CA1268052A

CA1268052A - Measure while drilling systems

Info

Publication number: CA1268052A
Application number: CA000500578A
Authority: CA
Inventors: William Gordon Goodsman
Original assignee: Positec Drilling Controls Canada Ltd
Current assignee: Schlumberger Canada Ltd
Priority date: 1986-01-29
Filing date: 1986-01-29
Publication date: 1990-04-24
Anticipated expiration: 2007-04-24
Also published as: US4914637A; EP0448845A1; EP0448845B1

Abstract

ABSTRACT OF THE DISCLOSURE
In a fluid communication device such as a measure-while-drilling well-logging tool of the type in which the information concerning the downstream parameters that are measured is trans-mitted upstream, e.g. to the surface of the earth, in the form of positive pressure pulses in the drilling fluid, a pressure modula tor for generating the pulses is driven by the drilling fluid passing through the tool. The pressure modulator is controlled by a solenoid actuated latching means which has low power require-ments as compared to known measure-while-drilling logging tools.

Description

1~6~0S~ 71620-1 This inven-tion relates to a new or improved fluid com-munication device such as a well-logging tool, and in particular to a tool of the logging-while-drilling or measure-while-drilling (MWDl type. In measure-while-drilling tools, sensors or trans-ducers positioned at the lower end of the drill string continuous-ly or intermittently monitor predetermined drilling parameters such as temperatures or pressures, or directional, logging or mechanical parameters, and the tool transmits the appropriate information to a surface detector. Typically such MWD tools are positioned as one of the cylindrical drill collars close to the drill bit and utilize a system of telemetry in which the informa-tion is transmitted to the surface detector in the form of pres-sure pulses through the drilling fluid or drilling mud that is normally circulated under pressure through the drill string during drilling operations.
Prior art examples of measure-while-drilling tools are shown in United States Patents 2,787,795 Arps, 2,887,~98 Hampton, 3,309,656 Godbey, 4,279,620 Westlake e-t al, 4,001,773 Lamel et al, 3,964,556 Gearhart et al as well as in Canadian Patents 425,996, Hassler, and 959,825 and 978,175 granted to Mobil Oil Corporation.
Hitherto, the MWD well-logging tools that have been available have been large, complex, and expensive, and have suffered from numer-ous disadvantages. Thus, known ~WD tools have not been retriev-able through the drill string, and in order to recov~r such tools it was necessary to withdraw the drill string from the drill hole.
Such tools furthermore have recluired complex and expensive power systems and drive transmissions to power the signal means by which ~, , -- 1 --::: : -, ;: , . : .. -, ~. . I . . .-:
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~ Z ~ ~ ~ 71620-1 the desired in~ormation is transmitted. Since it i5 not economically feasible to run an electrical power supply cable through a drill string, tiliS in turn has entailed a requirement for bulky and expensive battery pac~s or turbine power generating systems to he included in the tool Such tools also had the disadvantage of being large metal structures requiring expensive heavy equipment to machine, assemble, test and transport them.
These problems are avoided by the improved MWD well-logging tool disclosed herein.

SUMMARY OF THE INVENTION
~ he present invention provides a remote sensing system comprising a tool for positioning at a predetermined location in a conduit through which a flow of ~luid is circulated, said tool including a pressure modulator adapted to transmit signals indicative of selected parameters existing at said location, such signals being in the form o~ positive pressure pulses transmitted through the ~luid to a remote receiver, said pressure modulator comprising a stator co-axially arranged in said tool and having angularly spaced channels therein that extend from an upstream end of the stator to a downstream end thereof to define passage means through which at least a portion o~ said fluid ~low is to be directed blocking means adjacent said stator and movable between an inoperative condition wherein it is positioned in non-restrictive relationship relative to said passage means, and an operative condition wherein it effects rapid, tempor~ry, at least partial restriction of said passage means to generate said positive pressure pulses, said blocking means comprising a rotor - .

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element rotatably mounted in the path of fluid flow and having angularly spaced radially projecting ribs thereon, said ribs in said operative condition occluding said passage means impeller means interacting with the fluid flow to apply a driving torque to said rotor said impeller means being directly coupled to said rotor so that the rotor is urged to follow angular movement of the impeller means latching means effective to retain said rotor in the inoperative condition against the driving torque applied to said rotor and electrical actuator means for said latching means said actuator means being selectively energisable to release said latching means and free said rotor to undergo incremental angular movements away from the inoperative condition to the operative condition and again to said inoperative condition under the influence of said driving torque.
The blocking means rotor is preEerably so designed that the drilling fluid flow applies a continuous torque to the rotor so that it is incrementally rotated -2a~

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each time it is released by a latching means, to effect restric-tion of the passage and generate the desired pressure pulse. The drilling fluid is preferably either directed through angled vanes in a stator within ~he tool to impart an angular momentum to the drilling fluid reaching the rotor or the vanes on a coupled impel-lar are angled to impart reactive torque to the rotor. Some of the force obtained by this change in direction of the drilling fluid flow is applied directly to the restrictor rotor which is controlled by the latching mechanism. Because of this direct coupling, there is no need to change -the mechanical energy of the drillin~ fluid ~low into electrical energy using electro-mechani-cal devices and electrical lower regulating circuits, and accord-ingly the mechanism required is not complex. Furthermore, the power requirements of the tool are low as compared to prior art tools, since the latching mechanism requires comparatively little power to cause a change in state, in contrast to arrangements wherein the change in restriction of a passage is effec-ted b~
mechanical means driven by generated electrical power. Since the direct coupling decreases the complexity and electrical power requirements of the tool as compared to known positive pressure MWD tools; the tool of the present invention should be of reduced cost and greater reliability.
The well-logging tool is preferably of elongated cylin-drical form and of such diameter that it can slide within the bore of a drill string from the surface to the desired deployment loca-tion, the lower end of the tool carrying a conventional mule shoe and stinger that can be centered in a conventional mule shoe : - . ,~, . .

