Petroleum acids

Crude oils generally contain less oxygen than sulfur (Table 1,5). Even though it is not abundant, oxygen can play a consequential role in particular, it is responsible for petroleum acidity. Oxygen is found in the following compounds ... 

Distillates (petroleum), acid-treated light naphthenic... 

H. L. Lochte and E. R. Littmann, The Petroleum Acids and Bases, Chapter 12. Constable, London, 1955. 

The other nitrogen compounds which are nonbasic, and are not extracted from hydrocarbons by dilute acid, have not been investigated in detail, though there are indications that they contain pyrroles. In addition, it is possible that some part of the nitrogen in this material is present in the form of amides, derived from primary or secondary amines and petroleum acids. 

Gruse and Stevens (24) list still other metallic constituents which may be present in recognizable amounts in the ash from various petroleums, including tellurium, barium, lead, manganese, chromium, and silver. According to these authors, oil-soluble salts of petroleum acids probably account for the small portions of most metallic constituents present in crude oil. 

Lochte, H. L., Our Present Knowledge of the Petroleum Acids, presented before Division of... 

SYNS ACID-TREATED HEAVY NAPHTHENIC DISTILLATE DISTILLATES (PETROLEUM), ACID-TREATED HEAVY NAPHTHENIC (9CI)... 

Sachanen (71) presents data on the occurrence of petroleum acids, which include fatty and naphthenic acids and phenols, but which are primarily naphthenic acids. The naphthenic acid contents of crude oils vary from 0.03% (Pennsylvania and East Texas) to 1.5% (California) and 1.6% (Russia and Roumania). 

Klotz (66) and Lochte (67). Dr. Lochte is preparing a book entitled Petroleum Acids and Bases publication is expected in late 1053 or early 1954. 

In aLkaline flooding, the injected aUcali reacts with the saponifiable components in the reservoir crude oil. These saponifiable components are described as petroleum acids (naphthenic acids). Naphthenic acid is the name for an unspecific mixture of several cyclopentyl and cyclohexyl carboxylic acids with molecular weight of 120 to well over 700. The main fractions are carboxylic acids (Shuler et al., 1989). Other fractions conld be carboxyphenols (Seifert, 1975), porphyrins (Dnnning et al., 1953), and asphaltene (Pasquarelli and Wasan, 1979). The naphtha fraction of the crnde oil raffination is oxidized and yields naphthenic acid. The composition differs with the crude oil composition and the conditions dnring raffination and oxidation (Rndzinski et al., 2002). 

First, define the elements, independent species, dependent species, solid species, adsorbed cations on matrix, and surfactant-associated cations, based on the compositions shown in Table 10.8. These defined elements and species are listed in Table 10.9. This is a critical step in building an alkaline model. For this case, 6 elements (N = 6), 6 independent species and 8 dependent species with a total of 14 fluid species (] = 14), 2 solid species (K = 2), 3 adsorbed cations on matrix (I = 3), and 2 surfactant-associated cations (M = 2) are defined. Note that the subscripts a and s for CafOH), and CaCO, mean in aqueous and solid states, respectively. A, FIAo, and HA represent petroleum acid anion, petroleum acid in oleic phase, and petroleum acid in aqueous phase, respectively. The last fluid species must be F1A . In principle, we can arbitrarily select N independent species. Practically, we select the species that are similar to the elements, and they are simple species so that other dependent species can be defined from them with equilibrium constants. Chlorine is a nonreactive species therefore, it is not selected as an independent species. Of course, it will not appear in any reaction equation. 

The concentrations from the formation water analysis are good initial concentrations for these elemental fluid species. Thus, the two sets of initial input data are the same. The total amount of the element A (petroleum acid) is the same as that in oil. We showed in Example 10.3 that the acid number of 0.81 g KOH/g rock is converted to 0.019 eq/L water. The input value is equal to the output value for each set of initial concentrations. Most of the hydrogen is in water, which is about 1000 g/L/(18 g/mole) 2 = 111.11 moles/L. Thus, the input and output values should be very close to this value. For a similar reason, the input and output values of sodium are close to each other. The concentrations of... 

