A kind of nearly drill bit resistivity measurement while drilling method and device
Technical field
The present invention relates to drilling well and well logging field, particularly relate to boring the resistivity logging technology, is a kind of nearly drill bit resistivity measurement while drilling method and device specifically.
Background technology
So-called resistivity logging is exactly the measuring well resistivity of exclosure layer near the eyes, and it is applied to the evaluation to the stratum usually.Such as, porous stratum generally has higher resistivity, and it can indicate the existence of hydrocarbon; When porous stratum showed lower resistivity, general expression had the existence of saturation water.In cable well logging was arranged, measurement was carried out after trip-out, at the bottom of the logger lower going-into-well that it connects cable and measure in the last process of carrying.The resistivity logging technology that various ways (such as adopting electrode or coil) arranged now gets final product the measurement of compound electrode realization to electric current and/or current potential, and derives formation resistivity thus on ground.For instance, configurable a plurality of button electrodes push against this pole plate on the borehole wall during measurement on a pole plate.Can obtain the azimuthal resistivity measured value by these electrodes, simultaneously by focusing technology make measurement fully lateral expansion enter the stratum, thereby the resistivity information with higher vertical resolution is provided.
But there is the maximum defective of cable well logging just to be its non real-time property.As mentioned above, have the cable well logging to carry out after trip-out, at this moment, bored out several hours even the longer time on the stratum of wellbore.Because the intrusion of drilling fluid makes the formation resistivity of wellbore that change take place.Such as, when using low-resistivity drilling fluid (such as salt-water drilling fluid) to bore the porous stratum of opening high resistivity, because the intrusion of drilling fluid reduces the formation resistivity of wellbore, it might make according to the explanation that has cable well logging result to carry out can miss this section reservoir.This is boring easier generation under the situation of meeting thin reservoir.
In directional well, horizontal well drilling, institute's drilling well eye is exposed in the reservoir to greatest extent, then will improve recovery ratio greatly.Although being arranged, the cable well logging can in boring the thick reservoir of chance, use time-consuming non-worker; And approach reservoir in case bore chance, then there is the cable well logging powerless.Because this needs to detect in real time near the formation resistivity (also needing other geology and engineering parameter certainly) of drill bit.
Therefore be necessary Application and Development in technology and method, but the technology that adopts might not be applied in the well logging during in the cable well logging is arranged with the brill resistivity measurement.Environment in the well is very abominable, even also be so in the cable well logging is arranged, but near the environment the shaft bottom is then more abominable concerning measurement mechanism in drilling process.In well logging during, measurement mechanism only just allows to be assemblied on the drill collar under the prerequisite of not destroying the whole system mechanical integrity.Simultaneously, measuring method also need be provided with one section zone that is made of insulation materials fully on the drill collar surface, and it is very big that this implements difficulty.On measurement structure, when drilling tool when continuously rotation or slide is crept into, drill collar closely contacts with the stepout well eye, thereby is accompanied by violent wearing and tearing and powerful STRESS VARIATION.
Summary of the invention
The objective of the invention is to, a kind of nearly drill bit resistivity measurement while drilling method and device are provided.Be used for side direction resistivity, drill bit resistivity and azimuthal resistivity are measured, obtain the down-hole formation more information by measuring; As improved the side direction resistivity information of vertical resolution, the drill bit resistivity information that can detect (comprising drill bit the place ahead) formation resistivity around the drill bit and azimuthal resistivity information of many investigation depths etc., thereby provide more formation resistivity metrical information.
Technical scheme of the present invention is:
A kind of nearly drill bit resistivity measurement while drilling method, it is characterized in that, foot carry drill bit, can nearly bit location that in well, rotate and/or slide up and down, column conducting metal body on mounting strap magnetic core transmitting coil, level induces electric current thereby this band magnetic core transmitting coil elementary encouraged secondarily by an alternating voltage;
Transmit described electric current the galvanic circle that the stratum that utilizes described conducting metal body and close on constitutes;
Electrode and band magnetic core receiving coil also are installed on described conducting metal body, adopt this electrode and band magnetic core receiving coil measure respectively separately by the signal of telecommunication that described electric current produced, thereby indicate corresponding formation resistivity.
Electrode also is being installed on the described conducting metal body and is being with the magnetic core receiving coil to be meant: a plurality of electrodes and a plurality of band magnetic core receiving coil are being installed on described conducting metal body, measure respectively separately by the signal of telecommunication that described electric current produced, thereby indicate corresponding formation resistivity.
Electrode is being installed also on the described conducting metal body and band magnetic core receiving coil is meant: be installed in an electrode and ring-like band magnetic core receiving coil on the described conducting metal body and place the bottom of described band magnetic core transmitting coil, the signal of telecommunication that they are measured each free described electric current respectively and are produced is to indicate corresponding formation resistivity.
Electrode also is being installed on the described conducting metal body and is being with the magnetic core receiving coil to be meant: three electrodes and two band magnetic core receiving coils are being installed on described conducting metal body, measure respectively separately by the signal of telecommunication that described electric current produced, thereby indicate corresponding formation resistivity.