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sleeve positioned at the lower end of the drill string. Alterna-tively, the instrument may be set on a conventional baffle plates if orientation parameters are not desi.red. There is preferably a flexible packer sleeve near the upper end of the tool, this packer being expandable into engagement with the internal bore of the drill collar so that the flow of drilling fluid is directed to pass within the interior of the tool. The seal may alternatively . and more easily be made by a ro4y Pa~ seal or 0-ring manufactured by Parker Seal Company or others in a groove on the outside dia-meter of the containment sleeve or reducer piece. This seal maybe slipped into a diameter reducing polish sleeve ir required, which would hang from the upper box end of -the collar into which the tool is inserted. The polish sleeve would hang by a larger diameter lip and would be sealed on the outside by Poly-packs or 0-rings in grooves in the polish sleeve. The upper end of the tool preferably includes a spear point assembly that can be engaged, lowered within the drill string, and released by a stan- ;
dard oil field "soft-release" tool. For retrieval, the top of the spear point is designed to be captured and retrieved by a standard oil field "overshot" tool lowered within the drill string by a cable to latch onto the spear point.
The invention will further be described, by way o-E
example only, with reference to the preferred embodi~ent thereof that is illustrated in the accompanying drawings wherein:
Figure 1 is a somewhat schematic view of a drilling installation for drilling a hole in an underground formation;
Figures 2A and 2B together constitute a longitudinal I r~de~ r t~

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sectional view of a first embodiment of a logging tool for use in the drilling installation of Figure l;
Figure 3 is a sectional view taken on the line III-III
in Figure 2B;
Figures 4 and 5 are sectional views taken on the lines IV-IV and V-V respectively in Figure 2A;
Figure 6 is an enlarged perspective view partly sec-tioned showing a detail of the tool seen in Figure 2B;
Figures 7 and 8 are perspec-tive views showing respec-tively a stator and a rotor as used in the tool shown in Figure 2A;
Figure 9 is an exploded perspective view showing a detail of the tool;
Figure 10 is a fragmentary perspec-tive view showing a detail of the tool;
Figure 11 is a fragmentary and partly sectioned perspec-tive view showing a further detail;
Figure 12 is a somewhat schematic perspec-tive view of a ratchet arrangement that can be used in the tools shown in Figures 1 to 11;
Figure 13 is a view similar to Figure 2A showing an alternative embodiment;
Figures 14A to 14E show individual components o-f the embodiment of Figure 13; and Figure 15 is a schematic view illustrating the func-tions performed by the well-logging tool.
Referring to Figure 1, a drilling rig 15 in known manner mounts a drive mechanism 16 that provides a driving to~que to a .

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drill string 17 the lower end of which carries a drill hit 18 for drilling a hole in an underground formation 19. Alternatively the bit may be rotated by a 'mud motor' which is powered by the action of the pressure or flow of the drilling fluid, such ~otor being at the bottom of the drilling string at the bit there- fore not requiring the drill string be rotated. This motor mechanism is frequently used for controlled directional drilling. As is well known, the drill string comprises a series of tubular drill col-lars that are successively interconnected and define a con-tinuous bore -through which a flow of drilling Eluid from a positive dis-placement pump 10 which has its flow variations smoothed by an accumulator or pulsation dampener 11, (as known in the drilling industry) is delivered to the bottom of the drill hole to cool the drill bit and carry away the cuttings which become entrained in the drilling fluid and pass upwards between the outside of the drill string and the surrounding wall of the drill hole.
In most drilling applications, it is important to moni-tor on a continuous or intermittent basis certain parameters of the drilling process such as the temperature direction and orien-tation at the bottom of the drill hole, the strain applied to thedrill collar, and various characteristics of the formation in which the drill is operating. For this purpose a well-logging tool 21 is provided within the bore of the drill string. The tool 21 is generally of elongated cylindrical form, and carries at its base a generally tubular mule shoe and stinger 22 which has a curved lower edge 23 the uppermost portion of which leads to an axially extending groove 24 which is engaged by a mule shoe pin 25 fixed in the wall of a tubular mule shoe sleeve 26. The mule shoe -~ ~ .

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sleeve 26 (which is illustrated only schematically) is a conven-tional element having external webs (not shown) that sit on a ledge of a short orientation sub and is fixed by set screws or the like. The sleeve 26 carries the pin 25 fixed thereto and extend-ing radially inwardly. When the tool 21 is lowered to the bottom of the drill string, the lower edge 23 of the mule shoe engages the pin 27 and causes the tool to rotate un-til the pin enters the axial groove 24, thereby fixing the orientation of the tool with respect to the sleeve 26. The weight of the tool 21 is borne by the engagement between the pin 25 and the upper end of -the groove 24. Alternatively mating shoulders could be provided on the mule shoe and mule shoe sleeve.
The upper end of the tool 21 is provided with a spear point assembly 28 by means of which the tool can be manipulated by a standard oil field "soft release" tool lowered on a cable within the drill string -to release the spear point when the tool has been placed into position, or an "over-shot"may be used to engage the spear point when the tool is to be retrieved and brought to the surface. The assembly 28 essentially comprises an axial shaft 29 having an enlarged head 30 suitably configured for engagement by the overshot tool.
At an intermediate point in the length of the shaft 29 are ~hree radially extending axially oriented webs 31 the outer ends of which meet a tubular containment sleeve 36. Suitable seals (not shown) are provided on the exterior of the sleeve 36 for engagement with the bore of the drill string collar. IF the difference in these diameters is great, a diameter reducing polish -:

