WO2007089438A2 - Vérification par simulateur de conductivité dans un trou de forage et équilibrage des bobines transversales - Google Patents

Vérification par simulateur de conductivité dans un trou de forage et équilibrage des bobines transversales Download PDF

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Publication number
WO2007089438A2
WO2007089438A2 PCT/US2007/001321 US2007001321W WO2007089438A2 WO 2007089438 A2 WO2007089438 A2 WO 2007089438A2 US 2007001321 W US2007001321 W US 2007001321W WO 2007089438 A2 WO2007089438 A2 WO 2007089438A2
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WIPO (PCT)
Prior art keywords
tool
coil
coils
longitudinal axis
transmitter
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PCT/US2007/001321
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English (en)
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WO2007089438A3 (fr
Inventor
Stanislas W. Forgang
Randy Gold
Luis M. Pelegri
Michael S. Crosskno
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Baker Hugues Incorporated
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Priority claimed from US11/340,785 external-priority patent/US7319331B2/en
Priority claimed from US11/371,052 external-priority patent/US7205770B2/en
Application filed by Baker Hugues Incorporated filed Critical Baker Hugues Incorporated
Priority to CA002640705A priority Critical patent/CA2640705A1/fr
Priority to GB0813803A priority patent/GB2457324B/en
Priority to EA200801744A priority patent/EA014403B1/ru
Priority to BRPI0707316-0A priority patent/BRPI0707316A2/pt
Publication of WO2007089438A2 publication Critical patent/WO2007089438A2/fr
Publication of WO2007089438A3 publication Critical patent/WO2007089438A3/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
    • G01V3/18—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging
    • G01V3/26—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging operating with magnetic or electric fields produced or modified either by the surrounding earth formation or by the detecting device
    • G01V3/28—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging operating with magnetic or electric fields produced or modified either by the surrounding earth formation or by the detecting device using induction coils

Definitions

  • the present invention is related to the field of apparatus design in the field of oil exploration.
  • the present invention describes a method for calibrating multicomponent logging devices used for detecting the presence of oil in boreholes penetrating a geological formation.
  • Electromagnetic induction resistivity well logging instruments are well known in the art. Electromagnetic induction resistivity well logging instruments are used to determine the electrical conductivity, and its converse, resistivity, of earth formations penetrated by a borehole. Formation conductivity has been determined based on results of measuring the magnetic field of eddy currents that the instrument induces in the formation adjoining the borehole. The electrical conductivity is used for, among other reasons, inferring the fluid content of the earth formations. Typically, lower conductivity (higher resistivity) is associated with hydrocarbon-bearing earth formations.
  • the physical principles of electromagnetic induction well logging are well described, for example, in, J. H. Moran and K. S.
  • the conventional geophysical induction resistivity well logging tool is a probe suitable for lowering into the borehole and it comprises a sensor section containing a transmitter and receiver and other, primarily electrical, equipment for measuring data to infer the physical parameters that characterize the formation.
  • the sensor section, or mandrel comprises induction transmitters and receivers positioned along the instrument axis, arranged in the order according to particular instrument or tool specifications and oriented parallel with the borehole axis.
  • the electrical equipment generates an electrical voltage to be further applied to a transmitter induction coil, conditions signals coming from receiver induction coils, processes the acquired information, stores or by means of telemetry sending the data to the earth surface through a wire line cable used to lower the tool into the borehole.
  • the oscillating magnetic field produced by this arrangement results in the induction of currents in the formations which are nearly proportional to the conductivity of the formations. These currents, in turn, contribute to the voltage induced in one or more receiver coils. By selecting only the voltage component which is in phase with the transmitter current, a signal is obtained that is approximately proportional to the formation conductivity.
  • the basic transmitter coil and receiver coil has axes which are aligned with the longitudinal axis of the well logging device. (For simplicity of explanation, it will be assumed that the borehole axis is aligned with the axis of the logging device, and that these are both in the vertical direction.