Method of the present invention may further comprise the steps:
Adopt a ring-like band magnetic core transmitting coil, insert it in insulation materials and be installed near on the drill collar of drill bit, make it induce electric current, current loop comprises the stratum around drill collar and the drill collar;
Adopt two ring-like band magnetic core receiving coils, insert them in the insulation materials and be installed on the drill collar of transmitting coil bottom, realize side direction resistivity and drill bit resistivity measurement;
Adopt three button shape electrodes, insert them in the insulation materials and be installed on the drill collar of transmitting coil bottom, be used for detecting electric current (almost being perpendicular to the axial of drill collar), and this electric current is excited by ring-like transmitting coil from stratum side direction refurn electrode.
Make the vertical height of described three button shape electrodes smaller relatively more favourable to measuring, it makes the formation resistivity measured value of these electrodes have higher vertical resolution and higher investigation depth for this resolution ratio.Can obtain the same azimuthal resistivity information of three different investigation depths by the electric current that detects three electrodes because three electrodes are arranged to straight line and apart from the distance of transmitting coil by near to far away.
Described three electrodes both can be installed on the drill collar, and it is integrated with drill collar also can be installed on the rib of centralizer the back earlier.
The present invention also provides a kind of nearly drill bit resistivity measurement while drilling device, and comprising: microcontroller circuit is characterized in that also comprising: column conducting metal body, band magnetic core transmitting coil, electrode and band magnetic core receiving coil;
Described band magnetic core transmitting coil, electrode and band magnetic core receiving coil are installed on the described column conducting metal body, and link with described microcontroller circuit respectively;
Thereby the elementary of described band magnetic core transmitting coil encouraged secondarily level to induce electric current by an alternating voltage; Transmit described electric current the galvanic circle that the stratum that utilizes described conducting metal body and close on constitutes; Described electrode and band magnetic core receiving coil measure respectively separately by the signal of telecommunication that described electric current produced, this signal of telecommunication is sent into described microcontroller circuit handles, thereby measure corresponding formation resistivity.
Described microcontroller circuit is meant: can measure, control, processing, store information, depositing information be carried out the ground playback and/or be sent to the microcontroller circuit of shaft bottom/ground communications device; Described column conducting metal body is a drill collar.
A plurality of described electrodes and a plurality of described band magnetic core receiving coil can be installed on described column conducting metal body.
For device of the present invention:
Described microcontroller circuit is a single-chip microcomputer;
Described column conducting metal body is a stub boring quickly 101;
Described band magnetic core transmitting coil is a transmitting coil 121;
Described electrode is meant: nearly collecting electrode 141, middle collecting electrode 142, collecting electrode 143 far away;
Described band magnetic core receiving coil is meant: nearly receiving coil 131, receiving coil 133 far away;
Wherein:
Stub boring quickly is equipped with transmitting coil 121, nearly receiving coil 131 and receiving coil 133 far away and nearly collecting electrode 141, middle collecting electrode 142 and collecting electrode 143 far away on 101.
Described transmitting coil 121 is made up of ring-like band magnetic core coil, and it is wound with coil on ring type magnetic core, its with stub boring quickly 101 the axle consistent; The structural similarity of described nearly receiving coil 131 and receiving coil 133 far away and transmitting coil 121.
Described nearly collecting electrode 141, middle collecting electrode 142 and collecting electrode 143 far away are the button shape, and are installed on the centralizer 105.
Be sleeved on stub boring after 122 encapsulation of described transmitting coil 121 usefulness insulation materials quickly on 101, it has sealing ring 109 to be sealed to prevent that liquid from entering ring-like space 106 in two ends up and down, and the lead of transmitting coil is introduced ring-like space 106 by anti-water strand groove;
Be sleeved on stub boring after 132 encapsulation of nearly receiving coil 131 usefulness insulation materials quickly on 101, it has sealing ring to be sealed to prevent that liquid from entering ring-like space in two ends up and down, and the lead of nearly receiving coil is introduced ring-like space by preventing the water strand groove;
Be sleeved on stub boring after receiving coil 133 usefulness insulation materials far away 134 encapsulation quickly on 101, it has sealing ring to be sealed to prevent that liquid from entering ring-like space in two ends up and down, and the lead of nearly receiving coil is introduced ring-like space by preventing the water strand groove.
