(Table VIII). In the range studied a 10 “C rise in temperature roughly doubles the reaction rate.
Table IX. Rates of Decomposition of NChloroethanolamine in Neutral Media kexp~~/mln-’
PH
x 2.9 x 3.4 x
7.91 7.67
3.5
6.88
10-5 10-5
We acknowledge the helpful suggestions made by the reviewers.
10-6
[CIO-] = 0.897X 10-3M, [EA] = 0.1 M, [NaCIO4] = 1 M, T = 25 O C .
creases with pH. For the range pH 10.3-12.5 we find the linear relation log heXptl= 0.86 X pH - 13.26
Acknowledgment
( r x y= 0.998)
Extrapolating these results suggests that the rate must be very slow in the range pH 6-8. In order to calculate the rate constant for naturally occurring conditions, experiments were carried out at pH 6.88,7.67, and 7.91 and 25 O C . The decomposition of N-chloroethanolamine under these conditions is indeed very slow. For 20 days we each day determined pH and active chlorine (by iodometry) and traced the absorption spectrum between 190 and 300 nm. The results obtained are shown in Table IX, and they show that a discrepancy exists between experimental values and those obtained by extrapolation of the data in Table VI, underlying the caution with which such extrapolation should be used in this kind of studies. Finally, the marked influence of temperature upon the rate of decomposition of N-chloroethanolamine is to be noted
L i t e r a t u r e Cited ( 1 ) Stanbro, W. D.; Smith, W. D. Environ. Sei. Technol. 1979, 13,
446. (2) Kovacic, P.; Lowery, M. K.; Field, K. W. Chem. Rev. 1970, 70, 639. (3) Chandra, M.; Bansal, 0. P. J. Inorg. Nucl. Chem. 1978, 40, 1185. (4) Chandra, M.; Lal, S.; Bansal, 0. P. J . Indian Chem. SOC.1977, 54,1040. (5) Jennings, V. J. CRC Crit. Rev. Anal. Chem. 1974,3,407. (6) Hussain, A.; Trudell, P.; Repta, A. J. J . Pharm. Sei. 1970, 59, 1168. (7) Dennis, W. H.; Hull, L. A.; Rosenblatt, D. H. J. Org. Chem. 1967, 32, 3783. (8) Feigl, F. “Spot Test in Organic Analysis”, 6th ed.; Elsevier: Amsterdam, 1960; p 349. (9) Weil, I.; Morris, J. C. J. Am. Chem. SOC.1949, 71, 1664. (10) Morris, J. C. J . Phys. Chem. 1966, 70, 3798. (11) Cachaza, J. M.; HerrBez, M. A.; Pedrares, M. D. An. Q u h 1972, 68,1341. (12) Masure, F.; Schaal, R. Bull. SOC.Chim. Fr. 1956, 1138, 1141, 1143. (13) Jacquinot-Vermese, C. C. R. Hebd. Seances Acad. Sei. 1962,254, 3679. (14) Caldin, E. F.; Crooks, J. F.; Queen, A. J. Phys. E. 1973,6,930.
Received for review April 11,1980. Accepted April 3,1981
Volatile Liquid Hydrocarbon Characterization of Underwater Hydrocarbon Vents and Formation Waters from Offshore Production Operations Theodor C. Sauer, Jr. t Department of Oceanography, Texas A & M University, College Station, Texas 77843
Underwater hydrocarbon vent and formation water samples, two discharges from offshore production operations in the Gulf of Mexico, were compositionally characterized for volatile liquid hydrocarbons (VLHs). Hydrocarbons in surface samples of an underwater vent were not detected with carbon numbers greater than 10 ( n - C l o ) . Alkanes were the major components of all of the VLHs in vent samples with less than 10% being aromatic hydrocarbons. Hydrocarbons in samples of a formation water discharge were considerably more extensive and complex than vented hydrocarbons. Total VLH concentrations were -20 mg/L, 80%of which were aromatic hydrocarbons (mostly benzene, toluene, and xylenes), close to the percentage found in coastal waters of the Gulf of Mexico. Considerable amounts of C3 and Cq alkylbenzenes (100-400 pg/L per component) were evident. Estimations of the amount of VLH discharged into the outer continental shelf of Louisiana and upper Texas from these two discharges were made for underwater hydrocarbon venting, 400 X 106-1200 X lo6 g/yr, and for formation waters, 750 X 106-1100 X 106 dyr. Present address: Exxon Production Research Co., P.O. Box 2189, Houston. TX 77001. 0013-936X/81/0915-0917$01.25/0
Introduction
Hydrocarbon venting and formation water discharges from offshore production operations are two major sources of gaseous hydrocarbons (Cl-Cj aliphatics) and volatile liquid hydrocarbons (aliphatics, C6-Cl4; aromatics-benzene, naphthalene, and alkylbenzenes; cycloalkanes alkylcyclopentanes, and alkylcyclohexanes) in coastal waters ( I 1, particularly in the Gulf of Mexico, where almost two-thirds of the world’s offshore production platforms and one-eighth of the offshore production occurred during 1976 (2). Compositional characterization of the gaseous hydrocarbon fraction of these discharges has been sufficiently studied ( I , 3 , 4 ) . However, little information is available on the full characterization of the volatile liquid hydrocarbon (VLH) fraction of these offshore discharges. Only the major components of the VLH fraction (benzene and toluene) have been identified by some authors ( 3 , 4 ) . From an environmental standpoint, this fraction of hydrocarbons is the most important because of its higher immediate toxicity to organisms than the other fractions of hydrocarbons (5-7). This paper presents the results of the determination of VLHs in underwater vented and formation water discharges sampled from production platforms in the Gulf of Mexico.
