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 Vanbeselaere, 1995) (from Christopher, 1974)

Acquisition of 3C-3D seismic survey Shot in May, 2002 Field parameters: Source: Dynamite 0.5 kg @ 15 m Depth Group interval = 50 m N-S shot-line spacing = 325 m Receiver: 3C VectorSeis 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 km2

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 Crossline 11 Channel West East IHACM

Inline 41 Channel South North IHACM The Xline 41, crossing the well 11-25. It seems that all the events at the first 10 xlines are dipping upwards, statics?

XL81 XL41 XL11 East West

Time slices T=1150 T=1120 T=1130 T=1160 T=1170 T=1140 A “V” shape at 1170 ms. Color key: red positive, blue negative. T=1170 T=1140

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

Crossplot of P-velocity and S-velocity from 4 regional wells Vp=1.50*Vs+964 Vp/Vs=1.5 Vp/Vs=2.0 Vp/Vs=3.0 Mudrock: Vp=1.16*Vs+1360

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 Xline 11 Xline 41 Xline 81

Horizon Maps (Time Structure) PP data RushLake IHACM PS data RushLake IHACM

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

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