While it is true that some oil fields do not conform to the standard model of a fixed amount of oil trapped in a sedimentary basin, these examples are accommodated by the biogenic model. For example, the White Tiger field (Cuu Long Basin) cited above is located in an area where significant normal faulting brings relatively young sedimentary rocks into contact with older, fractured horst blocks of igneous rocks.[15] The produced oil is described as typically lacustrine (derived from lake deposits), consistent with the migration of hydrocarbons from the organic-rich sediments into the fractured basement.
In Eugene Island 330, a large production area of that is currently being recharged, a deep source rock is indicated, and the chemical composition of the recharging oil strongly indicates that it is leaking from a deep, intermediate reservoir.
One type of unusual deposit that one might to expect to find if the abiogenic hypothesis is true would be hydrocarbons trapped in sedimentary basins that do not contain conventional source rocks. Evidence for such deposits is lacking. Many economically disappointing wells have been drilled into geologic structures that would be expected to trap hydrocarbons, but there are no hydrocarbons present. Oil companies have learned that an appropriate source rock is necessary before they will commit to drilling a well in a potential new field.
Wallace G. Dow, an AAPG member and consultant in The Woodlands, Texas, calls the Cuu Long oil “paraffinic, classic lacustrine crude” expelled into fractured basement from lower source rock.
“The oils in the basement are virtually identical to the oils in the sandstone sitting around the basement,” Dow said.
“This is the key — they migrate updip through faults into the basement, in horst blocks,” he said.
Dow emphasized that the oil’s components indicate a lacustrine organic facies with lipid-rich, land-plant debris and fresh-water algal material, refuting theories of abiogenic origin in this area.
Where are the fields found in a crystalline bedrock away from sedimentary basins? There is no drilling on a large scale in bedrock. The Soviet superdeep well in the Kola peninsula in the basement has not progressed beyond 12000 m for more than 10 years. Furthermore, drilling deep wells over 5000 m does not mean drilling in crystalline bedrocks. The White Tiger field in basement (as many others) is perfectly explained with hydrocarbons generated from sedimentary source-rock.
Related Comments (1)
There is no such thing as “fossil fuels” (in the context that that misnomer is typically used); get over it. Your parroting of the oil company rant about “appropriate source rock” has the EXACT reverse effect versus the one you obviously intended: Big Oil promoting the truth about oil sourcing/supplies? Don’t make me laugh, even when at a check-out counter level of expertise. When at the level of physical chemistry you studiously avoid simpleton concepts like density: Since when are hydrocarbon lighter than either sedimentary rock or the water above them (in the case of Cuu Long Basin) the water above? Well then, if the answer to that question is so obvious, how is it you neglected to tell us that your biogenic ramblings require that hydrocarbons defy gravity and migrate DOWN!? Absurd. You babble, “One type of unusual deposit that one might to expect to find if the abiogenic hypothesis is true would be hydrocarbons trapped in sedimentary basins that do not contain conventional source rocks. Evidence for such deposits is lacking.” You mean like the Siljian Ring? Before you babble any further, Siljian Ring was NOT intended to produce cash. It was intended to provide science (heaven forbid!), which was later referenced as investment justification during the drilling for cash, I mean oil, at Cuu Long Basin, et al. Tell me, where are all those dinosaur bones on Titan? I mean, after all, CH4 is a “fossil fuel,” right?
http://links.veronicachapman.com/OriginsOfOil.htm