Abstract:
A control sub for use with a hydraulically operated downhole tool. In an embodiment, the sub comprises an outer sleeve connected to a work string and an inner sleeve slidably engaged to the outer sleeve by matching hex profiles, connected to the downhole tool. Radial ports in the outer sleeve provide selective circulation of fluid from the tool and by closing these ports with the sleeve fluid pressure in to the downhole tool can be controlled. Closure is effected by setting down weight on the sub against the tool. An indexing mechanism is also described to keep the tool in a configuration, which maintains pressure on the tool. The sub is suitable for use with an expander tool.

Description:
CROSSREFERENCE TO RELATED APPLICATIONS 
   This application claims priority from PCT/GB03/01596, having an international filing date of 14 Apr. 2003, and a priority date of 16 Apr. 2002. 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not Applicable 
   THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
   Not Applicable 
   INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
   Not applicable 
   BACKGROUND OF THE INVENTION 
   The present invention relates to hydraulically operated downhole tools and in particular, though not exclusively, to a control sub to provide selective control of a hydraulically operated expander tool for tubulars. 
   It is known in the art to utilise the pressure of fluid pumped through a work string in a well bore to control a hydraulically activated tool in the well bore. For instance, when expanding tubulars such as slotted, screen or solid pipe a rotary expander may be used. These expanders have a cone head with an outer diameter greater than the diameter of the tubular. On the tool are arranged hydraulically operated rollers. When mounted on the end of a work string and inserted into a tubular, hydraulic pressure introduced to the expander tool will force the cone through the tubular and with the aid of the rollers the tubular will be expanded to the diameter of the expander tool. 
   The hydraulic pressure to operate these tools is typically supplied from the surface of the well bore by pumps. Due to the distances of travel to the location of the expander tool it is difficult to control the operation of the expander tool and, in particular, to provide a constant pressure to give a uniform control and therefore expansion of the tubular in the well bore. It is also difficult to start and/or stop the expander tool at desired locations in the well bore. 
   It has been recognised that being able to control the flow of hydraulic fluid adjacent a hydraulically operated downhole tool would be advantageous. U.S. Pat. No. 5,392,862 describes a drilling mud flow control sub that provides the necessary fluid flow and pressure to activate an expanding remedial tool such as an underreamer, section mill or other cutting tool. The sub consists of a cylindrical sub assembly housing forming a first upstream end and a second downstream end. The housing is threadably connected between a drill string at its first upstream end and a tool at its downstream end. Intermediate the upstream and downstream ends is located a drop ball seat so that insertion of a drop ball will prevent hydraulic fluid flow to the tool. A rupture disc is affixed to a hole formed in the control sub wall normal to the sub axis, above the drop ball seat, so that when obstructed fluid is shunted from the sub. 
   This flow control sub provides means to terminate fluid flow to the tools hydraulically operating mechanism while allowing fluid circulation through the sub when the tool is deactivated ‘while tripping’ and/or rotating the drill string. However a major disadvantage of this tool is in the single function operation i.e. in turning the hydraulic mechanism off. There is no selective control of the tool. Additionally when hydraulic fluid is applied to the tool through the sub the pressure of this fluid can only be controlled from the surface as with the prior art systems. Further a disadvantage is in the length of time taken for the drop ball to reach the seat and the associated difficulties if the single ball does not locate correctly in the seat. 
   It is an object of at least one embodiment of the present invention to provide a control sub for use with a hydraulically operated downhole tool which allows the tool to be operated in selective on and off configurations. 
   It is a further object of at least one embodiment of the present invention to provide a control sub for use with a hydraulically operated downhole tool which allows control of the hydraulic pressure delivered to the tool. 
   It is a yet further object of at least one embodiment of the present invention to provide a control sub for use with a hydraulically operated downhole tool which allows selective control of fluid circulation when the tool is run in or tripped from the well. 
   It is a still further object of the present invention to provide a method of controlling hydraulic pressure to a hydraulically operated downhole tool in a well bore. 
   BRIEF SUMMARY OF THE INVENTION 
   According to a first aspect of the present invention there is provided a control sub for use with a hydraulically operated downhole tool, comprising a tubular assembly having a through passage between an inlet and a first outlet, the inlet being adapted for connection on a workstring, the first outlet being adapted for connection to a hydraulically operated downhole tool, one or more radial outlets extending generally transversely of the tubular assembly, an obturating member moveable between a first position permitting fluid flow through the one or more radial outlets and a second position closing the one or more radial outlets, wherein the obturating member is moved from the first position to the second position by a compressive force applied from the tool. 
