问答题 翻译：A major oil company usually initiates the sequence of events that leads to the drilling of oil and gas wells in foreign fields, but independent oil operators pay for most of the wells in the United States. In fact, about 80% of all wells drilled in the U.S. today are financed by independents.
问答题 翻译：Practically every rig uses internal-combustion engines as its prime power source, or its prime mover.
问答题 翻译：Also specified in gas purchase contracts is the maximum amount of sulfur the sales gas may contain.