kerogen

Petroleum System Modelling applied
to the evaluation of HC in Place in
Unconventional Gas Shale prospects
Domenico Grigo
28 April, 2011
www.eni.it

PSM applied to Gas Shale Prospect characterisation
Why
PSM
In the first phase of a non american gas shale prospect
evaluation the well data resolution is so large that the normal
approach (quantification of well data only) is not enough to
describe properly the properties distribution.
American Gas Shale (Barnett)
Prospect well data
The estrapolation of well data to the entire prospect extension
can be succesfully supported by the numerical simulation of
the natural processes gouverning the properties distribution.
Petroleum System Modelling is the only methodology capable
to reproduce natural processes starting from well data at basin
scale
Non American Gas Shale
Prospect well data
250 km
1000 km
2

Methods for characterising a Gas Shale
The North American analog
PSM
Key characteristics noted about each system (where available)
Time equivalent system Total porosity (%)
Basin
Age
TOC (%)
Kerogen type
Thermal maturity (%R o )
Gas in place (bcf/section)
Shale gas-in-place resource (tcf)
Absorbed gas (%)
Matrix permeability
Relative thickness
Reservoir pressure (psi)
Bottom-hole temperature (°C)
Depositional setting*
Basin type/ tectonic setting*
Lithology notes
Other notes
* Hypothesized as potential common denominator
3

Methods for characterising a Gas Shale
The North American analog
PSM
4

Gas Shales: unconventional reservoir
PSM
Gas accumulation is continuous and not related to buoyancy
The formation is simultaneously source rock and reservoir
Gas presence is not associated to geological traps: the target is a
portion of basin
Gas production achieved only with fracture stimulation
Not all the shale gas plays can commercially produce gas
Key geological factors are:
TOC >1% with %Ro>1,2
Quality of organic matter: type II kerogene is the most favourable
Vshale3500 m can
be acceptable
5

PSM
Gas Shale Maturity
6

Maturity Indicators
20
15
Depth (m): 1892,5
Sample Type: BC
Ro=0.60% - Std Dev. =0.06
PSM
•Vitrinite Reflectance (Ro%)
records only the maximum temperature
reached during burial
N° of Readings
10
5
0
0 0.5 1 1.5 2
Vitrinite Reflectance (Ro%)
•Apatite Fission Track (AFTA)
records also other temperatures but only if
younger than the maximun
•Fluid Inclusions (FI)
records all the temperatures
7

Equivalent Vitrinite Reflectance (Ro %)
Derived by Bitume reflectance
PSM
Vitrinite is often scarse in carbonate source rocks. Bitumen can
be present in this case, in particular when the maturity level is
middle/high.
By the use of Jacob’s formula
(Jacob & Hiltmann, 1985) it is
possible to convert the bitumen
reflectance in equivalent
vitrinite reflectance value:
Ro eq % = 0.618 R BIT + 0.40
5
8

Equivalent Vitrinite Reflectance (Ro %)
Derived by other organisns
PSM
From Suchy et Al. 2004
CAI = Conodont Alteration Index
9

Equivalent Vitrinite Reflectance (Ro %)
Tmax by pyrolysis Rock-Eval
PSM
This maturity parameter is derived by the Rock-Eval analysis
(the analytical technique finalized to source rock evaluation).
Tmax is the temperature at
which the maximum of
residual petroleum potential
(by kerogen pyrolysis)
occurs.
It has not be confused with
the maximum temperature
(very lower) reached by
sample during its burial
history.
S1
Immature sample
T max = 420 °C
S2
Mature sample
T max = 450 °C
300 300 400 500 °C
Heating rate = 25°C per minute
Overmature sample
T max not
available
10

Petroleum System Modelling
Well Temperature & MaturityCalibration
PSM
WELL
DATA
20
70
Measured
Computed
0
1000
SURFACE
TEMPERATURE
0
1000
WELL BURIAL
EVALUATION
H000
H100
H200
H300
H400
H500
H600
GS
H800
H900
TEMPERATURE HISTORY
120
170
220
Temperature (°C)
TEMPERATURE
MATCHING
2000
Depth (m)
3000
4000
5000
HEAT
FLOW
Depth (m)
2000
3000
4000
5000
6000
7000
150
H000
H100
H200
H300
H400
H500
H600
GS
H800
H900
100
50
Time (ma)
0
150
H000
H100
H200
H300
H400
H500
H600
GS
H800
H900
100
Time (ma)
50
270
0
0.20
0.70
1.20
1.70
2.20
Maturity (Ro%)
6000
0 50 100 150 200 250
Temperature (°C)
Measured
Computed
0
1000
2000
Depth (m)
3000
4000
150
MATURITY HISTORY
100
50
Time (ma)
2.70
3.20
0
MATURITY
MATCHING
0 1 2 3 4
Ro%
5000
6000
11

Maturity Computation & Potential Gas Shale definition
PSM
1000 km
Gas Shale Maturity
12

PSM
Gas Shale Properties
13

Kerogen
ENVIRONMENT
Aquatic
KEROGEN
TYPE
I
KEROGEN FORM
[ MACERAL]
alginite
ORIGIN
algal bodies
structureless debris of
algal bodies
HC
POTENTIAL
PSM
The potential to generate hydrocarbons and the quality of the products are affected by
the quality of the initial kerogen, which is controlled by the quality of the organic input
and by the evolution of diagenesis.
On the basis of optical examination and physicochemical analyses, kerogens have been
gathered into four main groups:
Terrestrial
II
III
IV
amorphous
organic
matter
exinite
vitrinite
inertinite
(modified, after Merrill, 1991)
structureless, planktonic
material,
primarily of marine origin
skins of spores and pollen,
cuticle of leaves and
herbaceous plants
fibrous and woody plant
fragments and strcturless
collidal humic matter
oxydized, recycled woody
debris
OIL
GAS AND
SOME OIL
NONE
GENETIC
POTENTIAL
+
-
14

