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A Case Study in TAN Determination Devils Tower (GOM) Crude
A Case Study in TAN Determination
Devils Tower (GOM) Crude
History of Devils Tower TAN
Uses and Misuses of ASTM D664 TAN Test
Potential Errors in D664 TAN Measurements- Devils Tower Examples- Sampling, Preparation and Testing
Addressing Refinery Corrosion Problems
Enhancing Value of High TAN Crude Oils
History of Devils Tower TAN History of Devils Tower TAN
Uses and Misuses of ASTM D664 TAN TestUses and Misuses of ASTM D664 TAN Test
Potential Errors in D664 TAN MeasurementsPotential Errors in D664 TAN Measurements-- Devils Tower ExamplesDevils Tower Examples-- Sampling, Preparation and TestingSampling, Preparation and Testing
Addressing Refinery Corrosion ProblemsAddressing Refinery Corrosion Problems
Enhancing Value of High TAN Crude OilsEnhancing Value of High TAN Crude Oils
TopicsTopicsTopics
In June 2006, Williams Pipeline reported to Dominion that the Total Acid Number (TAN) of Devils Tower crude was 2.4 mg KOH/g. In July, a Gulf Coast refiner heard that it was 3.1.
Refiners purchasing South Louisiana Intermediate (SLI) began to do so at an increased discount to HLS. Some of the discount was associated with reduced gravity and increased sulfur content.
DEPI began a process to determine whether TAN readings were accurate and whether SLI crude was deserving of such a large discount.
Test results of combined crude and of individual wells at multiple labs created concerns about testing methodology due to repeatability and accuracy issues.
In June 2006, Williams Pipeline reported to Dominion that the In June 2006, Williams Pipeline reported to Dominion that the Total Acid Number (TAN) of Devils Tower crude was 2.4 mg Total Acid Number (TAN) of Devils Tower crude was 2.4 mg KOH/g. In July, a Gulf Coast refiner heard that it was 3.1. KOH/g. In July, a Gulf Coast refiner heard that it was 3.1.
Refiners purchasing South Louisiana Intermediate (SLI) Refiners purchasing South Louisiana Intermediate (SLI) began to do so at an increased discount to HLS. Some of the began to do so at an increased discount to HLS. Some of the discount was associated with reduced gravity and increased discount was associated with reduced gravity and increased sulfur content. sulfur content.
DEPI began a process to determine whether TAN readings DEPI began a process to determine whether TAN readings were accurate and whether SLI crude was deserving of such were accurate and whether SLI crude was deserving of such a large discount.a large discount.
Test results of combined crude and of individual wells at Test results of combined crude and of individual wells at multiple labs created concerns about testing methodology multiple labs created concerns about testing methodology due to repeatability and accuracy issues. due to repeatability and accuracy issues.
History of Devils Tower TANHistory of Devils Tower TANHistory of Devils Tower TAN
Extreme TanExtreme TanExtreme Tan
In June 2006, Williams Pipeline reported to DEPI that the Total Acid Number (TAN) of Devils Tower crude was 2.4 mg KOH/g. In July, a Gulf Coast refiner heard it was 3.1.
Refiners purchasing South Louisiana Intermediate (SLI) began to do so at an increased discount to HLS. Some of the discount was associated with reduced gravity and increased sulfur content.
DEPI began a process to determine whether TAN readings were accurate and whether SLI crude was deserving of such a large discount.
Test results of combined crude and of individual wells at multiple labs created concerns about testing methodology due to repeatability and accuracy issues.
In June 2006, Williams Pipeline reported to DEPI that the In June 2006, Williams Pipeline reported to DEPI that the Total Acid Number (TAN) of Devils Tower crude was 2.4 mg Total Acid Number (TAN) of Devils Tower crude was 2.4 mg KOH/g. In July, a Gulf Coast refiner heard it was 3.1. KOH/g. In July, a Gulf Coast refiner heard it was 3.1.
