Basin and Petroleum Systems Modelling: Applications for Conventional and Unconventional
Petroleum Exploration Risk and Resource
Assessments
By Dr Bjorn Wygrala Schlumberger
21-22 November 2013
6. Petroleum Generation
and Migration
Education Days Moscow 2013
2
1. Opening Session: Industry Challenges and Opportunities
Conventional Petroleum Systems
2. Deepwater and Salt
3. Structural Complexity
4. Reservoir in Petroleum Systems Modeling
Theoretical Aspects
5. Temperature and Pressure
6. Petroleum Generation and Migration
Unconventional Petroleum Systems
7. Shale Gas/Oil
8. Gas Hydrates
9. Closing Session: Petroleum Systems Modeling in Context
Processes, Models and Features
Temperature Pressure
Heat Flow Analysis
with Crustal Models Pore Pressure Analysis
with Compaction
Kinetics Petroleum Generation
Multicomponent
Reactions
PVT
Fluid Flow
Petroleum Migration
& Accumulation
Darcy Flow, Invasion
Percolation, Flowpath
and Hybrid Modeling;
all multi-component
Fluid Properties
Flash Iterations
Geomechanics Rock Stresses
Seal Failure and
Fault Properties
4
From: TISSOT & WELTE (1984)
Petroleum Migration Definitions
5
Key factors of HC migration
Why do hydrocarbons migrate??
Hydrocarbons are lighter than water buoyancy
Hydrocarbons migrate as a separate phase from the
higher potential to a lower potential on the direct
way topography driven
How do hydrocarbons migrate??
6
Petroleum Migration Mechanisms and Rates
Migration Mechanism Migration Rate
Hydrodynamic 0.1 to 100 m/year
Compaction 0.001 to 1 m/year
Buoyancy Meters per day (gas)
Diffusion 1 to 10 m / m.a.
Matthews (pers. comm.)
7
Properties and Processes: Capillary Pressures
The effect of interfacial tension is to create a finite pressure difference
between immiscible fluids called the capillary pressure:
Pc = Pnw - Pw
with Pw = wetting phase and Pnw non-wetting phase
Capillary pressure depends on the properties of the fluids and solid
surfaces, swa and cosqwa, and the tube radius, r.
When adhesion > cohesion, adhesive forces draw the fluid up the tube
until they are balanced by the weight of the fluid column.
When cohesion > adhesion, cohesive forces drag fluid down the tube
until they are balanced by the weight of the head difference forcing fluid
upwards.
8
Properties and Processes: Capillary Pressures
9
Petroleum Migration Modeling Methods
Darcy Flow Flowpath Invasion Percolation
Source: Barenblatt:
Theory of Fluid Flow
Through Natural Rocks.
1000 m
1 cm
Upscaling What is the best practice?
10
Darcy
Petroleum Migration Modeling Methods
11
Leakage
re-migration
Image courtesy BG International
Three Phase Flow through Porous Media and Multicomponents
Darcy Flow
12
Fluid Flow - Darcy Flow
The flow of vapour or liquids can be quantified using Darcy’s Law.
gradpk
dx
dpk
A
JQ
Q = Darcy velocity [m/s], [m2/m2/s]
J = volumetric flow [m3/s]
A = Area [m]
= dynamic viscosity [Pa*s]
dp/dx= gradient [Pa/m]
The constant of proportionality (k, permeability) obtained by Henri
Darcy depends on the properties of both the fluid (in Darcy’s
experiments, water) and the porous medium (in Darcy’s
experiments, sand and gravel).
13
Reservoir in Static Equilibrium
0 S Swc co 1p
in t
Sw
pc
0 S Swc co 1Sw
12
3
45
Cell
1 Res. 1 0.1 6.1
2 Res. 1 0.1 5.7
3 Res. 55 0.5 5.74 Res. 95 0.9 5.7
5 Res. 96 1.3 5.7
6 Seal 1 1.7 5.7
S p uo c o
[%] [Mpa] [MPa]
Seal
Reservoir
2
3
4
5
6
6
pc
pin t
pce
pce
9080706050
40302010 0
Oil Saturationin %
a)
5.7
5.75.7
5.7 5.7
5.7 5.7
5.3
6.16.5
4.5
4.9
Regions of varyingoil potential and
critical oil saturation
Region of uniformoil potential
4.504.755.005.255.50
5.756.006.256.50
Oil Potentialin MPa
b)
Seal
Reservoir
14
Flow Rates
15
Darcy Flow Modeling: Pros and Cons
Concept: Based on equations of flow through porous media
Advantages:
• Good general definition of carrier and seal system
• Easy inclusion of complex migration and transport processes such as multi-phase migration,
gas diffusion and PVT controls
• Only method that fully integrates pressures into the modeling process
Disadvantages:
• Long processing times, especially with large 3D data models
• For acceptable processing times, models must be simplified with resulting loss of information
• Pitfalls: Cannot accurately handle accumulations and breakthroughs (e.g. 'thin reservoir'
problem); property scaling (e.g. saturation of large cells)
Leakage
re-migration
Image courtesy BG International
up
16
Flowpath
Petroleum Migration Modeling Methods
17
Break Through Spilling
Challanges:
- Impermeable and Permeable Faults
- Migration Losses
- Hydrodynamics
Capillary
Pressure
HC-Column
Pressure
... ...
