PRODUCING - 33 North German Oil Fields

PRODUCING - 33 North German oil fields. 2.5 NORTH GERMAN OIL FIELDS 2.5.1 General In the North German Basin oil is generally trapped on salt dome structures which have frequently been compared with the fields of the Gulf Coast, Texas and Louisiana, and particularly with the interior salt domes of these states. However, attempts to explore for oil in the North German Basin, by applying Gulf Coast methods, namely, drilling around the edges of the domes near the salt, have not re sulted in outstanding successes. For example, at Nienhagen drilling was started at the edge of the salt because of the presence of oil seeps. Only gradually was exploration extended some distance from these seepages and eventually the best production was developed on a nose about 3,000 meters distant from the salt plug. This characteristic of many of the German salt domes has been attributed to two main periods of uplift separated by an erosion interval—the first uplift during the Jurassic, and the second at the end of the Upper Cretaceous. When the domes first appeared during the Jurassic they were apparently of considerable extent with relatively gentle slopes; a comparatively thin section was involved in the uplift and some faulting occurred. As the salt moved in to form the stock, beds over the salt area, instead of bending, were faulted down. Some of the oil trapped under these conditions was not removed by erosion when the domes were truncated during the Cretaceous. In the next general movement, at the end of the Cretaceous, the salt rose rapidly, affecting relatively small areas but with greater intensity than during the previous uplift. This movement appears to have been too abrupt to in fluence greatly the accumulation of oil, although together with the regional move ments it served to add to the halo of faults and grabens ranging out from the salt core. In such relatively shallow domes oil may be found in about the areas where it was trapped originally; that is, in faults at some distance from the salt core. There are, however, in the North German Basin, domes which have retained their deep seated characteristics acquired in Jurassic time; these structures yield more pro duction than the shallow domes and the productive zone is in closer proximity to the salt. The testing of such deep-seated salt domes appears to form the most promising means of developing large oil production in Germany in the future. How ever, drilling on even the most favorable prospects in the North German Basin repre sents a highly speculative venture, as each dome presents entirely different prob lems not only as to the complexity of the structure but also in the up-dip pinch- out of oil horizons. 2.5.2 Geology Stratlgraphy«- The geologic section from Permian to Pleistocene, inclusive, ig much the same over northwest Germany and is summarized in the stratigraphic sec tion shown on pages 34and 35 , which also shows the producing horizons of various German oil fields. On the map showing the oil regions of Germany (page 26 ) in about the center of the North German Basin there is outlined an area of uplift called the Pompeckj Swell. This uplift evidently lies along a northward continuation of the Hercynian- Bohemian massive of central Germany, It has no surface expression but was a land area from Upper Triassic to Middle Cretaceous (Albian) time. The principal oil producing horizons of Germany—the Wealden, Malm, Dogger, Lias—were, therefore, not deposited on this arch, nor are these horizons known to occur in that part of the basin east of the Pompeckj ridge. They are present in the northwest portion of the basin and in the vicinity of Braunschweig (Brunswick) and Hannover, where this stratigraphic section reaches its maximum development. Structure,- In the northwestern part of the North German Basin there is fold- in* in the hercynian direction, from southeast to northwest, which started at the end of the Jurassic and received an impetus at the end of the Eocene, at the end of the Oligocene at the end of the Miocene and a weak final phase as late as Quater narv These movements are referred to as the Saxonian orogeny. The folding took place between old massives and decreases in intensity from south to north. 