Hydrocarbons, properties/recovery

Basic to establishing whether power recovery is even feasible, let alone economical, are considerations of the flowing-fluid capacity available, the differential pressure available for the power recovery, and corrosive or erosive properties of the fluid stream. A further important consideration in feasibihty and economics is the probable physical location, with respect to each other, of fluid source, power-production point, and final fluid destination. In general, the tendency has been to locate the power-recoveiy driver and its driven unit where dictated by the driven-unit requirement and pipe the power-recoveiy fluid to and away from the driver. While early installations were in noncorrosive, nonerosive services such as rich-hydrocarbon absorption oil, the trend has been to put units into mildly severe seiwices such as amine plants, hot-carbonate units, and hydrocracker letdown. 

Very recently , we have carried out an intercomperison study of hquid-hquid extraction (LLE) and sorption on polyurethane foam (PUF) and Amberlite XAD-2 for the analysis of aliphatic, aromatic and chlorinated hydrocarbons dissolved in seawater. The application of these methods, sampling in parallel the same body of water, has shown significant differences in the recovery of higher molecular weight components in the complex mixtures of both aliphatic and aromatic hydrocarbons. These are attributed to selective associations of these hydrophobic species with macromolecular organic matter such as fulvic and humic acids and to the effects of the dissolved organic molecules on adsorbent properties. 

In all of these attempts at a definition or classification of petroleum, it must be remembered that petroleum exhibits wide variations in composition and properties, and these variations not only occur in petroleum from different fields but may also be manifested in petroleum taken from different production depths in the same well. The mixture of hydrocarbons is highly complex. Paraffinic, naphthenic, and aromatic structures can occur in the same molecule, and the complexity increases with boiling range of the petroleum fraction. In addition, petroleum varies in physical appearance from a light-colored liquid to the more viscous heavy oil. The near-solid or solid bitumen that occurs in tar sand deposits is different from petroleum and heavy oil, as evidenced by the respective methods of recovery (Speight, 1999,2000). 

The large supply of tall oils and the well-known surface properties of many of the components have led to several suggestions to use them or their derivatives in micellar flooding (X58.5 9.). However, there are, so far as we know, no extensive laboratory investigations underway nor plans to test these possibilities in the field. In view of the contribution tall oils might make to enhanced recovery if they could be used, a survey of interfacial tension properties of aqueous/hydrocarbon systems, similar to those which have become common with the petroleum sulfonate and other surfactants under consideration for micellar floods, seemed worthwhile. 

In this chapter the properties of nonaqueous hydrocarbon foams will be reviewed and the effects of foam formation on flow of oil—gas mixtures in porous media will be discussed A laboratory technique for investigating the role of foamy-oil behavior in solution gas drive is described, and experimental verification of the in situ formation of non-aqueous foams under solution gas drive conditions is presented The experimental results show that the in situ formation of nonaqueous foam retards the formation of a continuous gas phase and dramatically increases the apparent trapped-gas saturation. This condition provides a natural pressure maintenance mechanism and leads to recovery of a much higher fraction of the original oil in place under solution gas drive. 

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