GENERAL INVERSION

Question 1

Definition of INVERSION

Answer 1

process of taking seismic data and extracting the underlying geology that produced that seismic data

Question 2

What is the traditional application of INVERSION?

Answer 2

Used on POST-STACK seismic data to extract AI (acoustic impedence volume- Pwaves— Zp)

Question 3

What is the newer application of INVERSION?

Answer 3

Now it is used on PRE-STACK seismic data to extract acoustic and shear impedence volumes (Swave — Zs)

Question 4

What kind of impedences are related to inversion ?

Answer 4

Pwave – Zp —- acoustic impedence

Swave – Zs — acoustic and shear impedence

Question 5

Why would you want to do INVERSION on Pre-Stack seismic data ?

Answer 5

You can calculate pore fluids

Question 6

What is the other purpose of doing INVERSION ?

Answer 6

ability to predict lithologic parameter (eg porosity and water saturation).

Question 7

What’s the GENERAL FORWARD MODEL ?

Answer 7

Impedence (Acoustic Shear)
to
Rc - Reflectivity
to
wavelet    w(t)
to 
Seismic s(t)

Question 8

INVERSION is the reverse of the GENERAL FORWARD MODEL

Answer 8

Seismic
to
Inverse Wavelet
to
Reflectivity
to
Impedence (Acoustic Shear)

Question 9

What’s the formula for Acoustic Impedence

Answer 9

Rho Vp

Question 10

What’s the formula for Shear Impedee

Answer 10

Rho Vs

Question 11

What happens going from Reflectivity to Seismic ?

Answer 11

S = W * R + noise
Seismic = Wavelet convolved with Reflectivity + noise

Question 12

What are the assumptions

Answer 12

no multiples
transmission loss/geometric spreading ignored
absoption if ignored
wavelet may be time varying…