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Basin and Petroleum Systems Modelling:
Technology and Applications for Petroleum Exploration
Risk and Resource Assessments
SLT Europe 2012-2013
By Dr Bjorn Wygrala
Schlumberger
EAGE Student Lecture Tour: Basin and Petroleum Systems Modeling
EAGE Student Lecture Tour 2012-2013
Basin and Petroleum Systems Modeling:
Technology and Applications for Petroleum
Exploration Risk and Resource Assessments
Course Note
Bjorn Wygrala, PhD
Schlumberger Aachen Technology Center (AaTC)
Ritterstraße 23
52072 Aachen
Germany
Email: bwygrala@slb.com
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EAGE Student Lecture Tour: Basin and Petroleum Systems Modeling
Copyright Notice
2012 Schlumberger. All rights reserved.
No part of this document may be reproduced, stored in an information retrieval system, or
translated or retransmitted in any form or by any means, electronic or mechanical, including
photocopying and recording, without the prior written permission of the copyright owner.
Trademark Information
* Mark of Schlumberger. Certain other products and product names are trademarks or
registered trademarks of their respective companies or organizations.
Schlumberger Aachen Technology Center (AaTC)
Ritterstraße 23
52072 Aachen
Germany
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EAGE Student Lecture Tour: Basin and Petroleum Systems Modeling
Contents
Introduction .......................................................................................................................4
Foreword .................................................................................................................................4
Abstract ....................................................................................................................................4
Oil and Gas Resources and Exploration ...............................................................................5
Global Energy Resources and Petroleum Exploration .............................................................5
Conventional and Unconventional Resources .........................................................................5
Geological Risk Factors in Exploration .....................................................................................6
Basin and Petroleum Systems Modeling .................................................................................6
Petroleum Systems Modeling Technology ..........................................................................9
Thermal History Modeling .......................................................................................................9
Pore Pressure Prediction .......................................................................................................10
Petroleum Generation and Expulsion ...................................................................................10
Petroleum Migration Modeling .............................................................................................11
Special Modeling Technology ................................................................................................13
Summary of Principle Results ................................................................................................14
1D vs 2D vs 3D Petroleum Systems Modeling .......................................................................15
Case Studies .....................................................................................................................18
Brazil: Campos Basin Subsalt Exploration ..............................................................................18
USA: Alaska North Slope Conventional and Unconventional Exploration ............................18
Brazil: Potiguar/Ceara Basin Deepwater Exploration ............................................................19
Venezuela: Santa Barbara Thrustbelt Exploration ................................................................19
USA: San Joaquin Basin/California .........................................................................................20
Appendix ..........................................................................................................................21
Further Education and Career Opportunities ........................................................................21
References and Recommended Reading ...............................................................................21
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EAGE Student Lecture Tour: Basin and Petroleum Systems Modeling
Introduction
Foreword
These Lecture Notes describe the general content of the lecture, however they are not
copies of the presentations, as most of the lecture will be live software presentations of
applications. The intent is also to give the audience an opportunity to obtain information in
advance, to follow the lecture without being distracted, and to enable the lectures to be
customized to specific requirements and updated if necessary.
Abstract
The stage will be set with general information about petroleum exploration and production
(E&P) and how the industry operates. The goal is to give the audience a feeling for the scope
of the task as well as of the scale, costs and risks of the operations and of the investments
and decisions that have to be made.
Basin and Petroleum Systems Modeling will then be introduced, starting with the rationale
for models and process modeling in the geosciences, and followed by an introduction to the
data types, workflows and goals of typical applications. Rather than just showing these
points in theory, a case study will be used in a live software presentation to illustrate all of
these points. Audience participation and questions will be encouraged in order to ensure
that the key issues are understood. This part will conclude with a summary of the roles of
the various geoscientific disciplines and show that the technology is integrative and can only
be successfully applied with a truly interdisciplinary approach.
The technology itself will then be introduced in more detail. What are the controlling factors
for the development of oil and gas resources, and how can these be simulated with
geological process modeling in order to at first understand petroleum distributions and
properties, and then to predict them. As petroleum generation is primarily a function of
temperature and geologic time, thermal history modeling is the first step. As distributions of
oil and gas and in particular their phase are controlled by temperatures and pressures,
pressure history modeling is then introduced. This is followed by a review of the methods
that are available to simulate the entire process of petroleum generation, expulsion,
migration, accumulation and loss in petroleum systems, and a discussion of special technical
challenges such as geomechanics.
