Drilling & Development of Oil and Gas Fields in the Dnieper-Donetsk Basin
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J. F. Kenney, V. A. Krayushkin, T. I. Tchebanenko, V. P. Klochko, Ye. S. Dvoryanin The modern Russian-Ukrainian theory of deep, abiotic petroleum origins is by no means simply an academic proposition. After its first enunciation by N. A. Kudryavtsev in 1951, the modern theory was extensively debated and exhaustively tested. Significantly, the modern theory not only withstood all tests put to it, but also it settled many previously unresolved problems in petroleum science, such as that of the intrinsic component of optical activity observed in natural petroleum, and also it has demonstrated new patterns in petroleum, previously unrecognized, such as the paleonological and trace-element characteristics of reservoirs at different depths. Most importantly, the modern Russian-Ukrainian theory of deep, abiotic petroleum origins has played a central role in the transformation of Russia (then the U.S.S.R.) from being a "petroleum poor" entity in 1951 to the largest petroleum producing and exporting nation on Earth. In this article is described a project for exploration and production of petroleum in an area which had been previously condemned, according to the perspectives and reasoning of the old "biological-origin" hypothesis: the northern flank of the Dnieper-Donets Basin. This specific project has been chosen because it is a "pure" modern project: the geological area explored is one which had been extensively studied in the past and had been previously condemned as possessing no potential for petroleum production; the exploration techniques applied, from the initial work-up, through the well planning, to the production tests have been carried out in ways peculiar to such for abiogenic hydrocarbons in crystalline environments; and the scientific tests upon the petroleum produced were specifically designed to test the assumption that the oil and gas originated at great depth in the Earth. The Dnieper-Donets Basin runs in a NW-SE direction between 30.6°E-40.5°E; its northern and southern borders are traced from 50.0°N-51.8°N and 47.8°N-50.0°N, respectively. For the first 45 year period of the geological study of the Northern Monoclinal Flank of the Dnieper-Donets Basin, its sedimentary, metamorphic, and igneous rock had been condemned as possessing no potential for petroleum production for reasons of the complete absence of any "source rock" (so-called) and the presence of active, strongly-circulating artesian waters. Recently the area was reexamined according to the perspective of the modern theory of deep, abiotic hydrocarbon origins.
Because the modern theory of hydrocarbon origins recognizes hydrocarbons as primordial material erupted from great depth, the exploration process began with a detailed analysis of the tectonic history and geological structure of the crystalline basement of the Northern Monoclinal Flank of the Dnieper-Donets Basin. Following the tectonic and deep structural analysis of the area, a program of geophysical and geochemical investigations, developed in accordance with the modern theory of petroleum peculiarly for the search for deep-seated petroleum, were conducted. During the first five years of exploration, in the early 1990's, of the northern flank of the Dnieper-Donets Basin, a total number of 61 wells were drilled, of which 37 are commercially productive, an exploration success rate of 57%. A number of the fields discovered are shown in the map in Fig. 1, together with their designation and type of petroleum fluids produced. The initial flows from the productive wells varied between 40-350 metric tons per day of oil and 100,000-1,600,000 cubic meters of gas per day. The specific gravity of the oil from the upper sedimentary levels ranges between 25°-48°API, that from the Precambrian crystalline basement rock between 28°-48°API. The sulfur content of the oil is uniformly less than 0.3%. The gas from the Precambrian crystalline basement contains also condensates. Of the fields described below, the Khukhrya field contains reserves in excess of 18 million metric tons of oil, and the Yulyovskoye oil and gas field more than 27 million tons of oil equivalent. The specific formations and depths from which petroleum has been discovered and is now being produced are as follow: 1.) Production from the upper sedimentary levels: The oil and gas bearing reservoir rocks in the upper sedimentary levels are Middle and Lower Carboniferous period sandstones. The oil wells which produce from the Carboniferous period sandstones have reservoir depths at the following levels: 3133-3172 m; 3200-3212 m; 3530-3543 m; and 3666-3688 m. The gas wells which produce from the Carboniferous period sandstones have reservoir depths: 1738-1754 m; 1802-1835 m; 2034-2063 m; 2813-2854 m; 2905-2994 m; 2910-2943 m; 2987-3526 m; 2990-3176 m; 3080-3339 m; 3089-3135 m; 3425-3603 m; 3439-3442 m; 3450-3469 m; 3472-3500 m; 3506-3528 m; 3530-3543 m; 3638-3724 m; 3824-3845 m; 3874-3933 m; 3962-4002 m; 4007-4100 m; 4423-4463 m; and 4500-4505 m. 2.) Production from the Precambrian crystalline basement: In addition to these reservoirs in the sedimentary rock, above, the exploration drilling has discovered five reservoirs in the Precambrian crystalline basement rock complex at depths ranging from several meters to 200 meters below the top of the crystalline basement. From such traditionally unusual reservoir rock, oil and