CA1039406A - Well surveying apparatus - Google Patents
Well surveying apparatusInfo
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- CA1039406A CA1039406A CA278,967A CA278967A CA1039406A CA 1039406 A CA1039406 A CA 1039406A CA 278967 A CA278967 A CA 278967A CA 1039406 A CA1039406 A CA 1039406A
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- probe
- well
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Abstract
Abstract of the Disclosure Well surveying equipment including a probe which is lowerable into a well, a plurality of gravity actuated sensors carried by the probe for sensing different components of the probe inclination, additional direction sensing means carried by the probe, apparatus for measuring movement of the probe longitudinally in the well, and computer equipment responsive to the gravity actuated sensors, the direction sensing means, and the movement measuring apparatus and programmed to com-pute the direction in which the probe is inclined and the hori-zontal and vertical coordinates between different spaced sta-tions in the well.
Description
~(~39~06 Ba kqround of the Invention This invention relates to apparatus for performing a survey on a well, that is, for determining the extent and direction of departure of the well from a true vertical con-dition. The present application is a division of Canadian Patent Application Serial NoO 216,028 filed December 12, 1974.
In performing a survey on a well by conventional methods, it is customary to lower into the well an instrument which contains an inclination responsive element and a com-pass element, toyether with a camera which photographs -these two elements simultaneously at a particular location in the well, to produce a record of the amount and direction of drift - from the vertical at that locationO A number of such photo-graphs taken at different levels can then be studied, and their information be utilized in calculating the final sur-vey results.
This is obviously a very slcw and inconvenient pro-cedure, often involving a delay of several days between the time that the survey instrument is initially lowered into the well and the time that the photographs are developed and the survey calculations completed. In addition, the procedure in many instances produces an ultimate survey record which is less precise and accurate than would be desired.
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~()394~6 Summary of the Invention The present invention provides apparatus which is capable oE performing a well survey much more eEfectively and quickly than the above discussed conven-tional photographic type equipment. ~s wlll appear, the survey apparatus of the invention can unction to automatically produce a full survey record instantaneously at the same time that the inclination and direction readings are being taken in the well, and can progressively update this information as successive readings are taken on a single run of the equipment into the well.
To achieve these results, the apparatus includes a .
probe which is lowerable into the well, desirably on a simple wireline, and which delivers inclination and direction signals to the surface of.the earth while the probe remains in the well. These signals, in conjunction with a related signal dependent upon the depth of the probe in the well at a parti-cular time, are then fed into a computer unit, which is pro-grammed to perform a predetermined calculation resulting in the development of a record of the survey. More particularly, the probe and depth responsive unit may take readings at two or more successive locations or stations in the well, and the computer is then progra~ned to calculate the departure of the well, in at least one horizontal or vertical direction, between these two stations. Preferably, the computer cal-culates three different departure components, consisting o~
the North-South horizontal departure, East West horizontal departure, and the -true vertical departure between the two stations. A series of such departure computations may be per~ormed by the computer between a series of successive stations in the well, with the incremental departures being
In performing a survey on a well by conventional methods, it is customary to lower into the well an instrument which contains an inclination responsive element and a com-pass element, toyether with a camera which photographs -these two elements simultaneously at a particular location in the well, to produce a record of the amount and direction of drift - from the vertical at that locationO A number of such photo-graphs taken at different levels can then be studied, and their information be utilized in calculating the final sur-vey results.
This is obviously a very slcw and inconvenient pro-cedure, often involving a delay of several days between the time that the survey instrument is initially lowered into the well and the time that the photographs are developed and the survey calculations completed. In addition, the procedure in many instances produces an ultimate survey record which is less precise and accurate than would be desired.
~ , ... ..
. ~_ J ~
~()394~6 Summary of the Invention The present invention provides apparatus which is capable oE performing a well survey much more eEfectively and quickly than the above discussed conven-tional photographic type equipment. ~s wlll appear, the survey apparatus of the invention can unction to automatically produce a full survey record instantaneously at the same time that the inclination and direction readings are being taken in the well, and can progressively update this information as successive readings are taken on a single run of the equipment into the well.
To achieve these results, the apparatus includes a .
probe which is lowerable into the well, desirably on a simple wireline, and which delivers inclination and direction signals to the surface of.the earth while the probe remains in the well. These signals, in conjunction with a related signal dependent upon the depth of the probe in the well at a parti-cular time, are then fed into a computer unit, which is pro-grammed to perform a predetermined calculation resulting in the development of a record of the survey. More particularly, the probe and depth responsive unit may take readings at two or more successive locations or stations in the well, and the computer is then progra~ned to calculate the departure of the well, in at least one horizontal or vertical direction, between these two stations. Preferably, the computer cal-culates three different departure components, consisting o~
the North-South horizontal departure, East West horizontal departure, and the -true vertical departure between the two stations. A series of such departure computations may be per~ormed by the computer between a series of successive stations in the well, with the incremental departures being
-2-399~Q6 summed in the computer to maintain a running total of the.
three departures. ... ...
The output of the computer may be employed to control an x-y plotter, which can then graphically repre-sent the course which the well follows in the earth. Also, a printed record of the three departures, as well as the inclination of the well at each station, the azimuth or -_ direction of that inclination, and any other desired in~
fo.rmation, can be provided ~or each of the various stations . ~ .
at which readings are taken by the probe. .
m e probe itself contains appropriate means for responding to the inclination of the well, desirably includ-. . ing three incllnation sensors for responding to component in-:. clinations in three mutually perpendicular directions. ~lso,. .
15 . the probe contains direction sensing means for determining ; the orientation of the probe with respect to a predetermined kn~wn direction, such as the North-South magnetic field o~ - :
,:.
~ the earth, or true North. ~nere the magnetic North is used as a rererenca direction, the direction sensing means may ~0 . include three magnetically sensitive elements, such as three mutually perpendicular fluxgates, producing directional com-ponents f-~om which the computer may derive the actual direc-tional orientation of the probe. In instances in which sur-. vey.s are to be taken within a drill string or casing which would prevent the use o~ magnetically responsive sensing ele- . .
ments, it is contemplated that a gyro or gyros may be substi--~uted ~or thesz magnetic units.
The sensing probe may be of a charactar similar to .. t'nat discloszd in U.S. Patent ~o. 3,791,043 issued February 12, 1974 to Michael King Russell.on;"Indicating Instruments''.
three departures. ... ...
The output of the computer may be employed to control an x-y plotter, which can then graphically repre-sent the course which the well follows in the earth. Also, a printed record of the three departures, as well as the inclination of the well at each station, the azimuth or -_ direction of that inclination, and any other desired in~
fo.rmation, can be provided ~or each of the various stations . ~ .
at which readings are taken by the probe. .
m e probe itself contains appropriate means for responding to the inclination of the well, desirably includ-. . ing three incllnation sensors for responding to component in-:. clinations in three mutually perpendicular directions. ~lso,. .
15 . the probe contains direction sensing means for determining ; the orientation of the probe with respect to a predetermined kn~wn direction, such as the North-South magnetic field o~ - :
,:.
~ the earth, or true North. ~nere the magnetic North is used as a rererenca direction, the direction sensing means may ~0 . include three magnetically sensitive elements, such as three mutually perpendicular fluxgates, producing directional com-ponents f-~om which the computer may derive the actual direc-tional orientation of the probe. In instances in which sur-. vey.s are to be taken within a drill string or casing which would prevent the use o~ magnetically responsive sensing ele- . .
ments, it is contemplated that a gyro or gyros may be substi--~uted ~or thesz magnetic units.
The sensing probe may be of a charactar similar to .. t'nat discloszd in U.S. Patent ~o. 3,791,043 issued February 12, 1974 to Michael King Russell.on;"Indicating Instruments''.
3~406 BrieE Description_of the Drawinqs ~` The above and other features and objects of the - invention will be better understood from the foilowing detailed description of the typical embodiment illustrated in the ac-companying drawings in which:
Fig. 1 is a somewhat diagrammatic representation of one form of surveying apparatus embodying the invention;
Fig. 2 is an enlarged vertical section through the ,, sensing probe of the ~ig. 1 apparatus;
Fig. 3 illustrates somewhat diagrammatically one of the inclination sensing accélerometers of the Fig. 2 probe;
Fig. 4 illustrates diagrammatically one of,the flux-gate assemblies of the probe;
Fig. 5 is a block diagram representation of the lS circuitry of the apparatus; --Fig. 6 represents diagrammatically and'in perspec- -tive the three instrument fixed axes of the probe; and , Fig. 7 shows an elevation graph made by the x-y plotter.
Description of the Preferred Emb'odiment '' The well surveying apparatus illustrated in Fig. 1 includes an elongated probe 10 which is loweredinto the wel~
11 on a conventional flexible electrically conductive wire-line 12. At the surface of the earth represented at 13, the wireline is wound about a drum 14 which is suitably power driven by a motor represented at 15 to raise and lower the probe in the well. At some location, the wireline passes about a pulley wheel or sheave represented at 16, which en-, gages the wireline with sufficient friction to turn in ,exact correspondence with the upward and downward movement of the ..
: 5'7~-24 ~394~6 probe, and which correspondingly drives an odometer 17 pro-ducing electrlcal pulses in a line 18 at a rate correspond-ing to and directly xepresenting and proportional to -the upward and downward movements of the probe. These pulses or signals in line 18 are fed to a digital computer l9 at the surface of the earth, which is programmed to make certain later-to-be-dlscussed survey computations.
