Effect of Composition on Wax Precipitation

Effect of composition on wax precipitation. Wax precipitation is often measured using the stock-tank oil at atmospheric pressure. When some gas is dissolved into the crude oil, the cloudpoint temperature may decrease, which is desirable. Low cloudpoint temperature implies that one may be less concerned about wax precipitation. 

A very clear effect of composition on CPT can be seen from the data presented in Table 5.4. The composition of the light crude oil (that is, oil 4) is shown in Table 5.5. The CPT at 38.3 bar is 318.9 K for the stock-tank oil. When 30 mole% C is dissolved in the crude oil as a result of pressure increase, the CPT is 316.8 K. The change in CPT is the result of two effects (1) pressure, and (2) composition. The pressure increase from 38.3 to 106.2 bar raises the CPT say by 0.5 K. The net effect of 

TABLE 5.4 Measured results for solvent effect on cloudpoint temperature of oil 4 (from Pan ef a/., 1997b) 

Madsen and Boistelle (1976, 1979) have measured the solubilities of wC287 nC32, in normal-alkane solvents from nC to nCj2 at atmo- 

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Let us now use the multisolid model described above to study (1) wax composition, (2) the effect of pressure, and (3) the effect of composition on wax precipitation. 

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