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Experimental Investigation of Multiple Pore Volumes Needed to Reach Steady-state Foam Flow in a Porous MediaNormal access

Authors: O. M'barki, K. Ma, K. Mateen, G. Ren, H. Luo, V. Neillo, G. Bourdarot, D. Morel and Q. Nguyen
Event name: IOR 2019 – 20th European Symposium on Improved Oil Recovery
Session: Foams III
Publication date: 08 April 2019
DOI: 10.3997/2214-4609.201900148
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 2.81Mb )
Price: € 20

In most of transient foam core-flood studies, it is observed that multiple pore volumes of foam injection are needed before reaching the steady-state. The pore volumes needed appear to change with the degree of homogeneity of the porous media, orientation of the core, type of surfactant and the total injected flow rate. This is contrary to the foam-model results, which usually predict reaching the steady-state after approximately a single moveable pore volume of gas injection. It is important to understand whether this is a laboratory artifact due to core scale and/or gravity segregation, or could it also be present at reservoir scale, in order to have the reliable foam rheology predictive tools at reservoir scale. We designed the experimental set-up to investigate the phenomenon. In order to mitigate the gravity segregation in typical sand-pack systems, as well as to study the scale effect, we used slim-tubes of 1-ft and 6-ft length to understand the pore volumes needed to reach steady-state. Silica-sand-packed cylindrical slim tubes with an inner diameter of 0.66 inch were used in the foam flood experiments. Foaming surfactant solution and gas were co-injected into the slim-tube apparatus until a steady state is reached. Transient and steady-state pressure gradient data were recorded to investigate foam flow in the slim tube at a variety of injection conditions. Foam experiments with foot-long and 6-ft long slim tubes were compared in order to understand the effect of system length on foam generation and transport. One of the most important findings in this study is that the 6-ft long slim-tube requires significantly fewer pore volumes to reach a steady state than foot-long one under the same foam injection scheme. The analysis of our results revealed several key factors that played important roles in triggering foam generation in the slim tube. We found that the vertical configuration with gas and surfactant solution co-injected from the bottom significantly promoted foam generation in a relatively homogeneous system compared with the horizontal configuration. Foam generation in the slim tube was also facilitated by wider sand grain-size distribution in our tests possibly due to more favorable pore throat-to-body ratios for the snap-off mechanism. Additionally, higher injection velocity helped triggering foam generation in the slim tube. The results obtained in this study can be therefore used not only for improving fundamental knowledge of foam transport but also for upscaling foam models.

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