Which term describes the fraction of pore space occupied by water when the hydrocarbon content is at maximum and can only be reduced by flow of a very dry gas that evaporates the water?

Which term describes the fraction of pore space occupied by water when the hydrocarbon content is at maximum and can only be reduced by flow of a very dry gas that evaporates the water?

• A. Capillary Water Saturation
• B. Wettability Water Saturation
• C. Irreducible Water Saturation
• D. Residual Water Saturation

Answer: (C)

Capillary trapping leaves behind a minimum amount of water in the pore space that cannot be removed by further hydrocarbon flow. This is irreducible water saturation—the fraction of pore space that water must occupy when hydrocarbons have displaced as much water as possible. It remains because capillary forces hold those-water-filled pores too strongly to be drained by movement of hydrocarbons alone. Only an external process that eliminates water, like injecting a very dry gas that evaporates the remaining water, can reduce this saturation. While residual or trapped water terms are related, the scenario described—removal through evaporation by a dry gas—fits irreducible water saturation most directly.

Capillary trapping leaves behind a minimum amount of water in the pore space that cannot be removed by further hydrocarbon flow. This is irreducible water saturation—the fraction of pore space that water must occupy when hydrocarbons have displaced as much water as possible. It remains because capillary forces hold those-water-filled pores too strongly to be drained by movement of hydrocarbons alone. Only an external process that eliminates water, like injecting a very dry gas that evaporates the remaining water, can reduce this saturation. While residual or trapped water terms are related, the scenario described—removal through evaporation by a dry gas—fits irreducible water saturation most directly.