APPARATUS FOR INDUCING VIBRATION IN A DRILL STRING

Abstract

An insert having a plurality of ports creating angled passageways through the walls of the insert is positioned in a drill string for altering fluid flow in the drill string and inducing vibration sufficient to speed up directional drilling and to prevent differential sticking in wellbores. Boundary layer flow along the walls of the drill string is drawn into an upstream group of ports to commingle with fluid in the central bore of the drill string and the insert. The flow is separated at a downstream group of ports and angled passageways cause the flow to be directed radially outward inducing vibration into the drill string.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is a regular application claiming priority of U.S. Provisional Patent application Ser. No. 60/582,064 filed Jun. 24, 2004, the entirety of which is incorporated herein by reference.

FIELD OF THE INVENTION

Embodiments of the invention relate to apparatus which acts to induce a vibration into a drill string during drilling operations and, more particularly, to aid in advancing the drill string and drill bit, particularly when drilling horizontal wellbores.

BACKGROUND OF THE INVENTION

It is known in drilling wellbores, and particularly, horizontal wellbores that inducing vibration in the drill string during drilling aids in advancing the bit through the formation. In horizontal wellbores, the gravity influence on moving the drill string downhole decreases and the weight lying against the low side of the borehole increases as the inclination angle increases, creating large frictional forces as the drill string is mechanically forced into the wellbore. Vibration acts to reduce friction between the drill string and the borehole permitting the drill string to move more freely therein.

Further, cleaning of the wellbore becomes more difficult as the inclination angle increase. The cuttings tend to accumulate along the lower side of the wellbore, about the drill string and create a situation wherein the drill string is prone to sticking in the wellbore.

Further, differential sticking of drill pipe is a common problem found in both vertical and horizontal drilling. Differential sticking is defined as a drill pipe being stuck in a wellbore caused by a differential between the formation pressure and the hydrostatic pressure in the wellbore. Typically, this situation occurs during overbalanced drilling where a permeable zone exists over which a thick layer of filtercake is deposited and there is contact between the drill pipe or drill collars and the filtercake. Other factors which may contribute to differential sticking are prolonged periods where the drill pipe is stationary, the length of the permeable zone, the filtercake thickness, the drilling mud type and the drilling mud properties. Conventionally differential sticking is resolved by jarring or rotating the drill pipe to attempt to free the drill pipe from the filtercake bond, chemically altering the filtercake properties and introducing nitrogen into the well in an attempt to reduce the hydrostatic pressure.

Vibration may be induced into a drill string using mechanical means to provide pulses of mechanical energy to the drill string. U.S. Pat. No. 4,384,625 to Roper et al. teaches the use of mechanical vibrators, such as hydraulically driven vibrators, incorporated into a drill string to vibrate the drill string at a suitable frequency and amplitude to reduce friction.

U.S. Pat. No. 4,243,112 to Sartor teaches a fluid-,driven rotary orbit jet reaction-type vibrator which is driven by a compressible fluid. The vibrator fits closely between a cover plate and a bearing surface and orbits about in a race so as to exert an orbiting radial vibrator force sequentially in all radial directions.

U.S. Pat. No. 6,009,948 to Flanders et al. discloses a resonator hydraulically operated by a fluid circulated from surface or by an electromechanical device such as a motor or a solenoid which imparts pulses of mechanical energy to aid in drilling, to free stuck drill string and to aid in cementing operations.

One disadvantage of the prior art devices is their complexity and the lack of access to permit passage of a wireline therethrough.

Ideally, a vibration inducing device is simple, inexpensive and is readily incorporated into a drill string without impeding operations integral to drilling.

SUMMARY OF THE INVENTION

Embodiments of the invention use shock turbulence interaction created by positioning a venturi insert in a flow of fluids in a drill string to create vibrations in the drill string which are sufficient to free a stuck drill pipe or reduce a high frictional coefficient between the drill string and the wellbore to assist in drilling operations.

In a preferred embodiment, a venturi insert having a plurality of angled passageways extending from ports in both an upstream and a downstream wall and a central bore, directs boundary fluid flow into the central flow at the upstream end and directs fluid at the drill string as it exits the downstream passageways which causes vibration therein. The venturi insert is preferably mounted in a bore of a pup tool which is threadedly engaged in the drill string. An inner sleeve and end rings are used to position the insert in the fluid flow. The insert is constrained from lateral movement however it is axially moveable within the pup tool in the sleeve and may be caused to spin therein. A snap ring retains the sleeve, insert and retainer rings in the pup tool. The sleeve is supported at a downstream end by a shoulder formed in the bore of the pup tool.