gas wells produce from the following levels: 3135-3151 m; 3164-3172 m; 3167-3173 m; 3192-3196 m; 3200-3280 m; 3213-3235 m; 3240-3260 m; 3244-3272 m, 3432-3498 m; 3468-3480 m; 3501-3520 m; 3516-3529 m; 3521-3531 m; 3547-3550 m; 3552-3570 m; 3590-3612 m; 3610-3625 m; 3618-3687 m; 3636-3735 m; 3685-3695 m; 3735-3800 m; and 4020-4041 m. The trapping strata for the reservoirs in the Carboniferous period sandstones are shallower shale formations, as is typical for sedimentary reservoirs. The trapping strata for the reservoirs in the Precambrian crystalline basement are impervious, non-fractured, essentially horizontal zones of crystalline rock which alternate with the fractured, uncompacted, bed-like zones of granite and amphibolite. An example of the "stacking of the petroleum reservoirs is shown in Fig. 2 for the Yuliyevskoye oil and gas field. Following the discovery of these petroleum reservoirs, a series of quite different scientific investigations have been carried out to test the initial assumptions that the oil and gas have entered the reservoir formations from great depth. Those laboratory analyses are described here briefly. 1.) Analysis and correlations of trace element abundances in oil: The oil produced from all reservoirs and depths have been analyzed for correlations of their trace metallic elements. For example the ratios of Ni/V and of either Methane or Nitrogen have been measured. The abundances of the trace metals show a clear correlation and have thereby established that the oil at all levels share a common, deep source, characterized by diffusive separation, regardless of the age, type or circumstance of the particular reservoir rocks. 2.) Paleontology analyses of the oil, - and its significance: The Paleontology analyses of the oil in the shallower Permian and Upper and Lower Carboniferous sandstone formations have demonstrated the presence of spore-pollen and other microphytofossils of the Devonian and Proterozoic ages, establishing thereby upward migration from the deeper formations, which migration is not necessarily correlated to the age of either. The paleontology analyses of the oil from these wells has been performed by laboratories in Lvov, Minsk and Moscow. The proterozoic microphytofossils examined included the following: Protoleiospheridium conglutinatum Tim., Zonoleiospheridium larum Med., Leiominuscula rugosa Naum., Margominuscula rugosa Medw., Protoarchaeosacculina stava. Naum., Leiopsophosphaera giganteus Schep., Asperatopsophosphaera magna Schep., Strictosphaeridium implexum Tim., Gloecapsomorpha hebeja Tim., Turuchanica alara Rud., Pulvinomorpha angulata Tim. The observations from all laboratories have been that the proportion of proterozoic microphytofossils is usually equal to 70%-75% of the total spore pollen abundance in oil from every formation and reservoir, irrespective of the reservoir rock, its depth or its age.
3.) Bacteriological analysis of the oil and the examination for so-called "biological marker" molecules: The oil produced from the reservoirs in the crystalline basement rock of the Dnieper-Donets Basin has been examined particularly closely for the presence of either porphyrin molecules or "biological marker" molecules, the presence of which used to be misconstrued as "evidence" of a supposed biological origin for petroleum. None of the oil contains any such molecules, even at the ppm level. There is also research presently under progress which has established the presence of deep, anaerobic, hydrocarbon metabolizing microbes in the oil from the wells in the uppermost petroliferous zones of the crystalline basement rock in the Dnieper-Donets Basin. 4.) Measurement of elevated abundances of helium: The petroleum from all producing reservoirs manifest elevated abundance of helium. The natural gas and oil from, for example, the Yulyovskoye field contain not less than 180,000,000 m3 of helium. Helium is of deep origin and can be transported significant distances in the Earth's crust only by entrainment in another carrier fluid, typically hydrocarbons or hydrocarbons and carbon dioxide or nitrogen together, by which process it becomes concentrated in the carrier fluid. These results, taken either individually or together, confirm the scientific conclusions that the oil and natural gas found both in the Precambrian crystalline basement and the sedimentary cover of the Northern Monoclinal Flank of the Dnieper-Donets Basin are of deep, and abiotic, origin. The exploration drilling is still in progress and continues to yield success. As of this date (September 2001), there are more than 50 commercial commercially oil and gas fields in the 100kmÃ-600km strip of the northern flank of the Dnieper-Donets Basin. One field produces gas from Jurassic age sandstones; thirty-two produce oil or gas from middle-lower Carboniferous age sandstones; fifteen produce from both Carboniferous age sandstones and lower crystalline basement rocks (amphibolites, crystalline schists, granites, gneisses, granodiorites); two fields produce oil and gas solely from the crystalline basement. For the work here reported, the first four authors, who were principally responsible for the discovery of these fields, were awarded the State Prize of Ukraine in the field of Science and Technology in 1993. V. A. Krayushkin, T. I. Tchebanenko, V. P. Klochko, Ye. S. Dvoryanin J. F. Kenney Gas Resources Corporation, 11811 North Parkway, Houston, TX 77060, U.S.A. See also
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