Question

In a waterflooding project, how is the displacement efficiency mathematically defined at the moment of water breakthrough at the production well?

Accepted Answer

In waterflooding, which is a process where water is injected into an oil reservoir to push oil toward a production well, displacement efficiency measures how effectively the water has moved the oil out of the rock pores in the areas it has physically contacted. At the moment of water breakthrough—the exact time when injected water first reaches the production well—the displacement efficiency is mathematically defined as the difference between the initial oil saturation and the average oil saturation within the swept region, divided by the initial oil saturation. Initial oil saturation refers to the fraction of the reservoir&#x27;s pore space filled with oil before injection begins, while average oil saturation at breakthrough represents the remaining oil volume per unit of pore volume after the water has swept through the reservoir. Think of this like squeezing a wet sponge: if the sponge is fully saturated with water and you press it, the efficiency is the percentage of water you managed to push out compared to how much was there initially. Mathematically, this is expressed as (Soi - Sor) / Soi, where Soi is the initial oil saturation and Sor is the residual oil saturation, which is the fraction of oil that remains trapped in the rock pores even after water has passed through. This ratio indicates what percentage of the originally present oil was successfully recovered from the zone that the water has effectively cleaned or swept.

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In a waterflooding project, how is the displacement efficiency mathematically defined at the moment of water breakthrough at the production well?

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