Chapter 6 Organic Constituents in Saline Waters

Chapter 6.

ORGANIC CONSTITUENTS IN SALINE WATERS

Water is a peculiar solvent and has been considered t o possess at ambient temperature a quasi-crystalline, open structure which will allow solute molecules to fill the space between the lattice points (Eley, 1939). As a nonpolar molecule dissolves in water at ambient temperature, the structure of the water in its immediate vicinity becomes more crystalline, or a microscopic “iceberg” surrounds the solute (Frank and Evans, 1945). Water also has been considered t o be an equilibrium mixture of an icelike and a close-packed structure, and with a molecule of gas as a solute, it reacts with the icelike structure filling one of the cavities to form a gas-hydrate and shifting the equilibrium from the close-packed structure to the icelike structure (Namoit, 1961). Another theory is that water is composed of clusters of highly hydrogenbonded molecules which are surrounded by a closely packed structure of monomeric water. These flickering clusters form and dissolve perpetually as a result of local energy fluctuations. Therefore, a water molecule can have a solute molecule as a neighbor along with its four H-bonded water neighbors. Interactions between the solute and water molecules will depress the energy level of the tetrabonded water molecule. However, large numbers of water molecules surround an unbonded molecule, and if it acquires a solute neighbor after the latter replaces a water molecule, the energy level is raised. Changes in the energy levels cause a shift of water molecules between various levels in accordance with the Boltzmann distribution law, giving an increase in the “icelikeness” and an increase in the clusters of water molecules near the surface of the solute molecule (Nemethy and Scheraga, 1962). When a hydrocarbon molecule transfers from the pure liquid to the solution hydrocarbon-water, interactions are established while hydrocarbonhydrocarbon interactions are broken. The amount, kind, and state (suspended, dissolved, or colloidal) of organic matter in petroleum-associated waters is important in determining the origin and migration of petroleum, and in problems concerning pollution of fresh waters by petroleumassociated waters. Probably the most plausible theory concerning the origin of petroleum is that it originated from organic constituents which are recognized as remnants or degradation products of living organisms of past ages; these organic source materials entered fine-grained aquatic sediments where biochemical and chemical conversions and fractionations occurred (Erdman, 1965). As increased sedimentation took place, the resulting overburden pressure and compaction caused the interstitial water, which con-

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tained minute quantities of hydrocarbon, to be squeezed out of the consolidating sediments, and subsequently the oil was accumulated in sands and left behind in structural traps (Kidwell and Hunt, 1958). Obviously, the waters associated with petroleum play a very important part in the origin, migration, accumulation, and subsequent production of petroleum - the accumulation and production of petroleum being totally dependent upon hydraulic flow in response to geostatic and hydrostatic pressures. Consider briefly that 99% of the oil found and produced typically occurs within the pore spaces of sedimentary rocks (Hedberg, 1964).About 59% of the production comes from sandstone reservoirs, 40% from carbonates, and 1% from other types of rock. Petroleum in igneous and metamorphic rocks occurs primarily in fracture pore spaces and probably has migrated to these rocks from its place of origin. The solubilities of petroleum hydrocarbons in water increase with temperature and decrease as the salinity of the water increases. A temperature drop from 150” t o 25°C reduces the solubility of petroleum in water by a factor of 4.5-20.5. Such a mechanism can account for the accumulation of petroleum because as upward moving subsurface waters containing dissolved hydrocarbons decrease in temperature and pressure and meet more saline waters, they will release dissolved hydrocarbons (Price, 1973). Information concerning dissolved organic matter in sea water was published as early as 1892 (Duursma, 1965). Palmitic acid, stearic acid, acrolein, and organic nitrogen were tentatively identified. The dissolved organic matter was found t o be about 2 mg/l in the open sea, increasing to about 15 mg/l in water taken near the coast of Greece, all of which was attributed t o saponification of the fats of dead organic organisms. Phytoplankton organisms comprise most living marine organic matter, 10% of which eventually becomes animal matter. The bulk of the organic particulate matter in the sea results from dead animal matter, but the dissolved organic constituents appear to be derived from dead phytoplankton and detritus rather than excretions from living cells. Decomposition of organic matter results primarily from the activities of heterotrophic bacteria. Organic matter decomposes more rapidly in a nearshore environment, where there is an abundance of such matter and bacteria, than in a deep-sea environment, where both the matter and bacteria are diluted. The dissolved organic matter can be classified into groups as follows: (1)nitrogen-free (for example, carbohydrates); (2)nitrogen-containing (for example, proteins); (3)lipids (for example, esters of fatty acids); and (4) complexes comprised of mixtures of the preceding three groups (for example, humic acids). Nitrogen-free organic compounds