` ~he wireline 12 conducts slgnals upwardly from probe 10 to the surface of the earth and to a data converter circuit 20. These signals may include representations of a number of differen-t inclination and direction components or ,, vectors, which may in some instances be conducted through a number of different mutually insulated wires in a multiple conductor cable functioning as the wireline, but which pre-ferably are carried on a single core cable in multiplexed ,fashion. In the circuitry illustrated in Fig. 5, it is as- r sumed that a multiplexing arrangement is employed,,in order to minimize the cost of the wireline. In Fig. 2, the single , central conductive core or wire of the wireline,,typically formed of copper, is represented at 21, and is connected at its upper end through a line represented at 22 to the input side of data converter 20. About conductor 21 the wireline includes a concentric grounded electrically conductive outer sheath 23, insulated from the inner conductive cora and acting to,complete the second side of the circuit from the probe to the data converter.
Computer 19 may be a general purpose digita`l compu-ter, and preferably has its output connected to an x-y plotter 24 and a printer 25, with the former functioning to produce in real time a graph 26 representing the departure of the well --5-- , ;\ ~0394(~
from true vertical. Printer 25 functions to produce a printed record in real time, t~plcally on a paper tape 27, giving the various departures, inclinations, a~imuths, and other types of survey information at a series of differ-~S ent stations in the well.
Referring now to Fig. 2, the probe lO which is lowered into the well may include an outer vertically elong- _ ated hollcw essentially tubular rigid case or housing 28 which is sealed against entrance thereinto of the pressur-~0 ized well fluid, and is strong enough to withstand its pre-sure, and which is suspended from the upper end of the probe at 29 from wireline 12. An inner vertically elongated case - or housing 30 is contained within outer case 28, and is mount-ed concentrically therein, centered about a main longitudi-nal axis 31. mis inner housing contains the actual sensing equipment and associated electronic circuitry. To protect S
this apparatus against mechanical shocks, the inner housing may be connected to the outer housing by an appropriate shock absorbing structure, as represented at 32. ~is shock absorb-0 ing structure may be attache~ to houslng 30 by means of a T-shaped connector 33, received and retained withln a T-sLot 34 extending transversely of a~is 31 into a lcwer portion of hous-ing 30. When the sensing elements within housing 30 are partial-ly of a magnetic character, to respond to the earth's magnetic '5 field, both o the cases 28 and 30 are made of non-magnetic ma-terial, such as a suitable aluminum alloy, to avoid interference with the desired magnetic.response. In ~ig. 1, it may be as-sumed that the well 11 is itself uncased, and does not contain a drill pipe or other string of pipe or tubing which might o-ther-wise interfere!with the magnetic response. If the probe , ,~,_ . . .. . .
~ 4 ~03~ 6 is substantialLy smaller in diameter than the hole, appro-priate centering or spacing springs 35 may be provided for maintaining the probe in an accurately centered and aligned position in the well during the loweriny procedureO
~5 Probe lO contains sensing means designated gener-ally by the number 36 (FigO 2), for responding to the in clination of the probe axis 31 with respect to the vertical~ ~
In addition, the probe contains second sensing means desig-nated by the number 37, for sensing the relationship between the probe axis 31 and the earth's magnetic fieldO The in-clination as determined by the first sensing means 36 may ultimately be read out by printer 25 as the 'drift angle' D (FigO 1) between probe axis 31 and a true vertical line VO To attain an accurate indication of this drift angle in all positions of the probe, means 36 desirably include three separate inclination responsive units 38, 39 and 40, which have three different mutually perpendicular sensing axes 0~, OX, and OZ ~FigO 6), and which sense drift angle components between their respective axes and the true verti-~0 cal line VO More par-ticularly, the unit 40 may have its axis oZ aligned with tcoincident with) the longitudinal axis 31 of the probe, to extend directly vertically when the probe itself is in a true vertical posi-tionO unit 40 then functions to produce or control an output signal, desirably a DoCo volt-!5 age siynal, whose value is an analog representation, and pre~erably a triynometric function, of the angle D between axis OZ and the vertical in any par-ticular position oE the instrumentD Similarly, unit 38 produces an output voltage or other signal which is an analog representation of the 0 angularity between axis OY and the vertical~ while unit 39 : 5~ 4 1039~
produces a corresponding analog signal representing the angle between axis C~ and the vertical, both of these s.ig-nals like the first signal preferably being trigonometric functions of the angles representedO As will be apparent, when axis OZ is in dixectly vertical position, the two axes OX and OY extend directly horizontally and perpendicular to one anotherO In a predetermined reference or zero position, OZ is vertical, Y extends horizontally in a North-South direction Imagnetic North) and oX extends horizontally and in an East-West directionO
Ihe direction sensing means 37 include three individual units 41, 42, and 43 for sens1ng three component angularities between three different mutually perpendicular axes respectively and the earth's magnetic field îmagnetic 15 North-South line)O One of these units, say unit 43, may have tbe same axis OZ as inclination sensing unit 40 (co-inciding with instrument axis 31), to produce an output signal which is an analog representation of the angularity bekween axis OZ and the earth's magnetic fieldO Unit 41 may have an axis Yl which is parallel to axis oY of in-clination sensing unit 38, and which may be treated ana-lytically as the same axisO Similarly unit 43 may have an axis 0 ~ ~thich is parallel to and can be treated analyti-' cally as coinciding with axis OX o~ unit 39O These three units ~l, 42 and 43 produce output signals, preferably DoCo voltag~e signals, whose values constitute analog represen-tations of (desirably trigonometric functions of) the angles between each o these axes O;Y, OX and OZ respectively and the earth's magnetic ield in any particular position o~
the probeO
578~4 Q~;
~1hile i-t is contemplated that the three inclin-atlon sensing units 38, 39, and 40 may take any of various different forms, it is presen~ly preferred that these sens-ing units be three iden-tical accelerometers, desirably of the force balance type, each ~unc-tioning to measure the ac-celeration of gravity along its particular instrument-fixed axis OY, OX, OL OZ o Fig. 3 illustrates one kncwn type o~
force balance accelerometçr, speciEically of the "Q-Flex"
design, which may be utilized. In that Figure, the acceler-ometer 38 and its axis OY have been represented as typieal of the three accelerometers and their relationship to their individual axes.
The accelerometer of Fig. 3 includes a proo~ mass 44 which is mounted between two permanent magnets 49 and 50 for movement along the sensing or critical axis OY o~ unit 38, and which is restrained against and not free for move-ment in any other direction. In Fig. 3, this confined single-axis mounting is effected by forming the proof mass at the center of and integral with a disc 46 centered about axis oY, with the periphery o~ the disc being connected at one side only to a rigid support 47 through a reduced neck 48 which is very thin in a direction parallel to axis O:Y but not in other directions, to thereby permit movement of di.sc 46 and mass 44 only in the desired direction along axis OY.
