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Refilling Fields?
Abiotic theorists often point out evidence of fields refilling. The most-cited example is Eugene Island, the tip of a mostly submerged mountain that lies approximately 80 miles off of the coast of Louisiana. Here is the story as related by Chris Bennett in his article "Sustainable Oil?" on WorldNetDaily.com:
A significant reservoir of crude oil was discovered nearby in the late '60s, and by 1970, a platform named Eugene 330 was busily producing about 15,000 barrels a day of high-quality crude oil. By the late '80s, the platform's production had slipped to less than 4,000 barrels per day, and was considered pumped out. Done. Suddenly, in 1990, production soared back to 15,000 barrels a day, and the reserves which had been estimated at 60 million barrels in the '70s, were recalculated at 400 million barrels. Interestingly, the measured geological age of the new oil was quantifiably different than the oil pumped in the '70s. Analysis of seismic recordings revealed the presence of a "deep fault" at the base of the Eugene Island reservoir which was gushing up a river of oil from some deeper and previously unknown source. (8)
A "river of oil" from an unassociated deep source? This does sound promising. But closer examination yields more prosaic descriptions and explanations.
According to David S. Holland, et al., in Search and Discovery, the reservoir is characterized by
1. Structural features dominated by growth faults, salt domes, and salt-related faulting.
2. Thick accumulations of predominantly deltaic deposits of alternating sand and shale.
3. Young reservoirs (less than 2.5 m.y. old) with migrated hydrocarbons whose origins are in deeper, organic-rich marine shales.
4. Rapidly changing stratigraphy, due to deposition and subsequent reworking.
5. Numerous oil and gas fields with stacked reservoirs, long hydrocarbon columns, and high producing rates. (9)
While it is true that the estimated oil reserves of Eugene have increased, the numbers are not extraordinary. The authors note that "From 1978 to 1988, these operations, activities, and natural factors [including better exploration and recovery technology] have increased ultimate recoverable reserves from 225 million bbl to 307 million bbl of hydrocarbon liquids and from 950 bcf to 1.65 tcf of gas." Other estimates now put the estimate of total recoverable oil as high as 400 Mb.
None of this is especially unusual for a North American oil field: most fields report reserve growth over time as a consequence of Securities and Exchange Commission reporting rules that require reserves to be booked yearly according to what portion of the resource is actually able to be extracted with current equipment in place. As more wells are drilled into the same reservoir, the reserves "grow." Then, as they are pumped out, reserves decline and production rates dwindle. No magic there.
Production from Eugene Island had achieved 20,000 barrels per day by 1989; by 1992 it had slipped to 15,000 b/d, but recovered to reach a peak of 30,000 b/d in 1996. Production from the reservoir has dropped steadily since then.
The evidence at Eugene Island suggests the existence of deep source rocks from which the reservoir is indeed very slowly refilling - but geologists working there do not hypothesize a primordial origin for the oil. In "Oil and Gas - 'Renewable Resources'?" Kathy Blanchard of PNL writes, "Recent geochemical research at Woods Hole Oceanographic Institution has demonstrated that the wide range in composition of the oils in different reservoirs of the Eugene Island 330 field can be related to one another and to a deeper source rock of Jurassic-Early Cretaceous age." (10) Her article explains that this kind of migration from nearby source rocks is hardly unique, and discusses it in the context of conventional biotic theory. A technical paper by David S. Holland, et al., "Eugene Island Block 330 Field - U.S.A. Offshore Louisiana," published by AAPG, notes that the Eugene Island oils show
abundant evidence of long-distance vertical migration. Based on a variety of biomarker and gasoline-range maturity indicators, these oils are estimated to have been generated at depths of 4572 to 4877 m (15,000 to 16,000 ft) at vitrinite reflectance maturities of 0.08 to 1.0% and temperatures of 150 to 170C (300 to 340F). Their presence in shallow, thermally immature reservoirs requires significant vertical migration. This is illustrated on Figure 36, which represents a burial and maturation history for the field at the time of petroleum migration, that is, at the end of Trimosina "A" time approximately 500,000 years ago. A plot of the present measured maturity values versus depth is superimposed on the calculated maturity profile for Trimosina "A" time to illustrate the close agreement between measured and predicted maturity profiles. The clear discrepancy between reservoir maturity and oil maturity is striking and suggests that the oil migrated more than 3650 m (12,000 ft) from a deep, possibly upper Miocene, source facies. Petroleum migration along faults is indicated based on the observed temperature and hydrocarbon anomalies at the surface and the distribution of pay in the subsurface. These results are consistent with those of Young et al. (1977), who concluded that most Gulf of Mexico oils originated 2438 to 3350 m (8000 to 11,000 ft) deeper than their reservoirs, from source beds 5 to 9 million years older than the reservoirs. (11)
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