DANMARKS GEOLOGISKE UNDERSØGELSE III. RÆKKE . NR. 36 Geological Survey of Denmark . III. Series . No. 36 Deep Tests in Denmark 1935-1959 by Theodor Sorgenfrei and Arne Buch Dansk sammendrag Dybdeboringer i Danmark 1935-1959 With 22 Piates I kommission hos C. A. REITZELS FORLAG (JØRGEN SANDAL) København 1964 PREFACE Work on this report on the first period of oil exploration in Denmark was started in 1959 as requested by Dr. H. ØDUM, Director of the GEOLOGICAL SURVEY OF DENMARK. In that year the DANISH AMERICAN PROSPECTING COM­ PANY relinquished the concession of Denmark and submitted the final portion of exploration data and well sample material to the Geological Survey of Denmark in accordance with the concession. Completion of the report was, however, delayed for various reasons. The main cause was the transfer of the senior author from the Geological Survey to the TECHNICAL UNIVERSITY OF DENMARK in 1961. By forwarding the report the writers want to emphasize its preliminary nature. The large amount of sample material derived from the wells drilled during the exploration programme is under current study at the Geological Survey. A team of geologists of which the writers are members was organized in 1959 for a careful re-study in detail of lithology, biostratigraphy, tectonics, etc. of the deep subsurface of Denmark. The work of this team did already result in new knowledge and concepts, which may alter our ideas of the geology in the future. It might, therefore, have been more sensible to postpone the present report. This was, however, deemed inadvisable because of the need for information on the deep tests drilled in Denmark and the fact that the final monographs may keep the public waiting for a while. Geology is not only taught at the universities, but also at high schools and teachers colleges in our country. Students and teachers have accordingly waited for a report on the geological results of the exploration for many years. The interest of the international public is also of a vivid nature. Denmark is situated in a strategic position from a geologic point of view. It connects the Precambrian basement shield of Fennoscandia with the sedimentary basin of Northern Germany, and it is a link between West and East in Northern Europe. By preparing this report it has been attempted to meet some of the wishes both of Danes and foreigners. Since it was assumed that the interests of the two groups are not identical, the English and Danish texts are somewhat different. An apology to the reader for deficiencies and inconsistencies. The writers are indebted to Mrs. RIGMOR BORG, J. A. TROELS-SMITH, Ph. D., GUNNAR JANSSON, M. SC. and Mr. CHR. WESTERGAARD for substantial aid during the preparation of the plates. Finally the members of the Team on the Subsurface Geology of Denmark are gratefully acknowledged for valuable discussions and contribution of material for publication. December 1963 Theodor Sorgenfrei Arne Buch INSTITUTE FOR APPLIED GEOLOGY GEOLOGICAL SURVEY OF DENMARK TECHNICAL UNIVERSITY OF DENMARK Charlottenlund Lyngby CONTENTS Page Abstract 7 Introduction 9 Brief Outline of the Oil Exploration in Denmark 9 The Background of the Exploration Activity in Denmark 10 Exploratory work 11 A. Gravity Survey 11 B. Seismograph Survey 12 C. Geological Operations 14 Outline of the Pre-Pleistocene Geology of Denmark 18 A. The Sedimentary Basin and its Stratigraphy 18 Pre-Cambrian 18 Cambrian 19 Ordovician-Silurian 19 Pre-Permian of unknown age 19 Lower Permian 19 Upper Permian 20 Triassic 20 Jurassic 20 Cretaceous 21 Tertiary 21 B. The Geological Structure of Denmark 23 1. Regional structure 23 a. The Fennoscandian Border Zone 23 b. The Danish Embayment 23 c. The Ringkobing-Fyn High 23 d. The northern part of the North German Sedimentary Basin 23 2. Local structure 24 a. The Fennoscandian Border Zone 24 b. The Danish Embayment 24 c. The Ringkobing-Fyn High 24 d. The northern part of the North German Sedimentary Basin 24 C. Hydrocarbons 24 The Drilled Sections and their Stratigraphic Subdivision 26 Danish Summary (Dansk Sammendrag) 91 Annex: Information on the species of the fossil fauna (Danish) 103 Foraminifera 103 Graptolithina 130 Pelecypoda 130 Ammonoidea 137 Belemnites 140 Literature 141 Foraminifera 141 Graptolithina, Mollusca 143 Borings 145 Plates 1-22 (13-22 unbound in cover pocket) ABSTRACT The exploration activity which resulted in the 31 deep tests reported on in this paper is briefly outlined in the introductory chapter. Mr. F. RAVLIN initiated exploration by drilling the two wells at Harte. He held the concession covering all of Denmark from 1935 to 1938, when GULF OIL CORPORATION acquired the concession. A large amount of geophysical and geological work was subsequently carried out under the aegis of the GULF OIL CORPORATION, and until 1957 eighteen deep tests were completed. Finally, during the period from 1957 to 1959, when the STANDARD OIL