Many petroleum-associated waters contain methane; however, in Japan, there is a type of natural-gas deposit called “suiy6sei-tenynengasuy’, a dry gas,

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which is found dissolved in subsurface brines (Marsden and Kawai, 1965). The major reservoirs in which it is found are marine or lagoonal sedimentary basins with thick sediments and of wide areal extent. Some of the associated brines contain more than 80 mg/l of iodide, which is the only commercial source of iodine in Japan. Some of these brines also contain dissolved ethane, propane, isobutane, butane, isopentane, and pentane. An interesting note is that large Soviet deposits of natural gas in a solid state totaling about 15 trillion m3 were reported to the U.S.S.R. Committee for Inventions and Discoveries. According to U.S.S.R. investigators, molecules of ground water attract molecules of natural gas and convert them to a hydrate, which resembles silvery-grey ice, where the pressure is 250 atm and the temperature 25°C or less. 1m3 of the hydrate contains up t o 200 m3 of natural gas. These solid hydrate deposits are found in permafrost zones at depths to 2,500 m. Because of the high electrical resistance, they are discoverable by geophysical methods. The hydrate can be converted to gas by sinking a well and reducing the pressure and/or pumping a catalyst such as methyl alcohol into it (Anonymous, 1970). The solubility of the hydrocarbons benzene, toluene, o-xylene, rn-xylene, p-xylene, naphthalene, biphenyl, diphenylmethane, and phenanthrene was found t o increase with increasing silver-ion concentration, indicating that a slightly soluble 1-1complex formed (Andrews and Keefer, 1949). Evidence was obtained that two water-soluble complexes formed with silver and each aromatic hydrocarbon tested. Potassium nitrate causes a reduction in the solubility of aromatics in aqueous solutions (salting-out effect), but silver nitrate increases the solubility of toluene about 73% compared to its solubility in pure water. Apparently this effect with silver ions results from the formation of n-complexes between the benzene ring and the cation. Benzene hydrocarbons exhibit a minimum solubility in water near 18°C which corresponds to a zero heat of solution. The actual volume occupied by a hydrocarbon with one benzene ring in water solution apparently influences its degree of solubility, and the larger the molecule the less soluble it is in water (Bohon and Claussen, 1951). However, naphthalene and biphenyl, which are larger in size and are multiring compounds, were 7 to 10 times more soluble, indicating that some property of the benzene ring may influence the solubility. I t was postulated that a positive heat of solution resulted in the heat of cavity formation, while a negative heat of solution resulted from the formation of icelike structures around the dissolved hydrocarbons and/or a n-electron complex of the aromatic nucleus where the n-electrons functioned as a base and the water as an acid. The heat of cavitation would predominate above 18°C and would cancel the negative heat reaction at 18°C ,and below 18°C the negative heat would be larger. A study of the effect that the salts sodium fluoride, sodium chloride, lithium chloride, ammonium chloride, sodium iodide, cesium chloride, tetramethylammonium bromide, etc., have upon the activity coefficient of benzene in aqueous solutions indicates that the salting-out effect varies con-

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ORGANIC CONSTITUENTS IN SALINE WATERS

