ИСТИНА

It is known that understanding of long-term hydrocarbon recovery or CO2 storage problems depend on proper addressing the physical coupling between the fluid flow and mechanical deformation. The success of geo-energy applications such as hydraulic fracturing, wellbore stability, and geological storage of CO2 is directly connected to the comprehensive formulation of appropriate rock rheology. Effective viscosity is an important parameter that allows to couple fluid flow and deformation processes occurring in the Earth. However, this parameter is rarely measured in the laboratories as it is a challenging task. Moreover, few existing measurements were made in the compaction regime and make no reckoning of (de)compaction.However, (de)compaction may affect fluid flow distribution in a porous medium and create highly porous channels such as chimneys observed in the subsea reservoirs and caprocks. Results of multistage laboratory creep and relaxation experiments that were conducted on different materials including artificial specimens, limestones, heterogeneous shales with sandstone inclusions, and pure sandstones and shales are presented in this study. Both compaction and (de)compaction regimes were considered. We studied the influence of historical changes in the thermal regime during the glaciation and deglaciation cycles, water saturation, preliminary damage of the samples on their viscous behavior. Effective viscosity was calculated for all samples. Experimental curves are explained using the theoretical model for Visco-elasto-plastic (de)compaction of porous rocks.