sleeve 32 is interposed. As shown in ~igure 2A the upper end of the polish sleeve 32 is formed with an annular shoulder 33 that seats in a step (not shown) in the drill collar and carrles seals 34 on its exterior. In this case the containment sleeve 36 forms a seal 36a against the bore of the polish sleeve 32.
A stator 37 fixed in the sleeve 36 has at its lower end a counterbore 39. The form of the stator 37 is more clearly illustrated in relation to Figures 4 and 7, from which it can be seen that the stator comprises a cylindrical body from which extends a series of helically arranged vanes 42 the outer edges of which lie against and are fixed to the interior of the containment sleeve 36 so that the stator defines, with the containment sleeve, an arrangement of axially and angularly extending passages for -the flow of drilling fluid therethrough. As is clearly seen in Figure 7, the vanes 42 increase in thickness towards their lower ends so that the intervening passages become progressively more restricted towards their lower ends.
The lower end of the containment sleeve has fixed there-in an array of radial webs 43 carried on the tubular hub 44 of a reducer 45, these webs 43 defining passages for the outflow of drilling fluid from the lower end of the containmen-t sleeve 36. A
shaft assembly 46 is journalled to rotate with respect to the hub 44 and carries a rotary seal 47 at the upper end of the hub which seal is held do~n by the lower end of the rotor 49 to prevent the ingress of drilling fluid. An upper section 48 of the shaft assembly 46 projects into the counterbore 39 of the stator and carries adjacent to the lower end of the stator a rotor element 49 ''' ~ , which is more clearly illustrated in Figure 8. A compression spring 47a located on the shaft section 48 below rotor 49 presses the seal 47 firmly against the reduce.r hub 44. The ro-tor 49 is keyed to the shaft section 48 and is fixed by a fastener 50 to rotate with the shaft assembly 46 and has defined in the periphery thereof a series of generally axially extending channels 51 corresponding in number and spacing to the vanes 42 of the stator, the channels 51 being of progressively greater angular extent from the upper end of the rotor to its lower end, as is clearly seen in Figure 8. The channels 51 thus define spaced ribs 55 on the peri-phery of the rotor 49, and as can be seen from Figures 4, 7 and 8, the angular extent of the upper end 56 of the ribs 55 is suffi-cient to effect.ively occlude the lower end of the passages between the vanes 42 of the stator, when the rotor is turned to bring the ribs 55 into register with these passages. O-ring seals 52 prevent fluid flow between the rotor 49 and the shaft section 48.
The rotor 49 is supported by an annular shoulder 53 on the shaft section 48.
The reducer 45 flares outwardly in conical form below the hub 44 and forms a seating connected to the top end of a tubu-lar upper latch slee-~e 57a that in turn connects to a lower latch sleeve 57b the lower end of which is connected to a cylindrical solenoid housing 58 beneath which is connected a compensator housing 59. The lower end of the compensator housing 59 is in turn connected to a cylindrical barrel 60 to contaiM the electron-ic and power supply components (not shown) the bottom end of which barrel carries the mule shoe 22.

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The shaft assembly 46 is carried in spaced upper and lower bearings 61 located in the upper latch sleeve 57a. A
dampener assembly 62 is mounted near the upper end of the interior of the upper latch sleeve 57a and comprises a dampener driver 63 in the form of a cylindrical collar that is keyed to rotate with the shaft assembly 46, but is axially slidable with respect there-to. The collar 63 forms one end of a cylinder assembly 64 which coopera-tes with an annular piston 65 that is fixed with respect to the shaft assembly 46. In the wall of the latch sleeve 57a is fixed a pin 66 which projects radially inwardly and is received in a groove 67 in the collar 63. ~s is more clearly shown in Figure 10, the groove 67 extends around the periphery of the collar 63 in an oscillating manner, i.e. varying in its axial position. Thus upon rotation of the dampener assembly with the shaft 46, the interaction of the pin 66 in the groove 67 will cause the dampener assembly 62 to oscillate in the axial direction of the shaft, this oscillation (and hence the rotational movement oE the shaft assem-bly 46) being dampened by displacement of hydraulic fluid within the cylinder 64 from one side to the other of the piston 65. The dampener assembly 62 thus acts in the manner of a hydraulic damper.
The shaft assembly 46 is centered with respect to the latch sleeve 57a by means of the bearings 61, and is located a~ially with respect thereto by a pair of collars 68 positioned adjacent each of the bearings 61 as shown in Figures 2A and 2B.
The lowermost of the two bearings 61 is seated on a flang~ 70 at the top of the lower latch sleeve 57b. A lower : .:
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extension 71 of the shaft assembly 46 pro~ects downwardly into the lower latch sleeve 57b and is connected to a torsion drive assembly 72 which is in turn coupled to a latch arrangement 73 that will be explained in more detail below.
The shaft extension 71 is surrounded by a co~pression drive spring 74 which is compressed between a shoulder on the shaft and the upper side of a torsion drive element 75. As is more clearly seen in Figure 9, the torsion drive element 75 is of generally cylindrical form having a central bore 76 traversed by a diametrical slot 77. The lower shaft extension 71 ls received in the bore 76, a pin 78 on the shaft extension 71 being received in the slot 77. The torsion drive element 75 is received with clear-ance within the lower latch sleeve 57b and is constrained by the interaction of the pin 78 with the slot 77 to follow the rotation-al movements of the shaft assembly 46, althouyh not being fixed axially with respect thereto.
The latch arrangement 73 has a latch cage formed by generally cylindrical housing 79 received within the lower latch sleeve 57b imme~iately below the torsion drive assembly 72.
pair of diametrically opposed lugs 80 project downwardly from the underside of the torsion drive element 75. A second pair of diametrically opposed lugs 80 project upwardly from the latch housing 75. A flat resilient spring element 82 of hard rubber is positioned between the torsion drive element 75 and the latch housing 79, and has four radially projecting arms 83 each of which is positioned between a pair of lugs 80, 81 so that rotation of the torsion drive element 75 is transmitted to the housing 79 ,: . .; .. ~ . ' :
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through gripping of the arms 82 of the spring in between the lug pairs 80 and 81. The spring element 82 is o~ about ~0 to 70 duro-meter hardness, and may be of neoprene or another rubber suitable for use in the opera-ting temperatures encountered.
The latch arrangemen-t 73 will now be explained with particular reference to Figures 2B, 3, 6 and 11. As mentioned above, thP cylindrical housing or latch cage 79 is constrained to follow the rotation of the shaft assembly 46 by virtue of the torsion drive arrangement 72.
As seen in Figure 6, the cylindrical housing 79 of the latch arrangement comprises a tubular wall 84 to which are affixed a pair of spaced annular upper and lower rings 85 and 86 respec-tively, the lugs 81 being formed integrally with the upper ring.
Figure 6 illustrates the housing 79 with parts removed to show the interior detail. The housing 79 provides a hollow cylindrical cage, and fixed in the upper ring 85 are four downwardly proj~ct-ing pins 87 arranged at equal angular intervals around the longi-tudinal axis of the tool. Likewise, theré are four equiangularly spaced pins 88 projecting upwardly from the lower ring 86, the lower pins being offset angularly by ~5 with respect to the upper plns .
Within the solenoid housing 58 there is mounted a sole-noid 90 carried in a bore 91 and urged upwardly by a compression spring 92. An axially arranged rod 93 projects upwardly from the solenoid plunger and is slidably guided in a bore by which opens into an enlarged counterbore 95 that opens to the upper end of the solenoid housin~ 58. At the upper end o~ the solenoid rod 93 is ' .

