Sentence:  In the search for oil and <WSD>gas</WSD> , we make similar waves under controlled conditions with dynamite and learn from them where there are buried rock structures favorable to the accumulation of these resources . 
Meaning of the word marked with <WSD> tags:  a volatile flammable mixture of hydrocarbons (hexane and heptane and octane etc.) derived from petroleum; used mainly as a fuel in internal-combustion engines