United States Environmental Protection Agency Municipal Environmental Researc Laboratory Cincinnati OH 45268 Research and Development EPA-600/S2-81-209 Oct. 1981 Project Summary Oil Content in Produced Brine on Ten Louisiana Production Platforms George F. Jackson, Eugene Humes, Michael J. Wade, and Milton Kirsch A survey of the oil content of brine effluents from offshore crude oil production platforms was conducted to determine (1) the amount of oil in the brine, (2) the factors affecting the oil content of the brine, and (3) approaches for reducing the oil content of brine. Ten-day surveys were conducted on 10 platforms representing a wide range of characteristics with respect to produced fluids, processing sys- tems, and water treatment systems. Each platform had a flotation unit for final oil separation before discharge. At least 40 gravimetric and 20 infrared tests for oil were run on brine effluents from each platform. Tests for oil were also run at upstream points in the systems. Other brine tests were run for correlation with effluent oil content, including soluble oil, oil drop-size distribution, sus- pended solids, surface tension, ionic analysis, pH, specific gravity, and temperature. Crude oil tests included specific gravity, surface tension, boiling point distribution, and temper- ature. Records were kept of operational factors, including water cuts, lift methods, pressures, chemical addi- tion programs, and hydraulic loading of water-treating units. Test and operational data were analyzed for correlation with effluent oil content. This Project Summary was developed by EPA's Municipal Environmental Research Laboratory, Cincinnati, OH. to announce key findings of the research project that is fully docu- mented in a separate report of the same title (see Project Report ordering information at back). Introduction This study was conducted to develop information on the oil content of brine discharges from offshore oil platforms. The specific objectives were: 1. To characterize the brines dis- charged from offshore platforms with respect to oil content, 2. To identify the factors contributing to the oil content of the brine, and 3. To consider approaches to reduce brine effluent oil content. The program was conducted in two phases so that Phase I experience could be used to revise the Phase II plan. The approach to meeting the program objectives was to conduct 10-day field surveys on 10 platformsthree during Phase I and seven during Phase II. A major part of the testing was directed to defining the variability of brine effluent oil content. Special tests were run to determine whether the oil in the brine was soluble, dispersed in fine droplets, or associated with suspended solids. Information on the design and operation of the water treatment systems were also recorded for correlation with brine oil test data. Methods and Materials Platform Selection The objective in platform selection was to pick platforms representing a ------- wide spectrum of factors having the most influence on effluent oil content. The following technical criteria were used for platform selection: Treatability Lift method Water cut Process complexity Chemical addition Gravity separator type Flotation unit type Flotation unit hydraulic loading All platforms selected were producing oil, gas, and water. The number of wells producing oil per platform varied from 1 to 30 at the time of the survey. Three types of gravity separator and flotation units with five different design variations were included in the survey. The range of hydraulic loading of flotation units selected was 9% to 84% of design rating. The percent of production gas lifted ranged from 0% to 99.8%. No two chemical addition programs were the same. A generalized schematic of an offshore production system is shown in Figure 1. All of the platforms considered for the survey were in the Louisiana Gulf Coast area from Lafayette (South Marsh Island) to east of the Mississippi delta, and from the marsh out to 140 km offshore. The platforms studied were located where the large hydrocarbon accumulations were mostly associated with salt domes or anticlines overlying various salt masses. The characteristics of produced fluids from other locations and other