   It will be appreciated that release of the compressive force will open the one or more radial outlets and thus by varying the compressive force applied from the tool the amount of fluid circulated radially out of the sub can be controlled. Preferably the cross-sectional area of the first outlet is greater than the cross-sectional area of the second outlet. By varying the circulation of fluid radially from the sub the fluid exiting the sub through the first outlet can be varied. This fluid exiting the first outlet controls the hydraulic pressure applied to the tool and therefore the operation of the tool. 
   Preferably the compressive force occurs from the downhole tool remaining static relative to movement of the workstring and the control sub. Thus the control sub acts in a similar manner to weight set tools but provides control as weight is set. 
   Preferably the tubular assembly comprises an inner sleeve and an outer sleeve, sealingly engaged to each other. Preferably the outer sleeve is adapted to connect to the work string and the inner sleeve is adapted to connect to the tool. More preferably the inner and outer sleeves include mutually engageable faces so that the sleeves may be axially slideable in relation to each other over a fixed distance. 
   Preferably also the obturating member is a sleeve. Advantageously the sleeve is coupled to the inner sleeve of the tubular assembly. Preferably the obturating member is also axially slideable within the tubular assembly. 
   Preferably the one or more radial ports are located on the outer sleeve. Advantageously matching radial ports are located on the obturating member such that under compression each set of radial ports align to allow fluid to flow radially from the sub. 
   Preferably an outer surface of the inner sleeve includes a portion having a polygonal cross-section. Preferably also an inner surface of the outer sleeve has a matching polygonal cross-section. These matching sections ensure that when the work string is rotated the sub is rotated and with it the hydraulically operated tool. More preferably the polygonal cross section is a hex cross-section. 
   Preferably also the sub includes an indexing mechanism. The indexing mechanism may comprise mutually engageable formations on the inner and outer sleeves. Preferably the engagement formations comprise a member and a recess in which the member may be engaged. The member may comprise a pin and the recess may comprise a slot. Preferably, one of the member and the pin is mounted on the outer sleeve and the other is mounted on the inner sleeve. Typically the slot extends circumferentially around the respective sleeve and the pin may move circumferentially with respect to the slot. 
   Preferably the slot and/or pin is configured such that the pin and slot move in only one direction to each other when engaged and operated. 
   Preferably also the slot includes one or more longitudinal profiles as offshoots from the circumferential path. When the pin is located in such a profile, the sleeves may move relative to each other to effect the relocation of the obturating member from one position to another. 
   According to a second aspect of the present invention there is provided a method of controlling a hydraulically operated downhole tool in a well bore, the method comprising the steps: 
   (a) mounting above the tool on a work string a control sub, the sub including a first outlet to the tool and one or more radial outlets through which fluid within the work string will flow when not obstructed by an obturating member, the obturating member being moveable under a compressive force from the tool; 
   (b) running the tool into a well bore and locating the tool on a formation in the well bore; 
   (c) compressing the control sub by setting down weight on the tool; 
   (d) using the compressive force to move the obturating member and thereby control the fluid flow through the radial outlets, regulating the fluid pressure from the first outlet to hydraulically control the tool. 
   Preferably the method includes the step of running the tool in the well bore with the radial outlets in an open position and circulating fluid within the well bore. 
   Preferably the method includes the step of indexing the sleeves with respect to each other to move a pin in a sleeve within a recess of the other sleeve. Further steps may therefore include locating the pin in a position wherein the compressive force may be released and the radial ports may selectively be in an open or closed position. 
   Preferably also the method may include the steps of picking up and setting down the weight of the string repeatedly to cycle opening and closing of the radial outlets and thus provide a selective continuous ‘on’ and ‘off’ operation of the tool. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings of which: 
       FIGS. 1  ( a ) to ( d ) are a series of part cross-sectional schematic views of a control sub, according to an embodiment of the present invention, in a work string with an expander tool illustrating the operating positions of the control sub during expansion of a pipe; and 
       FIG. 2  is an illustration of an indexing mechanism showing the outer surface of an inner sleeve and, in cross-section, the outer sleeve of a control sub according to a further embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Reference is initially made to  FIGS. 1  ( a ) to ( d ) of the drawings which illustrates a control sub, generally indicated by Reference Numeral  10  according to an embodiment of the present invention, in a work string  12  with an expander tool  14  illustrating the operating positions of the control sub  10  during expansion of a pipe  16  within a casing  18  of a well bore. 
