1、 Screening Tests for Evaluating the Effectiveness of Gypsum Scale Removers This NACE International standard represents a consensus of those individual members who have reviewed this document, its scope, and provisions. Its acceptance does not in any respect preclude anyone, whether he or she has ado
2、pted the standard or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not in conformance with this standard. Nothing contained in this NACE standard is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in conne
3、ction with any method, apparatus, or product covered by letters patent, or as indemnifying or protecting anyone against liability for infringement of letters patent. This standard represents minimum requirements and should in no way be interpreted as a restriction on the use of better procedures or
4、materials. Neither is this standard intended to apply in all cases relating to the subject. Unpredictable circumstances may negate the usefulness of this standard in specific instances. NACE assumes no responsibility for the interpretation or use of this standard by other parties and accepts respons
5、ibility for only those official NACE interpretations issued by NACE in accordance with its governing procedures and policies which preclude the issuance of interpretations by individual volunteers. Users of this NACE standard are responsible for reviewing appropriate health, safety, environmental, a
6、nd regulatory documents and for determining their applicability in relation to this standard prior to its use. This NACE standard may not necessarily address all potential health and safety problems or environmental hazards associated with the use of materials, equipment, and/or operations detailed
7、or referred to within this standard. Users of this NACE standard are also responsible for establishing appropriate health, safety, and environmental protection practices, in consultation with appropriate regulatory authorities if necessary, to achieve compliance with any existing applicable regulato
8、ry requirements prior to the use of this standard. CAUTIONARY NOTICE: NACE standards are subject to periodic review, and may be revised or withdrawn at any time in accordance with NACE technical committee procedures. NACE requires that action be taken to reaffirm, revise, or withdraw this standard n
9、o later than five years from the date of initial publication and subsequently from the date of each reaffirmation or revision. The user is cautioned to obtain the latest edition. Purchasers of NACE standards may receive current information on all standards and other NACE publications by contacting t
10、he NACE FirstService Department, 1440 South Creek Dr., Houston, TX 77084-4906 (telephone +1 281-228-6200). Reaffirmed 2012-12-13 Reaffirmed 2002-04-11 Approved 1997-10-11 NACE International 1440 South Creek Dr. Houston, Texas 77084-4906 +1 281-228-6200 ISBN 1-57590-044-0 2012, NACE International NAC
11、E Standard TM0397-2012 Item No.21230 TM0397-2012 TM0397-2012 NACE International i _ Foreword Hydrocarbon production is often accompanied by the production of a brine. Minerals may precipitate from a brine and deposit within the production system. The scale deposits can be located both downhole and i
12、n surface equipment. Often the deposit has an adverse effect on production and must be removed. Producers and service companies devote considerable effort to developing and marketing effective treating chemicals because of the serious impact that gypsum (CaSO4 2H2O) scale formation can have on hydro
13、carbon production. The performance of these treating chemicals used for scale removal can be verified most effectively after an actual field trial. However, field testing can be very difficult and time-consuming, especially when many chemicals are being evaluated. Although most laboratory tests cann
14、ot exactly duplicate field conditions, the advantage of such tests is to provide the user with a comparison of the performance of one scale remover against that of another under standard laboratory conditions. The industry has not established a standard test method to evaluate gypsum scale removers.
