Geological aspects of the Danish North Sea sector. With a report on the wells Dansk Nordsø E-1, E-2, F-1, G-1, H-1, I-1, J-1 and K-1

This paper presents lithological and chronostratigraphical descriptions of geological sections from the following eight Danish North Sea wells: Dansk Nordsø E-1, E-2, F-1, G-1, H-1, 1-1, J-1, and K-1, in which deposits of Triassic, Jurassic, Cretaceous, Tertiary and Quaternary age were found. The chronostratigraphy of the well sections is mainly a result of micropalaeontological examination of samples.The paper gives additional comments on the structural conditions of the Danish North Sea sector with reference to an outline map, and to a number of cross sections through the southern part of the Danish portion of the Central Graben. Some regional structures are given new names.

Mapping of hydrochemical data by computer at the Geological Survey of Denmark

In the present paper an outline is given of the actual use of computers to represent hydrochemical data at the Geological Survey of Denmark. Special emphasis is directed to the description of the different types of output.

Københavnsområdets geologi især baseret på citybaneundersøgelserne

The lithostratigraphy of the Maastrichtian, Danian and Selandian deposits of Copenhagen is described and related to a biostratigraphical zonation based on foraminifera. The Quaternary deposits are briefly mentioned. The København Limestone Formation is formally introduced. The Lellinge Greensand Formation is emended and a reference section in Copenhagen is defined. The structures of the area are discussed on the basis of detailed subsurface mapping. The geology of the area is finally described in detail.

Geology of the Dan field and the Danish North Sea

The Dan field was discovered in 1971 by the Dansk Undergrunds Consortium's fifteenth offshore wildcat, which encountered oil and gas in Maestrichtian and Danian chalk at the subsea depth of 5790-6565 feet. Production of some 800 BOPD from each of five wells began in July 1972.The field lies on the eastern flank of the North Sea Tertiary basin and near the axis of the Central Graben, a deep trough filled with a thick sequence of Permian to Cretaceous sediments. Upper Cretaceous-Danian chalk at the top of the sequence provides the reservoir for several further hydrocarbon accumulations in offshore Denmark. Geochemical studies indicate that deeper Upper Jurassic marine shales are the probable source beds for these accumulations.The Dan field is a halokinetically induced domal anticline. The chalk reservoir has an average porosity and permeability of 28% and 0.5 millidarcy, respectively. The solution GOR is 600 cu. ft./bbl and the crude oil is 30° API with low sulphur content (0.29%).

Some geological results from the first five Danish exploration wells in the North Sea. Dansk Nordsø A-1, A-2, B-1, C-1, and D-1

After an introducing survey of the exploration for hydrocarbons on the Danish continental shelf during the period from 1963 to 1968 a lithological and chronostratigraphical description of the first five exploration wells is given. The results are preliminary and they are based on investigations carried out by the staff of the Department of Subsurface Geology at the Geological Survey of Denmark.Deposits of Permian, Triassic, Jurassic, Cretaceous, Tertiary and Quaternary age are proved to occur in the borings. Stratigraphical investigations of the very thick Tertiary sequence in the central part of the North Sea show, that the main part of the sedimentation took place during the younger Miocene (Upper Miocene).

Dybdeboringen Nøvling nr. 1 i Midtjylland

The book contains geological and geophysical reports on the deep test well Nøvling No. 1. This boring was made by "Dansk Undergrunds Consortium" in Central Jutland 1966.Beds of Pleistocene, Tertiary, Upper Cretaceous, Lower Cretaceous, Jurassic, Triassic, Upper Permian and Upper Silurian age were penetrated. The final depth of the boring was 12342' or 3762 m below the Kelly Bushing.The book includes 17 articles written by 12 authors, all of whom are (or were) from the staff of the Pre-Quaternary Department (= Dep. of Subsurface Geology) of the Geological Survey of Denmark. In an introductory article a review is given of the geological and structural aspects of the boring together with an outline of the technical and administrative data.

Cyclogram technique for geological mapping of borehole data

This paper describes the principles of a new method for three-dimensional mapping of geological basic data from boreholes and wells. This method is developed by the Geological Survey of Denmark and uses cyclograms for graphical illustration of borehole records in stead of bar diagrams.The procedure and the technical tools for construction of the cyclogram and the map are described. Advantages and disadvantages of the method compared with other mapping methods are discussed.For illustration of the method a map of about 350 sq.km with more than 500 well-record-cyclograms is enclosed.