Applications of the technology will then be presented, with options ranging from frontier
exploration in which large areas with only sparse data are screened, to petroleum resource
assessments of yet-to-find oil and gas, to detailed assessments of exploration risks in
structurally complex areas, as well as applications for unconventional oil and gas
exploration.
The lecture will conclude with some key references and recommended reading, as well as a
review of academic and professional opportunities to show possible next steps that can be
taken by the students to develop their careers.
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EAGE Student Lecture Tour: Basin and Petroleum Systems Modeling
Oil and Gas Resources and Exploration
Global Energy Resources and Petroleum Exploration
Energy is the most important single resource to enable the essential functions of human
society to be performed at present and in the future. The acquisition and management of all
other resources are primarily controlled by the availability of energy. At present, fossil fuels
and especially petroleum (oil and gas) are the most important source of energy and this will
remain so for many decades. The value of these energy resources is substantial and
enormous financial resources are required to find, produce, and distribute petroleum and
petroleum products. It is therefore not surprising that the Petroleum Exploration and
Production (E&P) industry is one of the largest global industries. The risks and the required
resources are particularly high in petroleum exploration, and examples will be shown to
demonstrate the scale, costs and risks that the E&P industry has to address.
The lecture will address the
Geoscience component of
petroleum exploration which
is only responsible for a
relatively small part of the
total cost of exploration, but
which has a critical effect on
the other significantly more
expensive components.
Conventional and Unconventional Resources
Oil and gas is the result of the thermal maturation of organic material that was deposited in
sediments (source rocks) and then subjected to increasing temperatures through geologic
time as the rocks were buried by overlying sediments. The original organic material is
converted to oil and gas as a function of temperature, time and the type of organic material.
It can then be expelled from the source rocks and migrate through a basin until it is trapped
by a favourable combination of structural, reservoir and seal properties. This process results
in conventional oil and gas which is defined as petroleum occurring as discrete
accumulations or fields, and which has been the principle target of exploration since the first
oil well was drilled more than 150 years ago.
However, generated oil and gas in source rocks can also be partially retained in the source
rocks, and major technical breakthroughs which were initially developed in the 1990s now
enable gas (and increasingly oil) to be directly produced from the source rocks. These shale
gas and shale oil plays are commonly described as ‘unconventional’ as opposed to
conventional oil and gas occurrences. However, these are not the only new, unconventional
resources: for example gas hydrates also have potential to be major energy sources in the
future. Both conventional and unconventional hydrocarbon resources will be addressed and
examples will be shown in the lecture.
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EAGE Student Lecture Tour: Basin and Petroleum Systems Modeling
Geological Risk Factors in Exploration
In petroleum exploration, the main geologic uncertainties and therefore the principle risk
factors are related to the 'essential elements' which are needed for a petroleum
accumulation to exist. These essential elements are always the same in any exploration risk
assessment, regardless of whether it is being performed on a basin, play or prospect scale.
They are:
- the Trap (geometry, reservoir, seal)
- the Hydrocarbon Charge (the amount of hydrocarbons which can reach the trap)
- the Timing relationship between the Charge and the formation of the Trap.
The term ‘petroleum system’ is used
in petroleum exploration to describe
the geological elements and processes
that need to be in place for a
petroleum accumulation to occur
(Leslie B. Magoon and Wallace G. Dow,
AAPG Memoir 60). These essential
elements are the source, reservoir,
seal and overburden rocks, and the
essential processes are petroleum
generation, migration and
accumulation, as well as the timing
relationship with the structural
evolution of the trap and its properties. The same geological principles apply in both
conventionals and unconventionals: in conventionals, exploration is directed at the expelled
and migrated hydrocarbons, while in unconventionals the retained hydrocarbons are of
interest.
There are some fundamental issues which must be taken into account:
- The principle of the 'weakest link' applies, i.e. if one of the essential elements Trap
Geometry, Reservoir, Seal, Hydrocarbon Charge or Timing is missing, a prospect will not
be viable.
- All geoscience data has uncertainties, most of which are significant. This applies to every
type of geophysical and geological data, as most data cannot be obtained directly and
quantifications are mostly subjected to scaling issues. Uncertainties are an inherent part
of every geoscientists work: their job is to make decisions based on uncertain data and
for this they need to be able to assess the effects of the uncertainties on their
assessments.