Therefore in a broad aspect, a vibration inducing apparatus for controlling fluid flow within a bore of a drill string for creating vibration within said drill string comprises: a venturi insert fit to the drill string's bore and being axially moveable therein, the venturi insert having a body fit to the bore and having a central tubular bore formed therethrough for forming an annular wall extending between the drill string and the tubular bore; and a tubular fluid inlet formed in the insert's tubular bore projecting upstream from the annular wall; a tubular fluid outlet formed in the insert's tubular bore projecting downstream from the annular wall; wherein the annular wall comprises: a first angled wall extending downstream between the tubular fluid inlet and the body and radially outwards therefrom; a second angled wall extending downstream between the body and the tubular fluid outlet and radially inwards therefrom; and a plurality of ports formed in the first and second angled walls, the ports forming angled passages being directed radially inwards and downstream and radially outwards and downstream; wherein at least a portion of the fluid flows through the insert's angled passages and at least a portion of the fluid flows through the bore, the turbulence and pattern of the flow created upon exiting the insert inducing vibration in the drill string.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial section view of a vibration apparatus according to an embodiment of the invention, illustrating a venturi insert fit within a pup joint housing for connection to a drill string;

FIG. 2 is a perspective view of the venturi insert for the vibration apparatus according to FIG. 1;

FIG. 3 is a partial longitudinal sectional view of the venturi insert for the vibration apparatus according to FIG. 2, detailing the inner pipe, one of a plurality of annular wall ports and the fluid flow therethrough;

FIG. 4 is a longitudinal section view of the pup joint housing according to FIG. 1; and

FIGS. 5a-c are longitudinal sectional views of an internal sleeve of the vibration apparatus and upper and lower sleeve retainer plates fit within the pup joint housing. More particularly,

FIG. 5a is a longitudinal sectional view of the internal sleeve and retainer rings in the pup joint housing;

FIG. 5b is a sectional view of the upper sleeve retainer ring; and

FIG. 5c is a sectional view of the lower sleeve retainer ring; and

FIG. 6 is a partial section view of a vibration apparatus according to FIG. 1 illustrating a wireline passing through the bore of the venturi insert in the pup joint housing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As known to those skilled in the art, flow through a conduit, including flow through a drill string, is typified by a faster flow in a center flow stream and slower flow along the conduit wall; the boundary layer flow. As described in Technical Monograph 41—Understanding IEC Aerodynamic Noise Prediction for Control Valves by Floyd D. Jury at www.iceweb.com.au/Technical/ValveNoise.htm, noise generated downstream of a valve can come from the dissipation of mechanical energy in the fluid stream at a vena contracta of the valve. The primary noise mechanism is due to turbulence downstream of the vena contracta and is called turbulent shear flow. As flow becomes more intense due to the higher pressure drop across the valve, the normal shock begins to move further downstream and breaks up into several small shock cells. From each of the shock cells, shock waves are formed which travel downstream at some angle from the centerline. The shock waves bounce off the walls of the pipe and are reflected across the pipe to reflect off the opposite wall. As the reflected shock waves “bounce” down the pipe, the waves pass through the area of turbulence creating noise energy and impart vibration into the pipe wall. This is called “shock-turbulence interaction”. While typically this knowledge is used to reduce noise and vibration caused by flow restrictions through valves, in contradistinction, in the case of the present invention, the knowledge is combined with the knowledge of fluid flow through a conduit to create a vibration in a drill string to aid in drilling a wellbore.

Having reference to FIG. 1, in embodiments of the present invention, a vibration inducing apparatus 1 comprises at least one venturi insert 10 positioned within a drill pipe or drill string 11 to create a turbulence in a flow of fluid F through the drill pipe 11. The insert 10 is positioned in the drill string 11 such that venturi flow of fluid F′ through a plurality of ports 12 in the venturi insert 10 is caused to exit from the insert 10 so as to create shock-turbulence interaction with the drill pipe 11 resulting in a vibration of the drill pipe 11. Means 13, used to position the venturi insert 10 in the drill pipe 11, are such that little to no interference is created to the fluid flow F, F′.

