1、Designation: D 4525 08Standard Test Method forPermeability of Rocks by Flowing Air1This standard is issued under the fixed designation D 4525; 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 p
2、arentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers the determination of the coef-ficient of specific permeability for the flow of air throughrocks. The procedure establishe
3、s representative values of thecoefficient of permeability of rocks or well-indurated soils.1.2 This test method is limited to permeability valuesgreater than 0.9869 pm2(1.0 picodarcy), and is limited to rocksfree of oil or unctuous matter.1.3 The values stated in SI units are to be regarded as thest
4、andard. The values given in parentheses are mathematicalconversions to inch-pound units that are provided for informa-tion only and are not considered standard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the use
5、r 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:2D 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 3740 Practice for Minimum Requirements for Agenci
6、esEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and Construction2.2 American Petroleum Institute Standard:3RP-40 Recommended Practice for Core Analysis Procedure3. Terminology3.1 For terminology used in this test method, refer toTerminology D 653.4. Summary of Te
7、st Method4.1 The permeability of a rock sample is measured byflowing dry air through the specimen and measuring theabsolute pressure, the flow rate, and absolute pressure differ-ential of the air. Three or more tests are performed on a sampleat different mean air pressure values. The permeability va
8、luesare plotted as a function of the reciprocal mean absolutepressure; those points lying on a straight line are extrapolatedto a value corresponding to an infinite mean air pressure toobtain an equivalent permeability value for liquids.5. Significance and Use5.1 This test method is designed to meas
9、ure the permeabil-ity to air of a small sample of rock. By extrapolation, this testmethod also determines an equivalent of the liquid permeabil-ity. This parameter is used to calculate the flow through rock offluids subjected to a pressure differential.NOTE 1Notwithstanding the statements on precisi
10、on and bias con-tained in this test method, the measures of precision of this test method isdependent on the competence of the personnel performing them, and onthe suitability of the equipment and facilities used. Agencies that meet thecriteria of Practice D 3740 are generally considered capable of
11、competentand objective testing. Users of this test method are cautioned thatcompliance with Practice D 3740 does not in itself assure reliable testing.Reliable testing depends on many factors; Practice D 3740 provides ameans for evaluating some of those factors.6. Apparatus6.1 PermeameterThe permeam
12、eter 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 HolderThe specim
13、en holder shall have adiameter of at least ten times the diameter of the largest particle1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics.Current edition approved July 1, 2008. Published July 20
14、08. Originally approvedin 1985. Last previous edition approved in 2004 as D 4525 04.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary p
15、age onthe ASTM website.3Available from American Petroleum Institute (API), 1220 L. St., NW, Wash-ington, DC 20005-4070, http:/www.api.org.FIG. 1 Air Permeameter (Reproduced from RP-40)1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Dri
16、ve, PO Box C700, West Conshohocken, PA 19428-2959, United States.of the specimen. Where suitable, the preferred diameter is 2.54cm. The entrance and exit flow ports shall be sufficiently largeto prevent pressure loss at maximum flow rate. The length shallbe 1.3 to 1.7 times the diameter.6.1.2 Prefer
17、red ApparatusIn the preferred form, thespecimen holder shall be an elastomer sleeve and have meansfor confining the sleeve and compressing it against the speci-men so as to prevent bypassing of air under pressure betweenthe sleeve and the specimen. The holder shall also have ameans for confining the
18、 ends of the sample. In the preferredform, the end confining plugs will have two ports each, one forthe flow of air, and the other for a static pressure line tomeasure pressure at the end faces of the specimen, as in Fig. 2.This type of holder is suitable for many types of flowing fluidsand allows t
19、he simulation of overburden stress on the speci-men.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 allows rapid operation; it cannotbe used for s
20、imulating 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 superficial pores.Epoxies, polyesters, and sealin
21、g 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 shall be sensed downstreamfrom the specime
22、n 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 the ends of thespecimen. The transducers mu
23、st operate over a range of 0 to 50kPa (0 to 0.5 atmospheres) with a resolution of 250 Pa (0.0025atmospheres) or better. Alternatively, the sensors may beconnected to the end faces of the specimen with static lines, orplaced in sufficiently large flow lines to cause less than 250 Pa(0.0025 atmosphere
24、s) loss of head at maximum flow rate.Pressure must be sensed between the downstream end of thespecimen and the orifice if such a flow sensor is utilized.6.1.5.1 Manometers may be utilized to measure the pres-sures of the flowing air. Both a mercury and water manometermust be provided, with a high-pr
25、essure cutoff valve to thewater manometer as in Fig. 1, to provide the range ofdifferential pressures required. The manometers must be 20 cmor more in height.6.1.5.2 Alternatively, absolute pressure gages with a rangeof 0 to 50 kPa (0 to 0.5 atmospheres) and a resolution of 250Pa (0.0025 atmospheres
26、) may be used to measure the pressureof the flowing air.6.1.6 The dimensions of the column for drying the flowingair shall be a 2.54-cm inside diameter by a 30-cm or morelength. The columns shall be filled with silica gel or anhydrouscalcium sulfate, with indicator. There shall be a screen of 50mesh
27、 on the downstream end of the filter to prevent particulatematter from reaching the specimen under test.6.1.7 Compressed Air Source, with a regulator and gauge,shall supply air pressure up to 50 kPa (12 atmosphere) for theflow system.6.1.7.1 The air shall be clean and free of particles that canplug