@ 1981 American Chemical Society
Volume 15, Number 8, August 1981 917
Process Descriptions Hydrocarbon venting is a procedure in which waste gases associated with crude oil production are disposed of by flaring or underwater venting. This type of gas associated with produced crude oil (associated gas) is in contrast to natural gas which is solely produced (unassociated gas). In offshore areas underwater venting is the major means of disposing of waste gases, since it is safer and gases can be disposed of in larger amounts than by flaring. Associated waste gases contain appreciable amounts of C2-Clo aliphatic and aromatic condensates, unlike unassociated gas where only the C1-Cb gaseous aliphatic hydrocarbons are present. The composition of associated gas is related to the composition of the crude oil with which the gas is in equilibrium. Depending upon the operating efficiencies of the gadoil separators, various amocnts of condensates are removed. That gas which remains is considered waste gas. Formation water (or oil field brine) is water produced with oil and gas. On the average, 0.6 L of formation water is produced per liter of oil during the lifetime of the well (2). Dissolved and emulsified in formation waters are oil and gas which are partially recovered by processing with settling tanks and oil/water separators (density difference separation). A surfactant is often added to the water to break up the emulsion for better oil/water separation. The recovery of oil and gas from the water is not complete. Some hydrocarbons still remain in solution or are emulsified in the water. The types of hydrocarbons in the water depend upon the chemical (inorganic) properties of the water, the type of crude oil or gas produced, and the efficiency of the oil/water separation equipment. Unlike vented waste gases (hydrocarbon venting), the range of possible hydrocarbon compound types in formation water includes all those which are in the crude oil produced (gaseous hydrocarbons, VLHs, and >C14 hydrocarbons). This is because the soluble hydrocarbons in solution are accompanied by relatively insoluble hydrocarbons in emulsion.
ether) adsorbent, Tenax-GC. The collected components were desorbed from the Tenax-GC by heating (250 "C) and trapped on a liquid-nitrogen-cooled precolumn. With the use of a 6port valve, the trapped components on the precolumn were then "injected" onto a gas-chromatographic column by replacement of the coolant with 150 "C mineral oil for component separation and quantification. The dynamic stripping phase of the analysis was conducted twice on each sample to ensure complete stripping of the organic components from the water. The chromatographic column used was a 3.2 mm X 4.6 m copper tube packed with 10%SP-2100 on 80/lOO Supelcoport. The column was temperature programmed at 0 "C for 2 min, 0-180 "C at 4 "C/min, and 180 "C for 16 min. The length of time of the programming permitted elution of n -pentadecane. A Hewlett-Packard 5700A gas chromatograph with a flame ionization detector (FID) was modified to accomodate the precolumn and desorbance system. Peak areas from the chromatograms were measured with a 3933A Hewlett-Packard integrator. FID response factors (10) were incorporated in the calculations of the hydrocarbon and other organic compound concentrations. The analysis of the vented gas samples for VLHs did not need the stripping and desorbance apparatus. A 25-mL gas sample was injected directly onto the liquid-nitrogen-cooled precolumn. Component separation and quantification of the gas sample followed the procedure and conditions discussed previously. The volatile organic components were identified on a Hewlett-Packard 5982A dodecapole mass spectrometer interfaced to a 5710A gas chromatograph with a single stage glass jet separator and supported by a 5933A Data System. Details of the GC/MS analysis conditions are given in ref 9. The gaseous hydrocarbons (CI-C,) in the gas samples were determined by Bernard ( 1 1 ) . Gas samples were injected directly onto a 3-m, 1.5-mm i.d. Porapak Q gas chromatographic column thermostated at 60 "C. Results
