Complex sentence: Many of these laid-off employees went on to work and start up other oil companies in Alberta, creating a new group of Canadian producers, but many did not work in other oil companies and some left Alberta to find work elsewhere.
Split into simpler sentences: Many of these laid-off employees went on to work and start up other oil companies in Alberta, creating a new group of Canadian producers. But many did not work in other oil companies and some left Alberta to find work elsewhere.