~5 Unit 44-46 and its neck 4~ may be formed of an appropriately slightly resilient material, such as quartz, causing the unit 44-46 to resiliently return to the illustrated central position of Fiy. 3, with a motion sensing element 51 being so located as to sense movements of unit 44-46 in either direction ~rom the Fig. 3 normal cen-tered position, Element r:~ 9 _ ~ ~lW- ~
5~ 24 :
~ 3~
51 may be a capacltive type pickoff, coac-ting with a vapor ~: deposited metallic film 146 for~ed on disc 46 to provide a pick off signal which energizes a servo unit 52 to supply current to .a coil 53, wound about and movable with the proof mass, from a power source 54 and at a controlled value just sufficient to coact with magnets 49 and 50 in always maintaininy disc 46, mass 44, and coil 53 in the FigO 3 normal centered positionO
That is, the current which flows through coil 53 is just suf-ficient to react with the magnetic field of magnets 49 and 50 in overcoming any gravity induced displacement of elements 44 and 46 to return these parts to their center position regardless of the inclination of axis OY with respect to the verticalO When axis O.Y is in the FigO 3 hori~ontal position, there is no tend-ency for gravity displacement of elements 44 and 46 in either direction along axis OY~ and consequently no feedback current is fed to coil 53 by servo 52O If, hcwever~ the probe is turned to a position in which axis OY is no longer directly horizontal, the pickoff element 51 senses the .resultan-t displacement of ele-~; ments 44 and 46 along axis OY, to cause servo 52 to produce a current in coil 53 just counteracting ~he e~fect of gravity and returning these parts to their centered positionsO An output signal is taken from the accelerometer assembly through two out-put lines 55 across a resistor 56, with the result that this signal, which has a predetermined knuwn value when OY is verticaL
~5 and changes from positive to negative at 90 to the vertical, constitutes the desired analog representation of the angular-ity o~ the accelerometer axis O.Y with respect to the verticalO
It will of course be apparent that the mounting portion 148 of element 46, as well as the magnets 49 and S0, and pickoff unit 51, are all mounted in ~ixed positions relative to case 30 of 5~ 4 ~394~6 the probe, as by rigid attachment of these parts to a rigid support 47, combined with rigid at-tachment of that support to the caseO
The output signals a, b, and c from accélerometers S 38, 39, and 40 are fed to a multi.plexing circuit 57 (FigD 5), through three separate lines 58, 59, and 60 respectivelyO
Each of these lines may include a resistor-capacitor network represented at 61, which provides a low pass filter for smoothing out any variations produced by vibration of the probeO As will be discussed in greater detail at a later point, the multiplexing circuit 57 may include a solid state switching unit 62 containing a series of FET
(Field Effect Transistor) switches, for periodically sampling the signal voltages on lines 58, 59, and 60, and on three additional lines 63, 64, and 65 from the previously mentioned magnetic units - 41, 42, and 43, to encode these signals for transmission by telemetry to the surface of the earth on wlreline 120 me three units 41, 42, a~ld 43 for responding to components of the earth's magnetic :Eield preferably take ~20 the form of fluxgates, which are of Xnown type, and one of which is illustrated generally in FiyO 40 As seen in that figure, each of the fluxgate units may include two parallel identical rods 66 and 67, formed of a saturable magnetic material, de5irably mumetal, which rods are mounted in fixed positions relative to the probe case 30, with the l.ongitudinal axes 68 of the rods being parallel to the as-sociated one of the discussed instrument fixed axes o:Y, oX
or OZ (illustrated as oy in Fig. 4)0 Two insulated coils 69 and 70 are wound about the rods 66 and 67, and are con-~0 nected in series but in opposition to one another in a cir-cuit which is energized by the secondary of a transformer 71 ~03~4~6 whose primary is connected to t~e outpu-~ of an oscillator 72, supplying a relatively high frequency alternating current to the transformer and coils. This oscillator may as an example operate at a frequency of l kilohertz. The center of the secondary coil of transformer 71 may be grounded as shown, and an output sig'nal may be taken from the point between coils 69 and 70 through a line 73. The rods 66 and 67 are designed to become saturated with magnetic flux twice on each cycle of the alternating current. However, since the two cores are connected in magnetic oppositionj the earth's magnetic field component along the fluxgate axis will add to the coil induced magnetic field in one core 66 or ~7 while subtracting from the coil induced field in the other core, with the condition being re-versed on each reversal of the direction of the alternating ~5 current. Thus on each half cycle of the alternating current, one core 66 or 67 becomes saturated before the other, and re-~' mains saturated after the other. An output signal appears on line 73 only during periods when one but not both of the cores 66 or 67 is saturated. During those periods, the dif-~0 ference in reactance of the two coils causes an imbalance in the voltage developed across each coil and a resultant signal current flows through line 73. Since the portion of each cycle during whirh only one core is saturated is directly dependent upon the strength of the earth's magnetic field companent along the corresponding axis OY, OX or OZ, the width of the output pulses on line 73 is a function of the specified magnetic field component. The applied voltage may be selected to d'rive the cores to saturation at about one-half the peak voltage attained on each half cycle. It will also be apparent that the apparatus may be designed to respond to desaturation of the cores rather than saturation if desired.
The second harmonic of the signal on line 73 may be amplified by an amplifier 173, and then be fed to a phase-sensitive demodulator 74 supplied with a second har-, .. _ ......... . ... ...
57~-~4 ~(~394~6 monic reference voltage from a second harmonic generator 75 energized by a reference voltage derived from oscilLator 720 The outpu-t voltage from the demodulator 74 is in turn fed to an integrator 2760 This integrator acts to create a DoCo current which divldes between the two flux gate coils 69 and 70 an~ therc~y crea~es a maynetic field about each ~f th~
mumetal rods 66 and 670 This field opposes the component of the earth's field parallel to the mumetal rodsO The action of this feedback loop is such that the output signal of the phase sensitive demodulator is driven to virtually zero volts DoCo When this servoing action has sta~ilized, the outpu~
-voltage from the flux gates at line 73 will indicate virtually zero output signalO The ~OCo current output of the integrator which flGwg through the fluxgates is an ana~og of the magnetic ~ield parallel to the mumetal rodsO This current is converted to a DoCo voltage via resistor 280, the current sensing resistor.
As seen in FigO S, the three DoCo voltage signals d, e, and f from the three integrators controlled by fluxgates 41, 42, and 43 respectively are delivered from their respective demodulators to the three lines 63, 64, and 65, as analog voltage signals representing the intensities of the earth's magnetic field components along axes OY, OX, and OZ respectivelyO These analog signals are conducted by lines 63, 64, and 65 to the input side of FET switch assembly 620 The multiplPxing circuit 57 functions to transmit a series of siynals sequentially through wireline 12 to the surface o~ the earth, representing the previously discussed voltage signals a, b, c, d, e, and f on lines 58, 59, 60, 63, 64, and 65 respectivelyO For this purpose~ the solid state switch assembly 62 i~ncludes a series of FET switches 62a, 62b, etcO, or other switches, for sequentially connect-ing lines S8, 59, 60, 63, 64, and 65 to a line 76 (FigO 5), , . . .
under the control of a four bit ~CD (binary coded decimal) counter 77 whose outputs act through a logic circuit 78 to close the various FET switches in a predetermined repeating sequence. During each interval when one of the FET switches is closed, the voltage on the corresponding line 58, 59, 60, 63, 64, or 65 is utilized to control the amount of time which elapses be-tween two successive pulses on wireline 12, by determining the time required for a constant current generator 78 to charge the upper side of a capacitor 79 from an initially low negative value to the value of the voltage on the particular FET switch being read out. For this purpose, when each FET switch is closed, the upper side of the capacitor may be initially shorted or returned to, say, a minus 6 volt potential, by instantaneous closure of a discharge switch 80, which then immediately reopens to allow the constant current generator 78 to commence recharging of the capacitor. When the charge at the upper side of the capacitor reaches a certain predetermined level which is still negative but not as much so as the initial discharge voltage, sa~ for example when the capacitor charge reaches the minus four volt level, a first comparator 81 is automatically actuated to turn on a controlled bistable output circuit 82, which remains on until a second comparator 83 senses that the capacitor has reached a charge level corresponding to the voltage of the signal in line 76 from the EET
switch, and actuates bistable circuit or flip-flop 82 to its off condition. When thus turned off, the bistable switch actuates dis-charge switch 80, instan-taneously, to discharge capacitor 79 again and commence another cycle of operation. Also, the actuation of bi-stable circuit 82 to its off condition ac-ts through control line 84 to advance BCD counter 77 to the next successive count, which acts through logic 78 to open the particular FET switch which had pxeviously been closed and to close the next successive FET
switch. A pulse driver circui-t 84' is controlled by bistable ~Q13941~t6 circuit 82 and acts to produce an output pulse in wireline 12 each time that the bistable circuit is switched ~ff. This pulse is very short in duration, and terminates well before the reset comparator 8] is actuated on the next successive cycle, so that the timing between successive pulses on wireline 12 represents accurately in analog fashion the voltage of the par-ticular signal a, b, c, d, e, or f which con-trolled that timing. The signals are thus fed to the surface of the earth sequentially in a multiplexed pulse time modulated stream, for de-coding from that multiplexed condition before delivery to thesurface computer.
The various successive multiplexed signals on wireline 12 are identified and distinguished from one an-other by provision of suitable sync signals in conjunction there-with, preferably consisting of an extended length delay intervalbetween two successive pulses at the end of each series of in-formation signals a, b, c, d, e, and f, which delay is longer than any possible interval representing one of the information signals and can therefore be readily distinguished therefrom. For this purpose, the constant current generator 78' has a reduced current rate (say 1/3 of its normal current) to which it is switched by logic 78 through energization of a control line 178 after all of the FET switches have been scanned successively, to thereby charge capacitor 79 at a very slow rate requiring a relativelylong period of time before actuation of comparator 83 and thus produce the desired long synchronizing signal represented by two widely spaced pulses on the wireline. The next actuation of counter 77 after this synchronizing signal causes logic 78 to again close the first of the FET switches and to thus commence formation of another series of pulse time modulated signals on the wireline. It will of course be understood that all of the circuitry just described ~03~4~6 for delivering the multiplexed signals to wireline 12 is contained within the probe case 30.
The pulse time modulated or otherwise multiplexed signals on wireline 12 are decoded at the surface of the earth by the data converter or demultiplexing circuit designated generally by the number 20 in Figs. 1 and 5. This circuit is desirably of a type ac-ting to convert the sequential signals on the wireline to a series of identifiable binary coded decimal (sCD) signals delivered to computer 19 on twelve computer input lines 85 and an associated identifi-cation line 86. The wireline 12 may be connected to the demultiplexing circuit 20 through a capacitor 87, and be similarly connected to the probe circuitry through a capaci-~or 88.
In Fig. 5, the demultiplexing circuitry is typically illustrated as including a four bit scD counter 89 which receives the pulse time modulated signals from the wireline, and is advanced through successive binary counts on its four output lines 90 by the successive pulses. A sync detector 91 responds to the relatively extended sync interval in the ; pulse time modulated series of signals to reset counter 89 to a zero position when the sync signal is received. The length of time that counter 89 remains in each of its vari-ous count conditions is measured by a decimal counter 92, driven by a high frequency clock or oscillator 93, typi-cally having a frequency of 200 kilo-hertz. Thus, the binary coded decimal count on the twelve output lines 85 of counter 92 represents the length of a coxresponding signal intexval between successive pulses on wireline 12, and therefore re-presents the value of a corresponding one of the downholesignals a, b, c, d, e, or f. Counts representing these ~16-r ~ *
31CI~;~94q)6 signals are successively Eed to the computer, in con-junction with identification slgnals on a line 86 keyed to the sync signal on -the wireline and serving to identify to the computer which of the d~wnhole siynals is represented by each of the various computer input counts.