forma- tions may be different from those included in this survey. Little information is generally available on the amounts of soluble oil and surface active compounds present in the brine from various locations and formations. But differences are known to exist that could have a significant effect on oil/water separa- tion. Data Collection Analytical Test Methods Standard analytical test methods were used for most of the testing program. Procedures published by the U.S. Environmental Protection Agency (EPA), American Society for Testing and Materials, American Public Health Association, American Petroleum Insti- tute, and special procedures adapted for this program were used. Table 1 lists parameters measured and methods used. Each method is summarized in the following paragraphs. Table 1. Analytical Test Methods Parameters Method Oil and Grease Temperature pH Boiling range distribution Specific gravity Water cut Suspended solids Surface tension Viscosity Crude oil solubility Susceptibility to separation Ionic analyses of sodium, potassium Iron, calcium, magnesium, barium Chloride, sulfate Total dissolved solids Sulfide Alkalinity Bacterial culture Particle size distribution Infrared (EPA' Storet 00560) Gravimetric (EPA') Thermometer fASTM2) Combination electrode fASTM3 Method B) Gas chromatography (ASTM2 022887-73) Hydrometer (ASTM2 D1298-67) Volumetric (ASTM2 DJ 796-68) Gravimetric (EPA' Storet No. 00530 ASTM3 D1888-67) Surface tensiometer (ASTM3 D 1590-60) Viscometer (ASTM2 D 445-74) Silica gel adsorption (APHA4 502E) Equilibration (Shell Oil Company)6 Filtered brine (Mobil Oil Corp.)1 IR scan (EPA') Infrared (Conoco, Inc.6 API5 734-53) Flame emission (API5) Atomic absorption (EPA1) (API5) Autoanalyzer (APHA4) Gravimetric (EPA') lodometric titration (APHA4) Electrometric titration (API5) Sulfate reducing (API5 RP 38) Photomicrographic (Rockwell International8) ( 1. U.S. Environmental Protection Agency, 1979, "Methods for Chemical Analysis of Water and Wastes." 2. American Society for Testing and Materials, "1974 Annual Book of ASTM Standards, Part 23/24, Petroleum Products and Lubricants." 3. American Society for Testing and Materials, "1978 Annual Book of ASTM Standards, Part 31. Water." 4. American Public Health Association, "Standard Methods for the Examination of Water and Wastewater," 14th Edition. 1975. 5. American Petroleum Institute, 1968, "API Recommended Practice for Analysis of Oilfield Water." Nonstandard method. 6. Oil and Grease Determination Total recoverable oil and grease deter- minations by infrared (IR) analysis were made on board the platforms according to EPA procedures. Samples of brine were also extracted for analysis of total recoverable oil and grease by gravimetric techniques. IP-Oil w/Silica Gel Test- TheIR- oil w/silica gel test was used as an indicator of polar water-soluble-type compounds in the brine. Hydrocarbon oils in Freon have been shown to be adsorbed on silica gel only to a very limited extent, whereas naphthenic acids, vegetable oils, and other polar compounds with significant water solubility are adsorbed. To the extent that the IR-oil w/silica gel test is a true indicator of solubility, it is also an indicator of a lower level of treatability by physical processes. The IR-oil and corresponding IR-oil w/silica gel tests were run on the same Freon extracts. The term "soluble oil" is used in this report to indicate the material extracted by silica gel. The term "dispersed oil" is used for the unextracted material. Measurements to determine adsorb- able hydrocarbons were made according to APHA Standard Method 502E. IP-Oil Filtered Brine Test The IR-oil filtered brine test was also used as an indication of treatability. Brine ------- I Chemicals I [ i VI Subsurface 0/G W/S Gas Oil Water Separator Storage] Tank \ Oil to Pipeline O W IPrecipitator) (0/W Separator) (Skim Tank) W 0 Polishing Unit Flotation, Coalescer, etc. Water to Sea S Chemicals Arrows show direction of fluid flow. Letters alongside arrows indicate materials present in that stream. Letters are arranged in order of decreasing concentration of each componente.g., 0/G/W Code: OilGasWater. Figure 1. Generalized schematic of offshore production system. filtered and the IR-oil content of the filtrate was measured. Only soluble oil and very fine droplets (less than 8 micrometers) were expected to pass through the filter. Susceptibility-to-Separation Tests The purpose of the susceptibility-to- separation tests was to provide a quantitative measure of the rate of separation of oil from brine by gravity. The tests were run by a procedure supplied by Conoco, Inc.