I worked for Schlumberger much later (late 60"s early 70"s) so I suspect that the sources were less powerful by that time as the sensor technology had improved considerably by then. The most common radioactive survey when I worked for them ,measured the density of the formation by bombarding it with gamma rays from a cobalt 60 source. ( about 1 Curie if I remember correctly). The amount of radiation reflected back to the tool was measured and gave a measurement of the bulk density of the formation. If you knew the type of formation (sandstone or limestone were the only ones of interest as that is usually the only type you find oil or gas in) then you knew the density of the pure rock and could calculate the porosity of the formation. From resistivity surveys. you could tell weather the pore spaces were filled with water or oil or gas.
Shooting a well is also called perforating. The well is cased with steel casing which is cemented into the hole from top to bottom. To allow the oil to flow into the hole, explosive shaped charges are located opposite the production zone and fired electrically from the surface. These blow holes about 12 mm in diameter through the pipe & cement and into the formation about a metre deep.
I don't know if Wellex used some other technology in those days, but they were looked down on buy the Schlumberger engineers as a "poor cousin". Shclumberger was the acknowledged leader in the field. They did huge amounts of research, built all their own equipment in house,and never patented anything. They believed that they could stay 2 years ahead of their competitors and didn't give out any information. I had to sign all sorts of confidentiality agreements when I went to work for them.
It seams kind of unlikely that they would have a radioactive source downhole while perforating as the sensors were really sensitive to shock. The Schlumberger sources were about 20 mm in diameter and maybe 100 mm long. They were a stainless steel tube with a Cobalt wire in them that was the actual source. I suspect that you could put them in a shotgun and shoot them at a wall without causing a leak.
On the other hand, I heard rumours that a long time ago,(1950')somebody had found an earlier type of source on a lease in northern Alberta. They used to take the source out of the truck and place it in a roped off area on a corner of the lease. Some cat skinner found it and used it as a track pin punch and ruptured it. The source material was a powder in the case and contaminated himself and a big area. It was all supposed to have been hushed up. I don't know how true it was but it was one of those "oilpatch myths" that circulated.
Schlumberger crews were chopped and changed and moved all over the country so the movement of the crew probably didn't have any sinister connotations.