Steps of Organic Matter evolution
Diagenesis is strongly
controlled by the biological
activity (bacteria), and by the
chemical environment (redox
conditions, mineralogy).
At the end of diagenesis,
the organic matter consists mainly
of a policondensed structure which
is the kerogen.
Catagenesis and
Metagenesis, are controlled
by thermal stress due to burial
Both the absolute
temperatures and the heating
rate govern the evolution of
kerogen transformation.
≅
-
10 m
THERMAL
EVOLUTION
+
MACROMOLECULES
INITIAL KEROGEN
KEROGEN
KEROGEN
DEGRADATION
RESIDUAL KEROGEN
(after Bordenave, 1993 modified)
early
diagenesis
diagenesis
catagenesis
metagenesis
PSM
C,H,O,N
N
C,H,O
O
C,H
H
C
15

Source Rock
Evaluation
Source rock Evaluation: Geochemical log
Quantitative analysis
Source potential
Qualitative analysis
PSM
Thermal Maturity
FORMATION
MARNES
DE
MADINGO
450
TOC S2
HI KEROGEN
TMAX
COMPOSITION
P F G VG P F G VG 450
450
III II I IMM M V M
DOLOMIE DE
LOANGO
950
950
950
GRES
DE
TCHALA
CARBONATES DE SENDJI
1450
1950
1450
1950
TRACES
TRACES
1450
1950
SALIFERE DE LOEME
2450
2450
Oil prone
AOM
MPH
CHF
CWF
2450
ARGILES DE
POINT INDIENNE
T.D. 2782
0 1 2 3 4 5 6
(%)
0 1 10 100
(kg HC/ton of rock)
0 200 400 600 800 1000
(mg HC/g TOC)
0 20 40 60 80 100
(%)
Serie1
400 420 440 460 480 500
(°C)
16

Kerogen optical analyses
Some kerogen types are shown:
Microscope pictures of kerogens
Observation in transmitted white light
PSM
_________________
More or less 100 µ
1. Humic Kerogen
(woody fragments, and then vitrinite
and others coal macerals)
2. Sapropelic Kerogen
(spores and pollens)
3. Kerogen constituted by
Amorphous Organic Matter
(unstructured, unrecognizable OM)
17

The Seismic view of a Source Rock
PSM
18

Source rock lithological model
PSM
(50-80% shale)
(80-90% shale)
(90-100% shale)
19

Organic matter deposition & preservation modelling
PSM
OF-Mod 3D:
is a process-based software, which reproduce the development
and the variation of organic facies in a 3D volume.
TOM supply
1 fluvial sediment
primary productivity PP (g C·m -2·a-1 )
and nutrient supply
CO 2 + H 2 O CH 2 O + O 2
PP = 250 - 300 g C·m-2·a-1
PP = 50 – 60 g C·m -2·a * -1 *
* *
*
*
PP = 100 - 250 g C·m *
*
-2·a * * * *
* * *
*-1
2 * *
*
*
*
* * * * * *
*
* * * *
2
*
* * *
* *
* *
* * * *
* *
3 * * * * * ***
*
carbon flux
* *
Fc
* * *
*
*
*
*
*
*
*
*
*
*
*
* * * * ** 4 *
*
*
*
4
* * * **
*
Ctot: 10 wt%
Ctot: 7 wt%
degradation
OF: B
OF: C - A
* 6
*
MOC (anoxic)= PP · PF · dilution
epibenthic respiration
5
*
Ctot: 1-3 wt%
BFM erosion, bypass and
OF: BC-C
burial efficiency BE
sedimentation processes
Ctot: 0.3 wt%
OF: D MOC (oxic) = Fc · BE · dilution
water depth (m)
TOM = Terrestrial Organic Matter
SINTEF Petroleum Research
20

Final Outcome:
Gas Shale Thickness & Original properties definition
PSM
Original TOC=15%
Original HI=350
mgHC/gTOC
1000 km
21

Final outcome:
Gas Shale Depth & Burial Evolution
PSM
1000 km
22

PSM
Gas Shale original Gas in place
23

HC genaration simulation
Experimental Kinetic Parameters
The parameters defining the reaction scheme are determined experimentally
degrading thermically the kerogen samples with the MSSV (Micro Scale
Sealed Vessel) pyrolysys experiments
OPTIMIZATION OF RESULTS
PSM
ACCORDING TO A KINETIC SCHEME
USE IN THE
SIMULATION OF
HC GENERATION
AND EXPULSION
24

Calibration of the Kinetic Model
Original properties definition
PSM
Av. Source Rock Maturity 1.6 Ro%
TOC (%)
0 1 10 100
4400
HI mgHC/gTOC
1 10 100 1000
4400
4420
4420
4440
4440
Measured
Measured
Computed
4460
Depth (m)
Computed
4460
Depth (m)
4480
4480
MODELLED GAS SHALE
15 % TOC – HI 350
mgHC/gTOC
38 m
4500
4520
4500
4520
25

Expulsion Simulation Why
PSM
GENERATED GAS EXPELLED GAS
Between Generation and Expulsion of HC a time gap can exists but
also a volume gap due to the un-expelled HC remaining in the
source and not available for Migration and Charging
26

Final outcome:
Gas Shale OGIIP Volumes by area
PSM
The same process of
evaluation can be
applied at any scale
from the basin to the
block following the
maturation of the Gas
Shale exploration
project
1000 km
27