WO1995024662A1 - Instrument de diagraphie par induction - Google Patents

Instrument de diagraphie par induction Download PDF

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Publication number
WO1995024662A1
WO1995024662A1 PCT/GB1995/000494 GB9500494W WO9524662A1 WO 1995024662 A1 WO1995024662 A1 WO 1995024662A1 GB 9500494 W GB9500494 W GB 9500494W WO 9524662 A1 WO9524662 A1 WO 9524662A1
Authority
WO
WIPO (PCT)
Prior art keywords
former
logging instrument
coils
transmitter
induction logging
Prior art date
Application number
PCT/GB1995/000494
Other languages
English (en)
Inventor
James Roger Samworth
Michel Charles Spencer
Original Assignee
Bpb Industries Plc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Bpb Industries Plc filed Critical Bpb Industries Plc
Publication of WO1995024662A1 publication Critical patent/WO1995024662A1/fr

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Classifications

    • 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

  • This invention relates to induction logging instruments of the type which may be used to measure the resistivity/conductivity of a formation down a borehole either as part of an instrument string or in a measurement while drilling application, and in particular to an induction logging instrument which may make directional resistivity/conductivity measurements circumferentially around a borehole.
  • Figure 1 illustrates this drilling scheme. It shows a borehole 2 drilled through cap rock 4 which retains oil in an oil reservoir 6. When the borehole reaches the oil reservoir it deviates by 90° and forms a horizontal portion 8. As illustrated, a mobile wireline logging station 10 may lower instrumentation such as an induction logging instrument 12 into the borehole via a cable 14.
  • the induction logging instrument 12 (induction sonde) is used to measure the formation resistivity/conductivity in the oil reservoir.
  • a conventional induction logging instrument operates by having at least one transmitter coil wound around a former and one or more receiver coils longitudinally spaced from the transmitter coil along the former. Energisation of the transmitter coil causes ground currents to flow in a loop around the instrument. The magnetic field associated with these ground currents induces current in the receiver coils, the magnitude of which is dependent on the formation resistivity/conductivity.
  • EP-A-0475715 there is proposed an instrument for making directional measurements around a borehole.
  • this transmitter coils are placed asymmetrically around a conductive former in slots formed in the former.
  • the positioning of the transmitter coils results in nulls being formed in the primary magnetic field formed by the transmitter coil.
  • Receiver coils are placed at these nulls thereby eliminating the need for any cancellation coil to eliminate the primary field effects in receiver coils.
  • a fundamental problem associated with an instrument of this type is that the electrical properties of the conductive former change with temperature in a borehole. This results in changes in the primary field and changes in the positions of directional nulls. Thus spurious signals are generated at receiver coils and compensation for these is difficult.
  • the former on which the coils are wound may be conductive or non-conductive.
  • the former is screened from the field generated by the transmitter coil by a layer of magnetic core material on which the coil is wound.
  • a non-conductive former is used a directional instrument of the type described in EP-A-0475715 cannot be used because no nulls will be formed for receiver coil placement.
  • Preferred embodiments of the present invention provide an induction logging instrument which can selectively measure resistivity/conductivity, in particular radial directions.
  • the instrument is preferably constructed so that it can measure the resistivity of the surrounding formation in a plurality of segments around the circumference of the logging instrument with either a conductive or a non-conductive former.
  • Figure 1 shows the borehole discussed above
  • Figures 2a and 2b schematically show the generation of ground currents by a current flowing in a coil
  • Figure 3 schematically shows a ground current generated by a conventional induction logging instrument
