Paper No.

421

TEST METHODS FOR THE EVALUATION OF MATERIALS

FOR WET H2S SERVICE

H.H. Tang and M.S. Cayardhteftlm International, Inc.

P. O. Box 680666Houston, Texas 77268

USA

ABSTRACT

Two of the most common corrosion problems encountered in wet H2S service are sulfide stresscracking (SSC) and hydrogen-induced cracking (HIC). The problems related to SSC were firstrecognized in the late 1940s and early 1950s. The interest in SSC was vastly increased after the tubingftilure at Pincher Creek field in Alberta, Canada in 1949 and the well blowout at France’s Lacq fieldfollowing the failure of the drill pipe and casing in 1951. Following a series of sour service pipelinefailures in the Middle East in 1972 to 1974, the effect of HIC also caught the attention of the indust~.Since then, effort has been made to combat these problems by researching the mechanism related to SSCand HIC and methods to improve materials resistance to such damage. Test methods such as NACEStandard TMO177 [1] and TM0284 [2], were developed and standardized by NACE to facilitate theprocess of evaluating and testing material for wet H2S service. These two standards provide a solid basefor developing testing and research programs for materials evaluation and are two of the most widelyused standards for sour service qualification. In order to filly utilize these standards, understanding of thecorrosion and cracking mechanism and the usage of the standards are important. This paper attempts toaddress these issues and will discuss the background theories, proper usage, and limitation of thestandards. In additio~ intiormation will be given on typical acceptance criteria in terms of linking testresults to field applications.

Keywords : sulfide stress cracking, hydrogen-induced-cracking, hydrogen blistering, constant load,constant strai~ hydrogen damage.

Copyright@l999 by NACE International.Requestsforpermissionto publishthismanuscriptinanyform,inpal orinwholemustbe made inwritingto NACEInternational,ConferencesDivision,P.O. Box218340, Houston,Texas 77218-8340. The material presentedand the viewe expressed in thispaper are solely those of the author(s) and are not necessarilyendorsed by the Association.Printadin the U.S.A.

In this paper, two types of hydrogen related damage on material related to wet HJ3 serviceenvironment and their corresponding standard test methods will be discussed. The two types of damageare sulfide stress cracking (SSC) and hydrogen-induced cracking (HIC). NACE Standard TMO177,“Laboratory Testing of Metals for Resistance to Specific Forms of Environmental Cracking in H2SEnvironment”, was developed to facilitate conformity in testing of SSC so that data from differentsources could be compared on a common basis. The Standard was first developed by Task groupcommittee T-I F-9 in 1977, and the latest version was revised and released in 1996.

NACE Standard TM0284, “Evaluation of Pipeline and Pressure Vessel Steels for Resistance toHydrogen-Induced Cracking” was developed to evaluate the resistance of pipeline and plate steels tohydrogen-induced-cracking (HIC) and to provide a reliable test method for comparison of test data fromdifferent laboratories. This Standard was developed by task group T-lF-20 in 1984 and was last revisedin 1996. Discussion in this paper will be based on the latest version of both standards. The followingsections will discuss the background and theories of both SSC and HIC, the contents, proper usage, andsome of the limitations of the Standards, and summarizes some of the acceptance criteria used in theindustry.

BACKGROUND AND THEORIES

Sulfide Stress Cracking (SSC)

SSC is classified under environmental cracking (EC) and is a form of hydrogen embrittlementcracking. This phenomenon was first confi-onted by the refining industry in compressor components withhard weld deposits. It later became a significant problem in the upstream sector of oil and gas productionas the demand for high strength tubulars increased.

The reduction of hydrogen associated with the sulfide corrosion reaction of steel in wet H2Senvironments produces nascent hydrogen (IT) at the metal surface. The hydrogen atoms can combine toform molecular hydrogen (H2) and leave the surface as bubbles, or it can difise into the metal. Thesulfide in the environment acts as a cathodic recombination poison preventing the recombination ofhydrogen atoms, hence promoting hydrogen entry into the metal. Once the hydrogen atoms enter themetal, they diffise into the metal lattice and can lead to embrittlement. With the presence of tensile stress,cracking and failure of the metal can occur at stresses well below the material’s yield strength. It isimportant to recognize that SSC is a cathodic corrosion process. This is contrary to stress corrosioncracking (SCC), which is an anodic corrosion process. A photograph of a SSC fi-acture surface of atensile specimen is included in Figure 1. An arrow highlights the flat embrittlement region, where the SSCcrack initiated and propagated. The ductile region was the result of the final overload failure.