The computer 19 may be a conventional general purpose digital computer which is programmed to make a series of predetermined computations and deliver a series of prede-termined output signals to plotter 24 and printer 25 at each ~10 of a series of uniformly spaced stations along the length of the well. For example, a first of these series of pro-: grammed computations may be formed when probe 10 is at the surface of the earth, with the next series of computations being performed.when the probe is at a station 100 feet down the holeJ and with subse~uent computations being performed at other stations similarly spaced lOO feet apart longitudinally o the hole. As the probe is lowered into the hole, odometer 17 measures the length of wireline which is advanced into the well, and sends a signal through line 18 to computer 19 upon arrival of the probe at each of the predetermined uniformly spaced stations, in response to which the computer commences its series of programmed calculations. In a preferred arrange-ment, the computer makes appropriate calculations to actuate the printer to print successively on the strip of tape, for each of the various stations, the ollowing information:
. 1. The Station Number (typically written as theO
letter 'S' follcwed by the number 1, 2, 3, etc.
e.g. S-l).
2~ The drift anqle (D) of the well and the probe at . r that part:Lcular station (i.e. the angle D of Fig, 1 between the axis of the probe and the txue ~ertlcal).
' 578-24 3Lq~139~6 3. The Azimuth (A) of the well bore and probe at that station (i.e. the compass direction, in degrees, toward which the probe and well bore are inclined at the sta~ion),
Fig. 1 is a somewhat diagrammatic representation of one form of surveying apparatus embodying the invention;
Fig. 2 is an enlarged vertical section through the ,, sensing probe of the ~ig. 1 apparatus;
Fig. 3 illustrates somewhat diagrammatically one of the inclination sensing accélerometers of the Fig. 2 probe;
Fig. 4 illustrates diagrammatically one of,the flux-gate assemblies of the probe;
Fig. 5 is a block diagram representation of the lS circuitry of the apparatus; --Fig. 6 represents diagrammatically and'in perspec- -tive the three instrument fixed axes of the probe; and , Fig. 7 shows an elevation graph made by the x-y plotter.
Description of the Preferred Emb'odiment '' The well surveying apparatus illustrated in Fig. 1 includes an elongated probe 10 which is loweredinto the wel~
11 on a conventional flexible electrically conductive wire-line 12. At the surface of the earth represented at 13, the wireline is wound about a drum 14 which is suitably power driven by a motor represented at 15 to raise and lower the probe in the well. At some location, the wireline passes about a pulley wheel or sheave represented at 16, which en-, gages the wireline with sufficient friction to turn in ,exact correspondence with the upward and downward movement of the ..
: 5'7~-24 ~394~6 probe, and which correspondingly drives an odometer 17 pro-ducing electrlcal pulses in a line 18 at a rate correspond-ing to and directly xepresenting and proportional to -the upward and downward movements of the probe. These pulses or signals in line 18 are fed to a digital computer l9 at the surface of the earth, which is programmed to make certain later-to-be-dlscussed survey computations.
` ~he wireline 12 conducts slgnals upwardly from probe 10 to the surface of the earth and to a data converter circuit 20. These signals may include representations of a number of differen-t inclination and direction components or ,, vectors, which may in some instances be conducted through a number of different mutually insulated wires in a multiple conductor cable functioning as the wireline, but which pre-ferably are carried on a single core cable in multiplexed ,fashion. In the circuitry illustrated in Fig. 5, it is as- r sumed that a multiplexing arrangement is employed,,in order to minimize the cost of the wireline. In Fig. 2, the single , central conductive core or wire of the wireline,,typically formed of copper, is represented at 21, and is connected at its upper end through a line represented at 22 to the input side of data converter 20. About conductor 21 the wireline includes a concentric grounded electrically conductive outer sheath 23, insulated from the inner conductive cora and acting to,complete the second side of the circuit from the probe to the data converter.
Computer 19 may be a general purpose digita`l compu-ter, and preferably has its output connected to an x-y plotter 24 and a printer 25, with the former functioning to produce in real time a graph 26 representing the departure of the well --5-- , ;\ ~0394(~
from true vertical. Printer 25 functions to produce a printed record in real time, t~plcally on a paper tape 27, giving the various departures, inclinations, a~imuths, and other types of survey information at a series of differ-~S ent stations in the well.
Referring now to Fig. 2, the probe lO which is lowered into the well may include an outer vertically elong- _ ated hollcw essentially tubular rigid case or housing 28 which is sealed against entrance thereinto of the pressur-~0 ized well fluid, and is strong enough to withstand its pre-sure, and which is suspended from the upper end of the probe at 29 from wireline 12. An inner vertically elongated case - or housing 30 is contained within outer case 28, and is mount-ed concentrically therein, centered about a main longitudi-nal axis 31. mis inner housing contains the actual sensing equipment and associated electronic circuitry. To protect S
this apparatus against mechanical shocks, the inner housing may be connected to the outer housing by an appropriate shock absorbing structure, as represented at 32. ~is shock absorb-0 ing structure may be attache~ to houslng 30 by means of a T-shaped connector 33, received and retained withln a T-sLot 34 extending transversely of a~is 31 into a lcwer portion of hous-ing 30. When the sensing elements within housing 30 are partial-ly of a magnetic character, to respond to the earth's magnetic '5 field, both o the cases 28 and 30 are made of non-magnetic ma-terial, such as a suitable aluminum alloy, to avoid interference with the desired magnetic.response. In ~ig. 1, it may be as-sumed that the well 11 is itself uncased, and does not contain a drill pipe or other string of pipe or tubing which might o-ther-wise interfere!with the magnetic response. If the probe , ,~,_ . . .. . .
~ 4 ~03~ 6 is substantialLy smaller in diameter than the hole, appro-priate centering or spacing springs 35 may be provided for maintaining the probe in an accurately centered and aligned position in the well during the loweriny procedureO
~5 Probe lO contains sensing means designated gener-ally by the number 36 (FigO 2), for responding to the in clination of the probe axis 31 with respect to the vertical~ ~
In addition, the probe contains second sensing means desig-nated by the number 37, for sensing the relationship between the probe axis 31 and the earth's magnetic fieldO The in-clination as determined by the first sensing means 36 may ultimately be read out by printer 25 as the 'drift angle' D (FigO 1) between probe axis 31 and a true vertical line VO To attain an accurate indication of this drift angle in all positions of the probe, means 36 desirably include three separate inclination responsive units 38, 39 and 40, which have three different mutually perpendicular sensing axes 0~, OX, and OZ ~FigO 6), and which sense drift angle components between their respective axes and the true verti-~0 cal line VO More par-ticularly, the unit 40 may have its axis oZ aligned with tcoincident with) the longitudinal axis 31 of the probe, to extend directly vertically when the probe itself is in a true vertical posi-tionO unit 40 then functions to produce or control an output signal, desirably a DoCo volt-!5 age siynal, whose value is an analog representation, and pre~erably a triynometric function, of the angle D between axis OZ and the vertical in any par-ticular position oE the instrumentD Similarly, unit 38 produces an output voltage or other signal which is an analog representation of the 0 angularity between axis OY and the vertical~ while unit 39 : 5~ 4 1039~
produces a corresponding analog signal representing the angle between axis C~ and the vertical, both of these s.ig-nals like the first signal preferably being trigonometric functions of the angles representedO As will be apparent, when axis OZ is in dixectly vertical position, the two axes OX and OY extend directly horizontally and perpendicular to one anotherO In a predetermined reference or zero position, OZ is vertical, Y extends horizontally in a North-South direction Imagnetic North) and oX extends horizontally and in an East-West directionO
Ihe direction sensing means 37 include three individual units 41, 42, and 43 for sens1ng three component angularities between three different mutually perpendicular axes respectively and the earth's magnetic field îmagnetic 15 North-South line)O One of these units, say unit 43, may have tbe same axis OZ as inclination sensing unit 40 (co-inciding with instrument axis 31), to produce an output signal which is an analog representation of the angularity bekween axis OZ and the earth's magnetic fieldO Unit 41 may have an axis Yl which is parallel to axis oY of in-clination sensing unit 38, and which may be treated ana-lytically as the same axisO Similarly unit 43 may have an axis 0 ~ ~thich is parallel to and can be treated analyti-' cally as coinciding with axis OX o~ unit 39O These three units ~l, 42 and 43 produce output signals, preferably DoCo voltag~e signals, whose values constitute analog represen-tations of (desirably trigonometric functions of) the angles between each o these axes O;Y, OX and OZ respectively and the earth's magnetic ield in any particular position o~
the probeO
578~4 Q~;
~1hile i-t is contemplated that the three inclin-atlon sensing units 38, 39, and 40 may take any of various different forms, it is presen~ly preferred that these sens-ing units be three iden-tical accelerometers, desirably of the force balance type, each ~unc-tioning to measure the ac-celeration of gravity along its particular instrument-fixed axis OY, OX, OL OZ o Fig. 3 illustrates one kncwn type o~
force balance accelerometçr, speciEically of the "Q-Flex"
design, which may be utilized. In that Figure, the acceler-ometer 38 and its axis OY have been represented as typieal of the three accelerometers and their relationship to their individual axes.
