The prepared core plug sample will be loaded vertically into the Hassler cell in such a way that the crude oil enters the sample from bottom to top (production direction) and that the drilling fluid is flown over the top.

Confining pressure is applied using and registered on the pressure gauge attached to the Hassler cell.

Initial oil permeability will be measured at steady state conditions by flowing formation mineral oil (or crude oil) in production direction through the core.

The drilling fluid sequences will then be simulated over the core-face at pressures similar to the drilling design as provided by the customer.

The drilling mud system on top of the core-face will then be shut-in at pressure and temperature for a predefined time. After the shut-in period, the leak-off volume will be determined by opening the bottom core face and the volume of the fluids produced will be measured.

A mud cleanup simulation or a filter-cake lift-off pressure can be determined if required. After the drilling simulation / sequences, regained formation oil permeability will be measured at steady state conditions again by flowing mineral oil (or crude oil) again in production direction through the core. Afterwards the sample is unloaded from the core holder.

Mud filter cake is inspected and photographed before mechanical removal takes place. The core plugs is then again spun to irreducible volumes and re-measured for final regained crude oil permeability.