For SSC to occur, three elements are required, (1) a sufficient quantity of hydrogen in the metal,(2) a susceptible material, and (3) the presence of applied or residual tensile stress. SSC will not occur ifany one of these elements is not presence. A number of factors could affect a material resistance to SSC.These factors include the pH of the environment, H2S concentration, temperature, material strength,hardness, and applied residual stress. Understanding the effect of these factors plays an important role inevaluating materials for wet H2S service.

The pH, HZS concentratio~ and other species, such as chloride in the environment are highly

influential on SSC. The pH of the environment usually dictates the corrosion response of the metal.Lower pH tends to increase the corrosion rate of steel and increase the amount of hydrogen available fordiffhsion. Higher HZSconcentration promotes hydrogen charging and thereby increasing the severity ofthe situation. Other species, such as chloride, may increase corrosion by reducing the stability of surfacefilms.

Steel is most susceptible to SSC in the near room temperature. At higher temperatures,susceptibility to hydrogen embrittlement generally decreases resulting in a decrease in SSC susceptibility.High strength and high hardness material are more susceptible to SSC than lower strength materials. Thethreshold stress of SSC tends to be lower in the high strength materials. The existence of residual tensilestress resulting from cold working or welding processes will also increase the tendency for SSC ofsusceptible materials.

Hydrogen-Induced Cracking (HIC)

HIC is another form of hydrogen darnage (separate and distinct from SSC) which can result inwet H2S environments. HIC is also known as stepwise cracking. HIC is found in low strength pipelineand plate steels The production and difision of hydrogen occurs as previously described above.However, with respect to HIC, hydrogen atoms difise into the metal and become trapped at internaldiscontinuities where they recombine to form molecular hydrogen. With the increasing formation ofmolecular hydrogeq the pressure in the discontinuities builds up. The pressure subsequently createsdarnage by generating internal cracks and/or blisters. As cracks propagate, they tend to Iinkup and formstepwise cracking, which could propagate through the metal and reduce the effective load bearingcapacity of the metal. Such a crack array found in a pipeline or pressure vessel could cause rupture.Unlike SSC, applied and/or residual stress is not required for HIC. A micrograph of a typical HIC orstepwise cracking is shown in Figure 2.

Most of the environmental factors, such as pH, HzS concentration, and temperature, that aiYbctSSC susceptibility are also applicable to HIC. The effect of temperature on HIC is somewhat lessdramatic than observed with SSC. However, the role of metallurgical parameters in HIC can be muchdifferent than they are for SSC. HIC tends to be more significantly afl’ected by material cleanliness withreduced susceptibility associated with lower sulfir levels. On the other hand, SSC tends to be morestrongly influenced by strength (hardness) and microstructure as discussed previously herein. Therefore, itis important to realize that metallurgical processing can influence HIC and SSC susceptibility in differentways. Although applied and/or residual stress is not required for HIC, through thickness crack linkup ispromoted by the presence of tensile stress. This residual or applied tensile stress can lead to a particularform of HIC referred to as stress oriented hydrogen-induced cracking (SOHIC).

NACE TM0177 TEST METHODS

NACE Standard TMO177 was developed to evaluate material for susceptibility to sulfide stresscracking in wet H2S environments. The latest version of the standard also includes procedures forevaluating material for stress corrosion cracking (SCC), but the discussion of SCC and its correspondingprocedures in the Standard is outside the scope of this paper. Four different test methods, &B, C and Dare included in the Standard. Each test method has its own unique testing configuration and involvesslightly different environmental elements. These test methods are the uniaxial tensile test, bent beam test,

C-Ring test, and Double Cantilever Beam (DCB) test for Methods & B, C, and D, respectively. Theselection of test method is based on the preference of the user and the method that is best suited for thematerial application.

All the methods share some common procedures and requirements. All the test solutions used inthe Standard are deaerated, and include the use of 100 percent H2S gas. Exclusion of oxygen is a crucialpart of SSC testing. Oxygen contamination of the environment will promote pitting on the specimen andproduce an invalid test. Oxygen contamination can be detected by the milky appearance of the testenvironment caused by the formation of colloidal sulfbr. The specimens proposed by each standard arerequired to have a surface finish of O.81ym (32 pin) or finer, Good sutiace finish is essential. Poorsurface finish creates surface irregularity that could result in premature failure. In addition, all thestandard SSC tests are designed to be conducted at atmospheric pressure and room temperature(i.e. 24 ~ 2 C). This is generally the most aggressive temperature as discussed in the previous section.Special procedures are included in the latest version of the Standard for elevated temperature tests andfor tests with various levels of H2S concentration. The details for each test method are discussed in thefollowing section.

