1. Presented by: Dick Drozd Email: Dick.Drozd@WeatherfordLabs.com
Source Rock Geochemistry and Thermal Maturity Discussion of the Utica-Point Pleasant in the Northern Appalachian Basin
Presented by: Dick Drozd

2. Presentation Outline
What are the important elements of a geochemical evaluation and why.
Specific geochemical issues with the Ordovician section.
Geochemistry of the Utica – Point Pleasant and equivalent units.
Implications for exploration.
Questions

3. Significant Elements of Source Rock Evaluation
Organic Richness
Remaining Potential for Generation
Thermal Maturity
Kerogen Type
All measurements are made on present-day as- received material
Original condition most significant for exploration

4. Total Organic Carbon (TOC)
Solid organic material contained within a sample that can be subdivided into kerogen and bitumen.
Total organic carbon determined by combustion of samples that have been treated with acid to remove inorganic carbon.
Usually reported in units of weight fraction, TOC weight divided by sample weight.

5. Why is TOC Important? TOC provides the carbon for hydrocarbons
TOC provides increased porosity with increasing thermal maturation
TOC provides adsorptive sites for hydrocarbons
To retain oil for cracking to gas
Storage of adsorbed gas

6. Total Organic Carbon Guidelines
Present day organic richness of source rock
Quality
TOC (wt%)
Poor
<0.5
Fair
0.5 to 1
Good
1 to 2
Very good
2 to 4
Excellent
>4
Threshold Shale Oil
Threshold Shale Gas
The TOC Myth: “If I have high TOC, I have a good source rock.” (Dembicki, 2009)

7. Programmed Pyrolysis Pyrolysis Temperature-Programmed Pyrolysis
A chemical degradation reaction that is caused by thermal energy. (The term pyrolysis generally refers to an inert environment.)
Temperature-Programmed Pyrolysis
A pyrolysis during which the sample is heated at a controlled rate within a temperature range in which pyrolysis occurs.

8. Source Rock Analyzer (SRA)
Pyrolysis instrument that uses an FID detector and IR cells to measure:
Available Hydrocarbon Content – S1
Remaining Hydrocarbon Generation Potential – S2
Organic Richness – TOC
Thermal Maturity – Tmax

9. Parameters Measured
With Flame Ionization Detector (FID) - detects hydrocarbons only:
Volatile hydrocarbon content – S1
Pyrolized hydrocarbons – S2
Tmax – Temperature of maximum S2 release
With Infrared Detector – detects CO and CO2 only:
CO2 generated during pyrolysis – S3
Total organic carbon (TOC) – S4

10. Remaining Generative Potential Volatile Hydrocarbon Content
Displayed Pyrogram
Remaining Generative Potential
Hydrogen
Measure of TOC
CO2 Generation S4 S2
Temperature trace (nonisothermal
at 25oC/min)
600oC S3
Volatile Hydrocarbon Content S1
Yield
300oC
Tmax
Time (mins.)

11. Thermal Maturity Challenging to Measure
Maturation parameters are indicative of the maximum paleo- temperature that a source rock has reached:
Visual
Vitrinite reflectance (whole rock or kerogen concentrate)
Color indices (Conodonts, Zooclasts, bitumen)
Chemical
Programmed Pyrolysis Tmax (chemical) 11 11 11

12. Vitrinite Reflectance
Vitrinite: a term (from coal petrography) for the jellified remains of higher plant tissues (post-Silurian)
With increasing thermal alteration, vitrinite becomes more graphitic (condensed aromatic rings increase) and reflects more light
Reflectance (%Ro) tracks kerogen maturity
Other maturity measures expressed on vitrinite “scale”

13. Problems Obtaining Ro Maturities
Properly identified vitrinite:
Primary
Recycled
Cavings
Mud additives
Factors affecting accurate Ro measurements:
Poor polish
Oxidized vitrinite
Inclusions (pyrite, bitumen, other macerals)
Poor statistics (too few particles)
Hunt, 1996, p. 515

14. Calculated %Ro Values from Tmax
%VRo from Tmax = ( x Tmax) -7.16
Calculated values
Jarvie et al., 2001

15. Issues with Tmax Anything that affects the peak shape will affect Tmax
Contamination from drilling mud may alter the S2 peak,
with high amounts of indigenous or migrated oil present, the oil part of S2 may exceed the kerogen S2 and Tmax will be too low,
at very high maturities, there is no S2 peak (flat) and Tmax is virtually random
dependent on kerogen type.

