The Application and Value of AVO Analysis for De-risking Hydrocarbon Paleocene Prospects in the UK North Sea

摘要

Perhaps over a billion barrels of oil remains trapped within undrilled Tertiary prospects in the North Sea. This study’s primary aim has been to establish the suitability ofAVO analysis for derisking Paleocene prospects. For this, we have carried out a post-mortem analysis of seven wells drilled since 2005 in traps defined by seismic amplitude or possibleAVO anomalies. Only two of these wells encountered hydrocarbons. ConventionalAVO attribute study has been carried out, together with time-frequency spectral analysis. We conclude that the majority of failures relate to poor definition of traps mapped on the basis ofAVO artefacts and spurious amplitudes that could all have been avoided by robustAVO analysis. Three key problems were recognized whilst carrying out the analysis: (1) many 3D seismic datasets were acquired with less than 3 km cable length and are thus not ideal for robustAVO studies; (2) previous data processing flow was not optimized for the purpose ofAVO analysis; and (3) the frequency content of the data in some cases was less than 30 hz, where spectral-related anomalies could be critical in differentiating hydrocarbons from other fluid-related anomalies.