Environmental Aspects Of Hydrocarbon
ENVIRONMENTAL ASPECTS OF HYDROCARBON
RESOURCES DEVELOPMENT ON UKRAINIAN SECTOR
OF THE BLACK SEA SHELF
T.A. Safranov1, E.P. Larchenkov2
1Hydrometheorological Institute of Odessa, Ukraine
2I.I. Mechnikov National University of Odessa, Ukraine
Potential resources of hydrocarbon in Ukraine according to current geological prognosis have been estimated about 6,4109 t of conditional fuel. Proved reserves oil and gas are 230106 t and 1165109 м3 accordingly [1]. The reserves could ensure the production of 7- 8106 t/year of oil, and 30 – 35109м3/year of gas. According to State Programme “Oil and gas for Ukraine until 2010” planned for 2000 year oil and gas production should be raised up to 5106 t of oil and 27109 m3 of gas, but, actually, in 1998-2000 it is kept near 3,8-4106 t of oil (8 % annual demand), and 17 - 18109 m3 of gas (15 % annual demand). It is possible to double the production, but the problem is that it is very difficult to develop the resources because main part of them are in deep traps on land, or on relatively unexplored shelf of the Black Sea [2]. Nevertheless, it is assumed that the development should be economic due to big deficit of hydrocarbons, however, usually, ecological risk does not take into consideration under these estimations. It needs to emphasize that according to geological and geochemical criteria gas fields should predominate on the NW Black Sea shelf [3], and their development is not so dangerous for marine environment like oil fields.
Another source of hydrocarbons is hydrohydrates. The hydrohydrate is crystal matter where cavities of crystal grid of water are included gas molecules with diameter not more than 6,710-8 cm (СН4, С2Н6, С3Н8, i-С2Н6). Usually one crystal grid includes 6 molecules of Н2О and 1 molecule of СН4, which is very condensed (up to 25 MPa), therefore 1 м3 of water is able to interlink 200-250 м3 of methane [4]. Since it is necessary high pressure and low temperatures for hydrogydrate creation, they are common in deepest parts of oceans and seas. Opportune conditions for creation of hydrohydrates like
6Н2О1СН4 are under sea bottom where sea depth is not less than 400-500 m [5]. According to the bathymetry [6] there are not similar thermobarometeric conditions on the NW Black Sea shelf and there is no prospective for discovery of hydrogydrate deposits here. Bay the way, the techniques for exploration and exploitation of hydrohydrates are under development yet, and, also, they should be many technical problems due to hydrogen sulphide contamination of the seawater in the Black Sea.
Discovered on the NW Black Sea shelf eight gas fields and real perspectives for new discoveries is the base for increasing of hydrocarbon production in the Southern region. Large part (ca. 60-65 %) of expecting investments for the region is planned to be spent for hydrocarbon exploration and exploitation. Accordingly it is predictable that much intensive exploration and exploitation of hydrocarbons on the Ukrainian shelf of the Black Sea should leads to an increasing of technogenous impact on the sea environment and its degradation.
The North West Black Sea shelf ecosystems are undergone by impact of various natural and technogenic factors, e.a. eutrophication, contamination by waste loading water of major rivers as Danube, Dniester and Dnieper, damping, exploitation of mineral and natural resources, and intensive navigation. Currently exploitation of Golytzino, Schmidt, and Stormovoe gas fields and exploration of new fields do not negatively affect on the sea environment [7], but this is not so much the safety of the exploration and drilling as small exploration activity.
Currently technogeneous influence on the Northwestern Black Sea shelf leads to pollution of seawater and bottom sediments by oil, heavy metals, degradation of living conditions for hydrobionts and so on. Generally the oil comes to the NW part of the Black Sea by influxes of big and small rivers, industrial and domestic wastes and its content is much higher on nearest offshore. However, there is some evidence that areas of exploration for hydrocarbons are contaminated by oil as well [8].