Figure 10.26 shows the profiles of petroleum acids in water and oil phases, HA and HAo, at 0.9 PV injection. Both of the concentrations are converted to the volume fractions in water phase volume. These two profiles parallel each other. HA v is almost four orders of magnitude lower than HA . Near the injection end, these two concentrations are lower because some acid components are dissociated as soap thus, the acid components is depleted. 

The purpose of an activity map is to show at what range of concentrations in a system and how a chemical flood will work. For a given reservoir where the temperature, composition of crude oil, and residual oil saturation are fixed, five kinds of variables are under our control types of alkalis, concentrations of alkalis, types of surfactants, concentrations of surfactants, and salinity. Another important variable that is not under our direct control is the type and amount of petroleum acid that will convert to soap when contacted by the alkalis. As discussed earlier, the amount of soap will determine the concentrations of alkali and surfactant injected. In other words, to generate an activity map, we have to know the amount of soap that can be generated. Because the alkali concen-ttation typically is much greater than that required to convert all the petroleum acids in the oil to soap, the petroleum soap concentration (meq/L) is calculated... 

Parameters, such as soap mole fraction Xsoap—a fraction of petroleum acid converted to soap, are not the direct output parameters from a UTCHEM model. Before we investigate alkaline-surfactant phase behavior, we need to know how to calculate soap-related parameters. Table 12.3 lists the parameters related to soap and surfactant that are calculated or from the UTCHEM output files. These data are for the base case. This table helps us to understand the relationships of these parameters. 

Effect of Partition Coefficient and Dissociation Constant In the base case, the fraction of petroleum acid converted to soap (A/HA) is only 0.246, and the soap molar fraction is 0.309 (see Table 12.4). These values are affected by the partition coefficient Kd between water and oil and the acid dissociation constant Ka. Now let us see how sensitive these two parameters are. The data in Table 12.5 show that Kd is insensitive, whereas Ka is very sensitive. As Ka is increased, more acid is converted to soap. Accordingly, the soap molar fraction in the total surfactant becomes higher. As Xsoap is increased from the base case, the type III salinity limits are closer to those for the soap, which are lower. Thus, the mixture surfactant system becomes type II. As Xsoap... 

The thin film fonned between two approaching droplets is considered as a model emulsion system. The thinning of these films and their resistance to rupture is considered to be of great significance in understanding the behavior of emulsions. In our studies, we employed an electrical method to measure the film lifetime and thickness of model oils and crude oils. Through this, we probed the important roles that petroleum acids and asphaltenes play in the stability of crude oil emulsions. 

In our study the crude oil came from Shengli Oil Field (Shandong, China). The oil had an acid number of 2.98 mg KOH/g crude oil, a density of 0.9518 g/mL at 25°C, a weight percent of 32.5% for resin, and a weight percent of 4.2% for asphaltenes. In our experiments the crude oil and its fractions used were classified in following categories (1) crude oil, (2) crude oil with asphaltenes removed (deasphaltenes oil), (3) crude oil with petroleum acids removed (deacids oil), and (4) crude oil with both asphaltenes and petroleum acids removed (deasphaltenes and deacids oil). They were treated as described by Shaw and Stapp [61]. 

There exist natural surface-active substances in crude oil, such as petroleum acids and asphaltenes. The ionized acids formed by the reaction between the petroleum acids and the alkali can decrease the interfacial tension [1,5-7] and accelerate the thinning and breakdown of the film. At the same time, the asphaltenes can adsorb on to the interface and improve the stability of the film. When the film thickness is small enough (< 100 nm), it can keep this value for a long time because of the stabilization of the asphaltenes in the oil. In our study, almost all crude oil/alkali systems have this drainage process, and the crude oil/brine systems do not show it. So we can conclude that the drainage is correlated with the components, which have the interactions with alkaline solutions. 

The results in Table 7 show that the film lifetimes become shorter with increasing concentration of petroleum sulfonate (LH). The role LH plays in this case is similar to that of petroleum acids. 

Distillates (petroleum), acid-treated, medium heavy Distillates (petroleum), acid-treated, middle. See Petroleum distillates, acid-treated middle... 

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