Sampling and Analytical Procedures Hydrocarbon vented and formation water samples were taken from two different producing platforms in the Gulf of Mexico: the underwater vented samples from the TexacoEugene Island 338A platform (28" 12.3' N, 91" 41.2' W) in December 1977, and the formation water samples from the Shell-Buccaneer 296B platform (28" 45.0' N, 94" 44.0' W) in June 1978. The underwater vent samples were collected from a surface plume, located -100 m from Texaco's platform in 70 m of water. The diameter of the plume at the surface was 5 m. With a small rubber boat the plume was sampled for both water and gas. Surface water samples were taken with 2-L glass bottles, filled at arms length into the plume over the bow of the boat. Sodium azide (2-3 g) was added to the samples to inhibit biodegradation of the hydrocarbons. Surface gas samples were collected with 0.5-L widemouthed glass jars inverted under the plume surface to trap the rising bubbles. Both sample containers were opened and closed below the plume sea surface. The formation water sample was taken aboard the Shell platform at the disposal discharge pipe. The water sample had passed through the oil/water separators and was ready for discharge into marine waters. Two-liter glass bottles with sodium azide were used as sample containers. The method used to determine the VLHs in the hydrocarbon vented water and formation water samples is discussed in ref 8 and 9. The procedure involved dynamic headspace stripping of volatile organics from the water sample, and collection of organic components onto a solid poly(pheny1 918
Environmental Science & Technology
A chromatogram of the VLH fraction of a vented surface water sample is shown in Figure 1,with component identifications and quantities given in Table I. The total amount of VLH in the water sample taken a t the sea surface was 16.3 yg/L. Two-thirds of the VLHs were alkanes, mostly normal alkanes. Only 9.4% of the VLHs were aromatics with very small amounts of C3 benzenes. Benzene, toluene, and the xylenes were in concentrations ranging from 400 to 700 ng/L. Also given in Table I are the amounts of gaseous hydrocarbons and VLHs in the vented surface gas sample. The surface gas sample is in units of ymol of gas/L of gas and in percent of total hydrocarbons. Ca. 75% of the gas sample was hydrocarbons; the rest was unknown nonhydrocarbon gases (no FID response). Only 0.54% of the total hydrocarbons were VLHs. If the methylpentanes were included, -1.0% of the total hydrocarbons would be VLHs. Close to none of the VLHs were aromatic hydrocarbons. Almost all of the VLHs were alkanes (86%);n-hexane alone was over 50% of the alkanes. A chromatogram of the VLH fraction of a formation water sample is presented in Figure 2. Component identifications and quantities are given in Table 11. Some of the components in Figure 2 (peak numbers 14,15,21,and 33) were only partially resolvable. The concentrations of these components were estimated by integration with the Hewlett-Packard integrator. Over 20.0 mg/L of total VLHs was measured in the formation water. The possible hydrocarbons not identified would be at most a total of 1.0 mg/L. Ca. 80% of the VLHs were aromatic hydrocarbons: toluene concentration, -7.5 mg/L;
I
4
PLATFORM VENT Surf SCALE
3 3 0 n g / s q Cm Toluene-2 4 sq cm
Figure 1. Chromatogram of underwater vent plume-surface water sample. Peak number identifications are given in Table I.
Table 1. Concentrations of Gaseous Hydrocarbons and Volatile Liquid Hydrocarbons in Surface Water and Gas Samples from an Underwater Vent Plume a peak no.
compd
methane ethane propane isobutane n-butane isopentane 1 2 3 4
n-pentane 2-methylpentane 3-methylpentane n-hexane 5 methylcyclopentane 6 benzene 7 cyclohexane 8 2,3-dimethylpentane or 2-methylhexane 9 3-methylhexane 10 1,3-dimethyIcyclopentane 11 n-heptane 12 methylcyclohexane 13 2,2-dimethylhexane or 1,2,4-trimethyIcyclopentane 14 C3-cyclopentane 15 1,2,3-trimethyIcyclopentane 16 toluene
water sample, ng/L
concn gas sample, pmol/L of gas
b 26700 (80.0%) b 2600 (7.7%) b 2000 (5.9%) 560 (1.7%) b b b b b b 7520 1180 430 470 760 730 b 1330 1280 220
740 (2.2%) 270 (0.81%) 260 (0.78%) 80 (0.23%) 33 (0.10%) 80 5
0 1 18 14 5 24 4 3
40 40 680
concn peak no.
