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Evaluation of the Unloading Effect Due to Uplift and Erosion on P-Velocity of Siliceous Shale In the Barents Sea
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 80th EAGE Conference and Exhibition 2018, Jun 2018, Volume 2018, p.1 - 5
Abstract
We evaluate an effect of unloading due to uplift and erosion on the P-wave velocity (Vp) of siliceous shale and discuss how important to consider it in hydrocarbon exploration, especially in regions having experienced large amount of erosion in their burial history such as the Barents Sea area. Compilation of well-log data (81 wells) from the Barents Sea area demonstrates that, after uplift and erosion, Vp will not keep the maximum value at the maximum burial depth (MBD) experienced nor decrease with the same amount as its initial loading. It suggests that shale Vp has hysteresis and that it is not negligible.
We start to evaluate the applicability of Bowers’ model to the Barents Sea data by comparing his model with extensive well-log data set. Then, how the hysteresis of shale Vp affects our exploration evaluation will be demonstrated. Later in this paper, we provide a useful formula to estimate maximum burial depth from seismic data (Vp and current depth). Using the formula, we can estimate MBD and net erosion thickness straightforward by the combination of current depth and seismic velocity of a target shale formation, both of which can be obtained from seismic processing and depth converted seismic volume.