   With specific reference to  FIG. 1  ( a ), control sub  10  comprises a tubular body  20  having an outer sleeve  22  and an inner sleeve  24 . Outer sleeve  22  is of two-part construction, having an upper portion  26  and a lower portion  28 . Upper portion  26  includes a threadable portion  30  for connection of the sub  10  to a work string  12 . Upper portion  26  includes four apertures  32  circumferentially arranged around the sleeve  22  to provide access through the sleeve  22 . Lower portion  28  is threadably attached to upper portion  26 . Lower portion  28  has an inner surface  34 , which is hexagonal in cross-section. When threaded together the upper  26  and lower  28  portions of the outer sleeve  22  provide a lip  36  whose purpose will be described hereinafter. 
   Inner sleeve  24  includes a central bore  35  through which fluid may pass through the control sub  10 . Inner sleeve  24  has an outer surface  38  having a hexagonal cross-section to match the inner surface  34  of the outer sleeve  22 . Inner sleeve  24  further provides a threadable connection  40  at the base of the sub  10  for connection to an adapter  42  for the expander tool  14 . Beside the threadable connection  40  is located a stop  44 . 
   The upper end of inner sleeve  24  is threadably connected to an obturating sleeve  48 . Obturating sleeve  48  is located within the inner bore  35  of the control sub  10 . Obturating member  48  includes a matching set of apertures  50  to those apertures  32  in the outer sleeve  22 . It will be appreciated by those skilled in the art that the size and dimensions of the apertures  50  could be varied to provide a flow profile to regulate flow through the apertures  32  of the outer sleeve  22 . Further at a lower end of sleeve  48  is located a lip  46 . 
   In use, the control sub  10  is mounted at the end of a work string  12  by threadable connection  30 . An expander tool  14  is located onto the control sub via a threadable connection  40  with an optional adapter  42 . As seen in  FIG. 1  ( a ), when mounted the lips  36 , 46  of the outer sleeve  22  and obturating sleeve  48  respectively abut so that the inner sleeve  24  and obturating sleeve  48  are supported from the outer sleeve  24 . In this first position of the obturating sleeve  48  the apertures  50  and  32  are aligned to provide a radial port for the expulsion of fluid radially from the sub  10  towards the casing  18 . This is the configuration chosen for running the work string into the well and thus fluid can circulate from the sub via the inner bore  35  and the radial port provided by the apertures  32 ,  50 . 
   Reference is now made to  FIG. 1  ( b ) of the drawings wherein the work string has been run in the well bore through the casing  18  and the expander tool  14  has now located on a pipe  16  which requires to be expanded radially. When the expander tool  14  reaches the pipe, the expander tool will be stopped and the weight of the string will bear down upon the tool such that the tool  14  provides a compressive force onto the sub  10 . The compression force will move the inner sleeve  24  relative to the outer sleeve  22 , such that the inner sleeve  24  remains static and the outer sleeve  22  is shifted relatively downwards. This shift of the sleeves  22  and  24  provides an apparent shift of the obturating sleeve  48  such that the apertures  32 ,  50  are now mis-aligned. Fluid flow is now prevented from exiting the tool radially through the apertures  32 ,  50 . Further fluid is prevented from escaping between the sleeves  22 ,  24  by virtue of the o-rings  52 ,  54  located on either side of the aperture  50  of the obturating sleeve  48 . 
   Reference is now made to  FIG. 1  ( c ) of the drawings wherein the sub  10  is held in compression. The expander tool  14  has been pressured up and no pumping of fluid through the inner bore  35  is required to maintain the expander tool in the actuated position unless a bleed is located in the expander tool  14 . Pipe  16  is expanded by virtue of a cone  56  of the tool entering the pipe  16  and forcing the pipe to expand to a diameter equal to the actuated expander tool  14 . Expander tool  14  is operated from a constant pressure of fluid delivered through the inner bore  35 . Pipe  16  can become sealingly engaged to the casing in this operation. Alternatively, there may be annulus remaining between pipe  16  and casing  18 . 
   It will be appreciated by those skilled in the art that any type of hydraulically operated expander tool could be used in this configuration and thus, a full description of an expander tool is absent so as not to limit the present invention. 
   As the expander tool expands the pipe it maintains a compressive force on the sub  10  so that the ports  32 ,  50  remain mis-aligned for the pressure to be maintained constantly through the inner bore  35 . In a preferred embodiment of the present invention there is located within the bore  35  a sensor  58 . Sensor  58  is a downhole pressure memory gauge which monitors the pressure of the hydraulic fluid through the bore  35 . This can be used to determine that a constant hydraulic pressure has been exerted on the expander tool to monitor the expansion of the pipe  16 . It will further be appreciated that if the pressure within the bore  35  requires to be adjusted, weight can be released from the string  12  thereby reducing the compressive force from the expander tool  14  such that some alignment of the apertures  32 ,  50  occurs and a small radial expulsion of fluid from the sub  10  may occur to control the pressure within the bore  35 . 
