Water wetting

It is believed that the majority of clastic reservoir rocks are water wet, but the subject of wettability is a contentious one. 

Equation 11-30 may be integrated to obtain the profile of a meniscus against a vertical plate the integrated form is given in Ref. 53. Calculate the meniscus profile for water at 20°C for (a) the case where water wets the plate and (b) the case where the contact angle is 40°. For (b) obtain from your plot the value of h, and compare with that calculated from Eq. 11-28. [Hint Obtain from 11-15.]... 

As a somewhat anecdotal aside, there has been an interesting question as to whether gold is or is not wet by water, with many publications on either side. This history has been reviewed by Smith [119]. The present consensus seems to be that absolutely pure gold is water-wet and that the reports of non wetting are a documentation of the ease with which gold surface becomes contaminated (see Ref. 120, but also 121). The detection and control of surface contaminants has been discussed by White [121] see also Gaines [122]. 

Templeton obtained data of the following type for the rate of displacement of water in a 30-/im capillary by oil (n-cetane) (the capillary having previously been wet by water). The capillary was 10 cm long, and the driving pressure was 45 cm of water. When the meniscus was 2 cm from the oil end of the capillary, the velocity of motion of the meniscus was 3.6 x 10 cm/sec, and when the meniscus was 8 cm from the oil end, its velocity was 1 x 10 cm/sec. Water wet the capillary, and the water-oil interfacial tension was 30 dyn/cm. Calculate the apparent viscosities of the oil and the water. Assuming that both come out to be 0.9 of the actual bulk viscosities, calculate the thickness of the stagnant annular film of liquid in the capillary. 

Pentaerythritol may be nitrated by a batch process at 15.25°C using concentrated nitric acid in a stainless steel vessel equipped with an agitator and cooling coils to keep the reaction temperature at 15—25°C. The PETN is precipitated in a jacketed diluter by adding sufficient water to the solution to reduce the acid concentration to about 30%. The crystals are vacuum filtered and washed with water followed by washes with water containing a small amount of sodium carbonate and then cold water. The water-wet PETN is dissolved in acetone containing a small amount of sodium carbonate at 50°C and reprecipitated with water the yield is about 95%. Impurities include pentaerythritol trinitrate, dipentaerythritol hexanitrate, and tripentaerythritol acetonitrate. Pentaerythritol tetranitrate is shipped wet in water—alcohol in packing similar to that used for primary explosives. 

The main features in which the Radford process differs from the batch operation are in thermal dehydration and compounding. Water-wet nitrocellulose on a continuous vacuum belt filter is vacuum-dried followed by hot air transfusion (80°C) to reduce the moisture to less than 2%. After cooling, alcohol is sprayed on the nitrocellulose to a concentration of 15—20%. The alcohol-wet nitrocellulose is then transferred from a surge feeder to a compounder by a continuous weigh-belt along with the other ingredients of the composition, which are also weighed and added automatically. 

Fig. 2. Cellulose acetate stress—strain properties at standard and wet conditions, tested at 60% min extension rate, 3.9 cm gauge length. Sample conditions standard, 21°C, 65% rh wet, 21°C, water wet. To convert N/tex to gf/den, multiply by 11.33.

The surface of PTFE articles is sHppery and smooth. Liquids with surface tensions below 18 mN/m(=dyn/cm) are spread completely on the PTFE surface hence, solutions of various perfluorocarbon acids in water wet the polymer (78). Treatment with alkafl metals promotes the adhesion between PTFE and other substances (79) but increases the coefficient of friction (80). 

Surfactants. Surfactants (qv) perform a variety of functions in a drilling fluid. Depending on the type of fluid, a surfactant may be added to emulsify oil in water (o/w) or water in a nonaqueous Hquid (w/o), to water-wet mud soHds or to maintain the soHds in a nonwater-wet state, to defoam muds, or to act as a foaming agent. 

Wettabihty is defined as the tendency of one fluid to spread on or adhere to a soHd surface (rock) in the presence of other immiscible fluids (5). As many as 50% of all sandstone reservoirs and 80% of all carbonate reservoirs are oil-wet (10). Strongly water-wet reservoirs are quite rare (11). Rock wettabihty can affect fluid injection rates, flow patterns of fluids within the reservoir, and oil displacement efficiency (11). Rock wettabihty can strongly affect its relative permeabihty to water and oil (5,12). When rock is water-wet, water occupies most of the small flow channels and is in contact with most of the rock surfaces as a film. Cmde oil does the same in oil-wet rock. Alteration of rock wettabihty by adsorption of polar materials, such as surfactants and corrosion inhibitors, or by the deposition of polar cmde oil components (13), can strongly alter the behavior of the rock (12). 

