I wondered myself about ecoterrorism. It surprised me that crude oil would be sufficiently volotile to explode. My impression is that crude takes a good deal of applied heat and a sustained ignition source to get it burning. Do we know that this was crude oil vs refined products such as gasoline? My only real experience was minimal around Bunker C fuel used in boiler for heating buildings. The ones I recall had an LP gas flame to get the Bunker C burning. I don't think a few sparks from metal on metal destruction would be enough unless the crude oil met up with a steady source of flame and heat. My thoughs here are strictly arm chair speculation and I would like to hear assesment of others.