   When the pipe  16  is fully expanded in the casing  18  the expander tool  14  can be pulled from the well by “tripping” the sub  10  on the work string  12  from the casing  18 . As the expander tool  14  does not abut the surface of the pipe  16  when the pipe  16  is expanded, as shown in  FIG. 1  ( d ), there is no weight bearing facility for the expander tool  14  and thus a compressive force on the sub  10  is released. When the compressive force is released, the inner sleeve  24  drops in relation to the outer sleeve  22  and thereby causes the obturating sleeve  48  to relocate to the first position wherein the apertures  32  and  50  are now realigned to provide a radial port for hydraulic fluid within the inner bore  35  to pass from the sub  10  into the annulus created between the sub  10  and the casing  18 . Thus, as the tool  14  is pulled out of the hole, fluid can circulate within the well bore. Control sub  10  is thus in tension during this operation. 
   Reference is now made to  FIG. 2  of the drawings, which illustrates an additional feature of the sub  10 , provided in a further embodiment of the present invention. Like parts to those of  FIG. 1  have been given the same Reference Numeral but are now suffixed ‘a’. 
   In this embodiment the sub  10  is provided within an indexing mechanism generally indicated by Reference Numeral  60 . Indexing mechanism  60  comprises an index sleeve  62  located on the inner sleeve  24  on the sub  10   a . On the outer surface  38   a  there is located a profile  64 . Profile  64  is a key providing a lower  66  circumferential arrangement of v-grooves and on every second groove there is located a longitudinal portion  68 . On the outer sleeve  22   a  there is located one or more index pins  70 . In the embodiment shown there is one index pin  70 . Index pin  70  is arranged to project towards the inner bore  35   a  and locate within the profile  64 . The pin  70  may move to any position within the profile  64  as long as it remains in the path provided around the lower profile  66  or is located into one of the longitudinal portions  68 . 
   In operation, a sub  10   a  including the index mechanism  60  would be run into a casing as described herein with reference to  FIG. 1 . When the tool has landed on a formation in well bore, the pin  70 , originally located in the longitudinal portion  68 , will be driven along the slot and into the circumferential portion  66 . 
   When the pin  70  is located at a top  72  of the longitudinal portion  68 , the radial ports (not shown) in the outer and inner sleeves  22   a  and  24   a  (alike to the ports  32  and  50  in the tool  10  of  FIGS. 1   a  to  1   d ) are aligned and fluid may circulate from the sub  10   a  as described herein before. 
   When the index pin  70  is located within the circumferential portion  66 , the radial ports are closed as described herein with reference to  FIGS. 1  ( b ) and  1  ( c ). As the circumferential slot  66  includes a number of v-grooves, each v-groove provides a cavity  74  into which the pin  70  can locate and be held relative to the sleeve  62 . When the pin  70  is located in the cavity  74 , the sub  10   a  can be picked up on the string  12   a  and thus the expander tool can be tripped from the well bore with the radial ports in a closed position. By compression and release of the sub in a reciprocating action, the index pin  70  can be moved around the circumferential profile  66  and thereby the position of the radial ports, can be selected to provide controlled operation of the tool  14   a.    
   In the embodiment shown in  FIG. 2 , the sub  10   a  may be picked up while the radial ports remain closed and only on every second time the tool is picked up will the ports become open by virtue of the pin moving from the cavity  74  into the slot  68 . 
   A principal advantage of the present invention is that it provides a control sub for a hydraulically operated downhole tool, which controls the hydraulic pressure to the tool adjacent to the sub. A further advantage of the present invention is that it provides selective operation of a hydraulically operated downhole tool while the tool is in the well bore. 
   By use of an indexing mechanism, a further advantage of the present invention is that it ensures that pressure is maintained upon the expander tool without the risk of the radial ports opening and thus the expander tool can be reciprocated within a well bore without loss of hydraulic pressure upon the expander tool. 
   Modifications may be made to the invention herein described without departing from the scope thereof. For example, it will be appreciated that any number of apertures can be arranged to provide radial expulsion of the fluid for circulation from the sub. Additionally, these ports may be arranged to expel fluid in a direction substantially upwards or downwards in relation to the casing. Further, it will be appreciated that the control sub of the present invention could be used in a well bore, which is vertical, inclined or horizontal.