More particularly, as shown in FIGS. 1-5c, and in preferred embodiments, the vibration inducing apparatus 1 comprises a housing 20, such as a tubular pup joint, adapted for positioning within at least a portion of the drill string 11, the tubular pup joint 20 fit having a central tubular bore 21 formed therethrough being substantially coaxial and contiguous with a bore 22 of the drill string 11. The at least one venturi insert 10 is positioned within the central tubular bore 21 and, as shown in FIG. 2, has body 23 having a tubular bore 24 formed therethrough being coaxial with the tubular pup joint's central tubular bore 21, forming an annular wall 25 extending between the venturi insert 10 and the insert's tubular bore 24. The insert's tubular bore 24 further comprises a tubular fluid inlet 26 projecting upstream from the annular wall 25 and a tubular fluid outlet 27 extending downstream. Further, the annular wall 25 has a first outer angled wall 28 which extends downstream and radially outwards from the tubular inlet toward the drill string 11 for connecting the tubular inlet 26 to the body 23 and a second angled wall 29 extending downstream and radially inwards for connecting the body 23 to the tubular fluid outlet 27. The first and second angled walls 28, 29 have the plurality of ports 12 formed therein, the ports 12 forming passages 30 being directed radially inwards and downstream and radially outwards and upstream respectively for discharging annular fluid flow F into and out of the insert's tubular bore 24, the insert 10 acting as a vena contracta, so that turbulence is created in the fluid flow F′, converting fluid stream power into noise for inducing vibration in the drill string 11.

In use, wherein the drill string 11 may be stuck in a wellbore or resistant to movement therein due to a high frictional coefficient between the drill string 11 and the wellbore, the vibration induced in the drill string 11 acts to free the drill string 11 or reduce the frictional coefficient, thereby permitting the drill string 11 to advance more rapidly through a formation, particularly during horizontal wellbore drilling. Further, the vibration induced in the drill string 11 reduces the likelihood of differential sticking during all types of drilling. Applicant also believes that vibration induced in the drill string 11 above the drill bit may act to absorb undesirable vibrations at the drill bit caused by the impact of the bit in the formation which may cause the drill bit to bounce, reducing drilling efficiency.

Having reference to FIG. 3, preferably, the angle of the ports 12 through the angled walls 28, 29 is in a range of about 24° to about 45° to a perpendicular to the insert's body 23. Most preferably, the angle is in a range of about 24° to about 26° and most preferably the angle is 26°. The number of ports 12 is varied with the diameter of the drill string 11, larger diameters having a greater number of ports 12. The ports 12 form the angled passages 30 in the insert 10 which act much like a venturi, to cause a slower boundary layer B of fluid flowing adjacent the walls of the tubing string 11 to be accelerated, compressed into faster sound waves S in the flow F at a central portion C of the flow F and then separated again for creating a turbulent flow F′ in the fluids exiting and following the insert 10, the turbulence causing the drill string 11 to vibrate.

As shown in FIGS. 1, 4 and 5a-5c and in one embodiment, the venturi insert 10 is fit within the pup joint's tubular bore 21 using means 13 such as an internal sleeve 40 which is fixed in place by an upper and a lower retainer ring or plate 41, 42. A snap ring 43 is fit in a snap ring groove 44 adjacent an upper threaded end 45 of the tubular pup joint 20, for connection with the drill string 11, against which the upper retainer ring 41 is supported. A shoulder 46 is formed in the tubular pup joint 20 against which the lower retainer ring 42 is supported. The venturi insert 10 is axially moveable within the internal sleeve 40, the axial movement of the venturi insert 10 being limited by the retainer rings 41, 42. As the fluid flow F′ exits the ports in the second angled wall 29, the insert 10 is lifted from the lower retainer ring 42 to permit flow thereby. Evidence shows that the insert 10, in operation in pup tool 20 in a 3½ inch drill pipe, lifted approximately ¾ inch from the lower retainer ring 42. A lower end 47 of the tubular point joint 20 is threaded for engagement with the drill string 11.

In one embodiment of the invention, where the lower retainer ring 42 is a solid ring, the upper and lower retainer rings 41, 42 are spaced sufficient to allow the venturi insert 10 to be lifted off the lower retainer ring 42 by the fluid flow F′ exiting the ports 12 and thus permit the fluid to flow from the venturi insert 10 with minimal interference in the pattern of fluid flow F′. As shown in FIGS. 1 and 3, the venturi insert 10 is fit into the internal sleeve 40 having a very small radial tolerance which substantially eliminates any lateral movement restricting movement to axial movement. Fluid flow F through the venturi insert 10 may cause the venturi insert 10 to spin within the sleeve 40.

