ASTM_D_4631_-_95_2008.pdf

Designation:D463195(Reapproved 2008)Standard Test Method forDetermining Transmissivity and Storativity of LowPermeability Rocks by In Situ Measurements UsingPressure Pulse Technique1This standard is issued under the fixed designation D4631;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 parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers a field procedure 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 interest 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.The values in parentheses are for information only.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.Terminology2.1 Definitions of Terms Specific to This Standard:2.1.1 transmissivity,Tthe transmissivity of a formation 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,k,asfollows:K 5 kg/(2)where:=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 defined as the specific storage of a material if itwere homogeneous and porous over the entire interval.Thespecific storage is given as follows:Ss5 gCb1nCw!(4)where:Cb=bulk rock compressibility,Cw=fluid compressibility,andn=formation porosity.2.2 Symbols:2.2.1 Cbbulk rock compressibility M1LT2.2.2.2 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 groundwa-ter literature by hydrogeolists,whereas the symbol k is com-monly used for this term in rock mechanics and soil science.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.2.2.12 efracture aperture L.2.2.13 gacceleration due to gravity LT2.2.2.14 kpermeability L2.1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.21 on Groundwater andVadose Zone Investigations.Current edition approved Sept.15,2008.Published October 2008.Originallyapproved in 1986.Discontinued April 1995 and reinstated as D4631 95.Lastprevious edition approved in 2000 as D4631 95(2000).DOI:10.1520/D4631-95R08.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 2.2.15 nporosity(dimensionless).2.2.16 rwradius of test hole L.2.2.17 ttime elapsed from pulse initiation T.2.2.18dimensionless parameter.2.2.19 dimensionless parameter.2.2.20 viscosity of water ML1T1.2.2.21 density of water ML3.3.Summary of Test Method3.1 Aborehole is first drilled into the rock mass,intersectingthe geological formations for which the transmissivity andstorativity 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 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 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 conditions,the pulse test maybe performed by releasing the pressure on a shut-in well,thereby subjecting the well to a negative pressure puls