Amott test

The Amott test is one of the most widely used empirical wettability measurements for reservoir cores in petroleum engineering. The method combines two spontaneous imbibition measurements and two forced displacement measurements. This test defines two different indices: the Amott water index (${\displaystyle I_{w}}$) and the Amott oil index (${\displaystyle I_{o}}$).

The two Amott indices are often combined to give the Amott–Harvey index. It is a number between -1 and 1 describing wettability of a rock in drainage processes. It is defined as:

These two indices are obtained from special core analysis (SCAL) experiments (porous plate or centrifuge) by plotting the capillary pressure curve as a function of the water saturation as shown on figure 1:

with ${\displaystyle S_{spw}}$ is the water saturation for a zero capillary pressure during the imbibition process, ${\displaystyle S_{cw}}$ is the irreducible water saturation and ${\displaystyle S_{or}}$ is the residual oil saturation after imbibition.

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