Refiners purchasing South Louisiana Intermediate (SLI) Refiners purchasing South Louisiana Intermediate (SLI) began to do so at an increased discount to HLS. Some of the began to do so at an increased discount to HLS. Some of the discount was associated with reduced gravity and increased discount was associated with reduced gravity and increased sulfur content. sulfur content.
DEPI began a process to determine whether TAN readings DEPI began a process to determine whether TAN readings were accurate and whether SLI crude was deserving of such were accurate and whether SLI crude was deserving of such a large discount.a large discount.
Test results of combined crude and of individual wells at Test results of combined crude and of individual wells at multiple labs created concerns about testing methodology multiple labs created concerns about testing methodology due to repeatability and accuracy issues. due to repeatability and accuracy issues.
History of Devils Tower TANHistory of Devils Tower TANHistory of Devils Tower TAN
Quality control analysis found that labs were using different versions of ASTM D664 and that the sample preparation procedures were inconsistent or lacking.
A consistent sample prep procedure was developed to reduce repeatability and reproducibility errors.
Testing evolved to obtaining naphthenic acid measurements (Horvath-Gumulka and Carboxylic Acid Number) to directly measure the naphthenic acid content.
Comprehensive crude assays were obtained for Devils Tower and South Louisiana Intermediate.
Quality control analysis found that labs were using different Quality control analysis found that labs were using different versions of ASTM D664 and that the sample preparation versions of ASTM D664 and that the sample preparation procedures were inconsistent or lacking. procedures were inconsistent or lacking.
A consistent sample prep procedure was developed to A consistent sample prep procedure was developed to reduce repeatability and reproducibility errors.reduce repeatability and reproducibility errors.
Testing evolved to obtaining naphthenic acid measurements Testing evolved to obtaining naphthenic acid measurements (Horvath(Horvath--Gumulka and Carboxylic Acid Number) to directly Gumulka and Carboxylic Acid Number) to directly measure the naphthenic acid content.measure the naphthenic acid content.
Comprehensive crude assays were obtained for Devils Tower Comprehensive crude assays were obtained for Devils Tower and South Louisiana Intermediate. and South Louisiana Intermediate.
History of Devils Tower TANHistory of Devils Tower TANHistory of Devils Tower TAN
1.1 TAN test is intended for Petroleum Products and Lube Oils.
1.2 TAN used to indicate RELATIVE changes that occur under oxidizing conditions.
5.1 TAN used as a guide in quality control of lubricating oil formulations and a measure of lubricant degradation in service.
1.1 TAN test is intended for Petroleum Products and Lube 1.1 TAN test is intended for Petroleum Products and Lube Oils.Oils.
1.2 TAN used to indicate RELATIVE changes that occur 1.2 TAN used to indicate RELATIVE changes that occur under oxidizing conditions.under oxidizing conditions.
5.1 TAN used as a guide in quality control of lubricating oil 5.1 TAN used as a guide in quality control of lubricating oil formulations and a measure of lubricant degradation in formulations and a measure of lubricant degradation in service.service.
Intended Use of D664 TAN TestIntended Use of D664 TAN TestIntended Use of D664 TAN TestPer ASTM D664-06 TAN is “the quantity of base, expressed in milligrams of potassium hydroxide per gram of sample, required to titrate a sample in a specified solvent to a specified end point”.
Per ASTM D664Per ASTM D664--06 TAN is 06 TAN is ““the quantity of base, expressed in milligrams the quantity of base, expressed in milligrams of potassium hydroxide per gram of sample, required to titrate aof potassium hydroxide per gram of sample, required to titrate a sample in a sample in a specified solvent to a specified end pointspecified solvent to a specified end point””..
Refineries concerned about Naphthenic Acids that cause corrosion of carbon steel (at temperatures 450°-850°F).
ASTM D664 test is used as a proxy for Naphthenic Acid test.
Naphthenic Acid is generic name for organic acids in crude.
