Pulsing Apparatus for Downhole Use

Abstract

A pulsing apparatus for use in a conduit through which is flowing a liquid. The pulsing apparatus includes a housing in which is positioned a valve generally at the inlet of the housing, the valve controlling flow of fluid down a central passageway of the housing. There is also flow through an annulus of the housing formed in part by at least one rotor and one stator, the rotor rotating in response to fluid flow impinging on the vanes of the rotor. There is a second valve provided in the lower end of the housing through which flow can be intermittently interrupted to cause pressure pulses in the mud flow and hence in the conduit in which the pulsing apparatus is disposed, the second valve being operatively connected to the rotor.

Description

FIELD OF THE INVENTION

The present invention relates to flow pulsing apparatus for use in various applications, such as in down-hole operation in oil/gas wells, and in particular to a flow pulsing apparatus adapted to be connected in a drill string above a drill bit.

BACKGROUND OF THE INVENTION

In the drilling of oil and gas wells as well as other downhole activities, it is common to use a downhole system which provides a percussive or hammer effect to the drill string to increase drilling rate and/or minimize sticking of the drill string in the borehole. In typical drilling operations, a drilling fluid or mud is pumped from the surface, through the drill string and exits through nozzles in the drill bit. The fluid flow from the nozzles assists in dislodging and cleaning cuttings from the bottom of the borehole as well as carrying the cuttings back to the surface.

Pulsing apparatuses for wellbore activities are well known as exemplified by U.S. Pat. Nos. 2,743,083; 2,780,438; 5,190,114; and 6,279,670. In general, the flow pulses are achieved by periodically restricting flow to produce pressure pulses. The pressure pulses are translated along the drill string causing the drill string to vibrate in a longitudinal direction, the net result being a percussive effect along the length of the drill string.

It is also common in addition to using the pulsing apparatus to incorporate a pressure-responsive tool in the drill string which expands or retracts in response to the varying fluid pressure pulses created by operation of the pulsing apparatus. This expansion/retraction motion provides the desired percussive effect at the drill bit. Such an apparatus may be in the form of a shock sub or tool and, may be provided above or below the pulsing apparatus or in certain cases can form part of a pulsing apparatus.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a downhole pulsing apparatus which can be used to impart periodic, longitudinal movement in the drill string which can be transferred to the drill bit.

In another aspect, the present invention provides a pulsing apparatus wherein fluid flow through the apparatus can be modulated to control the fluid flow pattern through the pulsing apparatus.

In still a further aspect, the present invention provides a method of imparting pressure pulses to a drill string wherein the frequency of the pulses can be controlled.

These and further features and advantages of the present invention will become apparent from the following detailed description, wherein reference is made to the figures in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically depicts a drill string including typical drill string components drilling a deviated borehole.

FIG. 2A is an elevational view, partly in section, showing the first, upper end of one embodiment of the pulsing apparatus in accordance with the present invention.

FIG. 2B is a view similar to FIG. 2A showing the second, lower end of the pulsing apparatus of FIG. 2A.

FIG. 3 is an enlarged view showing a portion of the pusling apparatus shown in FIG. 2A.

FIG. 4 is a cross-sectional view taken along the lines 4-4 of FIG. 3.

FIG. 5 is an enlarged view of the lower portion of the pulsing apparatus of FIG. 2B.

FIG. 6 is a cross-sectional view taken along the lines 6-6 of FIG. 5.

FIG. 7 is a cross-sectional view taken along the lines 7-7 of FIG. 5.

FIG. 8 is a plan view taken along the lines (8)-(8) of FIG. 5.

FIG. 9 is a partial elevational view, partly in section, showing the flow of fluid through a portion of the pulsing apparatus depicted in FIG. 8.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

While the invention will be described with respect to its use in a drill string having a downhole motor, it is to be understood that it is not so limited. It can be used in other downhole operations, e.g., drilling with tubulars, or in any other downhole operation involving a tubular string through which a fluid is flowing. Thus the pulsing apparatus of the present invention can be used in work strings, fracking operations, etc.