The accelerometer of Fig. 3 includes a proo~ mass 44 which is mounted between two permanent magnets 49 and 50 for movement along the sensing or critical axis OY o~ unit 38, and which is restrained against and not free for move-ment in any other direction. In Fig. 3, this confined single-axis mounting is effected by forming the proof mass at the center of and integral with a disc 46 centered about axis oY, with the periphery o~ the disc being connected at one side only to a rigid support 47 through a reduced neck 48 which is very thin in a direction parallel to axis O:Y but not in other directions, to thereby permit movement of di.sc 46 and mass 44 only in the desired direction along axis OY.
~5 Unit 44-46 and its neck 4~ may be formed of an appropriately slightly resilient material, such as quartz, causing the unit 44-46 to resiliently return to the illustrated central position of Fiy. 3, with a motion sensing element 51 being so located as to sense movements of unit 44-46 in either direction ~rom the Fig. 3 normal cen-tered position, Element r:~ 9 _ ~ ~lW- ~
5~ 24 :
~ 3~
51 may be a capacltive type pickoff, coac-ting with a vapor ~: deposited metallic film 146 for~ed on disc 46 to provide a pick off signal which energizes a servo unit 52 to supply current to .a coil 53, wound about and movable with the proof mass, from a power source 54 and at a controlled value just sufficient to coact with magnets 49 and 50 in always maintaininy disc 46, mass 44, and coil 53 in the FigO 3 normal centered positionO
That is, the current which flows through coil 53 is just suf-ficient to react with the magnetic field of magnets 49 and 50 in overcoming any gravity induced displacement of elements 44 and 46 to return these parts to their center position regardless of the inclination of axis OY with respect to the verticalO When axis O.Y is in the FigO 3 hori~ontal position, there is no tend-ency for gravity displacement of elements 44 and 46 in either direction along axis OY~ and consequently no feedback current is fed to coil 53 by servo 52O If, hcwever~ the probe is turned to a position in which axis OY is no longer directly horizontal, the pickoff element 51 senses the .resultan-t displacement of ele-~; ments 44 and 46 along axis OY, to cause servo 52 to produce a current in coil 53 just counteracting ~he e~fect of gravity and returning these parts to their centered positionsO An output signal is taken from the accelerometer assembly through two out-put lines 55 across a resistor 56, with the result that this signal, which has a predetermined knuwn value when OY is verticaL
~5 and changes from positive to negative at 90 to the vertical, constitutes the desired analog representation of the angular-ity o~ the accelerometer axis O.Y with respect to the verticalO
It will of course be apparent that the mounting portion 148 of element 46, as well as the magnets 49 and S0, and pickoff unit 51, are all mounted in ~ixed positions relative to case 30 of 5~ 4 ~394~6 the probe, as by rigid attachment of these parts to a rigid support 47, combined with rigid at-tachment of that support to the caseO
The output signals a, b, and c from accélerometers S 38, 39, and 40 are fed to a multi.plexing circuit 57 (FigD 5), through three separate lines 58, 59, and 60 respectivelyO
Each of these lines may include a resistor-capacitor network represented at 61, which provides a low pass filter for smoothing out any variations produced by vibration of the probeO As will be discussed in greater detail at a later point, the multiplexing circuit 57 may include a solid state switching unit 62 containing a series of FET
(Field Effect Transistor) switches, for periodically sampling the signal voltages on lines 58, 59, and 60, and on three additional lines 63, 64, and 65 from the previously mentioned magnetic units - 41, 42, and 43, to encode these signals for transmission by telemetry to the surface of the earth on wlreline 120 me three units 41, 42, a~ld 43 for responding to components of the earth's magnetic :Eield preferably take ~20 the form of fluxgates, which are of Xnown type, and one of which is illustrated generally in FiyO 40 As seen in that figure, each of the fluxgate units may include two parallel identical rods 66 and 67, formed of a saturable magnetic material, de5irably mumetal, which rods are mounted in fixed positions relative to the probe case 30, with the l.ongitudinal axes 68 of the rods being parallel to the as-sociated one of the discussed instrument fixed axes o:Y, oX
or OZ (illustrated as oy in Fig. 4)0 Two insulated coils 69 and 70 are wound about the rods 66 and 67, and are con-~0 nected in series but in opposition to one another in a cir-cuit which is energized by the secondary of a transformer 71 ~03~4~6 whose primary is connected to t~e outpu-~ of an oscillator 72, supplying a relatively high frequency alternating current to the transformer and coils. This oscillator may as an example operate at a frequency of l kilohertz. The center of the secondary coil of transformer 71 may be grounded as shown, and an output sig'nal may be taken from the point between coils 69 and 70 through a line 73. The rods 66 and 67 are designed to become saturated with magnetic flux twice on each cycle of the alternating current. However, since the two cores are connected in magnetic oppositionj the earth's magnetic field component along the fluxgate axis will add to the coil induced magnetic field in one core 66 or ~7 while subtracting from the coil induced field in the other core, with the condition being re-versed on each reversal of the direction of the alternating ~5 current. Thus on each half cycle of the alternating current, one core 66 or 67 becomes saturated before the other, and re-~' mains saturated after the other. An output signal appears on line 73 only during periods when one but not both of the cores 66 or 67 is saturated. During those periods, the dif-~0 ference in reactance of the two coils causes an imbalance in the voltage developed across each coil and a resultant signal current flows through line 73. Since the portion of each cycle during whirh only one core is saturated is directly dependent upon the strength of the earth's magnetic field companent along the corresponding axis OY, OX or OZ, the width of the output pulses on line 73 is a function of the specified magnetic field component. The applied voltage may be selected to d'rive the cores to saturation at about one-half the peak voltage attained on each half cycle. It will also be apparent that the apparatus may be designed to respond to desaturation of the cores rather than saturation if desired.
The second harmonic of the signal on line 73 may be amplified by an amplifier 173, and then be fed to a phase-sensitive demodulator 74 supplied with a second har-, .. _ ......... . ... ...
57~-~4 ~(~394~6 monic reference voltage from a second harmonic generator 75 energized by a reference voltage derived from oscilLator 720 The outpu-t voltage from the demodulator 74 is in turn fed to an integrator 2760 This integrator acts to create a DoCo current which divldes between the two flux gate coils 69 and 70 an~ therc~y crea~es a maynetic field about each ~f th~
mumetal rods 66 and 670 This field opposes the component of the earth's field parallel to the mumetal rodsO The action of this feedback loop is such that the output signal of the phase sensitive demodulator is driven to virtually zero volts DoCo When this servoing action has sta~ilized, the outpu~
-voltage from the flux gates at line 73 will indicate virtually zero output signalO The ~OCo current output of the integrator which flGwg through the fluxgates is an ana~og of the magnetic ~ield parallel to the mumetal rodsO This current is converted to a DoCo voltage via resistor 280, the current sensing resistor.
As seen in FigO S, the three DoCo voltage signals d, e, and f from the three integrators controlled by fluxgates 41, 42, and 43 respectively are delivered from their respective demodulators to the three lines 63, 64, and 65, as analog voltage signals representing the intensities of the earth's magnetic field components along axes OY, OX, and OZ respectivelyO These analog signals are conducted by lines 63, 64, and 65 to the input side of FET switch assembly 620 The multiplPxing circuit 57 functions to transmit a series of siynals sequentially through wireline 12 to the surface o~ the earth, representing the previously discussed voltage signals a, b, c, d, e, and f on lines 58, 59, 60, 63, 64, and 65 respectivelyO For this purpose~ the solid state switch assembly 62 i~ncludes a series of FET switches 62a, 62b, etcO, or other switches, for sequentially connect-ing lines S8, 59, 60, 63, 64, and 65 to a line 76 (FigO 5), , . . .
under the control of a four bit ~CD (binary coded decimal) counter 77 whose outputs act through a logic circuit 78 to close the various FET switches in a predetermined repeating sequence. During each interval when one of the FET switches is closed, the voltage on the corresponding line 58, 59, 60, 63, 64, or 65 is utilized to control the amount of time which elapses be-tween two successive pulses on wireline 12, by determining the time required for a constant current generator 78 to charge the upper side of a capacitor 79 from an initially low negative value to the value of the voltage on the particular FET switch being read out. For this purpose, when each FET switch is closed, the upper side of the capacitor may be initially shorted or returned to, say, a minus 6 volt potential, by instantaneous closure of a discharge switch 80, which then immediately reopens to allow the constant current generator 78 to commence recharging of the capacitor. When the charge at the upper side of the capacitor reaches a certain predetermined level which is still negative but not as much so as the initial discharge voltage, sa~ for example when the capacitor charge reaches the minus four volt level, a first comparator 81 is automatically actuated to turn on a controlled bistable output circuit 82, which remains on until a second comparator 83 senses that the capacitor has reached a charge level corresponding to the voltage of the signal in line 76 from the EET
switch, and actuates bistable circuit or flip-flop 82 to its off condition. When thus turned off, the bistable switch actuates dis-charge switch 80, instan-taneously, to discharge capacitor 79 again and commence another cycle of operation. Also, the actuation of bi-stable circuit 82 to its off condition ac-ts through control line 84 to advance BCD counter 77 to the next successive count, which acts through logic 78 to open the particular FET switch which had pxeviously been closed and to close the next successive FET
switch. A pulse driver circui-t 84' is controlled by bistable ~Q13941~t6 circuit 82 and acts to produce an output pulse in wireline 12 each time that the bistable circuit is switched ~ff. This pulse is very short in duration, and terminates well before the reset comparator 8] is actuated on the next successive cycle, so that the timing between successive pulses on wireline 12 represents accurately in analog fashion the voltage of the par-ticular signal a, b, c, d, e, or f which con-trolled that timing. The signals are thus fed to the surface of the earth sequentially in a multiplexed pulse time modulated stream, for de-coding from that multiplexed condition before delivery to thesurface computer.