The function of described receiving coil far away 133 is identical with a current transformer, and the conductive formation around drill collar and the drill collar constitutes the elementary ring type magnetic core that passes through of mutual inductor, and on ring type magnetic core around coil (number of turn is N
F) constitute the secondary of mutual inductor; Two leads of 133 levels of receiving coil far away are introduced testing circuit by anti-water strand groove; A lead of 133 levels of receiving coil far away is connected to the reverse input end of operational amplifier 466, and another root lead of 133 levels of receiving coil far away inserts the non-inverting input of operational amplifier 466, as measuring the ground reference potential, between the output of operational amplifier 466 and reverse input end, insert feedback resistance R
F
The function of described nearly receiving coil 131 is identical with a current transformer, and the conductive formation around drill collar and the drill collar constitutes the elementary ring type magnetic core that passes through of mutual inductor, and on ring type magnetic core around coil (number of turn is N
N) constitute the secondary of mutual inductor; Two leads of nearly 131 levels of receiving coil are introduced testing circuit by anti-water strand groove; A lead of nearly receiving coil secondary 131 is connected to the reverse input end of operational amplifier 463, and another root lead of nearly 131 levels of receiving coil inserts the non-inverting input of operational amplifier 463, as measuring the ground reference potential, between the output of operational amplifier 463 and reverse input end, insert feedback resistance R
N
Described nearly collecting electrode 141, middle collecting electrode 142 and collecting electrode 143 far away are installed on the rib 105 of centralizer and are aligned to straight line, and rib can be straight line or curvilinear structures and have extremely hard surface such as tungsten carbide;
Described centralizer rib 105 is formed from steel and is integrated on the steel cylindrical sleeves, and this sleeve slidably is socketed in stub boring quickly on 101;
Collecting electrode is the button shape, and has the periphery and the close borehole wall of circle (being exactly circular) herein;
The surface of collecting electrode has certain cylinder radian to cooperate the surface configuration of centralizer, perhaps have a plane and this plane a shade below the centralizer surface.
Described collecting electrode (such as 141) is gone up configuration one lead and is introduced testing circuit by anti-water strand groove, and this lead passes through a small-sized ring-like band magnetic core coil 562 backs and stub boring and quickly 101 links to each other.
Described microcontroller circuit comprises: the master-slave mode measurement and control unit that multimicroprocessor and local serial communication bus constitute, described unit comprise a main observing and controlling subelement 300 and a plurality of from observing and controlling subelement i (as 400,500,------);
Described main observing and controlling subelement is carried out TT﹠C task, and by local serial communication bus 319 to respectively sending control command and data and/or reception from respectively from the information of observing and controlling subelement i from observing and controlling subelement i;
Describedly carry out TT﹠C task, and receive the control command and the data of main observing and controlling subelement and carry out corresponding operation and/or corresponding information is sent to main observing and controlling subelement by local serial communication bus 319 from observing and controlling subelement i.
Described serial communication bus comprises: RS-232, SPI, I
2C etc.
Described main observing and controlling subelement comprises: down-hole power monitor 320 and down-hole power controller 325, memory 302, local serial bus interface 315 and local serial communication bus 319 and ground serial bus interface 310 and ground serial communication bus 314, microprocessor 301;
Microprocessor 301 comprises internal storage, clock, timer and input/output interface etc.;
Down-hole power monitor 320 detects the output valve of each power supply, the output current of each battery pack, the ampere-hour of working etc., and exports these detected values to microprocessor 301;
Microprocessor 301 by local serial communication interface 315 and local serial communication bus 319 to respectively sending control command and data from observing and controlling subelement i, and with received respectively from the memory 302 that survey data and the state of observing and controlling subelement i is kept at expansion; When entire measuring device 100 trips out ground, all information that are kept in the memory 302 can be by ground serial communication interface 310 and 314 unloadings of ground serial communication bus to ground-based computer, simultaneously, measurement mechanism 100 also can receive control command and the data that ground-based computer sends by this bus.
Describedly comprise sine-wave generator 420 and power amplifier 425, nearly receiving coil 131 and receiving coil 133 far away, local serial communication bus interface 415 and local serial communication bus 319, microprocessor 401 from observing and controlling subelement 400;
Microprocessor 401 comprises internal storage, clock, timer and input/output interface etc.; Under the control of microprocessor, sine-wave generator 420 can produce the sine wave of different frequency, different amplitudes, and this sine wave carries out inserting transmitting coil 121 to motivate corresponding induced-current after electric current amplifies through power amplifier 425; The electric current that receiving coil 133 far away detects converts correspondent voltage to (referring to Fig. 3, wherein: V by operational amplifier 466
F=-R
F* I
F/ N
F) multiplexer 460 is inserted in the back, and the electric current that nearly receiving coil 131 detects inserts multicircuit switch 460 after converting correspondent voltage (referring to Fig. 3) to by operational amplifier 463;
Under the control of microprocessor 401, this two paths of signals timesharing inserts bandpass filter 450 by multicircuit switch 460, signal behind bandpass filtering inserts variable gain amplifier 445, this signal access wave detector 440 carries out detection and filters into direct current signal through low pass filter 435 subsequently, AD converter 430 is a data signal with analog signal conversion, and output in the microprocessor 401, microprocessor 401 is handled obtaining side direction resistivity above-mentioned and drill bit resistivity measurements these data signals according to predetermined computational methods, and is kept in the memory of microprocessor 401 inside;
When the request that receives autonomous observing and controlling subelement 300 from local serial communication bus 319 sends data command, then corresponding measured value is sent to main observing and controlling subelement 300 by local serial communication interface 415 and local serial communication bus 319.