NACE TM0177-96, Method A

NACE TMO177-96, Method A provides procedures for conducting a uniaxial SSC tensile test.The tensile specimen is loaded to a specific stress level at or below the material’s yield strength in tensionand exposed to a wet HzS environment for up to 30 days. Proof-ring and dead-weight testers are two ofthe most commonly used apparatus for this method. The former is becoming more popular due to itscompact size. Photographs of the Proof-ring testers are shown in Figures 3. Method A is a reliable testmethod and was shown to produce repeatable results among different laboratories when taking intoaccount the variance in test procedure at the time of study [3]. It is a very popular method for qualifyingmaterial such as high strength pipe and casing for oil and gas production and is specified in API 5CTSpecification [4].

Two different size tensile specimens are used by this method. The standard fill size specimen hasa 6.35 mm gage diameter and a 25.4 mm gage length, and sub-size specimen has a 3.81 mm gagediameter and 25.4 mm gage length. The selection of specimen is generally limited by the size of theavailable material and the specimen removal location or orientation. Standard fill size specimens arepreferred. The use of sub-size specimens may produce more severe cracking when it is used to testcarbon steel material. The corrosion of the specimen reduces the cross-sectional area of the specimenhereby resulting in an increase in stress experienced by the specimen. Hence, the time dependent nature ofcorrosion can lead to ftilures of sub-size specimens. This corrosion effect is less significant in the fill sizespecimen due to the larger cross-sectional area and corresponding smaller stress elevation. Therefore, theresults from the two types of specimens may not be directly comparable.

Two solutions are given in the latest version of Method A. Solution A has an initial pH of 2.6 to2.8, and Solution B has an initial pH of 3.4 to 3.6. Solution A is the original solution used in the firstversion of the Standard, and it has been widely accepted by the industry. Solution B was added to the1996 version of the Standard. Both solutions are saturated with 100 percent HJ5 gas. Bubbling HJ3continuously in the solution is used to control the pm maintain the HzS concentratio~ and also serves toprevent oxygen contamination during exposure.

Test Method A produces pass / fail test results and time-to-failure itiormation. Specimens areconsidered to be ftilures if they fracture or crack during the 30 day exposure period. Results fi-om afracture outside of the gage section should be considered invalid since the stress state at the locationoutside of the gage section is not well defined. The time-to-failure data collected for a set of specimenstested at different stress levels can be used to identi~ the SSC threshold limit of the material. Previousstudies suggest that SSC of carbon steel is logarithmically related to time [3]. The SSC threshold limit ofa material is defined as the highest stress level the material can sustain in the given environment withoutfailure during the test period.

It is important to note that this method was originally developed for evaluating predominantlyhigh strength low alloy steels. When using this method to evaluate other alloy materials, such as stainlesssteel or nickel base alloys, caution must be taken. Unlike low alloy steel, higher alloy materials possess aprotective oxide film which provides resistance to environmental cracking. The stability of the film and itsability to self repair is an important factor that is not addressed in this method. Damage to the film canlead to localized attack increased hydrogen charging, and/or cracking. The localized corrosion alsoproduces stress concentrations, promoting cracking, and possibly eventual ftilure. Although theformation of localized corrosion is not a failure criteria in the method, the potential for pit to develop intoa crack is considerable. Therefore, the user needs to examine the test acceptance criteria careii.dly andmake sound judgment accordingly when using this method to evaluate such materials.

NACE TMO177-96, Method B.

Method B is the bent beam test. A version of this test method was first published by Fraser,Eldredge, and Treseder [5] in an attempt to quantitatively study SSC. This method employs multiple bentbeam specimens containing stress risers (i.e. drilled holes). The specimens are loaded to different“pseudo-stress” levels in three point bending, and they are exposed to a wet HJJ environment for 30 days.The pass / fd results are statisticallyanalyzed to generate a critical stress value. It is important to keep in mindthat this test method is not designed to be a pass/ fail type of test based on individual specimen results. Theperformance of the material is measured based on the prevailing critical stress, SC,determined from statisticalanalysisof the pass/ fti results.