As shown In FIG. 6, most preferably, the venturi insert's tubular bore 24 is sized sufficiently to permit passage of a wireline 50 therethrough to permit ongoing operations during rotating and sliding portions of a horizontal drilling process, for providing measurements and orientation information while drilling and to free stuck floats or set plugs or packers and the like, located downhole from the vibration apparatus. Most preferably, the tubular bore is sized to accommodate 1¾″ wireline.

In particular drilling situations, it may be advantageous to position a plurality of said vibration inducing apparatus 1 within the drill string 11 at intervals along a length of the drill string 11 for creating vibration, particularly during sliding operations when drilling horizontal wellbores. A plurality of vibration inducing apparatus 1, as previously described are most easily inserted into the drill string 11 in individual housings or pup joints 20, the pup joints 20 being inserted into the drill string 11 at intervals such as at tubular joints (not shown).

The dimensions of the vibration apparatus 1 are dependant upon the diameter of the drill pipe 11 in which it is to be connected. The following is illustrative of one example only.

In one embodiment of the invention sized for use in a 3½ inch drill pipe, as shown in FIG. 4, the pup joint 20 is approximately 3 feet in length Lo. The snap ring groove 44 is sized to house a 3 inch snap ring 43. The internal diameter IDu of the pup joint 20, above the shoulder 46 and below the upper threaded end 45 is between 3.100 inches and 3.105 inches, the wall thickness Wu being about 0.31 inches. A length Lu between the shoulder 46 and the upper threaded end 45 is 11 inches for housing the internal sleeve 40 and retainer rings 41, 42 therein. The remainder of the wall of the pup joint below the shoulder has an inner diameter IDs of 2.75 inches and a wall thickness Ws of 0.43 inches. An outer diameter ODp of the pup joint 20 below the upper threaded end 45 is 3.62 inches. The upper threaded end 45 has an outer diameter ODt of 4.75 inches and a length Lt of about 9 inches.

As shown in FIGS. 5a-c, the inner sleeve 40 has an OD of 3.10 inches and an ID of 2.97 inches and a length L of 9.75 inches. The retainer rings or plates 41, 42 have an OD of 3.1 inches and have an angled face 48, preferably angled about 40° to 45° from a perpendicular to the insert body 23, on an upstream and downstream face 49, 51 respectively.

An insert 10 suitable for the 3½ inch pup joint having the above-listed dimensions is about 6 inches in length and has an outer diameter of 2.87 inches and an inner diameter of 2.67 at the body portion 23. The inlet and outlet 26, 27 extend approximately 1 inch from the angled walls 28, 29 which are angled at 45 degrees and are approximately 0.25 inches in length. The body portion is approximately 3.43 inches in length. The inlet and outlet 26, 27 have an outer diameter of 2.5 inches and an inner diameter of 2.3 inches. Any number of ports 12 between eighteen to forty two ports 12, all having a diameter ranging from 0.1875 to 0.210 inches, are formed in each of the angled walls 28, 19.

EXAMPLES

In a horizontal wellbore to be drilled in northern British Columbia, Canada, surface pipe was first set with a directional shoe in place. A vibration apparatus 1 according to an embodiment of the invention was positioned in a conventional directional drilling drill string 11 approximately 250 metres (833 feet) away from a drill bit. Drilling was commenced to drill out the directional shoe which incorporates a rubber wiper plug and a steel shoe. Surprisingly, the operation which typically takes 2-3 hours was accomplished in about ½ hour. So unusual was the rapidity of the drilling time, an on-site consultant on site halted the drilling so that the actual length of drill pipe 11 could be re-tallied. Further, drilling cuttings were examined for evidence that the rubber plug and steel shoe were actually drilled through. Evidentiary bits of rubber and steel were found in the cuttings.

In another example, generally directional drilling is accomplished with an alternating combination of repeated orientation of the drill bit by rotation of the drill string and drilling using a mud motor to rotate the drill bit.

