Publikationsdatum:
2020-07-20
Beschreibung:
Before making a critical evaluation of the crude oil and natural gas prospects for the years to the end of the century, it is necessary to review the geology and structure of the three German hydrocarbon-producing provinces. Furthermore, past exploration, production and reserves should be discussed.
The three hydrocarbon-producing provinces are: the NW German Basin, the Upper Rhine Graben and the Molasse Basin, which together make up about 41% of West German territory (Fig. 1).
The NW German Basin contains a sedimentary sequence over 8,000 m thick ranging in age from Permian to Quaternary. Gas and oil, the two natural hydrocarbons, are generally confined to separate lower and higher stratigraphic levels respectively (Fig. 2). The NW German Basin is the most important prospective area in West Germany. It extends into the North Sea.
The tectonic rift feature of the Upper Rhine Graben originated in the Eocene. The Tertiary fill is over 4,000 m thick. Oil is found mainly in Mesozoic, Eocene and Oligocene rocks; the Miocene and Pliocene reservoir rocks contain natural gas almost exclusively (Fig. 3).
The Molasse Basin is part of the foredeep north of the Alpine and Carpathian mountain ranges. The basin is filled with Upper Eocene to Pliocene and Quaternary sediments which, near the Alpine nappes, reach a thickness of over 5,000m (Fig. 4).
During this century there were peaks in annual oil-production in 1910, 1940 and 1968 (see Fig. 5). The 1910 peak was the result of drilling activity in the Wietze oilfield. During the period 1934–1945, government financial aid was made available for drilling exploration wells. The success of this collaboration is demonstrated by the oil output in 1940 of 1 × 106 t. After World War II, many different types of oil-bearing structure were found, particularly by reflection seismic techniques in conjunction with detailed stratigraphical and palaeogeographical investigations. The success achieved can be seen by the peak of 8 × 106 t oil production for 1968 (Fig. 5) and in the growth of oil reserves (Fig. 7). Intensive exploration also enabled many new gasfields to be developed, especially in the deeper horizons of the NW German Basin. In 1971, estimated gas reserves reached 360 × 109 m3 (Fig. 11), and annual gas production in 1979 was 20.7 × 109 m3 (731 Bcf) (Fig. 9).
There is, no doubt, still scope for the discovery and exploitation of oil and gas in Germany, especially in the NW German Basin where the best prospects for the future lie. This is borne out by two recent offshore oil discoveries and also by the successful application of enhanced recovery methods in the oilfields. The chances of finding more gas at the lower stratigraphic levels are promising now that gas has been discovered in the deeper parts of the Permian basin. The results of massive-hydraulic-fracturing tests in low-permeability pay-horizons are also encouraging. The deeper parts of oil- and gas-producing basins contain interesting prospects and have yet to be tested by ultra-deep wells.
Provided that the economic climate remains favourable, there should be no difficulty in finding and supplying German oil and gas in the future. Geologically and technically possible reserves should be converted into proven and/or probable reserves. German crude oil will be available for several years beyond the year 2000, and German natural gas for a far longer time. A production rate of 19 to 20 × 109 m3 of gas per annum is feasible over the next twenty years, and oil production will probably not sink below 3 × 106 t/a in this period.
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