Reservoirs, wetting state

Wettability A qualitative term referring to the water- or oil-preferring nature of surfaces, such as the mineral surfaces in a porous medium (rock) of an oil-bearing reservoir. The flow of emulsions in porous media is influenced by the wetting state of the walls of pores and throats through which the emulsion must travel. See also Contact Angle. 

Carbon Dioxide Flood. Smith et al. [SO] studied the impact of wettability on tertiary oil recovery by carbon dioxide flooding after a secondary waterflood. It was reported that oil recovery could be improved by the wettability alteration of reservoir rock surfaces using surfactants. In this study, water-wet sandstone rock surfaces were modified by treatment with solutions of surfactants to neutral and even moderately oil-wet states. The laboratory results indicated that maximum tertiary oil recovery, after waterflood, by carbon dioxide flooding increased as the wettability of the sandstone decreased from highly water-wet to a neutral-wet or a slightly oil -wet surface. 

Based on the above discussion, the function of the wet-oxidation catalysts should be confined to (i) activation of oxygen and (ii) direct electron transfer with the reactants (redox reaction) in the first step of the reaction. CeO seems to effectively contribute to both factors. CeOj behaves quite differently from other oxides of lanthanide and is always a constituent of automobile-exhaust purification catalysts. It stabilizes supports and keeps high surface area [64,65], prevents the sintering of precious metals and, thus, stabilizes their dispersed state [66,67], and acts as an oxygen reservoir [68,72]. When combined with precious metals, it works in various reactions other than the purification of vehicle exhausts e.g., detoxification of NjO, methanol decomposition, methanol synthesis, combustion of formaldehyde, etc [47,73-75]. Precious metals are remarkably activated and behave quite differently on CeO compared with their action on other supports. 

Table 5.4), prepared from reduction of Pd(II) salts with potassium graphite. The results suggested that this catalyst was not very active. However, some years later Jikei and Kakimoto [73] prepared a more active Pd/CGr based on a smaller crystallite size. In 2002, Kohler et al. [74] studied a variety of Pd/C catalysts with different properhes (Pd dispersion, oxidation state, water content, conditions of catalysts preparation etc.) in the Heck reaction of aryl bromides with olefins (entry 4, Table 5.4). The authors pointed out the hypothesis that the leached Pd from the support is the active species and the solid Pd/C catalyst acts as a reservoir that delivers catalytically active Pd species into solution. All catalysts were obtained by wet impregnation (5% Pd loading). The Heck reaction can also be conducted in ionic liquids through promotion by microwave irradiation. Moreover the reaction of iodobenzene with methylacrylate in NMP was reported to be accelerated by ultrasound [75]. The ionic liquid containing the catalyst system was used five consecutive times with only a slight loss of activity (entry 5, Table 5.4) [76]. Perosa [77] reported the addition of a phase transfer catalyst to an ionic liquid as a method to accelerate the C-C coupling reaction. As far as we know, only by using ionic liquids has Pd on carbon been recovered and reused with success.

In some circumstances a fluid can be totally wetting to a porous medium. In such cases a thin film of wetting fluid covers the solid. If bulk amounts of wetting fluid are present they connect to thin film through transition regions in which the film thickens the wetting fluid is then distributed not only in continuous and disconnected pendular states of bulk material, but also in thin film states. When the surface area of the solid is great, as it can be, for example because of clay minerals in sandstone oil reservoirs, the thin films can contain appreciable inventories of... 

Recovery factors from oil reservoirs with use of surfactants and water injection with surfactants can be affected strongly by the rate and level of spontaneous imbibition. Improved oil recovery from low permeability rock may consequently be possible by decreasing the capillary to gravity force ratio, i.e. decrease Mb and Q. This could be done by decreasing IFT between oil and water if the displacement rate does not end up too slow for commercial use. In the following sections, displacement of oU by spontaneous imbibition at high and low IFT are considered for each wettability state water-wet, mixed-wet and oil-wet. 

This instrument consists of two normal thermometers, one of which has its bulb exposed to the air while the other has its bulb surrounded by a wick connected to a water reservoir. Evaporation of moisture from the wick to the surrounding air causes the wet bulb thermometer to show a lower reading than the corresponding dry bulb thermometer. The difference between the wet and dry bulb temperature related to the dry bulb temperature defines the hygrometric state of the atmosphere. Tables have been produced, from large numbers of observations, which give the relative humidity corresponding to likely wet and dry bulb temperature combinations. 

Before discussing the issues concerning the polymer experimental procedures, it is necessary to establish the conditions under which the more traditional field core data have been gathered (i.e. core permeabilities, relative permeabilities, etc.). Central to such consideration is the matter of core wettability and how the core has been conditioned or restored for the relative permeability experiments and, therefore, for the polymer flooding experiments. This very important matter will not be considered here, but it will be assumed that the wettability and conditioning of the reservoir core have been satisfactorily achieved. This is important for polymer properties, since the adsorption is thought to be greater in water-wet cores than in oil-wet systems. In the discussion below, it will be assumed in all cases that experiments in porous media use correctly conditioned field cores at residual oil (unless otherwise stated). The oil will be the (dead) field oil, and conditions of reservoir temperature, but not necessarily pressure, will be established in the core. 

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