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 Email: Dick.Drozd@WeatherfordLabs.com

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

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

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.

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

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)

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.

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

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

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.)

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

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”

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

Calculated %Ro Values from Tmax %VRo from Tmax = (0.0180 x Tmax) -7.16 Calculated values Jarvie et al., 2001

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.

Some S2 Pyrograms Tmax Tmax?

Thermal Maturity Guidelines Vitrinite Reflectance (% Ro) scale for maturity assessment Immature <0.6% Ro Oil window 0.6-1.1% Ro Wet gas window 1.1-1.4% 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

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. 341 - 356

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

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.

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

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

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

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

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)

Stratigraphy

Utica & Point Pleasant Thickness

Structure on Top of the Trenton

Source Rock Maturation Status

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

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.

Contour Map – TOCo Utica / Pt Pleasant

Contour Map – Ro Equiv Pt Pleasant

Contour Map – NOC

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.

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.

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

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.

(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)

Questions?