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fixed a cross-piece 96 (Figure 11), and a helical compression spring 97 surrounding the rod 93 engages under the cross-piece 96 and urges the rod continuously upwa.rds. The cross-piece 96 sup-ports bearings 103 for a transversely arranged latching shaft 99 (see Figures 3 and 11). The shaft 99 is positioned within a dia-metrically arranged axiall.y extending transverse guide slot 100 formed in a sleeve extension 101 the upper end of ~he solenoid housing 58. The walls of -the guide slot are engaged by rollers 102 by means of which the shaft 99 is guided for movement axially of the tool, the interaction of the rollers with the guide slot preventing rotation of the shaft 99 and solenoid rod 93 about the axis of the tool. One end of the shaft 99 projects radially beyond the sleeve lOl to form a deten-t 99a lying in the path of movement of the pins 87, 88 of the latch cage 79. This shaf-t 99 is Eree to rotate in the rollers 102 and can rotate with respect to the cross-piece 96 in a bearing 103.
The spring 97 surrounding the solenoid rod 93 urges the shaft 99 upwardly to place the detent 99a in the path of movement of the upper pins 87 of the latch cage 79. In this position, when one of the upper pins 87 engages the detent, rotation of the latch cage 79, and hence of the rotor 49 to which it is connected through the shaft assembly 46, is prevented. When the solenoid 90 is energized, the rod 93 is drawn downwardly, moving th~ detent 99a out of the path of the upper pins 87 and into -the path of the lower pins 88 so that the latching cage 79, and hence the rotor 49, can rotate until one of the lower pins engages the detent, this rotation amounting to 45D. When the solenoid 90 is de-ener . .
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gized, the shaft 99 is moved upwards by the spring 97 to disengagethe lower pin 8~ and free the latch cage 79 for a further incre-mental rotation of ~5 until the next upper pin 87 is engaged.
The solenoid housing 58 protects the solenoid from the drilling fluid and is threaded to the lower end of the lower latch sleeve 57b and secured thereto in a fixed rotational orientation with respect to the stator 37 so that through the fixed orienta-tions of the various parts, the rotor 49 is in a predetermined rotational orientation with respect to the stator 37 when the solenoid 90 is de-energized. This predetermined orientation corresponds to a substantial alignment or registr~tion between the channels 51 in the rotor 49, and the passages between the vanes 42 of the stator 37 so that the resistance to flow of the drilling fluid through the rotor 49 is minimized.
The flow o~ drilling fluid passing through the upper end of the tool in a generally axially direction as indicated by the arrows in Figure 2A, is given an angular momentum by the vanes 42 of the stator as it passes thereover, and accordingly applies a torque to the rotor 49 as the drilling fluid passes through the channels 51 therein. However, as will be appreciated from the foregoing, the rotor 49 is not ~ree to rotate, since its rotation is closely controlled by the latch arrangement 73, and rotation is prevented when the detent 99a is in contact with one of the pins 87, 88 in the latch cage 79.
When the solenoid 90 is energized and the detent 99a is drawn downwardly to disengage from the upper pin 87, -the latch cage 79, and hence the rotor 49, are free to rotate through an - .: , . . , . -:: .: . . .
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angle of 45 until one of the lower pins 88 comes into engagementwith the detent 99a. The rotor 49 is thus arrested in a position wherein the broad upper end 56 of the ribs 55 substantlally com-pletely occlude the lower ends of the channels through the stator 37, this occlusion giving rise to a pressure pulse which travels through the drilling fluid and can be detected at the earth's surface.
In order to prevent the premature erosion of the modula-tor parts due to the high velocity impingemen-t of particles sus-pended in the drilling fluid, they are made of hard materials orcoated, diffused or scintered with hard materials such as titanium carbide. Special areas of concern are the bottom of the stator vanes 42, the top and sides of the ro-tor vanes 55, and the inside of the containment sleeve 36 enclosing these parts.
It is necessary to protect the internal co~ponents of the well-logging tool from the effects of the drilling fluid.
Thus the reducer, the upper and lower latch sleeves 57a, 57b, the solenoid housing, and the compensator housing are filled with oil.
The compensator housing 59 includes a compensator arrangement thereby the pressure of this oil is increased to correspond to the pressure of the surrounding drilling fluid as this increases when the tool 21 is lowered progressively deeper into the drill hole.
To this end, the compensator housing includes a cylindxical bore 110 the lower end of which has an opening 111 that communicates to the exterior of t~e tool 21 and the drilling fluid that surrounds it. Within the bore 110 is a spring-loaded piston 112. As the pressure of the drilling fluid surrounding the tool 21 increases, : ~ , ,:
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the piston 112 is pushed upwardly in the bore producing a compen~
sating increase in the pressure of the oil therein, and oE the oil contained throughout the interior spaces of the tool, these spaces communicating with the bore 110 through suitable passage means (not shown).
Beneath the compensator housing 59 is coupled a barrel arrangement 60 which contains the electrical powex supply and electronic controls (not shown) that are utilized to control the operation of the latch arrangement 73. A suitable passage 113 is provided in the compensator housing 59 to connect the control cables (not shown) between the solenoid 90, and the electronic controls, this passage also communicating the oil to the interior of the barrel 60 up to a bulkhead connector which excludes the pressure of the oil from the electrical power supply and electron-ics module and ensuring the oil pressure therein is equalized with the pressure of the exterior drilling fluid.
The compensator arrangement thus compensates for changes in pressure applied to the tool by the drilling fluid, due -to variations in depth at which the tool operates. As the tool is lowered, the increasing pressure of the surrounding drilling fluid will move the piston 112 to similarly pressurize the oil within the tool. If there is any air within the tool this will likewise be compressed.
The operation of the tool will now be described. The barrel 60 contains the interconnection system and various trans-ducers ~or the downhole parameters to be measured. The barrel will also contain a pressure transducer so that the tool can :: - . .

