Which reservoir state is described by pressure changes being uniform across the reservoir with time?

Which reservoir state is described by pressure changes being uniform across the reservoir with time?

• A. Unsteady State
• B. Steady-State
• C. Transient State
• D. Pseudosteady-state

Answer: (D)

The main idea is that the entire reservoir shares the same rate of pressure change as production continues. In pseudosteady-state, the pressure field evolves so that the decline over time is essentially uniform everywhere in the reservoir, even though the absolute pressure still varies with position (for example, from the well outward). This happens when the production rate and boundary conditions produce a self-similar, time-varying pressure distribution that looks steady in shape but declines in magnitude with time. It’s different from a truly steady state, where pressure would not change with time at all, and from a transient/unsteady state, where the rate of pressure change varies from one location to another and evolves in a more complex way. Hence, uniform pressure change across the reservoir with time is a hallmark of pseudosteady-state.

The main idea is that the entire reservoir shares the same rate of pressure change as production continues. In pseudosteady-state, the pressure field evolves so that the decline over time is essentially uniform everywhere in the reservoir, even though the absolute pressure still varies with position (for example, from the well outward). This happens when the production rate and boundary conditions produce a self-similar, time-varying pressure distribution that looks steady in shape but declines in magnitude with time. It’s different from a truly steady state, where pressure would not change with time at all, and from a transient/unsteady state, where the rate of pressure change varies from one location to another and evolves in a more complex way. Hence, uniform pressure change across the reservoir with time is a hallmark of pseudosteady-state.