Here Dr Alex Edwards et al discuss the presence of Secondary Overpressure Generating Mechanisms in Jurassic Shales, UK-Sector, Central North Sea.  Using a set of techniques such as Vp/Vs, Vp/Rho cross-plotting, they identified the signature for chemical compaction/and unloading in the gasprone Jurassic Kimmeridge Clay, as well as in the associated reservoirs. This analysis provided a set of velocity/effective stress relationships that can be used for pressure prediction, the results of which can be compared with the pressure inferred from a simple loading model, to understand the contribution to present day pore pressure of these additional processes.

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