- As petroleum occurrences are the result of geological processes, deterministic analyses
are essential. However, uncertainties necessitate statistical analyses in order to
understand their effects. Both approaches are therefore required.
Basin and Petroleum Systems Modeling
Models are an essential part of any analysis. When we construct a geologic cross-section
from outcrop studies, we are constructing a model which represents our understanding of
the geology. Even if we have no data, we can construct conceptual models, for example
based on analogues. Models are never unique and never ‘correct’, but they are nonetheless
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EAGE Student Lecture Tour: Basin and Petroleum Systems Modeling
essential to structure, perform and communicate our analyses and they always evolve as
additional data is acquired and our understanding improves.
A Petroleum Systems Model is a digital data model of a petroleum system in which the
interrelated processes and their results can be simulated in order to understand and predict
them. A Petroleum Systems Model is a preferably 3D representation of geological data in an
area of interest, which can range from a single charge or drainage area to an entire basin. A
Petroleum Systems Model is dynamic which means that Petroleum Systems Modeling
provides a complete and unique record of the generation, expulsion vs. retention, migration,
accumulation and loss of oil and gas in a petroleum system through geologic time!
Petroleum systems modeling
is used to process geological
data models in conventional
and unconventional
petroleum systems in order to
obtain information on
parameters and processes
which control the generation
and accumulation of oil and
gas. They are used to improve
our understanding and then
to enable better predictions
to be made.
The technology originated in the mid 1970s when researchers in geochemistry, after
realizing that hydrocarbon generation was determined by temperature and geologic time,
developed and published the first usable chemical kinetics. The name 'basin modeling' was
then used to describe the first generation of tools but has gradually been replaced by the
term 'Petroleum Systems Modeling'. This was due to the definition and propagation of the
Petroleum Systems methodology, the increasingly widespread use of the term in the
industry, and the close match of the methodology and the modeling technology after the
introduction of petroleum migration modeling capabilities.
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EAGE Student Lecture Tour: Basin and Petroleum Systems Modeling
Petroleum systems modeling is now widely applied to address many aspects of the E&P
processes from early exploration to field development, as shown in the following diagram
(Dietrich Welte and Harald Karg).
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EAGE Student Lecture Tour: Basin and Petroleum Systems Modeling
Petroleum Systems Modeling Technology
Thermal History Modeling
As petroleum generation is a function of temperature and time, thermal history modeling is
the primary goal of petroleum systems modeling and temperature predictions are a key
application result.
Temperature distributions within a basin are the result of heat flowing into the base of the
sedimentary sequence and then being conducted through the sediments to their surface.
The controlling physical parameter is the bulk thermal conductivity of the rocks which is a
function of their matrix conductivity (which depends on mineral types and shapes) and the
conductivity of the pore fluids, and therefore of the porosity.
As sediments compact with increasing depths, their porosities and the amount of pore fluids
are reduced, so that their bulk thermal properties change. The thermal properties of a
specific stratigraphic unit will therefore change with increasing burial through geologic time.
The thermal gradient shows the temperature increase within a specific unit, and is a result
of the bulk thermal conductivity of the unit and the heat flow. High thermal conductivities
(e.g. in sandstones) will enable more effective heat transfer and the resulting temperature
increase will be lower. Low thermal conductivities (e.g. in shales) will retard heat transfer
and result in higher temperatures with the same heat flow input; this is often described as a
‘thermal blanketing’ effect by sediments such as shales. Thermal gradients will therefore
change in each rock unit and through geologic time. This means that using an overall or
average thermal gradient for an entire sedimentary column and through geologic time is
neither geologically nor physically meaningful. Additional complications in temperature
calculations arise from non-steady state conditions when burial rates are high and
temperature increases cannot ‘keep up’ with increasing burial rates, but most modern
thermal simulators can take these into account.
There can be other factors which need to be taken into account for accurate temperature
predictions. Heat flow is predominantly a vertical process, but rock units with differing
thermal properties such as salt domes (salt has very high thermal conductivities) will lead to
lateral distortions of the temperature field which can only be simulated with full 2D or even
better with full 3D thermal simulators. In some basins, convection processes, for example
due to regional aquifer flow systems, can distort the normal temperature distributions as
convection is an effective heat transfer process.
