ON THE SPONTANEOUS RENEWAL OF OIL AND GAS FIELDS

V. I. Sozansky, Dept. Marine Geology, National Academy of Sciences, Ukraine

J. F. Kenney, Gas Resources Corporation, U.S.A.

P. M. Chepil, Institute Naukanaftogas, Ukraine

Oil and gas fields are dynamic systems undergoing constant depletion by diffusion, effusion, and chemical decomposition, and constant renewal by influx of new volumes of hydrocarbons. Many oil and gas fields are recharging and effectively inexhaustible, but at rates of recharging typically much smaller than the rate of oil and gas withdrawal by production.

The erroneous notion that the Earth’s supply of natural petroleum, both oil and gas, is becoming depleted and will soon be exhausted, has recently been widely asserted. These assertions have often been promulgated in connection with equally erroneous claims about a factually non-existent phenomenon called “Peak Oil”. According to the purveyors of these insupportable claims, the world-wide supply of oil will be exhausted within 20 years, and that of natural gas within 50 years, after which petroleum exhaustions mankind will supposedly suffer energetic collapse and an accompanying collapse of civilization.

These pessimistic ideas about the future of the petroleum industry are based upon a scientifically indefensible and discredited notion that oil originates from some miraculous (but still unspecified) spontaneous transformation of biological detritus in the thermodynamic regime of pressures and temperatures found in the near-surface crust of the Earth, - i.e., upon the notion of a “biological-origin-of-petroleum [“BOOP”]. The BOOP notion has been rejected by competent scientists since the end of the 19^th century because it stands glaringly in violation of the most fundamental laws of nature. The hydrocarbon molecules that comprise natural petroleum are highly reduced and of high chemical potentials. Biological molecules are oxidized and of low chemical potentials. Crude oil does not obtain from decayed fish, dead dinosaurs, putrified cabbage, plankton, or any biological matter.

Because the notion of BOOP requires a very restricted quantity of natural petroleum within the Earth, there have been almost continuous alarms raised predicting imminent petroleum exhaustions, - none of which has ever come to pass (of course). The American geologist Price (1947) observed that, approximately every five years since Drake drilled the first oil well in North America, some person has announced a dire prediction of an imminent exhaustion of oil resources. The persons making such predictions have often been considered to be “experts” possessing special information about petroleum resources and geology. All have been believers in BOOP.

In 1886, the American geologist C. A. Ashenbenner (Price, 1977) urged a strong conservation policy for the oil reserves in the U.S.A., because (as he predicted), the American oil fields would “soon be depleted” and were “nearing exhaustion”. In 1906, the American petroleum geologist D. T. Day, reported to the White House that oil reserves in the U.S.A. would be completely exhausted between 1935-1943. In 1920, the chief geologist of the United States Geological Survey, D. White (Pratt, 1942), predicted that production of oil in the U.S.A. would “peak” within 3-5 years, and thereafter begin to decrease, and would be exhausted within 18 years. White’s predictions were supported by the American Association of Petroleum Geologists.

Thus has continued the ill-informed litany that “the human race will run out of petroleum soon.” Such predictions of an imminent exhaustion of oil and gas resources and of an inevitable energy crisis were loudly proclaimed during the Arab oil embargo in the 1970’s.

The American geologist H. Hedberg (1971) called the 20^th century the Age of Petroleum. He wrote that there have been the Stone Age, the Bronze Age, the Iron Age, and that future historians may look back to a current brief period of the development of the human race, 200-300 years at most, as the Age of Petroleum, a period when the human race was engrossed with the finding and destruction of one of the very minor constituents of the earth’s crust – a unique fluid called petroleum. He asserted that reserves of oil on the globe are limited and soon would be depleted. He supposed that in human history the Age of Petroleum will have been only a brief episode in history. Further, Hedbert claimed that, if Alexander of Macedonia or Julius Caesar had powered their armies with petroleum as do modern military machines, the world supply might have been used long ago, and if Columbus’ Santa Maria had been an oil-powered motor ship, there might not be gasoline for our cars today.

Modern petroleum science recognizes that the hydrocarbon compounds of natural petroleum are generated spontaneously only at the very high pressures found in the deep crust or upper mantle of the Earth. Natural petroleum is a primordial, abiotic fluid which has penetrated the upper parts of the crust from great depth, usually along deep faults. Modern petroleum science thus provides a very different perspective of the future of the oil and gas industry.

The world-wide reserves of oil and gas were analyzed by Lasaga & Holland (1971) from both the perspectives of BOOP and an abiotic origin of petroleum. By their estimates, the maximum quantity of crude oil that could have been produced by all biological matter on Earth could be represented by a thin 2.5mm film uniformly covering the Earth’s surface. Their estimates of the quantity of crude oil that could be produced abiologically could be represented by a thick 10km (!) layer uniformly covering the surface of the Earth. This difference estimates that abiotic petroleum must be at least 8 million times greater than could ever be expected from BOOP. Thus modern petroleum science predicts, even by the early estimates of Lasaga & Holland, that there exist tremendous quantities of petroleum, sufficient for the needs of humanity for thousands of years.