siderably among the electrolytes (McDevit and Long, 1952). A limiting law for determining the influence of electrolytes on the activity of nonpolar solutes was developed, which related the magnitude of the salt effect t o the volume changes associated with salt and water mixing. Molecular hydrogen was found in oilfield waters in the Lower Volga region (Zinger, 1962). Up to 43%of the dissolved gas in these waters was hydrogen; other gases dissolved in the waters were methane, ethane, butane, pentane, carbon dioxide, nitrogen, helium, and argon. The pH of these waters was as low as 3.4, and the iron content was as high as 1,100 ppm. The solubility of methane increases with pressure and decreases with increased salt concentration at ambient temperature in NaC1-H2 0 and CaC12-H20 systems (Duffy et al., 1961). From the experimental data, it was estimated that 1 cubic foot of sedimentary rock with 20% porosity buried 300 m deep and saturated with a brine containing 50,000 ppm of NaCl could accommodate 0.3 mole of methane in solution. A gas-liquid partition chromatographic technique was used t o determine the solubilities of C1-C9 paraffin and branched-chain paraffins, four cycloparaffins, and five aromatic hydrocarbons in water (McAuliffe, 1963). Later this study was extended to seventeen paraffins, seventeen olefins, nine acetylenes, seven cycloparaffins, seven cycloolefins, and six aromatic hydrocarbons (McAuliffe, 1966). The data indicated that the solubilities of the hydrocarbons in water increased as unsaturate bonds were added t o the molecule, with ring closure, with addition of unsaturate bonds in the ring, and with addition of bonds which decreased the hydrocarbon molar volume. Branching increased the solubility in water for paraffin, olefin, and acetylene hydrocarbons but not for the cycloparaffin, cycloolefin, and aromatic hydrocarbons. Plots of the log of the solubility in water were a linear function of hydrocarbon molar volume for each homologous series of hydrocarbons. A capillary-cell method was used to measure the diffusion of methane, ethane, propane, and n-butane in water (Witherspoon and Saraf, 1964). At 25OC, the results indicated that the diffusion coefficients times los cm2/sec were 1.88, 1.52, 1.21, and 0.96, respectively, for methane, ethane, propane, and n-butane. The coefficients increased with higher temperatures. Near the critical solution temperature and about 300 atm, the solubility versus pressure curves for some hydrocarbon-water systems show a sharp maximum. However, pressure has a negative effect on solubility beyond this maximum, and a second two-phase region appears. The five binary hydrocarbon-water systems studied were benzene, n-heptane, n-pentane, 2-methyl-pentane, and toluene (Connolly, 1967). The accommodation of CI2-C& n-alkanes in distilled water was determined as a function of hydrocarbon supply, settling time, filtration poresize, and mode of introduction (Peake and Hodgson, 1967). Apparently it is possible to accommodate hydrocarbons in water at levels higher than solubil-

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ity levels, and such accommodation systems are stable for several days. Preferential accommodation of alkanes in the C16-C20range was found at the expense of other 'alkanes with lower and higher carbon numbers. A gas chromatographic method for the determination of petrol in water was developed whereby the petrol was extracted from the water into nitrobenzene and the extract was analyzed using a column polyethylene glycol 1,500 on silanized Chromosorb W (Jeltes-and Veldink, 1967). The methods were sensitive t o 0.1 mg/l, and for concentrations > 0.5 mg/l the precision was about 5% for the major components. Low-molecular-weight hydrocarbons in the C1-C4range were detected in sea water. Generally the concentration tended to decrease with depth (Swinnerton and Linnenbom, 1967). Methane was the most abundant hydrocarbon found, but smaller amounts of ethane, ethylene, propane, propylene, n-butane, isobutane, and some butenes also were detected and measured. Hundreds of drill-stem samples of brine from water-bearing subsurface formations in the Gulf coastal area of the United States were analyzed to determine their amounts and kinds of hydrocarbons (Buckley et al., 1958). The chief constituent of the dissolved gases usually was methane, with measurable amounts of ethane, propane, and butane present. The concentration of the dissolved hydrocarbons generally increased with depth in a given formation and also increased basinward with regional and local variations. In close proximity t o some oilfields, the waters were enriched in dissolved hydrocarbons, and up to 14 standard cubic feet of dissolved gas per barrel of water was observed in some locations. The ratio of toluene t o benzene in 27 crude oils from various sources ranged from 2.0 t o 11.3. Toluene is less soluble than benzene in distilled water, where the ratio is about 0.3 (McAuliffe, 1966). A method of prospecting for petroleum, utilizing information concerning the amount of benzene dissolved in subsurface waters, was patented (Coggeshall and Hanson, 1956). Gas chromatographic methods proved t o be good for determining the amount of benzene and other hydrocarbons in the petroleumassociated waters (Zarrella et al., 1967). Collected information indicates that the concentration of benzene in petroleum-associated water varies with different types of hydrocarbon accumulations, that the benzene concentration decreases with increasing distance from the hydrocarbon accumulation, and that benzene is specific for detecting the occurrence of petroleum hydrocarbon accumulation in a given geologic horizon. A brine sample taken from a horizon separated by 27 m of shale from an oil pool contained 0.02 ppm of benzene, indicating that low-permeability shale prevents movement of hydrocarbons. Chromatographic techniques were developed for the determination of sugars and phenols in sea waters and in sediments (Degens and Reuter, 1964). Biogeochemical differences were observed between the sugars in the sea and in the sediments.

