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Sonic Scanner - Schlumberger

The inset image in Fig. 3 shows the surface seismic data with normal, rather poor, resolution. In the Sonic Scanner image of Fig. 3, the solid green line indi-

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Text of Sonic Scanner - Schlumberger

Acoustic scanning plat formSonic Scanner Adding radius to borehole acoustics For decades, the oil and gas industry has used borehole acoustic measurementsthroughout the lifecycle of wells to evaluaterock properties in the near-wellbore the industry continues to develop newmethods for producing hydrocarbons more efficiently, a focus on well integrityhas become ever more has designed a tool usingthe latest acoustic technology for advancedacoustic acquisition, including cross-dipoleand multispaced-monopole addition to axial and azimuthal measure-ments, the tool makes a radial measurementto probe the formation for near-wellboreslowness and far-field slowness. Typicaldepths of investigation equal two to threetimes the borehole diameter. The new Sonic Scanner* acoustic scan-ning platform provides advanced types ofacoustic measurements, including borehole-compensated monopole with long and shortspacings, cross-dipole, and cement bondquality. These measurements are then con-verted into useful information about thedrilling environment and the reservoir,which assists in making decisions thatreduce overall drilling costs, improverecovery, and maximize productivity. Thefollowing field examples demonstrate thegreater flexibility in acoustic measurementsoffered by the Sonic Scanner tool. Achieving a better understanding of acoustic propagationTo enable a deeper understanding ofacoustic behavior in and around the bore-hole, the Sonic Scanner tool allows accu-rate radial and axial measurements of thestress-dependent properties of rocks nearthe wellbore. The Sonic Scanner platformprovides multiple depths of investigation,excellent waveform quality, and presenta-tions that reduce the complexity of soniclogging, without compromising the depthof more comprehensive understandingobtained by using the Sonic Scanner plat-form helps to improve fracture planning,sand control, and perforating earlier acoustic measurement barriersRegardless of the formation type, theSonic Scanner platform design overcomesearlier acoustic measurement barriers tosuccessful formation characterization andquantification because it uses a wide-frequency range thatenables characterizing formations as homogeneous or inhomogeneous isotropic or anisotropic uses long- and short-monopole transmitter-receiver spacing is fully characterized with predictableacoustics. Earlier technologies attempted to operateclose to the tool s low-frequency limit, orthey depended on previously acquired formation information to anticipate forma-tion slowness prior to data evaluation. The wide-frequency spectrum used bythe Sonic Scanner tool allows data captureat high signal-to-noise ratios and extractsmaximum data from the formation. Thisdesign feature also helps ensure that dataare acquired regardless of the formationslowness. The monopole transmitters haveFigure 1. The Sonic Scanner tool provides the bene-fits of axial, azimuthal, and radial information fromboth the monopole and the dipole measurements for near-wellbore and far-field slowness Geophysics Improve 3D seismic analysisand seismic tie-ins Determine shear anisotropy Input to fluid substitution Geomechanics Analyze rock mechanics Identify stress regimes Determine pore pressure Evaluate well placementand stability Reservoir characterization Identify gas zones Measure mobility Identify open fractures Maximize selective perfo-rating for sand control Maximize safety window for drawdown pressure Optimize hydraulic fracturing Well integrity Evaluate cement bond quality Benefits Enhance hydrocarbon recovery Make real-time decisions withreal-time quality control Improve reserves estimates Decrease operating time andreduce job costs by eliminat-ing multiple logging runs Reduce uncertainty and operating riskFeatures Robust measurement of compressional and shearslownesses Increased logging speed(1,097 m/h [3,600 ft/h]) Multiple monopole transmitterand receiver spacing High-fidelity