Crude oil stabilization

Absorber oil then flows to a still where it is heated to a high enough temperature to drive the propanes, butanes, pentanes and other natural gas liquid components to the overhead. The still is similar to a crude oil stabilizer with reflux. The closer the bottom temperature approaches the boiling temperature of the lean oil the purer the lean oil which will be recirculated to the absorber. Temperature control on the condenser keeps lean oil from being lost with the overhead. 

Process design for all plants is similar (Fig. 5). The typical Jay treating plant consists of three major parts (1) primary separation and crude-oil stabilization, (2) gas treating, and (3) sulfur recovery. ... 

The main objective in processing crude oil from the production well is to separate it into three phases—gas, oil, and water. Keeping this in mind, all processing is indeed simple. All successful operations are based on making the crude oil vapor pressure acceptable for pipeline transmission and removing sufficient water for the pipeline transmission. Conditioning the vapor pressure or degassing with crude water removal (dehydration) is commonly called crude oil stabilization. 

Crude oil stabilization is thus the major process quest of all surface facility processing. Crude oil flows into a first-stage separator from the wellhead gathering pipeline. A typical crude oil stabilization process train is shown in Fig. 4.1. Please note that this is a three-stage... 

Bridie et al. (1) found that asphaltenes are two to five times more effective than waxes as stabilizing agents. In a stable emulsion containing 6.6% asphaltenes and 9.8% wax, the emulsion was still stable if 90% of asphaltenes were removed. Waxes as crude oil stabilizers for North Sea crudes have been investigated by Thompson et al. (133, 134) who showed that waxes melt as the temperature increases, and separation efficiency increases at 60°C, which is above the wax melt temperature. 

Electrostatic stabilization occurs when the interfacial components are charged and the electric double layer between two or more droplets overlap. The resulting repulsive force counteracts further drainage of the film. Authors have, however, disregarded this repulsion as a significant stabilizing factor in describing water-in-crude oil stability (5, 6). 

The aim of this book is to discuss the many topics related to crude oil. It includes five sections. The first section deals with asphaltenes-these are natural surfactants that stabilize petroleum emulsions. The chapters of the second section discuss some advanced methods used in characterization of crude oil and it s components. The third section includes and publishes new discoveries and improvements in crude oil biology. The fourth section discusses the natural components presented in crude oil and those factors affecting crude oil stability. The final chapter involves some innovative ideas and concepts related to the crude oil. 

The method selected for crude stabilization depends upon a number of factors, principally economics and sales specifications. A crude oil stabilizer will almost always result in increased liquid recovery, but the capital investment and operating costs are correspondingly higher. Some factors that favor the installation of a crude stabilizer are ... 

The calculations involving crude oil stabilizer design are much more complicated and should be done using a suitable computer program. 

Reid vapor pressure, bar Vapor pressure crude oil, bar Vapor pressure gasoline, bar R crude oil R stabilized gasoline... 

Knowledge of a crude oil s overall physical and chemical characteristics will determine what kind of initial treatment —associated gas separation and stabilization at the fi ld of production— transport, storage, and of course, price. 

An important industrial example of W/O emulsions arises in water-in-crude-oil emulsions that form during production. These emulsions must be broken to aid transportation and refining [43]. These suspensions have been extensively studied by Sjoblom and co-workers [10, 13, 14] and Wasan and co-workers [44]. Stabilization arises from combinations of surface-active components, asphaltenes, polymers, and particles the composition depends on the source of the crude oil. Certain copolymers can mimic the emulsion stabilizing fractions of crude oil and have been studied in terms of their pressure-area behavior [45]. 

In almost all cases the molecules have a higher value as liquid than as gas. Crude oil streams typically contain a low percentage of intermediate components. Thus, it is not normally economically attractive to consider other alternatives to multistage separation to stabilize the crude. In addition, the requirement to treat the oil at high temperature is more important than stabilizing the liquid and may require the flashing of both intermediate and heavy components to the gas stream. 

