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Pyrolysis and TOC Identification of Tight Oil SweetSpots

Albert Maende* and W. David Weldon, Wildcat Technologies,LLC, Humble, TX, United States.

TALK OUTLINE

• Bakken Formation area of study

• Type of data, analytical method and interpretation framework

• Previous work

• Results

• Identification of Sweet Spots

• Conclusions

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Bakken Formation Area of Study

Bakken Formation Members• Lower Bakken Shale; deep marine organic rich

• Middle Bakken Member; epicontinental calcareous, dolomitic – siliciclasticthat is variously mottled, bioturbated and laminated

• Upper Bakken Shale; deep marine organic rich

Drilled Wells & Area of Study• 8 wells that were drilled through the Mississippian – Devonian (Paleozoic)

Bakken Formation within Williston Basin in North Dakota; originated ascontinental shelf but became intracratonic and has structures that reflecttrends of the Rocky Mountain province (Gerhard et. al., 1982)

Area of Study

Location of 8 wells analyzed from North Dakota, Williston Basin

WellNGS #

8474 2618 607 1405

WellName

GrahamUSA #1-15

JacobHuber#1

AngusKennedy#F32-24D

CarolineE. Peck#2

WellNGS #

11617 8177 5088 16637

WellName

Hagen#1-13

Dobrinski#18-44

Texel #1-15

Long #1-01H

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Type, Source of Data and Analytical Method

Type of Data• Pyrolysis, TOC and Carbonate Carbon

Source of Data• Pyrolysis and TOC data published by North Dakota Geological Survey

• HAWKTM Pyrolysis, TOC and Carbonate Carbon (CC) measurementsAnalytical Method• Dried drill cuttings ground using a mortar and pestle• Weighed to about 100 mg on a 4 decimal place balance• Analyzed for their S1, S2, S3, Tmax, TOC and CC measurements on the

HAWKTM Pyrolysis and TOC instrument

Analyzed Parameters

Pyrolysis, TOC and Carbonate Carbon Parameters

• S1 – free oil (mg hydrocarbons/g rock)

• S2 – kerogen yield (mg hydrocarbons/g rock)

• S3 – pyrolyzed CO2 (mg CO2/g rock)

• Tmax - Temperature (°C) at maximum generation of hydrocarbons frompyrolysis

• Carbonate Carbon (inorganic carbon) – wt. %

• Total Organic Carbon (TOC) – wt. %

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Pyrolysis Indices

Interpreted Pyrolysis Indices

• Hydrogen Index; S2/TOC x 100 (mg HC/g TOC)

• Oxygen Index; S3/TOC x 100 (mg CO2/g TOC)

• Oil Saturation Index (OSI); S1/TOC x 100

• Vitrinite Reflectance equivalent (Roe); Roe = 0.018 x Tmax – 7.16 (Jarvie, 2012)

Interpretation Framework

• Compilation of pyrolysis, TOC and CC data plus indices in graphical plots

• Evaluation in a lithofacies framework

Previous Work

Lithofacies of the Middle Bakken Member

(LeFever, 2009)

(Hess, 2011)

Wireline logs from 2 Bakken Formation Fields

Mid

dle

Bak

ken

Me

mb

er

Upper Bakken Shale

Lithofacies 5 - Siltstone

Lithofacies 4 - ParallelInterbeds of Dark Grey Shaleand Buff Silty Sandstone

Lithofacies 3 - Sandstone

Lithofacies 2 - ParallelInterbeds of Dark Grey Shaleand Buff Silty Sandstone

Lower Bakken Shale

Lithofacies 1 - Siltstone

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Previous Work

Isopach Map of the Middle Bakken Member Isopach Map of the Lower Bakken Shale

Mountrail maxthickness ~ 60 ft.

Mountrail maxthickness > 50 ft.

