McKetta and Wehe

A typical chart for water content from this period is presented in Figure 4.21. In Figure 4.21 the water content chart at temperatures above the hydrate stability conditions is based primarily on the data of Olds et al. (1942) while the data of Skinner (1948) were the basis for extrapolations to temperatures below the hydrate formation point. A summary chart is given by McKetta and Wehe (1958). However, below the initial hydrate formation conditions, Figure 4.21 represents metastable values, as observed in gas field data by Records and Seely (1951). Kobayashi and Katz (1955) indicated that such concentration extrapolations across hydrate phase boundaries yield severe errors. 

In 1958, McKetta and Wehe published a chart for estimating the water content of sweet natural gas. This chart has been modified slightly over the years and has been reproduced in many publications, most notably the GPSA Engineering Data Book. A version of this chart is appended to this chapter. 

The quantity of water in saturated natural gas at various pressures can be estimated from Figure 11-1, which is based on the correlation of McKetta and Wehe (1958). This chart provides essentially the same data as the frequently used correlation of McCarthy et al. (1950), but has the advantage of including corrections for gas specific gravity and water salinity. The corrections are used as simple multipliers for water content values shown on the main chart. For example, if the gas has a molecular weight of 26 and is in equilibrium with an aqueous phase containing 3% salt, the correction factors would be Cq = 0.98 and C = 0.93. For this case, and conditions of I50°F and 3.000 psia, the gas would have a water content of (0.93)(0.98KI04) = 95 Ih/MMscf. 

Figure 11-1. Water content of saturated natural gas. Data of McKetta and Wehe (1958)...

Azarnoosh and McKetta (1958) gave data for propane in water for pressures from 1 atm to 500 psia and temperatures from 60 to 280°F. They refer to previous work and mention an extensive bibliography on water-hydrocarbon systems by McKetta and Wehe (1959). For a total pressure of 14.7 psia (1 atm), the mole fraction X10 of propane was given as 5.89, i.e., Nc h = 0.0000589 at 60°F. The vs pressure plots were curved. The same authors (1959) reported data for propylene in water and cited Hiraoka (1954) on acetylene in water for pressures up to 500 psi and temperatures to 86 F, Bradbury et al. (1952) on ethylene in water at pressures up to 8000 psi and temperatures up to 212 F, and Brooks and McKetta (1955) and Brooks, Haughn, and McKetta (1955) on 1-butene and water. The propylene data were given as mole fraction x 1 O for pressures up to 500 psia and temperatures up to 220 F. was given as 1.66, which is... 

It is essential to estimate correctly the saturated water content in the incoming natural gas (generally expressed in mg/Sm ). This can be estimated by using simulation software or it can be calculated using equation of states. The most commonly used method to estimate the saturated water content is to use a saturated water content chart developed by McKetta and Wehe as presented in Figure 5.6 [3]. 

The three phase program was then evaluated by comparing predicted and experimental results for the methane-n-butane-water and n-butane-1 butene-water systems as reported by McKetta and Katz (,9) and Wehe and McKetta (1 ). 

McKetta, J. J., and Wehe, A. H., in Petroleum Production Handbook, Vol. 2, T. C. Frick, ed., 1962, McGraw-Hill, New York, pp. 22-1-22-26 gives an extensive bibliography on the various hydrocarbon-water systems. 

The McKetta-Wehe chart is quite accurate for all gases (sweet, sour, and acid) for pressure up to about 1400 kPa (200 psia). However, it is not applicable to sour gas at high pressure. Fortunately, most... 

Figure 5. Hydrocarbon—rich vapor and liquid K— values for water-1 butene system. Calculated with equation-of-state parameters for 1-butene. Experimental data (O), Leland et al. (9) (A), Wehe and McKetta (10).

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