The U.S. Bureau of Mines (USBM), developed by Donaldson et al. in 1969, is a method to measure wettability of petroleum reservoir rocks. In this method, the areas under the forced displacement
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 bo ...
curves of oil and water drive processes are denoted as
and
to calculate the USBM index.
:
USBM index is positive for water-wet rocks, and negative for oil-wet systems.
Bounded USBM (or USBM*)
The USBM index is theoretically unbounded and can vary from negative infinity to positive infinity. Since other wettability indices such as Amott-Harvey,
Lak wettability index In petroleum engineering, Lak wettability index, developed by Abouzar Mirzaei-Paiaman is a quantitative indicator to measure wettability of rocks from relative permeability data. This index is based on a combination of Craig's first rule. and mod ...
and modified Lak are bounded in the range of -1 to 1,
Abouzar Mirzaei-Paiaman highlighted the bounded form of USBM (called USBM*) as a replacement of the traditional USBM as
:
USBM* varies from -1 to 1 for strongly oil-wet and strongly water-wet rocks, respectively.
See also
*
Wetting
Wetting is the ability of a liquid to maintain contact with a solid surface, resulting from intermolecular interactions when the two are brought together. This happens in presence of a gaseous phase or another liquid phase not miscible with ...
*
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 ...
*
Lak wettability index In petroleum engineering, Lak wettability index, developed by Abouzar Mirzaei-Paiaman is a quantitative indicator to measure wettability of rocks from relative permeability data. This index is based on a combination of Craig's first rule. and mod ...
References
Petroleum geology
Surface science
Fluid mechanics
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