Visualization Investigation of Foam Injection in a Transparent Fractured Porous Medium

Naturally fractured reservoir account for 20% of world's oil reserves, in these reservoirs conductivity is mostly in the fracture network while the oil is mostly in the matrix and after primary recovery most of oil remains in the reservoir. Most of secondary or tertiary recovery methods such as water injection or gas injection are not efficient in fractured reservoirs. One of the remedy methods to control and improve volumetric sweep efficiency is foam injection. Foam in porous media is a dispersed gaseous phase within a continuous aqueous phase comprised mainly of thin films known as lamellae. The lamellae are stabilized by adsorption of surfactant at the gas/liquid interfaces. In the paper, experiments were performed to study the pertinent oil displacement mechanisms during gas and foam injection in a transparent fractured porous medium. Transparent material such as glass was used to construct micro models and to study various aspects of fluid displacement at pore scale. By using micro models, the displacement of the fluids can be observed and investigated in terms of micro-geometry and physical characteristics of the presented liquids, gases and solids. The classification of foams in based on their bubble size and gas fraction. The strength of foam is measured by the magnitude of the pressure drop that is generated along the medium. To create a large pressure drop very strong foams, and therefore very small bubbles, are required. Low productivity of gas injection in fractured reservoir leads to use foam instead of gas in order to increase resistance of fracture corridor against the injected fluid and to better control to mobility of gas.