A GEOCHEMICAL SURVEY OF THE NOTTINGHAMSHIRE OIL-FIELDS AND RELATED SEDIMENTS

The possibility of geochemical prospecting for oil depends upon the escape of hydrocarbons through the ‘cap-rock’ of the reservoir deposits to produce a definitive geochemical anomaly representative of the oil beneath. In view of the very large number of petrographical and structural factors that can interfere with the development of such an anomaly, it is not surprising that geochemical methods of prospecting for oil have not always met with conspicuous success. Geochemical anomalies of various types have been recorded over known oil-fields, but the discovery of identical anomalies in unknown territory has not always coincided with an occurrence of oil beneath. The object of the investigation described in this paper was to initiate similar studies in Great Britain using techniques that had not previously been fully exploited. The oil-fields of Nottinghamshire offer exceptional opportunities for investigating the possibility of the migration of hydrocarbons through a variety of sediments and discontinuous structures. Initially, it was our intention to investigate the following criteria: (i) that hydrocarbons migrate vertically above all types of oil accumulations; ( ii ) that the physico-chemical processes governing the movement of hydrocarbons are not greatly influenced by the petrographical and structural characteristics of sediments; and (iii) that such geochemical concentrations can be identified amidst the organic components of soils and subsoils (the so-called ‘background organic matter’).