1、Designation: D 4525 04Standard 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 (e) 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 establish
3、es 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 thes
4、tandard.1.4 This standard does not purport to address all of thesafety concerns, if any, 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. Refe
5、renced Documents2.1 ASTM Standards:2D 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 3740 Practice for Minimum Requirements for AgenciesEngaged in the Testing and/or Inspection of Soil and Rockas Used in Engineering Design and Construction2.2 American Petroleum Institute Standard:3RP-4
6、0 Recommended Practice for Core Analysis Procedure3. Terminology3.1 For terminology used in this test method, refer toTerminology D 653.4. 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,
7、 and 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 correspondin
8、g to 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.
9、 This parameter is used to calculate the flow through rock offluids subjected to a pressure differential.NOTE 1Notwithstanding the statements on precision and bias con-tained in this test method, the measures of precision of this test method isdependent on the competence of the personnel performing
10、them, and onthe suitability of the equipment and facilities used. Agencies that meet thecriteria of Practice D 3740 are generally considered capable of competentand objective testing. Users of this test method are cautioned thatcompliance with Practice D 3740 does not in itself assure reliable testi
11、ng.Reliable testing depends on many factors; Practice D 3740 provides ameans for evaluating some of those factors.6. Apparatus6.1 PermeameterThe permeameter shall have a specimenholder; a pressure transducer or gage, or manometers, formeasuring the air pressure differential across the ends of thespe
12、cimen; 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 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
13、.54cm. The entrance and exit flow ports shall be sufficiently large1This test method is under the jurisdiction of ASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics.Current edition approved July 1, 2004. Published July 2004. Originally approv
14、edin 1985. Last previous edition approved in 2001 as D 4525 90(2001).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 page onthe ASTM
15、website.3Available from American Petroleum Institute, 2101 L St., NW, Washington, DC20037.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 Drive, PO Box C700, West Conshohocken, PA 19428-295
16、9, United States.to prevent pressure loss at maximum flow rate. The length shallbe 1.3 to 1.7 times the diameter.6.1.2 Preferred 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 pr
17、event bypassing of air under pressure betweenthe sleeve and the specimen. The holder shall also have ameans for confining the 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 pressur
18、e at the end faces of the specimen, as in Fig. 2.This type of holder is suitable for many types of flowing fluidsand allows the 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 fo
19、r confining well-indurated specimens of a fine tomoderate texture. This holder allows 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
20、the specimen and the bushing, withoutpenetration of the specimen beyond the superficial 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 t
21、ests requiring the simulation of overbur-den stress.6.1.4 The flow rate of the air shall 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 differ
22、ential across the specimen is by meansof absolute pressure transducers located at the ends of thespecimen. The transducers must 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 f
23、aces of the specimen with static lines, orplaced in sufficiently large flow lines to cause less than 250 Pa(0.0025 atmospheres) 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
24、 be utilized to measure the pres-sures of the flowing air. Both a mercury and water manometermust be provided, with a high-pressure 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 Alternati
25、vely, absolute pressure gages with a rangeof 0 to 50 kPa (0 to 0.5 atmospheres) and a resolution of 250Pa (0.0025 atmospheres) 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 morelengt
26、h. The columns shall be filled with silica gel or anhydrouscalcium sulfate, with indicator. There shall be a screen of 50mesh 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 gage,shall supply air
27、 pressure up to12 atmosphere for the flowsystem.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 gage, or a hydraulic pressure source with gage, shallsupply pressure for seating the sleeve when that
28、 option forFIG. 2 Hassler Type Specimen HolderFIG. 3 Fancher-Type Specimen HolderFIG. 4 Compression Cell for Ring-Mounted SpecimensD4525042holding 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 re
29、quired for simulating insitu stress.6.1.8 Small Vacuum Source, for expanding the sleeve-typeholder is required for 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 Miscellane
30、ous Implements, including a stopwatch for use with bubble meter, a metric scale graduated inmillimetres for manometers, 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 homog
31、eneous 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. Di
32、p and strike of beddingplanes, if any, should be noted.8. Test Specimens8.1 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
33、.7 times thediameter of the specimen.8.2 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.8.3 Drying Specimens:8.3.1 If the specimen is free of swelling clay, dry in aconventional oven at a tem
34、perature 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 of 2.54 cm in diameter.8.3.2 If the specimen contains swel
35、ling 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.8.4 If necessary, clean engrained fines from the end faces ofthe specimen by mild wire brushing and air jetting.9. Procedur
36、e9.1 Measure and record the length and diameter of thespecimen to 60.1 cm. If the diameter is not uniform, measureat 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
37、 apparatus of the bushing-type holder, or increasethe annulus pressure of the sleeve-type holder, until a sealagainst the periphery of the specimen is obtained. A pressure of700 kPa (7 atmospheres) is usually found sufficient for sealingthe sleeve-type holder. Apply additional pressure to the coreho
38、lder if the simulation of in situ stress is required.9.3 Open the entrance flow valve, allowing air to flow to thespecimen. 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 becomesign
39、ificant. Flow rates less than 2 cm3/s per 1 cm2of specimenend face area usually are found to be satisfactory. Observe 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
40、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 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 re
41、lated, proceed to Section 10. If the values are notlinearly related, reduce the flowing pressure of 9.5, and repeatthe test.9.7 Repeat the procedures of 9.3-9.6 until a linear set of datais obtained.10. Calculation10.1 Calculate the coefficient of permeability, k, at eachmean pressure, as follows:FI
42、G. 5 Shielded MicroflowmeterFIG. 6 Bubble MeterD4525043k 5 2QePeL!/Pi22 Pe2!A (1)where:k = coefficient of permeability, 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
43、 of air, Pa, and = viscosity of air at temperature of test, Pas.10.2 Compute the mean pressure of each test for eachspecimen 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 me
44、an pressure for each test of a specimen, see Fig.7. Draw a straight line through at least three points (this will 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 theequi
45、valent liquid permeability of the specimen. If a straightline cannot be established through the data points, another 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
46、test specimen, including project name andlocation, as well as other pertinent data that help identify thespecimen,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
47、 structural features; and anydiscontinuities and large inclusions or inhomogeneities, if any,11.1.4 Length and diameter 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).
48、12. Precision and Bias12.1 PrecisionDue to the nature of rock materials testedby this test method, it is, at this 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 te
49、sted, 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 testmethod; therefore, bias cannot be determined.13. Keywords13.1 flow and flow rate; permeabilitySUMMARY OF CHANGESIn accordance with Committee D18 policy this section identifies the location of