34 - PRODUCING Stratigraphic section GENERALIZED STRATIGRAPHIC SECTION OF NORTHWESTERN GERMANY 1934 GOOD PRODUCTION O MINOR PRODUCTION G GOOD SHOW OIL FIELDS OTHER OIL OCCURRENCES GAS ASPHALT PRINCIPAL AGE AND FORMATION LITHOLOGIC CHARACTER (thicknesses are relative only) RECENT SAND AND GRAVEL QUATERNARY BOULDERS, GLACIAL TILl PLIOCENE SAND, CLAY 0'13OO' MIOCENE SAND, CLAY, 15C-95O' LIGNITE OLIGOCENE SAND, CLAY, 800' LIGNITE EOCENE SAND, LIGNITE 160'-330' PALEOCENE MARL, SHALE, 250'-600' CHALK SENONIAN •NOTE 1 500 • 660' EMSCHERIAN 6O0'-9OO' TURONIAN 9S0' CENOMANIAN 200' 5 § HAUTERIVIAN VALENGINIAN SHALE AND SANDSTONE SHALE, SANDSTONE MUNDER MERGEL MARL, GYPSUM CONTINUED ON FOI LOWING PAGE PRODUCING m - 35 Strategraphic section GENERALIZED STRATIGRAPHIC SECTION OF NORTHWESTERN GERMANY (continued) OIL FIELDS OTHER OIL OCCURRENCES GAS ASPHALT S E N T E N N ) N L N N N MIN R MINE N E A F P H RINCIPAL N H K F F E E AGE AND N G R BASI FORMATION LITHOLO GIC CHARACTER E BASI BASI D (VEINS R (thicknes R M BORDE POTAS POTAS H A S SCHOPPENSTED L VORWOHL £es are relative only) THORE SOTTOR HADEMSTOR WIETZESTEINFORD OBER HEID NEUENGAMM NIENHAGENHANIGSE OLHEIM-BERKHOPE VOLKENROD WEFENSLEBE SEHND MANSFEL K HORST-WIPSHAUSE HORDOR | HOPE-LINDWEDE HOHENEGGELSE BENTHEI MUNSTE LIMME DUTC DOLLBERGE DOBRILUG MUNSTE ~ | | | | | | 1 [ 1 | | | | | | 1 | 1 INUMEROU | | 1 | | | |DESDEMON ORNATEN | ~| MACROCEPHALEN • • G ' UPPER SANDSTONE, SHALE R CORNBRASH ' . i'.' , .' .','. ) PARKINSONI G SHALE DOGGE MIDDLE 500'-800 CORONATUS SHALE, LOWER POLYPLOCUS TCi7i — • i SANDSTONE • • 0 0 JURENSIS (continued UPPER POSIDONIEN = = ~—-^^: — C = BITUMINOUS SHALE ' MIDDLE AMALTHEUS S CAPRICORN U SHALE JURASSI LIA 600'-980 LOWER ARIETITES ANGULATUS PSILONOTUS SANDSTONE, 'i SHALE RHAET • • • 0 G ' R — MARL, GIPSKEUPER SANDSTONE, GYPSUM KEUPE 500'-1300 KOHLENKEUPER ^ DOLOMITE, SANDSTONE T 1 1 , ( l 1 - UPPER ' ± LIMESTONE K MIDDLE •M— —'—c ^ DOLOMITE, GYPSUM V KAL 600'-980 LOWER i LIMESTONE MUSCHEL C - MARL, GYPSUM, UPPER -^ ' ROCK SALT TRIASSI BAUSANDSTEIN N ' MIDDLE 5500 - ROGENSTEIN — SANDSTONE, 2300' _ SHALE BUNTSANDSTEI LOWER + v+v+ t ROCK SALT, + 4 POTASH SALT, UPPER r t t <" +- GYPSUM, T G G G ' t- ANHYDRITE, N 1- t I" r f SHALE 4300 - VtV. 660' VtVt ZECHSTEI STINKSCHIEFER g DOLOMITE • G T HAUPTDOLOMIT MIDDLE ANHYORIT ANHYDRITE N / ZECHSTEINKALK \ . yyyyy ' ^ LIMESTONE ^ ^ T ^^ BITUM SHALE \ T LOWER KONGLOMERAT ~— 5 —-^CONGLOMERATE "~ SANDSTONE PERMIA M PORPHYRY S ' ! SANDSTONE 1 PORPHYRY 1600'-3300 SANDSTONE, SHALE ROTLIEGENDE SANDSTONE S S '= COAL, R = SANDSTONE, G G G G ~ SHALE UPPE CARBONIFEROU CARBONIFEROU NOTE 1 SENONIAN PRODUCTION AT WIETZE-STEINFiJRDE IS SECONDARY ACCUMULATION IN BASAL TRANGRESSION SAND NOTE 2 OMITTED IN TABLE IS GOOD OIL SHOW IN ZECHSTEIN SALT ON MAKEL STRUCTURE R94A 36 - PRODUCING Geology The folds developed were not of the continuous undulatory type but are more in the form of horsts and grabens (called fault-folding). Along the edge of the massive, south of the North German Basin, these folds are found in the Harz range and its two branches, the Flechtinger-HOhenzug, parallel to and northeast of the Harz and the Thffringer Wald, parallel to and southwest of the Harz. In these ranges Paleo zoic rocks have been brought to the surface. There are two minor folds running parallel to the Harz flexure affecting the North German Basin, one extending along the Aller River through Celle and Bremen, the other along the lower Elbe River near Hamburg. These trends of folding are indicated in the drawing below. There is also another less pro nounced anticlinal trend affeoting the Sketch Map North German Basin, called the Rhenish NORTHWESTERN GERMANY trend, the direction of which is rough- Showing ly north and south. It is strongly in evidence in a broad zone east of the Known Salt Domes and Rhenish mass of Paleozoic schists and Fold Axes extends far to the north past Hannover and Ltfneburg, into the area of the lower Elbe. In the North German Basin oil is trapped in salt domes and salt anti clines situated along the Hercynian and Rhenish trends. Where these axes in tersect, up-lifts are especially strong and salt stocks are found at the inter sections. The origin of the salt is the rock-salt of the Permian Zechstein formation. Due to the pressure of thousands of feet of overlying sedi ments in the North German Basin the Zechstein salt became plastic and flowed upward along lines of least re sistance. Generally, the salt pierced overlying strata and burst its way up ward sometimes through great -thick nesses of younger beds. However, there are five general types of structures in which the Zechstein salt is found, namely: (1) Sedimentary beds showing the effect of only slight deformation; (2) Stassfurt type salt dome ridge— low broad anticlines with low broad salt core tapering gently to each side and with the overlying sedimentary beds gently arched concordantly with the top of the salt; (3) Asse type salt dome ridge—a narrow, sharp anticlinal ridge with a narrow, steep-sided, sharply up thrust core of salt and overlying sedi mentary beds sharply arched concordantly with the upper surface of the salt; (4) Lower Aller type salt dome ridge—an anticline with a salt core that projects into or through the overlying sedimen- GEOLOGICAL SECT A-B (after Fulda) tary beds and is in diapir relations to t Triasic z Permian them; (5) Hannoverian type salt stock— p Palaeozoic a circular or elliptical dome with a core of salt which has been intruded into or through the overlying sedimentary beds.

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