Joint Migration of Primary and Multiple Reflections in RVSP Data Jianhua Yu, Gerard T. Schuster University of Utah
Time (s) SP Drill-bit Primary Autocorrelogram Migration Drill Hole Real ? Ghost ?
Outline Motivation Joint Migration Method Examples Synthetic data UPRC data Summary
Outline Motivation Joint Migration Method Examples Synthetic data UPRC data Summary
Source Geophone ? RVSP While Drilling Provide Look-ahead Image Below the Drill Bit Reduce Uncertainty in Drilling
Source Geophone Bit Position? Problems in RVSPWD Pilot signal? Wavelet ?
Problems with Drill-bit and RVSP Data No source wavelet No source initiation time Not easy to get pilot signal in deviated well Not easy to get pilot signal in deviated well and horizontal well
Static shift errors may exist Difficulty for separating primary and ghost waves from deviated or horizontal well Problems with Drill-bit and RVSP Data
Solution Autocorrelogram Migration Why do we use autocorrelation of seismic data rather than the seismogram ???
Strengths of Autocorrelogram Migration No need to know initial time No limits to deviated well Be able to reduce static errors No need to know source wavelet
Well Drill bit Receiver Primary Direct Wave Ghost What is Joint Migration
Final migration image Ghost migration Primary migration Seismic Data
Joint Migration using Primary and Ghost Reflections Do not need to separate primary and ghost waves Attenuate the interferences in migration image What is Benefit from Joint Migration
Outline Motivation Joint Migration Method Examples Synthetic data UPRC data Summary
Primary Autocorrelogram Imaging Condition: x g s Autocorrelating Trace
Primary Autocorrelogram Imaging Condition: x g s
x g s
x g s Ghost Autocorrelogram Imaging Condition Ghost Autocorrelogram Imaging Condition: Autocorrelating Trace
x g s Ghost Autocorrelogram Imaging Condition Ghost Autocorrelogram Imaging Condition:
x g s
Principle of Joint Migration Seismic data: Primary + Ghost Ghost migrationPrimary migration Final migration image Product
Procedure of Joint Migration Pre-processing raw data Autocorrelating seismic traces: Migrating traces using both primary Mp and ghost imaging conditions Migrating traces using both primary Mp and ghost imaging conditions Mg Weighting primary image Calculating weight by w= Mp*Mg
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 Depth (m) 3 40 X (m) V1 V2 V4 V3 V5 V6
Shot Gather Time (s) CSG Time (s) Traces Autocorrelogram
Depth (km) X (km) X (km) Standard migration Joint migration Standard Migration with Joint Migration (3 CSGs) Source
Time (s) X (km) X (km) With only primaryJoint auto. migration Time Migration Results (39 CSGs) Source X (km)
Depth (km) X (km) X (km) Kirchhoff migAuto. mig Depth Migration With Static Errors Source 3 CSGs
Depth (km) X (km) X (km) Joint Kirchhoff mig Joint auto. mig Depth Migration With Static Errors Source 39 CSGs
Outline Motivation Joint Migration Method Examples Synthetic data UPRC data Summary
Acquisition Survey East (kft) North (kft) Well Rig 3C Receivers Drill bit 10 Depth (kft) 0
Recording Length: 20 s Sample Interval: 2 ms East (kft) North (kft) Well Rig 10 Depth (kft) ft Offset= ft Main Acquisition Parameters
Main Processing Steps Trace editing and static shift Trace editing and static shift Frequency panel analysis and noise elimination Frequency panel analysis and noise elimination Velocity analysis Velocity analysis Amplitude balance and energy normalization Autocorrelograms, vertical stacking utocorelograms Joint migrating autocorelograms
Autocorrelograms of CSG Time (s) s 12 s16 s
Time (s) 50 Joint Migration Images Traces
Acquisition Survey Map Well Rig 3C Receivers Drill bit East (ft) North (ft) C Line AC4
Time (s) SP Drill hole Joint Migration ( insert) and CDP Section
Time (s) SP Primary Migration ( insert) and CDP Section Drill hole
Time (s) SP Drilling hole Joint Migration ( insert) and CDP Section Joint
Time (s) SP Primary Migration ( insert) and CDP Section Drilling hole Primary
Outline Motivation Joint Migration Method Examples Synthetic data UPRC data Summary
SUMMARY Need separating primary and multiple? NO Work for deviated or horizontal well ? YES Reduce the influence of static errors ? YES Need pilot signal ? NO Need source wavelet and initial time ? NO Suppress coherent noise ? YES Amplitude fidelity ? NO Virtual Multiple ? YES
Acknowledgments I greatly appreciate Union Pacific Resources Corporation for providing this dataI greatly appreciate Union Pacific Resources Corporation for providing this data I thank the sponsors of the UTAM consortium for financial supportI thank the sponsors of the UTAM consortium for financial support