Describedly comprise from observing and controlling subelement 500: nearly collecting electrode 141, current detection circuit, local serial communication bus interface 515 and local serial communication bus 319, the microprocessor 501 of collecting electrode 142 and collecting electrode 143 far away;
Microprocessor 501 comprises internal storage, clock, timer and input/output interface etc.; Under the control of microprocessor, the electric current that nearly collecting electrode 141 and small-sized ring-like band magnetic core coil 562 detect converts correspondent voltage to (referring to Fig. 4, wherein: V by operational amplifier 563
Bn=-R
Bn* I
Bn/ N
Bn) back access multiplexer 560, and the electric current that middle collecting electrode 142 and small-sized ring-like band magnetic core coil 565 detect converts correspondent voltage (referring to Fig. 4) back access multiplexer 560 to by operational amplifier 566, and the electric current that collecting electrode 143 simultaneously far away and small-sized ring-like band magnetic core coil 568 detect converts correspondent voltage (referring to Fig. 4) back access multiplexer 560 to by operational amplifier 569;
Under the control of microprocessor 501, this three road signals timesharing inserts bandpass filter 550 by multicircuit switch 560, signal behind bandpass filtering inserts variable gain amplifier 545, this signal access wave detector 540 carries out detection and filters into direct current signal through low pass filter 535 subsequently, AD converter 530 is a data signal with analog signal conversion, and outputs in the microprocessor 501;
Microprocessor 501 according to predetermined computational methods to these data signals handle with obtain above-mentioned shallow, in, dark azimuthal resistivity measured value, and be kept in the memory of microprocessor 501 inside;
Send data command when local serial communication bus 319 receives the request of autonomous observing and controlling subelement 300, then corresponding measured value is sent to main observing and controlling subelement 300 by local serial communication interface 515 and local serial communication bus 319.
If comprise mud pulse generator and supporting equipment in the drill collar 25, then the metrical information of preserving in the memory 302 of main observing and controlling subelement 300 can be sent to this down-hole/ground communications device, and be transferred to ground by this device, after the ground-based computer system receive to handle, can be near ground obtains current downhole drill bit in real time a plurality of resistivity measurements on stratum.
Meaning of the present invention is, by a kind of nearly drill bit resistivity measurement while drilling method and device are provided, is used for side direction resistivity, drill bit resistivity and azimuthal resistivity are measured, and obtains the down-hole formation more information by measuring; For example improved the side direction resistivity information of vertical resolution, the drill bit resistivity information that can detect (comprising drill bit the place ahead) formation resistivity around the drill bit and azimuthal resistivity information of many investigation depths etc., thereby more formation resistivity metrical information is provided.
Description of drawings
Fig. 1 is a kind of near drill bit resistivity measurement while drilling device that proposes according to an example of the present invention and hangs on schematic diagram in the well;
Fig. 2 is the sectional view of nearly drill bit resistivity measurement while drilling device of the present invention;
Fig. 3 is the measuring circuit schematic diagram of ring-like band magnetic core receiving coil far away;
Fig. 4 is the measuring circuit schematic diagram of collecting electrode;
Fig. 5 is that ring-like band magnetic core transmitting coil is energized the current distributing figure that the back is produced;
Fig. 6 is measurement and the control block diagram that multimicroprocessor and local serial communication bus constitute;
Fig. 7 is that the basic circuit of main observing and controlling subelement constitutes block diagram;
Fig. 8 is the basic circuit formation block diagram from observing and controlling subelement 1;
Fig. 9 is the basic circuit formation block diagram from observing and controlling subelement 2.
The specific embodiment
For example understand below in conjunction with description of drawings the specific embodiment of the present invention: Fig. 1 according to a kind of near drill bit resistivity measurement while drilling device that an example of the present invention proposed and the situation of carrying out measurement while drilling in the shaft bottom.[except specializing, the measurement while drilling of herein mentioning (or being referred to as well logging during) all refers to: be hung with drill bit and some drilling tools in well, the measurement of being carried out when creeping into, suspending and/or making a trip.] drilling tool 20 hung among the well 11 by the rig on the ground 10 (not show), its underpart has drill bit 23, and can be rotated by the related device on the rig and/or move up and down.10 centers that enter drilling tool 20 flow downward drilling fluid on ground, flow out drilling tool 20 and upwards flow from annular space 21 (being formed zone between the borehole wall of drilling tool 20 outer walls and well 11) through the nozzle of drill bit 23, the rock core fragment that drilling fluid lubricating drill bit 23 and drilling tool 20 also finally carry the stratum 24 that is cut returns ground 10.A kind of MTR that has curved shell or offset sub can be used as directional drill tool (not showing) and is selected for use.
