1、Designation: D4525 131Standard Test Method forPermeability of Rocks by Flowing Air1This standard is issued under the fixed designation D4525; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in pa
2、rentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTEEditorial corrections were made throughout in February 2014.1. Scope*1.1 This test method covers the determination of the coef-ficient of specific permeab
3、ility for the flow of air throughrocks. The method establishes representative values of thecoefficient of permeability of rocks or well-indurated soils.1.2 This test method is limited to permeability valuesgreater than 9.869 10-18m2(0.01 millidarcy), and is limitedto rocks free of oil or unctuous ma
4、tter.1.3 UnitsThe values stated in SI units are to be regardedas the standard.The values given in parentheses are mathemati-cal conversions to inch-pound units that are provided forinformation only and are not considered standard. Reporting oftest results in units other than SI shall not be regarded
5、 asnonconformance with this test method.1.4 All observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D6026.1.4.1 The procedures used to specify how data are collected/recorded or calculated, in this standard are regarded as theindus
6、try standard. In addition, they are representative of thesignificant digits that generally should be retained. The proce-dures used do not consider material variation, purpose forobtaining the data, special purpose studies, or any consider-ations for the users objectives; and it is common practice t
7、oincrease or reduce significant digits of reported data to becommensurate with these considerations. It is beyond the scopeof this standard to consider significant digits used in analyticalmethods for engineering design.1.5 This standard does not purport to address all of thesafety concerns, if any,
8、 associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D653 Terminology Relating to Soil, Rock, and Contain
9、edFluidsD3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD6026 Practice for Using Significant Digits in GeotechnicalData2.2 American Petroleum Institute Standard:3RP-40 Recommended Practice for Core
10、 Analysis Procedure3. Terminology3.1 DefinitionsFor definitions of common technical termsin this standard, refer to Terminology D653.4. Summary of Test Method4.1 The permeability of a rock sample is measured byflowing dry air through the specimen and measuring theabsolute pressure, the flow rate, an
11、d absolute pressure differ-ential of the air. Three or more tests are performed on a sampleat different mean air pressure values. The permeability valuesare plotted as a function of the reciprocal mean absolutepressure; those points lying on a straight line are extrapolatedto a value corresponding t
12、o an infinite mean air pressure toobtain an equivalent permeability value for liquids.5. Significance and Use5.1 This test method is designed to measure the permeabil-ity to air of a small sample of rock. By extrapolation, this testmethod also determines an equivalent of the liquid permeabil-ity. Th
13、is parameter is used to calculate the flow through rock offluids subjected to a pressure differential.NOTE 1The quality of the result produced by this standard isdependent on the competence of the personnel performing it, and the1This test method is under the jurisdiction ofASTM Committee D18 on Soi
14、l andRock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics.Current edition approved Nov. 1, 2013. Published December 2013. Originallyapproved in 1985. Last previous edition approved in 2008 as D4525 08. DOI:10.1520/D4525-13E01.2For referenced ASTM standards, visit the ASTM w
15、ebsite, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American Petroleum Institute (API), 1220 L. St., NW,Washington, DC 20005-4070, http:/www.api.
