In the infinite conductivity vertical fracture flow regime, the slope of the pressure change is 0.5. Which option correctly states this value?

• A. 0.5
• B. 1
• C. 0
• D. 2

Answer: (A)

In this regime, the pressure disturbance spreads into the surrounding rock by diffusion. The infinite conductivity vertical fracture behaves like a constant-pressure source along the fracture, so the pressure change scales with the square root of time. That means ΔP ∝ t^0.5. On a log-log view of pressure change versus time, the slope is 0.5, which matches the given value. The other possibilities would imply linear, zero, or quadratic time dependencies, which do not describe diffusion-controlled fracture flow.