  • a conventional induction logging tool with transmitters and receivers (induction coils) oriented only along the borehole axis responds to the average horizontal conductivity that combines the conductivity of both sand and shale. These average readings are usually dominated by the relatively higher conductivity of the shale layers and exhibit reduced sensitivity to the lower conductivity sand layers where hydrocarbon reserves are produced.
  • loggers have turned to using transverse induction logging tools having magnetic transmitters and receivers (induction coils) oriented transversely with respect to the tool longitudinal axis.
  • Such instruments for transverse induction well logging has been described in PCT Patent publication WO 98/00733 of Beard et al. and US 5452761 to Beard et al.; US 5999883 to Gupta et al.; and US 5781436 to Forgang et al.
  • transversal coil arrays In transverse induction logging tools, the response of transversal coil arrays is also determined by an average conductivity; however, the relatively lower conductivity of hydrocarbon-bearing sand layers dominates in this estimation.
  • the volume of shale/sand in the formation can be determined from gamma-ray or nuclear well logging measurements. Then a combination of the conventional induction logging tool with transmitters and receivers oriented along the well axis and the transversal induction logging tool can be used for determining the conductivity of individual shale and sand layers.
  • the acquired data quality depends on the formation electromagnetic parameter distribution (conductivity or resistivity) in which the tool induction receivers operate.
  • the logging tool measures magnetic signals induced by eddy currents flowing in the formation. Variations in the magnitude and phase of the eddy currents occurring in response to variations in the formation conductivity are reflected as respective variations in the output voltage of receivers.
  • these receiver induction coil voltages are conditioned and then processed using analog phase sensitive detectors or digitized by digital to analog converters and then processed with signal processing algorithms. The processing allows for determining both receiver voltage amplitude and phase with respect to the induction transmitter current or magnetic field waveform. It has been found convenient for further uphole geophysical interpretation to deliver the processed receiver signal as a vector combination of two voltage components: one being in- phase with transmitter waveform and another out-of-phase, quadrature component.
  • the in-phase coil voltage component amplitude is the more sensitive and noise-free indicator of the formation conductivity.
  • the general hardware problem is typically associated with an unavoidable electrical field that is irradiated by the tool induction transmitter simultaneously with the desirable magnetic field, and it happens in agreement with Maxwell's equations for the time varying field.
  • the transmitter electrical field interacts with remaining modules of the induction logging tool and with the formation; however, this interaction does not produce any useful information. Indeed, due to the always-existing possibility for this field to be coupled directly into the receiver part of the sensor section through parasitic displacement currents, it introduces the noise. When this coupling occurs, the electrical field develops undesirable electrical potentials at the input of the receiver signal conditioning, primarily across the induction coil receiver, and this voltage becomes an additive noise component to the signal of interest introducing a systematic error to the measurements.
  • Another source of hardware errors introduced into the acquired log data is associated electrical potential difference between different tool conductive parts and, in particular, between transmitter and receiver pressure housings if these modules are spaced apart or galvanically separated. These housings cover respective electronic modules and protect them from exposure to the harsh well environment including high pressure and drilling fluids.
  • the pressure housing has a solid electrical connection to the common point of the electronic module it covers, however, design options with "galvanically" floating housings also exist. If for some reasons, mainly imperfections in conventional induction tools, the common points of different electronic modules have an electrical potential difference between them, this difference will appear on the pressure housings. It may occur even in a design with
  • this shield simultaneously creates a galvanic path for the currents that could be driven by pressure housings and/or electronic potential difference, or induced by the induction transmitter (as discussed in US Patent # 6,586,939 to Fanini et al, having the same assignee as the present application and the contents of which are incorporated herein by reference).
  • This path apparently exists along the shield's external surface and for a given frequency its depth and impedance has been controlled by the shield geometry, material conductivity and magnetic permeability.
  • the time varying currents also generate a respective magnetic field that crosses induction receiver coils and induces error voltages.