wideband wave-forms and dispersion curves Large receiver array Predictable acoustics Enhanced behind-casingmeasurements with simulta-neous cement bond log (CBL)and Variable Density* cementbond quality measurements Extremely rugged electronicpackageenhanced low-frequency output over theentire range of sonic frequencies; andthe dipole transmitters are designed forhigh-output power, high-purity acousticwaves,wide bandwidth, and low Sonic Scanner receivers feature alonger azimuthal array than other acoustictools; , 13 stations and 8 azimuthalreceivers at each station. With the twonear-monopole transmitters straddlingthis array and a third transmitter fartheraway, the short- to long-monopole trans-mitter-to-receiver spacing combinationallows the altered zone to be seen andprovides a radial monopole profile. Seeing beyond the altered zoneThe long-spaced transmitter-to-receiverconcept in earlier acoustic tools wasdesigned for seeing past the alteredzone and attempted to provide an unal-tered slowness range of Sonic Scanner transmitter-to-receiver spacings is both short andlong enough to see the altered zone andthus provide a radial monopole features improve measurementaccuracy of the fluids and the stress-dependent properties of the rocks nearthe wellbore; and that benefits fractureplanning, sand control, and perforatingdesign, as well as shallow-reading-devicepoint selection. The wide-frequency spectrum from the dipole transmitters used in the SonicScanner platform eliminates the need formultiple logging passes that were commonwith the earlier-generation acoustic telemetry, optimized with softwareand hardware, enables increased loggingspeeds and decreased operating times. Obtaining well integrity measurements with high accuracyThe Sonic Scanner tool provides a dis-criminated cement bond log (DCBL) thatcan be obtained simultaneously with thebehind-casing acoustic two monopole transmitters positionedat either end of the Sonic Scanner toolallow 3-ft and 5-ft cement bond log (CBL)and cement bond quality measurementsthat are independent of fluid and tempera-ture effects and do not require demonstrate the DCBL measure-ment accuracy, a logging run made with a Sonic Scanner tool is compared withmeasurements from a CBT* CementBond Tool. The DCBL measurements areindicated in blue and the CBT measure-ments are in black. A very good matchis shown between the measurements of the CBT tool and the azimuthallyaveraged Sonic Scanner platform. The transit time scattering shows in the 7-in, 23-lbm/ft two bond index measurementsshow good agreement, even in the zoneof high eccentralization near the top ofthe interval. Removing uncertainties about formationgeometry and structure A recurring problem encountered inreservoir modeling and simulation is thelack of available image data having a finescale. Until now, the only available alter-natives have been to work with surfaceseismic data, often too coarse in quality,or near-wellbore imaging and its associ-ated limitations. Coupled with the scaleof seismic measurements, additionaluncertainties arise regarding geometryand structure, formation property varia-tion, and fluid ,ftgAPI0 1500 1500 1 200 1200275 295 200 6000 50dB/ftmVXX,700XX,800XX,900XY,000XY,100X Y,200XY,300XY,400VariableDensityVariable DensityDiscriminatedAttenuationVariableD ensityDiscriminatedAmplitudeVariableDens ity*BondIndexTransitTimeSonic ScannerBond index limitCBTSonic ScannerFigure 2. A very good match is shown between azimuthally averaged Sonic Scanner platform and CBT curves (1). Curve scattering indicates eccentering (10 % of the internal radius) in the 7-in casing (2). A good match between bond index measurements is indicated (3).123The inset image in Fig. 3 shows thesurface seismic data with normal, ratherpoor, resolution. In the Sonic Scannerimage of Fig. 3, the solid green line indi-cates the interpreted reservoir top, andthe dashed blue line is the interpretedbottom of the main sand body. The purpleline shows the wellbore relative horizontal position alongthe bottom scale is 20 600 m from left to right, and the vertical scale (deepreading) is in increments of 5 m, show-ing clearly more than 15 m of excellentresolution compared with the surfaceseismic image. The Sonic Scannerimage