(LeFever, 2009)

CountyM – MountrailW – WilliamsMc - Mckenzie

MW

Mc

M

Mc

W

Previous Work

Hydrogen Index Map of the Bakken Formation

API Gravity of Bakken Formation Oils

(Kuhn et. al., 2009)Thickest Middle Bakken

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Results

Bakken Formation Tops in the Analyzed Wells

Texel #21-35

Dobrinski#18-44

Hagen #1-13

CatherineE. Peck #2

AngusKennedy#F32-24D

JacobHuber #1

GrahamUSA #1-15

Long #1-01H

UpperBakken(ft.)

10160.00–10172.00

8629.00 –8638.50

10508.67–10521.67

10369 –10372

MiddleBakken(ft.)

10169.00 –

10247.00

8638.58–

8661.50

10363.60 –

10375.00

10770.75 –

10793.92

10522.0 –

10573.83

9801 –

9825.58

10374 –

10378

9138 –

9171.5

LowerBakken(ft.)

10248.00 –

10263.00

8661.90 –

8668.00 ft.

10376.00 –

10406.00.

10794.58 -

10815.83

10574.00 –

10599.83

9826.08 –

9836.75

10379

Results

Graham USA #1-15 Well

MiddleBakkenMember

UpperBakkenShale

0.00 1.00 2.00 0 200 400 600

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Results

Jacob Huber #1 Well

0 20 40 60 80 100 0 200 400 600 800

MiddleBakken

LowerBakken

Results

Angus Kennedy #F32-24-P Well

0 200 400 600 8000 20 40 60 80

Upper Bakken

Middle Bakken

Lower Bakken

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Results

Catherine E. Peck #2 Well

0 10 20 30 0 100 200 300 400 500

Middle Bakken

Lower Bakken

Results

Hagen #1-13 Well

0 5 10 15 20 0 200 400 600

Middle Bakken

Lower Bakken

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Results

Dobrinski #18-44 Well

0 50 100 150 0 500 1000 1500

Upper Bakken

Middle Bakken

Lower Bakken

Results

Texel #21-35 Well

0 20 40 60 80

De

pth

(ft)

0 200 400 600 800

Upper Bakken

Middle Bakken

Lower Bakken

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Results

Long 1-01H Well

Upper Bakken

Middle Bakken

Lower Bakken

0 20 40 60 80 100 120 140 160 180 200 0 200 400 600 800 1000

Interpretation of Results

Interpreted Lithofacies for Middle Bakken Member in Long 1-05H Well on the basis ofPyrolysis Data

Depth (ft.) S2 (mg HC/g rock) InterpretedLithofacies

9138, 9140, 9140.5, 9141.5, 9142.5, 9151, 9151.5, 9155, 9156,9150.5, 9164, 9164.5, 9168.5 - 9170

<1.00 Sandy

9142, 9143, 9143.5, 9146 – 9147.5, 9150.5, 9152.5, 9153, 9155.5,9156.5 – 9159, 9160, 9165 – 9168, 9170.5 – 9171.5

1.00 – 1.60 Silty

9138.5 – 9139.5, 9141, 9142, 9144 – 9145.5, 9148 – 9150, 9152,9153 – 9154.5, 9157.5, 9160.5 – 9161, 9163 – 9163.5

>1.60 Shaly

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Interpreted Results

Interpreted Sweet Spots in the Middle Bakken MemberWell Name(NGS No.)

Formation InferredSweetspot;Depth (ft.)

TOC (wt.%); range(mean)

OSI; range(mean)

S2 (mgHC/g rock);range(mean)

InferredMiddleBakkenLithofacies

HydrogenIndex ofLowerBakken;range(mean)

GrahamUSA #1-15(8474)

MiddleBakkenMember

10374 -10376

0.28 – 0.46(0.35)

54 – 146(88)

0.33 – 0.86(0.56)

Sandy

CatherineE. Peck #2(1405)

MiddleBakkenMember

10770 -10793

0.57 – 0.93(0.82)

89 – 149(132)

0.50 – 1.25(0.94)

Sandy 47 – 180(108). Roe ofLower Bakken;0.81 – 0.98(0.92)

Interpreted Results

Interpreted Sweet Spots in the Middle Bakken Member

Well Name(NGS No.)

Formation InferredSweetspot;Depth (ft.)

