Manifestation of Fluid Saturation in Scattererd Waves – Numerical Experiments and Field Study

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25 September 2014II Russian-French Workshop

"Computational Geophysics" 1

II Russian-French Workshop "Computational Geophysics"

225 September 2014

Vladimir A. Tcheverda 1, Vadim V. Lisitsa 1,

Galina V. Reshetova 1.

Anastaiya S. Merzlikina 2, Valery V. Shilikov 2.

Vladimir A. Pozdnyakov 3.

1 – Institute of petroleum Geology and Geophysics SB RAS, Novosibirsk

2 – Rosneft Krasnoyarsk

3 – Siberian Federal University, Russia

This study is done thanks to PRACE* Access Grant # 2012071274: 32 million core-hours on supercomputer HERMIT at Stuttgart University

25 September 2014

Acknowledgements:

* Partnership for Advanced Computing in Europe

Content

1.Carbonate reservoirs. Fracture corridors.2.Scattered waves.3.Scattered waves’ simulation

Content

1.Carbonate reservoirs. Fracture corridors.2.Scattered waves.3.Scattered waves’ simulation

“It is estimated that more than 60% of the world's oil and 40% of the world's gas reserves are held in carbonate reservoirs.”

(http://www.slb.com/services/technical_challenges/carbonates.aspx)

Oil in carbonate reservoirs

Acquisitions and deep wells

Common situation for reservoirs in the carbonate environment: oil is accumulated in caverns, but permeability is determined mainly by fractures. Rock matrix is not permeable.

Cavernous/fractured reservoirs

"Computational Geophysics"

Core samples from Yurubcheno-Tohomskoe oil fieldNo cavities With cavities

FC – fracture corridors

BFC – bed controlled fracture

MBF – multibed fractures

HPF – highly persistent fractures

25 September 2014 12II Russian-French Workshop

Variety of fractures in the carbonate environment (following J.-P.Petit et al.)

Fracture corridors

Recovery of fracture corridors is of great importance in order to ensure effective oil field development.

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II Russian-French Workshop

Uncovered (outcrop) fracture corridor

Content

1.Carbonate reservoirs. Fracture corridors.2.Scattered waves.3.Scattered waves’ simulation.

Scattered waves

Regular seismic technology based on reflected waves cannot reconstruct the fine structure of a fractured reservoir:resolution of standard seismic techniques is of a few meters at best, while the typical thickness of fracture corridors does not exceed a few tens of centimeters. Fortunately, these objects generate scattered waves which can deliver important knowledge about fine interior of hydrocarbon collectors.

Scattered waves and fracture orientation

Model (thanks to Pierre Thore)

Closer look, top

Closer look, x-line

Closer look, in-line

Wavefield inside the reservoir, top view

Wavefield inside the reservoir, top view.

P-wave scattering

Wavefield inside the reservoir, top view.

S-wave scattering

Wavefield, x-line view

Wavefield, in-line view

In-line Cross-line

Azimuth distribution of scattering energy

Azimuth distribution of scattering energy and fracture orientation: Real data

Distribution of fractures in the well by FMI (Formation MicroImager) scanner

Azimuth distribution of scattered energy

Scattered waves and fluid saturation

Real life cubes

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Seismic cubes Permeability

Fluid saturation and scattered waves

Fluid saturation and scattered waves: synthetic

Fluid saturation and scattered waves: real data

Fluid saturation and scattered waves: real life prognostic geological map

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Fluid saturation and scattered waves

Core sample

Image in scattered waves

Multiple scattering

Content

1.Carbonate reservoirs. Fracture corridors.2.Scattered waves.3.Scattered waves’ simulation.

Scattered waves’ simulation

Simulation of wave propagation in realistic 3D anisotropic, viscoelastic media taking into account microstructure (fractures, cracks, caverns etc.) to

get a knowledge about scattered energy.

How are we doing this?

Time domain explicit finite-differences methods with local grid refinement in time and space.

First order system of viscoelastic wave equations

Artifacts

Artificial reflections must be around

34 1010

Estimated amplitude of scattered waves (theory of single scattering) is about 0.001

– 0.01 with respect to the incident one!!

Local grid refinement

1. Fine grid should be used only where \caverns\cracks\fractures are presented in order to avoid unrealistic demands on computer resources.

2. Different grids cause artificial reflections due to different numerical dispersion.

3. These artificial reflections must be around 10-3 - 10-4 with respect to incident wave.

4. Finite-difference scheme must be stable.

Local grid refinement

1. Grid refinement in time and space is performed by turn:

Parallel implementation via domain decomposition

Fine-grid area can be placed anywhere within the reference model regardless to the specific domain decomposition used in coarse-grid model.

Groups of PU: data exchange

Scalability

1. Optimal 3D Domain Decomposition via METIS - Serial Graph Partitioning and Fill-reducing Matrix Ordering.

2. Non-blocking send/receive procedures.3. Computations are starting from the most

interior point and are expanding towards neighboring domain

4. Send/Receive of partially sampled data

Scalability

Strong scalability (acceleration): the size of a problem is fixed, but the number of cores increased.

Ideal acceleration: N x time(N) = const, N – number of cores.

Strong scalability (acceleration)

Scalability

Weak scalability: the CPU load is fixed, but the number of cores increased.

Ideal WS: time(N) = const,

N – number of cores.

Weak scalability

Road map

1. Development of the archive with a set of realistic synthetic models (macro+mezo+micro scales).

2. Numerical simulation of multiphysics processes: isotropy+anisotropy+attenuation+fluid saturation+fluid flow induced by seismic waves (Permeability?) +……

3. Scattering imaging and inversion4. Non-linear effects of seismic waves’ propagation

Thank you for attention! Please, ask your questions!

Manifestation of Fluid Saturation in Scattererd Waves – Numerical Experiments and Field Study

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