Basic thermal modeling tools use 1D or multi-1D thermal calculations which are sufficient for
first-pass calculations, but which can deliver insufficiently accurate results if geologic
conditions are more difficult as described in the preceding section. Full 2D or better 3D and
non-steady state thermal modeling solutions therefore always ensure the most accurate
possible calculations. Petroleum systems experts are therefore able to routinely predict
temperatures at great depths and with difficult geological conditions with a very high level
of accuracy.
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EAGE Student Lecture Tour: Basin and Petroleum Systems Modeling
Pore Pressure Prediction
Pore pressure and overpressure modeling is an inherent function of petroleum systems
modeling simulators in order to determine compaction behaviour, and they are therefore
widely used for pore pressure predictions. They are especially effective when used together
with seismic pore pressure prediction methods, as the strengths and weaknesses of the
methods can complement each other.
Overpressures are mainly the result of a
combination of high sedimentation rates and
low permeabilities in specific stratigraphic
units. Due to these factors, pore fluids
cannot escape quickly enough and
overpressures result. Modeling these
processes in a multi-dimensional model
which simulates processes through geologic
time is exactly what advanced petroleum
systems modeling simulators do.
Overpressure modeling can be done with 2D
petroleum systems modeling tools, but is
much more accurate in 3D, as property distributions can be taken into account more
accurately and all lateral effects can be taken into account. The image shows modeled
overpressure distributions in a Gulf of Mexico model.
Additional factors which can lead to overpressures can also be modeled. These include the
generation and expulsion of oil and gas within and from source rocks, the effects of
hydrocarbon phase changes, aquathermal pressuring and others.
Petroleum Generation and Expulsion
Petroleum (oil and gas) generation occurs when organic material in source rocks is exposed
to sufficient temperatures and time. The original organic material (kerogen) is cracked to oil
and gas as the thermal ‘load’ increases. Both temperature and time have an effect: lower
temperatures over a longer period can have the same effect as higher temperatures during
a shorter geologic time span. Oil generation can start at depths of between 3000m or even
slightly less if the thermal conditions are right, but it can also occur at depths of up to
10,000m in basins with very rapid recent burial such as the South Caspian.
The process of oil and gas generation from kerogen can be modeled by using chemical
kinetics to determine the dependency of the process on temperature and time. The kinetic
parameters and therefore the effect of temperature and time can vary widely depending on
the type of organic matter in the source rock. However, laboratory analyses can be
performed to measure the kinetics parameters and these can be used on geologic time
scales. The industry has now been doing this for more than 30 years, so the methodology is
well established and proven. If no direct source rock data is available, analogues can be
used, but direct source-specific measurements of kinetics data will always provide improved
accuracy. As gas is often not generated directly, but is obtained from a process of secondary
cracking of previously generated oil, secondary cracking kinetics play a critical role for
accurate petroleum property predictions.
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EAGE Student Lecture Tour: Basin and Petroleum Systems Modeling
Expulsion of the generated petroleum from source rocks is a pressure controlled process
and can be critical for exploration risk assessments. Initial oil generation does not mean that
oil is immediately expelled from the source rocks and various methods and models are used
to enable the expulsion process to be modeled more accurately. With the increasing
importance of shale resource plays, expulsion has become an even more important factor,
as the amount of oil or gas that is retained in a source rock will determine the value of the
resource. As already mentioned, conventional petroleum occurences result from petroleum
that has been expelled and can migrate within a petroleum system to form discrete
accumulations, while unconventionals such as shale resource plays are based on producing
the petroleum that is retained in the source rocks. The geological and petroleum systems
framework and the processes are the same for both conventionals and unconventionals.
Petroleum Migration Modeling
Petroleum migration modeling has been a key development topic in basin-scale modeling
for more than 20 years, starting with 2D and map-based modeling in the early 1990s and
with the first full 3D simulators then being released in the late 1990s. Petroleum migration
modeling is technically challenging due to the complexities within basin-scale geological
models which evolve through geologic time: model geometries and physical properties can
change drastically in time and space, and scaling and resolution issues need to be addressed
in order to provide meaningful results. The principle controlling physical rock property is
capillary entry pressure, which offers a resistive force to the movement of petroleum and in
effect defines a seal. Secondary controlling properties include permeabilities which control
petroleum migration rates.