water sample, ng/L
compd
gas sample, pmollL of gas
17 2.3-dimethvlhexane or
190
6
18 2,4-dimethylhexane or 3-methylheptane
b
b
250
5
4-methy iheptane
19 1,(2 or 3 or 4)dimethylcyclohexane 20 1-methyl-3-ethylcyclopentane 21 n-octane 22 ethylcyclohexane 23 Ca-cyclohexane 24 ethylbenzene 25 m- and pxylenes
50 350
180 90 70 270
26 2-methyloctane or dimethylheptane 27 3-methyloctane
20
1
28 o-xylene 29 n-nonane
60 50
0 1
30 1,(2 or 3),(3 or 4)trimethylbenzene 31 n-decane n-undecane total VLH
30
total VLH aromatics total VLH cycloalkanes total VLH alkanes % VLH aromatics
20 16270 1530 3760 10980 9.4
tr t r c (0.54% VLH)d 180 1 28 151 0.5
a VLH component identifications were confirmed by mass-spectrometric analysis. Peak numbers correspond to those shown in Figure 1. Not quantitatively determined, tr = 0.1-0.4 pmol/L of gas. Percent of hydrocarbon gas which is VLH.
benzene, -1.2 m g b ; and xylenes, -3.6 m g b . A great diversity of Cs and C4 benzenes was evident in the sample; concentrations ranged from 100 to 400 pg/L. Ketones were also determined in the samples, and their amounts estimated. Methyl ethyl ketone was considered the most abundant, ca. 1500 PdL. Discussion Underwater Hydrocarbon Vent. In the hydrocarbon vented samples, hydrocarbons greater than n-decane were not
detected. The VLH concentration was over 16 pg/L in the vented water sample and almost 180 pmol/L in the gas sample. Ca. 30 VLHs were identified. In the gas samples -99% of all of the hydrocarbons were the Cl-Cb gaseous hydrocarbons. This is similar to natural gas concentrations. The average composition of natural gas from Louisiana shelf production is 92.5% methane, 4.7% ethane, 1.3% propane, 0.8% butane, and 0.6% pentane and heavier hydrocarbons. Pentane and VLHs in the vented gas sample were a little more concentrated at 1.65% (VLH = 0.54%).Vented hydrocarbon concentrations at the sea surface are expected to be variable from platform Volume 15, Number 8, August 1981 919
: 5 6 8 9
2
L
10
13
17
1
19 20 22
FORMATION WATER SCALE 22 ysqcm> Peah 130 2 4 SQ Cm
45
,
I
1
I
“-ALKANE CARBON NUMBERS
Flgure 2. Chromatogram of formation water sample. Peak number identifications are given in Table 11,
Table II. Concentratlons of Volatile Liquid Hydrocarbons in Formation Water Sample a peak no.
1 2 3 4
compd
2-methylpentane methyl ethyl ketone n-hexane methylcyclopentane
5
benzene
6 7 8
cyclohexane 2,2-dimethylpentane; 2,2,34rimethylbutane methyl propyl ketone
9
diethyl ketone
10 11 12
n-heptane methylcyclohexane
13 14
3-methylheptane; 2,5-dimethylhexane methyl isobutyl ketone toluene 2,2,34rimethylpentane
15 16
1,3-dimethyIcyclohexane 1-methyl-(1 or 3)-ethylcyclopentane
17
n-octane ethylcyclohexane
18 19 20 21 22
ethylbenzene m and p-xylenes 2,6-dimethylheptane; 2-methyloctane o-xylene
23 24 25 26 27 28 29 30
n-nonane cumene (isopropylbenzene) n-propylcyclohexane n-propylbenzene m- and p-ethyltoluene 1,(2 or 3),(3 or 4)-trimethylbenzene o-ethyltoluene 142 or 3),(3 or 4)-trimethylbenzene
concn, P9/L
1520 70 50 1150 100 50 570b 300 400 210 130 1906 7460 170 120 50 620 230 850 2060 150 1510 520 140 230 150 380 310 250 410
peak
compd
no.
