ParaGeo files [dataset]

The East Coast Basin (ECB) is a complexactive convergent marginof the North Island of New Zealand, where high overpressures in the Cretaceous to Recent stratigraphy have evolved and often near lithostatic pressures can be encountered at shallow burial depths (<300 m). This study investigates the controls on overpressure generation and direct changes in mechanical properties of the sedimentary rocks as a result of rapid burial, uplift, active tectonic compression, and changes in effective stress. A regional investigation, which included analysis of the Cretaceous to Pleistocene tectono-stratigraphy, was combined with 2D and 3D seismics and well-log interpretation to understand the structural, stratigraphic and sedimentation history of the ECB and thus the main factors that could have contributed to overpressure generation and dissipation. 1D hydro-mechanical models, which capture the geological histories, were built for five key wells across the ECB to investigate the overpressure contribution generated by disequilibrium compaction and tectonic compression. Results show that the overpressure registered is significantly driven by tectonic compression as a result of the subduction of the Pacific Plate beneath the Australian Plate from the Pliocene to present-day (~6 Ma). Disequilibrium compaction has played a secondary role in overpressure generation (up to 3 MPa at 2,000 m depth). Tectonic and unloading events (e.g., erosive events) have an impact on the sediment mechanics of low permeability intervals, which are critical factors as these intervals could have changed their properties from elastic to plastic, increasing the risk of failure.