TAN test measures all “mobile protons” in the oil- Some are very problematic (Naphthenic Acids)- Some are not as problematic
EstersPhenolic compoundsLactonesResinsAgents such as inhibitors and detergents
Refineries concerned about Naphthenic Acids that cause Refineries concerned about Naphthenic Acids that cause corrosion of carbon steel (at temperatures 450corrosion of carbon steel (at temperatures 450°°--850850°°F).F).
ASTM D664 test is used as a proxy for Naphthenic Acid test.ASTM D664 test is used as a proxy for Naphthenic Acid test.
Naphthenic Acid is generic name for organic acids in crude.Naphthenic Acid is generic name for organic acids in crude.
TAN test measures all TAN test measures all ““mobile protonsmobile protons”” in the oilin the oil-- Some are very problematic (Naphthenic Acids)Some are very problematic (Naphthenic Acids)-- Some are not as problematicSome are not as problematic
EstersEstersPhenolic compoundsPhenolic compoundsLactonesLactonesResinsResinsAgents such as inhibitors and detergentsAgents such as inhibitors and detergents
Industry Use of D664 TAN TestIndustry Use of D664 TAN TestIndustry Use of D664 TAN Test
1.2 No general relationship known between bearing corrosion and acid number.
5.2 The test method cannot be used to predict corrosiveness of oil under service conditions.
5.2 No general correlation is known between acid number and the corrosive tendency of oil towards metals.
1.2 No general relationship known between bearing 1.2 No general relationship known between bearing corrosion and corrosion and acid number.acid number.
5.2 The test method cannot be used to predict 5.2 The test method cannot be used to predict corrosiveness of oil under service conditions.corrosiveness of oil under service conditions.
5.2 No general correlation is known between acid number 5.2 No general correlation is known between acid number and the corrosive tendency of oil towards metals.and the corrosive tendency of oil towards metals.
Misuse of ASTM D664 TAN TestMisuse of ASTM D664 TAN TestMisuse of ASTM D664 TAN Test
Per ASTM D664-06Per ASTM D664Per ASTM D664--0606
ASTM D664 is the industry standard (inexpensive test and puts burden of proof of its inaccuracy on the producer).
ASTM D664 TAN should be used as a screening test.- Low TAN – No problems.- High TAN – May or may not have problems.
– Additional testing necessary.
Per SET WebsiteCrude oils with a TAN higher than 0.5 are considered to be POTENTIALLY corrosive between the temperatures of 450°to 750° F. However, there are many cases including high velocity, high TAN and others where this rule of thumb breaks down and correlating the TAN to corrosivity is still far from being reached.
ASTM D664 is the industry standard (inexpensive test and ASTM D664 is the industry standard (inexpensive test and puts burden of proof of its inaccuracy on the producer).puts burden of proof of its inaccuracy on the producer).
ASTM D664 TAN should be used as a screening test.ASTM D664 TAN should be used as a screening test.-- Low TAN Low TAN –– No problems.No problems.-- High TAN High TAN –– May or may not have problems. May or may not have problems.
–– Additional testing necessary.Additional testing necessary.
Per SET WebsitePer SET WebsiteCrude oils with a TAN higher than 0.5 are considered to be Crude oils with a TAN higher than 0.5 are considered to be POTENTIALLY corrosive between the temperatures of 450POTENTIALLY corrosive between the temperatures of 450°°to 750to 750°° F. However, there are many cases including high F. However, there are many cases including high velocity, high TAN and others where this rule of thumb velocity, high TAN and others where this rule of thumb breaks down and correlating the TAN to corrosivity is still far breaks down and correlating the TAN to corrosivity is still far from being reached.from being reached.