This input to design refers to the long-term stability of the raw material sources for the plant. It is only of importance where the raw materials can or do contain impurities which can have profound effects on the corrosivity of the process. Just as the design should cater not only for the norm of operation but for the extremes, so it is pertinent to question the assumptions made about raw material purity. Crude oil (where HjS, mercaptan sulphur and napthenic acid contents determine the corrosivity of the distillation process) and phosphate rock (chloride, silica and fluoride determine the corrosivity of phosphoric acid) are very pertinent examples. Thus, crude-oil units intended to process low-sulphur crudes , and therefore designed on a basis of carbon-steel equipment, experience serious corrosion problems when only higher sulphur crudes are economically available and must be processed. 

Oil-in-water emulsions provide a cost-effective alternative to the methods mentioned previously, namely, heating or diluting. A typical transport emulsion is composed of 70% crude oil, 30% aqueous phase, and 500 to 2000 ppm of a stabilizing surfactant formulation [1497]. Nonionic surfactants are relatively insensitive to the salt content of the aqueous phase ethoxylated alkylphenols have been used successfully for the formation of stable emulsions that resist inversion. 

Water-in-oil macroemulsions have been proposed as a method for producing viscous drive fluids that can maintain effective mobility control while displacing moderately viscous oils. For example, the use of water-in-oil and oil-in-water macroemulsions have been evaluated as drive fluids to improve oil recovery of viscous oils. Such emulsions have been created by addition of sodium hydroxide to acidic crude oils from Canada and Venezuela. In this study, the emulsions were stabilized by soap films created by saponification of acidic hydrocarbon components in the crude oil by sodium hydroxide. These soap films reduced the oil/water interfacial tension, acting as surfactants to stabilize the water-in-oil emulsion. It is well known, therefore, that the stability of such emulsions substantially depends on the use of sodium hydroxide (i.e., caustic) for producing a soap film to reduce the oil/water interfacial tension. 

Crude oils contain various amounts of indigenous surface-active agents that stabilize water-in-oil emulsions. Therefore crude oils may stabilize such emulsions. It has been shown that the effectiveness of a dispersant is dependent on both the dispersant type and the specific crude oil [309]. However, there is no apparent correlation between the degree of emulsion-forming tendency of the crude oil, which is a function of the indigenous surfactant content, and the effectiveness of the dispersant. In general, indigenous surfactants in crude oil reduce the effectiveness of the dispersant, but to an unpredictable level. 

This has been verified for polydimethylsiloxanes added to crude oils. The effect of the dilatational elasticities and viscosities on crude oil by the addition of polydimethylsiloxanes is shown in Table 21-1. Under nonequilibrium conditions, both a high bulk viscosity and a surface viscosity can delay the film thinning and the stretching deformation, which precedes the destruction of a foam. There is another issue that concerns the formation of ordered structures. The development of ordered structures in the surface film may also stabilize the foams. Liquid crystalline phases in surfaces enhance the stability of the foam. 

The stabilization of water-oil emulsions happens as a result of the interfacial layers, which mainly consist of colloids present in the crude oil—asphaltenes and resins. By adding demulsifiers, the emulsion breaks up. With water-soluble... 

To mitigate the effects of corrosion resulting from the presence of salts, it is advantageous to reduce the salt concentration to the range of 3 to 5 ppm. Typically, brine droplets in crude oil are stabilized by a mixture of surface-active components such as waxes, asphaltenes, resins, and naphthenic acids that are electrostatically bound to the droplets surface. Such components provide an interfacial film over the brine droplet, resulting in a diminished droplet coalescence. Adding water to the crude oil can decrease the concentration of the surface-active components on the surface of each droplet, because the number of droplets is increased without increasing component concentration. 

I. C. Callaghan, C. M. Gould, R. J. Hamilton, and E. L. Neustadter. The relationship between the dilatational rheology and crude oil foam stability 1. Preliminary studies. Colloids and Surfaces, 8(1) 17-28, November 1983. 

M. Feustel, M. Krull, and H. J. Oschmann. Additives for improving the cold flow properties and the storage stability of crude oil (Additive zur Verbesserung von KaltflieBeigenschaften und Lagerstabilitat von Roholen). Patent WO 0196503, 2001. 

The major problem in demulsifying crude oil emulsions is the extreme sensitivity to demulsifier composition. There have been attempts (2, 3) to correlate demulsifier effectiveness with some of the physical properties governing emulsion stability. However, our understanding in this area is still limited. Consequently, demulsifier selection has been traditionally based on a trial and error method with hundreds of chemicals in the field. 

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