  • Fanini '939 discloses a transverse induction logging tool having a transmitter and receiver for downhole sampling of formation properties, the tool having a symmetrical shielded split-coil transmitter coil and a bucking coil interposed between the split transmitter coils to reduce coupling of the transmitter time varying magnetic field into the receiver.
  • the tool provides symmetrical shielding of the coils and grounding at either the transmitter or receiver end only to reduce coupling of induced currents into the received signal.
  • the tool provides an insulator between receiver electronics and the conductive receiver housing having contact with conductive wellbore fluid, to reduce parasitic current flowing in a loop formed by the upper housing, feed through pipe, lower housing and wellbore fluid adjacent the probe housing or mandrel.
  • An internal verification loop is provided to track changes in transmitter current in the real and quadrature component of the received data signal.
  • Fanini '675 discloses a transverse induction logging tool having a transmitter and receiver for downhole sampling of formation properties, the tool having a symmetrical shielded split-coil transmitter coil and a bucking coil interposed between the split transmitter coils to reduce coupling of the transmitter time varying magnetic field into the receiver.
  • the tool provides symmetrical shielding of the coils and grounding at either the transmitter or receiver end only to reduce coupling of induced currents into the received signal.
  • the tool provides an insulator between receiver electronics and the conductive receiver housing having contact with conductive wellbore fluid, to reduce parasitic current flowing in a loop formed by the upper housing, feed through pipe, lower housing and wellbore fluid adjacent the probe housing or mandrel.
  • An internal verification loop is provided to track changes in transmitter current in the real and quadrature component of the received data signal
  • One embodiment of the invention is a method of preparing a multicomponent induction tool having a plurality of transmitter coils and a plurality of receiver coils.
  • the method includes positioning the logging tool in a calibration area substantially free from components capable of interfering with magnetic and electric fields produced by the tool.
  • a first conductive housing of the tool is coupled with a second conductive housing of the tool through a borehole conductivity simulator having an impedance similar to that of a borehole environment.
  • a first coil of the plurality of transmitter coils is activated and the signal in a first coil of the plurality of receiver coils is measured.
  • the first coil of the plurality of transmitter coils is moved relative to a conductive feed-through pipe between the first housing and a second housing to reduce the magnitude of the signal.
  • the first coil of the plurality of receive accordance is moved relative to the feed-through pipe until the magnitude of the signal is substantially equal to zero. That method may further include positioning the first coil of the plurality of receiver coils in an eccentered position in the logging tool prior to making the measurement. The method may further comprise orienting the logging tool with its longitudinal axis substantially parallel to the ground.
  • the first coil of the plurality of transmitter coils may have an axis that is substantially parallel to a longitudinal axis of the tool or substantially orthogonal to a longitudinal axis of the tool.
  • the first coil for the plurality of receiver coils may have an axis that is substantially parallel to a longitudinal axis of the tool or substantially orthogonal to a longitudinal axis of the tool.
  • the method may further include rotating the tool about a longitudinal axis of the tool, activating a second coil of the plurality of transmitter coils and measuring an additional signal in a second coil of the plurality of receiver coils, and moving the second coil of the plurality of transmitter coils with respect to the feed-through pipe to reduce the magnitude of the additional signal.
  • the method may further include magnetically coupling the tool to a calibrator, activating the first coil of the plurality of transmitter coils, and determining from a signal received at a specific coil of the plurality of receiver coils a transfer function between the specific coil and a first coil of the gravity of transmitter coils.
  • the tool may be positioned inside the calibrator.
  • Another embodiment of the invention is an apparatus for evaluating performance of the multicomponent induction logging tool having a plurality of transmitter coils and a plurality of receiver coils.
  • the tool is positioned in a calibration area substantially free from components capable of interfering with magnetic and electric fields produced by the tool.
  • the apparatus includes a borehole conductivity simulator having an impedance similar to that of a borehole environment, the borehole conductivity simulator coupling a first housing of the tool with a second housing of the tool.
  • the apparatus includes a processor configured to activate a first coil of the plurality of transmitter coils.