What represent near drill bit 23, with numeral 100 promptly is the nearly drill bit resistivity measurement while drilling device that proposes according to an example of the present invention, and its inside comprises can measure, controls, processing, store information, depositing information be carried out the ground playback and/or be sent to the instrument of shaft bottom/ground communications device (not having demonstration).[so-called refer to promptly that near drill bit distance from drill bit is within several drill collar length herein.] in this example, one or more drill collars 25 (not having complete demonstration) are serially connected on the measurement mechanism 100, they may be drill collars purely, also may be other measurement and/or the communication function of drill collar to realize no longer describing herein that measurement and/or communication device are housed.Be serially connected with stub boring quickly 22 between measurement mechanism 100 and drill bit 23, its length is predetermined according to the structural parameters of measurement mechanism and drill bit length.Measurement mechanism 100 comprises microcontroller circuit usually, and in this example, then adopt SCM system (comprising corresponding memory, clock and timer circuit and interface circuit etc.), it can be realized top desired measurement, control, processing, store information and depositing information be carried out the ground playback and/or be sent to the function of shaft bottom/ground communications device.Battery and/or downhole generator can be this device electric power are provided.
Fig. 2 is detailed has described to be installed in the stub boring structure of the nearly drill bit resistivity measurement while drilling device 100 on 101 quickly.Stub boring quickly is equipped with transmitting coil 121, nearly receiving coil 131 and receiving coil 133 far away and collecting electrode 141,142 and 143 on 101.In this example, transmitting coil 121 is made up of ring-like band magnetic core coil, and it is wound with coil on ring type magnetic core, and its axle with drill collar 101 is consistent.Magnetic core can be circle or square-section, also can adopt other cross section certainly.The structural similarity of nearly receiving coil 131 and receiving coil 133 far away and transmitting coil 121.Collecting electrode 141,142 and 143 is the button shape, preferably is installed on the centralizer 105.All sleeves and centralizer are fixed on stub boring quickly on 101 by locking nut 107 at last, and all have sealing ring 109 to enter ring-like space 106 to prevent drilling fluid between all sleeves and centralizer.The drilling fluid passage is at stub boring 101 102 places, center quickly.Most electronic units (as battery pack and circuit board etc.) be placed in stub boring quickly 101 and the formed ring-like space 106 of a plurality of sleeve in.
Transmitting coil 121 is made up of ring-like band magnetic core coil, and it is wound with coil on ring type magnetic core, its with stub boring quickly 101 the axle consistent.Magnetic core can be circle or square-section, also can adopt other cross section certainly.Be sleeved on stub boring after the encapsulation of transmitting coil 121 usefulness insulation materials (such as fluorubber) 122 quickly on 101, it has sealing ring 109 to be sealed to prevent that liquid from entering ring-like space 106 in two ends up and down, and the lead of transmitting coil is introduced ring-like space 106 by anti-water strand groove (not showing).The structure of nearly receiving coil 131 and receiving coil 133 far away is same as described above, and its insulation materials is for being respectively 132 and 134.
For receiving coil 133 far away, it is equivalent to a current transformer, and the conductive formation around drill collar and the drill collar constitutes the elementary ring type magnetic core that passes through of mutual inductor, and on ring type magnetic core around coil (number of turn is N
F) constitute the secondary of mutual inductor.As mentioned above, two leads of 133 levels of receiving coil far away are introduced testing circuit by anti-water strand groove.As shown in Figure 3, a lead of 133 levels of receiving coil far away is connected to the reverse input end of operational amplifier 466, and another root lead of 133 levels of receiving coil far away inserts the non-inverting input of operational amplifier 466, as measuring the ground reference potential, between the output of operational amplifier 466 and reverse input end, insert feedback resistance R
FThe gain of operational amplifier 466 is very high, oppositely and the voltage difference V between non-inverting input
iVery little, almost nil, and the input impedance of operational amplifier 466 is very high, thereby do not have electric current to flow into any one input basically.Therefore, be I if pass through the electric current of ring type magnetic core
F, then the electric current of inducting in receiving coil far away is secondary is I
F/ N
F, electric current I
F/ N
FFeedback resistance R flows through
FThereby, make the output voltage of operational amplifier 466 be-R
F* I
F/ N
FBecause measured current I
FLeave drill collar 101 behind the receiving coil 133 far away and drill bit 23 enters the electric current (referring to Fig. 5) on stratum for passing through, thereby be a kind of tolerance receiving coil 133 far away and 23 electrical resistivity of earth layer around of drill bit.
All structure and the measuring method with receiving coil 133 far away is identical with measuring method for the structure of nearly receiving coil 131, so can be equally referring to Fig. 3.Different is that what to measure in this example is that nearly receiving coil 131 is measured electric current I
NMeasure electric current I with receiving coil 133 far away
FDifference Δ I, and with this as a kind of tolerance to nearly receiving coil 131 and 133 electrical resistivity of earth layer around of receiving coil far away.As can be seen from Figure 5, electric current line that nearly receiving coil 131 and receiving coil far away are 133 is perpendicular to stub boring basically and quickly 101 enters the stratum, thereby has extraordinary side direction resistivity measurement effect.Simultaneously, because the distance of 133 of nearly receiving coil 131 and receiving coils far away is shorter, thereby can provide the side direction resistivity measurement of higher vertical resolution.
