2000
Berea Sandstone (Mississippian)
Fresh water dilution of brine
Sandstones and Shales (Devonian)
0 0
10
20
Br (mM)
30
40
Medina Sandstone (Silurian)
e Lak
MI
Eri
ch Ar
440
Lake Ontario
ON
100 km
e
NY PA
OH
Cl-Br relations and the stable isotope composition of shale formation waters indicate that saline brines were significantly diluted by freshwaters at the northwestern basin margin.
4000
1000
420
400
38
420
400
0
860
Carbon and hydrogen isotope values of CH4, and gas wetness (C1/C2+C3) increase with 1000 increasing thermal maturity of source organic matter.
5000
Adirondack Uplift n ui nq go l A
WV
KY
820
800
4)
2.0-2.9 3.0-3.9
100
10
Antrim and New Albany Shale Thermogenic Gas 1 -60
780
380
4.0-4.9 >5.0 740
760
Antrim and New Albany Shale Biogenic Gas
Biogenic
-70
1.0-1.9
Upper Devonian Organic-Rich Shale CAI Map 840
10000
6000
Cl (mM)
400
380
Cin ci
38
nn ati Arc h
400
420
440
740
760
-50
In cre as i M ng T at ur her it y m al
rie
780
All egh eny Val Fro ley nt and Rid ge
100 km
800
Arc h
ON
N
820
lay
eE Lak
Lake Ontario
2)
Salinity and thermal maturity of organic-rich shales are strong controls on microbial methane generation across the northern margin of the Appalachian Basin.
840
Fin d
n ui nq go
ch Ar
440
860
ati Arc h
Adirondack Uplift
Al
MI
740
760
inn
Extent of Last Glacial Maximum
420
780
Huron
0
Huron
44
800
Lake
N
820
Lake
1)
840
Cin c
860
Thermogenic -40
? 13C CH4 (‰)
-30
-20
