Abstract

ALZATE-ESPINOSA, Guillermo et al. Permeability and porosity changes in unconsolidated porous media due to variations of confining stress and temperature - An experimental study. Bol. cienc. tierra [online]. 2017, n.42, pp.64-72. ISSN 0120-3630.  https://doi.org/10.15446/rbct.n42.65497.

Thermal recovery processes are an efficient and commonly accepted technique for the exploitation of heavy oil reservoirs. The increase in the temperature of the porous medium because of steam injection in a thermal recovery processes, significantly reduces the oil viscosity and makes possible its flow to the producing wells. In recent years, there have been technological advances that have allowed such operations to be monitored achieving more profitable and safe process from the perspective of the integrity of the surface flow system. The assurance of the formation flow capacity as well as the mechanical integrity of the production and overlying formations with pressure and temperature changes caused by the steam injection process is a subject of current validity, given their implications economic and environmental impacts, especially for heavy oil reservoirs at shallow depths. Therefore, to ensure a correct understanding of what happens to reservoir and overlying formations during the thermal recovery process has become an issue of interest in reducing the environmental impact of these operations and generating models that predict production and the recovery with accuracy and reliability.

Experimental evidence suggests that the productivity of the wells and the flow capacity of the reservoir affected by thermal recovery processes depend not only on the temperature effect on the heavy oil viscosity but also on the effect of temperature on both petrophysical and mechanical properties of the porous medium. Therefore, the understanding of the geomechanical and petrophysical behavior of the geological formations under different stress and temperature scenarios is fundamental to model the different processes within the reservoir during the thermal recovery, and in particular those that determine the productivity of the wells and the recovery factor of the process.

The paper presents laboratory results about the porosity and permeability behavior with temperature and confinement stress for a non - consolidated porous medium. The evaluation makes use of reconstituted cores made from unconsolidated outcrops completely saturated with heavy oil. At each confinement stress condition, pore volume, total volume and permeability of the core are recorded at different heating stages. The results show a significant dependence of the permeability and porosity with the confinement stress. The greater the effective confinement stress, the greater the reduction of porosity and permeability as temperature increases. At low confinement stress, the tendency is maintained for permeability but not for the porosity of the porous medium.

Keywords : Thermal recovery; thermo-mechanical effect; permeability; porosity; heavy oil..

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