receive pressure signals Erom the earth's surface. LiXewise the barrel includes the measurement and control electronics and the power source for the system. These components are neither illus-trated or described in any detail herein, except with respect to the schematic diagram in Figure 15. These components are of known kind and do not form a part of the present invention. Re-ferring to Figure 15 therefore, tne required downhole parameters are meas-ured by suitable transducers 120 the signals from which are fed via a multiplexer 121 to a central processing unit 122 which con-10 trols actuation of the solenoid !~0, the system being energized bya power supply 123 which will be provided by a suitable electrical battery or power generating turbine assembly. Actuation of the solenoid controls the pressure modulator 125 (i.e. the positioning of the faces 56 of the rotor with respect to the passages in the stator) which generates the pressure pulse signals transmitted upwardly through the drill hole as represented by the line 126 in Figure 15 to a pressure transducer 127 on the drilling rig 15~
signals from the pressure transducer 127 being duly connected to a strip chart recorder 128 or other suitable decoding apparatus.
20 The readings from the strip chart recorder reveal the values of the downhole parameters that are being measured and make it possible to monitor the downhole conditions on a continuous or intermittent basis as required.
As has been mentioned above, the tool 21 i5 comparative-ly simple and less complex than other known tools for the same purpose, these advantages deriving primarily from the fact that the driving force for the pressure modulator 125 is derived .

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directly from the drilling fluid itself, and accordingly it is not necessary to provide the power supply and drive transmission that were previously included in such tools for this purpose. Instead, the pressure modulator is controlled merely by actuation of the latching mechanism 73, this in turn being effected by the solenoid 90. Because of this arrangement, there is no need to change the mechanical energy of the drilling ~luid flow into electrical ener-gy using electro-mechanical devices and electrical power regulat-ing circuits. Accordingly, ~ecause of the reduced complexity the tool 21 should have an improved reliability as comparecl to those previously used.
The dampener assembly 62 and the torsion spring 82 together cooperate to control rotation of the rotor 49 and of the latch cage 79 to prevent damage to the components of the latch assembly during operation thereof. Depending upon the angle of the blades 42 of the stator and the velocity and density of the drilling fluid, the torque applied to the rotor 49 and the associ-ated shaft assembly 46 and latch arrangemént 73 is comparatively small, the torque applied by the flow of drilling fluid would produce a very large angular acceleration of these parts if unrestricted, and this in turn would cause rapid wear and damage to the components of the latch arrangement 73, and in particular the interengaging parts of the detent 99a and the latch pins 87 and 88. If the angular acceleration applied to the assembly were left unchecked, the latch cage 79 would achieve a large angular velocity when released by the detent 99a, and even when turning through only ~5 might upon impact with the next pin 87, 8S

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produce sufficiently large stresses as to cause damage. Such stresses have to be reduced to remove the possibility of damage or fracture of the various components, since this would oE course cause tool failure and loss of signal. Even at a lesser level, such high speed impact might produce over time indentations in the pins of the latching cage which might prevent the detent 99a dis-engaging smoothly from these pins when the solenoid 90 is actuat-ed.
The dampener assembly 62, the operation of which is des-cribed in the foregoing, has the effect of limiting the angularvelocity that can be achieved by the rotor and main shaft assembly 46 so that the velocity with which the pins 87, 88 o~ the latching cage 79 engage the detent 99a is greatly reduced. The dampener assembly 62 also acts to minimize or reduce oscillation o~ the assembly once initial contact has been made between the detent 99a and the appropriate pin 87, 88.
Most of the remaining shock of the impact between the detent 99a and the pins 87, 88 is absorbed by the spring 82 that is positioned between the latch cage 79 and the torque drive ele-ment 75 as described in relation to Figure 9. The torsion spring82 provides a r ubber coupling that can deform elastically when stressed between the lugs 80 and 81 to absorb the peak load stresses that would otherwise be applied between the ~eten-t 99a and t~e pins 87, 88. Once the peak stress has been ~bsorbed, the spring 82 relaxes slightly, the total deflection of the spring in operation being relatively small, and amounting to no more than from about 2 to 5 o~ rotation. Accordingly, the required orien-, ::

