1、Designation: D 4645 04e1Standard Test Method forDetermination of the In-Situ Stress in Rock Using theHydraulic Fracturing Method1This standard is issued under the fixed designation D 4645; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revi
2、sion, 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.e1NOTEFigure 2 was corrected editorially in September 2004.1. Scope*1.1 This test method covers the determinati
3、on of the in-situstate of stress in rock by hydraulic fracturing.NOTE 1Hydraulic fracturing for stress determination is also referredto as hydrofracturing, and sometimes as minifracing. Hydraulic fracturingand hydrofracturing may also refer to fracturing of the rock by fluidpressure for the purpose
4、of altering rock properties, such as permeabilityand porosity.1.2 Hydraulic fracturing is the widely accepted field methodavailable for in situ stress measurements at depths greater than50 m. It can be used in drill holes of any diameter.1.3 Hydraulic fracturing can also be used in short holes forwh
5、ich other stress measuring methods, such as overcoring, arealso available. The advantage of hydraulic fracturing is that ityields stresses averaged over a few square metres (the size ofthe induced hydraulic fracture) rather than over grain sizeareas, as in the case of overcoring techniques.1.4 All o
6、bserved and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D 6026.1.4.1 The method used to specifiy how data are collected,calculated, or recorded in this standard is not directly related tothe accuracy to which the data can be applied in
7、design or otheruses, or both. How one applies the results obtained using thisstandard is beyond its scope.1.5 The values stated in SI units are to be regarded as thestandard.1.6 This standard does not purport to address all of thesafety problems, if any, associated with its use. It is theresponsibil
8、ity 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. Referenced Documents2.1 ASTM Standards:2D 653 Terminology Relating to Soil, Rock and ContainedFluidsD 2113 Practice for Diamond Core Drill
9、ing for Site Inves-tigationD 3740 Practice for Minimum Requirements for AgenciesEngaged in the Testing and/or Inspection of Soil and Rockas Used in Engineering Design and ConstructionD 5079 Practices for Preserving and Transporting RockCore SampleD 6026 Practice for Using Significant Digits in Geote
10、chni-cal Data3. Terminology3.1 For terminology used in this test method, refer toTerminology D 653.3.2 Definitions of Terms Specific to This Standard:3.2.1 breakdown pressurethe pressure required to inducea hydraulic fracture in a previously intact test interval.3.2.2 in-situ stressrock stress measu
11、red in situ (as op-posed to by remote sensing).3.2.3 secondary breakdown (or fracture reopening, or re-frac) pressurethe pressure required to reopen a closed,previously induced hydrofracture after the test interval pressurehas been allowed to return to its initial condition.3.2.4 shut-in pressure (o
12、r ISIP (instantaneous shut-inpressure)the pressure reached when the induced hydrofrac-ture closes back after pumping is stopped.3.2.5 vertical and horizontal principal stressesthe threeprincipal stresses in situ are generally assumed to act one in thevertical direction and the other two in the horiz
13、ontal plane.1This 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 Jan. 1, 2004. Published February 2004. Originallyapproved in 1987. Last previous edition approved in 1997 a
14、s D 4645 87 (1997).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 website.1*A Summary of Changes section appears at
15、the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4. Summary of Test Method4.1 A section of the borehole is isolated by pressurizing twoinflatable rubber packers. The fluid pressure in the sealed-offinterval bet
16、ween the two packers is raised by pumping fluidinto it at a controlled rate until a fracture occurs in the boreholewall. Pumping is stopped and the pressure in the interval isallowed to stabilize. The pressure is then reduced to the porepressure level of the rock formation, and the pressurizationpro
17、cess is repeated several times maintaining the same flowrate. Additional pressure cycles can be conducted at differentflow rates. The magnitudes of the principal stresses arecalculated from the various pressure readings. The orientationof the fracture is detected in order to determine the orientatio
18、nof the transverse principal stresses. A typical pressure versustime, flow rate versus time record for a test interval is shown inFig. 1.5. Significance and Use5.1 Limitations:5.1.1 The depth of measurement is limited only by thelength of the test hole.5.1.2 Presently, the results of the hydraulic f
