The performances of 335 male and female swimmers competing in 50-, 100-, and 200-m freestyle events at the 1992 Barcelona Olympic Games were videotaped and analyzed to determine stroke length (SL), stroke rate (SR), starting time (ST), turning times (TI = turn in, TO = turn out), finishing (end) time (ET), and average velocity (AV); relationships were then determined among these variables in addition to height, weight, age, and final time (FT). Differences were subsequently assessed within and among the events, and comparisons were made between male and female performances. ST, TI, TO, ET, and SL were identified as principal components of successful swimming performance at each distance. Results revealed statistically significant correlations between factors for all events. The men were older and taller; possessed longer stroke lengths; and started, turned, and swam faster than the women. As the race distance increased from 50 to 200 m, ST, TI, TO, SL, and ET increased for both men and women, while age, SR, and AV decreased.
In order to determine the effect of loads worn or carried on walking mechanics, 1 1 men and 1 1 women were filmed using high speed cinematography as they performed overground walking at 1-78 m/s under five load conditions. The loads included a baseline condition in which subjects carried no added load, and additional loads of approximately 9, 17,29 and 36 kg consisting of standard military items. The latter two loads were added in the form of a framed rucksack system. Values for several variables frequently used to described temporal and kinematic characteristics of waking were quantified from the film. These included stride length, stride rate, single leg support time, double-support time, swing time and the forward inclination of the trunk. The results of the study demonstrated that the males and females displayed significantly different gait patterns under all load conditions. Not unexpectedly, the females required a higher rate of stepping than the males because of their shorter stride lengths. The results also demonstrated that the walking . patterns of both the male and female subjects were'affected by the increases in carried load. In general, stride length and swing time decreased while stride rate and double-support time increased with increases in load. There was also an increased forward inclination of the trunk but only for the two heaviest loads which were carried in a rucksack. While the changes in gait characteristics were relatively small for the male subjects, the females were affected to a greater extent thereby demonstrating a greater sensitivity to load magnitude. It was concluded that careful consideration must be given to the absolute loads carried by males and females. Not only is it important for load requirements to be lower for females because of the physiological implications but also because of biomechanical implications and the associated mechanical stresses which must be endured during locomotion. While this study was directed primarily towards military applications, the results should also have implications for load carrying in a variety of situations and environments, including industrial and recreational appiications.
Many crude oil candidates for enhanced oil recovery by alkaline flooding produce their lowest interfacial tension at very low concentrations of alkali. Alkaline consumption by the rock makes propagation through the oil reservoir of such propagation through the oil reservoir of such dilute alkaline solutions prohibitively slow. The dilemma of having to choose between highest displacement efficiency (lowest interfacial tension) and satisfactory displacement rate can be resolved by adding cosurfactants to the alkali. Low concentrations of properly chosen cosurfactants raise the concentration of electrolyte required for minimum interfacial tension to alkali concentrations high enough for satisfactory propagation of the alkaline bank. That is, just as in chemical flooding, a cosurfactant can be used to raise the "salinity requirement" of an alkaline flood. Activity Maps, similar to the Salinity Requirement Diagrams of chemical flooding, are useful in formulating and understanding the results of cosurfactant-enhanced alkaline floods. Alkaline flooding systems, formulated by the methods discussed in this paper, recover as much oil in laboratory core floods as well-formulated chemical flooding systems. Introduction Johnson defined four mechanisms of enhanced oil recovery by alkaline flooding:"Emulsification and Entrainment" in which the crude oil is emulsified in-situ and entrained by the flowing aqueous alkali,"Wettability Reversal (Oil-Wet to Water-Wet)" in which oil production increases due to favorable changes in permeabilities accompanying the change in wettability,"Wettability Reversal (Water-Wet to Oil-Wet)" in which low residual oil saturation is attained through low interfacial tension and viscous water-in-oil emulsions working together to produce high viscous/ capillary number, and"Emulsification and Entrapment" in which sweep efficiency is improved by the action of emulsified oil droplets locking the smaller pore throats. Castor, et al proposed a fifth mechanism, "Emulsification and proposed a fifth mechanism, "Emulsification and Coalescence," in which unstable water-in-oil emulsions form spontaneously in the alkaline solution, then break to create local regions of high oil saturation, hence, increased permeability to oil. Because alkaline flooding research predated surfactant flooding research in Shell and basic concepts of salinity control and low IFT viscous/ capillary mechanisms were developed in those early alkaline studies, we have generally considered both in-situ generated surfactant flooding and preformed surfactant flooding to be special cases preformed surfactant flooding to be special cases of the same process. That is, we view alkaline flooding as a type of chemical flooding in which the surfactant is formed in-situ as the alkali converts petroleum acids in the crude oil to soaps. Our objective is to improve the cost- effectiveness of alkaline flooding by applying principles developed through recent research on principles developed through recent research on chemical flooding. As in chemical flooding, high oil-displacement efficiency depends upon attaining and maintaining conditions of "optimum salinity." When optimum salinity cannot be achieved by simple adjustments in salinity, we use cosurfactants, just as in chemical flooding. In keeping with the terminology of chemical flooding, we call the petroleum soaps formed during and alkaline flood the "primary surfactant" and any added preformed surfactant the "cosurfactant." Hence, supplementing an alkaline flood with preformed surfactants, added to the alkaline slug preformed surfactants, added to the alkaline slug before injection, becomes "cosurfactant-enhanced alkaline flooding." P. 413
The performance of male and female swimmers (N = 397) competing in the preliminary heats of the four 100-meter swimming events during the Seoul Olympic Games was videotaped and later analyzed to determine stroke rate (SR) and stroke length (SL). These data were combined with age, height, and final time (FT) values for statistical analyses which included the relationships among these variables, comparison of male and female performance, and assessment of differences in the four events. The results revealed the following ranges of correlations between SR and SL (rs from −0.65 to −0.90), SL and FT (rs from −0.32 to −0.80), height and SL (0.19 to 0.58), and age and FT (-0.16 to −.051). The factor of SL was identified as the dominant feature of successful swimming performance. The men were older and taller, had longer stroke lengths and higher stroke rates (two of four events), and swam faster than the women. The differences in final times across the four events (freestyle fastest, breaststroke slowest) were due to specific combinations of SR and SL, with neither parameter being consistently dominant.
