When does hysteresis occur?

When does hysteresis occur?

• A. When the viscosity changes
• B. When the pressure changes
• C. When temperature changes
• D. When there is a reversal in the direction of saturation

Answer: (C)

Hysteresis is about the system remembering its past—the present response depends on the path taken, not just the current conditions. Temperature changes can induce this memory because many properties in a reservoir-rock system—interfacial tension, wettability, phase distribution, and even fluid viscosity—change with temperature and do not respond instantly or in the same way when temperature is rising versus falling. When you heat and then cool, the saturation and capillary behavior can trace a different route, producing a loop in the response. This history-dependent behavior is most clearly triggered by temperature cycling, making it the best fit for when hysteresis occurs.

Hysteresis is about the system remembering its past—the present response depends on the path taken, not just the current conditions. Temperature changes can induce this memory because many properties in a reservoir-rock system—interfacial tension, wettability, phase distribution, and even fluid viscosity—change with temperature and do not respond instantly or in the same way when temperature is rising versus falling. When you heat and then cool, the saturation and capillary behavior can trace a different route, producing a loop in the response. This history-dependent behavior is most clearly triggered by temperature cycling, making it the best fit for when hysteresis occurs.