pressure is the same at inlet and outlet and only the gravitational force is driving the fluid down the packed porous bed

all derived for homogeneous rocks in which the permeability was uniform throughout the rock

 composed of several distinct units or layers each with its own permeability

are often found to be continuous between wells throughout the entire reservoir

can and do occur laterally as well as vertically in reservoirs.

In addition to the natural variations in lateral permeability in reservoir rocks, ____________________ in lateral permeability can also be present.

which refers to permeability damage caused in regions near the wellbore by the invasion of mud filtrate during  drilling operations

a layer of low permeability that is in series with the rest of the reservoir

can and do increase the permeability in the vicinity of the wellbore

split into different flow rates in different layers having different permeabilities