Referring then to FIG. 1, there is shown an earth borehole 10 having a vertical leg 12 and a horizontal leg 14. Extending from a derrick, mast, or the like 16 at the surface is a drill string shown generally as 18. String 18 has a series of bottomhole components comprising a drill bit 20 driven by a downhole motor 22. String 18 also includes a measurement while drilling (MWD) module 24 which can include a steering tool and other sensors commonly employed to determine downhole parameters. Upstring of MWD module 24 is the pulsing apparatus 26 of the present invention, above which is directly positioned a shock sub 27. The positioning of the pulsing apparatus 26 and the shock sub 27 will vary depending on the nature of the borehole.

Turning now to FIGS. 2A and 2B, the pulsing apparatus 26 comprises a housing shown generally as 28 having a first, upper end 28A and a second, lower end 28B. Housing 28 is comprised of a series of threadedly connected subs, namely a first, upper sub 30, a second sub 32 and a third sub 34. Sub 30 is connected at its upper end to a drill string element 29 which can be a portion of the drill string, a sub, another tool, etc. Lower sub 34 is also threadedly connected to a drill string component 36.

As used herein, and with respect to pulsing apparatus 26, the terms “upper,” “lower,” “up,” “down,” and similar terms are used with respect to the orientation of the apparatus in an earth borehole.

The pulsing apparatus 26 further includes a first valve assembly shown generally as 40 and described more fully hereafter, valve assembly 40, in part, forming a first stator shown generally as 41 and also described hereafter. Below valve assembly 40 is rotatably mounted a first rotor shown generally as 42 also described more fully hereafter. There is a second stator shown generally as 44 positioned below rotor 42 and above a second rotor shown generally as 46. There is a second valve assembly shown generally as 50 which is positioned in housing 28 below second rotor 46.

Referring now to FIGS. 2A, 2B, 3, and 4, the upper, first end of pulsing apparatus 26 is shown in greater detail. An annular, externally threaded nipple 52 is threadedly received in an internally threaded bore 54 in sub 30, sealing between sub 30 and nipple 52 being effected by an o-ring seal 56 received in an o-ring groove on the interior wall of sub 30. As best seen in FIG. 3, valve assembly 40 comprises a valve body 58, an annulus 61 being formed between valve body 58 and the inner wall of nipple 52. A plurality of circumferentially spaced, fixed, angled vanes 60 in annulus 61 connect valve body 58 to nipple 52. Valve body 58 comprises an annular wall 64 and a frustoconical wall 66, frustoconical wall 66 defining a circular opening forming an inlet 68 to valve body 58. Mounted in valve body 58 is a concical shaped plug 70 connected to a spindle 74, spindle 74 being reciprocally mounted in a sleeve bearing 76. There is a bushing 78 threadedly received in the lower end of annular wall 64 of valve body 58. Bushing 78 comprises an outer, annular wall 78A, and an inner central concentric wall 78B, inner wall 78B forming a bearing housing for bearing 76. An axially upwardly facing, annular shoulder 80 is formed on the upper end of inner wall 78B. A compression spring 79 is connected to the underside of valve plug 70 and is in surrounding relationship to spindle 74. In the position shown in FIG. 2A, conical valve plug 70 substantially blocks valve inlet 68. However, in the position shown in FIG. 3, and under the influence of fluid pressure acting against conical valve plug 70, spring 79 is compressed increasing the flow area between conical valve plug 70 and valve inlet 68. Accordingly, in the position shown in FIG. 2A, there is essentially no flow through valve 40, while in the position shown in FIG. 3 fluid flows through valve 40. To this end, bushing 78 defines a valve outlet 82.

As seen in FIG. 3, when sufficient fluid pressure caused by mud flow down the drill string from a mud pump (not shown) at the surface is reached, valve 40 opens and there are essentially two flow paths, i.e. a generally central flow path through valve 40 and a radially outer flow path through annulus 61. It will be recognized by those skilled in the art that vanes 60 act as static guide vanes or nozzle vanes which accelerate and add swirl to the incoming fluid/drilling mud and direct the flow to the vanes of first rotor 42 as discussed hereafter.

There is a thrust bearing 90 positioned adjacent the lower end of threaded nipple 52.

