Introduction

Downloaded from http://sp.lyellcollection.org/ by guest on October 2, 2021 Introduction Although the search for oil and gas in Europe, early as 1546 (Kent 1980). In Britain, seepage particularly in the North Sea, has been very oil was being used for medical purposes during successful, it has become progressively more the seventeenth century (Lees & Cox 1937). difficult and costly in recent years. The need Oil sands were mined for oil recovery during for continuing exploration success in finding the mid-1700s in the Pechelbronn area of the accumulations of hydrocarbons has created a Rhine graben and it is estimated that in the climate which favours the use of modern period up to 1860, more than 4000 metric tons scientific and technological methods and tech- of oil had been produced (Kent 1980). Britain, niques. Amongst these is petroleum geochemis- during the 1850s, saw the first use of seepage try. Applications of petroleum geochemistry oil recovered from a Derbyshire, U.K. coal (integrated with petroleum geology) in petro- mine. The first successful reported oil well was leum exploration has drastically changed in drilled in 1859 and discovered in the Wietze oil recent years from a post-mortem science to a field north of Hanover in northern Germany widely accepted exploration predictive tool. (Zeigler 1980). In 1918, following from the The oil industry, in its search for hydro- problems of importing crude oil during the carbons, has in recent years extended its 19 i 4" 18 First World War, the British Govern- exploration activity to take in the entire ment commissioned the first phase of U.K. continent of Europe, both on- and offshore deep exploration. The exploration programme basins. In addition to proving substantial oil and was based on analogy with the Pennsylvanian gas reserves, these studies have provided a vast Oil Fields and the objective was directed at amount of new geological and geochemical Carboniferous limestone accumulations in the information from many different areas of Southern Pennines and Scotland. A small oil Europe. These advances and applications are field was discovered at Hardstoft near reflected in this present volume. The pro- Chesterfield in 1922 and it was still producing ceedings of Petroleum Geochemistry and oil on a very small scale over fifty years later. Exploration of Europe contains papers by Exploration incentives lapsed during the 1920s experts in geology, geochemistry, sedimen- and the second phase of deep exploration did tology, data analysis, petroleum exploration not commence until the early 1930s when the and U.K. government policy that were anticlines in the Mesozoic basin of southern presented at an International Conference held England became the exploration targets. This within the British Isles Geological Congress at search for oil in southern England was the University of Glasgow in September 1982. encouraged by the occurrence of outcropping oil sands of Lower Cretaceous and Jurassic age (Lees & Tait 1946), together with probable Jurassic-aged source rocks at various locations Brief history of European petroleum from the Weald to Dorest (Gallois 1976; exploration Douglas & Williams 1981). Following from the small oil discovery at Hardstoft, exploration Exploration ofoil and gas has a long and varied activity later transferred back to the U.K. history in Europe, but it is only during the last East Midlands in the hope of finding hydro- few decades that geological understanding of carbon discoveries beneath unconformable North-west Europe and its extensive continental Mesozoic rocks (Kent 1980). The East shelves has been more fully understood. Since Midland operations met with mixed success and the late 1950s geological understanding of the the first commercial field was found at Eakring, North-west Europe offshore area has advanced Nottinghamshire in 1939, followed soon after- significantly mainly due to exploration and wards by three other discoveries. development activities by the oil and gas Exploration and some small commercial industry. production has continued onshore U.K. in the The oil industry has a long exploration Carboniferous (Southern Scotland; NW history in onshore parts of Europe. For England and East Midland), Permian (Eastern example, in North-west Germany, natural England), Triassic (Western England) and petroleum found at Hanover, Lower Saxony, Jurassic (Southern England) Formations. was already used for lubrication and lighting as During the late 1950s and early 1960s BP ix Downloaded from http://sp.lyellcollection.org/ by guest on October 2, 2021 x Introduction drilled several wells in the Wessex Basin Dor- Extensive exploration for and development set U.K. and commercial oil was found in of oil and gas fields has provided a wealth of fractured Cornbrash in Kimmeridge No. 1 new data and during the last decade the geo- (1959) and in a thin fractured Inferior Ooolite logical understanding of Europe, particularly in Wareham No. 1 Well (1964). Further NW Europe, and its extensive continental evaluation of the Wessex Basin suggested that shelves has been more fully understood, mainly