Abstract
Thermal recovery processes in heavy oil reservoirs have become an efficient technique for the exploitation of the viscous oil that is trapped in the porous space. The heat reduces the oil viscosity and thus allows it to flow from the formation to the well. In recent years, there have been technological advances that have permitted such operations to become safe and profitable. Having a right understanding of what happens to the reservoir and the surrounding formations during thermal recovery has become a topic of interest to reduce the environmental impact of these operations and to generate models that predict production and recovery factor accurately and reliably.
Understanding the geomechanical behavior of this type of formations under different scenarios of stress and temperature is essential to model this kind of operations due to possible scenarios during thermal recovery. Confining condiciton is related to the depth of the reservoir and tectonic activity in the area. Heavy oil reservoirs are mainly located at detph less than 3000 feet according to Shafiei et. al (2013) [1]. This usually makes the reservoir formations to be unconsolidated or poorly consolidated, this kind of formations show elastoplastic behavior where stress-strain relationship plays an essential role in the production/injection process.
Samples from an outcrop of an oilsand formation located in Eastern Cordillera of Colombia were collected to performe triaxial tests at high temperature conditions. Picacho formation presents a high content of fines as other important heavy oil formations in Colombia, where thermal recovery has been considered. Fines content is crucial in the understanding of the material behavior due to particular silt and clay behavior such as thermal consolidation and mineralogic change caused by the temperature increment.
During heating, different parameters were measured in order to understand what occurs to the porous medium while it is subjected to changes of temperature. The measurements include pore volume, total volume and permeability at different stages during the heating process. The experiments were perfomed at different conditions of effective confining stress (mainting pore pressure constant). The results show a significant dependence of the petophysical properties such us permeability and porosity to the confining stress at which the porous medium is subjected.