Dybdeboringen Rønde nr. 1 på Djursland

A report is given on the geological investigations carried out by geologists from the Pre-Quaternary Department (= Dep. for Subsurface Geology) of the Geological Survey of Denmark on occasion of the oil test well "Rønde No. l". This boring was made by "Dansk Undergrunds Consortium" in the peninsula of Djursland, Denmark, during the period from Oct. 1965 to July 1966.Beds of Pleistocene, Tertiary, Upper Cretaceous, Lower Cretaceous, Jurassic, Triassic, and Upper Silurian age were penetrated, when the operations stopped at a depth of 17389' or 5300 m below Kelly Bushing.Nine authors describe in a total of 15 articles the lithology and biostratigraphy of the drilled section. An introductory article presents an outline of the complete geological profile and summarizes the technical and administrative data of the well.

Geologi og Vandboring. 2.udgave

This book is intended as a simple geologic hand-book for well drillers and water supply engineers working in Denmark.The principles of physical geology are briefly treated in chapter I as an introduction to the geology of waterbearing beds in the subsoil of Denmark. The normal hydrologic cycle at the surface of the earth has been emphasized, illustrating the action of water upon landscape and subsurface. Glacial erosion and sedimentation are discussed rather comprehensively in order to make the user of the book familiar with the variability of the Quaternary deposits of the country. The work of the sea has also been treated, and the modes of marine erosion and sedimentation are outlined. The comparison of fluviatile, marine, and glacial deposits should draw attention to significant features and differences in rock composition and texture, and thus enable the well driller or engineer to determine the common rock types met with in water well drilling in this country. Weathering, disintegration, and crustal processes are only touched upon.In chapter II, which deals with the historical geology, the glacial drift that veils the bedrock formation over great parts of the country is described first, since a non-geologist should understand the nature of the Pleistocene glacial deposits before he is confronted with the less accessible formations of the subsurface. Regarding the pre-Pleistocene formation the description has been divided into two sections, the first one treating the areas W of Øresund, and the second one dealing with the island of Bornholm. The formations are described in their stratigraphic order of succession, and the sequence of sediments is described in rather great detail, with emphasis on the formations that provide aquifers of practical importance.Chapter III deals with the selection of drilling sites in general on the basis of geologic and hydrologic viewpoints, while chapter IV is a case history of the search for new groundwater supply areas for the waterworks of the township of Randers in Jutland. It includes an outline of existing major pumping stations in the town area and its surroundings, and a discussion of the geologic and hydrologic setting of the region. The plans for the test wells, which were proposed on the basis of geo-hydrologic considerations, are presented and compared with the results obtained through subsequent drilling.Waterbearing gravels and sands in the Pleistocene and waterbearing Upper Cretaceous limestone were tested. It appeared that rather complicated hydrologic situations are found in the surveyed area. One of the most cumbersome problems from a technical point of view is the occurrence of salt water in the aquifers. The salt water is assumed to be derived from deep-lying pre-Cretaceous formations from which it may ascend into the freshwater zones through structural dislocations due to a deficit in hydrostatic pressure in the more shallow aquifers. A natural drainage of the Gudenaa valley through highly permeable gravel beds near the surface may be responsible for the lower hydrostatic pressure in these aquifers. The last part of the book consists of a compilation of significant well logs, a list of geologic terms, stratigraphic tables, a geologic map of the pre-Pleistocene surface, and two cross sections through important wells.

Nye metoder for prøvepumpning af boringer og grundvandsreservoirer

The purpose of this paper is to introduce the practical application of selected quantitative and analytical methods for testing wells and evaluation of aquifers to engineers and geologists within the field of groundwater hydrology in the Nordic countries. This abstract, a list of symbols and units and text of figures and tables in English may possibly provide understanding of the used formulas and methods for readers not familiar with Danish.The increasing demand for ground water and the need for optimal utilization of aquifers accelerate the use of quantitative methods for predictions of available quantities of ground water and aquifer response on withdrawal.The first part of this paper gives a short introduction into the developed theory for analysing drawdown data from pumping tests and a number of selected formulas in their developed form for determining the hydraulic properties of wells (B, C and n), aquifers, (T and S) and confining bed (P'). Selected hydrogeological terms are defined. The procedure of pumping and the frequency of waterlevel observations in space and time is briefly mentioned both for step-drawdown test and pumping test with constant capacity.Formulas for adjustments of drawdown- and recovery data for barometric efficiency and decrease of saturated thickness are described. Examples of logarithmic and semilogarithmic plots of data are given together with type curves for leaky artesian and watertable conditions.Principles and formulas for prediction of the future drawdown in pumped wells and aquifers are outlined.The second part of the paper gives the practical application of the selected analytical methods and formulas. Illustrative examples with actual field data collected by the Hydrogeological Department, Geological Survey of Denmark, are presented for each method discussed. Basic data as well drawdown as recovery from 4 pumping tests and their numerical and graphical analysis a represented in 27 figures and 16 tables.