What is the expected behavior of the gas bubble pressure in a shut-in well when gas percolates up the annulus?

In a shut-in well scenario where gas is migrating up the annulus, the expected behavior of the gas bubble pressure is to remain stable. This stability occurs because the pressure within the gas bubble is a function of the hydrostatic pressure exerted by the fluid column above it and the gas laws governing the behavior of gas. When a well is shut-in, the system reaches a new equilibrium state where the gas pressure stabilizes due to the balance between the upward movement of gas and the static pressure of the liquid column above it.

As gas percolates up, it may temporarily displace some of the fluid, but the overall system tends to stabilize as long as there is no rapid influx of external pressures or changes in temperature that could affect the bubble dynamics. Under normal conditions, as the gas rises, it compresses slightly due to the pressure from the liquid above, but the stable nature of the well's conditions allows the gas pressure to achieve a steady state.

In contrast, fluctuations typically occur in more dynamic scenarios such as rapid pressure changes or when a flow path is disrupted. A rapid increase in gas pressure could indicate an abnormal situation like a significant influx of gas or failure of downhole equipment, while negligible pressure would imply a vacuum or complete absence of