Appropriate Use of TAN TestAppropriate Use of TAN TestAppropriate Use of TAN Test
Various Labs used different tests for TAN
- ASTM D664-04- ASTM D664-01 (significantly different)- Titrilube Test Kit (never tested on crude oil)
ASTM D664-06 is available (minor modification from –04)
Other, less common test methods are ASTM D974, UOP565 and UOP587
Various Labs used different tests for TANVarious Labs used different tests for TAN
-- ASTM D664ASTM D664--0404-- ASTM D664ASTM D664--01 (significantly different)01 (significantly different)-- Titrilube Test Kit (never tested on crude oil)Titrilube Test Kit (never tested on crude oil)
ASTM D664ASTM D664--06 is available (minor modification from 06 is available (minor modification from ––04)04)
Other, less common test methods are ASTM D974, UOP565 Other, less common test methods are ASTM D974, UOP565 and UOP587and UOP587
Potential Errors in TAN MeasurementPotential Errors in TAN MeasurementPotential Errors in TAN Measurement
Variation in ASTM D664 TAN TestsVariation in ASTM D664 TAN TestsVariation in ASTM D664 TAN Tests
0.05 0.35 1.30 1.30 1.66
8.6610.26 10.50
16.87
0
2
4
6
8
10
12
14
16
18
20
TAN
1 2 3 4 5 6 7 8 9
Different labs, different sampling, different preparation methodsDifferent labs, different sampling, different preparation methodDifferent labs, different sampling, different preparation methodss
Devils Tower XX WellDevils Tower XX WellDevils Tower XX Well
Samples should be taken free of additives if possible
- Defoamer and other Detergents- Low Density Hydrate Inhibitor (LDHI)- Paraffin Inhibitors et cetera
Samples should be adequately prepared
- Water wash to remove solubles- Remove all water possible (heat, demulsifier, centrifuge)- Small amounts of impurities can dramatically affect TAN
Samples should be taken free of additives if possibleSamples should be taken free of additives if possible
-- Defoamer and other DetergentsDefoamer and other Detergents-- Low Density Hydrate Inhibitor (LDHI)Low Density Hydrate Inhibitor (LDHI)-- Paraffin Inhibitors et ceteraParaffin Inhibitors et cetera
Samples should be adequately preparedSamples should be adequately prepared
-- Water wash to remove solublesWater wash to remove solubles-- Remove all water possible (heat, demulsifier, centrifuge)Remove all water possible (heat, demulsifier, centrifuge)-- Small amounts of impurities can dramatically affect TANSmall amounts of impurities can dramatically affect TAN
Potential Errors in ASTM D664 Sampling & Preparation
Potential Errors in ASTM D664 Potential Errors in ASTM D664 Sampling & PreparationSampling & Preparation
ASTM D664 and 2 other acid tests were run on each sample.
ASTM D664 tests on assay samples indicated TAN between 1.0 and 3.5 mg KOH/g in all cuts from 450º to 850º F.
Horvath-Gumulka Test (Naphthenic Acid Number) - Shell Global Solutions proprietary method of measuring crude acidity.
- Devils Tower crude tested ~8000 ppm, of which 45% was free acid. This corresponds to an acid equivalent of 1.44 mg KOH/g.
Carboxylic Acid Number Test (CAN) - Baker Petrolite proprietary method of measuring crude acidity.
- Devils Tower crude corresponds to acid equivalent of 1.45 mg KOH/g.
ASTM D664 and 2 other acid tests were run on each sample.ASTM D664 and 2 other acid tests were run on each sample.
ASTM D664 tests on assay samples indicated TAN between ASTM D664 tests on assay samples indicated TAN between 1.0 and 3.5 mg KOH/g in all cuts from 4501.0 and 3.5 mg KOH/g in all cuts from 450ºº to 850to 850ºº F.F.
HorvathHorvath--Gumulka Test (Naphthenic Acid Number) Gumulka Test (Naphthenic Acid Number) -- Shell Global Solutions proprietary method of measuring crude acShell Global Solutions proprietary method of measuring crude acidity.idity.
