HYDROCARBON POTENTIAL IN ENTRAILS OF THE EARTH OF UKRAINE AND MAIN TREND OF ITS DEVELOPMENT

О. Ю. ЛУКІН, академік НАН України, д-р геол.-мінерал. наук, професор, завідувач відділу (Український державний геологорозвідувальний інститут), lukin_alexander@ukr.net, https://orcid.org/0000-0003-4844-1617, І. П. ГАФИЧ, канд. геол.-мін. наук, директор з розвідки та перспективного розвитку (ДТЕК Нафтогаз), gafichip@dtec.com, Г. Г. ГОНЧАРОВ, завідувач сектору (Український державний геологорозвідувальний інститут), gggmorion@ukr.net, В. В. МАКОГОН, канд. геол. наук, завідувач сектору (Український державний геологорозвідувальний інститут), vlvlm@ukr.net, https://orcid.org/0000-0001-5810-517X, Т. М. ПРИГАРІНА, канд. геол.-мінерал. наук, головний геолог (Український державний геологорозвідувальний інститут), prig55@ukr.net, https://orcid.org/0000-0002-0256-9319

Ukraine are among of very limited number of countries-pioneers in the petroleum geology and hydrocarbon industry fields. There is no line in development of oil and gas (from prospecting and exploration on land and sea and different technical problems -up to and including oil and gas transport, building of gas-holders and so on), where Ukraine was not among pioneers. And at the present time in spite of long-term intensive mining, hydrocarbon potential of Ukraine is sufficiently powerful. In this respect the very significant is the fact that all ranges of oil and gas bearingness practically completely correspond to the Worlds ranges. So, the stratigraphic range of petroliferous formation in Ukraine is from pre-Cambrian to Pliocen including. Ukraine hydrocarbon and bitumen accumulation reservoirs are represented with all known sedimentary rocks and facies. The depth interval of commercial hydrocarbons pools distribution varies from first hundred meters almost to 7 km and apparently more than 8 km.
Deep petroliferous basins in Ukraine various from typically paleorift to subduction and accretion types.
Phase-geochemical diapason includes all known in the World types of hydrocarbons natural systems: from all kinds of natural bitumens and heavy oils to various gas-condensates (including pools of critical state) and all types of hydrocarbon gases. To this should be added that Ukrainian oils gascondensates and gases are distinguished with high quality and not contained admixed toxically components.
The oil-and-gas promising territories in Ukraine occupy about 80 % of total Ukrainian territory. Three petroliferous regions are known in our country ( fig. 1

ГОРЮЧІ КОРИСНІ КОПАЛИНИ
Voronezh crystalline massive and the Ukrainian shield, and also ukrainian segment of Donets basin; -the Western region includes together with pre-Carpathian foredeep and Transcarpathian deep, Lviv Paleozoic deep and Volyno-Podolian outskirts of East-European platform; -the Southern (Azov-Black sea) region is the most geotectonically-heterogenous (it includes the southern slope of Ukrainian shield, Pre-Dobrogean, Indol-Kuban and Northern Azov deeps, Karkinit-Northern Crimean-deep, North-Western and pre-Kerchian shelves of the Black sea).
The degree of development of hydrocarbon resources of the Eastern region achieves 58 %. 252 oil, gascondensate, gas and heterophase fields are discovered here. Nevertheless, this region leads both by unprospected HC resources category C 1 + D (~ 2,2 billions ton of conventional fuel) and by so-called stock of structures (in other words, by number of determined according to geologicgeophysical investigation predicted-prospecting target objects) that account for 326.
124 oil and gas fields are discovered in the Western region. The degree (stage) of development its hydrocarbon resour ces run as high as 45 %. Unprospected (undiscovered) resources account for 0,75 billions tons of conventional fuel. The stock of structures (target objects) is 165. 46 oil, gas and gascondensate fields are discovered in the Southern region. The degree of its development run as high as only 8 %, the stock of structures -target objects are 50.
Altogether in Ukraine over the whole preceding period it was extracted near 2 billions tons of conv. fuel. The amount of unprospected (undiscovered) HC resources (by category C 1 + D) is 5.3 billions tons of conv. fuel. This assessment is particulary minimal because it does take account a number of considerable promising lines of oil and gas prospecting. But even this the most reliable and justified part of the predicted HC resources is more than twice as large as the cumulative extraction of hydrocarbons from geological formation of Ukraine. And this is only part of the potential HC resources.
It is precisely potential resources characterize HC potential of geological formation of Ukraine. Indicated 5.3 billions ton of conv.

