One thing I could never understand is how sulfur gets in the oil.
Sulfur is a volcanic product, from deep in the earth, and no organism decaying yields enough sulfur to produce all the sulfurous oil out there.
Also, aren’t there reports of fields that had been pumped dry, but years later were replenishing themselves with oil?
Sulfur kills plants,
so why is there so much sulfur in coal,
which is supposedly compressed plant matter.
Yes. I understand that in some cases it is just that technology has allowed us to get at previously capped oil, in some cases the high price of oil has made it economically feasible to go after the oil that was otherwise to expensive to extract, and yet in other cases there is just plain more oil there.
Sulfur comes from evaporites deposited in and around the reservoir. The most common is anhydrite, which is CaSO4. Salt, also known as halite (NaCl) is another. They were deposited in hypersaline waters, such as the Dead Sea of today. Yes, there have been fields that have “burped” up some more oil but it probably leaking up the faults that are the trap for the field. Once the pressure is drawn down from production, you can get mini-earthquakes as the faults compensate for the pressure differential.