-- Devils Tower crude tested ~8000 ppm, of which 45% was free acidDevils Tower crude tested ~8000 ppm, of which 45% was free acid. This . This corresponds to an acid equivalent of 1.44 mg KOH/g.corresponds to an acid equivalent of 1.44 mg KOH/g.
Carboxylic Acid Number Test (CAN) Carboxylic Acid Number Test (CAN) -- Baker Petrolite proprietary method of measuring crude acidity.Baker Petrolite proprietary method of measuring crude acidity.
-- Devils Tower crude corresponds to acid equivalent of 1.45 mg KODevils Tower crude corresponds to acid equivalent of 1.45 mg KOH/g.H/g.
Potential Errors in TAN MeasurementPotential Errors in TAN MeasurementPotential Errors in TAN Measurement
Screening test OK?Screening test OK?Screening test OK?
Appropriate Use of TAN TestAppropriate Use of TAN TestAppropriate Use of TAN Test
No ProblemsNo ProblemsNo Problems
Appropriate screening test procedures?
Appropriate Appropriate screening test screening test procedures?procedures?
RetestRetestRetest
YesYesYes
NoNoNo
Yes – run detail testYes Yes –– run detail testrun detail test
WELL TEST OILWELL TEST OILWELL TEST OIL
Detail test OK?Detail test OK?Detail test OK?
NoNoNo
YesYesYes
NoNoNo
Address IssuesAddress IssuesAddress Issues
Protecting against corrosion from naphthenic acids requires either the use of corrosion resistant alloy materials in the overhead still columns or injection of a high temperature corrosion inhibitor.
Measure Naphthenic Acid specifically using:
- Horvath-Gumulka (SGS Proprietary Test)- Naphthenic Acid Titration (Baker Petrolite Test)
While performing Crude Assay, at various cuts:
- Measure TAN at each temperature- Assume ratio of Nap-acid to total TAN is constant
Protecting against corrosion from naphthenic acids Protecting against corrosion from naphthenic acids requires either the use of corrosion resistant alloy requires either the use of corrosion resistant alloy materials in the overhead still columns or injection of a materials in the overhead still columns or injection of a high temperature corrosion inhibitor. high temperature corrosion inhibitor.
Measure Naphthenic Acid specifically using:Measure Naphthenic Acid specifically using:
-- HorvathHorvath--Gumulka (SGS Proprietary Test)Gumulka (SGS Proprietary Test)-- Naphthenic Acid Titration (Baker Petrolite Test)Naphthenic Acid Titration (Baker Petrolite Test)
While performing Crude Assay, at various cuts:While performing Crude Assay, at various cuts:
-- Measure TAN at each temperatureMeasure TAN at each temperature-- Assume ratio of NapAssume ratio of Nap--acid to total TAN is constantacid to total TAN is constant
Addressing Refinery Corrosion ProblemsAddressing Refinery Corrosion ProblemsAddressing Refinery Corrosion Problems
Two industry majors provided current information on acid discounts that are applied to high TAN crudes - based on refinery processing costs and market perception.
Technical Discounts : $0.50 - $0.55/bbl per 1 TAN- Treating : $0.20/bbl- Segregation/Blending : $0.15 - $0.20/bbl- Metallurgy Investment : $0.15/bbl
Market Discounts : $1.00- $2.00/bbl per 1 TAN - Market Entry : $0.50/bbl- Hurdle Discount : $0.50/bbl
Expected Total Discount : $1.00 - $2.55/bbl per 1 TAN
Two industry majors provided current information on acid Two industry majors provided current information on acid discounts that are applied to high TAN crudes discounts that are applied to high TAN crudes -- based on based on refinery processing costs and market perception.refinery processing costs and market perception.
