Phase behavior tests

The chemical slug used in the project was prepared in a fresh, relatively soft brine (800 ppm of total dissolved solids, 18 ppm hardness). On the basis of interfacial tension measurements (phase-behavior tests were not reported), a solution of 0.8 wt% NaaCOa and 0.1 wt% Petrostep BlOO, a... 

Phase behavior tests are conducted in small tubes that are called pipettes. Therefore, the phase behavior tests sometimes are called pipette tests. For pipette tests, the tips of—for example, 5 mL—glass pipettes from Fisher or similar pipettes are sealed by acetylene and oxygen flame with a Victor torch. Phase behavior tests include the aqueous stability test, salinity scan, and oil scan. The main objective of phase behavior tests is to find the chemical formula... 

FIGURE 7.4 Flow chart of phase behavior tests. 

Set up a base model like batch.txt for surfactant flooding with injection compositions (water/oil ratio, surfactant concentration, and so on) being the same as the phase behavior tests. The initial lower and upper salinities, Csei and Cseu, may be the same as those in the pipette tests. 

The experimental data for this example are those shown earlier in Table 7.2, and the solubilization data (V Afs = C23/C33 and V Afs = Cu/Css) are shown in Figure 7.10. In the phase behavior tests, the surfactant concentration is 1 wt.% that is treated approximately as vol.%. The water/oil ratio is 1. Find the surfactant phase behavior parameters required in simulation C33maxo, C33maxi/ C33max2, Qpl Qpr/ Csei, and Cse . 

As with liquid systems, the general effect of pressure on phase behavior is negligible (Nelson, 1983). In practice, dead oils are used in phase behavior tests. Therefore, pressure effect is not investigated, although the reservoir temperature is maintained in phase behavior tests. However, different pressure causes a different amount of gas dissolved in the oil. In such cases, the pressure would have some effect. High-pressure PVT cells are needed for such phase behavior tests. 

When we introduced phase behavior tests earlier, we mentioned aqueous stability tests. The main objective of aqueous stability tests is to eliminate the surfactant precipitation problem. As we already know, the solubility of surfactant decreases with salinity. During aqueous stability tests, the surfactant solution becomes opaque up to some salinity, showing the surfactant starts to aggregate or even precipitate. When divalent or multivalent ions exist in the solution, the salinity needed to start precipitation is much lower. 

PHASE BEHAVIOR TESTS FOR THE ALKALINE-SURFACTANT PROCESS... 

Phase behavior tests performed in glass sample tubes (pipettes) for the alkaline-surfactant process include aqueous tests, a salinity scan (alkalinity scan), and an oil scan. The aqueous tests and salinity scan are the same as those for surfactant flooding. For the sahnity scan in AS or alkaline-surfactant-polymer (ASP) cases, alkali also works as salt. There are two ways to change salinity. One is to change the salt content while fixing the alkali content the other is to change the alkali content while fixing the salt content. Therefore, the salinity... 

To begin this simulation, we first need to set up an EQBATCH model. The difference between a phase behavior model and a flow model of an alkaline-surfactant system is that the matrix does not exist in the phase behavior test tube thus, there is no ion exchange on the matrix in the phase behavior model. Therefore, in the phase behavior model, we define 6 elemenfs and 14 fluid species based on Example 10.4 and remove Ihe calion exchanges only on fhe malrix. In particular, we keep fhe solid species Ca(OH)2(s) and CaC03(s). Af leasl one advantage is that we can ensure that there should not be any solid precipitation in the model, or any precipitation should be consistent with the observation in the test tube. The rest of the procedures to set up the EQBATCH model are similar to those in Example 10.4. 

