Amott wettability is the simplest way of determining the wettability characteristics of a reservoir.
This method uses natural imbibition and drainage and forced imbibition and drainage. The word forced refers to a flushing or a centrifuge process. Water wet and oil wet indices are then calculated from the saturation changes.
The technique is based on the premise that a strongly wetting fluid will spontaneously imbibe until the residual saturation of the non wetting fluid is obtained.
A Lab Alliance HPLC pump is used to induce forced imbibitions and drainage in the sample and measure liquid permeability at various stages of the process.
Oil and water wettability indexes are calculated based on the volumes of fluid displaced. An Index of 1 indicates a strongly wetting fluid. An index of 0 indicates a strongly non wetting fluid.
Amott – Harvey wettability Index is calculated as
AHWI = Water Wettability Index – Oil Wettability Index
A positive index suggests water wet condition whereas a negative index suggests an oil wet condition.