measurementsare used to update the geological modeland as input to the reservoir simulatorfor predicting pressure with transversely isotropic formation parameters A 3D anisotropy algorithm transforms thecompressional, fast-shear, slow-shear, andStoneley slowness Sonic Scanner meas-urements with respect to the boreholeaxes to anisotropic moduli referenced tothe earth s anisotropy axes. These modulihelp to classify formation anisotropy intoisotropic, transversely isotropic (TI), ororthorhombic types. The moduli alsoassist in identifying microlayering orthin-bedding-induced TI anisotropy (N < 0 implies microlayering-inducedTrueverticaldepth,mXX,000XX,005XX,010XX,015XX,02020600Horizontal position, mFigure 3. Excellent resolution obtained from the Sonic Scanner tool compared with the surface seismic BedDepthm XX,800XY,000XY,200XY,400XY,600XY,800ShaleN_TIV@3D_Aniso_ComGPa 300300Borehole Deviationdeg090Fast Shear DT s/ft44040Compressional DT s/ft44040Stoneley DT s/ft44040Slow Shear DT s/ft44040GPa010GPa010GPa010GPaGPa0505Shear Rigidity inX2 X3 TransverselyIsotropic Vertical PlaneShear Rigidity inX1 X2 TransverselyIsotropic Vertical Plane Shear Rigidity inX2 X3, X1 X2, and X1 X3 Borehole PlaneShear Rigidity inX2 X3 TransverselyBorehole PlaneEquivalent ShearRigidity inBorehole PlaneFigure 4. In this example, the high-gamma ray activity indicates a shaly interval. An isotropic zone (N = 0)extends from XY,500 to XY,600 m, and a high-permeability zone exists from XY,005 to XY,100 m. Top of reservoirBottom of main sand bodyWellboreInterpreted oil /gas contactIsotropicHigh permeabilit yDrilled wellPlanned wellintrinsic anisotropy; N > 0 implies bedding-induced anisotropy), relative magnitudeof principal stresses, and fluid mobility in porous rocks. Figure 4 shows the 3D anisotropy algo-rithm s ability to generate the TI param-eters. With reference to a borehole thatis parallel to the X3 axis, shear modulusor rigidity in the X2-X3 plane and shearrigidity in the X1-X2 plane enablequicklook interpretation of formationanisotropy, stress, and mobility effects. Determining formation mobilityBecause there is essentially no continuouslogging measurement of mobility available,other methods have to be method is to measure formationmobility, which is the ratio of perme-ability to , however, is not always avail-able when it is needed because porosityestimates are often preliminary, wirelinecores require an additional run into thewell, and whole cores are the borehole is in reasonablygood condition, Stoneley waves can beused to measure a continuous mobilityprofile in sands and carbonates. Thesedata can serve as an extension of corepermeability over a continuous intervalto save on coring costs, or to get a quickpermeability estimate for selecting theperforating the effects of tool presenceon sensitive Stoneley wave measurementsis extremely important. The design of theSonic Scanner tool, coupled with exten-sive laboratory and field testing, enableshighly accurate prediction of the effectsof the tool on acoustic measurements in all example in Fig. 5 demonstrateshow the Sonic Scanner Stoneley wavescan be used to measure a continuousmobility profile and obtain a quick per-meability estimate. Other applications ofStoneley permeability include formationevaluation, production testing strategyand programs, and reservoir modeling. Evaluating the mechanical properties of formationsAcoustic measurements have typicallybeen acquired in 1D as a function ofdepth, but seldom in 2D simultaneouslyas a function of depth and azimuthaldirection. And interpretation has almostalways been based on the assumptionthat the formations were homogeneousand isotropic a debatable assumption, 01002404030020016060PorositygAPI%ing/cm3 Gamma RayQualityFlagX,X20X,X40X,X60CaliperSign al-to-NoiseRatioDepthBulk Compressional s/ft s/ft s/ft s/ftDT ShearDT StoneleyDT mud016,000 s/ftSonic Scanner Stoneley110,000110,000SandCoalWaterBound WaterOilmD/cPmD/cPStoneley MobilityMobility ErrorMDT MobilityShale300150X,X00Figure 5. Mobility measured by the Sonic Scanner tool is shown in Track 4. The red dots indicate mobility values measured by the MDT* Modular Formation Dynamics Tester, which show good best, because of fracture alignment,dipping beds, unbalanced