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 curves of oil and water drive processes are denoted as and to calculate the USBM index. [1] [2]
USBM index is positive for water-wet rocks, and negative for oil-wet systems.
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 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 [3]
USBM* varies from -1 to 1 for strongly oil-wet and strongly water-wet rocks, respectively.
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The rise in core (RIC) method is an alternate reservoir wettability characterization method described by S. Ghedan and C. H. Canbaz in 2014. The method enables estimation of all wetting regions such as strongly water wet, intermediate water, oil wet and strongly oil wet regions in relatively quick and accurate measurements in terms of Contact angle rather than wettability index.
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In petroleum engineering, Lak wettability index 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 modified Craig's second rule
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