title: Modeling single & multi-phase flows in petroleum reservoirs using comsol multiphysics: ''Pore to field-scale effects''
Creators: name: Πανδης Κωνσταντινος-Διονυσιος
Publisher: name: Technical University of Crete
Year: 2015

description: The numerical modeling of transport processes in stratified petroleum reservoirs is a task of significant importance in the oil production industry as it is involved in technologies related to both reservoir characterization and recovery optimization. Traditional modeling approaches rely on the treatment of the porous material of the reservoir as an effective continuum, where fluxes are related to the gradients of volumed-average scalar properties, such as pressure, concentration, phase saturation and temperature, through macroscopic (cores scale) parameters, such as the medium permeability (or relative permeabilities for multi-phase flows), effective diffusivities etc. Such approaches essentially ignore the accurate description of pore scale phenomena arising at the complicated geometry of the pore scale in favor of reduced computational time for such field scale problems.
Modeling of transport processes at the pore scale is however an indispensable tool for the calculation of macroscopic transport parameters, as an alternative to core and field scale experimental measurements. The objective of this Msc thesis, is thus to offer better physical insight on how pore scale effects such as hydrodynamic dispersion determine the field scale transport properties in such upscaled systems. This will be accomplished using a commercially available generic finite element solver numerical modeling tool; Comsol Multiphysics. The results will be then implemented at realistic reservoir scale systems to study two processes relevant to reservoir characterization and recovery optimization; non-Gaussian hydrodynamic dispersion and water-flooding.
Pore-scale modeling is a first step to study single and multiphase flows and transport in porous media. The hydrodynamic dispersion coefficient is calculated for a single capillary, in order to simulate the phenomenon emanating at the pore scale. Mass transfer in the field scale and therefore in three dimensions is simulated in the second model, in order to extract information about dispersion in three dimensions and about the effects arising in a stratified, anisotropic and heterogeneous geometry, such as those typically encountered in petroleum reservoirs. As a last step, two phase flow is simulated in a three dimensional reservoir focusing primarily on the displacement of the non-wetting (oil) from the wetting phase (water) in the course of a Waterflooding process, used to optimize oil recovery in pressure depleted reservoirs.
The above numerical simulations are performed using a commercially-available software; Comsol Multiphysics. The Comsol multiphysics software utilizes PDEs to model the above physical phenomena. The system of equations, which are implemented in the software, consists of mass balances, partial differential equations that describe the accumulation, transport, injection and production of the phases in the model. In addition, several auxiliary equations apply to the system, coupling the different phases in the system together. This set of equations, PDEs and auxiliary equations, allows for equation manipulation such that the main differences between the formulations are the dependent variables that are solved for.
A comparison with the results of Eclipse simulator, which is widely used in the oil recovery industry, will be also provided in the case of two phase flow in a petroleum reservoir. Finally the aim is to evaluate the possibility of whether Comsol Multiphysics can reproduce the results provided by commercial reservoir simulators such as Eclipse 100.