Transcript Maximum Entropy Migration: Preliminary Results

JOINT IMAGING USING
PRIMARY AND MULTIPLE
FOR RVSP DATA
Jianhua Yu
University of Utah
Drill-bit Primary Autocorrelogram Migration
SP
1255
1235
1215
1.0
Time (s)
Drilling
Hole
2.0
Real
?
Ghost
3.0
?
Outline
Motivation
Joint Migration Method
Examples
Synthetic data
UPRC data
Summary
Outline
Motivation
Joint Migration Method
Examples
Synthetic data
UPRC data
Summary
RVSP While Drilling Geometry
Geophone
Source
?
RVSPWD Method
Provide Look-ahead Image Below
the Drill bit
Reduce Risk in Drilling
Problems in RVSPWD
Geophone
Source
Pilot signal?
Wavelet ?
Bit Position?
Problems with RVSPWD

Static shift errors may exist

Difficulty for separating primary
and ghost waves from deviated
or horizontal well
Solution
Autocorrelogram Migration
Why do we use autocorrelation
of seismic data rather than the
seismogram ???
Strengths of Autocorrelogram
Migration
Reduce
Static
errors
influence
No need
to know
source
wavelet
No need
to know
initial
time
No limits
to
deviated
well
What is Joint Migration
Well
Receiver
Ghost
Direct
Wave
Primary
Drill bit
What is Joint Migration
Seismic Data
Primary
migration
Ghost
migration
Final migration image
Benefits of Joint Migration
Do not need to separate
primary and ghost waves
Attenuate the interferences
in migration image
Outline
Motivation
Joint Migration Method
Examples
Synthetic data
UPRC data
Summary
Primary Autocorrelogram
Imaging Condition:
 sx  xg
p
  sx  xg
 sg
g
 xg
s 
sx
x
 sg
Primary Autocorrelogram
Imaging Condition:
  sx  xg
p
 sx  xg sg
g
 xg
s 
sx
x
 sg
Primary Autocorrelogram
Imaging Condition:
  sx  xg  sg
p
g
 xg
s 
sx
x
 sg
Ghost Autocorrelogram Imaging
Condition:





sx
xx
xg
g
  sx  x x  xg
0
0
 sg
0
x
 xx
0
s
0
0
g
 xg
x x
0
x
 sg
Ghost Autocorrelogram Imaging
Condition:
  sx  x x  xg
g
0
 sx  x x  xg  sg
0
0
x
 xx
0
s
0
0
g
 xg
x x
0
x
 sg
Ghost Autocorrelogram Imaging
Condition:
  sx  x x  xg  sg
g
0
0
x
 xx
0
s
0
g
 xg
x x
0
x
 sg
Principle of Joint Migration
Seismic data: Primary + Ghost
Primary migration
Ghost migration
Product
Final migration image
Procedure of Joint Migration

Pre-processing raw data

Autocorrelating seismic traces:
d(rg rg )
 gg  d g d g

Migrating traces using both primary
and ghost imaging conditions

Calculating weight by w= Mp*Mg
(Luo Yi, 2001)

Weighting primary image
Outline
Motivation
Joint Migration Method
Examples
Synthetic data
UPRC data
Summary
Outline
Motivation
Joint Migration Method
Examples
Synthetic data
UPRC data
Summary
Horizontal Well Model
0
0
X (m)
4
Depth (m)
V1
V2
V3
V4
V5
3
V6
Autocorrelogram
Shot Gather
200
0
Time (s)
Traces
Time (s)
0
1
4
4
1
CSG 10
Traces
200
Standard Migration with Joint Migration
(3 CSGs)
Depth (km)
0
1.6
X (km)
2.1
Source
1.6
X (km)
Source
2.5
Standard migration
Joint migration
2.1
Migration with Velocity Error 5%
Depth (km)
0
1.6
X (km)
2.1
Source
1.6
X (km)
Source
2.5
Kirchhoff
2.1
Auto. mig
Depth Migration With Static Errors
Depth (km)
0
1.6
X (km)
2.1
1.6
Source
X (km)
Source
2.5
Kirchhoff mig
Auto. mig
39 CSGs
2.1
Depth Migration With Static Errors
Depth (km)
0
1.6
X (km)
2.1
1.6
Source
X (km)
Source
2.5
Joint auto. mig
Joint Kirchhoff mig
39 CSGs
2.1
Time Migration Results (39 CSGs)
Time (s)
0
1.6
X (km)
2.1
Source
1.6
X (km)
Source
2.0
With only primary
2.1
Joint auto. migration
Why is Auto. Mig. Less Sensitive to
Velocity Error?
Standard migration:
  sx  xg
p
Auto. migration or Reduced migration
(Sheley, 1999):
  sx  xg  sg
p
Why is Auto. Mig. Less Sensitive to
Static Error?
Auto. Migration:
   sx  xg  sg
p
p 'xg   xg   g
 '   'sx  'xg  'sg
 'sx   sx   s
sgsxsxg
g sg
 'sg 
 
Outline
Motivation
Joint Migration Method
Examples
Synthetic data
UPRC data
Summary
Acquisition Survey
East (kft)
0
0
Drill bit
Well Rig
-5
Depth (kft)
0
10
4.5
Main Acquisition Parameters
Drill-bit Depth:
9188 ft
Offset Range:
1135-4740 ft
Recording Length: 20 s
Sample Interval:
2 ms
Station Number:
10
Main Processing Steps
Trace editing and static shift
Frequency panel analysis and noise elimination
Amplitude balance and energy normalization
Velocity analysis
Autocorrelograms, vertical stacking
Joint migrating autocorelograms
Autocorrelograms of CSG 96
1
10
1
10
1
10
Time (s)
0
4
8s
12 s
16 s
Joint Migration Images
1
Time (s)
0.0
3.3
Traces
50
Acquisition Survey Map
Well Rig
North (ft)
0
Drill bit
-5000
0
1500
3000
East (ft)
4500
Joint Migration ( insert) and CDP Section
SP
Drilling
1.0
Time (s)
hole
2.0
3.0
1255
1235
1215
Primary Migration ( insert) and CDP Section
SP
Drilling
1.0
Time (s)
hole
2.0
3.0
1255
1235
1215
Joint Migration ( insert) and CDP Section
SP
Drilling
1.0
Time (s)
hole
2.0
3.0
1255
1235
1215
Primary Migration ( insert) and CDP Section
SP
Drilling
1.0
Time (s)
hole
2.0
3.0
1255
1235
1215
Outline
Motivation
Joint Migration Method
Examples
Synthetic data
UPRC data
Summary
SUMMARY
No need to separate upgoing
and downgoing waves
Attenuate the noise in migration
Reduce influence of static errors
SUMMARY
No limit to horizontal well
No need the pilot signal and
wavelet history
Amplitude fidelity distortion
Acknowledgments
• I greatly appreciate Union Pacific
Resources for donating this data
• I am grateful to the sponsors of the
UTAM consortium for financial
support