16、org.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1suitability of the equipment and facilities used. Agencies that meet thecriteria of Practice D3740 are generally cons
17、idered capable of competentand objective testing. Users of this standard are cautioned that compliancewith Practice D3740 does not in itself assure reliable results. Reliableresults depend on many factors; Practice D3740 provides a means ofevaluating some of those factors.6. Apparatus6.1 Permeameter
18、The permeameter shall have a specimenholder; a pressure transducer or gauge, or manometers, formeasuring the air pressure differential across the ends of thespecimen; a means for measuring the flow rate of the air; anda means for providing dry air to the flow stream (see Fig. 1).6.1.1 Specimen Holde
19、rThe specimen holder shall have adiameter of at least ten times the diameter of the largest particleof the specimen. Where suitable, the preferred diameter is 2.54cm (1 in.). The entrance and exit flow ports shall be sufficientlylarge to prevent pressure loss at maximum flow rate.The lengthshall be
20、1.3 to 1.7 times the diameter.6.1.2 Preferred ApparatusIn the preferred form, the speci-men holder shall be an elastomer sleeve and have means forconfining the sleeve and compressing it against the specimenso as to prevent bypassing of air under pressure between thesleeve and the specimen. The holde
21、r shall also have a meansfor confining the ends of the sample. In the preferred form, theend confining plugs will have two ports each, one for the flowof air, and the other for a static pressure line to measurepressure at the end faces of the specimen, as in Fig. 2. This typeof holder is suitable fo
22、r many types of flowing fluids andallows the simulation of overburden stress on the specimen.6.1.3 Alternative ApparatusAn elastomer bushing may beused to confine the specimen, as in Fig. 3. This holder issuitable for confining well-indurated specimens of a fine tomoderate texture. This holder allow
23、s rapid operation; it cannotbe used for simulating overburden stress.6.1.3.1 Alternatively, a rigid bushing may be cast around thespecimen (see Fig. 4). The casting material shall be one thatwill adhere well to both the specimen and the bushing, withoutpenetration of the specimen beyond the superfic
24、ial pores.Epoxies, polyesters, and sealing wax are suitable for thispurpose. This method of mounting samples is particularly wellsuited for testing less well-indurated specimens. This techniqueis not applicable for tests requiring the simulation of overbur-den stress.6.1.4 The flow rate of the air s
25、hall be sensed downstreamfrom the specimen by means of calibrated orifices (Fig. 1),rotameters (Fig. 5), or a bubble meter (Fig. 6).6.1.5 The preferred method of sensing absolute pressure toobtain the pressure differential across the specimen is by meansof absolute pressure transducers located at th
26、e ends of thespecimen. The transducers must operate over a range of 0 to 50kPa (0 to 7.3 psi) with a resolution of 250 Pa (0.036 psi) orbetter. Alternatively, the sensors may be connected to the endFIG. 1 Air Permeameter (Reproduced from RP-40)FIG. 2 Hassler Type Specimen HolderFIG. 3 Fancher-Type S
27、pecimen HolderFIG. 4 Compression Cell for Ring-Mounted SpecimensD4525 1312faces of the specimen with static lines, or placed in sufficientlylarge flow lines to cause less than 250 Pa (0.036 psi) loss ofhead at maximum flow rate. Pressure must be sensed betweenthe downstream end of the specimen and t
28、he orifice if such aflow sensor is utilized.6.1.5.1 Manometers may be utilized to measure the pres-sures of the flowing air. Both mercury and water manometersmust be provided with a high-pressure cutoff valve to the watermanometer as in Fig. 1, to provide the range of differentialpressures required.
29、 The manometers must be 20 cm (7.9 in.) ormore in height.6.1.5.2 Alternatively, absolute pressure gages with a rangeof 0 to 50 kPa (0 to 7.3 psi) and a resolution of 250 Pa (0.036psi) may be used to measure the pressure of the flowing air.6.1.6 The dimensions of the column for drying the flowingair
30、shall be a 2.54 cm (1 in.) inside diameter by a 30 cm (11.8in.) or more length. The columns shall be filled with silica gelor anhydrous calcium sulfate, with indicator. There shall be ascreen of 50 mesh on the downstream end of the filter toprevent particulate matter from reaching the specimen under
31、test.6.1.7 Compressed Air SourceA source with a regulatorand gauge that shall supply air pressure up to 50 kPa (7.3 psi)for the flow system.6.1.7.1 The air shall be clean and free of particles that canplug the pores of the sample.6.1.7.2 A compressed air supply with a separate regulatorand gauge, or
32、 a hydraulic pressure source with gauge, shallsupply pressure for seating the sleeve when that option forholding the specimen is used. A seating pressure of 700 kPa(101.5 psi) or more shall be used for seating. Pressures up to100 MPa (14503.8 psi) may be required for simulating in situstress.6.1.8 S
33、mall Vacuum SourceUsed for expanding thesleeve-type holder is required for specimen insertion when thatholder option is utilized.6.2 Drilling MachineA machine with a diamond bit andcoolant circulating system to drill specimens from rocksamples.6.3 Required Miscellaneous ImplementsItems including ast
