Amott test

Amott Test A measure of wettability based on a comparison of the amounts of water or oil imbibed into a porous medium spontaneously and by forced displacement. Amott test results are expressed as a displacement-by-oil (60) ratio and a displacement-by-water ratio (Sw). In the Amott-Harvey test, a core is prepared at irreducible water saturation and then an Amott test is run. The Amott-Harvey relative displacement (wettability) index is then calculated as 6W — 60, with values ranging from — 1.0 for complete oil-wetting to 1.0 for complete water-wetting. See also reference 8, Wettability, Wettability Index. 

Wettability A qualitative term referring to the water- or oil-preferring nature of surfaces, such as mineral surfaces. Wettability may be determined by direct measurement of contact angles or inferred from measurements of fluid imbibition or relative permeabilities. Several conventions for describing wettability values exist. See also Amott Test, Contact Angle, Wettability Index, Wetting. 

Wettability Index A measure of wettability based on the U.S. Bureau of Mines wettability test in which the wettability index (W) is determined as the logarithm of the ratio of areas under the capillary pressure curves for both increasing and decreasing saturation of the wetting phase. Complete oil-wetting occurs for W = —oo (in practice about —1.5), and complete water-wetting occurs for W = oo (in practice about 1.0). Another wettability index is derived from the Amott-Harvey test. See also reference 8, Amott Test, Wettability. 

The main shortcoming, reported by Anderson [12] for the Amott methods, is their insensitivity near neutral wettability. In addition, the RDI relates relative volnmes of imbibition, but one also needs to look at these individual volumes to obtain a better understanding of flnid displacement as represented by this index. More recently, Ma [15] reported that the Amott test also does not discriminate adequately at strongly water-wet conditions and proposed an imbibition rate method for wettability (see below). Other shortcomings include variations in laboratory procednres. The temperatnre and length of time employed for the spontaneons imbibition and the pressure used during the forced displacement cycle are often modified to match specific field parameters or for ease of measurement in the laboratory. Consequently, the qnantitative values that are obtained can differ from one laboratory to another for reasons that are not related just to the wettability of the rock sample. 

Amott-Harvey. The wettability test devised by Amott [13] and its modification, the Amott-Harvey Relative Displacement Index (RDI) [14] are the most common quantitative measures of wettability employed for porous media by the oil industry. It relies on measurements of the saturation changes produced by spontaneous imbibition for both water. 

The relationship of SII to the Amott WI can be seen in Figure 6. This index is the same as the Amott WI at both neutral and highly water-wet conditions, 0 and 1, respectively. The denominator in equation 17 is normally estimated using a correlation obtained from conventional WI tests and can be formulated in terms of porosity, cp, and initial water saturation, Swi, both raised to powers. 

Mallach, A. (2008). Managing neighborhood change. Montclair, NJ National Housing Institute. McMUlen, D. P. (2006). Testing for monocentricity. In R. Amott D. P. McMiUen (Eds.), A companion to urban economics. Malden, MA BlackweU. 

The larger crystalline particles seen in the films (figs. 19-24) with lateral dimensions up to 300 [xm, either develop as isolated single crystals with lenticular, dendritic, acicular (needle-like) or spheroidal shapes, or grow into various crystalline formations. The shape and size of the particles are determined by the substrate and the specific R cation used (figs. 19-24). Energy dispersive X-ray analysis studies have indicated that these particles are rich in the particular R cation present in the test solution (Hinton and Amott 1989). X-ray diffraction studies have indicated a crystalline stmcture which could not readily be identified (Hinton and Amott 1989). Using the SEM, some microscopic evidence... 

For film formation and growth to occur, there must be some corrosion and evidence of this has been noted (Hinton and Amott 1989). However, the extent of corrosion as indicated by corrosion tests, is clearly very small (Hinton 1989, Hinton et al. 1984, 1985, 1988), probably because the rate of corrosion is controlled by the impedance to the cathodic reactions imposed by the presence of the surface film. 

The polarization curves for 7075 Al alloy, tested in a quiescent air-saturated 0.1 M NaCl solution, with and without separate additions of CeCb, PrCl3 and YCI3 at eoncentrations of 1000 ppm, are shown in fig. 28 (Amott et al. 1989). On the anodic arm of the polarization data (i.e. at potentials more positive than corr). the current increased rapidly with small changes in potential. This behaviour is typical of a corroding surface where the corrosion potential ( corr) and the pitting potential (Epu) are almost identical, in this case at around -0.72 V SCE. On the cathodic arm of the curve, the current density changes... 

The various routes that have been examined to enhance the corrosion resistance of anodized aluminium using cerium compounds, such as nitrates or sulphates, include pre- and post-treatments and anodizing with cerium species added to the bath formulation (the addition of cerium to commercial alloys for corrosion protection has not been reported). Each of these approaches has revealed some benefits in short-term laboratory corrosion tests. However, the imderlying mechanisms of corrosion protection are imclear. Corrosion inhibition of aluminium alloys caused by cerium species is well-established, with cerium acting as a cathodic inhibitor at intermetallic particles (Amott et al, 1987). Cerium oxide/ Itydroxide precipitates in response to the increase of pH at cathodic particles as the alloy briefly corrodes following its immersion in the environment. The precipitates stifle further corrosion by hindering the reduction of oxygen and water. 

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