19、racturingmethod can be interpreted in terms of in-situ stresses only if theboreholes are approximately parallel to one of the threeprincipal in-situ stresses. Unless evidence to the contraryexists, vertical boreholes are assumed to be parallel to one ofthe in-situ principal stresses.5.1.3 When the p
20、rincipal stress parallel to the borehole axisis not the least principal stress, only the two other principalstresses can be determined directly from the test. If theminimum stress acts along the borehole axis, fractures bothparallel and perpendicular to the axis of the borehole aresometimes induced
21、by the test, allowing for the determinationof all three principal stresses.5.1.4 In the unlikely event that the induced fracture changesorientation away from the borehole, its trace on the boreholewall cannot be used in stress determinations.5.2 Assumptions:5.2.1 The rock tested is assumed to be lin
22、early elastic,homogeneous, and isotropic. Any excessive departure fromthese assumptions could affect the results.5.2.2 Vertical boreholes are assumed to be substantiallyparallel to one of the in-situ principal stresses, since it has beenestablished from many geological observations and stressmeasure
23、ments by other methods that in most cases one of theprincipal stresses is vertical to subvertical.5.3 Hydraulic fracturing determination of in-situ stressescan be complicated by rock matrix porosity, naturally occur-ring fractures, the presence of nearby underground openings,and local variations in
24、the stress field.NOTE 2The quality of the result produced by this standard isdependent on the competence of the personnel performing it, and thesuitability of the equipment and facilities used. Agencies that meet thecriteria of Practice D 3740 are generally considered capable of competentand objecti
25、ve testing/sampling/inspection, etc. Users of this standard arecautioned that compliance with Practice D 3740 does not in itself assurereliable results. Reliable results depend on many factors; Practice D 3740provides a means of evaluating some of those factors.6. Apparatus6.1 Tripod or Drilling Rig
26、Equipment for lowering thehydraulic fracturing tool into and lifting it from the test hole isnecessary. To facilitate the lowering and lifting of the down-hole hydrofracturing tool, a tripod or a drilling rig is set up ontop of the test hole. When high-pressure tubing or drilling pipes(rods) are use
27、d for lowering the tool, it is necessary to use adrilling rig with a derrick and hoist capable of lifting thecombined weight of the pipe and instruments. When awireline-flexible hose system is used for hydrofracturing, awell-designed tripod capable of carrying the weight of thetesting tool, wireline
28、, and hoses is employed.6.2 Straddle PackerBorehole sealing is accomplished bytwo inflatable rubber packers, spaced apart a distance equal toat least six hole diameters, and interconnected mechanicallyand hydraulically to form one unit called the straddle packer.6.3 High-Pressure Tubing or HosePacke
29、r and test-interval pressurization is accomplished either by a high-pressure tubing (drilling rod is often a good substitute) or byhigh-pressure hose, or by a combination of the two (wheretubing is used to pressurize the interval, and the hose, which isstrapped to the outside of the tubing facilitat
30、es packer infla-tion). The hose or the tubing, or both, are connected hydrau-lically at one end to pumps or pressure generators (0.70 MPa,NOTE 1In this test the flow rate was maintained constant during the first three cycles. In the fourth cycle a very slow flow rate was maintained suchthat the top
31、level of the pressuretime curve could be considered as the upper limit for the shut-in pressure.FIG. 1 Typical Pressure Time, Flow Rate Time Records During HydrofracturingD464504e120 to 25 L/min are recommended ratings), and at the other to thestraddle packer and the test interval between the packer
32、s (Fig.2). It has been found that pump capacities similar to thosegiven here can overcome almost any common rock permeabil-ity and facilitate pressurization.6.4 Pressure Transducers and Flow MeterPressure trans-ducers (10 to 70 MPa) are used to monitor the test intervalpressure either on the surface
33、 or at the test depth (or both). Insome setups, the packer pressure is also monitored in the sameway as the test interval. A flow meter is used to monitor theflow rate of fluid into the test interval. The sensing devices feedinto multichannel analog time-base recorders for real-timecontinuous perman
34、ent recording. Digital computer recording iscarried out for the storage of test pressure and flow rateinformation which can later be used to provide a thoroughanalysis of the test data.6.5 Hydrofracture Delineation Equipment:6.5.1 Impression PackerThe presence and orientation ofthe induced hydrofrac
