Interpreting a 3C-3D seismic survey, Ross Lake, Saskatchewan

Chuandong (Richard) Xu and Robert R. Stewart CREWES Sponsors Meeting, Nov. 21, 2003

Outline

 Introduction  Geology (channel sands)  3C-3D seismic and VSP data  Interpretation of PP & PS sections, isochrons, and Vp/Vs  Summary & Acknowledgements

Introduction

      Ross Lake located in southwestern Saskatchewan. Target: Sandbars in Dimmock Creek Member of the Cantuar Formation of Mannville Group, Lower Cretaceous.

High porosity (>30%) and high permeability (3 Darcy). Heavy Oil, 13 ° API. 4 vertical wells + 1 horizontal well in this area.

No gas cap, not waterflooded.

Geology (from Christopher, 1974) (from Vanbeselaere, 1995)

Acquisition of 3C-3D seismic survey

     Shot in May, 2002 Field parameters: Source: Dynamite 0.5 kg @ 15 m Depth Receiver: Group interval = 50 m N-S shot-line spacing = 325 m 3C VectorSeis Group interval = 50 m E-W receiver-line spacing = 180 m Record length: 5000 ms @ 2 ms sample rate CDP Bin size: 25m × 25m with fold of 45 After processing, NS Inline 1-91, EW Xline 1-132, about 7.5 km 2

Map

25

Acquisition of the walkaway VSP

   Shot in June, 2003 Zero-offset VSP: offset=53.67 m Source: 1. Litton 315 vert-vibe 2. IVI horiz. mini-vibe Offsets VSP: 400 m and 700 m with vert-source

200 m

   Walkaway VSP: offsets=150, 250, 560, 1000m with vert-source Sweep: 8-180 Hz for P-souce 5-100 Hz for S-souce Downhole geophones spacing: 7.5m

Interpretation of seismic PP data West Crossline 11 East Channel IHACM

South Inline 41

North

IHACM Channel

West East

Time slices T=1120 T=1130 T=1140 T=1150 T=1160 T=1170

Horizon maps (time structure) Rush Lake IHACM

Time thickness between RushLake and IHACM

Interpretation of PS seismic data XL11, PS-radial XL11, PS-transverse PS time

PP time PP XL11 PS XL11, constant Vp/Vs=2.35

Crossplot of P-velocity and S-velocity from 4 regional wells Vp=1.50*Vs+964 Mudrock: Vp=1.16*Vs+1360 Vp/Vs=1.5

Vp/Vs=2.0

Vp/Vs=3.0

Amplitude Spectrum PP PS-radial PS-transverse

PP time, applied 5/10-50/60 bandpass filter PP data PS data, Vp/Vs=2.35 AND bulk shift UP 125ms PS VSP (700m offset)

PS synthetic in PS time

PP synthetic (PP time) PS synthetic (PS time)

Pick horizons on PS data

Horizon Maps (Time Structure) PP data Rush Lake Rush Lake PS data IHACM IHACM

PP time thickness RushLake-IHACM PS time thickness RushLake-IHACM Apparent Vp/Vs map between RushLake and IHACM

Vp

/

Vs

 2 * 

Tps



Tpp

 1

Summary

 PP time thickness indicates channels & sand bar shape  PS suggests sandy areas, shale cuts,

&

additional targets  Offset VSP helps correlations significantly  Zero-offset VSP gives interval Vp/Vs (1.6 to 3.3)  Synthetic seismograms increase confidence

Acknowledgements

 Husky Energy Inc.

 Larry Mewhort, Kenneth Hedlin and Angela Ricci from Husky  Larissa Bezouchko from Schlumberger  Hampson-Russell for donating ProMC  Sponsors of CREWES