ACTUATING BALL

Abstract: The present invention relates to tools for use in wellbores which are actuated by means of actuating balls. The invention provides a method of actuating a tool located in a wellbore, the method comprising the sequential steps of: (a) locating a frangible actuating ball (2) on a seat, the seat being provided in the tool for receiving the actuating ball (2); (b) pumping fluid down a tubing string attached to the tool so as to apply a force to the seat and thereby actuate the tool, the force being transmitted to the seat through the actuating ball (2); and (c) breaking the actuating ball (2) to permit fluid to flow through the seat. The invention has the advantage over the prior art of providing means for actuating a downhole tool with an actuating ball (2) so that the actuating ball (2) does not form an undesirable obstruction once the tool has been actuated.

Description: ] ACTUATING BALL The present invention relates to tools for use in wellbores which are actuated by means of actuating balls It is well known that actuating balls are widely used in the oii and gas drilling industry to operate a variety of downhoie tools These tools may be used for drilling, testing, completing and remedial work Conventional actuating balls are typically made from steel, bionze, plastic, bakehte or composite materials, and once received by a downhoie tool, remain in the well configuration until removed by mechanical or manual means Thus, once a conventional actuating ball is leceived by a tool, it remains an obstruction to fluid flowing down the tubing string until removed as described In certain circumstances, the removal of a deployed actuating ball can be essential for the completion of a downhoie operation, and the mechanical or manual methods presently employed for removal can be inconvenient and extremely expensive It is an object of the present invention to provide means for actuating a downhoie tool with an actuating ball without the actuating ball becoming an obstruction to fluid flowing through the tool once the tool has been actuated A fust aspect of the piesent mvention provides a method of actuating a tool located in a wellboie, the method comprising the sequential steps of a) locating a frangible actuating ball on a seat, the seat being provided in the tool for receiving the actuating ball, b) pumping fluid down a tubing string attached to the tool so as to apply a force to the seat and thereby actuate the tool, the force being transmitted to the seat through the actuating ball, and c) bieakmg the actuating ball to permit fluid to flow through the seat It is pieferable foi the fiangible actuating ball to be located on the seat by introducing the actuating ball into a fluid How ttavelling dow n the tubing stung It is furthei prefeiablc for the step of bieaking the actuating ball to include pumping fluid down the tubing string so as to increase the force transmitted by the actuating ball and thereby break the actuating ball Thus, the method of the present invention involves introducing an actuating ball into the tubing string and progressing the actuating ball down the string towards the tool to be actuated The actuating ball may be progressed down the tubing stπng by the action of gravity or a fluid flowing within the stπng Once the actuating ball is received by the seat, the flow of fluid down the tubing string is restricted or prevented, and therefore, a pressure differential across the actuating ball is generated The piessure differential results in a force being applied to the seat of the tool which may be harnessed to actuate the tool Once the tool has been actuated, the actuating ball remains located on the seat forming an obstruction When the obstruction generated by the actuating ball is to be removed, the actuating ball is broken mto a plurahty of small fragments which are then removed by the flow of fluid down the tubing string The actuating ball may be broken using one of a number of possible techniques, but it is preferably broken by pumping fluid down the tubing string so as to increase the pressure differential acioss the actuating ball until the structure of the ball fails A second aspect of the present invention provides a frangible actuating ball for use in the aforementioned method, the frangible actuating ball comprising a frangible wall provided with a piessure relief port adapted to equalise the piessure exerted on the sides of the wall When the actuating ball is suspended in a downhoie fluid flow the pressure relief port allows fluid suπounding the actuating ball to flow into the ball and equalise the pressure exerted on the inner and outer surfaces of the frangible wall Failure of the actuating ball structure on exposure to the high hydrostatic pressures found at well depths is thereby prevented Howevei, the pressure ielief port does not equalise the piessure diffeiential generated when the actuating ball is received by the seat and does not therefore pi event the ball fio failing when lequned Pi efei ably, the fiangible wall has a sphencal shape and is piefeiably provided as two separate portions attached to one another by suitable attachment means The two separate portions may have the same shape and may be attached by means of an adhesive Alternatively, the two separate portions may be attached to one another by means of a weld It is desirable for the frangible wall to be provided with a weak portion having a thickness less than that of the remaining portions of the wall, the weak portion being thereby adapted to break when the actuating ball transmits a predetermined force The frangible wall is preferably manufactured from boro¬ silicate