Volume 7, No. 9, September 1996
Accomodation at The Lodge at Kananaskis is available for the nights of November 3 - 5. The special group rate for the rooms is $113.00 CAD per night, single or double occupancy. Gratuities and various nefarious taxes will also be added, we're told. Please make reservations as required, before October 3, by calling The Lodge at Kananaskis directly at (403) 591-6240. To qualify for the rate quoted above, identify yourself as being with The University of Calgary, Department of Geology & Geophysics - CREWES Project. See you there!
Two time-lapse three-dimensional (3-D) seismic surveys were provided by Imperial Oil from a production area at Cold Lake, Alberta, where the bitumen-saturated sands are undergoing cyclical steam stimulation. The two data sets were processed concurrently using a procedure developed to minimise differences between them above the reservoir in order that differences within the reservoir itself could be attributed to changes in reservoir conditions. Interpretation of the two processed data volumes shows increased interval traveltimes during the injection cycle while the "difference" data volume reveals variations in reflectivity within the reservoir. These responses are mapped and combined to present the spatial distribution of the interpreted heated reservoir. Inversion of the stacked data confirms that amplitude anomalies are caused by zones of low velocity due to gas during the production cycle and steam during the injection cycle.
Two experimental time-lapse multicomponent (3-C) surveys were also provided. Modifications to the converted-wave processing routine included a revised method of determining the large shear-wave static corrections, iterative velocity analysis and deconvolution after normal moveout corrections. Analysis of Vp/Vs, measured from the 3-C seismic data, showed that this ratio is lower during steaming than during production and that, in general, lowest values are seen at the injection well locations (see figure below). The average measured Vp/Vs in the cold reservoir and the lowest measured value in the heated reservoir agree well with the theoretical values. Areas of heated and cold reservoir mapped from the Vp/Vs analysis correlate well with those determined from Imperial Oil's analysis of 3-D seismic data.
Selected amplitude anomalies from the two stacked 3-D seismic data sets were analysed by investigating amplitude variations with offset. The AVO results confirm the interpretation of amplitude anomalies as due to low velocity zones. Analysis of data along a 3-C P-P line indicates a good correlation between positive AVO response and injection well locations.
AVO and Vp/Vs analyses should be considered as complementary techniques to be integrated with the analysis of the conventional seismic data. The additional information afforded by these more unusual techniques of time-lapse 3-D, 3-C and AVO analysis increases confidence in the efficacy of seismic mapping techniques to portray accurately the spatial and temporal variations within the reservoir.
CREWES is growing! We have seven new students entering the Geophysics Graduate program with CREWES this September. A warm welcome to:
Dan Cieslewicz: B.Sc. Geology, 1993, U. of Waterloo, Ontario.
Jitendra Gulati: M.Sc. Exploration Geophysics, 1996, Indian Institute of Technology, Kharagpur, India.
Michael Mazur: B.Sc. Astrophysics, 1995, U. of Calgary, Alberta.
Carlos Rodriguez: Geophysicist at Petrobras, Brazil, since 1985; M.Sc. Geophysics, 1987, PPPG, Brazil; B.Sc. Geology, 1984, Rio De Janeiro, Brazil.
Alana Schoepp: B.Sc. Geophysics, 1995, U. of Alberta, Alberta.
Todor Todorov: B.Sc. Exploration Geophysics, 1996, U. of Mining & Geology, Sofia, Bulgaria.
Yong Xu: M.Sc. Exploration Geophysics, 1996, Peking U., Peking, P.R.C.
Note from the Editor:
As some of you may have heard through the grapevine, I will be starting work with Shell Canada this October. Shell is an active Sponsor of CREWES and so I hope to continue being involved with the Project. It's been a great seven years!
The CREWES Project
Dept. of Geology & Geophysics
University of Calgary
2500 University Dr. N.W.
T2N 1N4 CANADA
Dr. Robert Stewart: 220-3265
Dr. Don Lawton: 220-5718
Dr. Gary Margrave: 220-4606
Siriporn Chaisri: 220-3083
Wai-Kin Chan: 220-8093
Dan Cieslewicz: 220-3269
Jocelyn Dufour: 220-8266
Ken Fang: 220-8093
Robert Ferguson: 220-3271
Jitendra Gulati: 220-5134
Helen Isaac: 220-8396
Glenn Larson: 220-3458
Xinxiang Li: 220-6749
Nicolas Martin: 220-3083
Michael Mazur: 220-6801
Darryl Parry: 220-3032
Carlos Rodriguez: 220-6801
Chanpen Silawongsawat: 220-3083
Zandong Sun: 220-6444
Todor Todorov: 220-6801
Dan Vetrici: 220-3269
Shaowu Wang: 220-5027
Hans Westbroek: 220-6596
Yong Xu: 220-5134