Resultsof laboratory cbemicaI jloods are present ed to show that equilibrium pbases observed irr test tubes are representative of phases produced in core flow experiments. Consequently, many performance characteristics of chemical floods can be' explained and predicted from equilibrium surfactant-brin e-oil phase diagrams. An oil reservoir under chemical flooding can be visualized as a series" o/ connected cells with phase equilibrium attained in each. Fluid flow from one cell to the next is governed, not so much by initial properties of the oil, brine, or chemical slug and drive, as by properties o/ equilibrium phases formed from those fluids. Three types o{ equilibrium phase environment are deiined. Results o~interracial ten-"on measurements and laboratory flow experiments indicate that chemical f[oods should be designed to keep as much surfactant as possible /or as long as possible in the "Type iii" phase environment while the surfactant is traversing tbe reservoir.
A one-dimensional, compositional, chemical-flood simulator was developed to calculate oil recovery as a function of several major process variables. The principal relationships included are phase behavior and interfacial tensions as a function of electrolyte and surfactant concentrations, and polymer viscosity as a function of electrolyte and polymer viscosity as a function of electrolyte and polymer concentration. Emphasis was on studying the polymer concentration. Emphasis was on studying the process itself, especially complex interactions that process itself, especially complex interactions that occur because of two- and three-phase behavior, interfacial tension, fractional flow, dispersion, adsorption, cation exchange, chemical slug size, and polymer transport. Introduction Nelson and Pope reported laboratory flow results in which phase behavior plays a key role in oil recovery by chemical flooding. They show that many characteristics of chemical floods can be explained by considering the equilibrium mixing and transport of surfactant/brine/oil systems in light of phase behavior observed in external mixtures. phase behavior observed in external mixtures. Although based on highly idealized representations of the key properties involved, we believe that the simulator described here can yield significant insight into phase-related process mechanisms, such as "oil swelling," the interactions among process variables, and the relative merit of various process variables, and the relative merit of various chemical flooding strategies. The framework for systematically improving the compositional aspects of numerical simulation of chemical flooding is evident with our approach. This is because a completely compositional model based on total concentrations, rather than saturations, is assumed from the start. Then, the calculation of phase concentrations, and from them phase saturations, for any desired number of phase saturations, for any desired number of components and phases with any type phase behavior is a relatively simple matter. Conceptually, mathematically, and numerically, this approach is simpler and easier to use than the traditional approach used in reservoir engineering simulation, although in principle they can be made equivalent. The cases illustrated here are for up to six components and up to three phases, using highly simplified representations of the binodal and distribution curves for the surfactant/brine/oil systems and the properties of the various phases that form. Even so, as many as 64 parameters are required to specify the process. ASSUMPTIONS, EQUATIONS, AND NUMERICAL TECHNIQUE The basic assumptions of the model are as follow.The system is one-dimensional and homogeneous in permeability and porosity.Local thermodynamic equilibrium exists everywhere.The total mixture volume does not change when mixing individual components (delta VM = 0).Gravity and capillary pressure are negligible.Fluid properties are a function of composition only.Darcy's law applies.Physical dispersion can be approximated adequately with numerical dispersion by selecting the appropriate grid size and time step. Additional assumptions are required to model various properties such as interfacial tension, viscosity, etc. However, for the most part, these are changed readily by the user and are not considered as basic as the above assumptions, which also can be relaxed, but only with considerably more effort. The auxiliary assumptions will be given, therefore, with the specific examples discussed below. Given the above assumptions, the continuity equations for each component i and np phases are (1) SPEJ P. 339
Salinity design goals are to keep as much surfactant as possible in the active region and to minimize surfactant retention. Achieving these is complicated because (1) compositions change as a result of dispersion, chromatographic separation of components distributed among two or more phases, and retention by adsorption onto rock and/or absorption in a trapped phase; (2) in the presence of divalent ions, optimal salinity is not constant but a function of surfactant concentration and calcium/sodium ratio; and (3) the changing composition of a system strongly influences transport of the components.A one-dimensional (ID) six-component finitedifference simulator was used to compare a salinity gradient design with a constant salinity design. Numerical dispersion was used to evaluate the effects of dispersive mixing. These simulations show that, with a salinity gradient, change of phase behavior with salinity can be used to advantage both to keep surfactant in the active region and to minimize retention. By contrast, under some conditions with a constant salinity design, it is possible to have early surfactant breakthrough and/or large surfactant retention.Other experiments conducted showed that high salinity does retard surfactant, and, if the drive has high salinity, a great amount of surfactant retention can result. The design that produced the best recovery had the waterflood brine overoptimum and the drive underop-0197-752018310006-8825$00.25
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