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The Amott test is one of the most widely used empirical wettability measurements for reservoir cores in
petroleum engineering Petroleum engineering is a field of engineering concerned with the activities related to the production of hydrocarbons, which can be either crude oil or natural gas or both. Exploration and production are deemed to fall within the ''upstrea ...
. The method combines two spontaneous
imbibition Imbibition is a special type of diffusion that takes place when liquid is absorbed by solids-Colloid, colloids causing an increase in volume. Water surface potential movement takes place along a concentration gradient; some dry materials absorb ...
measurements and two forced displacement measurements. This test defines two different indices: the Amott water index (I_w) and the Amott oil index (I_o).


Amott–Harvey index

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: :AI=I_w-I_o These two indices are obtained from special core analysis (SCAL) experiments ( porous plate or
centrifuge A centrifuge is a device that uses centrifugal force to subject a specimen to a specified constant force - for example, to separate various components of a fluid. This is achieved by spinning the fluid at high speed within a container, thereby ...
) by plotting the capillary pressure curve as a function of the water saturation as shown on figure 1: :I_w=\frac with S_ is the water saturation for a zero capillary pressure during the imbibition process, S_ is the irreducible water saturation and S_ is the residual oil saturation after imbibition. :I_o=\frac with S_ is the oil saturation for a zero capillary pressure during the secondary drainage process, S_ is the irreducible water saturation and S_ is the residual non-wetting phase saturation after imbibition. A rock is defined as:


See also

*
Capillary pressure In fluid statics, capillary pressure () is the pressure between two immiscible fluids in a thin tube (see capillary action), resulting from the interactions of forces between the fluids and solid walls of the tube. Capillary pressure can serve as b ...
*
Imbibition Imbibition is a special type of diffusion that takes place when liquid is absorbed by solids-Colloid, colloids causing an increase in volume. Water surface potential movement takes place along a concentration gradient; some dry materials absorb ...
* Leverett J-function *
Multiphase flow In fluid mechanics, multiphase flow is the simultaneous Fluid dynamics, flow of materials with two or more thermodynamic Phase (matter), phases. Virtually all processing technologies from Cavitation, cavitating pumps and turbines to paper-making ...
*
Relative permeability In multiphase flow in porous media, the relative permeability of a Phase (matter), phase is a dimensionless measure of the effective Permeability (Earth sciences), permeability of that phase. It is the ratio of the effective permeability of that ...
* TEM-function * Rise in core – An alternate Reservoir Wettability Characterization Method * Lak wettability index * USBM wettability index


References

* Dake, L.P., "Fundamentals of Reservoir Engineering", Elsevier Scientific Publishing Company, Amsterdam, 1977. * Amott, E., "Observations relating to the wettability of porous rock", Trans. AIME 219, pp. 156–162, 1959. Petroleum engineering


External links


Fluid flow in porous media : facts

Fundamentals of Wettability

Multi-phase Saturated Rock Properties: Wettability: Laboratory Determination
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