16. Some S2 Pyrograms
Tmax
Tmax?

17. Thermal Maturity Guidelines
Vitrinite Reflectance (% Ro) scale for maturity assessment
Immature <0.6% Ro
Oil window % Ro
Wet gas window % Ro
Dry gas generation 1.4-~2.2% Ro
Dry gas preservation ~2.2-~3.2% Ro
Gas destruction >~3.2% Ro (?) 17 17 17

18. The TOC Myth: “If I have high TOC, I have a good source rock
The TOC Myth: “If I have high TOC, I have a good source rock.” (Dembicki, 2009)
Although a good source rock must have high TOC, not all organic matter is created equal.
The more hydrogen associated with the carbon, the more hydrocarbon it can generate – particularly liquid hydrocarbons.
Thus, we also need an indicator for the amount of hydrogen present in the organic matter (measured present day – projected into the past).
KEROGEN TYPE
From, Dembicki, H. (2009), Three common source rock evaluation errors made by geologists during prospect or play appraisals, AAPG Bulletin, v. 93, p

19. Primary Hydrocarbon Generation Yields
Oil vs. Gas
Type I (HI=810)
Type II (HI=420)
Type III (HI=250) C1
C2-C4
C5-C14
C15+
(Not secondary cracked products)
Jarvie, unpublished data

20. Kerogen Maceral Types
Maceral composition is determined via petrographic (optical) analyses of pelletized samples or thin sections.
Three Primary Maceral Groups.
Liptinite: Hydrogen-Rich
Vitrinite: Oxygen-Rich
Inertinite: Carbon-Rich
Numerous macerals and sub- macerals in each maceral group.
Fully characterize Kerogen Type via Maceral Composition and Programmed Pyrolysis.
Maceral Group
Macerals
Organic Precursors
Kerogen Type
Liptinite
Alginite I
Fresh Water Algae I
Alginite II
Marine Algae II
Exinite
Spores (Sporinite), Pollen
Cutinite
Leaf Cuticle
Resinite
Resin, Tree Sap
Vitrinite
Vitrinite, Psuedovitrinite
Woody Tissue
III
Inertinite
Semifusinite, Fusinite, Sclerotonite, etc.
Reworked and/or Oxidized Material, Charcoal IV
1. The coal mining and coal gas industries describe the organic composition of coal seams (or coal gas reservoir systems) in terms of maceral concentrations.

21. Visual Kerogen Type Assessment
Amorphous organic matter
Type I: (oil prone)
lacustrine algae
Type II: (oil prone)
marine algae

22. Visual Kerogen Type Assessment
Structured organic matter
Type III: (gas prone)
woody

23. Kerogen Quality Plot – Barnett Shale Example
Samples as measured today, at present maturity!
ca. 1.50% VRo
ca. 1.00% VRo
ca. 0.85% VRo
ca. 0.55% VRo
ca. 0.70% VRo
25% 0.70%Ro
50% 0.85%Ro
75% 1.00%Ro
90% 1.50%Ro

24. Estimation of Yields Measured present day: Original:
Barnett Shale (Oil)
Measured present day:
TOC
Volatile Hydrocarbons
Remaining Potential
Kerogen Type
Thermal Maturity
Original:
TOCo
Total Potential
Kerogen Type
Partitioning gas/oil
“Magic” is a set of calculations described in the literature but too long for this presentation.
Yield a set of yield estimates.
MAGIC