Fig. 1. Petroliferous regions of Ukraine
Reef-carbonate complexes of Ukraine are very promising for oil and gas. The world's characteristics of HC resurses testify that not only for oil but also for gas and condensate by no means less than the HC resources of terrigenous reservoirs. It is sufficient to mention that the most gas fields connected with Permian and Triassic (South Pars) and Jurassic (Iolotan) carbonate formations.
Carbonate formations of various geological age play great role in Eastern, Western and especially Southern petroliferous regions. Their HC potential are proved, but their degree of development of their potential HC resources no more than 10 %. The main part of carbonate reservoirs resources doesn't appears in those 5,3 billions of conv. fuel. Ukrainian because ukrainian petroleum geologists and geophysics had been for many years under wrong impression that carbonate formations are tight "plates" (Visean "plate" , Bashkirian "plate" an so on) and play the role of regional oil-gas proof thicknesses. But closer examination of them allowed to establish and maped a fuel are those that are provided by above mentioned stock of structures (target objects). These are far from distinct anticlyne structures as it was in the past but and geophysics (particularly seismic) prospecting are quite another. The total stock of such target objects are sufficiently large. Their number is above 540 objects.
Top priority task is additional prospecting of the largest fields ( fig. 2) and reanimation of exsousted productive reservoirs by the application of present-day methods. But the main strategic trends are connected with prospecting of reef-carbonate complexes and local bodies, deep and superdeep (more than 5,5-6 km) horizons, nontraditional and alternative resources.   Minimal assessment of total HC resources connected with nonanticlyne traps in terrigenous reservoirs is about 0,5 billion units of conv. fuels (half trillions m 3 of gas or half billions tons of oil).
All above-mentioned types of petroliferous traps are quite traditional in the World, but not completely traditional for Ukraine. So, we have great reserves connected with such pools.
Deep-seated petroliferous complexes. In due time just the great depths had been saved Ukrainian oil-gas exploration branch, oil and gas industry. Moreover, just owing to this line of prospecting and drilling, extraction of natural gas in Ukraine ranges up to about 68-70 billions m 3 per ear (in seventies years of XX century ( fig. 14). Tremendous (without any overestimation) ukrainian achievements in development of deep-seated HC pools (particularly discovery of 46 fields -with ~110 gascondensate, gas and also    established at the depth more then 6 km in Semirenkivske gascondensate field (Poltava region, central segment of DDD). Their evidence is self-decomposition of cores into thin discs with condensate and light oil films. According to a set of data such intervals are typical at the depths 5-7 and more kilometers. Deep-seated gas-condensate fields are at the stage of pool accumulation process according thermobaric, hydrogeologic, isotope-geochemical data ( fig. 16) with the pace that comparative with velocities of HC-fluid intensive extraction.
Within Poltava-Kharkov segment of the DDD that situated above Dnieper-Donets mantle plume there are localized the bulk part of prospected HC reserves and the most of potential resources of Lower Carboniferous -the main petroleum floor of the Eastern region. There are many very promising targets objects connected with deepseated terrigenous and carbonate reservoirs in this segment of DDD ( fig. 17).
Crystalline basement of different age (particulary pre-Cambrian) shows considerable pro mise of HC potential. This problem needs in special consideration in Ukraine. Now one can only to mention that just in Ukraine commercial HC potential AR-PR crystalline basement. The question is about intensive oil-gas accumulation in Eastern segment of joint zone between Voronezh anteclysa and DDD -Donets basin. Seven fields including great Yuliivka oil-gascondensate field have been discovered here.
A number of such zones are predicted within dilatansion zone within crystalline basement of Eastern, Western and Southern petroliferous regions.
Among indicators of such objects one ought to mention pools of gas in traps, connected with bazal strata of sedimentary cover.
An additional point to emphasize is that we predicted big and gigantic oil gascondensate and gas fields connected with massive reservoirs of deconsolidated Paleozoic -Early Mesozoic granites on the North-Western  Non-traditional HC sources. This trend has been seemingly very promising ten or even 5 years ago. Then the objects of shale gas were determined and prospecting works have been begun on Olesskaya (Lviv and Ivano-Frankivsk regions) and Yuzivskaya (Kharkive and Donetsk regions) areas. One ought to mention those objects were not the best. All efforts to develop this promising trend proved to be in vein by virtue of ecological and geopolitical reasons. Nevertheless, we argue with full responsibility argue that Ukrainian regions and Dnieper-Donets region first these are inexhaustible nontraditional source of gas during which shale, central-basin and free gas are deeply intertwined. This figure (fig. 19) demonstrates powerful Srebnian areal of gas-saturated Visean black shales. Their as evidenced by results of laboratory investigations and field tests. They are characterized with great content of kerogen and anomaly radioactivity. Bodies of good sandstone reservoirs with gascondensate pools occur within this black shale formation (particularly of large Rudovka field) ( fig. 20). The development of such fields must be realized so in order together with free gas from sandstones with effective porosity, to extract shale gas.
Another good case in point -Rudenkovske gas field ( fig. 21). Here together with considerable proved reserves of gas in terrigenous and carbonate reservoirs (blue colors), tremendous resources of shale and gas (Lower Visean black-shale suite) and central-basin gas (Upper Visean thickness of blackshale-sandstones thin intercalation).
We believe that the development of such hybride predominantly gas fields will be the very important trend of development to commercial level of the fields production capacity. Numerous oil zone of Carpathian region may be among them in sight. Here traditional oil pools in sandstones are combined with gas-saturated of Menilite black shales with intensive-fracturing caused by disjunctive-plikative tectonics.
It is pertinent to bring in mind that Ukraine has great reserves of coalbed gas and non-exhausted resources of methane dissolved in underground waters of abovementioned regions and connected with gas-hydrates of the ukrainian segment of the Black Sea.
From the aforesaid, it may be seen that collapse of Ukrainian fuel-energetic complexe is caused not by mythical exhaustion of natural HC resources but by collapse of the bulk of geophysics exploration and deep drilling ( fig. 22).