More specifically, during the orientation operation, the drill string 11 is slowly rotated to orient a bent housing in the bottom hole assembly in the desired direction. A mud motor is then energized so as to rotate the drill bit along a curved path in the oriented direction. The non-rotating drill string 11 slides along the borehole as the mud motor drills the curved path. Repeated orientation is necessary for adjusting or setting the direction of the borehole. Each time the borehole inclination must be adjusted, drilling is stopped, the drill string is rotated to reorient the drill bit and then drilling using the mud motor is recommenced.

Applied in this second example, typically a 1.5 metre slide in the formation being drilled, took 2-3 hours and possibly up to 5 hours to accomplish. Numerous slides were performed during drilling using the novel vibration apparatus, the result being a significant savings in time. A particular example was one 7 metre slide which took only 1 hour, 15 minutes to complete. Rig time was estimated to cost about $4000 CDN per hour. Thus, the savings realized using the novel vibration apparatus were significant. An approximate saving of $10,000 CDN was made in drilling out the directional shoe and an additional saving of about $19,000 CDN for the 7 metre slide alone.

Other advantages arose. Additionally, soap and nitrogen used to create foam to lift drilling cuttings, typically has a tendency to lose foam integrity, the soap and nitrogen separating from one another. Advantageously, the turbulence in the drilling fluids created by the vibration apparatus 1 acts to effectively remix the soap and nitrogen improving the integrity of the foam and thus providing better cleaning of cuttings from the wellbore.

The result of the improved cuttings removal has further advantages in the drilling process, particularly related to directional surveys performed to determine the direction of the drill bit after each connection is made to the drill string 11. As the wellbore is much cleaner than when conventional vibration apparatus are used, the directional survey is typically completed the fist time it is attempted. With conventional drilling techniques where much debris and cuttings may remain in the wellbore, it may take 2-3 times to successfully survey the bit orientation.

Claims

1. A vibration inducing apparatus for controlling fluid flow within a bore of a drill string for creating vibration within said drill string comprising:

a venturi insert fit to the drill string's bore and being axially moveable therein, the venturi insert having a body fit to the bore and having a central tubular bore formed therethrough for forming an annular wall extending between the drill string and the tubular bore; and

a tubular fluid inlet formed in the insert's tubular bore projecting upstream from the annular wall;

a tubular fluid outlet formed in the insert's tubular bore projecting downstream from the annular wall; wherein

the annular wall comprising:

a first angled wall extending downstream between the tubular fluid inlet and the body and radially outwards therefrom;

a second angled wall extending downstream between the body and the tubular fluid outlet and radially inwards therefrom; and

a plurality of ports formed in the first and second angled walls, the ports forming angled passages being directed radially inwards and downstream and radially outwards and downstream;

wherein at least a portion of the fluid flows through the insert's angled passages and at least a portion of the fluid flows through the bore, the turbulence and pattern of the flow created upon exiting the insert inducing vibration in the drill string.

2. The vibration inducing apparatus as described in claim 1 further comprising a housing for positioning the venturi insert within the at least a portion of the drill string, further comprising: means for securing the venturi insert within a bore of the housing for axial movement therein.

3. The vibration inducing apparatus as described in claim 2 wherein the means for securing the venturi insert in the housing further comprises:

an internal sleeve fit within the bore of the housing for housing the venturi insert and receiving the fluid flow, the insert being axially moveable therein; and

upper and lower retaining rings for retaining the internal sleeve in the housing's bore and for limiting the axial movement of the venturi insert therebetween.

4. The vibration inducing apparatus as described in claim 3 further comprising:

a shoulder formed in the housing against which the lower retainer ring is supported;

a snap ring against which the upper retainer ring is supported: and

a snap ring groove formed in the housing for accepting the snap ring for retaining the internal sleeve and retaining rings in the housing bore.

5. The vibration inducing apparatus as described in claim 2 wherein the housing is a pup joint threaded at an upper and lower end for connection to the drill string.

6. The vibration inducing apparatus as described in claim 1 wherein the plurality of ports are angled from about 24° to about 28°.

7. The vibration inducing apparatus as described in claim 6 wherein the plurality of ports are angled 26°.

8. The vibration inducing apparatus as described in claim 1 wherein the insert's bore is sized sufficient to permit passage of a wireline therethrough.

9. The vibration inducing apparatus as described in claim 1 wherein a number of the ports varies depending upon a diameter of the venturi insert.

10. The vibration inducing apparatus as described in claim 5 wherein a plurality of pup joints are threadedly engaged within a drill string at selected intervals for inducing vibration therealong.