28、the pores of the sample.FIG. 2 Hassler Type Specimen HolderFIG. 3 Fancher-Type Specimen HolderFIG. 4 Compression Cell for Ring-Mounted SpecimensD45250826.1.7.2 A compressed air supply with a separate regulatorand gauge, or a hydraulic pressure source with gauge, shallsupply pressure for seating the
29、sleeve when that option forholding the specimen is used. A seating pressure of 700 kPa (7atmospheres) or more shall be used for seating. Pressures up to100 MPa (1000 atmospheres) may be required for simulating insitu stress.6.1.8 Small Vacuum Source, for expanding the sleeve-typeholder is required f
30、or specimen insertion when that holderoption is utilized.6.2 Drilling Machine, with a diamond bit and coolantcirculating system to drill specimens from rock samples.6.3 Required Miscellaneous Implements, including a stopwatch for use with bubble meter, a metric scale graduated inmillimetres for mano
31、meters, a caliper for measuring the lengthand diameter of the specimens in centimetres, 60.05 cm, anda thermometer for measuring room temperature.7. Sampling7.1 An adequate supply of homogeneous material is neces-sary. A selection of samples shall be made using visualexamination of the site of evalu
32、ation 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 and strike of beddingplanes, if any, should be noted.8. Test Specimens8.1 Drill cylindrical specimens from the
33、 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 times thediameter of the specimen.8.2 The ends of the specimen shall be faced with a diamondsaw to be approxi
34、mately perpendicular to the axis of thespecimen. Wash the end faces with clear water.8.3 Drying Specimens:8.3.1 If the specimen is free of swelling clay, dry in aconventional oven at a temperature of approximately 100Cuntil an equilibrium weight is obtained. Before weighing, coolspecimens to room te
35、mperature in a desiccator. Drying timevaries with specimen size and permeability;4hisgenerallysufficient for a permeable specimen of 2.54 cm in diameter.8.3.2 If the specimen contains swelling clays, dry in acontrolled humidity oven at 45 % relative humidity at 63Cuntil weight equilibrium is obtaine
36、d. Drying time under theseconditions is usually two to four days.8.4 If necessary, clean engrained fines from the end faces ofthe specimen by mild wire brushing and air jetting.9. Procedure9.1 Measure and record the length and diameter of thespecimen to 60.1 cm. If the diameter is not uniform, measu
37、reat several positions, determine the mean diameter, and record.9.2 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, until a sealag
38、ainst the periphery of the specimen is obtained.Apressure of700 kPa (7 atmospheres) is usually found sufficient for sealingthe sleeve-type holder. Apply additional pressure to the coreholder if the simulation of in situ stress is required.9.3 Open the entrance flow valve, allowing air to flow to the
39、specimen. Adjust the entrance pressure upward until a suitableflow of air occurs, but do not exceed the critical velocitybeyond which turbulent flow occurs or inertial effects becomesignificant. Flow rates less than 2 cm3/s per 1 cm2of specimenend face area usually are found to be satisfactory. Obse
40、rve theflow rate until an equilibrium value is attained. Measure andrecord the flow rate and pressure differential across thespecimen.9.4 Lower the flowing pressure used in 9.3 to about two-thirds of the value and repeat the test of 9.3 and record.9.5 Lower the flowing pressure used in 9.4 to about
41、one-halfof the value and repeat the test and record.9.6 Make preliminary calculations of the flow rate dividedby pressure differential of each step: 9.3-9.5. If the values arelinearly related, proceed to Section 10. If the values are notlinearly related, reduce the flowing pressure of 9.5, and repea
42、tthe test.9.7 Repeat the procedures of 9.3-9.6 until a linear set of datais obtained.FIG. 5 Shielded MicroflowmeterFIG. 6 Bubble MeterD452508310. Calculation10.1 Calculate the coefficient of permeability, k, at eachmean pressure, as follows:k 5 2QePeL!/Pi22 Pe2!A (1)where:k = coefficient of permeabi
43、lity, m2(=1012Darcy),Qe= exit flow rate of air, m3/s,Pe= exit absolute pressure of air, Pa,L = length of specimen, m,A = cross-section area of specimen, m2,Pi= entrance absolute pressure of air, Pa, and = viscosity of air at temperature of test, Pas.10.2 Compute the mean pressure of each test for ea
44、chspecimen in Pa (atmospheres), and then calculate the reciprocalof each mean pressure, as follows:2/Pi1 Pe! (2)10.3 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
45、beat the lower values of reciprocal mean pressure) and extrapo-late the line to intersect the ordinate line at zero reciprocalmean pressure. The value of k at the intersection is theequivalent liquid permeability of the specimen. If a straightline cannot be established through the data points, anoth
46、er testat a lower mean pressure may be required, or the complete testshould be repeated.11. Report11.1 Report the following items for the particular test beingperformed:11.1.1 Source of test specimen, including project name andlocation, as well as other pertinent data that help identify thespecimen,
47、11.1.2 Date test is performed,11.1.3 Physical description of the test specimen, including:rock type, such as sandstone, limestone, granite, etc.; locationand orientation of inherent rock structural features; and anydiscontinuities and large inclusions or inhomogeneities, if any,11.1.4 Length and dia
48、meter of the specimen (9.1), as well asflowing pressure during the test (9.3-9.7), and11.1.5 The measured permeability (10.1), the mean pres-sures (10.2), and a permeability plot (10.3).12. Precision and Bias12.1 PrecisionDue to the nature of rock materials testedby this test method, it is, at this
49、time, either not feasible or toocostly to produce multiple specimens that have uniform physi-cal properties. Therefore, since specimens that would yield thesame test results cannot be tested, Subcommittee D18.12cannot determine the variation between tests since any varia-tion observed is just as likely to be due to specimen variationas to operator or laboratory testing variation. SubcommitteeD18.12 welcomes proposals to resolve this problem that wouldallow for development of a valid precision statement.12.2 BiasThere is no accepted reference value for this testmet