15、 Consequently, performance tests on a scale remover or collection of scale removers yield widely differing absolute and relative results depending on the test procedure used. NACE Unit Committee T-1D formed Task Group T-1D-32 in 1987, in response to an expressed need for a standard test method for t
16、he evaluation of chemical-based gypsum scale removers. The initial task group assignment was to compose and publish a technical committee report. That report was issued in 1991 (NACE Publication 1D1911). The subsequent assignment was to develop standard test methods for screening gypsum scale remove
17、r chemicals, which are addressed in this standard. This standard presents test methods for screening the effectiveness of two types of gypsum scale removers, one for scale dissolvers, and another for scale converters. These methods are primarily intended for use by those in the petroleum industry wh
18、o need to use treating chemicals to remove gypsum scale deposits. This NACE standard was originally prepared in 1997 by Task Group T-1D-32, a component of former Unit Committee T-1D on Corrosion Monitoring and Control of Corrosion Environments in Petroleum Production Operations. It was reaffirmed in
19、 2002 by Specific Technology Group (STG) 31 on Oil and Gas ProductionCorrosion and Scale Inhibition and it was reaffirmed in 2012 by STG 31 on Oil and Gas ProductionCorrosion and Scale Inhibition. It is issued by NACE International under the auspices of STG 31. In NACE standards, the terms shall, mu
20、st, should, and may are used in accordance with the definitions of these terms in the NACE Publications Style Manual. The terms shall and must are used to state a requirement, and are considered mandatory. The term should is used to state something good and is recommended, but is not considered mand
21、atory. The term may is used to state something considered optional. _ TM0397-2012 ii NACE International _ NACE International Standard Test Method Screening Tests for Evaluating the Effectiveness of Gypsum Scale Removers Contents 1. General . 1 2. Gypsum Scale Dissolver Screening Test 1 3. Gypsum Sca
22、le Converter Screening Test 3 4. Calculations . 5 References 6 Appendix A (Nonmandatory): Procedure for Making Compressed Gypsum Pellets . 6 _ TM0397-2012 NACE International 1 _ Section 1: General 1.1 The test methods described in this standard are static laboratory screening tests designed to measu
23、re the ability of chemicals to remove gypsum scale deposits. There are two types of scale-removal chemicals: dissolvers and converters. Scale dissolvers, generally chelating or sequestering agents, can affect the dissolution and removal of gypsum scale in one step. Converters, such as those formulat
24、ions based on sodium (or potassium) glycolate and sodium (or ammonium) carbonate (or bicarbonate), are used to alter or convert the calcium sulfate to another compound which is then removed by dissolution with a dilute mineral acid (typically hydrochloric acid). Test methods for screening both gypsu
25、m scale dissolvers and converters are described. 1.2 These test methods are recommended only for ranking the performance of different scale-removal chemicals under the laboratory conditions set by these test methods. 1.3 Many factors such as reaction kinetics, fluid velocity, temperatures and pressu
26、res, scale surface area, and scale composition can significantly affect scale removal under field conditions. Detailed consideration of these parameters is outside the scope of this standard. However, field conditions, field brine composition, and others noted above should be considered at some poin
27、t in the evaluation prior to final selection of a scale remover for field use. 1.4 Tests can be conducted using varying amounts of gypsum to obtain a better comparison of scale removers under the laboratory conditions set by these test methods. The actual ratio of scale remover to gypsum required fo
28、r a field application may be different from that established by these test methods. 1.5 This standard lists the necessary apparatus, reagents, and procedures for conducting screening tests of both gypsum dissolvers and converters. 1.6 A reference scale dissolver, tetrasodium ethylene-diaminetetraace
29、tate (Na4EDTA), or a reference scale converter, potassium glycolate (the potassium salt of hydroxyacetic acid, HOCH2 COOK), is run along with the scale removers being screened. The test results obtained using a reference chemical of known scale-removal capacity provide a benchmark to verify that the
30、 screening test procedures were properly conducted. _ Section 2: Gypsum Scale Dissolver Screening Test 2.1 This section lists the equipment and procedure for conducting the gypsum scale dissolver screening test. 2.2 Equipment and Solutions 2.2.1 Constant-temperature water bath or forced-draft oven c
31、apable of maintaining the specified temperature within 1 C. 2.2.2 60 mL wide-mouth glass bottles with caps that will not react with the test solutions and that will provide an airtight seal. These bottles shall be clean of any contaminating material and shall be dry. 2.2.3 Apparatus for delivering 5