Three collecting electrodes 141,142 and 143 are installed on the rib 105 of centralizer and are aligned to straight line, and rib can be straight line or curvilinear structures and have extremely hard surface such as tungsten carbide.Centralizer rib 105 is formed from steel and is integrated on the steel cylindrical sleeves, and this sleeve slidably is socketed in stub boring quickly on 101.Collecting electrode 141,142 and 143 is the button shape, has the periphery and the close borehole wall of circle (being exactly circular) usually herein.The surface of collecting electrode has certain cylinder radian usually to cooperate the surface configuration of centralizer, perhaps have a plane and this plane a shade below the centralizer surface.These electrodes only account for the sub-fraction of whole well periphery, thereby the orientation resistivity measurement can be provided.Equally, these electrodes also only account for the sub-fraction of its centralizer vertical height of installing, thereby the resistivity measurement with high relatively vertical resolution can be provided.In this example, the periphery of each electrode all use as fluorubber or glass fiber one epoxy resin compound insulation materials institute around, this also is that stub boring is quickly kept apart on 101 surface with electrode surface and centralizer rib 105.Collecting electrode 141,142 and 143 provides induced-current to return stub boring 101 passage (in case driving voltage is reverse, electric current is also reverse) quickly from the stratum, and measured current value can be determined the azimuthal resistivity value of the subterranean formation zone that this electrode is faced respectively.Collecting electrode 142 and 143 is more farther from transmitting coil 121 than electrode 141 respectively, thereby can provide than the darker resistivity measurements of collecting electrode 141 investigation depths.
Referring to Fig. 4, go up configuration one lead and introduce circuit by anti-water strand groove at the button electrode (such as 141) of metal mold.This lead passes through a small-sized ring-like band magnetic core coil 562 backs and links to each other with signal ground reference potential (being stub boring 101 bodies quickly).[note: " signal ground " herein mentioned is two reference potentials of isolating mutually with above-mentioned " measuring ground "." signal ground " refers to that quickly the current potential of body is as the reference current potential with stub boring, and " measuring ground " refers to the power supply ground of entire measuring device as with reference to current potential.] small-sized annular coil 562 is used for detecting the electric current of collecting electrode 141 of flowing through, its secondary lead inserts the reverse input end of operational amplifier 563, and another secondary root lead inserts the non-inverting input of operational amplifier 563, as measuring the ground reference potential, between the output of operational amplifier 563 and reverse input end, insert feedback resistance R
BnCollecting electrode 141 passes through magnetic core as small-sized annular coil 562 elementary circles, and the number of turn of 562 levels of small-sized annular coil is N
BnThe gain of operational amplifier 563 is very high, oppositely and the voltage difference V between non-inverting input
iVery little, almost nil.The input impedance of operational amplifier 563 is very high, thereby does not have electric current to flow into any one input basically.Therefore, if the electric current of the collecting electrode 141 of flowing through is I
Bn, the electric current of the small-sized annular coil " secondary " of then flowing through is I
Bn/ N
Bn, electric current I
Bn/ N
BnFeedback resistance R flows through
BnThereby, make the output voltage of amplifier be-R
Bn* I
Bn/ N
BnBecause measured current I
BnQuickly 101 enter the electric current (referring to Fig. 5) of the subterranean formation zone that this electrode faces for leave stub boring from collecting electrode 141, thereby be a kind of tolerance of subterranean formation zone resistivity that collecting electrode 141 is faced, have directionality simultaneously.
All structure and the measuring method with collecting electrode 141 is identical with measuring method with 143 structure for collecting electrode 142, so can be equally referring to Fig. 4.Different is, because collecting electrode 142 and 143 is more farther from transmitting coil 121 than electrode 141 respectively, thereby can provide the azimuthal resistivity measured value darker than collecting electrode 141 investigation depths.
From the above mentioned, actual when carrying out measurement while drilling, can detect simultaneously near, in, the current value of three collecting electrodes far away, thereby can obtain three same orientation simultaneously but the formation resistivity measured value of different investigation depth (shallow, in, dark), this is very useful to appraisal drilling liquid to the intrusion effect on stratum.When stub boring 101 rotations quickly, be actually and make three collecting electrodes implement scanning the also wall of well, thereby can obtain three azimuthal resistivity scanning curves, can generate along the formation resistivity section of borehole axis and well Zhou Erwei, to describe the anisotropic property of stratum on electrically.
The measured electric current I of formation apparent resistivity and receiving coil and/or collecting electrode is inversely proportional to.If the ring-like relatively transmitting coil 121 top stub borings in receiving coil and/or the collecting electrode position quickly voltage on surface are V, so formation apparent resistivity R
a=kV/I, k is an instrumental constant herein, can be determined by experience or model.Certainly also can be by proofreading and correct the influence that compensates Kelvin effect.
Fig. 5 is illustrated in the well with conduction drilling fluid by the formed induced-current distribution map of the ring-like band magnetic core transmitting coil of excitation.Certainly this figure depends on the distribution and the electrical conductivity of ground interlayer, and what Fig. 5 represented is the simplification situation on a single electrical conductivity stratum.
