--> Paleocene exploration along the UK Atantic Margin

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Paleocene exploration along the UK Atantic Margin


The 1986 Laggan gas discovery together with the 1992 and 1993 Foinaven and Schiehallion oil discoveries, established the west of Shetland Paleocene as a major new petroleum province. Exploration during the following 10 years had only limited success. However, renewed exploration since 2002 has seen 14 Paleocene exploration wells drilled, with 10 encountering notable hydrocarbons.

Since 1972, 79 wells have been specifically positioned on Paleocene prospects that resulted in 23 discoveries. Analysis of the 56 failed Paleocene wells shows that around 80% were drilled on either a poor or invalid trap, with the remaining 20% failing mainly due to either lack of or poor reservoir or poor top or lateral seal. Only 4 exploration wells were exclusively positioned on Paleocene 4-way dip structures, with all of these encountering hydrocarbons.

Fifty-six Paleocene prospects contained a stratigraphic component, with only 18 notable successes, all of which are within the Upper Paleocene Vaila sequence. Ten of the key discoveries are located in the Judd Sub-basin or adjacent Westray Ridge and a further five are located in the Flett Sub-basin.

Many of the wells were positioned on an amplitude or AVO anomaly, of which 18 encountered notable hydrocarbons. Following post-mortem studies, the majority of the failed wells can be shown to have drilled poorly defined amplitude anomalies (various lithologies including igneous), AVO artefacts, or spurious DHIs (which include multiples). For the majority of the failed prospects the amplitude anomaly had no conformance to structure.

In recent years all of the wells positioned on sound AVO anomalies successfully encountered hydrocarbons. Moreover, these wells show both a clear increase in amplitude with offset and a conformance with structure. Certainly, the recent triumphs firmly demonstrate there is potential for maintaining a high success rate in future Paleocene exploration west of Shetland. Equally, the evaluation and use of proven examples like Foinaven, Schiehallion, Laggan, Tormore, Glenlivet and other analogues can add value to future exploration programs.