Different approaches are used for petroleum migration modeling and there are no perfect
solutions: no single method will work for every task and model. The most widely used
approaches are:
− Flowpath modeling in which petroleum (oil and
gas) migration is controlled by buoyancy and
occurs along mapped surfaces. Petroleum, as it
has a lower density than water, migrates updip
along surfaces which are are defined as having
seal properties (see capillary entry pressures).
The image shows migration of oil and gas along
a regionally mapped surface.
The method is generally available as a low-cost
option and enables fast processing of highresolution
data models. It is therefore mostly used for initial assessments and screening
workflows and software tools. It works quite well in petroleum systems which have
specific characteristics such as well-defined regional migration pathways, e.g. continuous
high-permeability regional sands, but has some limitations when used in more complex
geological conditions, for example if migration is controlled by complex lithofacies
distributions. It also does not enable expulsion directions (upward vs. downward) to be
modeled, or migration rates to be determined.
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EAGE Student Lecture Tour: Basin and Petroleum Systems Modeling
− Invasion Percolation (IP) modeling is physically
similar to Flowpath modeling, as petroleum
migration is buoyancy controlled, i.e. by capillary
pressure distributions in the model. However,
instead of being a set of maps, the model is
cellular and can have very high resolutions. This
means that physically meaningful capillary
pressure distributions must be derived to
populate the cells in the model with the correct
physical properties. The image shows IP modeled
oil and gas saturations in cells, the properties of
which have been derived from seismic data using special workflows.
The method is particularly suited to data models which are, for example, based on
seismic data which has been converted to high-resolution geological information using
special inversion workflows. These can also be used in local areas, for example in a highresolution
field scale model which is included in a regional model using Local Grid
Refinement (LGR). The underlying physics are very similar to the Flowpath method
(buoyance control only), so the migration rates are not controlled by geological
parameters and migration is instantaneous within a specified time step.
− Darcy Flow modeling is often
described as ‘full physics’
modeling as migration is
controlled by the 3D distribution
of the properties of the 3D model
and by the full pressure field. For
example, Darcy flow is the only
method that can be used to
determine upward vs. downward
expulsion and the effects of
overpressuring on migration. It is
also the only method that enables
petroleum migration rates to be
determined. Depending on the geological conditions such as rapid recent generation and
migration, these can be important. They are essential for slow oil migration processes in
shale resource plays. The image shows Darcy flow (vectors) of full 3D pressure controlled
upward and downward expulsion from two source layers in the pre-salt in Brazil.
In theory, Darcy flow is an advanced and accurate technology, however in practice it has
disadvantages such as longer processing times than other methods which often limit the
resolution of the data models that can be processed in a given time.
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EAGE Student Lecture Tour: Basin and Petroleum Systems Modeling
− Hybrid methods are a combination
of petroleum simulator types, in
which different methods are used
in different areas of the data
models. Hybrid Darcy/Flowpath
simulators are widely applied and
Darcy is used in the lowerpermeability
parts of the model
where pressure control and flow
rates are important, while
Flowpath is used in higher
permeability stratigraphic units
which represent potential reservoirs. The image shows detail from a 3D model with the
vectors indicating petroleum expulsion from source rocks modeled with Darcy flow, and
the dark green Flowpath flowlines indicating petroleum migration in higher-permeability
units into petroleum accumulations. The dark blue colours show salt.
The method combines the benefits of the Darcy method (pressure controlled expulsion
and migration in low-permeability units), with the faster Flowpath method in higherpermeability
stratigraphic units which is also geologically more meaningful as oil and gas
migration is a very effective process in these units.
