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

SaskatchewanSaskatchewanChuandong (Richard) XuChuandong (Richard) Xu

andand Robert R. StewartRobert R. Stewart

CREWES Sponsors Meeting, Nov. 21, CREWES Sponsors Meeting, Nov. 21, 20032003

OutlineOutline

IntroductionIntroduction Geology (channel sands)Geology (channel sands) 3C-3D seismic and VSP data3C-3D seismic and VSP data Interpretation of PP & PS sections, Interpretation of PP & PS sections,

isochrons, and Vp/Vsisochrons, and Vp/Vs Summary & AcknowledgementsSummary & Acknowledgements

IntroductionIntroduction

Ross Lake located in southwestern Saskatchewan. Ross Lake located in southwestern Saskatchewan. Target: Sandbars in Dimmock Creek Member of the Target: Sandbars in Dimmock Creek Member of the

Cantuar Formation of Mannville Group, Lower Cantuar Formation of Mannville Group, Lower Cretaceous.Cretaceous.

High porosity (>30%) and high permeability (3 Darcy). High porosity (>30%) and high permeability (3 Darcy). Heavy Oil, 13Heavy Oil, 13° API. ° API. 4 vertical wells + 1 horizontal well in this area.4 vertical wells + 1 horizontal well in this area. No gas cap, not waterflooded.No gas cap, not waterflooded.

(from Christopher, 1974)

Geology

(from Vanbeselaere, 1995)

Acquisition of 3C-3D seismic survey

Shot in May, 2002Shot in May, 2002 Field parameters:Field parameters:

Source: Source: Dynamite 0.5 kg @ 15 m DepthDynamite 0.5 kg @ 15 m Depth

Group interval = 50 mGroup interval = 50 m

N-S shot-line spacing = 325 mN-S shot-line spacing = 325 m

Receiver:Receiver: 3C VectorSeis3C VectorSeis

Group interval = 50 mGroup interval = 50 m

E-W receiver-line spacing = 180 mE-W receiver-line spacing = 180 m Record length: 5000 ms @ 2 ms sample rateRecord length: 5000 ms @ 2 ms sample rate CDP Bin size: 25m CDP Bin size: 25m × 25m with fold of 45× 25m with fold of 45 After processing, NS Inline 1-91, EW Xline 1-132, about 7.5 kmAfter processing, NS Inline 1-91, EW Xline 1-132, about 7.5 km22

25

Map

Acquisition of the walkaway VSP

Shot in June, 2003Shot in June, 2003 Zero-offset VSP: offset=53.67 mZero-offset VSP: offset=53.67 m

Source: Source: 1. Litton 315 vert-vibe1. Litton 315 vert-vibe2. IVI horiz. mini-vibe2. IVI horiz. mini-vibe

Offsets VSP: 400 m and 700 m with vert-sourceOffsets VSP: 400 m and 700 m with vert-source

Walkaway VSP: Walkaway VSP:

offsets=150, 250, 560, 1000m with offsets=150, 250, 560, 1000m with vert-sourcevert-source

Sweep: 8-180 Hz for P-souceSweep: 8-180 Hz for P-souce

5-100 Hz for S-souce5-100 Hz for S-souce Downhole geophones spacing: Downhole geophones spacing:

7.5m7.5m

200 m

Crossline 11

Channel

West East

IHACM

Interpretation of seismic PP dataInterpretation of seismic PP data

Inline 41

Channel

South North

IHACM

XL11 EastWest XL41XL81

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 dataInterpretation of PS seismic dataXL11, PS-radial XL11, PS-transverse

PS time

PP XL11 PS XL11, constant Vp/Vs=2.35

PP time

Vp=1.50*Vs+964

Vp/Vs=1.5 Vp/Vs=2.0

Vp/Vs=3.0

Mudrock: Vp=1.16*Vs+1360

Crossplot of P-velocity and S-velocity from 4 regional wells

Amplitude Spectrum

PP

PS-transverse

PS-radial

PS VSP (700m offset)

PP time, applied 5/10-50/60 bandpass filterPP data PS data, Vp/Vs=2.35 AND bulk shift UP 125ms

PS synthetic in PS time

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

Xline 11

Pick horizons on PS data

Xline 41Xline 81

RushLake

IHACM

Horizon Maps (Time Structure)

PS dataPP data

RushLake

IHACM

PP time thickness RushLake-IHACM PS time thickness RushLake-IHACM

Apparent Vp/Vs map between RushLake and IHACM

1*2

/

Tpp

TpsVsVp

SummarySummary

PP time thickness indicates channels & sand bar PP time thickness indicates channels & sand bar shape shape

PS suggests sandy areas, shale cuts, PS suggests sandy areas, shale cuts, & & additional additional targetstargets

Offset VSP helps correlations significantlyOffset VSP helps correlations significantly

Zero-offset VSP gives interval Vp/Vs (1.6 to 3.3)Zero-offset VSP gives interval Vp/Vs (1.6 to 3.3)

Synthetic seismograms increase confidenceSynthetic seismograms increase confidence

AcknowledgementsAcknowledgements

Husky Energy Inc.Husky Energy Inc. Larry Mewhort, Kenneth Hedlin and Larry Mewhort, Kenneth Hedlin and

Angela Ricci from HuskyAngela Ricci from Husky Larissa Bezouchko from SchlumbergerLarissa Bezouchko from Schlumberger Hampson-Russell for donating ProMCHampson-Russell for donating ProMC Sponsors of CREWESSponsors of CREWES