P-wave and S-wave near-surface characterization in NEBC. Liliana Zuleta and Don C. Lawton 1 st December, 2011

Transcription

1 P-wave and S-wave near-surface characterization in NEBC Liliana Zuleta and Don C. Lawton 1 st December, 2011

2 Outline Objective heory and procedure Velocity and depth analysis SH data analysis / P-wave data analysis Receiver static corrections Vp/Vs analysis Field data & PP - PS registration Conclusions

3 Objectives Obtain precise P-wave and S-wave depth-velocity models for the near-surface. Compare Vp/Vs results with well log data. Derive S-wave statics as these are known to be much greater than P-wave statics and are difficult to obtain. Ultimatelyt l apply results of this work to the processing of a 3D/3C seismic survey that will be acquired in the same area, and to provide constraints on registration of PP and PS volumes.

4 Procedure wo datasets: Vibrator sources in V and SH mode. Multi-component t receivers. Rotate the horizontal component data, pick first break arrivals, apply the plus-minus analysis method and determine near-surface velocity and depth model. Calculate static corrections to datum for P and S data. Register PP and PS data for shallow horizons

5 Data Rotation Source-Receiver line θ MN or H 1 R θ ME or H 2 R = = H 2 * cosθ + H1 *sinθ H 1 *cos θ H *sin sinθθ * 2 Shear wave data processing requires the rotation of the data acquired. he radial component (R) contains predominantly SV and P-wave p ( ) p y modes, while the transverse () data are predominantly SH.

6 Field data and rotations Before Rotation After Rotation 500 ime (ms) SH-H1 SH-ransverse i ime (ms) SH-H2H2 SH-Radial Maximum offset = 1500 m

7 Plus-minus analysis Plus-Minus ime analysis window D + = AD + HD AH raveltim me HA AD HD AH h 2-layer case 1 = + D * V 2 cos θ layer case Depth V 1 V 2 X f X r A D H B θ 12 h 1 C E F G h Where θ + 2 = D ij = sin 1 ( V 2 * h1 * cos θ13 V2 * V 1 2 cos θ i / V j ) 23

8 Velocity analysis ΔX A D D H B C C F F G D D ' D = = = AD AD ' D ' HD HD 2 * ΔX V 2 ' AH AH Minus im me (ms) SP V 2 = 2/slope Distance (m)

9 Data & first-break picks Vertical component ime (ms) ime (m ms) ransverse component

10 First-break travel-time analysis P data SH data ime (ms) ime (ms ) ime (ms) ime (ms) V 2 V 2 V 1 V X rec V 3 Receiver location V 2 V 2 V V X rec Receiver location

11 P-wave velocity & depth profile Velo ocity (m/s) Station V 1 V Channel Z (m) V 1 ~ 1950 m/s V 2 ~ 2800 m/s Station

12 SH-wave data - velocity analysis Manual Ve elocity (m/s) Station V 2 V 1 V 3 Automatic Ve elocity (m/s) Station V 2 V 3 V 3 ransition zone V 1

13 SH-wave velocity & depth profile Manual 600 Z (m) V 2 ~ 650 m/s m/s V 1 ~ 350 m/s to 420 m/s V 3 = 1400 m/s Automatic Station 600 Channel Z (m) V 2 ~ 500 m/s m/s V 3 = 1400 m/s V 1 ~ 350 m/s to 420 m/s V 3 = 1100 m/s Station

14 Receiver static corrections Stations ime (ms) P-wave statics Shear statics P wave data Datum= 600 m V r = 2800 m/s SH wave data Datum = 600 m V r = 1400 m/s

15 Vp/Vs analysis Depth 0 Vp/Vs from nearby wel Vp/Vs obtained from the plus-minus analysis Z (m) 300 Z (m) Station Vp/Vs Vp/Vs=

16 PP data channel Banff Exshaw Jean Marie Base Otter Park

17 PS data channel Banff Exshaw Jean Marie Base Otter Park

18 SH data Banff Exshaw??? Jean Marie??? Base? Otter Park

19 Vp/Vs after event registration BH Vp/Vs Banff Exshaw Jean Marie Banff Exshaw Jean Marie Base Otter Park 2.0 Base OP 2.0 Vp/Vs

20 PS data in PP time Banff Exshaw Jean Marie Base Otter Park

21 PS data vs PP data Banff Exshaw Jean Marie Base Otter Park

22 Conclusions Different models were obtained from P-wave data and SH data due to more sensitivity of the shear data. For the P-wave, 1950 m/s and 2800 m/s were found for the first and second layer, respectively. For the SH-wave date, m/s, m/s and 1400 m/s for first, second and third layers, respectively he static correction times for SH-wave data are much greater than the static corrections times for P-wave data, as is expected. SH-wave statics range was -150 to -250 ms and P-wave statics varies from -15 ms to 15 ms. Well log information is very important in order to validate seismic reflectors on the data and to confirm PP and PS registration through hcomparison of Vp/VS.

23 Acknowledgements We thank all CREWES sponsors for their support, the faculty staff and computer technicians in the CREWES project for all their help. We acknowledge Nexen Inc. for allowing us to show the results of this project. Jennifer Leslie-Panek and Eric Von Lunen. We thank Sensor Geophysical for providing the results of their processing.