stresses, andformation damage from drilling. The Sonic Scanner tool enables a full3D characterization of the formation byadding the radial dimension from themultiple transmitter-receiver spacings,along with wideband frequency measure-ments and acquisition of all acousticmodes propagating in the borehole. Fromthe expanded set of measurements, dom-inant formation data can be evaluatedand the appropriate processing tech-niquescan be selected to extract 3Dacoustical properties. In a tight-gas reservoir, formation evaluation data and wellbore imageswere combined with Sonic Scannershear wave anisotropy and Stoneleywave data shown in Fig. 6. Wellbore stability simulation was used to ensureconsistency between the mechanicalearth model and the logging and drillingdata. The mechanical earth model wasthen applied to optimize subsequentdrilling operations. Detecting and evaluating open fractured intervals Understanding the mechanisms of aniso-tropy can be important when selectingthe right hydraulic fracture fluid for awell, especially if there is stress-inducedanisotropy or intrinsic anisotropy relatedto the presence of natural fractures. TheSonic Scanner tool can be used in evalu-ating the type of anisotropy, in additionto differentiating between open naturalfractures and drilling-induced fractures. The fractures shown in the FMI*Fullbore Formation MicroImager log in Fig. 7 are near vertical. Upon foot-by-foot examination, they were origi-nally interpreted to be drilling wave measurements from theSonic Scanner tool made it clear that thefractures were open naturalfractures and not drilling additional sonic data undoubtedlyprevented the operator from making anincorrect interpretation, which wouldhave led to selection of a high-gel fracturefluid that would have destroyed the permeability of the naturally fracturedformation. In this situation, encapsulatedbreakers are much less effective, and aneffective treatment can be addition to preventing fluid loss, this information would also be critical in preventing cement loss during com-pletion RayBit SizeCaliper 1DepthXX,050XX,100ftCaliper 2Stoneley Fractures0gAPI1504in144in1401000100Fast- In-LineVariableDensitySlow-In-LineVariab leDensity0 s 6,0000 s100 DT Shear Fast DT Shear Fast DT Shear Slow DT Shear Slow 80 s/ft 280SlownessProjectionSlownessFrequencyAn alysisSlownessProjectionSlownessFrequenc yAnalysis80 s/ft 28080 s/ft 28080 s/ft 28080 s/ft 28080 s/ft 28080 s/ft 280ResistiveConductiveFMI ImageDynamic ImageHorizontal Scale: 1 North80 s/ft 7. Stoneley wave measurements enabled determination that the fractures were natural, not drilling s ModulusEarth Stress PloFMI logtPore pressure max Shale max Sand max Sand-Wbs min Sand min Sand-Wbs max Shale-Wbs Vertical min Shale-Wbs min ShaleMud lossDataFRAC* serviceKickPressure Xpress*serviceDelta StabilityEffective axial stress, psi 0 1 strain, % 6 8 10 12 14 16 18 20 22Equivalent mud density, ppg-10 -5 0 5 10Distance, inDistance (in)x10o3= 3000 psiSample 67-S1Depth: ,0004,000Tr uever ticaldepth,ft6,0008,00010,0001050-5-10E - x 10 psiFigure 6. A mechanical earth model can be constructed and compared with independent measurements of rock properties and in situ stresses. 05-FE-130 2005 SchlumbergerNovember 2005*Mark of SchlumbergerProduced by Schlumberger Marketing Scanner Measurement Specifications OutputCompressional and shear DT, full waveforms, cement bond quality waveformsMax. logging speed1,097 m/h [3,600 ft/h] Range of measurementStandard shear slowness: < 4,921 s/m [1,500 s/ft]Vertical resolution< [6-ft] processing resolution for [6-in] sampling rate AccuracyDT: < s/m [2 s/ft] or 2% up to [14-in] hole size < s/m [5 s/ft] or 5% for > [14-in] hole sizeMud weight or type limitsNoneCombinabilityFully combinable with other tools Acquisition speed depends on product class and sampling rate. Vertical resolution of < cm [<2 ft] is Scanner Mechanical Specifications Max. temperature177 degC [350 degF]Max. pressure138 MPa [20,000 psi]Borehole cm [ in] cm [22 in]Outer cm [ in] m [ ft] m [22 ft] Weight383 kg [844 lbm] 188 kg [413 lbm] Tension157 kN [35,000 lbf]Compression13 kN [3,000 lbf] Advanced toolstring, including isolation joint Basic toolstring, near monopoles only

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