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 (
) and the Amott oil index (
).
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:
:
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:
:
with
is the water saturation for a zero capillary pressure during the imbibition process,
is the irreducible water saturation and
is the residual oil saturation after imbibition.
:
with
is the oil saturation for a zero capillary pressure during the
secondary drainage process,
is the irreducible water saturation and
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 : factsFundamentals of Wettability
Multi-phase Saturated Rock Properties: Wettability: Laboratory Determination
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