OGS New Perspectives on Shales – July 28, 2010

From Oil-Prone Source Rock to

Gas-Producing Shale Reservoir –

Geologic and Petrophysical

Characterization of

Shale-Gas Reservoirs

Q. R. Passey, K. M. Bohacs,

W. L. Esch, R. Klimentidis, and S. Sinha,

ExxonMobil Upstream Research Co.

OGS New Perspectives on Shales – July 28, 2010

Organic Matter Type

OGS New Perspectives on Shales – July 28, 2010

Maturity (LOM/Ro) – Type II

Kerogen and Coal Rank

OGS New Perspectives on Shales – July 28, 2010

Controls On Organic-Richness

OGS New Perspectives on Shales – July 28, 2010

Luman Tongue, Hiawatha Section, Green River Basin, WY

1-2 m thick Parasequences

in Mudstones

OGS New Perspectives on Shales – July 28, 2010

Parasequence Lithofacies

Stacking Pattern

OGS New Perspectives on Shales – July 28, 2010

Woodford Shale –

20 wt% TOC 40 vol% Kerogen

OGS New Perspectives on Shales – July 28, 2010

TOC Variablility in

Exshaw Formation

OGS New Perspectives on Shales – July 28, 2010

Vertical Variability

Scale of cm to meters

TOC (wt%)

0 5 10 15 20 25 30

2277

2277.44

2277.88

2278.32

2278.76

2279.2

2279.64

2280.08

2280.52

2280.96

2281.4

2281.84

2282.28

2282.72

2283.16

2283.6

Gamma Ray

< 3

m>

OGS New Perspectives on Shales – July 28, 2010

Variation in Lithology for

Shale Gas Formations

OGS New Perspectives on Shales – July 28, 2010

Maturity Impact on

Log Response

OGS New Perspectives on Shales – July 28, 2010

TOC from logR and

Borehole Image Log Response

OGS New Perspectives on Shales – July 28, 2010

Physiographic Setting of

Organic-Rich Mudstones

OGS New Perspectives on Shales – July 28, 2010

Definition of Total & Effective

Porosity for Shale-gas Reservoirs

OGS New Perspectives on Shales – July 28, 2010

0

2

4

6

8

10

12

14

16

1 2 3 4

Rep

ort

ed

Po

rosit

y (

p.u

.)

Sample #

Comparison of Reported

Porosity from Different Labs

OGS New Perspectives on Shales – July 28, 2010

Impact of “Porosity” Definition

on Calculated Gas Saturation

OGS New Perspectives on Shales – July 28, 2010

Recrystalized Biogenic Silica

and Pores in Organic Matter

OGS New Perspectives on Shales – July 28, 2010

TOC versus Total Porosity

in Shale Gas Reservoir

OGS New Perspectives on Shales – July 28, 2010

Preserved Samples

Non-Preserved Samples

Porosity versus Gas-filled

Porosity in Shale Gas Reservoir

OGS New Perspectives on Shales – July 28, 2010

TOC and Sg are Correlated

OGS New Perspectives on Shales – July 28, 2010

Pore Size Comparison – Fine

Sandstone versus Organic-matter

OGS New Perspectives on Shales – July 28, 2010

TOC wt% TOC vol%

OGS New Perspectives on Shales – July 28, 2010

3D Representation Pores

within the Organic Matter

OGS New Perspectives on Shales – July 28, 2010

Hypothetical Distribution

of Gas and Water

OGS New Perspectives on Shales – July 28, 2010

Summary

• Production, destruction, and dilution control TOC in mudstones

• Parasequence is the fundamental unit of shale gas reservoirs

• Shale-gas reservoirs are overmature oil-prone source rocks

• Porosity, TOC, and gas content are all positively correlated

• Shale-gas reservoirs comprise a large range in matrix lithologies

• Laboratory characterization of , k, and Sg is problematic

• Free gas likely to be in organic-matter porosity

• Gas-filled porosity (BVG) is better characterization term than Sg

OGS New Perspectives on Shales – July 28, 2010

For Further Information –

SPE 131350