basin modeling in 2d complex structural...

BASIN MODELING IN 2D COMPLEX STRUCTURAL AREAS

ISSUES AND EXISTING SOLUTIONS FOR THE CREATION OF COMPLEX GEOLOGICAL SCENARII.

Romain Darnault Thomas Crabie, Renaud Divies, Jean-François Lecomte, Marie Callies

[email protected]

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Entrée

Definitions : What is a complex area?

Plat du jour

Existing workflows and their limitations

Fromage

How to improve ?

Dessert

Conclusions

Menu

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DEFINITION : WHAT IS A COMPLEX AREA IN BASIN MODELING

Entrée

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WHAT IS A COMPLEX AREA IN BASIN MODELING ??

Meshing = vertical pillars

Unstructured mesh

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WHAT IS A COMPLEX AREA IN BASIN MODELING ??

• Displacements along Faults & Sediment Deformations must be taken into account

Vertical shear backstripping must be replaced by a real structural restoration (lateral displacement)

Vertical pillars – Multi1D backstripping method Unstructured mesh – Each structural block is meshed independently of the others, allowing to take into consideration lateral displacements

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THE CLASSICAL WORKFLOWS USED IN BASIN MODELING

ANT THEIR PRACTICAL LIMITATIONS

Plat du jour

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WHAT IS THE CLASSICAL WORKFLOW IN BASIN MODELING?

1st: Building present day model from both geological and geophysical data

Use of seismic, wells data , gravimetry data, field data…

Example of the western Black sea :

Matenco et al., 2016

Ringenbach 2013

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Example of Bolivia: Differences in a set of data interpretation.

Use of modeling to test hypotheses and validate present day cross section.

Darnault et al., 2016

Driehaus et al., 2014 Darnault et al., 2016

Data Uncertainty

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Example of Papua New Guinea: Hard time for interpreters

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2nd: Making a geological scenario consistent with both geophysical and geological data/context

Backward scenario

Present Day

N-1

N-2

N-3

N-4

Initial

Forward scenario

Present Day

N-1

N-2

N-3

N-4

Initial SL

5km

0 4 km

30 40 WSW

ENE

SL

5km

0 4 km

30 40

Comparison with the ‘target’ (previous slide)

WSW ENE

SL

5km

0 4 km

30 40

Triangle zones formed above the deeper detachment

WSW ENE

SL

5km

0 4 km

30 40

Triangle zones formed above the shallow

detachment

WSW ENE

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Present Day

N-1

N-2

Backward scenario

N-3

N-4

Initial

Forward scenario

Present Day

N-1

N-2

N-3

N-4

Initial

Pros Pros

Cons

Cons

• Easy to estimate the displacements along the faults

• Total Respect of hard data (present

day section)

• Easy for erosion modeling because erosion is simply material removal

• Easy to consider the maximum burial for compaction/decompaction processes.

• Modeled Present Day can be different from hard data

• Suppose to have lots of kinematical constraints to avoid trial-errors process

• Difficult to estimate erosion amount without data to constrain it.

• Decompaction is not obvious (maximum burial?)

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Two modes of deformation used

Mechanical engine of deformation

Geometrical engine of deformation

• Based on geometrical observation of the deformation (flexural slip, oriented shear, trishear, etc.)

• Use of geometrical constraints (area preservation, thickness preservation)

• Use of the Finite Element Method (meshing = patchwork of fine elements to take into consideration the heterogeneities)

• Use of the rocks properties for the deformation (Young modulus and Poisson coefficient)

• Minimization of the deformation energy to solve the equations


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Two modes of deformation used

Mechanical engine of deformation

Geometrical engine of deformation


Pros Cons

Pros Cons

• Allow mechanical compaction/decompaction

• Allow strain / stress calculation

• Require a good knowledge of the rheology • Still hard to model the heterogeneity of rocks

(ductile vs brittle) • Not always realistic due to approximations • Calculation of an accurate deformation can be

long (compare to geometrical modes)

• Geologically representative of the deformation observed, even without a perfect knowledge of the rheology

• Simple and Fast calculation of the deformation

• Need several modes (and knowledge) to be able to restore a complex system (flexural slip, shear, trishear, etc.)

• Do not respect the mechanical laws

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3rd: Simulation in a basin modeling software

Need to mesh all geological scenario steps

Each cell must be followed from step to step

Use of the thermic simulation to calibrate erosions

Need a loop between restoration and simulation

Back and Forth

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Simulation process can bring new constraints on the restoration, especially on: - Erosion amounts - In depth geometrical structures - Testing hypothetic event (like magmatism).