* Several samples were taken, each in a different separatory funnel. The brine oil content was then measured after various defined settling times. For Phase I testing, the settling times were 1, 5,15, 'Mention of trade names or commercial products does not constitute endorsement or recommenda- tion for use 30, 60, and 120 min. For Phase II testing, the settling times were 2, 5,15, 30, 60, and 120 min. Zero-settling-time control samples were taken immediately before and after the settling test samples were taken. Oil content was determined by the IR technique previ- ously described. Suspended Solids Tests Oil- coated solids are potential contributors to brine oil content. Suspended solids tests were run to check for correlation between brine suspended soilids and oil content. Suspended solids data were generated following the EPA Storet Method No. 00530. Samples were collected onboard the platforms using in-line filter holders to prevent oxidative production of suspended solids. Each filter was washed with deionized water, frozen, and sent to the onshore laboratory for analysis. Crude Oil Equilibration Equili- bration tests were run by a procedure supplied by Shell Oil Company. A layer of crude oil was placed on top of a layer of synthetic brine in a flask so that the two layers were not mixed. The flask was then held in an oven at 82°C for 14 days, and a sample of the brine was taken for an IR-oil content measurement. For Phase I tests, a synthetic brine equivalent to a concentration of 100,000 mg/l was used with an oil/water volume ratio of 4:1. For Phase II testing, the brine concentration was the same as that of the produced brine of the particular platform. In addition, one equilibration test was run with the same ------- oil/water ratio as the produced fluids, and a second test was run with the 4:1 oil/water ratio. Particle-Size Distribution Small oil drops are more difficult to separate from brine than large drops. The particle-size test provided a measure of the size distribution of oil drops (in the 2- to 120-micrometer range) in a given volume of brine. The drop size measure- ments were also used to calculate the concentration of dispersed oil. Particle-size distribution tests were run by a new nonstandard procedure developed by Rockwell International. Brine samples were taken from a flowing stream into a cell where the flow was stopped just long enough to take photomicrographs of the particles present. The procedure can distinguish between solids, oil droplets, and gas bubbles. Other Various other chemical and physical properties were measured on the brine to investigate possible correla- tions with oil content values. These properties included temperature, pH, alkalinity, specific gravity, surface tension, viscosity, sulfate-reducing bacteria counts, total dissolved solids, and chemical species such as iron, sodium, potassium, calcium, barium, chloride, and magnesium. Operational Characteristics In addition to analytical testing, the program plan included collection of available information on produced fluids and on the design and operation of production facilities to evaluate for correlation with brine oil content. The characteristics of produced fluids, chemical usage, design and operating conditions of the processing system, upsets, and intermittent operational procedures were of special interest. A list of the types of information recorded is as follows: Well Data Formation identification Total vertical depth Production rates Water cut Lift method Lift gas Shut in bottom hole pressure Flowing tubing pressure Choke size Gravity of oil Receiving vessel Chemical injection Processing Data Flow rate Temperature Pressure Vessel parameters Residence time Overflow rate Chemical addition Upsets Intermittent operational or maintenance procedures Unplanned events Information on the above factors was obtained by observations and