02004nab a2200193 4500 20260520001839.0 260224s2010 xxu Viscous creep in room-dried unconsolidated Gulf of Mexico shale (II) Development of a viscoplasticity model mayo 2010 03/08/2010 ; 02/08/2010 6 p. ; 50-55 Transcripción del resumen del autor. Laboratory creep experiments show that compaction of dry Gulf of Mexico shale is a permanent irrecoverable process associated with viscoplastic deformation. In order to find a relatively simple model that can describe such viscoplastic behavior of the dry frame of the shale, we combined the Perzyna viscoplasticity constitutive law with a modified Cambridge clay plastic yield model. The constitutive equation for this model is a power-law function that relates strain rate to the ratio of dynamic and static yield surfaces defined by the modified Cam-clay model. By incorporating the effect of strain hardening on the static yield pressure, we derived an equation relating volumetric creep strain at a constant hydrostatic pressure level to the logarithm of time, which is in good agreement with experimental results. We determined the model parameters by fitting experimental data of creep strain as a function of time. The determined parameters indicate that the yield stress of the hydrostatically loaded shale increases by 6–7% as strain rate rises by an order of magnitude. This demonstrates that the laboratory-based prediction of yield stress (as well as porosity) may be significantly overestimated. Thus, strain-rate calibration is required for weak shales such as those studied here to appropriately estimate physical properties under in situ conditions. 1-2 Journal of Petroleum Science & Engineering 72 ARTICULO Chang, Chandong 42910 Zoback, Mark D. 21228 175667 175667 0 0 0 0 243486 BAAB BAAB 2026-03-05 200047563 0 200047563 2026-03-05 18:56:00 2026-03-05 ARTICULO