concn, W L
31 32
n-decane 142 or 3),(4 or 5)-trimethylbenzene
410 380
33 34
m, p-, or o-cresol 1,2-diethylbenzene
35 36 37
3- or 4-ethyl-o-xylene sec-butylbenzene m, p-, or o-cymene (methylisopropylbenzene) m, p , or o-cymene; ethylxylene
50 140 100
38 39 40 41
160 90 50
m, p, or o-cymene; ethylxylene n-undecane 2-ethyl-pxylene; 3- or 4-ethyl-o-xylene alkylcyclohexane 2-ethyl-p-xylene; 3- or 4-ethyl o-xylene naphthalene
80 310 130 70 80 170
45 46 47
n-dodecane unknown
140
48 49 50 51
branched alkane 1- or 2-methylnaphthalene n-tridecane unknown
52 53
1,1,(4 or 6),(6 or 7)-tetramethyllindane unknown
42 43 44
unknown
54 branched alkane n-tetradecane 55 56 diethyl phthalate total VLH (identified components) total VLH aromatics total VLH cycloalkanes total VLH alkanes YO VLH aromatics
20 20 110 10 10 50
20300 16070 1060 3170 79.2
Component identifications were confirmed by mass-spectrometric analysis. Peak numbers correspond to those shown in Figure 2. No stripping efficiencies or adsorbent recovery analyses were conducted on the ketone and cresol compounds. Ketone and cresol concentrations are based on n-alkane standards with appropriate FID response factors of 0.7.
920
Environmental Science & Technology
to platform dependent upon the water depths of the venting discharge pipes and the compositions of the different waste gases. In the VLH fraction, the n-alkanes composed 57%of all of the VLHs in the water sample and 86% in the gas sample. Ca. 33% of the VLHs in the water sample were branched alkanes and cycloalkanes compared to 14% in the gas sample. Aromatic VLHs were almost completely void in the gas sample, while in the water sample aromatic VLHs were -10% of the total. From comparison of the gas and water samples of the vented samples, aromatic VLHs seem to partition readily into the aqueous phase as vented gas travels up the water column from the underwater discharge pipe to the sea surface. In this case, the partitioning of aromatic VLHs is almost complete by the time the gas reaches the surface. Consideration should be given to the fact that under nonequilibrium conditions (as in this discharge situation) aromatic VLHs have a higher rate of solution than the corresponding aliphatic or alicyclic VLHs. For a particular class of hydrocarbons, the rate of solution increases with a decrease in carbon number (7). Aromatic VLHs from surrounding waters, entrained into the ascending vented plume, are not believed to be major contributors to these vented water samples. Concentrations in Louisiana shelf waters range from 10 to 180 ng/L for benzene, from 10 to 70 ng/L for toluene, and from 15 to 100 ng/L for xylenes (9). From Table I, aromatic concentrations of the vented water samples were considerably higher than shelf water concentrations. The 9.4% aromatic VLHs in the vented water sample were very much smaller than the percent aromatic VLHs found in coastal water of 80%. An estimation of the amount of gaseous hydrocarbons and VLHs vented into the water column and atmosphere of the outer continental shelf of Louisiana and upper Texas was determined with the data from the Texaco vent samples and government available discharge rates. The total mount of vented or flared hydrocarbons in the OCS of the Gulf of Mexico during 1973 was reported to be 1.7 X 109 m3 (gas) by Sea Technology (12). More recent data of monthly discharge rates of oil-well gas vented or flared (vented gas-well gas is -5% of vented oil-well gas) are given (13):September 1974, 1.7 X lo8 m3; April 1976,3.7 X lo7 m3; March 1977,4.0 X lo7 m3; October 1977,5.9 X lo7 m3; May 1978,4.0 X lo7 m3; December 1979,3.1 X lo7m3. The 1979 discharge represents 3.5% of the total oil-well gas produced. From Brooks et al. ( 4 ) ,the