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Wilson e t al. (1970) found that ethylene, propylene, and carbon monoxide are produced in illuminated sea water to which dissolved phytoplankton was added. Higher saturated gaseous hydrocarbons and methane were not produced. Bonoli and Witherspoon (1968) measured the diffusion coefficients of methane, ethane, propane, n-butane, n-pentane, benzene, toluene, ethylbenzene, cyclopentane, methylcyclopentane, and cyclohexane in pure water at temperatures ranging from 2" to 60°C using the capillary-cell method. The effect of sodium chloride was studied, and the largest decrease in diffusion coefficients was found for the paraffin hydrocarbons. They attributed the decrease to the effects of ions in water acting as structure breakers as well as obstacles to diffusion because of obstructions and hydrations. Hydrocarbons containing nitrogen Chromatographic techniques were developed for determining humic acids, amino acids, and indoles in saline waters and in sediments (Degens and Reuter, 1964). Arginine was found in the particulate matter in sea water and decreased in concentration with depth. Relatively abundant concentrations of ornithine, serine, and glycine were found in sea water. The total concentrations of amino acids found in some petroleumassociated waters ranged from 20 to 230 pg/l (Degens et al., 1964). In general, the amino acid content increased with salinity. Adjustment of the salinity of the brines t o that of modern sea water indicated a similarity between the amino acid spectra in the two. High concentrations of serine and the presence of threonine and phenylalanine and glutamic and aspartic acids were found in the petroleum-associated waters. It was postulated that the amino acids occurred in the petroleum waters in a combined state as nonproteinaceous acid complexes and that the solubility of these complexes probably is a function of salinity. This postulate was based on information which indicated that serine is thermally unstable. More recent information indicates that serine, lysine, threonine, glycocol, histine, isoleucine, and leucine are fairly stable up t o 180°C (Califet and Louis, 1965). Liquid-exchange chromatography was used to determine the amounts of amino acids in some saline waters (Siege1 and Degens, 1966). The results indicated the bulk of the amino acids dissolved in the sea are tied up in complexes and are not in a free form. A study of the organic solutes in sea water led t o the conclusion that coprecipitation methods are the most versatile for their isolation (Chapman and Rae, 1967). Some of the organics that can be isolated by this method include glucose, glutamic acid, aspartic acid, citric acid, succinic acid, glycollate, glycine, and lysine. The percent of recovery of these solutes by this method varied from 16 t o 90%. The method involved the coprecipitation of these organic solutes with iron or copper. Most of the nitrogen in humic acid is located in the large and intermediate

FATTY ACIDS

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size molecules, with the smallest molecules being practically nitrogen-free. This is attributed to the fact that the link involving nitrogen is more susceptible t o oxidation than the rest of the molecule. Amino acids can be released from humic acid by acid hydrolysis, alkaline hydrolysis, and reduction with sodium amalgam (Piper and Posner, 1968). A widely used procedure for concentrating and recovering trace organics is the carbon-adsorption method developed by Braus et al. (1951).A modification of this method by Robinson et al. (1967) allowed recovery of organics using three activated carbon filters in series, with the final two receiving acidified water. Krause (1962)investigated the decomposition of organic matter in natural waters and found that immediately after the death of an organism that amino acids and keto acids appeared in the water. After 24 hours of aerobic decomposition, a qualitative and quantitative maximum was reached by both groups, and the amino acids present were alanine, aspartic, glutamic, glycine, leucine, lysine, methionine, phenylalanine, serine, tyrosine, and raline; and the keto acids present were pyruvic, oc-ketoglutaric, oxaloacetic, and glyoxylic. After 10 days, the only acids that remained of the amino group were glutamic, glycine, lysine, and serine; and of the keto group, pyruvic and oc-ketoglutaric. Litchfield and Prescott (1970)analyzed sea water, and pond water, and spent algal media and found aspartic acid in all of the samples. Other amino acids frequently found were serine, glycine, alanine, and arginine. Techniques employed in the analysis were dansylation, extraction, and thin-layer chromatography . Fatty acids Ralston and Hoerr (1942) determined the solubilities of the normal saturated fatty acids from caproic to stearic acid, whose number of carbon atoms ranges from 6 to 18 in water, ethanol, acetone, 2-butanone, benzene, and glacial acetic acid from ' 0 to about 60'C. In general, the solubilities increased with increasing temperature. Free fatty acids and hydroxyl ions form when soaps hydrolyze. The rate and percentage of hydrolysis is pH dependent, generally the potassium soaps are more hydrolyzed than the corresponding sodium soaps, and free fatty acid never separates as such from pure soap solutions unless reacted with an excess of acid such as carbon dioxide (McBain et al., 1948). Quantitative recovery of organic constituents from saline waters without alteration is difficult. Temperature and pressure changes, bacterial actions, adsorption, and the high inorganic/organic constituents ratio in most petroleum-associated waters are some reasons why quantitative recovery is difficult. Some of these factors apply also to sea waters, and Jeffery and Hood (1958) evaluated five methods which proved effective for isolation of portions of the soluble organic compounds in sea water. They were: (1)

