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There are two special reservoir flow regimes which are both stabilised and maintain constant flow rate: steady state regime Steady State flow regime (SS) and pseudo and Pseudo-steady state regime State flow regime (PSS).
The steady state regime Steady State flow regime (SS) regime is is reached when the flow is stabilised with the full pressure support at the external boundary.
The pseudoPseudo-steady state State flow regime (PSS) regime is is reached when the flow is stabilised with with no pressure support at the external boundary.
In both above cases, the drawdown and flow rate will stay constant upon productivity stabilisation.
As for formation and bottom-hole pressure in PSS they will be synchronously varying while in SS they will be staying constant.
The table below is summarizing summarising the major differences between SS and PSS regimes.
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It's again important to avoid confusion between the termines stationary conditions (which mean that refered referred properties are not chaning changing in time) and stabilised flow conditions which may admit pressure and rate variation.
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