It is a specious argument that subsurface fluid moves from higher to lower pressure region. To clearify this confused idea

wide discussion is made in this article refering to this problem appeared recently in publications. According to Hubbert's theory on the fluid force potential and field intensity

it is

therefore

described that only fluid potential can be considered as criterion for determining direction and limitation of subsurface fluids instead of pore pressure. In order to show the regime of oil droplets and gas bubbles under hydrostatic or hydrodynamic forces

resultant force relation is derived and resolution is made according to net buoyancy and apparent water force field intensity. Application of Darcy's law to fluid migration is also mentioned. Equations describing ralation between water head and inclined oil-water interface elevation differences as well as the critical (maximum)height of oil column retained by capillary and hydrodynamic pressure are given and explained.