1、Designation: D 4631 95 (Reapproved 2000)Standard Test Method forDetermining Transmissivity and Storativity of LowPermeability Rocks by In Situ Measurements UsingPressure Pulse Technique1This standard is issued under the fixed designation D 4631; the number immediately following the designation indic
2、ates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a field procedure
3、for determin-ing the transmissivity and storativity of geological formationshaving permeabilities lower than 103m2(1 millidarcy) usingthe pressure pulse technique.1.2 The transmissivity and storativity values determined bythis test method provide a good approximation of the capacityof the zone of in
4、terest to transmit water, if the test intervals arerepresentative of the entire zone and the surrounding rock isfully water saturated.1.3 The values stated in SI units are to be regarded as thestandard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with i
5、ts 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. Terminology2.1 Definitions of Terms Specific to This Standard:2.1.1 transmissivity, Tthe transmissivity of a f
6、ormation ofthickness, b, is defined as follows:T 5 Kb (1)where:K = equivalent formation hydraulic conductivity (efhc).The efhc is the hydraulic conductivity of a material if it werehomogeneous and porous over the entire interval. The hydrau-lic conductivity, K, is related to the equivalent formation
7、, k,asfollows:K 5 krg/ (2)where:r = fluid density, = fluid viscosity, andg = acceleration due to gravity.2.1.2 storativity, Sthe storativity (or storage coefficient) ofa formation of thickness, b, is defined as follows:S 5 Ssb (3)where:Ss= equivalent bulk rock specific storage (ebrss).The ebrss is d
8、efined as the specific storage of a material if itwere homogeneous and porous over the entire interval. Thespecific storage is given as follows:Ss5rgCb1 nCw! (4)where:Cb= bulk rock compressibility,Cw= fluid compressibility, andn = formation porosity.2.2 Symbols:2.2.1 Cbbulk rock compressibility M1LT
9、2.2.2.2 Cwcompressibility of water M1LT2.2.2.3 Khydraulic conductivity LT1.2.2.3.1 DiscussionThe use of the symbol K for the termhydraulic conductivity is the predominant usage in ground-water literature by hydrogeolists, whereas the symbol k iscommonly used for this term in rock mechanics and soils
10、cience.2.2.4 Llength of packed-off zone L.2.2.5 Pexcess test hole pressure ML1T2.2.2.6 Poinitial pressure pulse ML1T2.2.2.7 Sstorativity (or storage coefficient) (dimensionless).2.2.8 Ssspecific storage L1.2.2.9 Ttransmissivity L2T1.2.2.10 Vwvolume of water pulsed L3.2.2.11 bformation thickness L.2.
11、2.12 efracture aperture L.2.2.13 gacceleration due to gravity LT2.2.2.14 kpermeability L2.2.2.15 nporosity (dimensionless).2.2.16 rwradius of test hole L.2.2.17 ttime elapsed from pulse initiation T.1This test method is under the jurisdiction of ASTM Committee D18 on Soil andRock and is the direct r
12、esponsibility of Subcommittee D18.21 on Ground Water andVadose Zone Investigations.Current edition approved Oct. 10, 1995. Published March 1996. Originallypublished as D 4631 86. Discontinued April 1995 and reinstated as D 4631 95.1Copyright ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2
13、959, United States.2.2.18 adimensionless parameter.2.2.19 bdimensionless parameter.2.2.20 viscosity of water ML1T1.2.2.21 rdensity of water ML3.3. Summary of Test Method3.1 A borehole is first drilled into the rock mass, intersectingthe geological formations for which the transmissivity andstorativi
14、ty are desired. The borehole is cored through potentialzones of interest, and is later subjected to geophysical boreholelogging over these intervals. During the test, each interval ofinterest is packed off at top and bottom with inflatable rubberpackers attached to high-pressure steel tubing. After
15、inflatingthe packers, the tubing string is completely filled with water.3.2 The test itself involves applying a pressure pulse to thewater in the packed-off interval and tubing string, and record-ing the resulting pressure transient. A pressure transducer,located either in the packed-off zone or in
16、the tubing at thesurface, measures the transient as a function of time. The decaycharacteristics of the pressure pulse are dependent on thetransmissivity and storativity of the rock surrounding theinterval being pulsed and on the volume of water being pulsed.Alternatively, under non-artesian conditi
17、ons, the pulse test maybe performed by releasing the pressure on a shut-in well,thereby subjecting the well to a negative pressure pulse.Interpretation of this test method is similar to that described forthe positive pressure pulse.4. Significance and Use4.1 Test MethodThe pulse test method is used
