Abstract
A common issue in thermal oil recovery is that a high-permeability path in the reservoir diverts steam from reaching the bulk of the pay region. Injection of thermal foams is an effective approach to improve the oil recovery factor by increasing the effective viscosity of gas phase. Conducting conventional laboratory testing on thermal foams is time consuming, often not representative of field conditions, and delivers limited amount of data. This study will outline a novel microfluidic method for rapidly screening foaming agents at reservoir-relevant pressures and temperatures. The objective of this study is to provide operators with a tool that can rapidly screen chemical additives before conducting a field pilot.
Microfluidics is the study of fluid-flow at the micro-scale (typically tens to hundreds of microns). For measurement and analysis of fluid behavior and properties, microfluidics shows unique advantages including i) fast heat and mass transfer; ii) small amount of sample consumption; iii) full-factorial multiplexed analysis. In this study, microfluidic devices are fabricated from glass and silicon wafers in a clean-room environment. A network of microscopic channels etched in the silicon wafer emulates flow through the reservoir and allows reservoir engineers to visualize the foaming process and quantify foam stability under a variety of conditions. The microfluidic device has two parallel porous media sections with two permeabilities, which allows the comparison of foam velocity.
The results of this study show that recently developed high molecular weight sulfonates, can form stable foams at 250°C. This study provides the first micro-confined visual data showing the stability of thermal foams at high-temperature and -pressure. A key observation is that the mechanism responsible for increasing the pressure-drop across a porous media may not always be the formation of foam. Some chemicals showed that deposits form in the chip and increase the pressure drop. This is proof that selecting the correct chemistry is critical to preventing reservoir damage. The speed at which the foam moves through the two porous media sections is an indication of the foam's ability to increase resistance in the reservoir.
This study demonstrates a novel approach to screening thermal foams and describes the pore-scale mechanism of foam degradation at temperature. This is the first study showing visual evidence of how thermal foams perform at reservoir-relevant temperatures and pressures (250°C and 5 MPa).