Rotatably journaled in pulsing apparatus 26 is first rotor 42. Rotor 42 comprises a tubular, central core portion 94 having a central passageway 96. Passageway 96 communicates with a plurality of angled ports 106 for a purpose described hereafter. Rotor 42 also comprises a radially outward annular sleeve portion 98 connected to and rotatable with core portion 94, an annulus 100 being formed between core portion 94 and sleeve portion 98. As seen in FIG. 3, connecting core portion 94 and sleeve portion 98 are a plurality of circumferentially spaced, angled vanes 102. The swirling mud flow induced by stator vanes 60 impinges on vanes 102 resulting in rotational motion of first rotor 42. As well, flow of mud exiting ports 106 from passageway 96 also impinges on vanes 102 resulting in rotation of first rotor 42. A radial sleeve bearing 89 is positioned in counterbore 91 in surrounding relationship to sleeve portion 98.

Central core portion 94 of rotor 42, as best seen in FIG. 2A, includes an axially downwardly extending shaft portion 108 which projects toward second, lower end 28B of housing 28. Shaft portion 108 is received in an axial bore 110 in the central core portion 111 of a second rotor 46 and is connected thereto by a pin 112 received in registering bores in shaft portion 108 and central core portion 111 of rotor 46, thereby rigidly connecting rotor 46 to rotor 42 for rotation therewith.

Sleeve portion 109 of rotor 46 is connected to core portion 111 by a plurality of circumferentially spaced vanes 114 positioned in an annulus 121 between core portion 111 and sleeve portion 109. Fluid flow in the annulus 121 impinging on vanes 114 induces rotation of rotor 46 in a similar manner as discussed above with respect to rotor 42.

The central core portion 111 of rotor 46 has an upper, axially facing surface 118, while central portion 94 of rotor 42 has an annular, axially downwardly facing shoulder 130. Disposed between shoulder 130 and the axially upwardly facing surface 118 of rotor 46 is a second stator 44. Stator 44 carries upper and lower thrust bearing assemblies 140 and 142 respectively and includes a central core portion 150 and a radially outwardly spaced sleeve portion 152 thereby forming an annulus 154 therebetween. Interconnecting core portion 150 and sleeve portion 154 are a plurality of circumferentially spaced, fixed, angled vanes 156, vanes 156 acting in the same manner as described above with respect to vanes 60 of first stator 40 as a result of fluid flow in annulus 154.

As seen in FIG. 2B, there is a central passageway 180 formed by sleeve portion 109, passageway 180 being in open communication with a generally radially outwardly angled flowport 181 having a funnel shaped mouth 182 formed in a threaded fitting 183 which is threadedly received in a threaded interior socket of sleeve 109, fitting 183 rotating in a clockwise direction as indicated by the arrow R shown in FIG. 5.

Since flowport 181 exits fitting 183 through an exit opening 194 off-center, as rotor 46 rotates concentrically, flowport 181 moves in an eccentric path. Connected to the lower end of fitting 183 by a threaded bolt 196 is a plate 198 through which extends an opening 200 which is also off-center with respect to the centerline of plate 198. As seen in FIG. 5, opening 200 is in open communication with exit opening 194 from flowport 181. Thus, as rotor 46 rotates, opening 200 also rotates in an eccentric pathway.

There is a second, annular plate 210 which is connected to a threaded fitting 212 received in a threaded female receptacle in sub 34. In this regard, as seen in FIG. 5, plate 210 and fitting 212 have registering bores, offset from the centerline, in which is press fitted a slotted tubular pin 214. Plate 210, as seen in FIGS. 5 and 7, has an offcenter opening 220, opening 220 being in open communication with a passageway 222 which in turn is in open communication with a central fluid passageway 224, passageway 224 defining an exit for fluid passing through pulsing apparatus 26 in a downhole direction.

