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Few wells had penetrated the Cardium sandstone, and little was known about it. Along the Rocky Mountain foothills southwest of Edmonton, the Cardium outcropped at the surface, but at wells drilled in the Edmonton area it was not present. Somewhere between Edmonton and the foothills the wedge-shaped sandstone must pinch out, and near the point where it pinched out there was a possibility of an oil accumulation, trapped by an impervious layer of shale. The Pembina No. 1 well might be near that pinch-out line, and thus Nielsen's prognosis listed the Cardium as one of the secondary oil prospects. The top of the Cardium sandstone was projected at 5,240 feet, and Nielsen's prognosis called for no cores to be taken from this formation "unless samples show good porosity or oil stain. "2
The well was spudded in on February 23, and as the drilling bit ground toward its objective nearly two miles below the surface, the well site geologist examined the rock cuttings returned to the surface in the circulating drilling mud, looking for the changes in rock types which would signify the progression from one formation to the next, and for indications of oil staining which might hint at the presence of an oil accumulation.
The first prospective zone was the Cardium. It wasn't easy to pick the top of this sandstone from the rock cuttings, since the formation was not widely known or easily recognized. From oil-stained rock cuttings, the well site geologist picked the top of the Cardium sandstone at 5,330 feet, and a drillstem test was ordered to determine whether or not the formation contained oil in commercial quantity.
A drillstem test allows formation fluids, such as oil, water, or gas from the interval being tested to rise up the drill pipe, propelled by the formation pressure. On tests of a high-pressure, prolific oil-bearing zone, such as a Devonian reef, oil will rush up the drilling pipe and flow at the surface at a rate of several hundred or even several thousand barrels a day. On tests of less permeable and lower-pressure zones, the formation fluid may rise only a few hundred feet toward the surface, and is then trapped in the drill pipe by a valve. The string of drill pipe, in 90-foot stands, is pulled to the surface to find out what, if anything, has risen in the pipe during the test period.
Nothing flowed to the surface during the test of the Cardium sand. When the valve was closed and the pipe pulled, it was found that the bottom 11 0 feet of the drill string contained a mixture of drilling mud and formation oil.
It was the first indication of oil that had been found in Socony's new regional district, but there was nothing to indicate a commercial discovery. It looked just like thousands of other oil shows that had been found throughout Western Canada, teasers which eventually produced little or no oil.
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