The communication between the restauration tool and the simulator must be strong, handy and rapid

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From Callies et al., 2016 From Vilasi et al., 2009

Salina del Isthmo, Gulf of Mexico (Ref: CNH Atlas) Darcy HC migration (faults act as conduits with

permeable damage zone)

Albanides Repartition of the maturity (vitrinite reflectance in %)

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HOW TO IMPROVE THE WORKFLOW?

Fromage

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HOW TO IMPROVE THE WORKFLOW ?

For very complex areas, it is often required to test several hypotheses. Need of a handy tool allowing the creation of several scenarii : The kinematic tree

Objectives : - Be able to create as many scenarii as wanted during the restoration step

- Be able to replay a kinematic scenario after a minor modification

(modifying the source rocks, or reservoir thickness, erosion, etc.)

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Backward or Forward scenario ?

Present Day

N-1

N-2

N-3

N-4

Initial

Present Day

N-1

N-2

N-3

N-4

Initial

N-4

N-3

N-2

N-1

Virtual present day

Increase of the uncertainty

Divergence

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A mix between Backward and Forward scenario

Present Day

N-1

N-2

N-3

N-4

Initial

N-2’

Forward step

N-2’’

Redrawing

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How to refine a scenario : Refine a layer in the first step (Layering) ?

Present Day

N-1

N-2

N-3

N-4

Initial

Refine a layer in present day and replay automatically all the restoration

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How to refine a scenario : Intermediate Steps (Layering) ?

Present Day

N-1

N-2

N-3

N-4

Initial

N-2

N-3

Adding automatically intermediate steps between two main scenario stages.

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Finally, what kind of deformation engine should we used?

It depends what you want to do with the data you have!

Restoration software for basin modeling need to provide a large panel of deformation tools…

• Geometry driven methods

• Oriented shear, Flexural slip

• Moving least square

• Vectorial displacement field calculation from known displacement

• Minimization of area variation

• Fast calculation (real time), few information required from the user = easy to use

• Mechanic driven method

• Finite elements • Add of strain tensor calculated on the stratigraphy to take into account the heterogenities of the stratigraphy

• Add a degree of freedom (Cosserat continuum) to take into account the “layercake” effect

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Finally, what kind of deformation engine should we used?

It depends what you want to do with the data you have!

Restoration software for basin modeling need to provide a large panel of deformation tools…

• Use of physical engines (e.g. PhysX from NVidia or Sofa from INRIA) for forward modeling

• Physical driven method (forward modeling)

How to deform ductile processes ?

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… with handy and efficient tools to manipulate and deform the structural blocks!

• Automated detection and selection of sources and targets, all mouse-driven

• All deformation parameters are predefined • Contact preservation between blocks • Length or surface preservation • Stiffness of the rock (in addition to elastic parameters)

• Kinematic Scenario

• Keeps track of the operations, easy testing of hypothesis, comparison, go back and forth

Definition of deformation along fault

Instantaneous results

Eroded material drawing

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Restoration Tool

• Structural Interpretation and Validation of the present day section

• Elaboration of the kinematic scenario

of the deformation

Basin Simulator

• Need a scenario

• Need to be able to test quickly various scenarios (P/T simulations,…)

The link between Restoration and simulation:

meshing tool

The solution must be fully integrated, allowing back and forth between Restoration and simulation tools Need an efficient and handy meshing tool

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CONCLUSION

• Key exploration areas are now structurally complex. Basin modelling need to deal with this complexity in acceptable time

• Existing software allow to manage a full restoration in complex area, or to model fluid flows, Hc accumulations, maturity (etc.) but it is often tedious and practical limitations are still present

Structural “Restoration” Objectives

• Structural Interpretation and Validation

• Understanding of main deformation stages and assumptions

Basin Modeling Needs

• A consistent kinematic scenario with an appropriate time stepping

• A mesh in which simulators will be able to run

• The ability to test quickly various scenarios

The link between the step of the scenario creation and the step of simulation must be strong (should not be separated anymore)

1st: The link between the different steps of the workflow

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CONCLUSION

• As seen yesterday, a study need structural experts: basin modeler experts, gravity experts, magnetics experts…

• Solutions exist to bring expertise but… the tools have to be usable !!

The challenge consist in making the new generation basin modeling tools easily usable by peoples not especially expert of all of these domains.

2nd: Expertise issues

Some idea to reach this objective?

Use of other research domains as : - Ergonomy - Machine learning - Automatism - …

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CONCLUSION

• Use of several deformation engine (geometrical, mechanical, physical)

• Adapt or invent the deformation engines in the aim to restore or to model ductile processes (shale, salt)

3rd: Ability to manage all the structures

basin modeling in 2d complex structural...

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