Special Modeling Technology
Petroleum Systems Modeling software needs many special technical capabilities to make it
applicable in specific geologic environments and for specific tasks. Due to time contraints,
these cannot be presented in detail during the lecture, but they include for example:
− Local Grid Refinement (LGR) techniques which enable specific areas, reservoirs or
stratigraphic units within a basin-scale model to be simulated with much higher
resolutions
− Crustal modeling tools which enable paleo-heatflow histories to be more accurately
assessed so that they can be used as thermal boundary conditions
− Links to structural modeling to enable petroleum generation and migration modeling to
be performed in complex geological environments such as thrustbelts
− Combinations of deterministic and statistical modeling which enable the effects of
uncertainties in the geological model to be rigorously analyzed
− Fully integrated geomechanics modeling which is directly coupled with pore pressure
simulations and enables stress/strain and fracture/failure risks to be assessed
− Special tools for unconventionals such as shale resource plays which include Langmuir
and organic porosity modeling and enable, for example, more accurate predictions of
shale oil vs. shale gas prone areas
− Gas hydrate modeling which not only models the location of the Gas Hydrate Stability
Zone (GHSZ) through geologic time, but also the process and effects of hydrate
formation
− Special geochemical modeling tools such as biodegradation, so-called Phase Kinetics for
more accurate petroleum property predictions, SARA kinetics for Saturates, Aromatics,
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EAGE Student Lecture Tour: Basin and Petroleum Systems Modeling
Resins and Asphaltenes which enable better petroleum property predictions, and
Thermochemical Sulfate Reduction (TSR) which enables H2S predictions to be made.
Summary of Principle Results
Temperature, pressure and petroleum property predictions are often described as the
three key deliverables that petroleum systems modelers are expected to provide. In
summary, information (through geologic time) which is obtained from petroleum systems
models can be summarized as follows:
1. Temperatures (thermal histories) which is a function of the lithological properties and
their distributions, as well as of boundary conditions such as basal heat flow and surface
temperatures through geological time
2. Maturity (maturation histories), which is a function of the thermal history
3. Pressure/overpressures (pressure/overpressure histories) which is a function of burial
rates, lithofacies distributions, lithological properties and their effect on fluid
movements, as well as of the geomechanical conditions during geological time
4. Hydrocarbon generation timing and location which is a function of the type of organic
matter and the maturation of the source rocks in the petroleum system
5. Hydrocarbon type (oil and gas or component mix) which is a function of the type of
source material and the maturation level
6. Hydrocarbon retention (in unconventional systems) vs. expulsion (in conventional
systems) which is a function of the hydrocarbon properties, the lithological properties of
the source rock and adjacent rock units, as well as of the ambient conditions for
pressures, etc.
7. Hydrocarbon migration which follows expulsion and is determined mainly by buoyancy
as oil and gas is lighter than water, by the pore pressure distributions in the system, by
the physical properties of the carriers and seal units in the petroleum system, as well as
by the evolving structure of the petroleum system through geologic time, taking factors
such as fault properties into account.
8. Hydrocarbon accumulation and loss which are determined by the geometry of the trap,
by the quality of the seal and the quality of the reservoir through geologic time. The
properties of the accumulated hydrocarbons will be determined by the entire charge
history, as well by the pressures and temperatures (PVT) of the accumulation at present
and throughout geologic time. Additional factors such as hydrocarbon compositions,
biodegradation, etc can then be analysed within the framework of the petroleum
systems model.
A key point is that a dynamic model which evolves through geologic time is essential in order
to assess the importance of the relative timing of all parameters and processes, for example
did the traps exist when hydrocarbons were migrating in the system. The petroleum systems
model must also be structurally correct through geologic time – if the geometric framework
is not correct, then the properties and processes that are simulated in this framework will
also not be correct.
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EAGE Student Lecture Tour: Basin and Petroleum Systems Modeling
1D vs 2D vs 3D Petroleum Systems Modeling
A frequently asked question when petroleum systems modeling software or services are
discussed is whether 1D, 2D or 3D modeling should be performed and what the main
benefits and deliverables of each approach are.
Petroleum systems modeling can be done in 1 dimension (1D) at a single point in a basin
such as a well or a ‘pseudo-well’, in 2 dimensions (2D) along geologic cross-sections, or in 3dimensions
(3D) for a complete 3-dimensional data model which can cover an area ranging
from a charge area for a single prospect to an entire basin or region, and which are mostly
constructed from 2D seismic lines. The depth/thickness of the data models is selected to
include all of the relevant elements of the petroleum system (source, carrier, reservoir), as
well as additional zones such as the basement which can be required to define the boundary
conditions more accurately and thereby obtain more accurate results.
The dimensions of the modeling tool, i.e. whether it is 1D, 2D or 3D, controls the type and
quality of the results that can be obtained:
1D Modeling can be used for items 1-6 (see previous section), even though there are some
limitations and pitfalls:
− Temperatures will be reasonably accurate as heat transfer from deeper levels of a basin
to the surface is a mostly vertical process. This can, however, be severely perturbed by
more complex geological situations and processes such as salt domes, igneous intrusions
or water flow which will have lateral effects which cannot be taken into account in a 1D
data model, or if a 2D or 3D data model is simulated with a multi-1D simulator!