18、to deter-mine the transmissivity and storativity of low-permeabilityformations surrounding the packed-off intervals. This testmethod is considerably shorter in duration than the pump andslug tests used in more permeable rocks. To obtain results tothe desired accuracy, pump and slug tests in low-perm
19、eabilityformations are too time consuming, as indicated in Fig. 1 (fromBredehoeft and Papadopulos (1).24.2 AnalysisThe transient pressure data obtained usingthe suggested method are evaluated by the curve-matchingtechnique described by Bredehoeft and Papadopulos (1),orbyan analytical technique propo
20、sed by Wang et al (2). The latteris particularly useful for interpreting pulse tests when only theearly-time transient pressure decay data are available.4.3 Units:4.3.1 ConversionsThe permeability of a formation isoften expressed in terms of the unit darcy. A porous mediumhas a permeability of 1 dar
21、cy when a fluid of viscosity 1 cP (1mPas) flows through it at a rate of 1 cm3/s (106m3/s)/1 cm2(104m2) cross-sectional area at a pressure differential of 1 atm(101.4 kPa)/1 cm (10 mm) of length. One darcy corresponds to0.987 m2. For water as the flowing fluid at 20C, a hydraulicconductivity of 9.66
22、m/s corresponds to a permeability of 1darcy.4.3.2 Viscosity of WaterTable 1 shows the viscosity ofwater as a function of temperature.5. ApparatusNOTE 1A schematic of the test equipment is shown in Fig. 2.5.1 Source of Pressure PulseA pump or pressure intensi-fier shall be capable of injecting an add
23、itional amount of waterto the water-filled tubing string and packed-off test interval toproduce a sharp pressure pulse of up to 1 MPa (145 psi) inmagnitude, preferably with a rise time of less than 1 % of onehalf of the pressure decay (P/Po= 0.5).5.2 PackersHydraulically actuated packers are recom-m
24、ended because they produce a positive seal on the boreholewall and because of the low compressibility of water they arealso comparatively rigid. Each packer shall seal a portion of theborehole wall at least 0.5 m in length, with an applied pressureat least equal to the excess maximum pulse pressure
25、to beapplied to the packed-off interval and less than the formationfracture pressure at that depth.5.3 Pressure TransducersThe test pressure may be mea-sured directly in the packed-off test interval or between thefast-acting valve and the test interval with an electronicpressure transducer. In eithe
26、r case the pressure shall berecorded at the surface as a function of time. The pressuretransducer shall have an accuracy of at least 63 kPa (60.42The boldface numbers in parentheses refer to the list of references at the end ofthe text.FIG. 1 Comparative Times for Pressure Pulse and Slug TestsD 4631
27、2psi), including errors introduced by the recording system, anda resolution of at least 1 kPa (0.15 psi).5.4 Hydraulic SystemsThe inflatable rubber packers shallbe attached to high-pressure steel tubing reaching to thesurface. The packers themselves shall be inflated with waterusing a separate hydra
28、ulic system. The pump or pressureintensifier providing the pressure pulse shall be attached to thesteel tubing at the surface. If the pump is used, a fast-operatingvalve shall be located above, but as near as practical to theupper packer. That valve should be located less than 10 mabove the anticipa
29、ted equilibrium head in the interval beingtested to avoid conditions in the tubing changing during the testfrom a full water column to a falling water-level columnbecause of formation of a free surface at or near zero absolutepressure (Neuzil (3).6. Procedure6.1 Drilling Test Holes:6.1.1 Number and
30、OrientationThe number of test holesshall be sufficient to supply the detail required by the scope ofthe project. The test holes shall be directed to intersect majorfracture sets, preferable at right angles.6.1.2 Test Hole QualityThe drilling procedure shall pro-vide a borehole sufficiently smooth fo
31、r packer seating, shallcontain no rapid changes in direction, and shall minimizeformation damage.6.1.3 Test Holes CoredCore the test holes through zonesof potential interest to provide information for locating testintervals.6.1.4 Core DescriptionDescribe the rock core from thetest holes with particu
32、lar emphasis on the lithology and naturaldiscontinuities.6.1.5 Geophysical Borehole LoggingLog geophysicallythe zones of potential interest. In particular, run electrical-induction and gamma-gamma density logs. Run other logs asrequired.6.1.6 Washing Test HolesThe test holes must not containany mate
33、rial that could be washed into the permeable zonesduring testing, thereby changing the transmissivity and storat-ivity. Flush the test holes with clean water until the return isfree from cuttings and other dispersed solids.6.2 Test Intervals:6.2.1 Selection of Test IntervalsTest intervals are deter-