  • the apparatus further includes a first coil of the plurality of receiver coils configured to provide a signal responsive to the activation of the first transmitter coil.
  • the apparatus includes a device configured to move the first coil of the plurality of transmitter coils relative to the first coil of the plurality of receiver coils to reduce the magnitude of signal, and move the first coil of the plurality of receiver coils relative to the conductive feed- through pipe until the magnitude of the signal is substantially zero.
  • the device may further be configured to position the first coil of the plurality of receiver coils in an eccentered position in the logging tool.
  • the first coil of the plurality of transmitter coils may have an axis that is substantially parallel to the longitudinal axis of the tool or substantially or organelle to a longitudinal axis of the tool.
  • the first coil of the plurality of receiver coils may have an axis that is substantially parallel to a longitudinal axis of the tool or substantially orthogonal to a longitudinal axis of the tool.
  • the apparatus may further include a calibrator wherein the logging tool is magnetically coupled with a calibrator and the processor is further configured to determine from the signal a transfer function between the first coil of the plurality of transmitters and the first coil of the plurality of receivers.
  • FIG. 1 shows schematically a wellbore extending into a laminated earth formation, into which wellbore an induction logging tool as used according to the invention has been lowered;
  • FIG. 2A illustrates a conventional resistivity measurement in the vertical direction
  • FIG. 2B illustrates a resistivity measurement in the horizontal direction
  • FIG.3 is an overall flow chart of the procedures of the present invention
  • FIG. 4 illustrates a borehole conductivity simulator (BCS) used in the present invention
  • FIG.5 illustrates an assembly for calibrating of transverse arrays in a logging tool
  • FIG. 6 illustrates an assembly for calibrating longitudinal arrays in a logging tool
  • FIGS. 7-8 illustrate assemblies for calibrating XY cross-component arrays
  • FIGS. 9-10 illustrate assemblies for calibrating XZ cross-component arrays.
  • the instrument structure provided by the present invention enables increased stability and accuracy in an induction wellbore logging tool and its operational capabilities, which, in turn, results in better quality and utility of wellbore data acquired during logging.
  • the features of the present invention are applicable to improve the structure of a majority of known induction tools.
  • FIG. 1 schematically shows a wellbore 1 extending into a laminated earth formation, into which wellbore an induction logging tool as used according to the present invention has been lowered.
  • the wellbore in FIG. 1 extends into an earth formation which includes a hydrocarbon-bearing sand layer 3 located between an upper shale layer 5 and a higher conductivity than the hydrocarbon bearing sand layer 3.
  • An induction logging tool 9 used in the practice of the invention has been lowered into the wellbore 1 via a wire line 11 extending through a blowout preventor 13 (shown schematically) located at the earth surface 15.
  • the surface equipment 22 includes an electric power supply to provide electric power to the set of coils 18 and a signal processor to receive and process electric signals from the receiver coils 19. Alternatively, the power supply and/or signal processors are located in the logging tool.
  • the relative orientation of the wellbore 1 and the logging tool 9 with respect to the layers 3, 5, 7 is determined by two angles, one of which ⁇ as shown in the FIG. 1. For determination of these angles see, for example, US 5999883 to Gupta, et al.
  • the logging tool 9 is provided with a set of transmitter coils 18 and a set of receiver coils 19, each set of coils 18, 19 being connected to surface equipment 22 via suitable conductors (not shown) extending along the wire line 11.
  • the relative orientation of the wellbore 1 and the logging tool 9 with respect to the layers 3, 5, 7 is determined by two angles, one of which ⁇ as shown in the FIG. 1.
  • the logging tool 9 is provided with a set of transmitter coils 18 and a set of receiver coils 19, each set of coils 18, 19 being connected to surface equipment 22 via suitable conductors (not shown) extending along the wire line 11.
  • Each set of coils 18 and 19 includes three coils (not shown), which are arranged such that the set has three magnetic dipole moments in mutually orthogonal directions, that is, in x, y and z directions.