− Maturation calculations will therefore have the same limitations as temperatures.
− Pressure calculations can be performed with 1D tools but only have limited value, as
there is always a lateral component in property distributions and fluid movements in
sediments
− Hydrocarbon generation timing, location, and type, as well as expulsion can also be
calculated in 1 dimension, but the same limitations apply as to the thermal and
maturation histories
Petroleum migration, accumulation and loss cannot be assessed with 1D modeling, as
petroleum migration always has a lateral component which does not exist in a 1D model.
2D Modeling can be used for items 1-6 with significant improvements compared to 1D, even
though there are still some limitations and pitfalls:
− Temperatures are more accurate than with 1D modeling as lateral effects along the
cross-section will be taken into account, including fluid movements along the section.
More complex geological situations and processes such as salt domes or igneous
intrusions can also be taken into account if they located in the section. If these geological
complications are not in the section (for example, if a salt dome or intrusion is next to a
section), 2D modeling will not be able to take them into account. This also applies if fluid
movements cross the section.
− Maturation calculations will therefore have the same improvements but also the same
limitations as temperatures.
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EAGE Student Lecture Tour: Basin and Petroleum Systems Modeling
− Pressure calculations will be much more accurate than with 1D tools and can be very
useful if the sections and their boundary conditions are located and defined properly
− Hydrocarbon generation timing, location, and type, as well as expulsion can be calculated
much more accurately in 2 dimensions, but the same limitations apply as to the thermal
and maturation histories
Petroleum migration, accumulation and loss can be assessed with 2D modeling, but only
along the cross-section. If the 2D section is positioned appropriately, it can be a useful tool
for some basic hydrocarbon risk assessments, for example for hydrocarbon column height
vs. seal quality calculations. However, it must be emphasized that hydrocarbon volumetrics
are not possible and 2D results cannot be quantitative as petroleum migration always has a
lateral and areal component. A structure on a 2D section is charged from an area, a so-called
charge area, and not just from active source units along the section.
A particularly important point for 2D modeling is their location within the regional structural
framework. This must also take the structural evolution through geologic time into account.
In order to deliver meaningful results for a 2D simulation, the cross sections must be in the
correct position relative to the controlling structures. For example, if the effect of water flow
is to be investigated, the section must be located in the direction of the water flow. Or if
petroleum migration is to be analysed, then the section must be located along a migration
path from the kitchen to the potential accumulation sites. This is not always possible as the
2D sections are mostly taken from seismic sections and their position is rarely related to the
orientation of the geological features. 2D modeling therefore has significant additional
benefits when compared to 1D, but users need to be aware of the limitations and pitfalls
and must have knowledge of the regional 3D structural development through geologic time.
3D Modeling can be used for all of the items 1-8 with no limitations or pitfalls which are
related to geometries and dimensional limitations:
− Temperatures will always have the optimum accuracy as all lateral effects will be taken
into account in a full 3D temperature simulation. Complex geological situations and
processes such as salt domes or igneous intrusions, as well as fluid movements are taken
into account.
− Maturation calculations will therefore have the same improvements
− Pressure calculations will be much more accurate than with 1D or 2D tools as all lateral
property variations can be included in the data model. And 3D Geomechanics modeling
can be used to provide significantly more accurate results in complex geological
environments.
− Hydrocarbon generation timing, location, and type, as well as expulsion can be calculated
with the highest possible accuracy with no dimensional limitations.
Petroleum migration, accumulation and loss can clearly be most accurately assessed with 3D
modeling. No functional or dimensional limitations apply and quantitative modeling is
possible. There are no concerns with the orientation or position of 3D models, only with the
resolution of the data model which may be limited by computing memory and performance.
However, Local Grid Refinements (LGR) techniques can be used to provide the highest
possible model resolution where is needed, and PetroMod processing performance as well
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EAGE Student Lecture Tour: Basin and Petroleum Systems Modeling
as the hardware have improved dramatically during the last few years to enables modeling
tasks to be performed in hours that previously took days.