  • Figure 4 schematically shows a ground current generated by a logging instrument embodying the present invention
  • Figure 5 shows a schematic cross-section through a logging instrument embodying the present invention
  • Figure 6 shows a side view of one of the coil systems of the instrument of Figure 5;
  • Figures 7a and 7b schematically show in side and plan cross-sections the field patterns generated by an embodiment of the invention
  • Figure 8 shows an instrument embodying the invention with multiple receiver and transmitter coils
  • Figure 9 shows the instrument of figure 8 with the addition of a cancellation coil system
  • Figure 10 shows an instrument embodying the invention with a single transmitter coil and multiple receiver coils
  • Figure 11 shows the instrument of Figure 10 with the addition of a cancellation coil
  • Figure 12 shows a further embodiment of the invention.
  • the mechanism by which ground currents are induced by an induction logging instrument is illustrated with reference to Figures 2a and 2b.
  • Figure 2a shows a transmitter coil 20 through which an AC current is passed. This generates a varying magnetic field which penetrates into any surrounding conductive medium. The portion of the magnetic field is illustrated in cross-section in Figure 2a as lines of magnetic flux 22.
  • each line of magnetic flux has a current element 24 circulating round it.
  • a network of circulating current cells is formed.
  • the network for the lines of flux in Figure 2a is shown diagrammatically in Figure 2b. It can be seen that at the boundaries of each cell 24 the currents cancel. Thus there is current generated around the outside of the field and this is illustrated by the thick black line 26. This is the current that flows in the medium penetrated by the magnetic field.
  • FIG 3 shows the ground current 26 which is generated around the transmitter coil of a conventional induction logging instrument 12.
  • a field and current pattern as illustrated in Figure 4 is required.
  • the lines of magnetic flux 22 which are produced have been constrained to be present predominantly on one side of the logging instrument 12 thus producing a non-symmetrical ground current loop 28 which also is predominantly on the same side of the induction logging instrument. This ground current will be detected by receiver coils on the instrument.
  • the induction logging instrument comprises a non-magnetic, non- conductive core 30. Carried on the outside of this core 30 are six circumferentially-spaced coils 32 each wound on magnetically-permeable cores 34.
  • the core 30 Carried on the outside of this core 30 are six circumferentially-spaced coils 32 each wound on magnetically-permeable cores 34.
  • each one is distorted from the generally circular shape to lie against the outer surface of the core 30 over a portion of its circumference with the axis of the coil being substantially parallel to the axis of the core.
  • there are six coils circumferentially spaced around the core there are six coils circumferentially spaced around the core. Clearly more or fewer coils could be used.
  • FIG. 7a the lines of magnetic flux 42 generated as a result of activation of coil 40 carried on the logging instrument extend outwardly from the logging instrument and penetrate the surrounding formation.
  • the lines of flux 44 are generated on the opposite side of the coil.
  • the high magnetic permeability of the cores in the other coils around the instrument provide a line of weakest resistance through which these lines of flux pass. Thus virtually no magnetic flux is generated on the other sides of the instrument.
  • each of the six coils is activated in turn in response to signals from the surface logging station, six different radial regions of the surrounding formation will have ground current induced in them. These induced currents are detected in the usual manner by the logging station by measuring the currents they themselves induce in a corresponding system of receiver coils.
  • the whole logging instrument is illustrated with reference to Figure 8 in which six transmitter coils 40 are wound on a non-magnetic core 48. Longitudinally spaced on the core from the transmitter is a geometrically-similar arrangement of receiver coils 50. When one of the transmitter coils is activated, a current will be induced in at least one of the receiver coils. The coil of most interest is that on the same arc of the instrument as the activated transmitter coil. However, the results from the other coils will enable fine tuning of results to be made.
