The East Irish Sea Basin — from caterpillar to butterfly, a thirty-year metamorphosis

Abstract

In the thirty years since the award of the first licenses, the East Irish Sea Basin has emerged as a significant hydrocarbon province. This paper first lists some of the occasionally almost arbitrary events that led to the first success in the basin, the discovery of the Morecambe Field in 1974. An attempt is made to review progress over those thirty years in certain topics, namely (1) stratigraphy, (2) structure, (3) sedimentology, (4) diagenesis-'the Platy Illite problem' and others, (5) uplift and inversion, (6) hydrocarbon sources and types, (7) East Irish Sea Basin analogues. The paper concludes by summarizing the current state of knowledge. 1995 represented the thirtieth anniversary of the first award of licences in the East Irish Sea Basin (EISB), the twenty-sixth anniversary of the drilling of the first wells and the twenty-first anniversary of the discovery of the South Morecambe Field. It is, perhaps appropriate to look back on some of the crucial events of the last thirty years, and on some of the earlier concepts and interpretations, with a view to seeing how these last have progressed or been found wanting. Undoubtedly, the biggest spur to exploration was the discovery in 1974 by the British Gas Corporation subsidiary HGB Ltd of the South Morecambe Field. How a fledgling organization came to discover this 5 TCF gas accumulation in its first venture, is itself noteworthy. Key events that led to this discovery might be summarized as follows: (1) the wish of the government in power in 1969 to foster a national presence in the exploration of British waters by allowing the then Gas Council to take 100% interests in EISB blocks; (2) the readiness of the Gas Council to exploit this opportunity; (3) the unwillingness of the Council's main North Sea partner to participate in the proposed application, with its offer of a firm well; (4) the unwillingness of other majors to join the application; (5) the informal gift by Gulf in 1973 of the logs of wells 110/8-1 and -2, on the basis of a 'gentleman's agreement' that HGB would likewise make data available from any wells it