Drilling for hydrocarbon exploration have been done on fifteen places. Ecological researches carried out by “Odessamorgeologiya” during 1991-1997 have shown that the oil are concentrated within sea bottom sediments near drilling platforms where it concentration can be up to 4 mg/g of dry matter and this more than 20 times that the content in unpolluted parts of the Azov and the Black seas. Increased contents of oil presented by transformed asphalten-tar compounds have been measured in areas on developed gas fields Golitzino and Shtormovoe. Total amount of the oil in seawater exceeds for 1.3 – 3.3 times marginal rate of concentration (MRC); it is equal 0.05 mg/l for areas of fishing grounds. Thereto increased concentrations of other pollutants have been measured [9].
According to the results of ecological investigation carried out by “Odessamorgeologiya” on many unexplored areas of the NW shelf of the Black Sea the contents of liquid hydrocarbons in both surface and near sea bottom water are nearly equal. Thus, they are not more than 100 mcg/l and light factions within them account 33-46 % on areas of Ushakov and Zonalnaya blocks. Oil content within bottom sediments near Zmeinyj Island is from 680 to 1740 mg per kg of dry weight, and also the content has been reduced seaward, that can be interpreted as their source is Danube river influx. In October 1998 the measurements of oil content done by “Odessamorgeologiya” on area of Bezymyanyj block (northeastward from Zmeinyj Island) have been shown that on some stations the content within surface water is up to 39.1 mg/l with visible trend of increasing its northeastward. Oil content within near bottom water reached 32 MRC, but it was not measured within bottom sediments.
Risk of environment pollution and aggravation of ecological state of offshore ecosystems varies for various stage of hydrocarbon exploitation and, in general, depends on using technologies. Only comprehensive approach for improving of exploration, exploitation and transportation hydrocarbons is able to reduce negative effects on the environment and to take into account issues of environment conservation such particular area as the Northwestern shelf of the Black Sea that is undergone by many factors negatively affect on the environment and adjacent to the land with high concentration of industrial and agricultural complexes, and useful recreation resources. This is very complicated task in term of technique, economy and ecology, and it is necessary to solve it carefully.
Reference
1. Danilishin B.M., Dorogunzon S.I., Mistchenko V.S. at all. Natural resources for sustainable development of Ukraine. – Kiev.: RVPS of Ukraine, 1999. – 716 p. (in Ukrainian)
2. Shpak P.F. at all. Oil- and gas bearing regions and hydrocarbon resources of Ukraine. – Geol. J., 1992. –No 5. – 53 – 64 pp. (in Russian)
3. Larchenkov E.P., SafranovT.A., Esipovich S.M., Yanko V. Evolution and main factors of petroleum potential forming of Karkinit Depression, Nopth Black Sea. - 2nd International Symposium of the Petroleum Geology and Hydrocarbon Potential an the Black Sea Area. 22-14 September. Istambul, 1996.
4. Krayushkin V.A. Hydrohydrates under bottom of the Ocean. – Geol. J. – 1991. – No 6. – 57 – 66 pp. (in Russian)
5. Korsakov O.D. at all. Hydrohydrates of the Black Sea as nontraditional hydrocarbon resources. –Geol. J. - No 6. – 67 – 76 pp. (in Russian)
6. Zaitsev Yu. The Most Blue in World. Black Sea Environmental Series, volume 6. – UN Plaza, New York, NY 10017 USA. –1998.
7. National report on the state of environment in Ukraine in 1998. – Kiev: Minekobezpeki of Ukraine, 1999. – 161 p. (in Ukrainian)
8. Safranov. T.A., Larchenkov E.Р., at all. Main factors of north-western Black Sea shelf pollution by hydrocarbons. – Intern. Forum – Conference of Euroregions “Peace and Security”. – Ivano-Frankovsk, 2000. (in Russian)
9. Sebakh L.K., Pankratova T.M., Petrenko O.A. Valuation of the state of the Black Sea ecosystem under current anthropogenis stress. – Environmental issues of the Black Sea. – Odessa: OCNTEI, 1999. – 145 – 149 pp. (in Russian)
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