The area around a producing or injecting well where reservoir fluid is forced moving by the well operation.

In other words, the area, where reservoir fluid is moving along the streamlines which either stem from injecting well or end up at producing well.

For homogeneous reservoir it can be estimated as:

A_e = \frac{V_e}{h_e \ \phi_e}

where

	drainage volume
	effective formation thickness
	effective porosity

It is often related to drainage radius as:

A_e = \pi \, r_e^2

A_e = r_e^2

for square-shape drainage area

which can be is misnomer for other shapes of drainage area.

See also