Assessing Source Rock Potential Using Solid-State 13C NMR Organic

Geochemical Approaches

• By Charlie Keracik

Acknoledgements

• Baylor University

– Dr. William Hockaday

– Dr. Steven Driese

– Dr. Don Parker

– Dr. Forman

– Todd Longbottom

– Ken Bolling

Content

• Research Objectives

• Motivation • Source rock evaluation methods.

• Goals of Study • Results • Conclusions

Objectives

• To relate structural characteristics of the organic matter in source rocks to their pyrolysis behavior during Rock-Eval™.

• Develop a predictive relationship for estimating hydrocarbon potential using highly correlated chemical parameters.

Motivation

Oil Shale Commercialization

-Provides 91% of Estonia's electricity.

-Full Industry Complex 50,000bpd in Utah by 2024.

- EcoShale™ In-Capsule Process expected to produce 400 million barrels of oil over next 20 years.

-First major production in North America in decades

Not shale oil.

SOURCE ROCK EVALUATION

• What is a source rock?

• A sediment containing

sufficient organic matter to be a future source of hydrocarbons.

Classification of organic matter in source rocks Lacustrine Deposit

High H/C and low O/C

Terrestrial Deposit (humic coals) Low H/C and high O/C

Chemical structure of kerogen (Type I)

Long Aliphatic chains Low aromatic content.

Chemical structure of kerogen (Type II)

Medium aliphatic chains. Increased aromatic content.

Chemical structure of kerogen (Type III)

High aromatic content. Short aliphatic chains.

Rock-Eval pyrolysis ™

Thermal degradation of kerogen

Solid-State 13C NMR

Fig. 13C CP NMR spectra layout and functional groups.

Values were obtained by cross polarizarion13C NMR spectroscopy, data from: Bushnev et al., 2009

Hypothesis

• Hydrocarbon potential (S2) is linked to:

– 1. Total organic carbon (TOC %wt)

– 2. Intensity of aliphatic carbon peaks <90ppm

• dipolar-dephasing 13C NMR spectra is linked to:

– 1. Free hydrocarbons already generated (S1)

How do structural characteristics of kerogen affect pyrolysis products?

• Area of study • Location: Woodway,

TX

• Formation: Eagle Ford Shale

• 9 samples • TL-1-9

13C Nuclear Magnetic Resonance

• 300 MHz Solid-State Nuclear magnetic resonance spectroscopy.

• Cross Polarization and Dipolar-Dephasing experiments performed on each sample.

Quantitative 13C NMR spectra of kerogen

Fig. Solid-state 13C NMR Spectra of sample TL-8 obtained using the cross-polarization (upper) and dipolar-dephasing (lower) techniques. Also identified in the spectra are several of the dominant chemical functional groups.

Rock-Eval pyrolysis ™ results

TOC†(wt.%)

S1

(mg/g)

S2

(mg/ g)

S3

(mg/g)

Tmax

(ºC) %Ro

HI

(s2x100)/

(TOC)

OI

(s2x100)/

(TOC)

TL1 9.49 1.06 61.31 1.39 408 0.18 646 15

TL2 7.21 1.07 45.49 1.67 410 0.22 631 23

TL3 8.19 0.96 53.44 1.46 412 0.26 653 18

TL4 3.76 0.18 14.26 1.73 421 0.42 379 46

TL5 5.43 0.22 17.99 3.35 419 0.38 331 62

TL6 7.91 0.34 35.29 2.82 411 0.24 447 36

TL7 2.00 0.47 3.58 0.54 421 0.42 179 27

TL8 4.93 0.32 26.05 1.08 416 0.33 528 22

TL9 0.94 0.01 1.26 0.30 431 0.60 134 32

Rock Eval results for samples TL-1 to TL-9, obtained from GeoMark Labratories LTD.

TOC = total organic carbon, data from Boling (2013) [8]

Kerogen quality plot relating TOC to potential oil yields.

TL-1

TL-2

TL-3

TL-4 TL-5

TL-6

TL-7

TL-8

TL-9 0

10

20

30

40

50

60

70

80

0 2 4 6 8 10 12

Po

ten

tial

Oil

Yie

ld S

2 m

gHC

/gR

ock

Total Organic Carbon, TOC (wt %)

Type I: Oil Prone

Type III: Gas Prone

Mixed Type II / III:

Oil / Gas Prone

Type II: Oil Prone

Usually Marine

NMR measurements of chemical structure to Rock-Eval pyrolysis products

s1 s2 s3 Tmax %Ro HI OI

faN -0.665 -0.755 -0.500 0.762 0.766 -0.792 0.120

faP -0.556 -0.491 -0.042 0.364 0.370 -0.585 0.171

faS -0.262 -0.484 -0.789 0.450 0.456 -0.475 -0.351

faB -0.663 -0.783 -0.554 0.880 0.881 -0.789 0.190

fal 0.491 0.467 0.201 -0.343 -0.349 0.576 -0.002

falH 0.461 0.365 -0.002 -0.249 -0.252 0.482 -0.069

fal* 0.461 -0.744 -0.618 0.855 0.852 -0.855 0.098

falO 0.182 0.434 0.588 -0.496 -0.499 0.456 0.065

Tabulated R values were calculated by the Microsoft Excel using CORREL function. Values highlighted in red show a strong positive correlation (R>0.75) Values highlighted in green represent a strong negative correlation (R<-0.75).