The study of oil and gas fields shows that most oil and gas reservoirs are recharging systems. In many regions data have been obtained which establish that oil and gas constantly are being replenished to producing fields.

The scientific problem of replenishment of oil and gas reserves was first addressed by Russian petroleum scientist V. A. Sokolov, who studied extensively the problem of the diffusion and micro-filtration of hydrocarbons through rocks. Sokolov came to the conclusion that any gas or oil field, irrespectively of its size, will be destroyed by diffusion and effusion within 200 million years without an influx of hydrocarbons from greater depth.

The subject of the influx of hydrocarbons into oil and gas fields was first raised by the geologist L. I. Baksakov and reported at the 3^rd World Petroleum Congress, Bucharest, 1907. Baksakov reported that more oil had been produced from the Middle Miocene rocks of Starogroznenskoye field than the volume and porosity of these rocks could contain. He concluded that oil from greater depth fills up the Middle Miocene reservoirs. Influxes of oil were ascertained also in other fields of the Grosnett Petroleum Corporation. Reserves of some fields were observed to increase by 300% - 400% greater than originally estimated. Recently, many shallow oil wells in Chechnya, which had been shut down for long periods because of military operations and which had been previously exhausted, have now been restored to production.

American geologists have known for a long time that the estimates of recoverable oil and gas in producing fields usually increase. This phenomenon is called reserves growth. Analysis of exploration and production data shows that, world-wide, hydrocarbons (both crude oil and natural gas) volumes added to reserves by reserve growth are much greater than the volumes of new field discoveries.

In the U.S.A., the unexpected increased production of oil from Eugene Island Block 330 has drawn particular attention. This field was discovered in 1971 by the well Pennzoil 1. Production from this field is from 25 Pliocene-Pleistocene sandstone reservoirs at depths ranging from 1290-3800 m. In the early 1980’s, the flow had dropped to 4,000 barrels of oil per day. Then suddenly production increased to 13,000 barrels, and estimated reserves were increased from 60 to 400 million barrels.

The recharging of dynamic reservoirs in the Gulf of Mexico has been studied by several institutions directed by R. Anderson of the Lamont Doherty Geophysical Observatory. The investigations have established that the rate of increase in the volume of oil in the reservoirs of Eugene Block Island 330 is approximately equal to the rate of extraction. Hydrocarbons migrate into the Eugene Block Island 330 field from geo-pressured zones along a large growth fault system in the Eugene Island area.

Recent studies of oil and gas fields in Ukraine have established that these reservoirs are also being recharged by inflow of hydrocarbons from great depth. Measurements show that 2x10⁹m³ of methane enter the giant Shebelinka gas field in the Dniepr-Donets depression every year. In 2007, the Ukrainian State Commission responsible for the measurement of petroleum resources increased the official reserves of the Shebelinka field by 10⁹m³ which have been attributed to an influx of deep gas. The reserves of the Shebelinka field were initially estimated to be 4.3x10¹¹m³ of methane. This field has now produced already 6.0x10¹¹m³ of gas.

Fig.1. Reduced average pressure vs. cumulative gas production

for the Shebelinka field (after A.A.Barenbaum et all, 2005).

In Ukraine, the gas fields Proletarske, Bilousivka, Chornukhi whose total produced gas was 20.6x10¹²m³, were abandoned as exhausted fifteen years ago, along with several other similarly exhausted fields. However, when tested recently, these fields now produce the same quantity of gas, at the same pressure and rate of production as when initially discovered.

The pressure distribution within oil and gas deposits in formations at different depths can establish the deep origins of petroleum. An example of such has been measured in the Rudovsko-Chervonozavdske gas-condensate field in the Dniepr-Donets basin. The depths of the reservoirs in this field are all less than 2 km. In the Tournaisian reservoir, the pressure gradient is 1.45, i.e., 45% higher than hydrostatic pressure. In the higher section of the field in the Lower Visean formation, the pressure gradient is only 1.05-1.15. In the still higher Upper Visean, the pressure gradient has fallen to 0.95-0.07. Thus the distribution of pressure of pressure in that field indicates that gas enters the reservoirs from the depth from where it fills deep horizons in the first place.

Substantial inflows of deep oil have been observed in big Ukrainian fields Hnidyntsi and Lelyaki, Dniepr-Donets depression. From these fields three times more oil has been produced than estimated reserves. The fields are continuing to be under the development. In light of these facts, the following practices should be carried out in oil and gas fields.

- Oil and gas fields form very quickly during the first dozens of years.

- All “old” oil and gas fields considered previously to be exhausted should be thoroughly investigated to ascertain the quantities of oil and gas that have accumulated since the fields were shut in.

- The optimum balance between production and recharging should be determined in order to prolong the period of recovery between replenishments.

- The scientific body of knowledge concerning the cycles of regeneration of oil and gas deposits should be increased and extended.

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