For the function that realizes that nearly drill bit resistivity measurement while drilling device 100 is all, underground survey and the control system important step that is absolutely necessary.Owing to a large amount of detections, processing, storage, communication and demand for control are arranged, generally all comprise microprocessor subsystem and corresponding sub-TT﹠C system in these systems.Have at least two kinds of system's constituted modes can realize above-mentioned requirements.A kind of is the TT﹠C system that adopts single microprocessor to constitute, another kind of then be the TT﹠C system that adopts the multimicroprocessor formation, and two kinds of systems differ from one another.For the TT﹠C system that adopts single microprocessor to constitute, all measurements and control work are handled by a microprocessor, comparatively speaking, have avoided the communication problem between subsystem in the multi-micro processor system, and structure is easier.But, when the more observing and controlling pin of system requirements, then increased the complexity of system because of the input/output end port of expanding system.Simultaneously, when controlled parts on the circuit when microprocessor is far away, both strengthened the difficulty of circuit board wiring, also can cause problems such as interference.For the TT﹠C system that adopts multimicroprocessor to constitute, characteristics are then just in time opposite.Because whole observing and controlling problem is distributed to the communication subsystem that is made of a plurality of microprocessors and goes to finish, comparatively speaking, the observing and controlling function singleness of single subsystem, circuit board wiring is convenient, and interference problem solves easily.But the information exchange between each subsystem has but become a big problem, in case because certain factor causes communication not smooth, then the function of whole system might can't realize.
The master-slave mode TT﹠C system that has adopted multimicroprocessor and local serial communication bus to constitute in an example of the present invention, as shown in Figure 6.Whole system comprises a main communication subsystem 300 and a plurality of from communication subsystem i (as 400,500,------).Main communication subsystem also needs as requested by local serial communication bus 319 to respectively sending control command and data and/or reception from respectively from the information of communication subsystem i from communication subsystem i except that the TT﹠C task of finishing self.And from communication subsystem i except that the TT﹠C task of finishing self, also need to carry out corresponding operation and/or corresponding information is sent to main communication subsystem according to the control command and the data of the main communication subsystem that receives by local serial communication bus 319.
Existing now multiple serial communication bus can be used, as RS-232, SPI, I
2C etc., this example has adopted I
2The C serial communication bus.
Fig. 7 is circuit theory diagrams of main communication subsystem 300 in this example, memory 302, realization and down-hole that this circuit comprises the parts 320 and 325 of realizing the down-hole power monitoring function, realize the down-hole information memory function other from communication subsystem carry out the parts 315 of information exchange and local serial communication bus 319 and realization with information that deposit the down-hole at aboveground serial communication interface 310 and the ground serial communication bus 314 that plays back to ground-based computer, and the core of circuit is a microprocessor system 301.Microprocessor system 301 comprises internal storage and basic clock, timing and I/O function (not expression separately).Down-hole power monitor 320 detects the output valve of each power supply, the output current of each battery pack, the ampere-hour of working etc., and export these detected values to microprocessor system 301, thereby system can understand whether unusual whether each power supply output current, each battery pack transfinite, the residue ampere-hour of each battery pack etc., and turns on and off corresponding power supply to guarantee the Electrical Safety of system by down-hole power controller 325.Microprocessor system 301 by local serial communication interface 315 and local serial communication bus 319 to respectively sending control command and data from communication subsystem i, and with received respectively from the memory 302 that survey data and the state of communication subsystem i is kept at expansion.In case entire measuring device 100 trips out ground, all information that are kept in the memory 302 can be by ground serial communication interface 310 and 314 unloadings of ground serial communication bus to ground-based computer, simultaneously, measurement mechanism 100 also can receive control command and the data that ground-based computer sends by this bus.In this example, realize that the mutual communication between the master and slave subsystem is referred to as " local serial communication ", and realize that the mutual communication between measurement mechanism 100 and the ground-based computer is referred to as " ground serial communication ", and they have adopted different serial communication bus, and the former is I
2The C serial communication bus, the latter is the RS-422 serial communication bus.Certainly, also can adopt single bus.
