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Rock Physics


Gas

Down dip wet sand

GasGas

Where is the Gas?

Pre-stack Time Migrated Stack


Gas

Down dip wet sand

GasGas

The stack is a function of:

Lithology

Porosity

Fluids


Where is the Gas?


Petrophysics, Logs

Nphi


Nphi

This log is a function of:

Lithology

Porosity

Fluids

Petrophysics, Logs


Nphi Rhob

Petrophysics, Logs

Nphi


Nphi Rhob Nphi/Rhob

Petrophysics, Logs

Nphi


Nphi Rhob Nphi/Rhob Lith/Phi/Fluids

Petrophysics, Logs

Nphi


Nphi Rhob Nphi/Rhob Lith/Phi/Fluids GR

Petrophysics, Logs

Nphi


Nphi Rhob

Petrophysics, Logs

Nphi


Nphi Rhob

Lithology/Fluid

Petrophysics, Logs

Nphi


Nphi Rhob

Porosity

Petrophysics, Logs

Nphi


Nphi Rhob Lith/Phi/FluidsLithology/Fluids

Porosity

Petrophysics, Logs


Gas

Down dip wet sand

GasGas

Where is the Gas?



Amplitude Variations

with Offset,

AVO


RecordingSystem

Seismic Sources

t2

t3

GeophoneArray

t1

Location

of gather

Offset

CMP Gather

t2

t3

t1

The PSTM CDP Gather

In the PSTM CDP gather, at any given time, each offset samples the

same subsurface point but does so at different angles.


Am

pli

tud

e

sin2θθθθ

P (intercept)

Offset

Seismic Gather

tG (slope)

AVO Gradient Analysis


Am

pli

tud

e

sin2θθθθ

AVO Analysis

Full Stack

P (Y Intercept)

G (Slope)

Normal Incidence Section

AVO Gradient Section


Normal Incidence (P)

Seismic Petrophysics

Where are the sands?

Gas?

Porosity?

AVO Gradient (G)


0,0

G

P P

Stack

G

Stack

Crossplot of P and G

What does this crossplot mean

In terms of:

Lithology?

Porosity?

Fluids?


LithSeis®

Modeling Methodology


Conventional Seismic Modeling



GR RT DT Rhob Nphi

Lith/

Phi/

Fluids

Inversion


GR RT DT Rhob Nphi GR RT DT Rhob Nphi

Lith/

Phi/

Fluids

Inversion Forward Modeling



GR RT DT Rhob Nphi GR RT DT Rhob Nphi Seismic

Lith/

Phi/

Fluids

Inversion Forward Modeling



Lith/Phi/Fluids Seismic Model / Stack


Logs

Forward Model

Inversion


CDP 1


CDP 11


CDP 22


CDP 33


CDP 44


Rock Modeling Summary

P GGathers


1000 Models


From Shale to a 6% Porosity Sand

Wet, Gas

6%



Wet, Gas

10%



Wet, Gas

14%



Wet, Gas

18%



Wet, Gas

22%


26%


Wet, Gas



Wet, Gas

30%



Wet, Gas

34%



Wet, Gas

38%



Wet, Gas

42%



Wet, Gas

46%


Laminated Sands



Wet, Gas

30%


From Shale to a 30% Porosity,Laminated Sand

Wet, Gas

30%


Thickness


Sand with Porosity from 0 to 46%

4ms Thick

Distance

Thickness

4ms



8ms Thick

Distance

Thickness

8ms



12ms Thick

Distance

Thickness

12ms



16ms Thick

Distance

Thickness

16ms



20ms Thick

Distance

Thickness

20ms



All Thicknesses

Distance

Thickness


Results of:

1000’s Models

100’s data Sets


Rocks vs. Distance & Direction

Function of?

Lithology

Fluids

Thickness

Elliptical Distance Direction

Function of?

Porosity

Blocky or Laminated

Infers Depositional Facies


How does this fit with

reality?


AVO Type Tendencies


Seismic Petrophysical WorkflowP Section

G Section

Lithology Section

AVO Types Section

P vs. G


Gas

Down dip wet sand

GasGas

Where is the Gas?



Gas

Down dip wet sand

GasGas

Where is the Gas?

The stack is a function of:

Lithology

Porosity

Fluids



GasGas

Gas

GasGas

Gas

Seismic Lithology/AVO Response

4

Lithology Color Bar

50

15

0

-15

-50

G

P


Examples

Depositional Facies


Lithology/Fluid and AVO Types

Lithology AVO Type

4

Lithology Color Bar

50

15

0

-15

-50

G

P

G

12

3

4

5

-5

-3

-2

-1

AVO Type Color Bar

P

-4 5

4

3

2

1

-1

-2

-3

-4

-5


Lithology/Fluid Response, Surface

4

Lithology Color Bar

50

15

0

-15

-50

G

P


G

12

3

4

5

-5

-3

-2

-1

AVO Type Color Bar

P

-4 5

4

3

2

1

-1

-2

-3

-4

-5

AVO Type Response, Surface


LithSeis Data, Section Views

Lithology AVO Type

4

Lithology Color Bar

50

15

0

-15

-50

G

P

G

12

3

4

5

-5

-3

-2

-1

AVO Type Color Bar

P

-4 5

4

3

2

1

-1

-2

-3

-4

-5


4

Lithology Color Bar

50

15

0

-15

-50

G

P

Lithology/Fluid Response, Surface


AVO Type Response, Surface


Conclusion

Think in terms of

Lithology, Porosity

and fluids

not

wiggles and

impedances and

instantaneous

attributes.

rock physics - eseise-seis.com/wp-content/uploads/2015/11/rock-physics.pdftitle: microsoft...

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