Technical Discounts : $0.50 Technical Discounts : $0.50 -- $0.55/bbl per 1 TAN$0.55/bbl per 1 TAN-- Treating : $0.20/bblTreating : $0.20/bbl-- Segregation/Blending : $0.15 Segregation/Blending : $0.15 -- $0.20/bbl$0.20/bbl-- Metallurgy Investment : $0.15/bbl Metallurgy Investment : $0.15/bbl
Market Discounts : $1.00Market Discounts : $1.00-- $2.00/bbl per 1 TAN $2.00/bbl per 1 TAN -- Market Entry : $0.50/bblMarket Entry : $0.50/bbl-- Hurdle Discount : $0.50/bblHurdle Discount : $0.50/bbl
Expected Total Discount : $1.00 Expected Total Discount : $1.00 -- $2.55/bbl per 1 TAN$2.55/bbl per 1 TAN
Enhancing Value of High TAN CrudesEnhancing Value of High TAN CrudesEnhancing Value of High TAN Crudes
Obtain sufficient test oil for assays and follow-up testing.
Confirm that a high TAN is caused by Naphthenic Acid.
Work Closely with Refiners.
- Provide testing results before and after well completion. - Convey value of crude (complete assay and comparison).- Propose cost sharing for injection of corrosion inhibitors.- Consider process changes to reduce charge rate & temp.- Evaluate blending and lease of refining capacity.- Consider cost sharing for upgrading construction materials
(last resort).
Obtain sufficient test oil for assays and followObtain sufficient test oil for assays and follow--up testing.up testing.
Confirm that a high TAN is caused by Naphthenic Acid.Confirm that a high TAN is caused by Naphthenic Acid.
Work Closely with Refiners.Work Closely with Refiners.
-- Provide testing results before and after well completion. Provide testing results before and after well completion. -- Convey value of crude (complete assay and comparison).Convey value of crude (complete assay and comparison).-- Propose cost sharing for injection of corrosion inhibitors.Propose cost sharing for injection of corrosion inhibitors.-- Consider process changes to reduce charge rate & temp.Consider process changes to reduce charge rate & temp.-- Evaluate blending and lease of refining capacity.Evaluate blending and lease of refining capacity.-- Consider cost sharing for upgrading construction materials Consider cost sharing for upgrading construction materials
(last resort).(last resort).
Enhancing Value of High TAN CrudesEnhancing Value of High TAN CrudesEnhancing Value of High TAN Crudes
Retain large quantity of test oil from new wells- Add TAN testing process map to standard quality tests.- Insure comprehensive assays include TAN values in each cut.
ASTM D664 TAN test is best used as a screening tool.- Controlled sampling, preparation and test procedures necessary.- High TAN from D664 does not always mean high corrosivity.- Precise Naphthenic Acid content not determined by ASTM D664.
Work Closely with Refiners to maximize value of high TAN crudes.
Retain large quantity of test oil from new wellsRetain large quantity of test oil from new wells-- Add TAN testing process map to standard quality tests.Add TAN testing process map to standard quality tests.-- Insure comprehensive assays include TAN values in each cut.Insure comprehensive assays include TAN values in each cut.
ASTM D664 TAN test is best used as a screening tool.ASTM D664 TAN test is best used as a screening tool.-- Controlled sampling, preparation and test procedures necessary.Controlled sampling, preparation and test procedures necessary.-- High TAN from D664 does not always mean high corrosivity.High TAN from D664 does not always mean high corrosivity.-- Precise Naphthenic Acid content not determined by ASTM D664.Precise Naphthenic Acid content not determined by ASTM D664.
Work Closely with Refiners to maximize value of high TAN crudes.Work Closely with Refiners to maximize value of high TAN crudes.
ConclusionsConclusionsConclusions
Presented by:
Clay CoeDirector, Oil Marketing & TradingDominion Exploration & Production, [email protected]
Presented by:Presented by:
Clay CoeClay CoeDirector, Oil Marketing & TradingDirector, Oil Marketing & TradingDominion Exploration & Production, Inc.Dominion Exploration & Production, [email protected][email protected]
Devils Tower TAN – A Case StudyDevils Tower TAN Devils Tower TAN –– A Case StudyA Case Study