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ORGANIC CONSTITUENTS IN SALINE WATERS

dialysis or electrodialysis; (2) ion exchange;, (3) solvent extraction; (4) coprecipitation; and (5) carbon adsorption. Their results showed that the total organic material was most efficiently removed by electrodialysis or by coprecipitation with ferric hydroxide. A study of the differential uptake of organic compounds by montmorillonite and kaolinite revealed that montmorillonite adsorbed the compounds more efficiently than kaolinite. The compounds studied were aspartic acid, alanine, glucose, and sucrose (Williams, 1960). Approximately 13%of the aspartic acid was removed from solution by montmorillonite, while kaolinite removed only about 2%. The following saturated, monosaturated, and diunsaturated long-chain fatty acids were found in sea water: saturated Cl0, C12,CI4,C16,CIS,CzO,and CZ2; diunsaturated CIS; and monounsaturated CI6 and c18 (Emery and Koerner, 1961). Also isolated were CIS,C1,, and C19 acids which might or might not have been originally present. A gas chromatographic method was developed for the determination of trace amounts of the following fatty acids in water: n-valeric, isovaleric, n-butyric, isobutyric, propionic, and acetic (Emery and Koerner, 1961). The gas chromatograph was equipped with a flame ionization detector and a column of Tween 80 on Chromosorb W. The fatty acids lauric, myristic, palmitic, stearic, hyristoleic, palmitoleic, oleic, linoleic, and linolenic were identified in sea water using solvent extraction, esterification, and gas-liquid chromatography (Slowey et al., 1962). Samples of deep-sea water contained less unsaturated acids and shorter-chain acids than surface samples. Saturated straight-chain fatty acids were found in petroleum-associated waters from two reservoirs. The carbon numbers were CI4through C30.The same acids were identified in a shale-core sample from a petroleum reservoir. The even-numbered acids predominated over the odd-numbered acids in the amounts found in every case. The identification methods consisted of extraction by refluxing, esterification, gas chromatography, and mass spectrometry (Cooper, 1962). A gas chromatographic method capable of separating unesterified fatty acids was developed (Metcalfe, 1963). Acids up to CzOwere identified using a thermal conductivity detector and a column composed of phosphoric acidtreated ethylene glycol succinate polyester on Chromosorb W. Bordovskii (1965) studied the sources of organic matter in marine basins, the sedimentation of organic matter in water, and the transformation of organic matter in sediments and its early diagenesis. He also pointed out that the organic matter in water is present in true solution, as colloidal organic detritus, and as live organisms in suspension. Bacteria play an important part in altering the composition of the organic material in the aqueous phase as well as in the sediments. Wangersky (1965) found that organic carbon was present in freshly distilled water and that it survived triple distillation and distillation from