Fig. 8 is from circuit theory diagrams of communication subsystem 400 in this example, this circuit comprises sine wave generating circuit 420 and 425, nearly receiving coil 131 and the current detection circuit of receiving coil 133 far away and parts 415 and the local serial communication bus 319 that carries out information exchange with down-hole master's communication subsystem 300, and the core of circuit is a microprocessor system 401.Microprocessor system 401 comprises internal storage and basic clock, timing and I/O function (not expression separately).In this example, under the control of microprocessor, sine-wave generator 420 can produce the sine wave (can certainly only produce the sine wave of fixed frequency, fixed amplitude) of different frequency, different amplitudes, frequency range is from 100Hz to 10000Hz, usually the frequency of selecting for use is in several kilohertz range, in this example, frequency is 1500Hz.This sine wave carries out inserting transmitting coil 121 to motivate corresponding induced-current after electric current amplifies through power amplifier 425.The electric current that nearly receiving coil 131 detects inserts multiplexer 460 after converting correspondent voltage (referring to Fig. 3) to by operational amplifier 463, and the electric current that receiving coil far away 133 detects converts correspondent voltage (referring to Fig. 3) back access multicircuit switch 460 to by operational amplifier 466.Under the control of microprocessor 401, this two paths of signals timesharing inserts bandpass filter 450 by multicircuit switch 460, and the function of bandpass filter 450 is that other frequency component of filtering all except that the driving frequency component is to improve the signal to noise ratio of signal.Signal behind bandpass filtering inserts variable gain amplifier 445, purpose is the signal resolution ability of raising system, and gain both can have been selected by microprocessor 401 by predetermined requirement, also can be controlled by microprocessor 401 according to the amplitude of the signal of real-time input.This signal access wave detector 440 carries out detection and filters into direct current signal through low pass filter 435 subsequently, and AD converter 430 is a data signal with analog signal conversion, and outputs in the microprocessor 401.Microprocessor 401 is handled obtaining side direction resistivity above-mentioned and drill bit resistivity measurements these data signals according to predetermined computational methods, and is kept in the memory of microprocessor 401 inside.In case receive " request sends data " of autonomous communication subsystem 300 to order from local serial communication bus 319, then corresponding measured value be sent to main communication subsystem 300 by local serial communication interface 415 and local serial communication bus 319.
Fig. 9 is from circuit theory diagrams of communication subsystem 500 in this example, this circuit comprises the current detection circuit of collecting electrode 141,142 and 143 and parts 515 and the local serial communication bus 319 that carries out information exchange with down-hole master's communication subsystem 300, and the core of circuit is a microprocessor system 501.Microprocessor system 501 comprises internal storage and basic clock, timing and I/O function (not expression separately).In this example, under the control of microprocessor, the electric current that nearly collecting electrode 141 and small-sized ring-like band magnetic core coil 562 detect converts correspondent voltage (referring to Fig. 4) back to by operational amplifier 563 and inserts multiplexer 560, and the electric current that middle collecting electrode 142 and small-sized ring-like band magnetic core coil 565 detect converts correspondent voltage (referring to Fig. 4) back access multiplexer 560 to by operational amplifier 566, and the electric current that collecting electrode 143 simultaneously far away and small-sized ring-like band magnetic core coil 568 detect converts correspondent voltage (referring to Fig. 4) back access multiplexer 560 to by operational amplifier 569.Under the control of microprocessor 501, this three road signals timesharing inserts bandpass filter 550 by multicircuit switch 560, and the function of bandpass filter 550 is that other frequency component of filtering all except that the driving frequency component is to improve the signal to noise ratio of signal.Signal behind bandpass filtering inserts variable gain amplifier 545, purpose is the signal resolution ability of raising system, and gain both can have been selected by microprocessor 501 by predetermined requirement, also can be controlled by microprocessor 501 according to the signal amplitude of real-time input.This signal access wave detector 540 carries out detection and filters into direct current signal through low pass filter 535 subsequently, and AD converter 530 is a data signal with analog signal conversion, and outputs in the microprocessor 501.Microprocessor 501 according to predetermined computational methods to these data signals handle with obtain above-mentioned shallow, in, dark azimuthal resistivity measured value, and be kept in the memory of microprocessor 501 inside.In case receive " request sends data " of autonomous communication subsystem 300 to order from local serial communication bus 319, then corresponding measured value be sent to main communication subsystem 300 by local serial communication interface 515 and local serial communication bus 319.
Certainly, also can be placed in collecting electrode 141,142 and 143 on the drill collar rather than on the centralizer.At this moment, the structure of collecting electrode and small-sized ring-like band magnetic core coil and with their circuit of being correlated with and described above identical.In the occasion of the smooth drill collar of needs, this is very useful.
Relevant by the azimuthal resistivity value that collecting electrode obtains with the residing orientation of drill collar shell (or with respect to other reference point).Such as, suppose and in drill collar 25 (Fig. 1), comprise the conventional measurement orientation and the device of hole deviation, it can provide the orientation and the hole deviation value of well, and can also provide drill collar 25 with respect to magnetic north (promptly so-called " magnetic tool-face ") with respect to the gyrobearing angle of well flash (i.e. what is called " gravity tool-face ").The measured signal of this device can be input to main communication subsystem 300, realizes local storage.If desired, the orientation during rotation also can obtain.
If in drill collar 25 (Fig. 1), comprise conventional down-hole/ground communications device, such as mud pulse generator and supporting equipment, then can be as required, the metrical information of preserving in the memory 302 of main communication subsystem 300 is sent to this down-hole/ground communications device, and be transferred to ground by this device, after the ground-based computer system receives processing, can obtain current on ground in real time and near following a plurality of resistivity measurements on the stratum drill bit, this is for realizing that geologic steering drilling is very useful.
Arrive this, detailed description first-selected example among the present invention, but can derive various skills according to spirit of the present invention.Such as, the electrode that can adopt other structure with ring-like band magnetic core coil, can adopt different mode of connections or different computational methods or even not isostructural electrodes to obtain the side direction resistivity value, can adopt the TT﹠C system of other structure etc.Therefore, this specific embodiment only is used to the present invention is described but not is used to limit the present invention.