measure- ments by the field survey team, from company records, and by verbal reports from operating personnel. Results Summary of Analytical Test Results A summary of the tests for brine effluent oil content for all 10 platforms is presented in Table 2. Means and standard deviations are listed for gravimetric oil (GR-oil), IR-oil, soluble oil, and dispersed oil. Performances of flotation units are compared in terms of dispersed oil in the effluent in Table 3. The table also lists influent oil content, hydraulic loading, chemical addition rate, and the flotation unit description for each platform. A comparison of the performance of gravity separators is presented in Table 4. The table also lists the type of separator, settling test results, the brine/oil specific gravity difference, and brine temperature. Drop size distribution tests are summarized in Tables 5, 6, and 7 for flotation unit influents and effluents. The tables include listings of median drop sizes, largest drop sizes, cumulative number distributions, cumulative con- centration distributions in percent, and cumulative concentration distributions in milligrams per liter. Produced fluid properties are described in Table 8. Discussion Effluent Oil Content Significant differences occurred in the flotation effluent mean IR-oil, GR- oil, dispersed oil, and soluble oil contents of the 10 platforms (see Table 2). Significant negative correlations exist between effluent IR-oil content and surface tension sample-to-sample for each platform. A summary listing of mean surface tension and linear regres- sion slope and correlation coefficient is presented in Table 9 for all platforms. Flotation Unit Performance Significant differences exist in the amount of dispersed oil remaining in the 10 flotation effluents (see Table 2). Four factors of potential significance to flotation unit performance are influent oil concentration, hydraulic loading, flotation chemical addition rate, and the type of flotation unit. Significant design and operational differences exist for all platforms. A single predominant factor that determines flotation effectiveness in removing dispersed oil has not been identified by simple bivariate data analysis, and it is therefore not possible to make quantitative conclusions about the factors most important to flotation unit performance. General conclusions are presented concerning flotation unit performance, however. High influent oil content excursions over 500 mg/l usually had a marked effect on effluent oil content. An influent oil content below 300 mg/l appears desirable. Some lightly loaded units may handle more than this. Hydraulic loading was not evaluated comprehensively during the study because most units operated at relatively low and uniform loadings, and problems were experienced in flow monitoring. Oil content usually increased when chemical feed was interrupted. Gravity Separator Performance The principal purposes of the gravity separators in the water-handling systems are (1) to remove a large percentage of the oil from the water upstream of the flotation units, and (2) to protect the flotation units from the effects of slugs of oil that might enter the water handling systems as a result of upsets in the production-processing systems. This survey has demonstrated that the gravity separators do adequately per- form their primary functions; the superiority of one type over the others was not demonstrated, however. A general relationship exists between the oil content of gravity separator effluent and the rate of oil separation as indicated by settling tests (Table 10). Brine Soluble Oil Four tests were used as indicators or measurements of soluble oil: the IR-oil w/silica gel test, the equilibration test, the filtered brine test, and the IR-scan ------- Table 2. Comparison of Oil Contents of Platform Flotation Effluents GR-OH. mg/l IR-Oil, mg/l "Dispersed" oil, mg/l "Soluble" oil, mg/l "Soluble" oil. Fraction of IR-Oil Platform SS107 SS198G BDCCF5 ST131 BM2C SMI SOB EI18CF WD45C ST177 SP65B Z 7.6 18 26 12 22 48 52 63 64 77 (s) (5.2) (9.2) (6.9) (13) (6.7) (16) (24) (95) (74) (73) X 15 36 36 37 39 48 76 81 95 106 (s) (3.7) (7.8) (8.3) (19) (4.2) (16) (38) (109) (103) (99) X 1.6 5.7 26 5.9 4.9 23 63 66 92 38 (s) (1.5) (7.7) (8.6) (13) (5.1) (13) (30) (106) (126) (80) X 13 31 10 28 36 25 13 30 21 61 (s) (2.7) (2.7) (2.3) (3.1) (4.1) (4.7) (13) (32) (13) (15) % 87 86 28 76 92 52 17 37 22 58 Note: Some numbers do not check because of rounding. Two significant figures have been retained in all numbers below 100. x = Mean (s} - Standard deviation Table 3. Performance Comparisons for Platform Flotation Units Flotation effluent Flotation influent Platform SS107 BM2C SS198G ST131 SM130B BDCCF5 SP65B EI18CF WD45C ST177 uispcr X mg/l 1.6 4.9 5.7 5.9 23 26 38 63 66 92 SttU Oil (s) mg/l (1.5) (5.1) (7.7) (13) (13) (8.6) (80) (30) (106) (126) toiai X mg/l 215 158 130 386 156 113 170 222 1169 432 r in -on (s) mg/l (49) (65) (39) (199) (105) (15) (147) (210) (3409) (394) Hydraulic loading % of design 24-31 18-39 <1-2.5 3-12 1-20 53"' II"1 24-30 68-75 26-47 Flotation chemicai addition rate ppmv 14 17 255 126 0 5 17 0 7 26 1 Flotation unit description 4 4 3 4 4 1 4 1 1 4 - cell (M) - cell (M) - cell (H) - cell (M) - cell (M) - cell (H) - cell (M) - cell (D) - cell (H) - cell (H) Note: (M) = Mechanical gas dispersion (H) - Hydraulic gas dispersion (D) = Dissolved gas (1) Estimated mean. test (which was only performed during Phase I). The API gravity, brine total dissolved solids, and pH were also examined for correlation with soluble oil. These parameters did not show a significant relationship to soluble oil by simple bivariate analysis. The filtered brine test requires additional development to establish it as a reliable indicator of soluble materials or treatability. The equilibration test provides an indication of soluble components in brine of the same order of magnitude as the IR-oil w/silica gel test. The number of tests is too limited, however, for definitive conclusions. When the program plan was devel- oped, water cut was proposed as a parameter to examine for correlation with soluble oil, the theory being that brine from new wells with a low water/oil ratio would be high in soluble oil components. The data indicate that a significant correlation does exist. Linear regression analysis yields: Soluble oil, rng/l = 40 - 0.29 (water cut, %) r = -0.67 Significant correlations between suspended solids and brine oil content were not identified, possibly because of precision and accuracy problems with the suspended solids analysis. The sulfate-reducing bacteria counts in brine effluents were 100/ml or less for all platforms except ST131. For this particular survey, sulfate-reducing bacteria did not appear to relate to effluent oil content. Conclusions 1. The program was successful in developing an internally consistent data base of oil content and related properties for effluent and influent samples taken on a regular sched- ule from 10 separate offshore platforms for 10 consecutive days. 2. The second objective, to deter- mine the factors affecting the variability of brine oil content, was partly satisfied. Simple statistical analysis identified soluble oil as a significant variable from platform to platform, and brine surface tension as a significant variable on any platform. Variations in oper- ating conditions (such as influent oil content, excursions in influent oil content, interruption of flotation ------- Table 4. Performance Comparisons for Platform Gravity Separators Settling tests Rl Water Effluent Settling time Sample"' Hydraulic loading A rine/oil specific treatment IH-OII. mg/l K min 17nmin point Tank rpl gravtty separator Platform type x (s) mg/l mg/l - (m3/d)/ (m3/d)/ m2 plate pack BDCCF5 Skim Tank 113 (15) 103 53 9-i 27 SS198G CPI 130 (39) 209 117 8-i - 10 SM130B CPI 156 (105) 169 107 8K-i - 242 BM2C CPI 158 (65) 219 128 8-i - 580 SP65B Skim Tank 170 (147) 311 128 5A30 21 SS107 None 215 (49) 119 86 9-i 120 EI18CF Skim Tank 222 (210) 151 39 8-i 84 ST131 Gun Barrel 386 (199) 851 239 8-i 8.2 ST177 Gun Barrel 432 (394) 210 100 9-i 31 WD45C None'3' 1169 (3409) 59 54 9-i 38 (1) Separator influents were sampled if a sample tap was available. Other points and effluents were samples could not be taken. (2) Gravity separation was in an oil tr eater with the primary function of separating water from oil. (3) Gravity separation was in two gun barrels with the primary function of separating water from oil. - .232 .258 .268 .262 .221 .270 .330 .287 .309 .183 sampled Brine temperature °C 41.1 36.5 40.9 45.6 38.0 49.2 39.9 22.8 36.6 40.2 when influent Table 5. Cumulative Percent-by-Number Drop Size Distribution for Composites of Test Runs Oil Percent-by-number of drops with diameter equal or less than Platform pies Large Largest Sam- Number Calculated11' Measured31 2 um 5pm JO /jm 20 um 30 um 40um 60 um 100 urn >100um drops drop pies''" of drops mg/l mg/l % % % % % % % % % >40 >60 u Flotation Influent WD45C ST177 BM2C ST131 BDCCF5 SS107 SSI98G EI18CF SM130B 399 340 410 359 410 378 365 574 1.715 2.557 32 1.537 29 1,109 492 1.231 53 277 9 293 11 108 284 685 42 204 99 51 189 88 44.5 130 0.01 3.8 0.01 3.8 63 6.2 942 855 325 41.0 32.8 540 45.0 64.0 99.6 98.0 89.0 92.5 89.0 97.0 85.6 93.8 9997 99.5 973 994 972 99.87 973 9865 100.OO 99.92 9997 100.00 99.0 100.OO 99.88 99.98 100.00 - 0 0 3 0 0 0 1 0 25 55 35 49 99.0 100 OO 0 0 35 700.00 0 0 28 990 9955 99.95 100.00 11 2 97 9905 995 99.77 99.94 100.00 41 26 120 Flotation effluent WD45C ST177 BM2C ST131 BDCCF5 SS107 SS198G EI18CF SM130B 254 512 410 157 368 410 115 355 293 1.637 1,586 26 14 565 26 48 629 372 407"> 35 4 7 57 4 26 161 50 9 5 28 1 3 78 15 57 57 9 001 25.2 0.01 40 5.6 30.3 95.2 97.1 18 32.5 87.8 150 64.0 48.0 94.2 98.2 99.63 91 85.0 98.8 93.5 94.8 860 99.78 99.4 99.94 1OO.OO 100.00 9985 100.00 99.42 9845 99 78 99.8 9998 99.94 99.42 999 9978 99.95 99.98 99.98 700.00 1OO.OO 9978 9995 100 OO 99.98 700.00 700.00 - 700.00 8 1 O 0 1 0 0 0 3 1 0 0 0 1 0 0 0 0 64 41 17 16 81 14 35 32 59 '"Number of brine samples photographed for drop counts. I2'O// as calculated from drop counts '^Dispersed oil as measured by IR-Oil w/Silica Gel tests on the brine effluent from the particle-size test equipment when the particle-size-distnbution test was run. 141 Test run during upset conditions. chemical, and hydraulic loading) produced notable changes in effluent brine oil content; but no simple statistical correlations were developed. 3. A comparison of the oil content of the gravity separator effluent with the 5- to 120-min values of the susceptibility-to-separation test indicated that the equipment was generally operating near those values. A comparison of flotation influent and effluent oil showed that the flotation units reduced the oil content below the limit for gravity separators indicated by the susceptibility-to-separation test. Most flotation units were effective in removing dispersed oil, but their removal efficiencies differed. Special adaptations of six test methods contributed to the suc- cessful accomplishment of the project objectives. a. The infrared method for mea- suring oil concentrations in brine proved to be acceptable for onsite determinations. Al- though it gives different results from the gravimetric method, the two can be correlated on a platform-by-platform basis. ------- Table 6. Cumulative OH Content by Drop Size in Percent Oil Percent of oil in drops with diameters equal or less than ' Platform Sam- ples12' Number Calculated" Measured3' 2 um of drops mg/l mg/l % Sum % ^ 20 um 30 urn 40 um % 60 um 100 um % % Large >700 um drops % >40 >60 Largest drop u Flotation Influent WD45C ST177 BM2C ST131 BDCCF5 SS107 SS198G EI18CF SM130B 399 340 410 359 410 378 365 574 1.715 2,557 32 1,537 29 1,109 492 1,231 53 277 9 293 11 108 284 685 42 204 99 51 189 88 5 0.42 0.01 003 0.01 006 0.02 002 44.5 17.5 30 60 30 145 1 9 1 7 76 375 27.5 428 260 708 108 68 925 60 46.0 762 430 930 31 0 124 100 00 79 570 90.0 652 100.00 43.0 155 91 100.00 970 100.00 56.0 228 100.00 70000 79.5 700.00 37 0 65 5 0 3 0 1 0 0 77 70000 47 0 0 0 0 0 0 2 26 25 55 35 49 35 28 97 120 Flotation Effluent WD45C ST177 BM2C ST131 BDCCF5 SS107 SS198G EI18CF SM130B 254 512 410 157 368 410 115 355 293 1,637 1.586 26 14 565 26 48 629 372 407"" 35 4 7 57 4 26 161 50 9 5 28 1 3 78 15 1.3 73 012 001 0.85 0.01 0.07 0.04 1 1 66 37 20 30 17.4 2.8 11 4 42 17.5 115 55 670 48.5 375 800 31 0 275 24.8 27.2 70 100.00 100.00 463 10000 47.0 71 0 260 488 80 51 5 470 978 26.0 740 87 580 1OOOO 1OOOO 26.0 943 70000 70000 580 70000 70000 S 7 0 0 7 0 0 - 0 3 7 0 0 0 7 0 0 0 0 64 41 17 16 81 14 35 32 59 '"Oil as calculated from drop counts in milligrams per liter "'Number of brine samples photographed for drop counts. ^'Dispersed