25. Utica / Point Pleasant & Equiv. Rocks
Early Paleozoic age, therefore no primary Type III organic matter present
Maturity - no vitrinite – Substitute:
Zooclasts reflectance (chitinozoans, scolecodonts, etc.) or bitumen reflectance
Conodont color
Original Kerogen Type – Original hydrogen index (HIo)
Primary organic matter marine
Contribution from reworked/ recycled organic matter likely low,
Contribution of oxidized organic matter unknown
Over large geographic area & depositional settings variations likely (measured HIo 200 to 650)

26. Stratigraphy

27. Utica & Point Pleasant Thickness

28. Structure on Top of the Trenton

29. Source Rock Maturation Status

30. Point Pleasant Equivalents
Utica Undifferentiated
Point Pleasant
Collingwood
Cobum
Antes
Cobourg
Lindsay

31. Source Rock – Oil Correlation
Two papers in the 1990’s Cole et al and Drozd & Cole examined the petroleum systems in Ohio. Conclusions:
Oil in Ohio classified into three families
Group 1 found in Cambrian, Ordovician and some Silurian reservoirs, fingerprint characteristics of Early Paleozoic organic matter, and heavy carbon isotopes,
Group 2 found in some Silurian and Devonian to Pennsylvanian reservoirs, variable but distinct fingerprint characteristics, and intermediate carbon isotopes,
Group 3 found in a few Berea reservoirs similar to Group 2 in fingerprint pattern, but with light carbon isotopic composition.
Source-Oil Correlation
Group 1 oils from Point Pleasant Shale,
Group 2 oils from facies of Ohio Shale, hence variable characteristics,
Group 3 oils from Sunbury Shale.

32. Contour Map – TOCo Utica / Pt Pleasant

33. Contour Map – Ro Equiv Pt Pleasant

34. Contour Map – NOC

35. Comparison of Pt Pleasant to Other Shale Plays
TOC (wt%)
TOCo (wt%)
Maturity (%Ro eq)
Ohio
Pt Pleasant
1.65
2.01
0.84
Attractive
2.40
2.80
0.76
Michigan
Collingwood
1.96
2.74
1.44
Ontario
Lindsay
5.20
5.52
0.69
6.53
7.27
0.74
4.96
7.19
0.83
2.56
3.79
1.23
Utica
1.00
1.25
0.85 PA
1.76 2+
Barnett (Oil)
3.86
Eagle Ford (Oil)
2.76
0.98
Geneseo/Burkett
2.52
1.19
There is some variability in TOC in OH, similar to Collingwood in MI. Average maturity very different.
“Selected” samples can have much higher TOC than cuttings.
Utica in PA may include Pt Pleasant facies; much more mature.
Other shale oil plays.

36. Ongoing Thoughts
Our understanding of the kinetic of the Point Pleasant kerogen is very limited due in part of lack of appropriate samples (low maturity but similar facies to producing area)
Therefore, maturity guides may not be as appropriate as we would like.

37. Kerogen Type Determines Timing/Rates of Conversion
0.60
430
440
450
460
470
480
420
0.40
0.75
0.95
1.10
1.30
1.50
%Ro
Tmax (oC)
Type II-OS
Type II
Type III
Type I

38. Ongoing Thoughts
Our understanding of the kinetic of the Point Pleasant kerogen is very limited due in part of lack of appropriate samples (low maturity but similar facies to producing area)
Therefore, maturity guides may not be as appropriate as we would like.
Product expectation (heavier oil, light oil, condensate, wet gas) is also less certain than preferred.
Variation in properties across a play is always an issue when the play is new, because we have yet to fully measure parameters needed to obtain a basic understanding of the detailed rock characteristics.

39. (Richard Stoneburner, COO, Petrohawk Energy)
The first step in our successful development of the Eagle Ford Shale play was to “prove the rocks”.
(Richard Stoneburner, COO, Petrohawk Energy)

40. Questions?