The various successive multiplexed signals on wireline 12 are identified and distinguished from one an-other by provision of suitable sync signals in conjunction there-with, preferably consisting of an extended length delay intervalbetween two successive pulses at the end of each series of in-formation signals a, b, c, d, e, and f, which delay is longer than any possible interval representing one of the information signals and can therefore be readily distinguished therefrom. For this purpose, the constant current generator 78' has a reduced current rate (say 1/3 of its normal current) to which it is switched by logic 78 through energization of a control line 178 after all of the FET switches have been scanned successively, to thereby charge capacitor 79 at a very slow rate requiring a relativelylong period of time before actuation of comparator 83 and thus produce the desired long synchronizing signal represented by two widely spaced pulses on the wireline. The next actuation of counter 77 after this synchronizing signal causes logic 78 to again close the first of the FET switches and to thus commence formation of another series of pulse time modulated signals on the wireline. It will of course be understood that all of the circuitry just described ~03~4~6 for delivering the multiplexed signals to wireline 12 is contained within the probe case 30.
The pulse time modulated or otherwise multiplexed signals on wireline 12 are decoded at the surface of the earth by the data converter or demultiplexing circuit designated generally by the number 20 in Figs. 1 and 5. This circuit is desirably of a type ac-ting to convert the sequential signals on the wireline to a series of identifiable binary coded decimal (sCD) signals delivered to computer 19 on twelve computer input lines 85 and an associated identifi-cation line 86. The wireline 12 may be connected to the demultiplexing circuit 20 through a capacitor 87, and be similarly connected to the probe circuitry through a capaci-~or 88.
In Fig. 5, the demultiplexing circuitry is typically illustrated as including a four bit scD counter 89 which receives the pulse time modulated signals from the wireline, and is advanced through successive binary counts on its four output lines 90 by the successive pulses. A sync detector 91 responds to the relatively extended sync interval in the ; pulse time modulated series of signals to reset counter 89 to a zero position when the sync signal is received. The length of time that counter 89 remains in each of its vari-ous count conditions is measured by a decimal counter 92, driven by a high frequency clock or oscillator 93, typi-cally having a frequency of 200 kilo-hertz. Thus, the binary coded decimal count on the twelve output lines 85 of counter 92 represents the length of a coxresponding signal intexval between successive pulses on wireline 12, and therefore re-presents the value of a corresponding one of the downholesignals a, b, c, d, e, or f. Counts representing these ~16-r ~ *
31CI~;~94q)6 signals are successively Eed to the computer, in con-junction with identification slgnals on a line 86 keyed to the sync signal on -the wireline and serving to identify to the computer which of the d~wnhole siynals is represented by each of the various computer input counts.
The computer 19 may be a conventional general purpose digital computer which is programmed to make a series of predetermined computations and deliver a series of prede-termined output signals to plotter 24 and printer 25 at each ~10 of a series of uniformly spaced stations along the length of the well. For example, a first of these series of pro-: grammed computations may be formed when probe 10 is at the surface of the earth, with the next series of computations being performed.when the probe is at a station 100 feet down the holeJ and with subse~uent computations being performed at other stations similarly spaced lOO feet apart longitudinally o the hole. As the probe is lowered into the hole, odometer 17 measures the length of wireline which is advanced into the well, and sends a signal through line 18 to computer 19 upon arrival of the probe at each of the predetermined uniformly spaced stations, in response to which the computer commences its series of programmed calculations. In a preferred arrange-ment, the computer makes appropriate calculations to actuate the printer to print successively on the strip of tape, for each of the various stations, the ollowing information:
. 1. The Station Number (typically written as theO
letter 'S' follcwed by the number 1, 2, 3, etc.
e.g. S-l).
2~ The drift anqle (D) of the well and the probe at . r that part:Lcular station (i.e. the angle D of Fig, 1 between the axis of the probe and the txue ~ertlcal).
' 578-24 3Lq~139~6 3. The Azimuth (A) of the well bore and probe at that station (i.e. the compass direction, in degrees, toward which the probe and well bore are inclined at the sta~ion),
4. qhe measured depth (P) of the probe at the sta-~ . . .
tion (derived directly from odometer 17), .. , . .
tion (derived directly from odometer 17), .. , . .
5. The vertical depth (V) or vertical departura ~l of the probe from its initial location at the ~; surface of the earth.
~;; 10 6. m e North-South departure (N or S) of the probe ;~ and well bore from the point at which the hole ; - commenced at the surface of the earth.
7. The East-West departure (E or W) o the proba and well bore from the point at which the welL
~` 15 commenced at the surface of the earth.
8. Ihe average hole curvature ~K) between'two suc-cessive stations, in degrees per 100 feet, ~re-' ' ferred to as "dog-leg severity").
' As an example, the above information may be printed out for a particular station on tape 27 as follows:
; ' S 012 ...... (Station 12) D 90.22 ... (Drift angle, 90.22 degrees) A 251.97... (A2imuth, 251.97 degrees) P 1200.00 ..(Measured depth, 1200 feet) V 723.47 ... (Vertical depth, 723.~7 feet) -' - S 494.26 ... (Southerly departure, 494.26 feet) : :
W 467.10 ~..(Westerly departure, 467.10 feet) K 3.26 ...; (Hole curvature, 3.26 degrees per ~ ' '; 100 feet) ' S 013 ...... (Station 13). ~-;etc.
, . ~ .
~LQ~9g~0~
Immediately upon arrival of probe 10 at each of the selected stations, odometer 17 automatically causes the com-puter to ini-tiate and substantially instantaneously complete a series of calculations for determining all of the above S specified information for that particular station. The com-puter in turn actuates the printer to immediately print out that information in the manner discussed, and causes the x-y plotter 24 to plot, instantaneously upon arrival of the probe at each station, the advancement of the well hoLe and probe to that station from the preceding one. Thus, a continual up-to-date plot of the well is maintaine~ in real time. The computer may be programmed to produce selectively any on~ of two or more types of graphs, preerably including either a plan vi~w in which the North-South and East~West departure of the hole are plotted progressively against each other as ~- illustrated on the graph 26 of Figs. 1 and 5, or an elevation gxaph as seen in Fig. 7, in which horizootal departure is plotted against vertical depth -to give a vertical profile of the hole. The computer may be actuated between its dif-_20 ferent conditions by a number of push buttons 94 (Fig. 1), including at least four such buttons labelled "PLAN", "ELE-VATION", "RESET/PRINT'' and "HOLD". The "PLAN" button when pressed instructs the computer to produce a Fig. 5 type plan view graph on the plotter, desirably accompanied by a simul-taneous print out by printer 25 of the above discussed infor-mation which it records. -The "ELEVATION" button instructs the computer to produce a Fig. 7 type graph and a print out.
rrhe "RESET/PRINT" button resets the plan ànd elevation oper~
_ ations to a zero condition, and typically also instructs the ~0 computer and printer to produce a single print out of the cur-rent drift and azimuth angles. The "HOLD" button temporarily , . ~[)394~6 halts all operation of the computer and related circuitry at a particular condition.
q~o discuss the mathematics involved in the function-ing o the present apparatus, and the programming of the ~5 computer, to an extent assuring a full understanding of the invention by persons skilled in the art, it may first of all be noted that the three output signals a, b, and c from accelerometers 38, 39, and 40 respectively, re-presenting three inclination components, may be defined as follows:
a = -g sin D cos H
b = g sin D sin H
c - g cos D
where: g is the Gravitational Constant scale fa~tox D is the Drift Angle of the hole and probe as defined hereina~ove H is the 'High Side A~gle', that is, the angle through which probe 10 L
is turned about its longitudinal axis 31 from an orientation in which a predetermined reference point on the outer surface of the inclined probe is at its "high side".
To discuss this "High Side Angle" H more specifically, it is convenient to treat as the "reference point" for this purpose the location at which T-slot 33 of Fig. 2 enters the periphery o~ probe case 30, or more specifically the~center of the T-slot opening (point R in Fig. 2). The "High Side Angle" may then be considered as having a value of zero degrees when the inclined probe is turned about its longitudinal axis 31 t~a position in which this T-slot reference location R is at the ''High Side" of .1 , ~33~
theprobe, that is, the positlon in which poin-t R is higher than in any other position to which theprObe can be turned about its axis. In Fig. 1, this would mean that the T-slot ~ .
would be at the location designated 33', at the left side of S the probe. If the probe is in fact not in this position, the above referred to High Side Angle is the angle ~in degrees) through which the reference point R is turned in a clockwise direction from the zero position (as viewed looking down the hole along axis 31).
The three directional component signals d, e, and f produced by fluxgates 41, 42, and 43 respectively may be defined as follows:
d = -M (cos A cos B cos D cos H - sin A cos B sin H -sin B sin D cos H) 1-5 e = M (cos A cos B cos D sin H t sin A cos B cos H -~; sin B sin D sin H) f = -~ (sin B cos D + cos A cos B sin D) where;
M is the magnetic constant (scale factor) _20 A is the A2imuth Angle, B is the Magnetic Dip Angle, D is the Drift Angle, and H is the High Side Angle.
