Changes

==Interaction between capillarity and buoyancy==

==Interaction between capillarity and buoyancy==

Virtually every reservoir holds its fluids in a porous network. The pores are normally well within the size range where capillary forces are strong. To fill a reservoir with oil or gas, the buoyancy force driving the oil or gas into the pores of the reservoir must overcome the capillary force developed between the original fluid and the displacing fluid. The smaller the pore throats, the greater the [[capillary pressure]] associated with them.

Virtually every [[reservoir]] holds its fluids in a [[Pore system fundamentals|porous network]]. The pores are normally well within the size range where [[Capillary pressure#Capillary pressure concepts|capillary forces]] are strong. To fill a reservoir with oil or gas, the buoyancy force driving the oil or gas into the pores of the reservoir must overcome the capillary force developed between the original fluid and the displacing fluid. The smaller the pore throats, the greater the [[capillary pressure]] associated with them.

Following the path of least capillary resistance, nonwetting fluids (gas or nonwetting oil) first move into the pore system that has the largest pore throats. Later, as the column height of the oil or gas grows and the buoyancy pressure increases, the hydrocarbons begin migrating into pores with smaller and smaller pore throats (in a water-wet system).

Following the path of least capillary resistance, nonwetting fluids (gas or nonwetting oil) first move into the pore system that has the largest pore throats. Later, as the column height of the oil or gas grows and the buoyancy pressure increases, the hydrocarbons begin migrating into pores with smaller and smaller pore throats (in a water-wet system).