oil as measured by IFI-Oil w/Si/ica Gel tests on the brine effluent from the particle-size test equipment when the particle-size-d/stribution test was run. "'Test run during upset conditions Table 7. Cumulative Assigned Oil Content Distribution by Drop Size Groups in Composites of Test Runsn} Oil Assigned concentration of oil in drops w/dia equal or less than '" Sam- P/atform pies Flotation Influent WD45C 399 ST177 340 BM2C 410 ST131 359 BDCCF5 - SS107 410 SS198G 378 EI18CF 365 SM130B 574 Flotation Effluent WD45C 254 ST177 512 BM2C 410 ST131 157 BDCCF5 368 SS707 470 S5798G 775 EI18CF 355 SM130B 293 Number Calculated'3' of drops mg/l 1,715 2,557 32 1,537 29 7.709 492 7,237 7,637 7,586 26 74 565 26 48 629 372 53 277 9 293 77 708 284 685 40715' 35 4 7 57 4 26 767 50 Measured"' 2 um mg/l mg/l 42 204 99 57 789 88 9 5 28 7 3 78 75 00 0 7 0.0 0.0 00 00 00 0.0 0.2 0.0 0.0 0.0 0.2 5 um mg/l 73 722 30 7.4 36 7.5 0.2 0.2 4.9 0.0 03 33 2.6 70 um mg/l 77 6 873 257 36.7 20.4 6.0 6.0 2.4 70.5 0.8 0.9 27.5 3.7 20 um mg/l 793 755.4 426 47.4 586 70.9 9.0 5.0 730 7 0 7 4 554 39 30 um mg/l 239 783.6 645 57.0 87 3 73.6 74.4 7.4 76.3 3.9 40 um mg/l 420 797.9 99.0 705.8 20.7 76.2 30 78.0 3.9 60 um 100 um mg/l mg/l 2040 750.3 7890 32.6 57.6 76.2 28 0 75.0 Large >100um drops mg/l >40 0 3 0 1 0 0 77 88.0 47 - 8 7 0 0 7 0 0 0 3 >60 0 0 0 0 0 0 2 26 7 0 0 0 7 0 0 0 0 Largest drop f 25 55 35 49 35 29 97 720 64 47 77 76 87 74 35 32 59 "'The cumulative oil concentration data in this table were calculated by multiplying the total analytically determined dispersed oil concentration by the percentage concentration data reported in Table 200 in full report "'Number of brine samples photographed for drop counts. "'Oil as calculated from drop counts "'Dispersed oil as measured by IR-Oil w/S/lica Gel tests on the brine effluent from the particle-size test equipment when the particle-size-distnbution test was run Test run during upset condition b. The silica gel/IR method for oil and grease analysis provided a measure of the soluble oil content. The soluble oil content at the discharge conditions is a lower limit of treatability by gas flotation. c. The equilibration method mea- sured brine soluble components of the crude oils. Results using this method are of the same order of magnitude as those obtained by the silica gel/IR method. The susceptibility-to-separation test proved to be a useful semi- quantitative tool in estimating the ease and ultimate limit of gravity separation. The filtered brine method was intended to provide a measure ------- Table 8. Properties of Produced Fluids Platform Water Cut, Percent Brine Properties pH Total Dissolved So/ids, mg/l (Gravimetric) Temperature, °C Specific Gravity"' Surface Tension,"' dynes/ cm Crude Oil Properties API Gravity @ 156°C Temperature, °C Specific Gravity" ' Surface Tension,"' dynes/cm Viscosity @ 37.8°C, Cent/poise Boiling flange, °C Initial Boiling Point Final Boiling Point SP65B 35 69 105,000 386 1.086 67 29.5 36.0 0865 30 824 150 480 WD45C 64 70 80.500 397 1.073 60 258 36.9 0890 30 20.21 150 485 ST177 47 63 203,000 36.1 1 151 67 36.8 329 0842 30 347 150 480 BM2C 27 66 1 14,000 450 1 093 60 34.2 39.1 0831 25 3.41 150 410 ST131 32 63 138,000 22.6 1 129 61 367 200 0842 25 285 150 480 BDCCF5 91 67 108,000 409 1 095 61 31.4 31 8 0863 28 826 150 480 SSI 07 87 66 112.OOO 48.2 1.095 63 35.2 44 5 0825 26 3.71 150 500 SS198G 10 7 1 114,000 31 1 1.106 66 340 30.2 0.848 27 524 150 500 EI18CF 90 63 162.00O 382 1 140 57 41 9 35.1 0810 26 2.44 150 480 SM130E 19 62 163.000 40.1 1 133 68 29.2 350 0865 26 692 150 400 Percent recovered Below - 200 200 - 250 250 - 300 300 - 350 350 - 400 400 - 450 450 - 500 500 - 550 49 1 104 14.6 14.5 5 1 54 08 0.2 297 124 21.9 21 2 62 68 1 4 0.4 428 10.5 193 130 66 6.9 0.8 0.2 61 1 22.6 132 24 06 0 1 00 00 61 7 226 88 1 6 0.3 0 1 00 00 459 245 22.5 56 13 02 00 00 38.2 24.3 25.5 6.3 3.0 20 0 7 00 484 272 175 3.2 1 6 1 2 06 00 37.1 23.4 273 7.5 2.1 03 0.0 00 77.4 14.0 70 1.4 02 0.0 00 00 Note: Brine properties are based on tests on flotation unit effluents. Crude oil properties are based on tests on crude oil samples taken after all treatment steps o the platform "'Specific gravity and surface tension test results are reported for approximately the