Micellar flooding is a promising tertiary oil-recovery method, perhaps the only method that has been shown to be successful in the field for depleted light oil reservoirs. As a tertiary recovery method, the micellar flooding process has desirable features of several chemical methods (e.g., miscible-type displacement) and is less susceptible to some of the drawbacks of chemical methods, such as adsorption. It has been shown that a suitable preflush can considerably curtail the surfactant loss to the rock matrix. In addition, the use of multiple micellar solutions, selected on the basis of phase behavior, can increase oil recovery with respect to the amount of surfactant, in comparison with a single solution. Laboratory tests showed that oil recovery-to-slug volume ratios as high as 15 can be achieved [439]. 

Figure 2 shows the test tube aspect of a salinity scan with an anionic surfactant at a concentration about 1 wt. % and for WOR = 1. hi all test tubes the surfactant, oil, alcohol, and temperature are the same, i.e., in Eq. 4 all values are set but sahnity. The test tube that exhibits three-phase behavior corresponds to the salinity S = 2.2% NaCl, so-called optimum sahnity in this case, which satisfies HLD = 0 according to Eq. 4. 

The absolute value of the characteristic parameter of the surfactant a can be estimated from a single experiment by using Eq. 4 for HLD = 0 if all other variables values are known. For instance in the example of Fig. 2 scan oil ACN = 6 for hexane, 3 vol% 2-butanol/(A) = - 0.16, temperature 25 °C, and since the three-phase behavior is exhibited for the test tube with aqueous phase salinity S = 2.2% NaCl, then the surfactant parameter value is ct = 0.32. 

In their test system, the researchers used the ionic liquid l-butyl-3-methylimidazol-ium hexafluorophosphate (bmim)(PF6), which is stable in the presence of oxygen and water, with naphthalene as a low-volatility model solute. Spectroscopic analysis revealed quantitative recovery of the solute in the supercritical CO2 extract with no contamination from the ionic liquid. They found that CO2 is highly soluble in (bmim)(PF6) reaching a mole fraction of 0.6 at 8 MPa, yet the two phases are not completely miscible. The phase behavior of the ionic liquid-C02 system resembles that of a cross-linked polymer-solvent system (Moerkerke et al., 1998), even though... 

An interesting investigation of the ternary mixture H2S + C02+CH4 was performed by Ng et al. (1985). Although much of this study was at temperatures below those of interest in acid gas injection, it provides data useful for testing phase-behavior prediction models. The multiphase equilibrium that Ng et al. observed for this mixture, including multiple critical points for a mixture of fixed composition, should be of interest to all engineers working with such mixtures. It demonstrates that the equilibria can be complex, even for relatively simple systems. 

It should be noted that the field tests were made with only one type of surfactant, and without benefit of many recent research advances in such areas as high-pressure phase behavior and surfactant design, mechanisms of dispersion formation and disappearance, and mechanisms of dispersion flow through porous media. Furthermore, the design and successful performance of field tests pose many technological challenges in addition to those encountered in the prerequisite experimental and theoretical research. 

More field tests will be needed, especially to incorporate research advances in such areas as materials design phase behavior and dispersion morphology mechanisms of dispersion formation, flow, and breakdown and simulation of dispersion-based sweep control. 

After each step of auxiliary phase deposition, the PEVD process was stopped for sensor response behavior testing by opening Gate A (Eigure 20b). Under the open circuit condition, the EME of the sensor was indicated by the electrometer. A high flow rate at both sides remained until the equilibrium EME value of the sensor, zero in this case, was reached. 

Computational quantum mechanics continues to be a rapidly developing field, and its range of application, and especially the size of the molecules that can be studied, progresses with improvements in computer hardware. At present, ideal gas properties can be computed quite well, even for moderately sized molecules. Complete two-body force fields can also be developed from quantum mechanics, although generally only for small molecules, and this requires the study of pairs of molecules in a large number of separations and orientations. Once developed, such a force field can be used to compute the second virial coefficient, which can be used as a test of its accuracy, and in simulation to compute phase behavior, perhaps with corrections for multibody effects. However, this requires major computational effort and expert advice. At present, a much easier, more approximate method of obtaining condensed phase thermodynamic properties from quantum mechanics is by the use of polarizable continuum models based on COSMO calculations. 

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