Concept of ‘Potential’ in a Petroleum Reservoir

Are we defining ‘potential’ in a petroleum reservoir to be @ macroscopic-scale; or, to be @ microscopic-scale?

Under Darcian approach, are we ‘really’ defining macroscopic potential in a petroleum reservoir to be an average of the microscopic concept - over all microscopic points - within a Representative Elementary Volume (REV) – centered @ a macroscopic point – within a petroleum reservoir?

In such cases, can the ‘total potential’ include - any other potential - than ‘pressure potential’ and ‘gravitational potential’?

Even in simple cases, are we strictly defining the macroscopic flux of water/oil/gas phase as a function of the “intrinsic phase average” of viscosity (μ), pressure (p) and gravitational forces (ρ∇z) – taken over the water/oil/gas phase within the REV?