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tation between the rotor 49 and the latch cage 79 can still be maintained quite accurately.
Since pump strokes from the positive displacement pump normally used in drilling may cause some variations ln instantane-ous flow rate, the rotor assem~ly may tend to resonate at the pump stroke rate or a harmonic or sub-harmonic thereof. This may be dampened somewhat by the dampener assembly 62 but there is some backlash play of the pin 66 in the slot 67 of the da~pener collar 63. To restrict this oscillation to acceptable levels (i.e. less than about 10 peak to peak) -there should be a one way ratchet mechanism, as shown in Figure 12, with stops every 10 or so.
This mechanism must be rotationally oriented so that it will not latch the impact torque and hold this peak torque between pins 87, 88 and the detent 99a which could mean the solenoid 90 would not have enough pull ~orce or the spring 97 would not have enough push force to take the detent 99a off the pins 87, 88.
As shown in Figure 12 the ratchet mechanism comprises a ratchet ring 130 that is fixed with respect to the lower latch sleeve 57b by means of a key 131 and is formed with a series of inwardly directed -teeth 132. In all there are forty teeth 132, although for simplicity in illustration, a lesser number is shown in Figure 12. With forty teeth, the stops are provided at angular intervals of 9O The ratchet ring 130 co-operates with a pawl 133 that is pivotally attached to the top face of the torsion drive element 75 and is urged to swing outwardly to engage the teeth by a torsion spring 134 carried on the lower shaft extension 71. The drive element 75 is rotated step-wise in the direction of the .:
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arrow 135 in angular increments of 45 (corresponding to the spac-ing between successive pins 87 and 88) each increment movin~ the pawl 133 past five of the forty ratchet teeth 132.
As will be appreciated by those skilled in the art, in the rotor-stator arrangement shown in Figures 2, 7 and ~, the fluid flow will generate Bernoulli forces which will tend to drive the rotor 49 towards the closed position in relation to the stator vane 42, and to resist rotation of the rotor away from this closed position. In the arrangement shown, the Bernoulli forces are overcome because of the large torque in the desired direction of rotation that is generated by the inclination of the stator vanes 42. This is because some high velocity fluid flows past the ou-ter diameter of the rotor vanes 55 in the gap between the rotor vanes and the containment sleeve 36 which both drags the vanes by fric-tion, and also causes reactive force as the fluid is forced to change direction as a resul-t of striking other blades. The rotor blades are shaped as they are so that the area 55a on the trailing edge of the rotor 49 is minimized to reduce the Bernoulli force, to straighten the flow as it moves down the rotor blades and to minimize backwards reactive force caused by the fluid that ~ets over the leading edge of the top face of the rotor striking the preceding vane. However, in order to guarantee enough force to cause the rotor to move from the closed position to the open posi-tion, a fairly high angle is required on the stator vanes causing an excessively high force in the desired direction when the rotor is in the open position which requires that the latching control parts be made stronger than one would like~ These parts include the actuating device (solenoid or motor mechanism), the shaft 99 . . .

and the bearings on it, the pin cage 73, the shock absorber spring 82, and the hydraulic dampener 62. Furthermore, -the reactive force which holds the rotor in the closed position against the appropriate stop in the latch cage tends to be relatively weak because of the design optimizations, and the rotor may tend to oscillate off the stop at the closed position due to fluctuations in the flow velocity which are normal with conventional equipment.
This reduces the average side of the pressure pulse. This problem may be overcome by use of the one way ratchet mechanism of Figure 12 to allow motion only in the desired direction.
The above described problems are also overcome by -the alternative embodiment of the rotor-stator arrangement as shown in F'igures 13 and 14. Referring to Figure 13, which is a longitudi-nal section of view equivalent to the upper portion of Figure 2A, a spear-point assembly 228 is formed integrally with the stator 237, and as before .ncludes at its upper end an enlarged head 230.
The shaft 229 merges into the hub of the stator 237 through a smooth transition section 229a. The vanes 242 of the stator extend radially outwardly and are attached to a cylindrical con-tainment sleeve 236. In contrast to the first described embodi-ment, in the embodiment of Figures 13 and 14 the stator vanes 242 are purely radial in form and do not lie at an angle to the axis of the assembly 228. The form of the stator 237 is ~ore clearly illustrated in Figure 14A.
The spear-point assembly 228 is in axial alignment with a shaft assembly 246 positioned below it, the chaft having a reduced diameter upper section 248 upon which is mounted a rotor 249 which is secured by a fastener 250 in threaded engagement with `' , ~ ,,~'' . :

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the upper end of the shaft section. Underneath a shoulder 248a, the rotor 249 is keyed to the shaft assembly 246 by a key 248c, and is sealed thereto by an 0-ring seal 248b. The form oE the rotor 249 is most clearly seen in Figure 14B. It includes a cylindrical hub 249a having an upwards projection 249b that is received within a counterbore 239 in the lower end of the stator.
The rotor 249 has a series of radially extending ribs 255 having flat lands 256 at the uppex ends thereof and separated by channels 251. It wlll be seen that the ribs 255 of the rotor are posi-tioned closely adjacent the lower end of the stator vanes 2~2 and can be rotated to a position to substantially block the lower ends of the passages between these vanes.
Surrounding the shaft assembly 246 beneath -the rotor 249 is a drive assembly 201 which comprises an impeller wheel 202 positioned co-axially of the shaft assembly 246 between an upper slip clutch element 203 and lower slip clutch element 204. The upper slip clutch element is most clearly shown in Figure 14C, the lower slip clutch element is most clearly seen in Fi~ure 14D, and the impeller wheel is most clearly seen in Figure 14E. Referring to Figure 14E it will be seen that the impeller wheel 202 comprises a central tubular sleeve 205-having an axially directed slot 206 opening from its upper end and a series of helical vanes 207 projecting outwardly from the external surface -thereofO
As seen in Figure 14C, the upper slip clutch element 203 is of generally cylindrical form and is received over the shaft assembly 246 and within the sleeve 205 of the impeller wheel 202.
A pin 208 pro~ecting radially from the outer sur~ace o~ the .

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element 203 is received within the slot 206 in the impeller wheel, and constrains the upper slip clutch element 203 to rotate with the latter, while accommodating relative axial movement between these two elements. The lower slip clutch element w~ich is most clearly shown in Figure 14D is of stepped cylindrical form and is received within a cup-shaped recess 204 at the upper end of the reducer 245. The clutch element 204 has a cylindrical bore 210 which receives the shift assembly 2~6. The element 204 is of stepped configuration having an enlarged lower section 211 and an upper tubular portion 212 between which is an annular shoulder 213.
Within the tubular sleeve 205 of the impeller wheel, surrounding the shaft assembly 246 and acting between the underside of the upper slip clutch element 203 and the upper end of the top section 212 of the lower slip clutch element 204 is a strong compression spring 212 formed by a series of Belleville spring washers 214 arranged back to back. The spring 214 acts to urge the annular top face 215 of the upper slip clutch element 203 into engagement with the lower face of the rotor hub 249a, and to urge the lower slip clutch element 204 downwardly into engagement with the recess 209 against a ledge 253 on the shaft 246.
The lower end of the sleeve 205 of the impeller wheel 202 rests upon a rotary seal 247 that is supported on the angular shoulder 213 of the lower clutch element 204 and on the upper face of the reducer hub. The impeller sleeve 205 is loaded downwards under its own weight and further by a light compression spring 216 positioned within the sleeve around the top section 212 of the lower slip clutch element.