U S . Geological Survey estimated that 70% of gas flared and vented was vented underwater. The amount of gas vented underwater does not represent the amount which dissolves in the water column. When a model which describes the rate of methane bubble dissolution while rising in the water column (14) was used, the amount of vented gas dissolved in the water column before reaching the surface was conservatively estimated to be 5-15% of the gas vented. (For a radius of 0.5 cm and an average water depth of 30 m, -15% of a rising gas bubble will dissolve in the water column.) With the approximate range for dissolution of 5-15% and assuming 70% of the estimated total discharge, 4.2 X los m3/yr (4.2 X loll L of gas/yr), is vented underwater, then ca. 0.4 X 109-1.2 X IO9 g of VLHs/yr is dissolved in continentalshelf surface waters of the Gulf of Mexico, almost entirely on the Louisiana shelf. Ca. 6.0 X 109-6.8 X lo9 g of VLHs/yr is estimated to be vented directly into the atmosphere. Table I11 shows the estimated inputs of all of the vented gaseous hydrocarbon components and the VLH fraction discharged into the water column and the atmosphere. The volume mole percents of hydrocarbons are taken from Table I. The estimated amounts of methane and c2-c4 hydrocarbons dissolved in the water column of the Gulf range from 8 X lo9 to 26 X lo9 g/yr and from 5 X lo9 to 14 X lo9g/yr, respectively. These compare well with the estimate made by Brook et al. ( 4 ) of 25 X lo9 g/yr (25 000 metric tons) for methane and 11 X lo9 g/yr for CpC4 hydrocarbons. Ca. 2.5% by weight of the total hydrocarbons discharged by venting is VLHs with a t most 10%of that being aromatic. The observed higher dissolution rates of the VLH aromatic components compared to other gaseous hydrocarbons and VLH during ascent of vented gas through the water column are not included in the estimation. Formation Water. In contrast to underwater vented gases which contained only hydrocarbons from methane to n-decane, discharged formation waters possessed a greater and more complex variety of hydrocarbons: gaseous hydrocarbons, VLHs, and greater than n-Cl4 (solvent-extractable) hydrocarbons. The number of VLH components in the formation water sample (Table 11) were considerably more extensive than those in the vented samples (Table I). Ca. 45 VLHs were identified in the formation water with a total concentration of -20 mg/L. Benzene, toluene, and the xylenes made up -12 mg/L in the sample. Many C3- and C4-alkyl aromatic hydrocarbons (-15 compounds) were evi-
Table 111. Estimated Inputs of Vented and Formation Water Gaseous Hydrocarbons and Volatile Liquid Hydrocarbons into OCS Marine Waters of the Gulf of Mexico (Louisiana-Upper Texas) i o 4 (total hydrocarbons vented), glyr
methane ethane propane butanes pentanes methylpentane
170.0 31.0 35.0 30.0 15.0 3.8 7.2
VLH >C14 hydrocarbons
lo-'
(amount released to atmosphere from ventlng), g/yr
145.0-162.0 26.0-29.0 29.0-33.0 25.0-28.0 13.0-14.0 3.2-3.5 6.0-6.8
(solvent-extractable)
io-'
(amount dissolved In water column from ventlng), glyr
8.0-25.0 2.0-5.0 2.0-6.0 2.0-5.0 1.0-2.0 0.3-0.6 0.4-1.2a
lo-'
(dlscharged formatlon water hydrocarbons) b , glyr
64.0-30O.Oc 8.4-42.0' 0.8-18.0' 0.2-13.0' 0.2-4.9' 750 1740e
'Calculation of VLH dissolved in water column from venting: 4.2X 10l1 L of gas discharged by venting or flaring (average of rates given in text since April 1976-assumed all gas is hydrocarbons) X 0.7 (fraction vented in water column) + 22.4 (Liter of gas/mol STP) X 0.0054 (fraction of gas which is VLH) X 0.05-0.15 (fraction of gas dissolved in water column) X 100 (approximate molecular weight of VLH). Discharge rate = 3.47X 1 O 1 O L of formation water/yr. Gaseous concentration ranges were calculated from formation waters given by McAuliffe (3)and Brook et al. (4). VLH aromatic, alicyclic, and aliphatic discharged amounts were calculated to be 560 X IO', 40 X IO6, and 110 X lo6 g/yr, respectively. Unidentified VLH (1 mg/L) amounts were 40 X IO6 g/yr. a The solvent-extractable value is based on a 50 mg/L concentration; 72 mg/L was proposed EPA discharge upper limit (FederalRegister, April 13,1979).'See text for calculations.
*
Volume 15,Number 8, August 1981 921
dent in the formation water sample; concentrations ranged from 100 to 400 pg/L per component. Total aromatic VLHs made up 80%of the VLHs in formation water as compared to 10%for the vented gas (in water sample). This 80%aromatic value in the VLH fraction of the formation water is close to the observed percentage in Gulf of Mexico surface waters (9). However, most of the C3- and C4-alkyl aromatic hydrocarbons in the formation water were not evident within detection limits (