  • the three-coil transmitter coil set transmits magnetic fields T x , T y and T 2 ; the receiver coils measure induced signal from main directions R x , R y and R z as well as the cross components, Rxy, Rx 2 and Rzy.
  • coil set 18 has magnetic dipole moments 26a, 26b, 26c
  • coil set 19 has magnetic dipole moments 28a, 28b, 28c.
  • the transmitter coil set 18 is electrically isolated from the receiver coil set 19.
  • the coils with magnetic dipole moments 26a and 28a are transverse coils, that is they are oriented so that the magnetic dipole moments are oriented perpendicular to the wellbore axis, whereby the direction of magnetic dipole moment 28a is opposite to the direction of magnetic dipole moment 26a. Furthermore the sets of coils 18 and 19 are positioned substantially along the longitudinal axis of the logging tool 9.
  • conventional induction logging tools provide a single transmitter and receiver coil that measure resistivity in the horizontal direction.
  • the resistivities of adjacent high resistivity sand and ' low resistivity shale layers appear in parallel, thus the resistivity measurement is dominated by low resistivity shale.
  • a transverse coil is added to measure resistivity in the vertical direction. In the vertical direction, the resistivity of the highly resistive sand and low resistivity shale are appear in series and thus the vertical series resistivity measurement is dominated by the resistivity of the highly resistive sand.
  • the magnitude of the local eddy currents is dependent upon their location relative to the transmitter coil set 18, the conductivity of the earth formation at each location, and the frequency at which the transmitter coil set 18 is operating.
  • the local eddy currents act as a source inducing new currents, which again induce further new currents, and so on.
  • the currents induced into the sand layer 3 induces a response magnetic field in the formation, which is not in phase with the transmitted magnetic field, but which induces a response signal in receiver coil set 19.
  • the magnitude of the current induced in the sand layer 3 depends on the conductivity of the sand layer 3, the magnitude of the response current in receiver coil set 19. The magnitude also depends on the conductivity and thereby provides an indication of the conductivity of the sand layer 3.
  • the magnetic field generated by transmitter coil set 18 not only extends into sand layer 3, but also in the wellbore fluid and in the shale layers 5 and 7 so that currents in the wellbore fluid and the shale layers 5 and 7 are induced.
  • the fully made tool is placed in calibration area which has a small number of external parts that could interfere with magnetic and electric fields produced or received by the tool and thus affect tool readings (machinery, measurement tools, etc.). For example, positioning the tool at approximately 15 ft (4.6m) above the ground typically reduces the tool environmental reading to a value less than about 10 mS/m. The tool is positioned parallel to the Earth with the array to be adjusted pointing normal to the ground.
  • FIG. 4 illustrates the BCS, comprising an assembly of conductor 401 and resistor
  • resistor 410 which electrically couples top housing 405 and bottom housing 404.
  • a closed circuit is thus created from bottom housing 404 through resistor 410 through top housing 405 through a feed- through pipe running from bottom housing to top housing through mandrel 408.
  • the value of resistor 410 can be configured to be approximately equal to a total conductivity (or resistivity) value between top and bottom housings which the tool would experience inside a borehole according to its specifications.
  • a resistance value of approximately 20 Ohms is typically chosen.
  • the tool becomes very sensitive to the axial current that could be induced by the array transmitter in the following loop: "top housing — conductive feed- through pipe - bottom housing - BCS".
  • the magnitude of the current will be proportional to the array coils displacement from their longitudinal alignment (almost true for small displacements ⁇ 1/d) and simulator resistor value.
  • the transmitter coil may be moved in the plane parallel to the ground. This coil movement is performed until an absolute minimum in the receiver reading is reached.
  • the receiver coil is positioned off-center relative to the tool. At this position, the receiver signal is particularly sensitive to misalignment of the transmitter. This makes it easier to determine the minimum.
  • the transmitter coil frame is fixed inside the mandrel. This could be accomplished with the sets of non- conductive screws and/or with epoxy; however, alternative means could be applied, as well. Shorting the isolator between the upper housing and the mandrel is done to significantly increase the magnitude of the axial current in this test procedure and, therefore, increase accuracy of balancing.
