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Przegląd Geologiczny, vol. 55, nr 12/1, 2007

Przegląd Geologiczny, vol. 55, nr 12/1, 2007

Fig. 16. Principal geological regions of Poland (without the Cenozoic deposits): oil and gas fields (after Kamkowski P., 1993, modified)

was modernized first in 1960s when the oscillographic data recording was replaced by the analogue and the magnetic met-hods and later in 1970s when digital data recording was intro-duced. The latter completely updated in 1980s and 1991-94. The pioneers of these modern methods were: K. Sojka,

L. Rudzik, L. Król, Z. Śliwiński,

E. Poleszak, A. Kisłow, J. Buko-wicki, T. Rokosz, H. Tarnowski,

Z. Soja, S. Plewa and W. Twaróg (Jawor & Kruczek, 1994).

In the last years the Polish Oil and Gas Company became deeply restructured. The exploration and production divi-sions were established: the first one in Zielona Góra (prospec-ting the western and the northern part of Poland) and the next one in Sanok (for the eastem and the Southern part of Poland). The Department of Exploration in Warsaw concentrates mainly on exploration in foreign countries and on cooperation with compa-nies realizing their prospecting works in Poland.

Fore-Sudetic Monocline. In the Polish Lowland the first discovery of oil was in 1961 (borehole Rybaki-1) in the carbonates of Zechstein Main Dolomite Formation at depth of ca 1800 m. The initial oil output was morę than 100 t/d. From this oil field 130,000 t of oil was totally exploited. Discovering of the “Rybaki” oil field considera-bly influenced on intensifying exploration in the Polish Lowlands, and especially in the Fore-Sudetic Monocline area (Depowski et al, 1978).

In 1964 the first gas findings in the Rotliegend sandsto-nes and the Zechstein limestones were documented (Bog-daj-Uciechów gas field; Karnkowski P. et al, 1966). The resources of this field were estimated at ca 16 x 10⁹ m³ at the depth interval 1520-1620 m. Content of hydrocarbons is 57%, nitrogen — 42.5% and helium — 0.4%. From this field and the others around helium is liąuefied in a cryoge-nic factory.

Continued exploration in the next years finalized in discovering the new oil and gas fields from which the morę important are following (Fig. 16):

□    “Załączę” (1971), gas — av. depth 1400 m, the Rotliegend reservoir, resources — 23 x 10⁹ m³, methane — 74.2%, helium — 0.17%;

□    “Wierzchowice” (1971), gas — av. depth 1560 m, the Rotliegend sandstone and the Zechstein Limestone reservoirs, resources — 12 x 10⁹ m³, methane — 69%, helium — 0.31%;

□    “Kaleje” and “Klęka” (1974), gas — av. depth 3120 m, the Rotliegend reservoir, resources—1-2 x 10⁹ m³, methane — 80%;

□    “Żuchlów” (1978), gas — depth 275-1325 m, the Rotliegend reservoir, resources — 24.5 x 10⁹ m³, methane — 60%, helium — 0.22%, hitherto it is the biggest gas field in the Polish Lowland;

□    “Paproć” (1982), gas — av. depth 2688 m, the Rotliegend sandstone and the Zechstein Limestone rese-rvoirs, resources — 6 x 10⁹ m³, methane — 50-70%, it depends on a horizon;

□    “Radlin” (1985), gas — depth 3077-3112 m, the Rotliegend sandstone reservoir, resources — 12 x 10⁹ m³, methane — 83%, it is the most rich gas filed on the northern slope of the Wolsztyn Ridge;

□    “Kościan” (1995-1997), gas — depth 2132-2207 m, the Zechstein Limestone reservoir, resources — 10 x 10⁹ m³, methane — 80%. This field started 1975. Then the Kościan-1 borehole documented a gas and the next four drillings were negative. The field was very quickly explo-ited (only 22.4 x 10⁶ m³). In 1995 after new 3D seismic acquisition and the new geological interpretation of this region (Peryt & Dyjaczyński, 1991; Dyjaczyński, 1995; Górski & Trela, 1996, 1997) carbonate buildups were defined. The Kościan-6 borehole discovered a new gas field and documentation of its resources was continued (Dyjaczyński et al, 1997; Radecki, 1997; Radecki & Jastrząb, 2002). Moreover, in the same region with the same methodology, a few other gas fields in the Zechstein Limestone unit were found (“Brońsko”, “Wielichowo”, “Ruchocice”);

□    “Górzyca” (1988), oil and gas — depth 2704 m, the Main Dolomite reservoir, resources — 1.5 x 10⁶1 of oil and 2 x 10⁹ m³ of gas;

□    “Bamówko-Mostno-Buszewo” BMB (1993) (Fig. 17), oil and gas — depth 3100-3200 m, the Main Dolomite reservoir, resources — 20 x 10⁶1 of oil and 15 x 10⁹ m³ of gas (Górski & Trela, 1996, 1997, Mamczur et al, 1997). It

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