Basically, if you need to burn one barrel of oil to extract one barrel of oil from the ground, then you have already lost. Here, "burn" is used very loosely and is an all encompassing term including electricity for workers, rigs etc. and also the physical petrol required for transport to the refinery and end customers. The cost obviously also includes the initial investment and factors in the life of the rig installation itself as well.
It seems that we're currently at an EROEI of 10:1 and it's declining pretty steadily (kind of obvious). The wiki article is pretty informative. And, a cursory search on reddit for the term "peak oil" also returns quite a few interesting results. Caveat Emptor though, since there are some loony conspiracy theories posted as well, so it's up to you to sift the wheat from the chaff.
if you interpret "need to burn one barrel of oil" as "need the energy of one barrel of oil", there will probably be some leeway, even below 1:1; oil is a very good energy carrier, and pumping up oil carrying a kWh of energy at the cost of more than one kWh of solar electricity or solar heat will probably be more efficient than using that energy to produce (in the literal sense, by chemistry, starting with CO2 and H2O) oil for some time.
Basically, if you need to burn one barrel of oil to extract one barrel of oil from the ground, then you have already lost. Here, "burn" is used very loosely and is an all encompassing term including electricity for workers, rigs etc. and also the physical petrol required for transport to the refinery and end customers. The cost obviously also includes the initial investment and factors in the life of the rig installation itself as well.
It seems that we're currently at an EROEI of 10:1 and it's declining pretty steadily (kind of obvious). The wiki article is pretty informative. And, a cursory search on reddit for the term "peak oil" also returns quite a few interesting results. Caveat Emptor though, since there are some loony conspiracy theories posted as well, so it's up to you to sift the wheat from the chaff.