  • a similar positioning may be done in the vertical direction. As discussed below, the tool is more sensitive to mis-positioning in the vertical direction than in the horizontal direction. Suitable positioning screws may be provided in the logging tool to accomplish this movement.
  • the receiver coil is moved to a position where the signal and the receiver coil is zero. When this is done, the particular transmitter and receiver are properly balanced. The description above has been made with respect to movement of the coils relative to each other. It is to be understood that when these movements are made, the coils are also being moved relative to the feed-through pipe.
  • the tool is rotated about its axis and similar procedure has been performed with next horizontal array.
  • the instrument might have a plurality of transverse and tilted arrays so that similar tuning could be developed for each sensor.
  • the tool isolation short is removed and mandrel is covered with the non-conductive pressure sleeve.
  • Calibration of transfer coefficient is done after the instrument is positioned in the low conductive calibration environment and inserted inside the calibrator. The calibration principle lies in introducing a certain dissipative load through magnetic coupling for calibrating array so that its signal readings are identical to the values to be read while logging a homogeneous formation with finite conductivity.
  • the tool readings while the calibrator loop is not loaded reflect environmental conductivity and, in particular, ground conductivity. This data has to be known and stored for further processing.
  • the last step in calibration is verification of the tool symmetry and immunity to axial currents.
  • the overall tool symmetry assumes that the same array reads the same values of the "ground” or environmental conductivity while its measurement direction points to ground or from the ground. For these purposes the tool is rotated around its longitudinal axis on 180°. Absence of such a "direction sensitivity" would indicate normal tool functioning and ensure respective symmetry while operating in the well bore.
  • a modified BCS test may be run with the short removed in the feed-through.
  • connecting and disconnecting the BCS to the tool should result in absolute minimal difference in readings that would indicate for proper operation in the well without formation-dependable offset in the tool data.
  • This modified BCS test could be run as described, or, to reduce calibration time, performed right after the transfer coefficient is determined.
  • FIG. 5 one arrangement of the alignment loop is discussed. Shown therein is an alignment loop 501 surrounding an array characterized by the transmitter coil 504 directed along an X direction (T x ) and the receiver coil 508 directed along the X direction (R x ). Bucking coil B x 506 is also shown.
  • This array is "denoted as XX, using a nomenclature in which the first letter signifies the orientation direction of the transmitter coil and the last letter signifies the orientation direction of the receiver coil. This nomenclature is generally used herein.
  • the XX and YY arrays in the multi-component tool are ideally aligned at 90° from each other.
  • the alignment measuring method of the present invention is based on analyzing the output of the cross- component system when the tool is rotated inside of an alignment loop.
  • the alignment loop 501 is a stationary loop, lying so that the longitudinal axis of the loop and the longitudinal axis of the well-logging tool are substantially aligned. Its dimensions are such as to obtain substantial inductive coupling with the transmitter as well as with the receiver of both XX and YY arrays.
  • the long "box" calibrator of FIG. 4 is used to performed calibration of the horizontal arrays. A detailed analysis of the signals is given later in this document.
  • FIG. 6 illustrates a loop alignment assembly usable for aligning ZZ arrays in a testing device.
  • Transmitter TZ 601, bucking coil BZ 603 and receiver RZ 605 are disposed along the feed-through pipe 615 and have a common longitudinal axis.
  • Alignment loop 610 is substantially coaxial with receiver RZ 605 and substantially centered on RZ.
  • FIG. 7 illustrates an embodiment for calibration of an XY array using a calibration box.
  • Transmitter 701 and bucking coil 703 are disposed along the feed-through pipe oriented to produce a magnetic moment in an X- direction.
  • Receiver 705 is disposed along the same feed-through pipe having an orientation so as to receive components of a magnetic moment in a is disposed along the same feed-through pipe having an orientation so as to receive components of a magnetic moment in Y - direction.
  • the alignment box 710 is disposed at an angle of 45° so as to be oriented halfway between the X-direction and the Y-direction.
