# Complex Geometry

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To conclude this project, the simulation of gas injection have been carried out, using a complex geometry investigated by our partner group.

Indeed, they  simulated the injection of water in a cave full of oil in order to see the amount of oil which can be recovered and where the remaining oil is wedged. The geometry and mesh caracteristics can be found in the website of our partner group:

http://hmf.enseeiht.fr/travaux/bei/beiep/content/2014-g01

Here, a injection of gas in this geometry is simulated. The initial amount of oil corresponds to the quantity of oil wedged into the cap of the cavity at the final time of the two-phase flow simulation.

The table below recaps the main characteristics of the simulation:

Inlet velocity Physical properties Mesh Time step Physical time simulated
0.6 m/s real properties refined $10^{-4}$ 5 s

On the video,we can see that while the gas is injected into the domain, water and oil are driven out. Indeed, the graphs below shows that their volume fractions in the domain decrease with time.

Because of its lighter density, gas first occupies the first cave, pushing the oil out of the cavity. The oil is therefore drived out to the outlet, increasing the oil recovery ratio.

After the gas has fulfilled the cave, some of the gas flows over the obstacle between these two caves and drives the oil in the second cave out. Finally, it seems that after a certain time,  a maximum oil recovery ratio has been reached.

The first figure shows the outlet oil and water flow rate in function of time and the second figure shows the oil, water and gas volume fraction in the domain.

From these figures, we can observe that when 25% of gas is injected in the domain, gas starts to leave the domain. Moreover, the repartition of phase does not change: a stable state is reached where no oil can be recovered anymore.

In the end, the simulation show that 34.3% oil was recovered in this procedure. Therefore, after water injection recovery, gas injection would be a good choice to improve oil recovery efficiency.