Autocorrelogram Migration of Drill-Bit Data Jianhua Yu, Lew Katz, Fred Followill, and Gerard T. Schuster

Outline Motivation and Objective Autocorrelogram Migration Examples Synthetic Data UPRC data Summary

IVSPWD Objective Provide Look-ahead Image Below Drill Bit Reduce Uncertainty in Drilling Reduce Uncertainty in Drilling ?

Problems No Source Wavelet No Source Wavelet No Source Initiation Time No Source Initiation Time Not Easy to Get Pilot Signal in Not Easy to Get Pilot Signal in Deviated Well Deviated Well

Autocorrelogram Migration No need to know source wavelet No limits to deviated well Solution No need to know initial time

Outline. Motivation and Objective. Autocorrelogram Migration. Examples. Summary Outline. Motivation and Objective. Autocorrelogram Migration. Examples. Summary

Well Drill bit Receiver Primary Primary, Ghost and Direct Waves Direct Wave Ghost

Primary Autocorrelogram Imaging Condition: x g s Autocorrelate Trace Trace DR

Primary Autocorrelogram Imaging Condition: x s g D*DD*R }

x g s BONUS: Mitigates src/rec statics!

x g s Ghost Autocorrelogram Imaging Condition Ghost Autocorrelogram Imaging Condition: Ghost Autocorrelate Trace Trace DG

x g s Ghost Autocorrelogram Imaging Condition Ghost Autocorrelogram Imaging Condition: D*DD*G }

x g s

Autocorrelogram Migration Migrated Image Autocorrelation Function Imaging Cond.

Auto. Migration Procedure Auto. Migration Procedure Filter data Pre-process raw data Autocorrelate seismic traces: Autocorrelogram migration with primary & ghost imaging conditions

Outline. Motivation and Objective. Autocorrelogram Migration. Examples. Summary Outline. Motivation and Objective. Autocorrelogram Migration. Examples. Summary

Geological Model 0 Depth (m) 3 40 X (m) V1 V2 V4 V3 V5 V6

Velocity Model Depth(km) X(km) X(km) Interval VelocityRMS Velocity

Shot Gather Time (s) CSG Time (s) Traces Autocorrelogram

Primary Autocorrelogram Depth Migration Depth (km) X (km) With primary+ghost X (km) Without ghost

X (km) Without ghost Ghost Autocorrelogram Depth Migration Depth (km) X (km) With primary+ghost

Acquisition Survey East (kft) North (kft) Well Rig 3C Receivers Drill bit 10 Depth (kft) 0

Main Acquisition Parameters Drill-bit Depth: 9188 ft Offset Range: ft Recording Length: 20 s Sample Interval: 2 ms Station Number: 10

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 Calculating cross- and autocorrelograms, vertical stacking Calculating cross- and autocorrelograms, vertical stacking Autocorelogram migration Cross- and Autocorelogram migration

1 Trace # Time (s) 5-40 Hz 1 Trace # 10 Raw CGR 96 Proc. CGR 96

Autocorrelogram of CSG Time (s) s 12 s16 s

Time (s) 5000 Autocorrlogram Migration Images X(ft) X(ft) No reflections Primary Image Ghost Image Correlation Window = 8 s

Acquisition Survey Map Well Rig 3C Receivers Drill bit East (ft) North (ft) C Line AC4

Time (s) SP Drill hole Primary Autocorrelogram Image ( Corr. window=8 s )

Time (s) SP Ghost Autocorrelogram Image( Corr. window=8 s) Drill hole

SUMMARY Works for deviated wells Works for deviated wells Auto migration images show rough correlation to surface-CDP section Autocorrelation Migration: Mitigates src/rec static Compresses wavelet No need to know wavelet or start time Beware of virtual multiples! Beware of virtual multiples!

Acknowledgements We appreciate DOE’s Financial supportWe appreciate DOE’s Financial support We are grateful to Union Pacific Resources Corp. for donating this dataWe are grateful to Union Pacific Resources Corp. for donating this data I thank the sponsors of the UTAM consortium for their financial supportI thank the sponsors of the UTAM consortium for their financial support

SUMMARY Difficulty of separating upgoing and downgoing wave can cause artifacts in migration image

What is Next Improve the method for real- time purpose Reduced the virtual multiple and other wave influence Developing 3D autocorrelogram method

X (km) Without ghost Time (s) X (km) With primary+ghost Primary Autocorrelogram Time Migration

X (km) Without primary Time (s) X (km) With ghost+primary Ghost Autocorrelogram Time Migration

Outline. Objective.. Examples. Summary Outline. Objective. Autocorrelogram Migration. Examples. Summary 

Processed CSG 96 Part of CRG Time (s) Time (s) 5-40 Hz

Drill-bit Data of CSG # Time (s) Trace Number

Frequency Panel Analysis Time (s) Time (s) < 5 Hz 5-15 Hz

Frequency Panel Analysis Time (s) Time (s) Hz Hz