32、0.0 0.5 mL, e.g., graduated cylinders or volumetric pipets. 2.2.4 Vacuum filter flask, 0.45 m membrane filters (47 mm diameter), and filter holder assembly. 2.2.5 Laboratory balance and miscellaneous equipment to weigh, handle, and transfer solids. The balance shall be capable of measurement to 0.01
33、 g or better. 2.2.6 ACS(1)reagent grade gypsum powder (CaSO4 2H2O).2 2.2.7 Undiluted and diluted (1:1 vol in distilled or deionized water) solutions of the scale dissolver(s). 2.2.8 A 200 g/L solution of reagent grade Na4EDTA. This will be used as a reference scale dissolver with a known gypsum-diss
34、olving capacity to verify that the test operator is conducting the screening test procedures properly and consistently. (1) American Chemical Society (ACS), 1155 16th St. NW, Washington, DC 20036. TM0397-2012 2 NACE International 2.3 Test Procedure. The test procedure shall consist of the following
35、steps: 2.3.1 Using weighing paper or its functional equivalent, weigh and record the weights of 12 samples, each 10.0 0.05 g, of ACS reagent grade gypsum powder. This allows for duplicate tests of a scale dissolver, which shall be run diluted and undiluted, and a reference sample, which shall be run
36、 at one concentration only, at two temperatures, 25 C and 50 C. 2.3.2 Add 50.0 mL of undiluted scale dissolver to each of four 60 mL bottles. Add 50 mL of diluted (1:1 vol in either deionized or distilled water) dissolver to each of four other bottles. Transfer the first preweighed 10 g gypsum sampl
37、e to the first bottle, seal the bottle, and shake vigorously for approximately 10 s. Ensure that all the powder is thoroughly wetted, dispersed, and submerged within the test solution. Without delay, continue with the remaining seven bottles in a similar manner. 2.3.3 Add 50.0 mL of the reference Na
38、4EDTA scale dissolver to each of four 60 mL bottles. Transfer a preweighed 10 g gypsum sample to the first bottle, seal the bottle, and shake vigorously for approximately 10 s. Ensure that all the powder is thoroughly wetted, dispersed, and submerged within the test solution. Without delay, continue
39、 with the remaining three bottles in a similar manner. 2.3.4 Ensure that all bottles are tightly sealed and place duplicates of each dissolver sample (undiluted, diluted, and reference) into a 25 C oven or water bath. Place the remaining six samples in a 50 C oven or water bath. 2.3.5 Allow the bott
40、les to remain undisturbed for 24 hours. Try to minimize vibration of the equipment in order to reduce effects caused by minor amounts of agitation. Avoid agitation of the sample bottles in the water bath. 2.3.6 After completing the test, samples that were heated to 50 C must be cooled to 25 C prior
41、to the analysis for scale dissolver efficacy. Flowing 25 C tap water in a shallow tray (the height of which is about that of the test bottles) for 10 min may be used for this purpose. Alternatively, a circulating water bath may be used. 2.4 Analysis Spectroscopically analyze for Ca2+ in solution (Pa
42、ragraph 2.4.1, below) or use the gravimetric analysis procedure (steps a through d in Paragraph 2.4.2, below). Some chemicals may produce reaction products that are not easy to filter. In such cases, spectroscopic analysis may be the only reasonable alternative. The test operator shall specify which
43、 method of analysis was used. 2.4.1 Spectroscopic Analysis If calcium analyses are to be done spectroscopically, briefly shake the test bottle and filter an appropriate volume of the liquid to be analyzed through a 0.45 m membrane filter (47 mm diameter).(2) Carry out the analyses and skip to Paragr
44、aph 2.5. 2.4.2 Gravimetric Analysis Before proceeding with steps (a) through (d) below, prepare 1 L of a saturated gypsum solution for each chemical tested. This solution can be prepared by stirring a 3 g/L slurry of ACS reagent grade gypsum powder in either distilled or deionized water for several
45、hours at room temperature. Decant the supernatant solution and then, by applying vacuum or pressure, filter the supernatant solution through a 0.45 m membrane filter (47 mm diameter). (Use of a fibrous prefilter may reduce the filtration time.) (a) Record the weight of a 0.45 m membrane filter and p
46、osition it in the filter holder assembly. Using 25 to 50 mL of the saturated gypsum solution (this solution can be conveniently dispensed from a plastic wash bottle), rinse each bottle free of solids, transferring the solids and solution into a filter holder assembly. Applying vacuum or pressure, pa
47、ss the fluids through a preweighed 0.45 m membrane filter (47 mm diameter). (b) Using 25 to 50 mL of either deionized or distilled water, flush the dissolver solution from the membrane filter. (c) When no more liquid passes through the filter, transfer the solids-covered filter to a small labeled be
48、aker, bottle, or petri dish. (2) Cellulose acetate filters are most commonly used; however, a more resistant material may be required depending on the chemical being performance tested. The chemical compatibility of a filter can be tested by exposing the filter to the chemical in question. A weight loss or an unacceptably slow flow rate (caused by swelling of the filter polymer) would indicate an incompatibility between filter and che