TOC (wt.%); range(mean)

OSI; range(mean)

S2 (mgHC/g rock);range(mean)

InferredMiddleBakkenLithofacies

HydrogenIndex ofLowerBakken;range (mean)

Hagen #1-13 (11617)

MiddleBakkenMember

10363 -10373

0.22 – 0.49(0.35)

100 – 129(115)

0.30 – 1.08(0.61)

Sandy 80 – 134 (108).Roe of LowerBakken; 0.83 –1.07 (1.01)

Long 1-01 H(16637)

MiddleBakkenMember

8138 –9171.5

0.22 – 0.76(0.47)

374 – 791(630)

0.46 – 2.89(1.36)

Silty 464 – 827 (712).Roe of LowerBakken; 0.51 –0.74 (0.61)

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Interpreted Results

Non – Oil Productive Middle Bakken Member

Well Name(NGS No.)

Formation MiddleBakken;Depth (ft.)

TOC (wt.%); range(mean)

OSI; range(mean)

S2 (mgHC/g rock);range(mean)

InferredMiddleBakkenLithofacies

HydrogenIndex ofLowerBakken;range (mean)

Dobrinski#18-44(8474)

MiddleBakkenMember

8638 -8661

0.10 – 0.80(0.29)

0 – 298(44)

0 – 1.91(0.13)

Sandy 20 – 607 (200).Roe of LowerBakken; 0.31 –0.62 (0.48)

Identification of Sweet Spots

Sweet Spots indicative of Middle Bakken Member Productive Oil Intervals

• Oil Saturation Index Values exceeding 100

• Over a continuous multi-depth interval not just single streaks

• Sandy lithofacies

• At locations with Middle Bakken Member that overlies:

i. Lower Bakken Shale of Roe 0.90 – 1.00

ii. Hydrogen Index of about 100

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Some Exceptions

Long 1-01H Well

The productive oil Middle Bakken depth interval differs in that:

• Roe of underlying Lower Bakken is barely mature (0.61)

• Hydrogen Index of the underlying Lower Bakken averages 712

• Inferred to be migrated oil

Conclusions

Formation Tops

• Upper, Middle and Lower Bakken Formation Tops can be picked on the basis of theirpyrolysis and TOC data

• Using Pyrolysis and TOC to pick Formation Tops is similar to using wireline logsUsing Pyrolysis data, the Middle Bakken lithofacies can also be identified in terms of:

• Relative sandy, silty and shaly tendencies on the basis of S2 values;

• S2 values of <1.00, 1.00 – 1.60 and >1.60 mg HC/g rock

Sweet Spots marking Middle Bakken productive oil intervals

• Oil Saturation Index values >100 over a continuous multi-depth interval

• Locations where Middle Bakken overlies Lower Bakken of Roe 0.90 – 1.00 and HydrogenIndex of about 100

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Acknowledgements/Questions

I am grateful to Wildcat Technologies for sponsoring my participation at this landmarkconference and I wish to also say thank you to URTeC conference organizers for invitingme.

Thank you for listening to me and please let me have your questions.

References

HESS, 2011, Westward Expansion of the Bakken Oil Resource Play in North Dakota, Tight Oilfrom Shale Plays, World Congress 2011.Jarvie, D. M., 2012, Shale Resource Systems for Oil and Gas: in J. A. Breyer, ed., Shale Reservoirs– Giant Resources for the 21st Century: AAPG Memoir 97, p 69 – 87 and p.89 – 119.Gerhard, L. C., S. B. Anderson, J. A. LeFever and C. G. Carlson, 1982, Geological Development,Origin, and Energy Mineral Resources of Williston Basin, North Dakota: AAPG Bull. v.66, No. 8,p. 989 – 1020.LeFever, J. A., 2009, Montana-North Dakota? Middle Member Bakken Play, North DakotaGeological Survey.North Dakota Geological Survey, 2011.Kuhn, P. H., R. di Primio and B. Horsfield, 2009, Inconsistency of Hydrocarbon GenerationPotential and Production Data, The Bakken Play of North Dakota, 7th Petroleum GeologyConference – Queen Elizabeth II Conference Center, London.