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In operation, the flow of drilling mud passing downward-ly through the drill string enters the containment sleeve 236 and passes axially over the stator vanes 242. The flow passes the rotor 249, moves over the blades 207 of the impeller wheel 202 before passing out of the lower end of the containment sleeve.
The flow of the drilling mud over the vanes 207 imparts a torque sufficient to cause rotation of the impeller wheel 202 which accordingly rotates continuously as long as the flow of drilling mud passes thereover. Rotation of the impeller wheel 202 relative to the lower slip clutch element 204 and the reducer 205 is accom-modated by sliding engagement of the impeller sleeve 205 upon the seal 247. However, by virtue of the interaction of the pin 208 with the slot 206, the upper slip clutch element 203 is con-strained to~ follow the rotation of the impeller wheel 202. In turn, the friction engagement between the top face 215 of the upper slip clutch element and the underside of the rotor hub 249a imparts a torque to the latter urging it to rotate in the same direction as the impeller wheel. The rotor 249 however is fixed by means of -the key 248c to the shaft assembly 246, and according ly can rotate only when the shaft assembly is freed by operation of the latch arrangement 73, and even then rotates only incremen-tally with each actuation of the solenoid 90 to permit the detent g9a to disengage one of the upper pins 87 and move lnto engagement with the su~ceeding lower pin 88. It will be seen therefore that actuation of the solenoid 90 frees the shaft assembly 246 to rotate through an angular increment of 45 under the urging of the impeller wheel 202 to bring the top faces 256 of the rotor ribs .; . :
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255 into blocking position with respect to the passages between the stator vanes 242, and thus generate a positive pressure pulse in the flow of drilling mud. Upon de-energization of the sole-noid, another incremental rotation of 45 is carried out -to move the ribs 255 into a non-blocking position where -they offer minimum resistance to the flow of drilling mud.
Except when the solenoid 90 is energized ancl de-ener-gized as discussed above, the rotor 249 is held stationary by the latch arrangement 73. However, the impeller wheel 202 is rotated continuously by the flow of drilling mud, relative rotation between these two elements being accommodated by sliding engage-ment of the top face 215 of the u~per slip clutch element against the underside of the rotor hub 249a, and by sliding between the lower end of the impeller sleeve 205 upon -the seal 247.
The rotor drive arrangement illustrated in Figures 13 and 14 has significant advantages over that described in relation to Figures 2A, 7 and 8. Specifically, the stator 237 is straight and stream-lined thus reducing resistance to the flow of drilling mud. The rotor is of shorter axial length reducing the back reac tive force, and both the leading and trailing edges of the rotor ribs 255 are narrow to reduce the Bernoulli forces in either direction. The two slip clutch faces cause transference of torque from the impeller wheel 202 to the rotor 249 and the shaft assem-bly 24~, and the maximum torque -transferred is limited by the slip point of the clutch faces. The impeller blades are designed to be able to provide enough torque to the rotor at minimum flow rate of the drilling mud to overcome all the forces that arise and to J

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generate the required signal strength. These torque requiremen-ts are reduced by the design of the rotor 249 as compared to that of the earlier embodimerlt so that the strength and complexity of the other elements of the control mechanism can be corresponding reduced. E'or normal mud flow conditions, the ratchet arrangement of Figure 12 would not be required with the embodiment of Figures 13 and 14, except to limit oscillations which might occur in situ-ations where the fluid flow rate was very low and extremely vari-able.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A remote sensing system comprising a tool for positioning at a predetermined location in a conduit through which a flow of fluid is circulated, said tool including a pressure modulator adapted to transmit signals indicative of selected parameters existing at said location, such signals being in the form of positive pressure pulses transmitted through the fluid to a remote receiver, said pressure modulator comprising:
a stator co-axially arranged in said tool and having angularly spaced channels therein that extend from an upstream end of the stator to a downstream end thereof to define passage means through which at least a portion of said fluid flow is to be directed;
blocking means adjacent said stator and movable between an inoperative condition wherein it is positioned in non-restrictive relationship relative to said passage means, and an operative condition wherein it effects rapid, temporary, at least partial restriction of said passage means to generate said positive pressure pulses, said blocking means comprising a rotor element rotatably mounted in the path of fluid flow and having angularly spaced radially projecting ribs thereon, said ribs in said operative condition occluding said passage means;
impeller means interacting with the fluid flow to apply a driving torque to said rotor said impeller means being directly coupled to said rotor so that the rotor is urged to follow angular movement of the impeller means;
latching means effective to retain said rotor in the inoperative condition against the driving torque applied to said rotor; and electrical actuator means for said latching means said actuator means being selectively energisable to release said latching means and free said rotor to undergo incremental angular movements away from the inoperative condition to the operative condition and again to said inoperative condition under the influence of said driving torque.

2, A system according to claim 1 wherein said rotor is positioned axially adjacent one end of said stator, the number size and distribution of the stator webs and of the rotor ribs corresponding such that in the operative condition the passage means is substantially wholly occluded by said ribs and in the inoperative condition the passage means is not substantially occluded by said ribs.

3. A system according to claim 1 wherein said impeller means is in the form of a turbine wheel having angled blades projecting into the path of the fluid flow, said turbine wheel being coupled to drive said rotor.