  • the current induced in the receiver coil by the ground current flowing in the formation can be masked by the very large current directly induced by the transmitter coil.
  • Various measures may be employed to reduce the effect of the directly induced signal thus making it possible to measure more accurately the ground currents induced in the formation. These measures are: l. Pulse or transmit a short burst of current from the transmitter coil. The directly coupled signal disappears as soon as the transmitter pulse ceases. However, the ground current flows for a short time after this. Thus, if the current induced in the receiver coil is measured after the transmitted pulse stops, the effect of the directly induced current is removed and all the receiver coil current is induced by current flowing in the formation.
  • phase sensitive detector Use a phase sensitive detector.
  • the directly induced signal is 90° out of phase with the transmitter current but the voltages induced by the ground current in the receiver coil are 180° out of phase with the transmitter current.
  • Using a phase sensitive detector to isolate the two out of phase signals induced in the receiver coil will allow them to be measured independently.
  • FIG 10. An alternative embodiment of the logging instrument is illustrated in Figure 10.
  • the transmitter comprises a single coil symmetrically wound around the logging instrument. The whole of the formation around the circumference of the tool is therefore excited by the transmitter coil.
  • the receiver comprises a plurality of coils arranged around the circumference of the instrument such as are illustrated in Figures 5 and 6. Thus only a small region of the formation is interrogated by the receiver and this gives the total measurement the directional properties required.
  • a modification to Figure 10 is shown in Figure 11. In this, a cancellation coil 56 is provided on the instrument for connection with the receiver coils to cancel the directly induced currents.
  • FIGS 12a and 12b A further embodiment of the invention is illustrated in Figures 12a and 12b which uses a system as described in our European patent application No. 94302726.8 This enables measurements to be made in a measurement whilst drilling application where the logging instrument is provided on a coiled tubing system adjacent to a down hole motor and drilling bit.
  • the instrument is formed on a strong core 60 which is non-magnetic and may be of metal.
  • a screen made up of a plurality of elongate sections 62 of magnetically-permeable core material. The purpose of these is to shield the coils surrounding the tube from the drilling mud flowing through the instrument to drive the down hole motor and which may be conductive.
  • each wound round elongate sections 64 of magnetically-permeable core material are coils 32 of the type shown in Figure 5, each wound round elongate sections 64 of magnetically-permeable core material.
  • a field generated in the formation is similar to that illustrated in Figure 7a.
  • lines of flux within the instrument do not pass through the central core and the drilling mud flowing therethrough because of the presence of the shield 62. Instead the lines of flux pass through the magnetically-permeable core material 62.
  • the lines 44 as shown in Figure 7a would in fact only be present on the side of the instrument adjacent to the activated coil and no current would be induced in the coil as a result of conductivity in the drilling mud.
  • This embodiment may be modified to correspond to that of Figure 10 which has only a single transmitter coil. To do this the transmitter coil would be wound directly around the screen of magnetic core material thereby shielding the coils from drilling mud flowing through the tube.
  • the invention may be used in a measurement whilst drilling application.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Remote Sensing (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Electromagnetism (AREA)
  • Environmental & Geological Engineering (AREA)
  • Geology (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Geophysics (AREA)
  • Geophysics And Detection Of Objects (AREA)