The test specimen consisted of 67.3 mm long by 4.57 mm wide by 1.52 mm thick bent beam withtwo No. 70 holes (stress risers) located at the transverse centerline. The stress risers serve to increase thelocal stress concentration. Constant deflection fixtures, such as the one shown in Figure 4, are used toapply the three point loading to the specimen. In a typical test program 12 or more specimens are needed,and they are loaded to different pseudo stress levels. Pseudo stress levels are determined based on thehardness of the material evaluated. The pseudo stress does not represent the actual outer fiber stressexperienced by the specimen since the equation used in the method does not account for the stressconcentration and local plasticity produced by the holes.

The test environment used in Method B is different than the environments stated in Method A.The test solution used in Method B has 5 weight percent acetic acid in distilled water with no additionalsodium chloride. The sodium chloride is intentionally left out to reduce the corrosion rate which wouldlead to stress elevation due to reduction in thickness. Moreover, the HJ3 gas in the solution is replenishedby an intermittent purge instead of continuously purging throughout the test duration as in the othermethods given in TMO177. Because of the lack of a continuous purge, the user needs to pay moreattention to the exclusion of oxygen in the system during the exposure. The initial and final pH of thesolution are not specified in this method but are defined by the specification of the test environment.

A set of 12 or more specimens are normally used to evaluate each material. The pseudo stresslevels are selected such that approximately half of the specimens complete the test without ftilure. Thespecimens are considered ftilures if they fracture during the test or a crack is found on the tension surfaceof the specimen following exposure. Cracking is detected by bending the specimen to a 20-degree angle,and examining the surface at 10x magnification. The pass / ftil results are then used to calculate thecritical stress, SC.

NACE TM0177-96, Method C

Method C is the NACE C-Ring Test. This method utilizes the C-ring specimen by stressing theouter diameter of the specimen in tension and exposing the specimen to a wet H2S environment for up to30 days. This method was developed to evaluate material resistance to circumferential loadiig. It is especiallysuitable for testing of tubing, round bar, or small diameter pipe, where difkulty in removing tensile specimensexists.

The C-Ring specimen dimensions are constrained by the specimen’s width-to-thickness ratio andthe outer diameter-to-thickness ratio defined in the Standard. These two ratios determine the variation ofcircumferential stress across the width of the C-Ring specimen versus the specimen defection. A drawingof the C-Ring specimen is shown in Figure 5. A fine polish finish or as-fabricated finished is acceptable inthis method. Both Solution A and Solution B described in Method A are acceptable in this method.Continuous HJ3 gas purging is required throughout the test duration. Multiple specimens arerecommended at each test and stress condition.

The failure of the specimen is defined as rupture of the specimen or cracking observed on thetension surface at 10x magnification following exposure. Mechanically overstressing of the specimen afterthe exposure can be used to reveal the presence of cracking. This method provides the pass/ ftil result ata particular stress level.

NACE TM0177-96, Method D

Method D uses a fracture mechanic approach to evaluate material resistance to sulfide stresscracking. This method utilities the crack arrest method to generate a stress intensity factor, KISSC, toquantifj the materials ability to resist or arrest sulfide stress cracking. Unlike the first three methodsdiscussed above, cracking should always occur in this method, and the crack propagation / arrestresponse of the material is evaluated. Hence, the result of this method does not depend on any pass/ ftilevaluation. In this method, a double-cantilever-beam (DCB) specimen with an artificial crack is loaded tocertain defections and exposed to a wet HJ3 environment. The duration of the exposure is 14 days forcarbon and low alloy steel, and it should be at least 30 days for stainless steel or higher alloy steels. A longertest duration for the higher alloy steels may be necessaryto ensure crack has filly arrested.

There are two types of DCB specimens recommended by the method. Both types of specimensshare the same general dimensions, but have different artificial crack f=tures (i.e. either a chevron crackstarter or an electrodischarge-machined (EDM) slot). A drawing of the chevron crack starter specimen isshown in Figure 6. The chevron crack may also be supplemented with fatigue precracking. The loadingon the crack front is generated by a wedge, which dictates the arm displacement of the specimen. Therequired arm displacement for crack propagation is related to the type and strength of the material ofinterest and its likely susceptibility to cracking. The suggested arm displacements included in the method

are determined fi-om past experience. The ideal arm displacement will generate enough force to initiatecrack propagation and allow the crack to arrest within the exposure period. Both Solutions A and B ofMethod A are allowed in this method. Continuous H2S purging is also required throughout the testduration.