listed temperature Table 9. Surface Tension Summary Platform SP65B WD45C ST177 BM2C ST131 BDCCF5 SSI 07 SS198G EI18CF SM130B Mean surface tension 67 60 67 60 61 61 63 66 57 68 Linear Slope -6.9 -17.8 -11.6 -0.4 -1.24 -2.94 -6.1 -4.5 -3.2 -3.0 regression Correlation coefficient -0.96 -0.87 -0.70 -0.5 -0.65 -0.73 -0.92 -0.68 -0.84 -0.32 of soluble oil plus finely dis- persed (less than 10 micro- meters) oil in the effluent. As such, this method could provide an alternative to the silica gel/IR method in establishing a lower limit of treatability for flotation processes. Differences in experimental procedure caused this method to be in- consistent with the IR method for determining oil and grease in some cases. f. Oil drop-size distributions were obtained with unique new 8 equipment from photomicro- graphs for both flotation unit influents and effluents. These measurements determined the size range of dispersed oil droplets removed by gas flota- tion. Dispersed oil concentra- tions calculated from these distributions compared poorly with measured IR oil concen- trations. The experience of this project indicates that the first four methods can be used to characterize produced brine. The filtered brine method, after suitable modification, appears promising. Th photomicrographic method isapplicabl to verifying mathematical models and i improving equipment design. Recommendations 1. A comprehensive analysis of th data base provided for this projec must be undertaken. Included shoul be a multivariant analysis of th treatment processes to identify th significant variables affecting th stabilization of oil in water an process unit performance. No othe field studies of treatment processe should be undertaken until this wor is complete and its recommendation are known. 2. Methods for characterizing oil ii water beyond simply measuring c its concentration should be investi gated. Some obvious candidates ar (1) boiling point distribution curve for gas/liquid chromatography (GLC (2) gas/liquidmass spectrometr (GLC/MS), and (3) infrared spectres copy. Those methods that provi useful could be employed in a stud of the characteristics of bulk oils am extracts from a range of wate discharge points. 3. Two methods subject to problem during the present study (filter ------- Table 10. Comparison of Settling Tests for Separator Effluent Platform BDCCF5 SS198G SM130B BM2C SP65B SS107 EI18CF ST131 ST177 WD45C Water treatment separator type Skim Tank CPI CPI CPI Skim Tank None Skim Tank Gun Barrel Gun Barrel None Mean mg/l 113 130 156 158 170 215 222 386 432 1.169 Proportion in settling"' Test range Percent 85 90 80 66 60 8 60 95 31 0 Settling test range"' IR-oil content 5 min mg/l 121 237 192 261 331 136 163 1,259 271 68 120 min mg/l 43 101 100 105 113 56 38 168 85 49 l"The settling test range is reported as the highest 5-minute settling test result and the lowest 120-minute test result. ^Gravity separation was in an oil treater with the primary function of separating water from oil. {3]Gravity separation was in two gun barrels with the primary funciton of separating water from oil. brine oil in water and flow rate) need more study. A search should be conducted for a reliable, portable, continuous flowrate meter. The full report was submitted in partial fulfillment of Contract No. 68- 03-2648 by Rockwell International under sponsorship of the U.S. Environ- mental Protection Agency. ------- George F. Jackson and Eugene Hume are with Crest Engineering, Inc.. Tulsa, OK 74101; Michael J. Wade is with Texas Instruments. Inc., Dallas. TX 75165; and Michael Kirsch is with Rockwell International Corporation. NewburyPark, CA 91320. John S. Farlow is the EPA Project Officer (see below). The complete report, entitled "Oil Content in Produced Brine on Ten Louisiana Production Platforms," (Order No. PB 82-1O8 408; Cost: $33.50. subject to change) will be available only from: National Technical Information Service 5285 Port Royal Road Springfield. VA 22161 Telephone: 703-487-4650 The EPA Project Officer can be contacted at: Oil and Hazardous Materials Spills Branch Municipal Environmental Research LaboratoryCincinnati U S. Environmental Protection Agency Edison. NJ 08837 10 . S. 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