Closure Phase Statics Correction Closure Phase Statics Correction University of Utah Jianhua Yu

Outline Objective Close Phase Statics Correction Examples Summary

Outline Objective Close Phase Statics Correction Examples Summary

STATICS CORRECTION PROBLEMS STATICS CORRECTION PROBLEMS Poor quality image caused by and source and receiver static errors Near-surface velocity model Irregular acquisition geometry False structure and misinterpretation

Objective Eliminate source and receiver time errorsEliminate source and receiver time errors First Arrival Reflection Closure phase

Outline Objective Close Phase Statics Correction Examples Summary

i+1i j+1 i-1 j j-1 Diagram of Three Pair Source and Receivers for Reflections

i+1 i j+1 i-1 j j-1 Diagram of Reflections After Applying “Mirror principle”

T i-1,1 =t (i-1,1)+  t si-1+  t r1  T i,i-1 = t (i,1) - t (i-1,1) +  t si -  t si-1 T i,1 =t (i,1)+  t si+  t r1  T i+1,i = t (i+1,2) - t (i,2) +  t si+1 -  t si  Ti-1,i+1 = t (i-1,3) - t (i+1,3) +  t si-1 -  t si+1 Closure Phase Method 1 32  t r3  t r2  t r1 i-1 ii+1  t si-1  t si  t si+1 Mirror principle t t (i,1) t t (i-1,1) Trume time

Closure Phase Method Moveout difference between adjacent traces

Closure Phase Method After NMO

The final estimation of static shifts at source position i+1 is: Closure Phase Method

Outline Objective Close Phase Statics Correction Examples Overthrust model data Saudi data Texas data Summary

Overthrust Data SP Time (s) SP

Overthrust Result SP Time (s) Common source gathers before (left) and after(right) eliminating source/receiver static errors 2 3 SP

Overthrust Result X (km) Time (s) Model without (left) and with (middle) shot/receiver static error, and the result after eliminating static errors

Outline Objective Close Phase Statics Correction Examples Overthrust model data Saudi data Texas data Summary

Acquisition Geometry 87 m R81R81R81R81 RmRmRmRm Rm-1Rm-1Rm-1Rm-1 R1R1R1R1 R 80 R2R2R2R2 Variable 30 m

Aramco Data Features: Data has strong scatter energy noiseData has strong scatter energy noise Ground rollGround roll Multiples from sand duneMultiples from sand dune First arrivals were influenced in far offsetsFirst arrivals were influenced in far offsets

Test of Static Correction Method on SAUDI Desert Data: Preliminary Results Two Raw CSGs Time (s) X (m)

LMO Data Before and After CP Static Correction LMO Data Before and After CP Static Correction Time (ms) Shot Number Time (ms) Before CP After CP

Stack Sections Before and After CP Static Correction Applied Time (s) X (m) `````````` BB AA Not any preprocessing step was applied except band-pass filtering ``````````

Zoom View of Window “A” Time (s) X (m)

Zoom View of Window “B” Time (s) X (m)

Outline Objective Close Phase Statics Correction Examples Overthrust model data Saudi data Texas data Summary

Acquisition Geometry 25 m R81R81R81R81 R 1 60 R 159 R1R1R1R1 R 80 R2R2R2R m 75 m

Time (s) Traces 1 TEXAS CSG DATA 156 Ground roll

Time (s) Trace Number 1 ZOOM VIEW OF CSG 140

Time (s) Trace Number 1 TEXAS DATA AFTER LMO 135 Time (s) No Static correction No Static correction After CP Static correction After CP Static correction

Time (s) X (m) Stacked Section With Conventional Plus-minus method

Time (s) X (m) Stacked Section With Closure Phase method

Time (s) X (m) Stacked Section With Conventional Plus-minus method

Time (s) X (m) Stacked Section With Closure Phase method

Outline Objective Close Phase Statics Correction Examples Summary

Summary The test results show : No need near-surface velocity model No need near-surface velocity model CP method can eliminate static shifts at source and receiver positions and improve the stacked image CP method can eliminate static shifts at source and receiver positions and improve the stacked image

Summary Waveform variation influences the correlation accuracy and robust. Waveform variation influences the correlation accuracy and robust. NO need to solve system of equations NO need to solve system of equations

What’s next Combination of refraction and reflection Improve the robustness of algorithm for noisy data Improve the robustness of algorithm for noisy data Long wavelength static correction ?

Acknowledgements I greatly appreciate Saudi Aramco for providing this data and permission to publishI greatly appreciate Saudi Aramco for providing this data and permission to publish I am grateful to the 2000 sponsors of the UTAM consortium for financial supportI am grateful to the 2000 sponsors of the UTAM consortium for financial support I thank all of people who give me some suggestions and help for this workI thank all of people who give me some suggestions and help for this work