![]() ![]() Force chains arch around the region that undergoes grain dissolution interparticle contact forces are low within the contracting zone, yet are sufficient to provide transverse support to the major force chains. Local arches form when the dissolving inclusion size is similar to the grain size however, granular chains buckle and grains flow to refill voids when dissolving inclusions are larger than the length scale of force chains (about 6-to-10 grain diameters). This study explores localized granular dissolution in sediments under constant vertical stress and zero lateral boundaries using 2D and 3D discrete element simulations to gather macro-scale and particle-scale information during dissolution. ![]() Mineral dissolution and subsurface volume contraction can result from various natural and engineered subsurface processes. This work thus demonstrates how carbonate pore morphology changes with depth (higher effective stresses are encountered deeper in the reservoir) or during production (with hydrocarbon depletion the effective stress increases). The vuggy carbonate has bigger porosity variation than fractured carbonate to the mechanical loading‐unloading cycle. Clearly, the changes in pore morphology were more significant in the fractured carbonate (including extension, connection, and disconnection of fractures) during both loading and unloading, while the vuggy carbonate experienced irreversible structural damage. ![]() For fractured carbonate, the unrecovered porosity can be linked to similar reduction of the surface area and the average aperture of the fracture. This was mainly because of the stress effect on large pore space (i.e., fractures and vugs). ![]() The results showed that after loading, porosity decreased exponentially, followed by an increase during unloading where it did not recover to its initial value. However, there is a serious lack of data with regard to how precisely the pore morphology changes as a function of effective stress we thus carried out in situ loading‐unloading experiments (up to 20 MPa effective stress) where two carbonate samples (fractured and vuggy) were examined with X‐ray computed tomography at high resolution in 3‐D. The associated pore structure-which is of key importance in terms of hydrocarbon production and fluid flow-varies with effective stress. This study shows the advantage of employing speleoseismology in moderate seismic regions, where earthquake effects are rarely preserved in the geological record.įractures, vugs, and pores constitute the main pore space in carbonate reservoirs. Niedźwiedzia Cave shielded environmental earthquake effects from erosion. Although there are sparse historical data that would allow estimating linked seismic hazards, the <8 km distance between the cave and faults should suffice to destroy the speleothems. The other plausible seismic sources are faults in the Upper Nysa Kłodzka Graben located to the east and the Trzebieszowice‐Biela Fault. Located 6, the Sudetic Marginal Fault can produce peak ground acceleration values high enough to break speleothems. We applied ground motion models to determine the probable seismic source size, which is most likely the Sudetic Marginal Fault ‐ one of the most pronounced tectonic structures in Central Europe. Although we cannot unambiguously exclude other agents (frost or gravity collapses), the most likely trigger of damage in the cave was an earthquake, which is supported by timing (the damage occurred independently from climatic conditions in cold and warm periods) and deformation style (damage to the ceiling and walls as well as the passage floor). Events 1, 3 and 4 are robustly constrained, and events 2 and 5 are less certain. Multiphase speleothem damage and passage collapse in Niedźwiedzia Cave (NE Bohemian Massif, Poland) were dated with U‐series methods, revealing five events: (1) 320‐306 ka, (2) 253‐236 ka, (3) 162‐158 ka, (4) 132‐135 ka, and (5) >21 ka. ![]()
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