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Physical Modeling: Time Lapse, 3D, and VSP Robert W. Wiley Allied Geophysical Laboratories University of Houston. Outline. Properties of Physical Modeling Fracture Model Time-Lapse Model 3D VSP Model Hardware Future Directions Conclusions. Properties that scale well. - PowerPoint PPT Presentation
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Physical Modeling: Time Lapse, 3D, and VSP Robert W. Wiley Allied Geophysical Laboratories University of Houston
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Page 1: Outline

Physical Modeling: Time Lapse, 3D, and VSP

Robert W. WileyAllied Geophysical Laboratories

University of Houston

Page 2: Outline

Outline

• Properties of Physical Modeling

• Fracture Model

• Time-Lapse Model

• 3D VSP Model

• Hardware

• Future Directions

• Conclusions

Page 3: Outline

Properties that scale well

• Distance (typically we use 1km = 10 cm)• Time (typically we use 4 ms = 0.4 s)• Frequency (typically we use 30 Hz = 300 kHz)• P and S velocity

– For acoustic propagation we scale vp by 0.5– For elastic propagation we do not rescale

• Viscosity– Gas by air– Water by water– Oil by glycerol

Page 4: Outline

Properties that do not scale well• Source and receiver size• Pore size (other physics takes place for extremely small pores)• Frequency dependent attenuation mechanisms (which we don’t

yet understand anyway!)• Soft sediments and weathering zones

Other limitations• A model 1 m by 1 m by 0.5 m (corresponding to 10 km x 10

km by 5 km) weighs more than one metric ton!• Models take months to build • We needed bigger, stronger, and more patient graduate

students!

Page 5: Outline

Fracture Model

Page 6: Outline

Fracture ConstructionFracture Construction

1.1 cm

Glass slides

35.5 cm

Glass blocks

Resin

x

Fracture model under construction showing glass slides in situ

y

Page 7: Outline

HTI model

y

x

63.5 cm63.5 cm

50.8 cm50.8 cm

Fracture zoneFracture zone

Page 8: Outline

2.5

3

2

1071 CDP 1360

Line 2151

Page 9: Outline

+ + -

2.2

2.4

2.6

1071 1360

Tim

e (s

)

CDPLine 2140 500 m Offset

Page 10: Outline

Trace Number

200

1

1 200100 300

Line

Damp for 750 m offset – time slice 2430 ms – Perp.

Page 11: Outline

Positive Amplitude

Most Positive Curvature Most Negative Curvature

Principle Comp Filter

Page 12: Outline

Time-Lapse Model

Page 13: Outline

The model as constructed

(Wardana, 2001)

Page 14: Outline

Time lapse modeling

(Wardana, 2001)

wet

half wet

dry

near mid far

Amplitude

Page 15: Outline

Time lapse modeling

(Wardana, 2001)

wet

half wet

dry

near mid far

Coherence

Page 16: Outline

3D VSP Model

Page 17: Outline

Physical model

6 layer alternate blue and black & a salt body ρblue= 2.4 g/cc ρblack = 1.34 g/cc Vblack= 2586.9 m/sVblue =3264.3 m/s

Page 18: Outline

Preprocessing (First break pick)

Page 19: Outline

Hardware

Page 20: Outline

3 C Transducers Shear Transducers

Pin TransducersSpherical Transducers

TRANSDUCERS

Page 21: Outline

Old System (Backup System)

Page 22: Outline

NI 2 Source 4 Receiver System

Dry Tank

Page 23: Outline

NI 8 Source 16 Receiver System

Wet Tank

Page 24: Outline

Initial Configuration

Data Configuration

Page 25: Outline

NI System Control- LabView Based

Main Window

Position Control Window

Page 26: Outline

Future Directions

• Bring the two new systems on line

• Develop a 16 receiver system

• Develop a multiple source system

• Collect porous model data

• Test additional transducers

• Investigate other materials

Page 27: Outline

Conclusions

• We are able to build reasonably complex physical models

• Results are similar to seismic data

• This is an excellent approach to acquiring controlled data for testing algorithms

• Physical modeling is cost effective compared to field experiments

Page 28: Outline

Thank You

Page 29: Outline

CurvatureCurvature2.4

2.6

CDP

Line 2140 500 m Offset

1150 1202

Page 30: Outline

Pinducer

Page 31: Outline

Physical Limitations

• Inaccurate construction of actual model

• Limited selection of velocity and density parameters

Page 32: Outline

Some Limitations

• Limited bandwidth with strong resonance at one frequency

• Limited to materials with specific elastic parameters

• Difficult to build lateral velocity variations

• Labor intensive

• Cannot model all real earth materials/layers

Page 33: Outline

Source and Receiver Issues

• Inaccurate location of source and receiver with respect to the model

• Source and receiver resonate at one frequency

• Source and receiver dimensions are large

• Source and receiver have pronounced radiation patterns

Page 34: Outline

+ + -

2.2

2.4

2.6

1071 1360

Tim

e (s

)

CDPLine 2140 500 m Offset

Page 35: Outline

Properties that do not scale well• Source and receiver size• Pore size (other physics takes place for extremely small pores)• Frequency dependent attenuation mechanisms (which we don’t

yet understand anyway!)• Soft sediments and weathering zones

Other limitations• A model 1 m by 1 m by 0.5 m (corresponding to 10 km x 10

km by 5 km) weighs more than one metric ton!• Models take months to build • We needed bigger, stronger, and more patient graduate

students!

Page 36: Outline

Why Run Models

• To test interpretation – Salt dome, coal seam

• To test algorithm – Migration, Multiple removal

• To test interpretation tools – fracture identification, fluid content

• To test theory – Lamb’s problem, Kirchhoff diffraction, anisotropy

Page 37: Outline

Why Physical Modeling

• No simplifying mathematical assumptions

• No approximations to mathematical functions

• No round-off errors

• No a priori mathematical understanding required

Page 38: Outline

Limitations

• Limited selection of velocity and density parameters

• Difficult to build lateral velocity variations

• Labor intensive

• Inaccurate construction of actual model

• Limited to frequency response of transducers

• Source and receiver dimensions

Page 39: Outline

Benefits of Physical Modeling

• Experimental repeatability and controlled conditions

• Very cost-effective compared to field work

• Physics of elastic energy propagation through physical models is same as real world

• Arbitrary earthlike conditions closer to real earth data than numerical modeling

Page 40: Outline

Spherical Transducer

Page 41: Outline

3C Transducer

Page 42: Outline

www.valpeyfisher-ud.com

Shear Transducer Design

Page 43: Outline

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