Abstract

Un instrument de diagraphie par induction, qui permet d'effectuer des mesures directionnelles de conductivité/résistivité, comprend au moins un bobinage d'émission (32) enroulée sur un noyau magnétique (34) et prenant appui sur un gabarit (30) d'enroulement allongé. Plusieurs bobines de réception (50) sont espacées longitudinalement du bobinage émetteur et réagissent aux courants générés par la bobine d'émission dans le sol.
PCT/GB1995/000494 1994-03-07 1995-03-07 Instrument de diagraphie par induction WO1995024662A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9404381A GB9404381D0 (en) 1994-03-07 1994-03-07 Induction logging instrument
GB9404381.7 1994-03-07

Publications (1)

Publication Number Publication Date
WO1995024662A1 true WO1995024662A1 (fr) 1995-09-14

Family

ID=10751429

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1995/000494 WO1995024662A1 (fr) 1994-03-07 1995-03-07 Instrument de diagraphie par induction

Country Status (2)

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GB (2) GB9404381D0 (fr)
WO (1) WO1995024662A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106246163A (zh) * 2016-08-31 2016-12-21 中国科学院地质与地球物理研究所 近钻头动态井斜测量方法及装置

Families Citing this family (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6100696A (en) * 1998-01-09 2000-08-08 Sinclair; Paul L. Method and apparatus for directional measurement of subsurface electrical properties
US6377050B1 (en) 1999-09-14 2002-04-23 Computalog Usa, Inc. LWD resistivity device with inner transmitters and outer receivers, and azimuthal sensitivity
US6509738B1 (en) * 2000-07-14 2003-01-21 Schlumberger Technology Corporation Electromagnetic induction well logging instrument having azimuthally sensitive response
EP1421413A2 (fr) * 2001-08-03 2004-05-26 Baker Hughes Incorporated Procede et appareil destines a un systeme de mesure par instrument a induction multi-composant
US6677756B2 (en) 2001-08-03 2004-01-13 Baker Hughes Incorporated Multi-component induction instrument
US7463035B2 (en) 2002-03-04 2008-12-09 Baker Hughes Incorporated Method and apparatus for the use of multicomponent induction tool for geosteering and formation resistivity data interpretation in horizontal wells
US7385400B2 (en) 2004-03-01 2008-06-10 Pathfinder Energy Services, Inc. Azimuthally sensitive receiver array for an electromagnetic measurement tool
CA2499045A1 (fr) 2004-03-01 2005-09-01 Pathfinder Energy Services, Inc. Reseau de recepteurs a sensibilite azimutale pour outil de mesure electromagnetique
US7719282B2 (en) 2004-04-14 2010-05-18 Baker Hughes Incorporated Method and apparatus for mulit-component induction instrument measuring system for geosteering and formation resistivity data interpretation in horizontal, vertical and deviated wells
GB2492992B (en) 2011-07-19 2017-04-26 Reeves Wireline Tech Ltd A method of establishing formation resistivity
US10830039B2 (en) * 2014-04-03 2020-11-10 Baker Hughes Holdings Llc Downhole tri-axial induction electromagnetic tool

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4264862A (en) * 1979-08-20 1981-04-28 The United States Of America As Represented By The United States Department Of Energy Induction logging device with a pair of mutually perpendicular bucking coils
US4737719A (en) * 1986-05-21 1988-04-12 Halliburton Company Coherent detection system for use in induction well logging apparatus
US4980643A (en) * 1989-09-28 1990-12-25 Halliburton Logging Services, Inc. Induction logging and apparatus utilizing skew signal measurements in dipping beds
US5045795A (en) * 1990-07-10 1991-09-03 Halliburton Logging Services Inc. Azimuthally oriented coil array for MWD resistivity logging
EP0475715A2 (fr) * 1990-09-10 1992-03-18 Baker Hughes Incorporated Mesure de conductivité pour puits
JPH05142359A (ja) * 1991-11-22 1993-06-08 Reideitsuku:Kk 鋼製ロツドによる地中情報収集方式

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4302723A (en) * 1979-06-15 1981-11-24 Schlumberger Technology Corporation Apparatus and method for determining dip and/or anisotropy of formations surrounding a borehole
US5095272A (en) * 1990-03-23 1992-03-10 Halliburton Logging Services, Inc. Methods for determining formation dip and strike using high frequency phase shift

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4264862A (en) * 1979-08-20 1981-04-28 The United States Of America As Represented By The United States Department Of Energy Induction logging device with a pair of mutually perpendicular bucking coils
US4737719A (en) * 1986-05-21 1988-04-12 Halliburton Company Coherent detection system for use in induction well logging apparatus
US4980643A (en) * 1989-09-28 1990-12-25 Halliburton Logging Services, Inc. Induction logging and apparatus utilizing skew signal measurements in dipping beds
US5045795A (en) * 1990-07-10 1991-09-03 Halliburton Logging Services Inc. Azimuthally oriented coil array for MWD resistivity logging
EP0475715A2 (fr) * 1990-09-10 1992-03-18 Baker Hughes Incorporated Mesure de conductivité pour puits
JPH05142359A (ja) * 1991-11-22 1993-06-08 Reideitsuku:Kk 鋼製ロツドによる地中情報収集方式

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 017, no. 522 (P - 1616) 20 September 1993 (1993-09-20) *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106246163A (zh) * 2016-08-31 2016-12-21 中国科学院地质与地球物理研究所 近钻头动态井斜测量方法及装置

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Publication number Publication date
GB9404381D0 (en) 1994-04-20
GB9504482D0 (en) 1995-05-03
GB2287324A (en) 1995-09-13

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