  • FIG. 8 illustrated an alternate embodiment for aligning an XY array.
  • Alignment box 815 is located at the TX 801, and alignment box 810 is positioned at the RXY cross- component receiver 805. Both alignment boxes are oriented along the same direction as their respective transmitter/receiver.
  • a wire 820 electrically couples alignment box 810 and alignment box 815. (in this configuration box 815 receives signal from transmitter coil, the voltage induced across its winding produces current flowing through winding of both boxes and load impedance. While going though winding of 810 this current generates filed that is picked up by cross-component receiver)
  • FIG. 9 illustrates an assembly for orienting of the XZ cross-component array.
  • Transmitter TX 901 and bucking coil BX 903 are disposed along the feed-through pipe oriented so as to produce a magnetic moment along an X-direction.
  • the receiver RZ 905 is disposed along the feed-through pipe and oriented so as to be receptive to Z-components of magnetic moments.
  • the alignment box 920 can be positioned centrally between main X-transmitter 901 and Z-cross-component receiver 905 and tilted 45° with respect to the tool longitudinal axis 910.
  • the assembly of FIG. 8 displays small signals during XZ array calibration. This signal tends to display a high sensitivity to the angle.
  • FIG. 10 illustrates an alternate embodiment for aligning the XZ cross-component array.
  • Transmitter TX 1001 and bucking coil BX 1003 are disposed along the feed-through pipe oriented so as to produce a magnetic moment along an X-direct ⁇ on.
  • the receiver RZ 1005 is disposed along the feed-through pipe and oriented so as to be receptive to Z-components of magnetic moments.
  • Alignment box 1010 is centered on transmitter TX 1001, and alignment loop 1015 is coaxial with receiver RZ 1005.
  • a wire 1020 electrically couples alignment box 1010 and alignment loop 1015.
  • calibration using two alignment devices displays a large signal for the XZ array calibration.
  • the alignment box for establishing the coil orientation.
  • the XY or YX response obtained by rotating the tool inside of the alignment loop has a zero-crossing each time that either a transmitter or a receiver coil is perpendicular to the plane of the loop.
  • Whichever coil (transmitter or receiver) is substantially aligned with the loop (enclosed in the same plane) experiences a maximum coupling with the alignment loop.
  • the coupling response between them undergoes a slow change corresponding to the variation.
  • the non-aligned coil experiences a minimum coupling with the alignment loop.
  • the coupling When the position of the non-aligned coil is varied around this point of minimal coupling, the coupling experiences an abrupt change.
  • the coupling becomes zero when the non-aligned coil achieves perpendicularity with the alignment loop.
  • a practitioner in the art would recognize that the zero-crossings of the coupling response are significantly affected by the coil that is at right angle to the alignment loop, regardless of whether the perpendicular coil is a receiver or a transmitter.
  • the substantially aligned coil plays little or no role in the production of a zero-crossing. The angle between successive zero crossings thereby represents an alignment angle between the two related coils.
  • Eqn. (4) illustrates that there are two cycles of variation for each cycle of tool rotation.
  • the angle between successive zero-crossings represents the alignment angle among the cross component coils.
  • An intuitive graphical approach can therefore be used to measure the misalignment angle between transmitter and receiver.
  • the last expression in eqn. (8) indicates that a graphical representation of the coupling response of the misaligned cross component system resembles a sinusoidal function.
  • the period of this sinusoid equals 180° and has offsets on both the abscissa and the ordinate.
  • the offset on the abscissa is ⁇
  • the offset on the ordinate is (K/2)sin( ⁇ ).
  • the coefficient B obtained with such fitting represents the misalignment angle.
  • the cross component response can thus be fit to this curve.
  • Table 2 shows the effects of misalignment in the vertical direction. A misalignment exceeding 5/16" produces an error greater than 0.22%. Thus vertical misalignment has a greater effect on induction response than horizontal misalignment.