the Bridport Sands were probably a better due to the exploration and development reservoir target than the fractured poor activities by the oil and gas industry. The hydro- reservoir rocks believed to be producing in the carbon potential of the various regions of Kimmeridge No. 1 and Wareham No. 1 Wells Europe is by no means uniform and oil and gas (Colter & Harvard 1981). Wytch Farm No. 1 accumulations have been encountered in sedi- Well was spudded in 1973 and discovered light ments ranging in age from Pre-cambrian to oil in the Bridport sands. Subsequent ex- Tertiary. Hydrocarbon accumulations can be ploration and appraisal of the Wytch Farm correlated to specify depositional cycles and Field (Colter & Harvard 1981) has proved the distinct mega-tectonic units (Ziegler 1980, largest known onshore U.K. oil field with light 1981). A number of hydrocarbon provinces oil accumulation in both Bridport and Bunter have been defined based upon the age of their sand reservoirs. major hydrocarbon source rocks and their However, it was not until the discovery of principal reservoir formations, the type of the vast natural gas field at Groningen in the reservoir trap and also the regional oil and gas Netherlands in 1959, that extensive offshore assessment. Reviews of the evolution of major exploration activities commenced. After the oil and gas plays in Europe are given by Kent Second World War, Shell-Esso carried out (1975a, 1975b, 1980), Ziegler (1980, 1981), exploration over large areas of the Netherlands Burollett (1980), Naylor & Mounteney (1982) and drilled several tests in the Groningen region and Pergrum et al. (1982). Specific and in the northern part of the country. In 1959, detailed studies of regional geology and the Slochteren No. 1 Well was drilled through selected oil and gas fields are presented in two the Zechstein Formation and discovered that excellent Conference Volumes Petroleum the underlying basal Permian (Rotliegendes) Geology of the Continental Shelf of North- Sands were hundreds of feet thick and later West Europe (Eds. A. W. Woodland 1975 and shown to be more than 20 miles across, which L. V. Illing & G. D. Hobson 1981). A useful was entirely gas-bearing and very porous. This reference Geological Atlas of Western and unexpected discovery of recoverable gas rentral Europe, edited by P. A. Ziegler (1982) (5.69 x 10 TM m 3) made the field one of the has recently been published. Annual reviews of largest ever found. In addition to Groningen's European petroleum exploration activity are economic importance, the discovery also published in AAPG World Review (see Kat provided a new scale of reference for potential 1980, 1981). NW Europe offshore discoveries. Exploration- ists now begin to anticipate the possibility of large hydrocarbon accumulations rather than Development of petroleum geochemistry reservoirs measured in only tens of feet vertical thickness and acres in extent. The science of petroleum geochemistry is the Just over 18 years ago, in 1965, the first gas application of chemical principles to the study discovery in U.K. waters was made by BP at the of the origin, generation, migration, accumula- West Sole Field in the Southern North Sea tion and alteration of petroleum, and the use of Basin. This was followed immediately by the this knowledge in exploration and recovery of gas discovery of the Viking Field and, in rapid oil and gas (Hunt 1979). Although the concept succession by discovery of the Leman Bank, of petroleum originating from organic-rich Indefatigable and Hewett Fields in 1966. The shales and migrating into sands was first major turning point in the exploration for oil in observed by geologists in the late 1800s, these offshore NW Europe was the discovery of the early theories about the controlling principle of giant Ekofisk Field in the Norwegian sector of petroleum occurrences were often limited in the North Sea in December 1969. Following concept in that they mainly addressed the this major oil discovery, the North Sea has question of 'where' accumulations were located. proved to be one of the best areas for It has become clear during the last twenty petroleum exploration anywhere in the world years, that to be able to better answer the and a number of large oil fields have been question 'where', it is usually necessary to discovered. evaluate 'why, when and how much' petroleum Downloaded from http://sp.lyellcollection.org/ by guest on October 2, 2021 Introduction xi was present in a basin and to understand and aware of the wide scope of different modern establish the generation, migration and geochemical analytical techniques and methods accumulation processes. This understanding is applicable to assist in petroleum exploration at essential if the oil industry is to improve its different phases from the initial frontier basin petroleum exploration success ratio. study through many different topics even to a Although hypotheses are periodically put better understanding of the origin and proper- forward for a non-biological, earth-mantle ties of reservoired heavy crude oil.

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