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IGC (International Geo Consultants BV), Kapelstraat 5B, 2161 HD Lisse, The Netherlands
1 Torenwacht 5, 2353DB Leiderdorp, The Netherlands
2 Javastraat 178HS, 10965CN Amsterdam, The Netherlands
High-resolution sequence stratigraphy analysis is based on the integration of third-order sequence analysis and high-frequency (Milankovitch) cyclicity analysis. Sliding window spectral analysis of wireline logs reveals wavelength changes of the high-frequency cycles along the bore hole. The abrupt wavelength change, shown as the break of the sliding window spectrum bands, indicates a stratigraphic discontinuity. The gradual wavelength change, detected by the gradual shift of the spectrum bands, reflects a gradual change in the rate of net sediment accumulation. These cyclicity patterns reflect the thickness variations of preserved depositional cycles, controlled by basin subsidence, eustatic sea-level/base-level fluctuations, and sediment supply. Observations from the subsurface of the southern North Sea indicate that the breaks of spectrum bands as well as the trend of spectrum band shift can be correlated between wells to help detailed sequence correlation. Cyclicity analysis of the synthetic logs generated from a two-dimensional sequence stratigraphic modelling confirms the lateral correlatability of the cyclicity pattern between wells. Integration of cyclicity analysis with traditional methods will help accurate and reliable sequence stratigraphic correlations in various settings, including biostratigraphically barren strata, thick intervals of fine-grained or coarse-grained sediments, and chalk sections. Such correlations are essential for the establishment of a proper geological model in the hydrocarbon exploration, development and production.
