Daniel R.H. O Connell, Ph.D. Geophysicist. Fugro Consultants, Inc. 25 March Diablo Canyon SSHAC SSC Working Meeting March 2014

Transcription

1 AB1632 Onshore Seismic Data Daniel R.H. O Connell, Ph.D. Geophysicist Fugro Consultants, Inc. 25 March 2014 Diablo Canyon SSHAC SSC Working Meeting March 2014

2 2011 and 2012 CCCSIP Onshore Seismic Data Collection and Processing What are the various data products that have been collected and processed? Inputs: 2D and 3D active source seismic data and gravity data Outputs: 2D and 3D tomography and seismic reflection What is the resolution of the seismic data? Varies from 1 m to 400 m depending on depth and data type Can you provide examples of data artifacts? Seismic reflection data reflect acoustic, not geologic structure Acoustic reflection data artifacts are associated with: crooked 2D acquisition geometry, signal-to-noise variations, velocity uncertainties, migration limitations (truncated-limited aperture), multiples from shallow large-velocity-contrast soil-weathering zones, shallow steep/vertical bedding dips.

3 CCCSIP Onshore: 2012 DCPP 3D Seismic Data 5-30 m group, 5-20 m source, 9 m bins, <3 km 8000 Receiver Positions, 8000 Source Points

4 CCCSIP Onshore: 2012 Terrace 3D Seismic Data Reflection: 2.4x4.8x0.6 m bins, Z < 300 m Tomography: 3x3x0.6 m cells, Z < 100 m 2.6 km

5 2011 2D+ Vibroseis Acquisition m group, m source, 9 m bins, arbitrary 2D lines along source routes 22 km

6 11 km 2011 AWD 2D Acquisition 9 m group interval, 1 m geophone interval in group, 9 m source interval

7 24 km 18 km CCCSIP Onshore Seismic+USGS Gravity Data Gravity Stations Gravity and Seismic Data

8 Joint Seismic-Gravity 3D Inversion 61x61x61 m cells everywhere, 15x15x3 m cells to -300 m, and 15x15x1.5 m cells to -100 m DCPP Elevation = 33 m Elevation = -28 m Elevation = -700 m Elevation = m Vp (km/s) km 18 km 7.0

9 Sonic-Log-Free Processing Approach 3D processing of all data ( 2D crooked profiles and irregular 3D) Joint travel-time-gravity 3D tomography for initial 3D interval velocity model and long-wavelength statics 3D tomography refraction moveout first-break residual statics 3D surface-consistent processing (amplitude, decon, statics, etc.) 3D Fast Beam Pre-stack Depth Migration (FBM) velocity updates 3D FBM/Kirchhoff PSDM 3D migration stacks 2D post-processing including time-variant filtering AGC 3D post processing including AGC 3D attributes

10 CCCSIP Onshore: 2012 Terrace 3D Seismic Data Reflection: 2.4x4.8x0.6 m bins, Z < 300 m Tomography: 3x3x0.6 m cells, Z < 100 m 2.6 km

11 High-Resolution Terrace 3D and AWD km

12 3D Marine Terrace Amplitude Slice at 9 m Elevation 1 km

13 3D Marine Terrace Semblance Slice at 9 m Elevation 1 km

14 3D Marine Terrace Normalized Amplitude Slice at 5 m Elevation 1 km

15 3D Marine Terrace Envelope Weighted Frequency Slice at 5 m Elevation 1 km

16 3D Terrace Inline Along 2D AWD Line 113 3D Inline Along AWD 113 2X VE Resolution 1-4 m 1600 ft 490 m 2D AWD 113 1:1 (No VE) Resolution 5-20 m 6000 ft 2000 m SL

17 AWD 207 Maino-Gonzales 1 Well Comparison West 2 km East

18 AWD 207 Maino-Gonzales 1 Well Comparison VE 1:1 West East Franciscan Contact Feet Below 2000 ft Datum

19 AWD 207 Maino-Gonzales 1 Well Comparison West 2 km East

20 Steep to Vertical Bedding Along 2D AWD km

21 Steep to Vertical Bedding Along 2D AWD

22 2D AWD TVFAGC 2:1 VE Steep/Vertical Bedding Washout Zones

23 2D AWD Line 150 Sycamore Canyon Shallow Multiples

24 2D AWD Line 150 Southwest Northeast Shallow soil-weathering multiples near bottom of valley 4.8 km/s 2.5 km/s 150_AWD_FBM_psdm_1_mix_depth_tvfagc

25 2D Vibroseis Line 204 Low Tertiary velocities cause shallow (< 1000 ft) aliasing High Franciscan velocities allow imaging of moderate shallow dips

26 2D Vibroseis Line 204 Southwest Northeast Strike Dip 204_beam_50k_vibeonly_poly_sl_stackagc

27 Vibe 204 3D Views: Comparing 2D Line With Arbitrary Line from 3D 2D from 3D inline migration of 2D sources+receivers Arbitrary line from 3D migration of all live receivers (pink circles) from all sources (green lines)

28 3D Perspectives of Vibroseis 204: 2D Line Arbitrary Line from 3D 5.7 km 6 km 6 km

29 What is the resolution of the seismic data? CCCSIP Onshore Seismic Reflection Imaging Resolution Bedding Fault Detection Data Type Resolution (m) Resolution (m) Depth Range (m) D Terrace DCPP 10 m Receivers DCPP 30 m Receivers D AWD D Vibroseis D Vibroseis *-12000

30 Conclusions What is the resolution of the seismic data? Varies from 1 m to 400 m depending on velocity, depth, data type, acquisition geometry, and signal-to-noise Can you provide examples of data artifacts? Seismic reflection data reflect acoustic, not geologic structure Acoustic reflection data artifacts are associated with: Crooked 2D acquisition geometry, Spatial signal-to-noise variations (traffic, scattered surface waves, etc.), Subsurface velocity uncertainties (sans sonic logs), Migration limitations (truncated-limited aperture), Multiples from shallow large-velocity contrast soil-weathering zones, Shallow steep/vertical bedding dips (Aliasing). It is important for ONSIP data interpreters, and anyone seeking to interpret these data, to: Understand the source and receiver acquisition coverages of these data volumes, Focus on the well-constrained reflection and tomographic imaging in areas with consistent source and receiver coverage.

31 Thank You