Sequence stratigraphic analysis of North Sea Eocene and Paleocene seismic-reflection profiles and well data provides examples of lowstand, transgressive and highstand systems tracts, including the 'basin-floor thick', 'slope thick' and prograding-wedge facies of the lowstand systems tract. This study was initiated to evaluate the interpretation methodology, refine the biostratigraphic control and test the Vail-Exxon depositional model prior to undertaking a more regional study. The primary data consisted of 4200 km of multifold seismic reflection profiles distributed in a 20 km grid, calibrated using log suites from 45 wells including 37 with biostratigraphic data. Thirty-two micropalaeontologic bioevents from top Cretaceous to top Eocene were evaluated. Twenty-three bioevents were identified as useful chronostratigraphic markers and were used to constrain both well-log and seismic reflection profile correlations. In general, the mapped systems tracts are more spatially separated than suggested by the diagrammatic Vail-Exxon model and require biostratigraphic correlation to confirm temporal relationships. Many of the lowstand systems tracts appear to be line-sourced by several sediment-supply systems. Ten Paleocene and Eocene sequences were recognized in this study, compared to 22 on the Cenozoic cycle chart. The remaining 12 Cenozoic sequences are either absent or are coalescent and below the resolution of this study.

High-resolution biostratigraphic analyses provide calibration of both depositional systems and specific depositional environments. Such studies facilitate prediction of reservoir geometry and the lateral continuity of both reservoir sandstones and sealing mudstones. Data from the offshore Nigeria Oso Field are presented as a case study of one late Miocene deltaic depositional system. Within the Oso Field, marine mudstones are recognized as effective top seals across the entire field in contrast to marginal marine to non-marine mudstones which have more restricted distribution and act as intrafield baffles. Three sequence stratigraphic models have been considered: (1) the first is based on biostratigraphic data integrated with core sedimentology; (2) a second model constructed using core sedimentology; and (3) a third based on interpreted regional seismic reflection profiles and well-log data. Integration of all data shows that the lower Oso Field producing interval is interpreted as a lowstand prograding wedge, and the upper interval as a prograding distal transgressive or alternatively distal highstand system tract.

High resolution biostratigraphic analyses provide calibration of both depositional systems and specific depositional environments. Such studies facilitate prediction of reservoir geometry and the lateral continuity of both reservoir sandstones and sealing shales. Data from the offshore Nigeria Oso Field is presented as a case study of one late Miocene deltaic depositional system. Within the Oso Field, marine shales are recognized as effective topseals across the entire field in contrast to marginal marine to nonmarine shales which have more restricted distribution and act as intrafield baffles. Multiple sequence stratigraphic models have been considered; one model based on regional seismic and well-logs data, one on log-motif and core sedimentology, and one on biostratigraphic data integrated with core sedimentology. The lower Oso Field producing interval is interpreted as a lowstand prograding wedge and the upper interval as a prograding distal transgressive or alternatively distal highstand system tract, based on integrating all these data.