4. A retrievable well-logging tool that is of elongate form and is adapted to be lowered through the interior of a drill string to a desired location to transmit signals therefrom to the surface through the drilling fluid, said tool having at the upper end thereof a spear point arrangement enabling lowering of the tool to a predetermined location in the drill string by a soft-releasing tool engaging therewith, said well-logging tool being subsequently retrievable by engagement of said spear point assembly by an overshot tool, said tool including a pressure modulator adapted to transmit signals indicative of selected parameters existing at said location, such signals being in the form of positive pressure pulses transmitted through the drilling fluid to a remote receiver on the surface, said pressure modulator comprising:
a stator co-axially arranged in said tool and having angularly spaced channels therein that extend from an upstream end of the stator to a downstream end thereof to define passage means through which at least a portion of said fluid flow is to be directed;
a rotor element rotatably mounted in the path of drilling fluid flow adjacent said stator and movable angularly between an inoperative condition wherein it is positioned in non-restrictive relationship with respect to said channels and an operative condition wherein it effects rapid, temporary, at least partial restriction of said passage means to generate said positive pressure pulses, said rotor element having angularly spaced radially projecting ribs thereon that pass alternately between said operative condition wherein they occlude said passage means, and the inoperative condition;
impeller means interacting with the fluid flow to apply a driving torque to said rotor, said impeller means having angled blades projecting into the path of the fluid flow to interact therewith so that the impeller is urged to rotate thereby, said impeller being directly coupled to said rotor;
latching means effective to retain said rotor in the inoperative condition against said driving torque; and electrical actuator means for said latching means said actuator means being selectively energisable to release said latching means and free said rotor to undergo incremental angular movements away from the inoperative condition to the operative condition and again to said inoperative condition under the influence of said driving torque.

5. A well-logging tool according to claim 4 wherein said latching means comprises a cage that is fixed to rotate with said rotor element, said cage having two sets of angularly spaced abutments, the abutments of the second set being arranged in opposed relationship to those of the first set and angularly offset with respect thereto, said electrical actuator means comprising a solenoid-actuated reciprocating rod that extends in the axial direction of the tool and carries a detent that projects into said cage, said detent being positioned in the path of rotation of the abutments of the first set when said latching means is in the engaged condition such that one said first abutment is engaged by said detent to support said rotor in its inoperative condition against rotation under the influence of the driving torque supplied through said impeller, such that when said detent is moved by actuation of said solenoid to disengage an abutment of said first set, it is moved into the path of the succeeding abutment of the second set, thereby to arrest the incremental angular movement of the rotor element in the operative condition of the blocking means.

6. A well-logging tool according to claim 5 wherein said two sets of angularly spaced abutments are provided in the form o axially extending protuberances arranged in opposed annular rings in said cage, said detent being in the form of a transverse shaEt carried on said solenoid actuated reciprocating rod and having a projecting shaft and adapted to engage said protuberances.

7. A well-logging tool according to claim 5, including dampener means operatively connected to said rotor element to prevent excessive acceleration thereof when disengaged by said latching means, said dampener means comprising a hydraulic damper having a piston fixed on a shaft that is coupled to said rotor and is slidably arranged in a cylinder that is mounted to rotate with said shaft and is adapted to be oscillated axially of a shaft upon rotation thereof, such oscillation producing flow of dampening fluid within said cylinder from one side of the piston to the other side and thus dampening such movement.

8. A well-logging tool according to claim 5 including a shock-absorbing spring arrangement operatively coupled to said latching means to absorb the impact of engagement of the latter.

9. A well-logging tool according to claim 5 including a shock-absorbing spring arrangement operatively coupled to said latching means to absorb the impact of engagement of the latter.

10. A system according to claim 1 wherein said rotor element is in the form of a turbine, said impeller means comprising peripherally spaced angled blades that are integral with said ribs and are adapted to be driven by said fluid flow.

11. A system according to claim 10 wherein said angularly spaced channels are defined between radially extending webs of said stator, said rotor being rotatably mounted co-axially of the tool adjacent one end of the stator, said rotor ribs at a spacing corresponding to that of said stator channels.

12. A system according to claim 11 wherein said actuator means comprises a solenoid that controls a reciprocating rod that extends in the axial direction of the tool and carries a detent that projects into said latching means.

13. A system according to claim 12 wherein said latching means comprises a cage that is fixed to rotate with said rotor, said cage having a series of equiangularly spaced abutments thereon, said detent being positioned in the path of rotation of said abutments when said latching means is in the operative condition, such that one said abutment is engaged by said detent to support said rotor against rotation under the influence of said fluid flow.

14. A system according to claim 13 wherein said cage contains a first and a second set of said abutments, the abutments of said second set being arranged in opposed relationship to those of said first set and angularly offset with respect thereto such that when said detent is moved by actuation of said rod to disengage an abutment of one set, it is moved into the path of the abutments of the second set thereby to limit the incremental angular movement of the rotor.

15. A system according to claim 14 wherein said first and second sets of abutments are provided by axially extending protuberances arranged in opposed annular rings in said cage, said detent being in the form of a transverse shaft carried on said reciprocating rod and having a projecting shaft end adapted to engage said protuberances in succession.

16. A system according to claim 1 including dampener means operatively connected to said rotor to prevent excessive acceleration thereof when disengaged by said latching means.

17. A system according to claim 16 wherein said dampener means comprises a hydraulic damper having a piston fixed on a shaft coupled to said rotor and sliding in a cylinder which is mounted to rotate with said shaft and is adapted to be oscillated 71620-l axially of the shaft upon such rotation, such oscillation producing flow of dampening fluid within said cylinder from one side of the piston to the other through at least one restriction, and thus dampening such movement.

18. A system according to claim 16 including a one-way ratchet mechanism coupled to said rotor element to prevent rotation thereof in the direction opposed to said single direction, said ratchet mechanism having a series of teeth sufficient in number as to limit possible angular oscillation of said rotor to less than about 10°.

19. A system according to claim 1, 2 or 3 further including a shock-absorbing spring arrangement operatively coupled between said rotor and said latching means to absorb the impact energy of engagement of the latching means.