A secondaiy member is preferably enclosed by the frangible wall and it is desirable for the secondary member to have a spheπcal shape A third aspect of the present invention provides a tool for use in a wellbore and an actuating ball as defined above for actuating the tool, the tool having a function actuated by movement of a seat, the seat being adapted to receive the actuating ball and thereby restrict or prevent the flow of fluid through the tool The present invention has the advantage over the prior art of providing means for actuating a downhoie tool with an actuating ball so that the actuating ball does not form an undesirable obstruction once the tool has been actuated The present invention thereby provides a more convenient actuation of a downhoie tool than that cuπently offered by the prior art An embodiment of the present invention will now be descnbed with reference to the accompanying drawings, in which Figure 1 is a cross-section view of a first embodiment of the second aspect of the present invention; Figure 2 is a cross-section view of the embodiment of Figure 1 prior to assembly, and Figure 3 is a cioss-section view of a second embodiment of the second aspect of the present invention The actuating ball 2 shown in f igures 1 and 2 is a fu st embodiment according to the second aspect of the present invention The actuating ball 2 comprises a frangible wall 4 having a spherical shape The frangible wall 4 defines an enclosed space 6 which is in fluid communication with the exterior of the actuating ball 2 via a pressure relief port 8 The pressure relief port 8 thereby ensures that the hydrostatic pressure within the enclosed space 6 is equal to that surrounding the actuating ball The frangible wall 4 is manufactured from boro-sihcate (Pyrex) to form a toughened glass The frangible wall 4 is provided with a thickness sufficient to withstand a predetermined crushing force, which if exceeded, causes the structure of the actuating ball 2 to fail and disintegrate into a plurality of small fragments The fiangible wall 4 may be provided with a portion (not shown in Figures 1 to 3) having a thickness less than that of the remaining portions of the wall This portion thereby provides a weakness in the structure of the actuating ball 2 along which the wall 4 will initially fractuie Such a portion provides convenient means for ensuπng that the actuating ball 2 fails at a specific crushing force The actuating ball 2 is constructed from two hemispheπcal portions 10, 12 which are attached to one another by means of an adhesive to form a join 14 Alternatively, the first and second hemispherical portions 10, 12 may be attached to one anothei by conventional welding techniques The two hemispherical portions 10, 12 aie identical to one anothei except foi the pressuie ielief port 8 provided in the first portion 10 I he actuating ball 20 shown in Figure 3 is a second embodiment according to the second aspect of the present invention I his second actuating ball 20 has a similar construction to the first actuating ball 2 shown in f igures 1 and 2 The same retei ence numei als as those used in Figuies 1 and 2 aie used in Figure 3 foi featuies ol the second actuating ball 20 which are the same as the corresponding features of the fust actuating ball 2 The actuating ball 20 is au anged with a secondary member 16 pi ovided in the enclosed space 6 The secondary me bei 16 is a solid spheπcal ball manufactured from glass or steel and has the function of providing the actuating ball 20 with additional weight The actuating balls 2,20 shown in Figures 1, 2 and 3 are used in association with a downhoie tool The downhoie tool is provided with a seat for receiving the actuating ball The seat will typically have an annular shape through which fluid flowing down a tubing string may pass Furthermore, the seat is generally moveable in an axial direction and biased towards an uphole position by means of a compression spring Downhoie movement of the seat against the biasing force of the compression spimg results in the actuation of the tool Downhoie tools of this type aie commonplace in the oil and gas drilling industry, and consequently, need not be descnbed any further When in use, an actuating ball of the present invention is intioduced into a tubing string and progressed downhoie towards the tool to be actuated until received by the seat of the tool The actuating ball may be progressed down the tubing string by the action of gravity or a flow of fluid within the string When the actuating ball is received by the seat, any flow of fluid through the seat is eithei lestπcted or prevented and theieby generates a pressure differential acioss the actuating ball As a result, a force is applied to the seat of the tool which may overcome the biasing force of the compi ession spring so as to move the seat and actuate the tool Once the tool has been actuated, the obstruction within the tubing stung caused by the actuating ball may be conveniently lemoved by breaking the actuating ball into a plurahty of small fragments This may be achieved by increasing the pressure differential across the actuating ball so that the predetermined crushing force is exceeded Once the actuating ball has disintegiated, the pluiahty of small fragments are displaced by the flow of fluid down the tubing string and the obstruction caused by the actuating ball is theieby iemoved If a secondary membei is piesent then this is also displaced down the tubing stπng by the fluid flow The present invention rs not limited to the specific embodiments described above. Alternative arrangement and materials will be apparent to a reader skilled in the art.

