Reference fluid bubble point tests

Figure 4.6a-c plot experimental results for the pure reference fluid bubble point tests for the 325 x 2300, 450 x 2750, and 510 x 3600 screen samples, respectively. To compare with pore diameters based on SEM analysis and historical data, also plotted for reference is a best fit linear curve to the data. As shown, for all three screens, bubble point is directly proportional to the contact angle corrected surface tension of each pure reference fluid, thus vaiidating the simplified model in Chapter 3. From the bubble point versus surface tension plots, one can easily determine a best fit effective pore diameter (Method 1) for each screen sample. These pore diameters, along with those based on SEM analysis and historical data, are listed in Table 4.2 for comparison of the three methods proposed earlier. Uncertainties for pore diameters based on reference fluid tests here are based on uncertainty in the DPT reading. Uncertainties for historical values are estimated. 

Pretest predictions were performed based on Equation (3.16). To do so, knowledge of mixture surface tension, mixture contact angle, and effective pore diameters is required. Here, pore diameters were based on Method 1 in Table 4.2, pure reference fluid bubble point tests. Mixture surface tension for all mass fractions was estimated from an equation of state and Langmuir isotherm (1916) fit to data available in the literature. Mixture contact angles were measured as a function of methanol mass fraction. 

Evaluating subcooled liquid states for bubble point tests would involve an added complexity, since one would have to take into account the pressure dependence of the surface tension (Turkevich and Mann, 1990a). Therefore, to permit facile interpretation of the data, reference fluid bubble point tests are conducted in equilibrium saturated liquid states. One can then use Equations (C.12-C.14) to determine the excess of composition of methanol ... 

There are a number of special symbols which are used only in referring to the results of a black oil reservoir fluid study. These symbols are defined in Table 10-3. The subscripts o and g refer to liquid and gas, as always. The subscripts F, D, and S refer to flash vaporization, differential vaporization, and separator test, respectively. The subscript b is added to indicate that the quantity is measured at the bubble point. 

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