In summary, a 3D data model should always be compiled if permitted by the available time,
budget and data for a project. The additional effort that is required to build the data model
is always worth it in terms of the quality of the results. Constructing a 3D data model is the
only way to obtain a comprehensive volume risk assessment, which is always the key
question in exploration with respect to charge.
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EAGE Student Lecture Tour: Basin and Petroleum Systems Modeling
Case Studies
Several case studies will be used during the lecture. Due to time constraints, only the first
two will be used in most cases. However, the additional case studies can be used to present
specific technical points or to address specific academic interests.
Brazil: Campos Basin Subsalt Exploration
This is a 3D modeling project from the Campos Basin in Brazil. It was used during the 7th
licensing round to assess risk factors related to petroleum generation in the pre-salt and
migration to post-salt targets. It is an excellent example of petroleum systems modeling
workflows now routinely applied by Petrobras in all basins in Brazil.
USA: Alaska North Slope Conventional and Unconventional Exploration
This is a 3D model which covers the entire North Slope of Alaska. It was started as a resource
assessment project in cooperation with the USGS, but has evolved to become a reference
project for both conventional and unconventional hydrocarbon resources. It is also an
excellent example for workflows which are used to create and then utilize the results from
petroleum systems modeling.
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EAGE Student Lecture Tour: Basin and Petroleum Systems Modeling
Brazil: Potiguar/Ceara Basin Deepwater Exploration
This is a 3D exploration model which is directly linked to multi-client seismic and CSEM data.
It is used to show the value of integration workflows, of basin to prospect scaling, and of
using multiple lines of evidence to assess prospect risks.
Venezuela: Santa Barbara Thrustbelt Exploration
This is a 2D study which is used to demonstrate the special workflows that are required in
structurally complex areas and especially in compressive settings. Standard petroleum
systems modeling reconstruction workflows cannot be used in these environments, and
structural reconstructions must first be performed in order to better validate
interpretations, and then to reconstruct paleo-geometries which are then used for
petroleum systems modeling.
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EAGE Student Lecture Tour: Basin and Petroleum Systems Modeling
USA: San Joaquin Basin/California
This is a 3D study which is documented in a complete series of papers by the USGS as
Professional Paper 1713 (http://pubs.usgs.gov/pp/pp1713/). It includes a unique and
detailed sequence of separate papers which describe the geological framework and
exploration history, the development of the petroleum systems model, and the resulting
petroleum resource assessment of the basin.
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EAGE Student Lecture Tour: Basin and Petroleum Systems Modeling
Appendix
Further Education and Career Opportunities
In this part of the lecture, educational opportunities will be presented such as the Basin and
Petroleum Systems Modeling Group at Stanford University
https://pangea.stanford.edu/researchgroups/bpsm/. Career opportunities in the industry
will also be presented.
References and Recommended Reading
Introductions for Students:
− Gluyas, J., and R. Swarbrick, 2003, Petroleum Geoscience (excellent standard reference)
− Bjorlykke, K., 2011, Petroleum Geoscience (excellent introduction to the topic including
basin modeling fundamentals)
− Keary, P., M. Brooks and I. Hill, 2002, An Introduction to Geophysical Exploration
(excellent introduction to geophysics for geoscience students, includes good examples)
− Killops, S.D and V.J. Killops, 2005, An Introduction to Organic Geochemistry (good
introduction for students, maybe dated, but good structure)
− Selley, R.C., 1997, Elements of Petroleum Geology (good introduction for students, easy
to read, includes description of petroleum industry)
− Fossen, H., 2010, Structural Geology (good introduction to the topic for students, easy to
understand, includes geomechanics)
− Stuewe, K., 2007, Geodynamics of the Lithosphere: An Introduction (good introduction to
the topic for students)
For Advanced Studies:
− Hantschel, T. and A. Kauerauf, 2010, Fundamentals of Basin and Petroleum Systems
Modeling (very complete reference of the theoretical aspects of the topic, the only
reference which also covers the physics)
− Jaeger, J., N.G. Cook and R. Zimmermann, 2007, Fundamentals of Rock Mechanics (the
best reference on the topic, for physicists and engineers)
− Twiss, R.J. and E.M. Moores, 2006, Structural Geology (excellent and advanced reference
on the topic)
− Krauskopf, K.B. and D.K. Bird, 1994, Introduction to Geochemistry (advanced reference
on the topic, in-depth chemistry knowledge required)
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