Bedrock Delineation by a Seismic Reflection/Refraction Survey at TEAD Utah David Sheley and Jianhua Yu

Outline AcquisitionAcquisition Reflection ProcessingReflection Processing Refraction ProcessingRefraction Processing InterpretationInterpretation ConclusionsConclusions

Survey Location North 1 Mile Mandate: Image Bedrock Interface Bedrock Depth: 2 – 200? m

Acquisition Parameters Hz geopones Hz geopones 5 m receiver spacing5 m receiver spacing 2.5 m source spacing2.5 m source spacing Split spreadSplit spread 2630 m total line length2630 m total line length 1056 shot gathers1056 shot gathers EWG source (5 stacks)EWG source (5 stacks)

EWG Source

Recording Parameters 1 ms sample interval1 ms sample interval 1500 samples/record1500 samples/record 120 active channels120 active channels 4-Hz low cut filter4-Hz low cut filter 500-Hz high cut (Nyquist) filter500-Hz high cut (Nyquist) filter

Outline AcquisitionAcquisition Reflection ProcessingReflection Processing Refraction ProcessingRefraction Processing InterpretationInterpretation ConclusionsConclusions

Reflection Processing Flow Reformat Data CSG, CRG Editing Band-Pass Filtering Hz Hz Automatic Gain Control (AGC)

Reflection Processing Flow Reformat Data CSG, CRG Editing Band-Pass Filtering Hz Hz Automatic Gain Control (AGC) Refraction and Refraction and Surface Wave Mute

CMP 1179: Trace Editing Time (ms)

CMP 1179: SW and Refr. Mute Time (ms)

Reflection Processing Flow Reformat Data CSG, CRG Editing Band-Pass Filtering Hz Hz Automatic Gain Control (AGC) Refraction and Refraction and Surface Wave Mute Velocity Analysis NMO Correction Residual Statics

Reflection Processing Flow Reformat Data CSG, CRG Editing Band-Pass Filtering Hz Hz Automatic Gain Control (AGC) Refraction and Refraction and Surface Wave Mute Velocity Analysis NMO Correction Residual Statics BP Filtering and BP Filtering and Amplitude Scaling F-X Prediction Filtering Filtering Trace Mixing and AGC Scaling AGC Scaling Output Result

Final Reflection Section: Time Time (ms) Offset (m)

Final Reflection Section: Depth Depth (m) Offset (m)

CMP’s 599 and 600 Time (ms)

Final Reflection Section: Time Time (ms) Offset (m) CMP 600 CMP 1180

CMP’s 1179 and 1180 Time (ms)

Outline AcquisitionAcquisition Reflection ProcessingReflection Processing Refraction ProcessingRefraction Processing InterpretationInterpretation ConclusionsConclusions

117,000 First Arrival Picks Time (ms)

Inversion Parameters 117,000/127,000 picks117,000/127,000 picks 2.5 m grid size2.5 m grid size 2.5 m source spacing2.5 m source spacing 2730 x 220 m model (x,z)2730 x 220 m model (x,z) 160 x 80 max smoothing size160 x 80 max smoothing size 40 x 20 min smoothing size40 x 20 min smoothing size

Tomographic Residual Traveltime Residual (ms) Iteration 160 x x x 40

Velocity Tomogram Depth (m) Offset (m) Velocity (m/s)

Tomogram & Raypath Density Depth (m) Offset (m) Depth (m) Offset (m) Velocity (m/s) # of Rays

Outline AcquisitionAcquisition Reflection ProcessingReflection Processing Refraction ProcessingRefraction Processing InterpretationInterpretation ConclusionsConclusions

Refraction/Reflection Comparison Depth (m) Velocity (m/s) Offset (m) Depth (m) Offset (m)

Refraction/Reflection with Wells Depth (m) Velocity (m/s) Depth (m) Offset (m)

Interpretation Depth (m) Velocity (m/s) Depth (m) Offset (m)

Outline AcquisitionAcquisition Reflection ProcessingReflection Processing Refraction ProcessingRefraction Processing InterpretationInterpretation ConclusionsConclusions

Conclusions Refraction tomography provides confidence in the reflection image.Refraction tomography provides confidence in the reflection image. 40-Hz geophones did not sufficiently attenuate surface wave energy.40-Hz geophones did not sufficiently attenuate surface wave energy. Source induced noise contaminated near offset traces.Source induced noise contaminated near offset traces. The source produced adequate energy to image the bedrock contact.The source produced adequate energy to image the bedrock contact.