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alkaline permanganate. He correlated this with algal growth in city reservoirs and suggested that the organic carbon content of distilled water must be considered by anyone growing organisms in distilled water. He also found that bubbling sea water caused organic compounds to form aggregates on the surface and further theorized that such reactions may be related to the origin of life. Kabot and Ettre (1963) developed gas chromatographic methods capable of determining free fatty acids. They analyzed different mixtures of the normal fatty acids using both packed and Golay columns in conjunction with a flame ionization detector. They concluded that the quantitative analysis of free fatty acids is possible. Naphthenic and humic acids Davis (1968) examined the organic fractions of artesian well waters from a Texas oil-bearing Eocene age aquifer, using infrared and chromatographic methods. He found that the water coproduced with oil contained 1,000 times more naphthenic acids than water located updip from the oil. He also found a phthalic acid ester dissolved in the petroleum-associated water but concluded that it may be common t o ground waters in general. Shaborova et al. (1961) state that “the presence in subsurface waters of organic acids in the form of salts of various metals or in a free state indicates a current process of leaching of organic matter from the enclosing rock. The presence of organic acids in subsurface waters is one of the evidences for the existence in the earth’s crust of chemical processes of decomposition of preserved organic matter. In turn, the organic acids are broken down into simpler compounds by decarboxilization. It is known that decarboxilization of organic acids is accompanied by the formation of hydrocarbons. In nature, this process is a real geochemical factor. Consequently, the organic acids and their salts that are dissolved in subsurface waters can be regarded as one of the sources for the generation of hydrocarbons.” Using a steam distillation method, organic acids were found in concentrations from 663 to 2,242 mg/l in subsurface waters taken from a Kazhim stratigraphic well. The average molecular weight of the acids was from 46 to 58, and the waters taken from Devonian age sediments contained higher concentrations of the acids than waters taken from Carboniferous age sediments. Lochte et al. (1949) analyzed waters produced with high-pressure gas wells and identified the following acids: acetic, propionic, isobutyric, n-butyric, isovaleric, n-valeric, n-hexanoic, and other C6isomers. Crude oils were treated with ammonia solution followed by electroprecipitation of the aqueous phase to remove naphthenic acids (Agaev, 1961). Further isolation of the naphthenic acids was accomplished by heating the aqueous phase to decompose the ammonium salts and remove ammonia and water. Oden (1919) recognized fulvic acid, humus acid, and hymatomelanic acid

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in soils. Later, Page and Dutoit (1930) modified the name humus acid to humic acid. Sestini (1898) demonstrated that the humic acids are of complex composition and contain ethereal and anhydride components in addition to alkyl, hydroxyl, and ketonic groups. Burges (1960) suggested that humic acid is a single chemical substance or a group of similar substances, and that primarily it is nonnitrogenous. Steelink et al. (1960) fused soil humic acids and found the following degradation products: catechol, profocatechuic acid, and resorcinol. Steelink and Tollin (1962) determined the presence of two free-radical species in humic acid using an electron paramagnetic-resonance spectrometer. They believed that one could be a semiquinone radical and the other a quinhydrone radical. Fulvic acids, humic acids, and hymatomelanic acids have been found in natural waters (Wilson, 1959; Black and Christman, 1963; Packman, 1964). The brown color, characteristic of many natural waters, is attributed to complex organic compounds which probably are derived from water-soluble peptizable components of soil humus. A method that can be used t o determine the organic acids in petroleumassociated waters was published by the Natural Gasoline Association of America (1953). The water is treated with lime water to convert the organic acids to their calcium. salts, which are titrated with a standard mineral acid. Determination of oil in water The following method was developed by Nalco Chemical Company (1971) and is applicable t o waters and brines where the oily matter is hydrocarbons or hydrocarbon derivatives and all liquid or unctuous substances that have a boiling point above 90°C and are extractable from waters or brines at pH 5.0 or lower using benzene, chloroform, or carbon tetrachloride. The sample is extracted with a fluorocarbon solvent which is evaporated off in a specially designed vessel and the residual oil measured volumetrically in a microsyringe. Pear-shoped l o p , capacity opprox.17 m l , o f f s e t odditionol opening so th0t"popped" somple w i l l be r e t o i n e d

S y r i n g e , 5 0 0 kl, 10-pl divisions

Fig. 6.1.Microsyringe-evaporatingflask.