The computer is preferably programmed to calculate ~5 the drift angle D at each station in accordance with the fol-lowing ormula: ~
D = tan~ c ~ (7) where:
~ 0 ~ D ~ 180 D ~ 0 when numerator - O and denominator~0 D ~ 18C when numerator _ 0 and denominator C 0 D - 90 when denominator = 0 5~8~
` ~63 ;~94~6 0 C D ~90 when denominator ~ O
90 < D - 180 when denominator ~ O
D is m~a~urcd from vcrtical wi-th D - 0 when probe is pointing straight down S a,b c are the values of the drif-t component ~ _ .
~ signals on lines 58, 59 and 60 of Fiy. 5.
:~ To compute the aximuth A, as above de~lned, the computer is preferably programmed in accordance with the foll~wing formula, with the below stated limitations:
A = tan~l (a~ - bd)l r (8) (a2 ~ b2)f - (ad t be)c where:
0 ~ A ~ 360 a, b, c, d, e and f are the signal values on lines 58, 59, 60, 63, 64 and 65 ~15 A ~ 0 when numerator = O and denominator ~0 A = 180 when numerator = O and denominator ,-0 A = 90 when denominator - 0 and numerator C o A ~ 270 when denominator ~ 0 and numerator ~ 0 0 < A ~ 90 when numerator < 0 and denominator < 0 90~ A ~ 180 when numerator ~0 and denominator~> 0 180C A C 270 when numerator ~'O and denominator~ 0 270 ~ A C 360 when numerator ~ 0 and dsnominator C 0 A is measured from magnetic north clockwise with A ~ 0 when probe is pointing toward magnetic north.
The incremental horizontal and vertical departures or coordinates between two successive stations in the well, having drift angles Dl and D2 respectively, and ~zimuths Al and A2 respectively, may be determined by the ~ollowing ormulae ` 3L~)35~6 ~Z (Vertic~l Inci-ementj = 100 cos~ 2- J (9) Z > 0 lf o ' 1 2 ~9O~
< 0 if 90 C - , - lS0 D -~ ~2 ~`~Z = 0 i' 1 = 90O
~X (East-West Increment) = 100 sin (1 2 ) sin ~ (10) o ~Dl + D2~ ~Al I A2 ~ 360 if ~1 ~ A2¦ ~ 180 , use 100 sin ~ ~sin ~
if ~1 ~ A2~ ~ 180 , use 100 sin ( 2 )sin( 2~ ) if ~1 ~ A2¦= 180 , se~ ax - o ~X ~ 0 if < 2 ~ 180 0O Al + A2 ~ 360 2 ~ 180 X ~ 0 if 180~ Al '~ 2 ~ 360 T A -r 360 or 180 c 1 22 . ~ 360 Al ~ A2 ~X = 0 if 2 - = 180 Al ~ A2 ~ 360 O
or - 2 = 0 ~fol } D2 ) ~ A2 ~Y (~ortn-South Increment) ~ 100 sin ~ 2 /cos ~ 2 ~ (11) . I 1 2¦ r ~ 2 ) ~ 2 - if ~Al - A2¦ ~ 180 , use 100 sir,( 2 ) ( 2 if IA1 - A2¦= 180 .set ~Y = 0 A
0 if o ~ 1 2 2 ~goO
Al ~ A2 20 ~ 270' 2 ~ 360 A ~ A~ ,L 3 O O
or oo 1 2- ~ 90 A ~ A ~ 360 or 270 ~ 1 22 ~ 360 0 if 90 ~ 2 ~270 O if 2 . = 90 ~ 270 ~23 -~78~4 The computer calculates these departure increments according to the specified above formulae at each station, and maintains in its memory a running total of these incre-ments as a total vertical departure or depth, and -total East-West and North-South departures, as follcws:
Zt (Vertical Total) - ~ Q Zi (12) i=l Xt (East-West Total) _ ~ Xi (13) - Yt (North-South Total) ~ ~ L~ 4) i-l .
`These total departures are printed out at each station on the printed tape 27, as discussed previously, and the incre-mental departures are ed to the X-Y plotter 24 to produce either or both of the two previously discussed types of graphs.
It is also contemplated that the computer may store in its memory all of the incremental information for the various sta-tions during a probe lcwering operation, with one type of graph being produced by the plotter automatically in real time as the probe is lowered, and with the computer being actuable by one of the pushbuttons 94 after the lcwering operation to actu-ate the plotter to rapidly form from its memory information the other type o graph.
- The hole curvature K is calculated bv the computer according to the following ormula:
K ~ cos~l [cos Dl cos D2 ~ sln Dl sin D2 cos ~A2 ~ Al)¦ (15) ~24- -,., , ' .,,_, . . . ........... . . ..... . .
t 16)~9~
o ~ a1.wa~s < 90 o if ,A~ > 180 , use:
COS-1lCOS D1 cos D2 -~ sin Dl sin D2 cos (3r~ ¦A2 - A1 ¦ )~
iE I A2 - ~ ~ 1 g O U S e cos l¦cos Dl cos D2 ~ sin Dl sin D2 cos (A2 - Al~
o if ¦A2 - ~ 180 , use cos~l ~os Dl cos D2 ~ sin Dl sin D2 J
While a certain specific embodimant of the invention has been disclosed as typical, the invention is of course not limited to this particular form, but rather is applicable broadly to all such variations as 4all wit'nin the SCOp2 of the appended claimsO As an example, it i5 contemplated that a gyro or gyros may ba substituted for the magnetically responsive fluxgates of the probe, to produce directional signals referenced to the true North rather than magne~ic Nortn or referenced to any other appropriate and convenient gyro datermined directionO
Also, the instrument may in some instances be contal~ed witnin a drill string at a set location near the drill, and be lowered witn the string into a wallO In that case, the string ;nay have an appropriately non maynetic section about the prob2 if the discussed magnetic type sensors are employed, to enable the desired response to the earth's ragn2tic fieldu Similarly, many or numerous other variations of the speci~ically dis-closed equipment can be providedu ,
~;; 10 6. m e North-South departure (N or S) of the probe ;~ and well bore from the point at which the hole ; - commenced at the surface of the earth.
7. The East-West departure (E or W) o the proba and well bore from the point at which the welL
~` 15 commenced at the surface of the earth.
8. Ihe average hole curvature ~K) between'two suc-cessive stations, in degrees per 100 feet, ~re-' ' ferred to as "dog-leg severity").
' As an example, the above information may be printed out for a particular station on tape 27 as follows:
; ' S 012 ...... (Station 12) D 90.22 ... (Drift angle, 90.22 degrees) A 251.97... (A2imuth, 251.97 degrees) P 1200.00 ..(Measured depth, 1200 feet) V 723.47 ... (Vertical depth, 723.~7 feet) -' - S 494.26 ... (Southerly departure, 494.26 feet) : :
W 467.10 ~..(Westerly departure, 467.10 feet) K 3.26 ...; (Hole curvature, 3.26 degrees per ~ ' '; 100 feet) ' S 013 ...... (Station 13). ~-;etc.
, . ~ .
~LQ~9g~0~
Immediately upon arrival of probe 10 at each of the selected stations, odometer 17 automatically causes the com-puter to ini-tiate and substantially instantaneously complete a series of calculations for determining all of the above S specified information for that particular station. The com-puter in turn actuates the printer to immediately print out that information in the manner discussed, and causes the x-y plotter 24 to plot, instantaneously upon arrival of the probe at each station, the advancement of the well hoLe and probe to that station from the preceding one. Thus, a continual up-to-date plot of the well is maintaine~ in real time. The computer may be programmed to produce selectively any on~ of two or more types of graphs, preerably including either a plan vi~w in which the North-South and East~West departure of the hole are plotted progressively against each other as ~- illustrated on the graph 26 of Figs. 1 and 5, or an elevation gxaph as seen in Fig. 7, in which horizootal departure is plotted against vertical depth -to give a vertical profile of the hole. The computer may be actuated between its dif-_20 ferent conditions by a number of push buttons 94 (Fig. 1), including at least four such buttons labelled "PLAN", "ELE-VATION", "RESET/PRINT'' and "HOLD". The "PLAN" button when pressed instructs the computer to produce a Fig. 5 type plan view graph on the plotter, desirably accompanied by a simul-taneous print out by printer 25 of the above discussed infor-mation which it records. -The "ELEVATION" button instructs the computer to produce a Fig. 7 type graph and a print out.
rrhe "RESET/PRINT" button resets the plan ànd elevation oper~
_ ations to a zero condition, and typically also instructs the ~0 computer and printer to produce a single print out of the cur-rent drift and azimuth angles. The "HOLD" button temporarily , . ~[)394~6 halts all operation of the computer and related circuitry at a particular condition.
q~o discuss the mathematics involved in the function-ing o the present apparatus, and the programming of the ~5 computer, to an extent assuring a full understanding of the invention by persons skilled in the art, it may first of all be noted that the three output signals a, b, and c from accelerometers 38, 39, and 40 respectively, re-presenting three inclination components, may be defined as follows:
a = -g sin D cos H
b = g sin D sin H
c - g cos D
where: g is the Gravitational Constant scale fa~tox D is the Drift Angle of the hole and probe as defined hereina~ove H is the 'High Side A~gle', that is, the angle through which probe 10 L
is turned about its longitudinal axis 31 from an orientation in which a predetermined reference point on the outer surface of the inclined probe is at its "high side".
