Abstract:
A downhole tool for treating a zone adjacent a wellbore, comprising a body having at least two separable portions, the portions operable to open and close a fluid path through the tool, and at least one manipulator, like a spring-loaded finger, to establish a fluid path between an interior and exterior of the wellbore, thereby permitting a zone adjacent the wellbore to be treated. In another embodiment a method is disclosed for treating a zone of interest adjacent a wellbore.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to treating zones adjacent a wellbore. More particularly, the invention relates to hydraulically fracturing multiple zones in a single trip. 
     Description of the Related Art 
     With extended reach wells, it is common to have multiple hydrocarbon-bearing zones at different locations along the length of a wellbore. In order to increase production at the various zones, they are often “hydraulically fractured.” Hydraulic fracturing is a technique in which a liquid, like water is mixed with sand and chemicals and injected at high pressure into a hydrocarbon-bearing formation (zone) surrounding the wellbore. The resulting small fractures (typically less than 1 mm) permit oil and gas to migrate to the wellbore for collection. Multiple zones at different depths mean multiple fracturing jobs requiring each zone to be isolated from adjacent zones, typically through the use of packers that seal an annular area between the wellbore and a tubular string extending back to the surface of the well. 
     In some instances, the zones are fractured in separate trips using bridge plugs, resulting in multiple trips and increased costs. In other cases, the zones are treated using ball seats and balls of various sizes, resulting in wellbore debris when the balls are “blown out” to reach a lower zone. What is needed is a more efficient apparatus and methods for treating multiple zones in a single trip. 
     SUMMARY OF THE INVENTION 
     The present invention generally includes a downhole tool for treating a zone adjacent a wellbore, comprising a body having at least two separable portions, the portions operable to open and close a fluid path through the tool, and at least one manipulator, like a spring-loaded finger, to establish a fluid path between an interior and exterior of the wellbore, thereby permitting a zone adjacent the wellbore to be treated. In another embodiment a method is disclosed for treating a zone of interest adjacent a wellbore. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1  is a section view of a tubular string disposed in a wellbore, with a fracturing tool and a latch assembly disposed in the string. 
         FIG. 2  is a section view of the wellbore of  FIG. 1 , showing the latch assembly on wireline latched to the fracturing tool. 
         FIG. 3  is a section view of the wellbore of  FIG. 2 , showing the latch assembly/tool moving upwards in the string to a position in which a spring-loaded finger is adjacent a lower portion of a finger recess formed in a sub and in contact with a lower edge of a sliding sleeve. 
         FIG. 4  is a section view showing the spring-loaded finger in a position adjacent an upper portion of the finger recess and showing the sliding sleeve having been moved upward to a location wherein a window of the sleeve is aligned with a port in a wall of the sub. 
         FIG. 5  is a section view of the wellbore, illustrating a fracturing job in progress. 
         FIG. 6  is a section view of the wellbore, wherein the latch assembly/tool is shown moving upwards towards another sub. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention relates to multiple formation treatment jobs performed in a wellbore in a single trip. 
       FIG. 1  is a section view of a wellbore  100  having a string of production tubing  110  installed therein. At a lower end of the string are two subs  125 ,  130  that are installed in the string  110 . Each sub is placed in a location adjacent a zone of interest A, B and includes a slidable sleeve  135  having a window  140  formed therein and at least one port  145  permitting fluid communication between an inside and outside of the string  110  when the window  140  and the port  145  are aligned. In the embodiment of  FIG. 1 , each sub  125 ,  130  can be isolated from the other sub by packers  150 . In  FIG. 1 , only the lowermost packer is shown in a set position, with the upper packers unset. Downhole settable packers are well known in the art and can be set remotely either with tools, movement, or in some cases by exposure to fluids. While only two subs  125 ,  130  are described in the present embodiment, it will be understood that the invention can be used with any number of subs and aspects of the invention are particularly useful when multiple zones (10-50) are being treated. Temporarily anchored at a lower end of the string is a fracturing tool  200  having an upper body  205 , a lower body  210 , an anchor assembly  215 , and a latch recess  220 . Shown in the wellbore above the tool and suspended on wireline  230  is a latch assembly  225 , the operation of which will be explained in relation to the other figures. 
