Phase behavior salinity scan test

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. 

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... 

Based on this concept, a crude oil/surfactant/brine system should have phase behavior (e.g., optimum salinity, IFT minima) similar to that of the pure alkane/ surfactant/brine system whose ACN is the same as the crude EACN. However, the concept of EACN is not practically applicable for several reasons. First, all the hydrocarbon compositions of a crade oil are not readily identified. Thus, the EACN of a crude oil cannot be calculated directly using Eq. 7.79. Second, measurement of the EACN of a crude oil requires a series of surfactant solutions to be tested to obtain individual minimum ITT. Then these surfactant solutions are tested against increasing alkane carbon numbers to find minimum IFTs. The ACN at which a surfactant solution also gives the lowest IFT for the crude oil is the EACN of the oil. Finding it is not an easy task. Third, several parameters affect the value of the EACN. Variations in EACN with alcohol cosolvent type, total WOR of the sample, and crude oil composition have been observed (Tham and Lorenz, 1981). In practice, we always select surfactants by scan tests using the actual crude oil for a specific application. 

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... 

Although EO and PO-EO sulfonates and sulfates have been used in field tests, no systematic phase studies of these systems are presented in the literature, especially at reservoir conditions. Maerker and Gale [12] observed that the PO-EO-sulfates designed for the Loudon field showed a normal phase behavior using diesel oil, but a nonclassical phase behavior using crude oil in a salinity scan. It appears to be a general trend that these surfactants have low ability to form middle phases at low surfactant concentration. 

---