As best seen in FIG. 6, opening 220 is generally crescent-shaped. More specifically opening 220 has a modified crescent shape comprised of a generally semi-circular portion 230 which extends from about point A to about point B, a straight portion 232 which extends from about point C to about point D, a first arc portion 234 which extends between point A and point C and a second arc portion 236 which extends between point B and point D. Opening 220 can also be described as bean-shaped, kidney-shaped, etc. As seen in FIG. 5, the passageway defining opening 220 has a first, upper, vertical wall portion, the wall surface being generally parallel to the long axis of the pulsing tool 26, and second lower skirt portion 252 which, as seen in FIG. 5, flares outwardly from the intersection of skirt portion 252 with upper portion 250.

FIGS. 8 and 9 show a modified version of opening 220 as indicated by the section lines (8)-(8). Turning then to FIGS. 8 and 9, it can be seen that crescent-shaped opening 220A has a chamfered lip portion 254 extending from the upper surface of plate 210A downwardly, chamfer 254 extending for approximately a peripheral distance determined by points A and C. In all other respects, as seen in FIG. 9, the passageway forming opening 220A is the same as described above with respect to opening 220.

As can be best seen by comparing FIGS. 5 and 6, at all times there is some overlap between fixed opening 220 and eccentrically rotating opening 194. This ensures that at all times while the mud pumps are operating, there is fluid flow through the drill string. It will also be appreciated that as rotor 46 rotates, the degree of overlap between openings 220 and 194 will vary, resulting in flow changes and hence pressure pulses resulting in pulsing of mud passing through pulsing apparatus 26.

In operation, but prior to the mud pumps being turned on, there would of course be no flow through pulsing apparatus 26. However, activation of the mud pumps forces drilling mud or fluid down the drill string. When the pressure of the flowing mud reaches a predetermined pressure, valve 40 opens, the degree of opening depending upon the pressure of the mud and the spring force of the spring 79. At the same time, and as can be seen from the above description, there is also flow through an annular path defined primarily by the annuli formed by the rotors and stators. Thus, the above referenced central flow path, at least in part is formed by passageways 96 and 180.

The angles of the vanes in rotors/stators can vary to at least partially control the velocity of the mud through the annular flow path. Thus, all the vanes of all the rotors/stators can be at the same angle or at slightly different angles. Likewise, flow through the central passageway commencing with valve 40 is controlled not only by mud pump pressure but also by the spring force of spring 79 determined by the spring constant.

It will also be appreciated that the plug valve, i.e., valve 40 can be used to more readily control flow through the central passageway of the first stage to the second stage of the pulsing apparatus 26. In this regard, the conical shape of valve plug 70 coupled with the valve inlet 68 being formed by a frustoconical wall ensures greater throttling control of fluid flow through the central passageway. This is important since speed of rotation of the rotors in the pulsing apparatus 26 is primarily a function of flow through the annular flowpaths. To control rotation, and hence frequency of pulsing, that flow must be modulated which is accomplished by valve 40.

Although the application has been described above with respect to a two-stage pulsing apparatus, a stage being a stator and a rotor, it is to be understood that it is not so limited. The pulsing apparatus could include only one stage, two stages as described, or more stages. Furthermore, it will be recognized that the stator vanes impart a spiraling flow path which ensures the fluid impinges on the rotor vanes at the optimum angle of attack.

It will be understood from the above description that flow exiting pulsing apparatus 26 is in the form of a series of pressure pulses. These pressure pulses are used to provide a percussive action along the axis of the drill string 12. Furthermore, the fluctuations in the drilling fluid flow rate at drill bit 20 provide for effective cleaning of cuttings from the drill bit during the drilling operation.

The pressure pulses may also be used, as is well known to those skilled in the art, to operate shock subs or to move a reciprocating mass which impacts on an anvil, with the aim of providing a percussive or hammer action to a system drilling in hard rock. Shock subs useful with the pulsing apparatus of the present invention are well known to those skilled in the art.

In addition to its uses in drilling, the pulsing apparatus of the present invention can be used in such operations as: (a) reducing friction in drilling operations; (b) shaking of tubing to clean screens; (c) vibrating of cement during cementing operations; (d) pulsating fluid being pumped into a formation to fracture it; (e) enhancing the fishing operation through inducing impulse vibration to the drill string.