Claims: CLAIMS: 1. A method of actuating a tool located in a wellbore, the method compπsing the sequential steps of: a) locating a frangible actuating ball on a seat, the seat being provided in the tool for receiving the actuating ball; b) pumping fluid down a tubing string attached to the tool so as to apply a force to the seat and thereby actuate the tool, the force being transmitted to the seat through the actuating ball; and c) breaking the actuating ball to permit fluid to flow through the seat. 2. A method of actuating a tool as claimed in claim 1 , wherein the frangible actuating ball is located on the seat by introducing the actuating ball into a fluid flow travelling down the tubing string. 3. A method of actuating a tool as claimed in claim 1 or 2, wherein the step of breaking the actuating ball includes pumping fluid down the tubing string so as to increase the force transmitted by the actuating ball and thereby break the actuating bail 4. A frangible actuating ball for use in the method claimed in any of claims 1 to 3. the frangible acmating ball comprising a frangible wall provided with a pressure relief port adapted to equalise the pressure exerted on the sides of the wall. 5 A frangible actuating ball as claimed in claim 4, wherein the frangible wall has a spherical shape 6 A frangible actuating ball as claimed in claim 4 or 5, wherein the frangible wall is provided as two separate portions attached to one another by suitable attachment means 7 A frangible actuating ball as claimed in claim 6, wherein the two separate portions have the same shape 8 A frangible actuating ball as claimed in claim 6 or 7, wherein the attachment means is an adhesive 9 A frangible actuating ball as claimed in claim 6 or 7, wherein the attachment means is a weld 10 A frangible actuating ball as claimed in any of claims 4 to 9. wherein the frangible wall is provided with a weak portion having a thickness less than that of the remaining portions of the wall, the weak portion being thereby adapted to break when the actuating ball transmits a predeteπmned force 1 1 A frangible actuating ball as claimed in anv of claims 4 to 10. wheiein the fi angible wall is manufactuied li o boi o-silicate 12 A fiangible actuating ball as claimed in any of claims 4 to 1 1 , wheiein a secondary membei is enclosed by the fiangible wall 13 A frangible actuating ball as claimed in claim 12, wherein the secondary membei has a spherical shape 14 A tool foi use m a wellboi e and an actuating ball claimed in any ot claims 4 to 13 ioi actuating the tool the tool haung a function actuated bv movement of a seat, the seat being adapted to leccive the actuating ball and thereby icstiict oi prevent the flow of fluid through the tool.

Inventors: APPLETON ROBERT PATRICK, APPLETON, ROBERT, PATRICK
Applicants: APPLETON ROBERT P, SMITH INTERNATIONAL, APPLETON, ROBERT, PATRICK, SMITH INTERNATIONAL, INC.
Application year: 1997
Main classification: E21B23
IPC codes: E21B23, E21B34