     Arrows  300  illustrate fluid flow and arrow  301  illustrates downward movement of the latch assembly. In  FIG. 1 , fluid is being circulated from the surface of the well, out a port  235 , and upwards in an annulus  240  formed between the wellbore  100  and the tubing string  110 . In one embodiment, the port  235  is initially blocked by a frangible member (not shown) and opened when pressure on a column of fluid in the wellbore is raised above a rupture threshold of the frangible member. Opening a port in a tubular string through pressure is well known and in the embodiment shown, the frangible member may have been previously ruptured prior to the installation of the wireline and latch assembly. One purpose of the flowing fluid is to urge the latch assembly  225  and wireline  230  downwards in the wellbore  100  as the fluid acts against the shape of latch transfer cup  245  (which is essentially a transport assembly) annularly disposed on the latch assembly  225 . The latch assembly is also equipped with latch members  250  constructed and arranged to mate with latch recess  220  formed in an interior of the tool  200 . In one embodiment, fluid flow adequate to move the latch assembly downwards is 5-10 barrels of fluid per minute. 
       FIG. 2  is an enlarged section view of the wellbore  100  showing the latch assembly  225  connected to the tool  200 . As illustrated ( FIG. 1 ), downwardly flowing fluid has acted upon the latch transfer cup  245  and the assembly has been “pumped down” to the tool. In  FIG. 2 , latch members  250  of the assembly are housed in the latch recess  220  of the tool  200 .  FIG. 2  also illustrates additional features of the tool, including upper body portion  205  which is suspended at a lower end of the latch assembly  225 . Lower body portion  210  is anchored to an inner wall of the tubular string  110  with anchor assembly  215  having spring-loaded anchors that permit upward movement but prevent downward movement of the tool  200  due to the geometry of its their teeth  260 . Upper body portion is also equipped with manipulators in the form of outwardly biased, spring-loaded fingers  265  that are biased against an inner wall of the tubular  110  and serve to shift sleeves  135 , thereby establishing a fluid path between an interior and exterior of the wellbore, as will be discussed herein. Each finger  265  is biased with a spring  270 . 
     In  FIG. 2 , arrow  302  illustrates upward movement of the tool  200  and latch assembly  225  due to an upward force applied to the wireline  230  from the surface of the well. In this disclosure, the term “wireline” is meant to include cable-like material having the strength to support the weight of the tool and any resistance applied to it in order to operate downhole shifting mechanisms, as will be described herein. In one embodiment, the wireline does not include electrical conductors. 
     The tool  200  is arranged wherein when upward movement is applied, the upper and lower bodies  205 ,  210  separate to create a gap  275 . In doing so, an equalization path  280  formed in the upper body  205  is aligned with equalization ports  285  in the lower body  210 , and pressure between an upper  305  and lower  310  annulus is equalized. In this manner, the tool can more easily be moved upwards in a string in order to treat different zones. In one embodiment, the upper and lower bodies  205 ,  210  are spring-biased apart to ensure their separation in case the anchor  215  does not provide enough “drag” on the lower body. Typically, after latch assembly  225  is connected to the tool  200 , the additional packers  150  are set, thereby isolating the subs from each other. 
       FIG. 3  is similar to  FIG. 2 , with the tool  200  being urged upwards in the string  110  as shown by arrow  301  and the upper and lower body portions  205 ,  210  of the tool separated in order to align the equalization path  280  and ports  285 . In  FIG. 3 , the tool  200  has been moved upwards in the string  110  to a location adjacent sub  125  and the fingers  265  have partially entered a finger recess  315  formed in the inner diameter of the sub  125 . The finger recess  315  is designed to facilitate the shifting of sleeves  135  at each sub  125 ,  130  ( FIG. 1 ) in order to expose one or more ports  145  leading from the wellbore to an adjacent zone, in this case lower zone A. In  FIG. 3 , the fingers  265  have also contacted a lower edge  134  of the sleeve  135  and are poised to move the sleeve upwards to a position wherein window  140  formed in the sleeve and port  145  in the body of the sub are aligned. Because the tool  200  is still being moved upwards, the equalization path remains open between upper  305  and lower  310  annular areas. 
