By comparing lithologic description with core analysis and sonic log transittimes, it is possible to break the Boundary member of the Triassic Charlieformation into two major rock types. These rock types can be correlated betweenwells by their characteristic signature on the sonic logs and can thus betraced areally.
When the depths of these marker beds are fed into an electronic computer along with digitized sonic log data it is possible to compute many of the reservoir parameters for subdivisions of the Boundary member. The engineer canthus develop an extremely detailed description of the reservoir for studies of reserves, waterflood predictions, etc.
The Boundary Lake field is situated in northeastern British Columbia and covers an area of about 100 square miles. Oil production is from a thin (0 to40 feet) carbonate bed, the Boundary member of the Triassic Charlieformation.
Previous studies in the field have shown that the sonic logs may be reactingto changes in the lithology of the reservoir (Jeffries and Kemp,1963). Subsequently, Meneley made a detailed study of representative Boundary Lake cores. This report outlines some of the results obtained incorrelating his lithological descriptions with computer-manipulated logdata.
Sonic logs from all available wells in the Boundary Lake field (Figure1) were digitized by spot-reading them at 6-in. intervals over thereservoir section. This information was fed to an IBM 1410 computer, and the output correlated with core-analysis porosity data from thirty-seven wells.Using a "cumulative" calibration technique (Holgate, 1960), atransit-time-versus- porosity plot was developed (Figure 2). Thisempirical relationship was used to convert all sonic log readings toappropriate porosity values. Detailed examination of a number of cores showedthat distinctive lithological types could be associated with sonic log characteristics (Figure 3). Cores from the southern part of the fieldwere checked to identify various rock-type occurrences.
By means of sonic logs, correlation sections were constructed across the southeastern part of the field, and individual zones were followed over wide areas.