Nowadays, a large percentage of oil daily production in some Latin American countries comes from heavy oil reservoirs. The oilfield development and reservoir exploitation strategy for this kind of reservoirs must take into account the impact of geomechanical issues on modelling any reservoir production scenario, either for a single well or sector model simulator. The modelling or simulation tools used to represent the performance and behavior of heavy oil reservoirs present some limitations such as they are not fully coupled and they only use a nonlinear elastic constitutive model to represent the mechanical behavior of the reservoir. Both examples show major limitations to figure out a closer analysis to the true behavior of heavy oil reservoirs. The geological formations related with mentioned reservoirs usually present a mechanical behavior similar to materials with very low capacity to support changes in the stress-state and to present permanent and unrecoverable deformations after loading and unloading processes. Therefore, to analyze the behavior of heavy oil reservoir is mandatory to use modelling tools that incorporate a coupled analysis between fluid-flow process and strain-stress using an elasto-plastic constitutive model.
The elasto-plastic constitutive model defines the plastic and elastic phenomenon caused by loading and unloading that occurs in the heavy oil-reservoir. Several research centers have been focused to design experimental tests to learn more thoroughly the results provided by this model, and the results have been satisfactory. However, laboratory tests are not easy to access in most of cases, so it is necessary to have a numerical simulation model that allows knowing the mechanical behavior of the reservoir associated for any production scenario or strategy.
This paper presents the results from a coupled model, which integrates both the geomechanics and fluid-flow equations for a single-well case using different constitutive models. This model could provide an overall result of the mechanical behavior of unconsolidated sand under production of high viscosity oil. The results comparison for the three considered cases, just fluid flow, an elastic lineal behavior of the rock and finally an elasto-plastic behavior, provides a great difference between the stress-state among cases with a dramatic change in the formation permeability, and therefore in the reservoir pressure.
This numerical model is a useful approximation to improve the characterization of heavy oil reservoirs. As a result, heavy oil reservoirs will have a more successful production intervention or recovery process.