Nanotechnology-Based Micromodels and New Image Analysis to Study Transport in Porous Media
Authors: Javadpour F. , Fisher D. 
Published: March 2010

Abstract
Micromodels have been widely used to study transport in porous media in past decades. Fabrication complexities, high cost and inaccuracies associated with the traditional micromodels limit their use. Recent developments in nanotechnology open a new window to fabricate new types of micromodels. These cutting edge techniques alleviate the above mentioned problems associated with traditional micromodels. The new generation of micromodels can be metres in length to accommodate scale dependency of dispersion phenomena. This is achieved in a 5 cm by 5 cm model. Objects representing grains can be fabricated as small as 3 micron with regular or random patterns. These physical models are made of glass or polymers. The polymer models are inexpensive and are reproducible in exact pattern and size. Wettability of these polymer models can be adjusted at any desirable level. Experiments using glass models can be operated at pressures as high as 35 MPa (5,000 psi) and at temperatures over 150 ºC. Also, we developed a new technique of image analysis which allows monitoring spatial and temporal changes in saturation without dying the fluids. In this article, we present the fabrication and development of the new micromodels. Example studies in miscible flooding, multiphase flow, fines migration and the VAPEX process are also presented.

Introduction
The subject of transport of fluids and particles in porous media is important in determining the performance of underground hydrocarbon reservoirs. Single phase flow, multiphase flow, miscible displacement, polymer/surfactant flooding and fines migration are examples of the processes of interest. Solid matrix of the porous rock is complex, both geometrically and morphologically. There are two major modelling approaches for the study of the above processes: macroscopic or black-box models and pore-level or phenomenological models.
In black-box models, the process is described simply based on the information of the influent and effluent parameters. These models present the behaviour of the process without any insights about what is happening in the pores. On the contrary, pore-level models describe the macroscopic behaviour using the knowledge of the pore-level interactions between the fluids and solid matrix. Physical micromodels are useful tools to study pore-level events of the transport of materials in porous media.
The use of glass micromodels to study pore scale displacement processes involved in multiphase fluid flow in porous media has been a useful technique for many years, and has been used by many different researchers(1–6). These studies can be generally grouped as low pressure experiments in large area models at room conditions, and narrow linear models at reservoir conditions.
The types of flow structures range from ball and stick controlled coordination systems to 2D representations of reservoir rock thin sections. With the new techniques, the scale of pore sizes range from less than 3 microns(7) to pores which are in the order of millimetres in diameter. The small dimension pore structure models are generally polymer replica models copied from an etched silicon master(7, 8). These polymer models are ideal for studies at low pressure and temperature.