35、ture is commonly recorded by the use ofan impression packer, which is an inflatable packer with anouter layer of very soft semicured rubber. An orienting device,in the form of a magnetic borehole surveying tool or agyroscopic borehole surveying tool, is used to determine thedirection and inclination
36、 of the hydrofracture traced on theimpression packer (Fig. 3).6.5.2 Borehole TeleviewerAn alternative to the orientedimpression packer is the borehole televiewer, which is a soniclogging tool that takes an oriented acoustic picture of theborehole wall. This tool is considerably faster than the impre
37、s-sion packer because it can take readings from an entire test holein one trip. The impression packer requires retrieval after eachtest so that the outer cover can be properly marked or replacedbefore lowering the tool to the next zone. However, theborehole televiewer is considerably more expensive
38、to own orrent, does not always discern hydrofractures that have closedtightly after the pressurization stage of the test, and requires afluid filled borehole.7. Personnel Prequalification and Equipment Verification7.1 Test PersonnelThe performance of a hydraulic frac-turing test may vary from locati
39、on to location, and from onerock type to the next. Quick decisions, which are often requiredin the field, may change the outcome of the tests. Hence, thetest supervisor should be a person who thoroughly understandsthe theoretical aspects of the test method, and who has hadsubstantial experience in c
40、onducting such tests in a variety ofrock types, depths, and locations.7.2 Drilling PersonnelQuality drilling is important tomaintaining a reasonably straight vertical hole and in keepinga nearly circular cross-section.7.3 Equipment VerificationThe compliance of all equip-ment and apparatus with perf
41、ormance specifications shall beverified. Performance specification is generally done by cali-brating the equipment and measurement systems.8. Procedure8.1 Drill a borehole (in most cases in the vertical direction)to the depth of interest. Diamond bit coring is recommendedFIG. 2 Suggested Schematic D
42、ownhole and Surface Equipment Set Up for Hydraulic FracturingD464504e13because it yields a continuous core and leaves a smooth anduniformly circular borehole wall.8.2 Select testing zones of solid unfractured rock within thedrilled hole, making use of the core, if available, or one ormore geophysica
43、l logs (such as caliper, density, boreholeteleviewer) if they have been run.8.3 To seal off the test interval, lower the straddle packer tothe predetermined depth of testing and pressurize hydraulicallyso as to inflate packers onto the wall of the borehole. Thepressurization, typically using water,
44、is generated on thesurface by a high-pressure pump and is conveyed to the packerby means of tubing or flexible hose.8.4 With the packers well anchored to the sidewalls (apacker pressure of 3 MPa is usually sufficient at this stage ofthe test), pressurize hydraulically (typically using water) thetest
45、 interval between the packers at a constant flow rate. Thisrate may change from one test hole to the next, often dependingon the permeability of the rock (the higher the permeability thehigher the rate). The general principle is to affect hydrofrac-turing within a minute or so from the beginning of
46、intervalpressure rise. Throughout the interval pressurization, maintainpacker pressure at a level of about 2 MPa higher than theinterval to ensure that no leak-offs occur. As the rock hydrof-ractures, the breakdown pressure is reached. If pumping is thenstopped without venting the hydraulic line, th
47、e pressure willsuddenly drop and settle at a lower level called the shut-inpressure. Repeated cycling of the pressurization procedureusing the same flow rate will yield the secondary breakdownpressure (the pressure required to reopen a preexisting hydrof-racture), and additional values of the shut-i
48、n pressure.8.5 Continuously record the entire pressurization processboth as pressure versus time and as flow rate versus time.8.6 At the conclusion of the test, vent the packer pressure toallow the packers to return to their original diameter. The entireFIG. 3 Suggested Schematic Downhole and Surfac
49、e Equipment Set Up for Taking a Packer Impression of theHydraulic FractureD464504e14straddle packer assembly can then either be moved to the nexttest zone or pulled out of the borehole.8.7 The most common tool for determining hydraulic frac-turing orientation is the oriented impression packer. Lower thepacker on the drill-rod or wireline to the test interval afterhydrofracturing, and inflate to a pressure higher than thesecondary breakdown pressure or the shut-in pressure (which-ever is larger). This ensures that the packer will slightly openthe hydrofracture
