Pembina: The Hidden Elephant

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Still, there was always a chance that this could be the exception. In Nielsen's opinion the oil found in the drillstem test warranted further eval­uation of the formation, if not immediately, then at least after the well had reached its final contracted total depth, another 4,000 feet down. In a wire March 27 to Socony's Calgary office, Nielsen recommended obtaining side­wall cores and running electric logs over the Cardium sand. "We did not obtain a core from the Cardium and it would be very useful to have some for porosity, permeability and fluid content analysis," Nielsen wired. "This would be very useful in deciding future program for Cardium."

An electric log of a drilled hole looks something like a cardiogram chart of your heart. Electric impulses measure the characteristics of the rock sequences penetrated, indicating the top of each and giving some hints as to which formations might contain oil or gas. The log of the Pembina well indicated that the top of the Cardium sand was actually 16 feet higher than had been established by the well site geologist on the basis of the drilling samples. As a result, the interval covered by the drillstem test might have missed the best part of the sand.

"In view of the result of the microlog and sidewall coring, we feel that further testing of the Cardium sand is imperative before the well is completed," Nielsen advised the Calgary office. He recommended that a string of seven-inch easing be cemented in the hole from the surface to a depth of 5,428 feet, and that the hole then be deepened to its projected depth of 9,400 feet. This casing would protect the Cardium sandstone from being plugged up by drilling mud while the hole was being deepened. Later, the Cardium could be further tested through perforations shot through the seven-inch casing.3

The string of intermediate casing was set and drilling resumed, but not without difficulties. On April 6, Nielsen wired Calgary: "Unfortunately yesterday a one-foot wrench was dropped into the hole . . . what do you propose?" The wrench was fished out by a powerful fishing magnet lowered down the hole on a wire line. The spring thaw turned roads in the Pembina area into quagmires and severely ham­pered the movement of drilling mud and supplies to the well site.

In May, the well reached its total depth of 9,425 feet without encountering further shows of oil, and was plugged back for more tests to further evaluate thc Cardium. A perforating gun was lowered down the hole, and one-inch holes were shot through the casing into the Cardium sandstone. Tests of the formation yielded only very small amounts of oil, far from enough to make a producing oil well. It still looked as though the well was no more than a teaser.

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