In order to determine the stress intensity factor, the corresponding lifloff load, and the total cracklength resulting from the exposure need to be measured. Before the determination of K1ssc, the fracturesurface is examined for any undesired features, such as crack pinning, crack branching and insufficientcrack propagation. The detection of any undesired feature will invalidate the test result. The stressintensity factor is calculated using the liftoff load and crack length results.

NACE TM0284 TEST METHOD

NACE Standard TM0284 was developed to evaluate pipeline steel and plate steel for wet HZSapplications. This method was specifically designed to evaluate material resistance to HIC. It provides aquantitative approach to characterize internal HIC and creates a basis for comparing results generated bydifferent laboratories. There are four major steps involved in conducting a HIC test as described in theStandard. They are test specimen removal, test environment control, sample preparation, and crackmeasurement. These steps are discussed in the following paragraphs.

There are two separate specimen removal criteria for testing pipe steel or plate steel. For testingof pipe steel, a set of three full thickness specimens are removed around the pipe diameter of each pipe.The specific specimen removal locations vary depending on pipe manufacturing process, such as seamlesspipe, ERW pipe, longitudinally welded pipe, and spiral-welded pipe as stated in the Standard. For testingof plate steel, the number of specimens and specimen removal locations are determined by the thicknessof the plate evaluated. The standard HIC specimen measures 100 mm long by 20 mm wide. The thicknessof the specimen is determined based on the thickness of the pipe or plate. A surface finish equivalent to320 grit with all the mill scale removed is also required for a consistent evaluation. Close attention todeaeration procedures should also be maintained.

The HIC exposure test is conducted in either of the two solutions recommended in the standardwith 100 percent HzS saturation for 96 hours. Solution A of this standard has the same composition asthe Solution A used in the NACE TMO 177-96 Standard. Solution B is an ASTM synthetic seawatersolution, that was included in the first version of the Standard. Solution A is a low pH solution and it is amore aggressive environment compared to Solution B. Continuous H2S gas purging is also requiredthroughout the test duration to maintain H2S saturation and exclusion of oxygen. As in most testinginvolving H2S gas, oxygen contamination is undesirable.

Blistering on the wide surface of specimens may result from the exposure. However, the Standardspecifically excludes any guidelines for evaluating of surface blistering. Each of the three specimens issectioned into four equal length sections and the three internal surfaces are polished for examination.Therefore, a total of at least nine surfaces (sections) are evaluated for each material evaluation.Metallographic preparation for cracking examination is an important part of the test. A consistent andsystematic grinding and polishing procedure is necessary to produce reliable results. Although no detailedpolishing procedures are included in the Standard, ASTM E3 Standard [6] can be referenced foracceptable practices on metallographic preparation.

Thepolished sufiaces weevduated using mopticd microscope atma@fications up to lOOX.The length and width of each individual crack in each section are measured based on the criteria listed inthe Standard. The polished surface may be lightly etched to distinguish the cracks from other features,such as inclusions and scratches. Based on the crack measurements, the crack sensitivity ratio (CSR),crack length ratio (CLR), and crack thickness ratio (CTR) for each section are evaluated and averagedfor each specimen and a set of specimens. Figure 7 includes drawings ilom the Standard that illustratesthe measurement and calculation of these ratios. CSR is a ratio which characterizes the cracked area withrespect to the overall section surface area. CLR is a ratio which characterizes the sum of all crack lengthswith respect to the overall width of the section. CTR is a ratio which characterizes the sum of all crackwidths with respect to the overall thickness of the section. These three ratios are the quantitative resultsused to characterize the peflorrnance of the material. No pass / failure criteria are included in theStandard. Detection of cracking or blisters does not necessarily constitute a fhilure. The ratios aregenerally compared against acceptance criteria provided or imposed by the user of the material.

ACCEPTANCE CRIETRIA

Both TMO177 and TM0284 Standards serve as a guideline for conducting SSC and HIC testing,respectively, but no acceptance criteria are included in either of the Standards. The acceptance criteria aregenerally set by the user. The criteria should be based on the design requirements of the applicationand./or in many cases, correlation with past experience. Many of the acceptance criteria were establishedbased on past experience and data generated from previous studies. Setting appropriate acceptancecriteria is essential for the evaluation process. Understanding of the testing mechanism and relating theresults to the intended application is important. A list of typical industry acceptance criteria for both SSCand HIC are included in Tables 1 and 2, respectively for reference. The acceptance criteria for SSC testconducted on high strength casing and tubing for sour services is specified by API [4]. Thus fw criteriaare only given for test conducted according to NACE TMO177, Method A. However, works are inprogress to generate criteria for Methods B and D. There currently exists no single acceptance level fortest conducted for HIC per TM0284. Individual end user (steel purchaser) utilize test solutions andacceptance criteria based on the severity and criticality of the application. As shown in Table 2,acceptance criteria can vary substantially from application to application and among various end users.