34、mined from the core descriptions, geophysical borehole logs,and, if necessary, from visual inspection of the borehole with aborescope or television camera.6.2.2 Changes in LithologyTest each major change inlithology that can be isolated between packers.6.2.3 Sampling DiscontinuitiesDiscontinuities a
35、re oftenthe major permeable features in hard rock. Test jointed zones,fault zones, bedding planes, and the like, both by isolatingindividual features and by evaluating the combined effects ofseveral features.6.2.4 Redundancy of TestsTo evaluate variability in trans-missivity and storativity, conduct
36、 several tests in each rocktype, if homogeneous. If the rock is not homogeneous, each setof tests should encompass similar types of discontinuities.6.3 Test Water:6.3.1 QualityWater used for pressure pulse tests shall beclean and compatible with the formation. Even small amountsof dispersed solids i
37、n the injection water could plug the rockface of the test interval and result in a measured transmissivityvalue that is erroneously low.6.3.2 TemperatureThe lower limit of the test water tem-perature shall be 5C below that of the rock mass to be tested.Cold water injected into a warm rock mass cause
38、s air to comeout of solution, and the resulting bubbles will radically modifythe pressure transient characteristics.6.4 Testing:6.4.1 Filling and Purging SystemAllow sufficient timeafter washing the test hole for any induced formation pressuresto dissipate. Once the packers have been set, slowly fil
39、l theTABLE 1 Viscosity of Water as a Function of TemperatureTemperature, C Absolute Viscosity, mPas0 1.792 1.674 1.576 1.478 1.3910 1.3112 1.2414 1.1716 1.1118 1.0620 1.0022 0.9624 0.9126 0.8728 0.8430 0.8032 0.7734 0.7436 0.7138 0.6840 0.66FIG. 2 Schematic of Test EquipmentD 46313tubing string and
40、packed-off interval with water to ensure thatno air bubbles will be trapped in the test interval and tubing.6.4.2 Pressure Pulse TestThis range of pressures is inmost cases sufficiently low to minimize distortion of fracturesadjacent to the test hole, but in no case should the pressureexceed the min
41、imum principal ground stress. Record theresulting pressure pulse and decay transient detected by thepressure transducer as a function of time. A typical record isshown in Fig. 3.6.4.2.1 Before the pressure pulse test can be started it isnecessary to reliably estimate the natural pressure in the test
42、interval. See 7.1.1 and Fig. 3 for a description of a method toprepare the system for the pulse test. After the pressure is at, orestimated to be approaching at a predictable rate, near-equilibrium conditions, then rapidly pressurize the tubing,typically to between 300 and 600 kPa (50 to 100 psi), a
43、nd thenshut in.7. Calculation and Interpretation of Test Data7.1 The type of matching technique developed by Brede-hoeft and Papadopulos (1) involves plotting normalized pres-sure (the ratio of the excess borehole pressure, P, at a giventime to the initial pressure pulse, Po) against the logarithm o
44、ftime, as indicated in Fig. 1 and Fig. 3. The pulse decay is givenas follows:PPo5 Fa,b! (5)where:a and b = dimensionless parameters given by:to:a5pr2wS/VwCwrg (6)and:b5pTt/VwCwrg (7)where:Vw= volume of water being pulsed,rw= well radius,t = time elapsed from pulse initiation,Cw= compressibility of w
45、ater,T = transmissivity,S = storage coefficient,r = density of water, andg = gravitational acceleration.Tables of the function F (ab) have been provided byCooper, et al (4), Papadopulos (5), and Bredehoeft and Papa-dopulos (1).7.1.1 In Fig. 3 the pressure, p, shown before (to the left of)Time t1repr
46、esents the unknown natural pressure in the intervaleventually to be tested. The drill hole encounters that intervalat Time t1and from then until Time t2the pressure variationreflects the effects of drilling and test hole development. If theinterval consists of rocks or sediments of low hydrauliccond
47、uctivity, there might be a long time period before thewater level in an open hole would stabilize to the equilibriumlevel. For that reason before a pulse test can be conducted wewant to establish a condition that provides a reasonableestimate of the undisturbed pressure for the interval. Thefollowin
48、g procedure is intended to provide that condition. AtTime t2the packers are inflated, and then the system is filledwith water and shut in. By this operation the change in pressurein the packed-off interval will reflect a compressive system andshould approach the pressure in the interval being tested
49、 muchmore rapidly than would the water level in an open test hole.Monitoring the pressure changes should indicate when near-equilibrium conditions are approached. At Time t3the value isopened, the system is subjected to the Pulse Po, and the valveis closed. Monitoring the heads after Time t3gives the dataneeded to use the calculation procedure of Bredehoeft andPapadopulos.7.1.1.1 Neuzil (3) points out the necessity of measuring theamount of water used to create the