Although specific embodiments of the invention have been described herein in some detail, this has been done solely for the purposes of explaining the various aspects of the invention, and is not intended to limit the scope of the invention as defined in the claims which follow. Those skilled in the art will understand that the embodiment shown and described is exemplary, and various other substitutions, alterations and modifications, including but not limited to those design alternatives specifically discussed herein, may be made in the practice of the invention without departing from its scope.

Claims

1. A downhole pulsing apparatus comprising:

an elongate tubular housing having a first end and a second, there being an axial fluid flow pathway through said housing;

a first valve disposed proximal said first end of said housing to at least partially control the flow of fluid through said housing, said first valve having a valve inlet and a valve outlet;

at least one vaned stator having a plurality of circumferentially spaced, angled first vanes to direct fluid entering said first end of said housing in a spiral pattern;

at least one vaned rotor rotatably mounted in said housing below said at least one stator, said rotor having a central fluid passageway in fluid communication with the outlet of said valve, said rotor having a plurality of circumferentially spaced, angled second vanes rotatable with said rotor, flow from said stator impinging on said rotor vanes resulting in rotation of said first rotor;

a second valve mounted in said housing, said second valve having first and second valve members, each of said valve members having first and second axial flow openings, respectively, said first valve member being rotatable around a longitudinal axis through said housing, said second valve member being fixed, rotation of said first valve member varying the alignment of said first and second openings between a minimum open area and a maximum open area to provide a an intermittently varying flow and pressure exiting said second end of said housing.

2. The pulsing apparatus of claim 1, wherein said first valve member is operatively connected to said first rotor for rotation therewith.

3. The pulsing apparatus of claim 1, wherein there are a plurality of said rotors.

4. The pulsing apparatus of claim 3, wherein there are a plurality of stators, respective ones of said rotors being positioned below respective ones of said stators.

5. The pulsing apparatus of claim 4, wherein said first valve member of said second valve is operatively connected to the rotor most proximal said second end of said housing.

6. The pulsing apparatus of claim 1, wherein said first valve comprises an annular valve body, said annular valve body defining said valve inlet, and a valve element mounted in said valve housing, said valve element comprising a valve plug connected to a compression spring, said valve plug substantially preventing fluid flow into said valve inlet when said spring is in a relaxed position, fluid flowing through said housing acting on said valve plug to compress said spring and increase the flow through said valve inlet.

7. The pulsing apparatus of claim 6, wherein said valve plug is conically shaped.

8. The pulsing apparatus of claim 1, wherein said at least one rotor comprises a first central core portion in surrounding relationship to said central passageway and a first outer sleeve, a first rotor annulus being formed between said first central core portion and said first outer sleeve, said second vanes being disposed between and interconnected to said first central core portion and said first outer sleeve.

9. The pulsing apparatus of claim 8, further comprising a plurality of angled ports in open communication with said central passageway and said first rotor annulus.

10. The pulsing apparatus of claim 8, wherein said first central core portion of said at least one rotor is connected to a second rotor for rotation therewith, said second rotor comprising a second central core portion and a second outer sleeve, a second rotor annulus being formed between said second central core portion and said second outer sleeve, the vanes of said second rotor being disposed in said second rotor annulus.

11. The pulsing apparatus of claim 8, wherein said central core portion includes an axially extending shaft portion and said second rotor has an axially extending bore for receipt of said shaft.

12. The pulsing apparatus of claim 11, wherein said shaft is connected to said second central core portion by a pin received in registering holes in said shaft and said second central core portion.

13. The pulsing apparatus of claim 6, wherein said valve body has a generally cylindrical portion and a generally frustoconical portion, said frustoconical portion defining said valve inlet.

14. The pulsing apparatus of claim 1, wherein said second axial flow opening in said second valve member is generally crescent-shaped when viewed in plan view.

15. The pulsing apparatus of claim 14, wherein said generally crescent-shaped opening forms the mouth of a passageway extending through said second valve member, said second valve member comprising a disc-shaped plate having an upper surface proximal said first valve member, said passageway through said second valve member having a chamfered lip portion extending from said upper surface into said passageway, said lip portion extending for a portion of the periphery of said crescent-shaped opening.

16. The pulsing apparatus of claim 1, wherein said first valve member comprises a second disc shaped plate.