To discuss this "High Side Angle" H more specifically, it is convenient to treat as the "reference point" for this purpose the location at which T-slot 33 of Fig. 2 enters the periphery o~ probe case 30, or more specifically the~center of the T-slot opening (point R in Fig. 2). The "High Side Angle" may then be considered as having a value of zero degrees when the inclined probe is turned about its longitudinal axis 31 t~a position in which this T-slot reference location R is at the ''High Side" of .1 , ~33~
theprobe, that is, the positlon in which poin-t R is higher than in any other position to which theprObe can be turned about its axis. In Fig. 1, this would mean that the T-slot ~ .
would be at the location designated 33', at the left side of S the probe. If the probe is in fact not in this position, the above referred to High Side Angle is the angle ~in degrees) through which the reference point R is turned in a clockwise direction from the zero position (as viewed looking down the hole along axis 31).
The three directional component signals d, e, and f produced by fluxgates 41, 42, and 43 respectively may be defined as follows:
d = -M (cos A cos B cos D cos H - sin A cos B sin H -sin B sin D cos H) 1-5 e = M (cos A cos B cos D sin H t sin A cos B cos H -~; sin B sin D sin H) f = -~ (sin B cos D + cos A cos B sin D) where;
M is the magnetic constant (scale factor) _20 A is the A2imuth Angle, B is the Magnetic Dip Angle, D is the Drift Angle, and H is the High Side Angle.
The computer is preferably programmed to calculate ~5 the drift angle D at each station in accordance with the fol-lowing ormula: ~
D = tan~ c ~ (7) where:
~ 0 ~ D ~ 180 D ~ 0 when numerator - O and denominator~0 D ~ 18C when numerator _ 0 and denominator C 0 D - 90 when denominator = 0 5~8~
` ~63 ;~94~6 0 C D ~90 when denominator ~ O
90 < D - 180 when denominator ~ O
D is m~a~urcd from vcrtical wi-th D - 0 when probe is pointing straight down S a,b c are the values of the drif-t component ~ _ .
~ signals on lines 58, 59 and 60 of Fiy. 5.
:~ To compute the aximuth A, as above de~lned, the computer is preferably programmed in accordance with the foll~wing formula, with the below stated limitations:
A = tan~l (a~ - bd)l r (8) (a2 ~ b2)f - (ad t be)c where:
0 ~ A ~ 360 a, b, c, d, e and f are the signal values on lines 58, 59, 60, 63, 64 and 65 ~15 A ~ 0 when numerator = O and denominator ~0 A = 180 when numerator = O and denominator ,-0 A = 90 when denominator - 0 and numerator C o A ~ 270 when denominator ~ 0 and numerator ~ 0 0 < A ~ 90 when numerator < 0 and denominator < 0 90~ A ~ 180 when numerator ~0 and denominator~> 0 180C A C 270 when numerator ~'O and denominator~ 0 270 ~ A C 360 when numerator ~ 0 and dsnominator C 0 A is measured from magnetic north clockwise with A ~ 0 when probe is pointing toward magnetic north.
The incremental horizontal and vertical departures or coordinates between two successive stations in the well, having drift angles Dl and D2 respectively, and ~zimuths Al and A2 respectively, may be determined by the ~ollowing ormulae ` 3L~)35~6 ~Z (Vertic~l Inci-ementj = 100 cos~ 2- J (9) Z > 0 lf o ' 1 2 ~9O~
< 0 if 90 C - , - lS0 D -~ ~2 ~`~Z = 0 i' 1 = 90O
~X (East-West Increment) = 100 sin (1 2 ) sin ~ (10) o ~Dl + D2~ ~Al I A2 ~ 360 if ~1 ~ A2¦ ~ 180 , use 100 sin ~ ~sin ~
if ~1 ~ A2~ ~ 180 , use 100 sin ( 2 )sin( 2~ ) if ~1 ~ A2¦= 180 , se~ ax - o ~X ~ 0 if < 2 ~ 180 0O Al + A2 ~ 360 2 ~ 180 X ~ 0 if 180~ Al '~ 2 ~ 360 T A -r 360 or 180 c 1 22 . ~ 360 Al ~ A2 ~X = 0 if 2 - = 180 Al ~ A2 ~ 360 O
or - 2 = 0 ~fol } D2 ) ~ A2 ~Y (~ortn-South Increment) ~ 100 sin ~ 2 /cos ~ 2 ~ (11) . I 1 2¦ r ~ 2 ) ~ 2 - if ~Al - A2¦ ~ 180 , use 100 sir,( 2 ) ( 2 if IA1 - A2¦= 180 .set ~Y = 0 A
0 if o ~ 1 2 2 ~goO
Al ~ A2 20 ~ 270' 2 ~ 360 A ~ A~ ,L 3 O O
or oo 1 2- ~ 90 A ~ A ~ 360 or 270 ~ 1 22 ~ 360 0 if 90 ~ 2 ~270 O if 2 . = 90 ~ 270 ~23 -~78~4 The computer calculates these departure increments according to the specified above formulae at each station, and maintains in its memory a running total of these incre-ments as a total vertical departure or depth, and -total East-West and North-South departures, as follcws:
Zt (Vertical Total) - ~ Q Zi (12) i=l Xt (East-West Total) _ ~ Xi (13) - Yt (North-South Total) ~ ~ L~ 4) i-l .
`These total departures are printed out at each station on the printed tape 27, as discussed previously, and the incre-mental departures are ed to the X-Y plotter 24 to produce either or both of the two previously discussed types of graphs.
It is also contemplated that the computer may store in its memory all of the incremental information for the various sta-tions during a probe lcwering operation, with one type of graph being produced by the plotter automatically in real time as the probe is lowered, and with the computer being actuable by one of the pushbuttons 94 after the lcwering operation to actu-ate the plotter to rapidly form from its memory information the other type o graph.
- The hole curvature K is calculated bv the computer according to the following ormula:
K ~ cos~l [cos Dl cos D2 ~ sln Dl sin D2 cos ~A2 ~ Al)¦ (15) ~24- -,., , ' .,,_, . . . ........... . . ..... . .
t 16)~9~
o ~ a1.wa~s < 90 o if ,A~ > 180 , use:
COS-1lCOS D1 cos D2 -~ sin Dl sin D2 cos (3r~ ¦A2 - A1 ¦ )~
iE I A2 - ~ ~ 1 g O U S e cos l¦cos Dl cos D2 ~ sin Dl sin D2 cos (A2 - Al~
o if ¦A2 - ~ 180 , use cos~l ~os Dl cos D2 ~ sin Dl sin D2 J
While a certain specific embodimant of the invention has been disclosed as typical, the invention is of course not limited to this particular form, but rather is applicable broadly to all such variations as 4all wit'nin the SCOp2 of the appended claimsO As an example, it i5 contemplated that a gyro or gyros may ba substituted for the magnetically responsive fluxgates of the probe, to produce directional signals referenced to the true North rather than magne~ic Nortn or referenced to any other appropriate and convenient gyro datermined directionO
Also, the instrument may in some instances be contal~ed witnin a drill string at a set location near the drill, and be lowered witn the string into a wallO In that case, the string ;nay have an appropriately non maynetic section about the prob2 if the discussed magnetic type sensors are employed, to enable the desired response to the earth's ragn2tic fieldu Similarly, many or numerous other variations of the speci~ically dis-closed equipment can be providedu ,
Claims
1. Apparatus comprising a probe adapted to be low-ered into a well and including sensing means responsive to changes in inclination of said probe, and computer means res-ponsive to said sensing means and programmed to compute the azimuth direction in which said probe is inclined relative to the vertical, and means for displaying said azimuth direction, said sensing means including three mutually perpendicular gravity actuated sensors producing outputs a, b, and c, and three mutually perpendicular compass direction responsive sensors producing outputs d, e, and f, said computer means being programmed to calculate said azimuth direction according to the formula:
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA216,028A CA1031074A (en) | 1974-12-12 | 1974-12-12 | Well surveying apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1039406A true CA1039406A (en) | 1978-09-26 |
Family
ID=4101854
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA216,028A Expired CA1031074A (en) | 1974-12-12 | 1974-12-12 | Well surveying apparatus |
| CA278,967A Expired CA1039406A (en) | 1974-12-12 | 1977-05-24 | Well surveying apparatus |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA216,028A Expired CA1031074A (en) | 1974-12-12 | 1974-12-12 | Well surveying apparatus |
Country Status (1)
| Country | Link |
|---|---|
| CA (2) | CA1031074A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5287119A (en) * | 1987-10-14 | 1994-02-15 | Wang Laboratories, Inc. | Computer input device using an orientation sensor |
| US5363120A (en) * | 1987-10-14 | 1994-11-08 | Wang Laboratories, Inc. | Computer input device using orientation sensor |
-
1974
- 1974-12-12 CA CA216,028A patent/CA1031074A/en not_active Expired
-
1977
- 1977-05-24 CA CA278,967A patent/CA1039406A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5287119A (en) * | 1987-10-14 | 1994-02-15 | Wang Laboratories, Inc. | Computer input device using an orientation sensor |
| US5363120A (en) * | 1987-10-14 | 1994-11-08 | Wang Laboratories, Inc. | Computer input device using orientation sensor |
Also Published As
| Publication number | Publication date |
|---|---|
| CA1031074A (en) | 1978-05-09 |
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