Normalized frequency (digital signal processing)

2014-01-23T03:01:19Z

71.167.68.184: /* Alternative normalizations */ how did you measure the number of programs that use different methods?

The '''Amott test''' is one of the most widely used empirical [[wettability]] measurements for reservoir [[Core sample|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 (<math>I_w</math>) and the Amott oil index (<math>I_o</math>).

==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:
:<math>AI=I_w-I_o</math>
[[Image:Amott-Harvey_Index_calculation.png|thumb|300px|right|Figure 1: Amott–Harvey index and USBM number calculation.]]
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:
:<math>I_w=\frac{S_{spw}-S_{cw}}{1-S_{cw}-S_{or}}</math>
with <math>S_{spw}</math> is the water saturation for a zero capillary pressure during the imbibition process, <math>S_{cw}</math> is the irreducible water saturation and <math>S_{or}</math> is the residual oil saturation after imbibition.
:<math>I_o=\frac{S_{spo}-S_{or}}{1-S_{cw}-S_{or}}</math>
with <math>S_{spo}</math> is the oil saturation for a zero capillary pressure during the [[secondary drainage]] process, <math>S_{cw}</math> is the irreducible water saturation and <math>S_{or}</math> is the residual non-wetting phase saturation after imbibition.

A rock is defined as:
* Water wet when the Amott–Harvey index is between 0.3 and 1,
* Weakly water wet when the Amott–Harvey index is between 0 and 0.3,
* Weakly oil wet when the Amott–Harvey index is between -0.3 and 0,
* Oil wet when the Amott–Harvey index is between -1 and -0.3.

==See also==
* [[USBM index]] - an alternative wettability index
* [[Relative permeability]]
* [[Multiphase flow]]
* [[Capillary pressure]]
* [[Leverett J-function]]
* [[Imbibition]]

==External links==
* http://www.jgmaas.com/scores/facts.html

==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.
[[Category:Fluid dynamics]]

{{fluiddynamics-stub}}

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Normalized frequency (digital signal processing)