CONCLUSIONS

In order to select material for wet HJS applications, an engineer needs to identi& an appropriatetest method to evaluate candidate materials. Armed with the knowledge of corrosion science and theunderstanding of the established test methods will facilitate the material selection process. Moreimportantly, the knowledge will enable one to identi~ potential problems and investigate solutionsthrough research and testing. This paper did not address all the potential corrosion problems one willencounter in wet HJ3 services, but serve as an introduction to two of the widely encountered mechanismsand their respective evaluation procedures.

ACKNOWLEDGMENTS

The authors of this paper would like to acknowledge the technical contributions of Dr. Russell Kane andthe support from the staff of hteOm International, Inc.

1. NACE Standard TMO177, “Laboratory Testing of Metals for Resistance to Specific Forms ofEnvironmental Cracking in H2SEnvironments”, NACE International, Houston, Texas 1996.

2. NACE Standard TM0284-96,’’Evaluation of Pipeline and Pressure Vessel Steels for Resistance toHydrogen-Induced Cracking”, NACE International, Housto~ Texas 1996.

3. J.B. Greer, “Results of Interlaboratory Sulfide Stress Cracking Using the NACE T-l F-9 ProposedTest Method”, Presented during Corrosion/75, April, 1975, Toronto, Ontario, Canada.

4. API Specification 5CT, “Specification for Casing and Tubing”, fifth Edition, April 1, 1995.5. J.P. Fraser, G.G. Eldredge, and R.S. Treseder, “Laboratory and Field Methods for Quantitative Study

of Sulfide Corrosion Cracking”, A paper presented at the Fourteenth Annual Conference, NationalAssociation of Corrosion Engineers, San Francisco, California, March 17-21, 1958.

6. ASTM Standard E3-95, “Methods of Preparation of Metallographic Specimens”, 1995 Annual Bookof ASTM Standards, Volume 03.01.

——_

FIGURE 1- Fracture Surface of a SSC Tensile Specimen

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FIGURE 2- Typical Hydrogen-Induced Cracking at 50X

B-

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2 holescentered*G,0G2°

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4 E

FICRJRE 5- C-Ring Specimen

Y-l- +

5 ~j&=+==‘Slot G

— —

D+I

!

i1[1IllII

1 /

z f?odius K TypicalEoth Sides(m:lling Cutter)

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li!llA45._50.

\ Groove

Root Radius

Section Y–YSection Z–Z

FIGURE 6- Chevron Crack Starter DCB Specimen

Crack Sensitlwty Roto, CSR =z(. xb) ~loo

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Crock Length Rotco, CLR =x.

x 10Cw

Crock Th, ckness Eotio, CT!? = Zb— x 10C

Method Of Meosuring Crock, ng Sever, ty

FIGURE 7- HIC Measurement and Calculation [2]

TABLE 1- SAMPLE SSC ACCEPTANCE CRITERIA

Test Method API Proposed Acceptance Criteria for C90 and T95 Qualification(l)

A 80% of SMYS or 72%(2)of SMYS

B Sc >120 for C-90 OrSC>126 for T95 (1)

c Not Proposed ‘1)

D KISSC232.0 or 30.0(3) &&2 (1)

(1) - The proposedcriteriaare still in reviewingprocessandhavenot beenapprovedyet.(2) - Criteriafor sub-sizespeeimen(stillpendingfor approval).(3) - Criteriafor alternate specimen.

TABLE 2- SAMPLE HIC ACCEPTANCE CRITERIA

Major US Oil Companyl Western Canada2 North Slope3

CSR <1.5 0/0 Not Needed Reported

CLR <15 0/0 ~ 50/0 < 100/0

cm ~ 5 0/0 <1.5 0/0 ~ 10/0

1. Test conducted using Solution A with initial pH of 2.9- 3.3 and final pH of 3.5- 4.02. Test conducted using Solution A with initial pH of 2.6- 2.8 and final pH of 2.6- 3.73. Test eondueted using Solution A