When water is injected into a water-wet reservoir, oil is displaced ahead of the injected fluid. Injection water preferentially invades the small- and medium-sized flow channels or pores. As the water front passes, unrecovered oil is left in the form of spherical, uncoimected droplets in the center of pores or globules of oil extending through intercoimected rock pores. In both cases, the oil is completely surrounded by water and is immobile. There is htde oil production after injection water breakthrough at the production well (5). 

In an od-wet rock, water resides in the larger pores, oil exists in the smaller pores or as a film on flow channel surfaces. Injected water preferentially flows through the larger pores and only slowly invades the smaller flow channels resulting in a higher produced water oil ratio and a lower oil production rate than in the water-wet case. 

The data available are generally for the Athabasca materials, although workers at the University of Utah (Salt Lake City) have carried out an intensive program to determine the processibiUty of Utah bitumen and considerable data have become available. Bulk properties of samples from several locations (Table 3) (9) show that there is a wide range of properties. Substantial differences exist between the tar sands in Canada and those in the United States a difference often cited is that the former is water-wet and the latter, oil-wet (10). 

Froth from the hot-water process may be mixed with a hydrocarbon diluent, eg, coker naphtha, and centrifuged. The Suncor process employs a two-stage centrifuging operation, and each stage consists of multiple centrifuges of conventional design installed in parallel. The bitumen product contains 1—2 wt % mineral (dry bitumen basis) and 5—15 wt % water (wet diluted basis). Syncmde also utilizes a centrifuge system with naphtha diluent. 

An attempt has been made to develop the hot-water process for the Utah sands (Fig. 10) (20). With od-wet Utah sands, this process differs significantly from that used for the water-wet Canadian sands, necessitating disengagement by hot-water digestion in a high shear force field under appropriate conditions of pulp density and alkalinity. The dispersed bitumen droplets can also be recovered by aeration and froth flotation (21). 

The water-wet CN can be gelatinized with softeners such as phthalates and dried on dmms or band driers for the manufacture of CN chips (68). These CN chips can be colored with pigments so that colored enamels can be produced without using ball or roUer mills. 

Decomposition Flame Arresters Above certain minimum pipe diameters, temperatures, and pressures, some gases may propagate decomposition flames in the absence of oxidant. Special in-line arresters have been developed (Fig. 26-27). Both deflagration and detonation flames of acetylene have been arrested by hydrauhc valve arresters, packed beds (which can be additionally water-wetted), and arrays of parallel sintered metal elements. Information on hydraulic and packed-bed arresters can be found in the Compressed Gas Association Pamphlet G1.3, Acetylene Transmission for Chemical Synthesis. Special arresters have also been used for ethylene in 1000- to 1500-psi transmission lines and for ethylene oxide in process units. Since ethylene is not known to detonate in the absence of oxidant, these arresters were designed for in-line deflagration application. 

LEAKS ONTO WATER, WET GROUND, OR INSULATION 7.3.1 Leaks Onto Water or Wet Ground... 

Many catalysts are sold as water-wet and are useful when water can be tolerated. These wetted catalysts are much less apt to start fires. Catalysts can be wetted with safety with methylcellosolve (2 ethoxyethanol) before adding them to volatile solvents 40). 

Figure 13 Influence of coupling agents and fiber content on the characteristic values of kenafreinforced recycled PE at room temperature (dry state) and after exposure in boiling water (wet-state) [57].

Water Wetting Solids. The water wetting solids test (oil-base mud coating test) indicates the severity of water wetting solids in oil-base mud [24]. The items needed are... 

The water phase of oil-base mud can be freshwater, or various solutions of calcium chloride (CaCl ) or sodium chloride (NaCl). The concentration and composition of the water phase in oil-base mud determines its ability to solve the hydratable shale problem. Oil-base muds containing freshwater are very effective in most water-sensitive shales. The external phase of oil-base mud is oil and does not allow the water to contact the formation the shales are thereby prevented from becoming water wet and dispersing into the mud or caving into the hole. 

In the water-blocking mechanism large volumes of invaded liquid may be retained by low permeability or low-pressure formations. The blocking may occur for an oil wet and a water wet sandstones. 

Formations can be oil wet or water wet. The fluid filtrate depends on what is the continuous phase of the completion fluid. Thus the formation wettability can be reduced by wettability charge. This effect can be controlled either by proper fluid selection or by treatment with water wetting additives. 

The temperature of air as indicated by a thermometer when a water-wet wick encloses its bulb. If the surrounding air is not saturated water will evaporate, taking the latent necessary latent heat from the thermometer bulb which then gives a lower reading than a dry bulb in the same air. The depression in wet bulb temperature is proportional to the amount of moisture in the air. 

In addition to the careful selection of structural metals, the cathodic protection of water-wetted parts may also be specified. For most boiler plant systems, however, because of the tortuous and extended waterside surfaces involved, the use of cathodic protection is only a partial solution to controlling corrosion and should never be the sole secondary protocol. Rather, cathodic protection functions well when employed as part of a more comprehensive program that includes appropriate internal chemical treatments. 

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