  • the transmitter coil of one array is moved in the direction normal to the ground. This coil movement is performed until an absolute minimum in the coupling response is determined.
  • the transmitter coil frame is fixed inside the mandrel.
  • the tool is rotated on its axis and a similar procedure is performed with the other horizontal array.
  • similar tuning can be developed for an instrument having a plurality of transverse and tilted arrays.
  • the tool isolation short is removed and mandrel is covered with the non-conductive pressure sleeve to protect induction coils from being directly exposed to borehole fluids.
  • Calibration of a transfer coefficient is performed once the instrument is inserted inside the calibrator in the low conductive calibration environment.
  • a magnetic load is introduced suitable for calibrating array, so that its signal readings are identical to the values to be read while logging a homogeneous formation.
  • the magnetic load is introduced using the above-referenced calibrator using known electromagnetic parameters and coupling parameters.
  • the tool loading can be achieved by connecting selected impedance to the terminal of a normally-open calibrator loop.
  • the open loop represents an infinitely resistive formation.
  • the closed loop represents an almost infinitely conductive formation (limited only by internal impedance of the wires of the calibrator loop). Therefore, a calibration loop load can be chosen effectively representing a given formation conductivity values.
  • Implicit in the control and processing of the data is the use of a computer program on a suitable machine readable medium that enables the processor to perform the control and processing.
  • the machine readable medium may include ROMs 5 EPROMs, EEPROMs, Flash Memories and Optical disks.

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Abstract

Pour effectuer l'étalonnage des groupes de bobines dans un appareil de diagraphie d'induction à plusieurs composants, on positionne l'appareil horizontalement au-dessus du sol. Les corps supérieur et inférieur de l'appareil sont raccordés par un simulateur de conductivité dans le trou de forage qui a une résistance comparable à celle d'un trou de forage. Pour effectuer le positionnement axial et radial des bobines émettrices, on surveille les sorties au niveau des bobines réceptrices pour obtenir un minimum.
PCT/US2007/001321 2006-01-26 2007-01-19 Vérification par simulateur de conductivité dans un trou de forage et équilibrage des bobines transversales WO2007089438A2 (fr)

Priority Applications (4)

Application Number Priority Date Filing Date Title
CA002640705A CA2640705A1 (fr) 2006-01-26 2007-01-19 Verification par simulateur de conductivite dans un trou de forage et equilibrage des bobines transversales
GB0813803A GB2457324B (en) 2006-01-26 2007-01-19 Borehole conductivity simulator verification and transverse coil balancing
EA200801744A EA014403B1 (ru) 2006-01-26 2007-01-19 Способ проверки имитатором скважинной удельной проводимости и балансировки поперечных катушек
BRPI0707316-0A BRPI0707316A2 (pt) 2006-01-26 2007-01-19 verificação de simulador de condutividade de furo de sondagem e equilìbrio de bobina transversa

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US11/340,785 US7319331B2 (en) 2004-05-07 2006-01-26 Two loop calibrator
US11/340,785 2006-01-26
US11/371,052 US7205770B2 (en) 2004-05-07 2006-03-08 Borehole conductivity simulator verification and transverse coil balancing
US11/371,052 2006-03-08

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WO2007089438A2 true WO2007089438A2 (fr) 2007-08-09
WO2007089438A3 WO2007089438A3 (fr) 2008-04-24

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040220741A1 (en) * 2003-04-29 2004-11-04 Pathfinder Energy Services, Inc. Adjustment for frequency dispersion effects in electromagnetic logging data
US20050143920A1 (en) * 2003-12-12 2005-06-30 Barber Thomas D. Method for determining sonde error for an induction or propagation tool with transverse or triaxial arrays

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040220741A1 (en) * 2003-04-29 2004-11-04 Pathfinder Energy Services, Inc. Adjustment for frequency dispersion effects in electromagnetic logging data
US20050143920A1 (en) * 2003-12-12 2005-06-30 Barber Thomas D. Method for determining sonde error for an induction or propagation tool with transverse or triaxial arrays

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