34、op watch for use with bubble meter, a metric scale graduatedin millimetres for manometers, and a thermometer with divi-sions of 0.5C (1F) or better for measuring room temperature.6.4 Specimen Size Measurement DevicesDevices used tomeasure the length and diameter of the specimen shall becapable of me
35、asuring the desired dimension to within 0.1 % ofits actual length.7. Hazards7.1 WarningMercury has been designated by many regu-latory agencies as a hazardous material that can cause seriousmedical issues. Mercury, or its vapor, may be hazardous tohealth and corrosive to materials. Caution should be
36、 takenwhen handling mercury containing products. See the appli-cable product Safety Data Sheet (SDS) for additional informa-tion. Users should be aware that selling mercury or mercurycontaining products into your state or country may be prohib-ited by law.8. Sampling8.1 An adequate supply of homogen
37、eous material is neces-sary. A selection of samples shall be made using visualexamination of the site of evaluation to provide a representa-tive array of permeability values. Attention should be given tothe in situ orientation of the sample when visual inspectionindicates anisotropy is present. Dip
38、and strike of beddingplanes, if any, should be noted.9. Test Specimens9.1 Drill cylindrical specimens from the rock samples inorientations dictated by the in situ conditions and test goals, forexample, parallel and perpendicular to the bedding planes.Drill the samples to a length between 1.3 and 1.7
39、 times thediameter of the specimen.9.2 The ends of the specimen shall be faced with a diamondsaw to be approximately perpendicular to the axis of thespecimen. Wash the end faces with clear water.9.3 Drying Specimens:FIG. 5 Shielded MicroflowmeterFIG. 6 Bubble MeterD4525 13139.3.1 If the specimen is
40、free of swelling clay, dry in aconventional oven at a temperature of approximately 100Cuntil an equilibrium weight is obtained. Before weighing, coolspecimens to room temperature in a desiccator. Drying timevaries with specimen size and permeability;4hisgenerallysufficient for a permeable specimen o
41、f 2.54 cm (1 in.) indiameter.9.3.2 If the specimen contains swelling clays, dry in acontrolled humidity oven at 45?% relative humidity at 63Cuntil weight equilibrium is obtained. Drying time under theseconditions is usually two to four days.9.4 If necessary, clean engrained fines from the end faces
42、ofthe specimen by mild wire brushing and air jetting.10. Procedure10.1 Measure and record the length and diameter of thespecimen to the nearest 0.1 mm (0.004 in.). Take a minimum ofthree length measurements 120 apart and at least threediameter measurements one at the each end and one at themid-point
43、 of the height. Determine the average length anddiameter of the specimen.10.2 Place the specimen in the specimen holder and add endpieces to the holder as necessary. Turn the wheel of thecompression apparatus of the bushing-type holder, or increasethe annulus pressure of the sleeve-type holder, unti
44、l a sealagainst the periphery of the specimen is obtained.Apressure of700 kPa (101.5 psi) is usually found sufficient for sealing thesleeve-type holder.Apply additional pressure to the core holderif the simulation of in situ stress is required.10.3 Open the entrance flow valve, allowing air to flow
45、tothe specimen. Adjust the entrance pressure upward until asuitable flow of air occurs, but do not exceed the criticalvelocity beyond which turbulent flow occurs or inertial effectsbecome significant. Flow rates less than 2 cm3/s per 1 cm2ofspecimen end face area usually are found to be satisfactory
46、.Observe the flow rate until an equilibrium value is attained.Measure and record the flow rate and pressure differentialacross the specimen.10.4 Lower the flowing pressure used in 10.3 to abouttwo-thirds of the value and repeat the test and record.10.5 Lower the flowing pressure used in 10.4 to abou
47、tone-half of the value and repeat the test and record.10.6 Make preliminary calculations of the flow rate dividedby pressure differential of each step: 10.3 10.5. If the valuesare linearly related, proceed to Section 11. If the values are notlinearly related, reduce the flowing pressure in 10.5, rep
48、eat thetest, and record.10.7 Repeat the procedures of 10.3 10.6 until a linear setof data is obtained.11. Calculation11.1 Calculate the coefficient of permeability, k, at eachmean pressure, as follows:k 5 2QePeL!/Pi22 Pe2!A# (1)where:k = coefficient of permeability, m2Qe= exit flow rate of air, m3/s
49、Pe= exit absolute pressure of air, PaL = length of specimen, mA = cross-section area of specimen, m2Pi= entrance absolute pressure of air, Pa = viscosity of air at temperature of test, Pas11.2 Compute the mean pressure of each test for eachspecimen in Pa (psi) to the nearest 1 Pa, and then calculate thereciprocal of each mean pressure, as follows:2/Pi1Pe! (2)11.3 Plot the coefficient of permeability versus the recipro-cal of the mean pressure for each test of a specimen, see Fig.7. Draw a straight line through at least three points (this will
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