Flowpath Modeling
18
Principle Scheme of Flowpath Modeling
Oil
Gas
Source Rock
Top Carrier
Top Carrier
Top Carrier
Stacked Reservoir System
Expulsion from Source
Leakage
Spilling
GasFlowpaths
OilFlowpaths
19
Spilling and Merging
20
Capillary
pressure
HC
column
pressure
distribution throughout entire reservoir
... ...
HgHgIFT
PetPetIFTHgcPPet
cP
cos
cos
Petroleum Densities
Petroleum IFTs
HG-Air Capillary Pressures
)( petwg
cPh
Column Heights
21
Flow Path (ray tracing) Modeling: Pros and Cons
Concept: Geometrical surface analysis (buoyancy driven migration)
Advantages:
• Fast processing
• High resolution modeling
• Accurate reservoir geometries can be included
Disadvantages:
• Incomplete physical model of petroleum migration
• Arbitrary definitions of the migration system, e.g. of seals
• Not suitable for complex migration processes in certain types of petroleum systems
• Pitfalls: Misleading simplicity (e.g. not taking facies changes in carriers into account in simple
models)
up
22
Invasion Percolation
Petroleum Migration Modeling Methods
23
Invasion Percolation
Fully Integrated Migration Mode
Cell-Based (Irregular) Percolation Grid
Integrated Multicomponent (3-Phase) PVT (Flash) Model
Seismic Link
24
Academic Example: 2 Phase
Invasion Percolation
25
Noise (Capillary Pressure Heterogenities)
Without 'Noise' With 'Noise'
Invasion Percolation
26 26
Invasion Percolation
Depth
Shale
Sand
Oil
Shale
Oil
ShaleShale
Oil
Sand Sand
Oil
27
Gridding: Flowpath vs. Percolation
Flowpaths traverse grid
in arbitrary direction
Percolation
Without Noise With Noise
wrong
28
Invasion (Capillary) Percolation: Pros and Cons
Concept: Flow controlled by capillary forces only
Advantages:
• Very fast processing of single phase HC flow
• High resolution modeling, for example on seismic-scale data including 3D ... if seismic is
converted to meaningful properties
• Multiple charge scenarios can be tested quickly
Disadvantages:
• Slow performance with 3-phase in 3D, and very slow with multi-component modeling and
source tracking
• Pitfalls: Only 'pretty pictures' if seismic is not converted meaningfully to properties; high
resolution can be misleading (see e.g. 'thin bed' problem); very sensitive to controls
parameters (e.g. noise settings and 'angled bed' problem)
up
29
Hybrid
Petroleum Migration Modeling Methods
30
Petroleum Migration Modeling: Modeling approaches
Temperature
/ pressure
additional
migration
modeling migration
modeling
'Standard' Sequential Hybrid Full Hybrid
Input
migration
modeling
Temperature
/ pressure
Temperature
/ pressure
/ migration
Input Input
Output Output Output
31
Darcy Flow Analysis
Flowpath Modelling
Domain Decomposition
32
Darcy Flow
Finite Element –
Sampled Grid (100x100)
Flowpath Map
Fine Grid (300x300)
Hybrid Modeling Results
33
Equilibrium Approach (Multilayer Flowpath Modelling, Perculation Analysis)
- all column heights are smaller or equal to the capillary pressures of the seal
Disequilibrium Reservoirs due to
- migration smaller then generation
- viscous effects
- rest saturations
Change in Wettebility can yield to
Entire Outflow
- component polarity controlled
Generated Masses of one Timestep
Seal Breakthrough
34
Input
Regional facies mapping based on
seismic attributes
High Permeability Facies
Low Permeability Facies
Full 3D Hybrid modeling automatically
assigns the optimum migration modeling
method according to the properties in the
geologic model ... and provides by far the
best match to the known accumulations
Output
Model: Campos (Brasil)
Source: Wintershall
Hybrid Modeling
35
Hydrocarbon Migration
Rift stage source rock with transformation overlay and accumulation bodies, vectors and
flow paths
HC Migration
in Miocene
Model: Santos (Brasil)
Source: HRT
36
Comparison of Methods
Petroleum Migration Modeling Methods
37
Comparison of Migration Methods
Hybrid
Closed Fault
Closed Fault
Accumulation
FlowVectors
Big Circle: LiquidSmall Circle: Vapor
Closed Fault
Closed Fault
Invasion Percolation
Liquid
Vapor
Breakthrough
Flowpath
Big Circle: LiquidSmall Circle: Vapor
LithologyShale sandySand shalyDolomiteSilt shalySandChalkMarlShale sandySaltBasement
38 38
Hybrid and Invasion Percolation
RONCADOR RONCADOR
Roncador Field, Campos Basin, Brazil
RONCADOR RONCADOR
70% SR-2 ~ 30% SR-1 85% SR-2 ~ 15% SR-1
Hybrid IP
Reserves: ~ 3.0 BBOIP
API: ~ 30.0º
GOR: ~ 125 m3/m3
Reserves: ~ 2.6 BBOIP
API: ~ 33.0º
GOR: ~ 140 m3/m3
39
IP Hybrid Shengli
Hybrid and Invasion Percolation
same API
(different GOR)
40
Migration Modeling Methods: Advantages / Disadvantages
Dynamics ++ - -
Scaling - + +
Processing speed -- + + -
Data availability + + +
Source and expulsion + - -
Migration – low perm. units + -- +
Migration – high perm. carriers - ++ +
Reservoir bodies -- ++ +
Darcy Flowpath Percolation
Petroleum Systems Components:
3D Modeling Requirements:
Conclusion: There is no method that provides an acceptable solution for 3D
modeling if used on its own!
