It is true the the hydrothermal vents do produce some hydrocarbons. They are released into the ocean and microbes eat it as a source of food. These vents are not a source of the petroleum we produce. How many oilwells are in Hawaii or Iceland? Hawaii sits on an oceanic hotspot and is the largest volcano on earth. Iceland is the top of the Mid-Atlantic rift and is all volcanic. Not one drop of oil has been produced from either.
could be too close to the heat or the rock isnt compatible with the process... where as the middle east, no volcanos and a huge sand filtration system before the water gets to the hot spots... just throwin it out there...