1、Designation: D4525 13Standard 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 par
2、entheses 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 method establishes rep
3、resentative values of thecoefficient of permeability of rocks or well-indurated soils.1.2 This test method is limited to permeability valuesgreater than 9.869 10-18 m2(0.01 millidarcy), and is limitedto rocks free of oil or unctuous matter.1.3 The values stated in SI units are to be regarded as thes
4、tandard. 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 All observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D6026.1.4.
5、1 The procedures used to specify how data are collected/recorded or calculated, in this standard are regarded as theindustry standard. In addition, they are representative of thesignificant digits that generally should be retained. The proce-dures used do not consider material variation, purpose for
6、obtaining the data, special purpose studies, or any consider-ations for the users objectives; and it is common practice toincrease 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
7、analyticalmethods for engineering design.1.5 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
8、 limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D653 Terminology Relating to Soil, Rock, and ContainedFluidsD3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD6026 Practice for U
9、sing Significant Digits in GeotechnicalData2.2 American Petroleum Institute Standard:3RP-40 Recommended Practice for Core Analysis Procedure3. Terminology3.1 DefinitionsFor definitions of common technical termsin this standard, refer to Terminology D653.4. Summary of Test Method4.1 The permeability
10、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 valuesare plotted as a function
11、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 measure the permeabil-ity to air o
12、f 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 1The quality of the result produced by this standard isdependent on the
13、competence of the personnel performing it, and thesuitability of the equipment and facilities used. Agencies that meet thecriteria of Practice D3740 are generally considered capable of competentand objective testing. Users of this standard are cautioned that compliancewith Practice D3740 does not in
14、 itself assure reliable results. Reliableresults depends on many factors; Practice D3740 provides a means ofevaluating some of those factors.1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics.Curr
15、ent edition approved Nov. 1, 2013. Published December 2013. Originallyapproved in 1985. Last previous edition approved in 2008 as D4525 08. DOI:10.1520/D4525-13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book o
16、f 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.org.*A Summary of Changes section appears at the end of this standardCopyright ASTM Interna
17、tional, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States16. Apparatus6.1 PermeameterThe 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 me
18、asuring 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 2.54cm (1 in.). The en
19、trance and exit flow ports shall be sufficientlylarge to prevent pressure loss at maximum flow rate.The lengthshall be 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 compressin
20、g it against the specimenso as to prevent bypassing of air under pressure between thesleeve and the specimen. The holder 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 st
21、atic pressure line to measurepressure at the end faces of the specimen, as in Fig. 2. This typeof holder is suitable for 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 i
22、n Fig. 3. This holder issuitable for 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 b
23、e one thatwill adhere well to both 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. Th
24、is 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 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 pr
25、essure toobtain the pressure differential 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 7.3 psi) with a resolution of 250 Pa (36.3 psi) orbetter. Alternatively, the sensors may be conn
26、ected to the endfaces of the specimen with static lines, or placed in sufficientlylarge flow lines to cause less than 250 Pa (36.3 psi) loss of headat maximum flow rate. Pressure must be sensed between thedownstream end of the specimen and the orifice if such a flowsensor is utilized.FIG. 1 Air Perm
27、eameter (Reproduced from RP-40)FIG. 2 Hassler Type Specimen HolderFIG. 3 Fancher-Type Specimen HolderFIG. 4 Compression Cell for Ring-Mounted SpecimensD4525 1326.1.5.1 Manometers may be utilized to measure the pres-sures of the flowing air. Both mercury and water manometersmust be provided with a hi
28、gh-pressure cutoff valve to the watermanometer as in Fig. 1, to provide the range of differentialpressures required. 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 (36.3psi) m
29、ay be used to measure the pressure of the flowing air.6.1.6 The dimensions of the column for drying the flowingair 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 a
30、screen of 50 mesh on the downstream end of the filter toprevent particulate matter from reaching the specimen undertest.6.1.7 Compressed Air Source, with a regulator and gauge,shall supply air pressure up to 50 kPa (7.3 psi) for the flowsystem.6.1.7.1 The air shall be clean and free of particles tha
31、t canplug the pores of the sample.6.1.7.2 A compressed air supply with a separate regulatorand gauge, or 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 use
32、d for seating. Pressures up to100 MPa (14503.8 psi) may be required for simulating in situstress.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
33、 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 manometers, and a thermometer with divisionsof 0.5C (1F) or better for measuring room temperature.6.4 Specimen Size Measurement Dev
34、icesDevices used tomeasure the length and diameter of the specimen shall becapable of measuring 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. Mercur
35、y, or its vapor, may be hazardous tohealth and corrosive to materials. Caution should be 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
36、 state or country may be prohib-ited by law.8. Sampling8.1 An adequate supply of homogeneous 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 si
37、tu orientation of the sample when visual inspectionindicates anisotropy is present. Dip 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 a
38、nd perpendicular to the bedding planes.Drill the samples to a length between 1.3 and 1.7 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 Specim
39、ens:9.3.1 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 temperature in a desiccator. Drying timevaries with specimen size and permeability;4hisgenerallysufficie
40、nt for a permeable specimen of 2.54 cm in diameter.FIG. 5 Shielded MicroflowmeterFIG. 6 Bubble MeterD4525 1339.3.2 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 usua
41、lly two to four days.9.4 If necessary, clean engrained fines from the end faces 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
42、 at least threediameter measurements one at the each end and one at themid-point 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 bush
43、ing-type holder, or increasethe annulus pressure of the sleeve-type holder, until 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
44、situ stress is required.10.3 Open the entrance flow valve, allowing air to flow 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 tha
45、n 2 cm3/s per 1 cm2ofspecimen end face area usually are found to be satisfactory.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
46、 repeat the test of 10.3 and record.10.5 Lower the flowing pressure used in 10.4 to aboutone-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 Sec
47、tion 11. If the values are notlinearly related, reduce the flowing pressure of 10.5, and repeatthe test.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 Pe
48、2!A# (1)where:k = coefficient of permeability, m2,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.11.2 Compute the mean
49、 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 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
