Which of the following lists the five types of reservoir boundaries?

• A. No-flow, Constant-pressure, Leaky, Conductive, Composite Limits
• B. No-flow, Constant-pressure, Leaky, Conductive
• C. No-flow, Constant-pressure, Conductive, Composite Limits
• D. No-flow, Constant-pressure, Leaky, Composite Limits

Answer: (A)

At a reservoir edge, how pressure and fluids respond is captured by boundary types. The five standard reservoir boundary types are: no-flow boundary (impermeable, no exchange across the boundary); constant-pressure boundary (the boundary pressure stays fixed, as with a large external reservoir); leaky boundary (some leakage across the edge allows limited cross-flow); conductive boundary (the boundary can transmit pressure changes with finite conductivity, enabling exchange); and composite limits (boundaries that combine behaviors of two or more types). This fifth category is needed because real reservoirs often exhibit mixed boundary behavior that isn’t fully described by a single simple type. The other lists omit one of these essential boundary behaviors, so they don’t provide the full set.