A Flow and Transport Model in Porous Media for Microbial EOR Studies at Core Scale

The oil fields at their initial operation stage produce using basically its natural energy which is known as a primary recovery. As the reservoir loses energy in order to maintain the pressure it requires the injection of gas or water, which is called a secondary recovery. When the secondary recovery process becomes ineffective it is necessary to apply a more sophisticated approach such as steam injection, chemicals, etc. These are known as enhanced oil recovery methods. Some important oil fields in Mexico are entering the third stage. For the optimal design of oil recovery methods it is required to perform a variety of laboratory tests under controlled conditions to model the fundamental recovery mechanisms for a given recovery method in a specific reservoir. However, the laboratory tests commonly have a number of drawbacks, which include among others that they are very sophisticated, time consuming, expensive and always not enough to cover the whole range of field conditions involved. A proper modeling of the laboratory tests would be decisive in the interpretation, analysis and understanding of recovery mechanisms as well as in obtaining the relevant parameters for the subsequent implementation of recovery processes at the well and the reservoir scale. In this work we present a flow and transport model which was implemented using the finite element method to simulate, analyze and interpret MEOR processes at core scale under laboratory conditions. The flow model is biphasic and is based on the oil phase pressure and total velocity formulation given by Chen Z. et al. 2006, in which the capillary pressure, relative permeabilities, the effects of gravity and the dynamic porosity and permeability modification due to the clogging-declogging phenomena (adsorption-desorption of microorganisms) are taken in account. Whereas, the transport model consists of two phases (water-biofilm) and three components (microorganisms, nutrients and bioproducts). The transport model includes physical-chemical-biological phenomena such as advection, diffusion, dispersion, adsorption-desorption, growth and decay of microorganisms. Adsorption of nutrients is implemented through a linear adsorption isotherm. The effects of the bioproducts on the residual oil saturation are also included. From the methodological point of view, each stage of model development (conceptual, mathematical, numerical and computational) is described. Finally, the resulting coupled flow and transport model is numerically validated in a case study of oil displacement by the injection of water follows by the injection of water with microorganisms and nutrients. The oil recovery evaluation considering different scenarios is shown.