       FIG. 4  illustrates a position wherein the tool  200  has moved upwards to a location in lower sub  125  wherein the fingers  265  have contacted an upper edge  316  of the recess  315 . In this position, the sleeve window  140  is fully aligned with the port  145 , and upward movement of the tool is halted. In addition, the contact between the finger  165  and the upper edge  316  of the recess creates a resistance with a corresponding resistance in the wireline  230  noticeable by an operator at the surface of the well. 
       FIG. 5  shows the tool  200  of  FIG. 4  after upward force from the wireline  230  has ceased. The absence of upward force has permitted the upper  205  portion of the body to move downwards slightly (note position of fingers  265  relative to recess  315 ), thereby closing the gap  275  and misaligning the equalization path  280  and ports  285 . In this position the closed path  280 , in conjunction with a body cup seal  320  annularly disposed about the body of the tool  200 , essentially seal the wellbore below the tool. The body cup seal  320  is typically constructed of a stiff but resilient material and its shape ensures that its walls will expand against an inner diameter of the sub, thereby sealing the interior of the sub to the flow of fluid. As shown by arrows  303 , fracturing material can now be pumped from the surface of the well at high pressure in order to flow into zone A through the window  140  in sleeve  135  and through the port  145 . 
       FIG. 6  shows the tool of  FIG. 5  after the fracturing job is completed. In this Figure the tool  200  is again being raised as is evident by upward arrow  301  and the location of the fingers  265  relative to the recess  315 . As shown, the fingers have moved upward past an upper edge  316  of the recess  315  and past the lower edge  134  of sleeve  135 . More specifically, the fingers  265  have depressed springs  270  to a point where the fingers have cleared the lower edge  134  of the sleeve  135 . An upper edge of the sleeve  136 , as shown in the Figure, has contacted a downwardly facing shoulder  137  formed in the interior of the sub and further upward movement of the sleeve  135  is prevented. In this manner, the tool  200  can continue its upward movement in the string until it reaches sleeve  135  of sub  130  (see  FIG. 1 ). In the meantime, window  135  and port  145  of sub  125  stay aligned and will provide a path to gather hydrocarbons as the well produces. 
     In one example, the invention is used as follows: The tool  200  is run into a wellbore  100  at the lower end of a string  110  of production tubing. Installed in the string are one or more subs  125 ,  130 , each of which includes a sleeve  135 , window  140  and port  145  as has been disclosed herein. The one or more subs are installed in the string in a manner that places them adjacent corresponding zones of interest A, B. Initially, the ports  145  in each sub are in a “closed” position. At some point after the string  110  and tool  200  are run into the wellbore  100 , a latch assembly  225  is “pumped down” to a location where it latches with the tool  200 . In one embodiment, the latch assembly runs in on wireline  230 , as has been described. In another embodiment, it is run into the wellbore on coiled tubing (not shown) or another relatively ridged means. 
     Once the latch assembly  225  and tool  200  are mated, the tool is pulled upwards in the wellbore with an equalization path  280 ,  285  through the tool opened. As it moves upwards, spring-loaded fingers  265  encounter the lower end  134  of a sleeve and urge it upwards to a point wherein a window  140  formed in the sleeve  135  aligns itself with an adjacent port  145  formed in an outer wall of the sub. In one embodiment, a recess  135  is formed in an interior wall of the sub to facilitate the manipulation of the sleeve by the fingers  265 . Once the window and port are aligned and an upper and lower annular areas  305 ,  310  above and below the tool are isolated from one another, a fracturing job is performed. Thereafter, the tool  200  is pulled upward to the next tool. The process can be repeated for each zone of interest. 
     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.