Hi bevans,A good query. I've put an explanation in the first...

Hi bevans,

A good query. I've put an explanation in the first Slide below of how, from my understanding, drilling mud fluid invasion zones are generated.

From my understanding you don't need to suffer significant drilling mud fluid losses to generate an invasion zone that can on occasions severely affect the wireline logs ability to measure hydrocarbons reservoired within the formation. Also, what is generally moving into the reservoir formation is not the drilling mud itself (the solids) - this is designed to form the mud cake barrier - but the drilling mud's fluid component.

Trust this helps.

GLTAH
Cheers
VOGC