COMPANY OF NEW JERSEY was the concessionaire, seismic work was carried out in selected areas, and 11 deep tests were drilled. Among the geological results the most important one was the proof of a well developed Pre-Upper Cretaceous sedimentary basin in Denmark. The rock column includes Pre-Cambrian, Cambrian, Ordovician, Silurian, Permian, Triassic, Jurassic, and Lower Cretaceous formations. A thick evaporite sequence in the Upper Permian Zechstein is the prerequisite of the salt dome province discovered in North Jutland. Oil shows were encountered in dolomites of the Zechstein in South Jutland, but these petroliferous beds proved unproductive. A short blow out of petroleum gas was, moreover, experienced while drilling in the Suldrup salt dome in North Jutland. It is assumed, that a Zechstein dolomite was the reservoir. An abbreviated well log is given for each of the 31 deep tests. Graphic logs of the wells arranged into simple cross sections are found on plates 18 to 22. Bibliographic references regarding fossil species of importance for biostrati- graphy are given in the Danish annex at the end of the paper. Most of the species concerned are illustrated on plates 1 to 11. INTRODUCTION BRIEF OUTLINE OF THE OIL EXPLORATION IN DENMARK The history of oil exploration in Denmark has partly been dealt with by HILMAR ØDUM (1960) in his paper on the salt exploration. The main events in the history of the prospecting for hydrocarbons in Denmark were otherwise as follows: In January 1935 the Danish Government granted to Mr. FRED RAVLIN, a U.S. citizen, an exclusive right to prospect for all undiscovered minerals in Denmark (except for the Faroe Islands and Greenland). The Danish American Prospecting Co. was subsequently formed by Mr. RAVLIN, and the first two tests for oil and natural gas, Harte No. 1 and No. 2, were drilled in Jutland during the period July 1935 till April 1938. Both holes were dry. Partly before and partly while these drillings were carried out a very limited amount of geophysical work, including magnetometer, gravimeter, and refraction seis­ mograph surveys, was carried out. In August 1938 the Danish American Prospecting Company and the Danish concession was taken over by Gulf Refining Company (Gulf Oil Corporation, Pennsylvania, U.S.A.) Shortly thereafter the Danish American Prospecting Company commenced extensive exploratory activities in Denmark. A detailed gravimeter survey was started in September 1938, seismograph operations were initiated in June 1939, and drilling of stratigraphic tests and structure core holes with a Sullivan rig began in the fall of 1939. Moreover, various geological surveys and studies were in progress. All operations were suspended, when the German army invaded Denmark on April 9, 1940. Early in 1946 operations were resumed. Drilling of structure core holes on gravity features suggesting salt domes was continued with the Sullivan rig. Furthermore an Emsco J-750 rig and a Cardwell model "R"-rig were brought into Denmark. The first deep test with the Emsco rig, Vinding No. 1, was started in July 1947. The Cardwell rig was put in operation on the Suldrup salt dome in September the same year. The rigs are shown on plate 12. The gravity survey was completed in July 1948, and the seismic surveys were continued until October 1953. Drilling activity was going on almost uninterruptedly till October 1953. The Sullivan rig was drilling structure core holes and core holes in the salt domes. 10 Similarly the Cardwell rig was included in both the salt prospecting programme and structure drilling. Moreover, a number of semi deep tests and stratigraphic tests were drilled with the Cardwell rig. Only 5 deep tests were completed with the Emsco rig. The Gassum No. 1 deep test was standing idle from February 1949 to December 1950 during a period of negotiations, when concession matters were discussed with the Danish Government. Drilling with the Cardwell rig was also suspended during this period. Since June 2, 1950, operations were carried out under a new concession signed by King Frederik IX the said date. Due to the discouraging results of the exploration efforts it was decided to suspend field operations on February 1, 1954. Interpretation and compilation work was, however, continued on a small scale. Structure drilling was resumed with a Failing 1200 rig in January 1956. Shortly afterwards the drilling of seismic shot holes was started. On May 13, 1957, Standard Oil of New Jersey took over the Danish American Prospecting Company and resumed operations on a full scale under a new concession from which salt deposits were excluded. Two seismic crews were active from July to December 1957, and one of the crews continued work until December 1958. Eleven wildcats were drilled from December 1957 to May 1959 with an Emsco 800 rig (see plate 12). All wells were, however, dry holes, and the concession was finally given up on June 30, 1959.