FORT McMURRAY, Alberta — At a camp for oil workers here, a collection of 16 three-story buildings that once housed 2,000 workers sits empty. A parking lot at a neighboring camp is now dotted with abandoned cars. With oil prices falling precipitously, capital-intensive projects rooted in the heavy crude mined from Alberta’s oil sands are losing money, contributing to the loss of about 35,000 energy industry jobs across the province. Despite a severe economic downturn in a region whose growth once seemed limitless, many energy companies have too much invested in the oil sands to slow down or turn off...