41
PVT Modeling
Petroleum Migration Modeling Methods
42
Component Mol% Mass%
CO2 0.91 0.43
N2 0.16 0.05
C1 36.47 6.24
C2 9.67 3.10
C3 6.95 3.27
iC4 1.44 0.89
nC4 3.93 2.44
iC5 1.44 1.11
nC5 1.41 1.09
C6 4.33 3.97
C7+ 33.29 44.71
?
Volume
Liquid, Vapour, (Water) Phase
Composition
Liquid, Vapour, (Water) Phase
Density
Liquid, Vapour, (Water) Phase
Viscosity
Liquid, Vapour, (Water) Phase
p
T
p, T Separator
GOR, API Density
Multicomponent PVT-Analysis: Main Tasks
Liquid
Vapour
HC Components HC Phases
43
The Phase Concept
A phase is defined as a mechanically separable body of matter with distinct
physical and chemical properties.
E. g. ice, water and steam are representing the solid, liquid and gaseous phase
of pure H2O.
A component is one of a set of arbitrarily chosen chemical entities that, taken
together, completely describe all chemical variation within a system. No
component may be a linear algebraic combination of two or more other
components in the same system.
E. g. methane, ethane, nitrogen (N), oxygen (O), sulfur (S)...
The phase concept is a potential tool for the prediction of hydrocarbon phases
within the reservoir ahead of drilling.
Knowledge of hydrocarbon phases in the prospect might significantly reduce the
risk of drilling an uneconomic reservoir. E. g. a gas field where the only
economically targets are oil fields.
44
LIQUID
VAPOUR (GAS)
C...Critical Point
Temperature
Pressure
T...Triple Point A
B C
pT Diagram of Pure Substance (single component)
45
LIQUID
VAPOUR
(GAS)
C...Critical Point
Volume
Pressure
A B
T = Tc
T < Tc
T > Tc
pV Diagram of Pure Substance (single component)
46
pT Diagram of a Mixture (two components)
Temperature
Pressure
LOW PRESSURE
HIGH PRESSURE
100%
0 % Vap
Liq
Bubble point li
ne
Dew point line
LIQUID
VAPOUR(Gas)
Critical condensation temperature
Critical Point
‘Cricondentherm’
liquid
liquid
47
pT Diagram of Ethane-Methane
48
Component/Phase Models: Component = Phase Model
C1
C2-C4
C5-C6
C7-C13
C13+
Vapour
Phase
Liquid
Phase
pure gas
pure gas
pure oil
pure oil
pure gas
49
Symmetrical Black Oil Model (SBO)
CO2
N2
C1
C2-C4
C5-C6
C7-C13
C13+
Pseudo-
Component
Gas
Pseudo-
Component
Oil
Bubble and Dew Point Curves
Gas Component
Oil Component
Gas Component
Oil Component
Vapour Phase
Liquid Phase
Vapour Phase
Liquid Phase
Components: Pseudo- Phases:
Components:
50
Flash Calculations
CO2
N2
C1
C2-C4
C5-C6
C7-C13
C13+
Vapour Phase
Liquid Phase
Solve Van der Waals Type Equations
Evaluate Fugacities
Correct Compositions
Estimate Compositions
51
Petroleum Migration Modeling: Flash Calculation Technology
Vapour phase hydrocarbons (red vectors) exsolving
from the single liquid phase at shallow depths due to
decreasing temperatures and pressures!
3-Phase / n-component migration modeling with flash calculations enables properties and compositions to
be more accurately determined for both in-situ and surface conditions!
52
HC Quality Prediction
Accumulated
HC’s
What it looks like
when it comes to the surface
Flashed to surface
conditions
Predicts API=35
GOR=39
53
Flash calculations 3-phase / n-component modeling
View of the
hydrocarbon
accumulation
with
volumetrics,
properties,
phase and
component
information
Flashed to
surface
conditions
At reservoir
conditions
Processes, Models and Features
Temperature Pressure
Heat Flow Analysis
with Crustal Models Pore Pressure Analysis
with Compaction
Kinetics Petroleum Generation
Multicomponent
Reactions
PVT
Fluid Flow
Petroleum Migration
& Accumulation
Darcy Flow, Invasion
Percolation, Flowpath
and Hybrid Modeling;
all multi-component
Fluid Properties
Flash Iterations
Geomechanics Rock Stresses
Seal Failure and
Fault Properties