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Apparatus. The necessary apparatus consists of: (1)Microsyringe - evaporating flask (see Fig. 6.1): this assembly consists of a single-neck flask of approximately 20 ml volume which tapers opposite and slightly offset to the neck into a microsyringe equipped with a gas-tight Teflon-tipped plunger and calibrated to measure 0-500 pl. (2) 1,000-ml pear-shaped separatory funnel. (3) Hotplate or hot-water bath: capable of being controlled in the range of 45O-55'~ at * ~ O C . (4) 500-ml Berzelius, tall form beaker. Reagents. The necessary reagents are: (1)50%hydrochloric acid solution, reagent-grade. (2) pH paper indicating strip or pH meter. (3) 1,1,2-trichlorotrifluoroethane(Freon TF) reagent-grade, purified, 48OC boiling point. Sampling. Collect a composite or spot sample representative of stream to be measured. Volume to be taken will be dependent on content of oily material and should be in the range of 1-5 liters. Sample should be caught in glass container. Procedure. Extraction: adjust pH of entire sample t o pH 5 or below using hydrochloric acid added in small increments. Thoroughly mix the sample and allow it t o stand 15 minutes. Measure the volume of entire sample and transfer to separatory funnel. Add portion of 1,1,2-trichlorotrifluoroethane extraction fluid (see Note 1) to sample container, thoroughly rinsing any adhering oil material. Add this and balance of fluorocarbon to separatory funnel. Shake thoroughly for 5 minutes and let stand t o separate layers. Draw off fluorocarbon layer into suitable beaker, filtering any entrained solids, if necessary, and warm gently to boiling point (see Note 2). Continue boiling until volume remaining can be contained in measuring flask. Transfer to measuring flask with fluorocarbon rinse of beaker, and immerse the flask and contents into 500-ml beaker partially filled with water and warmed to 65°C on hotplate or in hot-water bath. Be sure open neck of flask is clear of upper edge of beaker (can be maintained by extension of syringe piston). Continue until volume is reduced to that of syringe volume. Draw fluid into syringe and increase heat slowly t o remove last traces of solvent, indicated by lack of bubbles forming in the syringe column. Measure amount of oil material in graduated syringe using graduations midway in syringe. Note 1: for single extractions fluorocarbon volume should be one-tenth of the original sample volume. In double extractions for better accuracy and reproducibility use two volumes of fluorocarbon, each onetwentieth of the original sample volume. Note 2: although fluorocarbon is essentially considered nontoxic, the

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evaporation of the solvent should be done in a well-ventilated area or under an exhaust hood with adequate draft to handle high-density vapors.

Calculation : 1-11measured = mg/l oily matter mi sampIe

c

Organic acids in oilfield brines This method measures the bulk of the organic acid salts in oilfield waters.

Reagents and apparatus. Acetone; NaOH, 0.02N; HC1, 0.05N; acetic acid, 10 mg/l; a hotplate; and a standard pH meter. Procedure. Pipet 25 ml of filtered brine into a 250-ml beaker; add 25 ml of acetone and adjust the pH t o precisely 6. Titrate the sample to a pH of 3.5, and record the amount of 0.05N HC1, used in the adjustment from pH 6 to 3.5. Boil the solution for 5 minutes. Cool and titrate back to pH 6 with 0.02N NaOH. Make a blank determination for NaOH and HC1. To calculate, subtract blank from NaOH and HC1 titrations. Calculation: (ml HC1 x HC1 N ) - (ml NaOH x NaOH N ) x 60,030 = mg/l organic acids ml sample as acetic acids. References Agaev, A.A., 1961. Separation of ammonium salts of naphthenic acids from crude oil in an electric field. Izv. Vyssh. Uchebn. Zaved., N e f t Gaz, 4:95-98 (in Russian). Andrews, L.J. and Keefer, R.M., 1949. Cation complexes of compounds containing carbon-carbon double bonds, 11. The solubility of cuprous chloride in aqueous maleic acid solutions. J. A m, Chem. Soc., 71 :2379-2380. Anonymous, 1970. Solid natural gas discovered. Ind. Res., 12:70. Black, A.P. and Christman, R.F., 1963. Chemical characteristics of fulvic acids. J. A m . Water Works Assoc., 55:897-912. Bohon, R.L. and Claussen, W.F., 1951. The solubility of aromatic hydrocarbons in water. J. A m . Chem. Soc., 73:1571-1578. Bonoli, L. and Witherspoon, P.A., 1968. Diffusion of paraffin, cycloparaffin, and aromatic hydrocarbons in water and some effects of salt concentration. In: Advances in Organic Geochemistry - Proc. 4th Int. Meet. Org. Geochem., Amsterdam. Pergamon Press, New York, N.Y., 9:16-18. Bordovskii, O.K., 1965. Accumulation and transformation of organic substance in marine sediments. Mar. Geol., 3:3-114. Braus, H.,Middleton, F.M. and Walton, G., 1951. Organic chemical compounds in raw and filtered surface waters. Anal. Chem., 23:1160-1164.

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