Abstract:
A tubing conveyed tool for use in perforating a well bore utilizing abrasive perforating techniques. The perforating tool is particularly useful in non-vertical wells. The perforating tool is designed to permit running and setting a bridge plug, and then perforating the well bore without requiring the removal of the tool string. An eccentric weight bar can also be used to allow for directional perforating in non-vertical wells. The eccentric weight bar uses gravity to cause the bar to rotate to a predetermined position.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of co-pending application Ser. No. 11/372,527, entitled “Methods and Devices for One Trip Plugging and Perforating of Oil and Gas Wells,” filed Mar. 9, 2006, which claims the benefit of the filing date of Provisional Application No. 60/661,262, entitled “Improved Abrasive Perforating Device and Methods of Use,” filed Mar. 12, 2005, and the contents of these applications are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The instant invention relates to devices and methods for setting bridge plugs and perforating hydrocarbon wells. More particularly, the invention describes new devices that may be conveyed on tubing to allow setting a bridge plug and perforating the well in a single tubing trip. 
     BACKGROUND OF THE INVENTION 
     After drilling a well for hydrocarbons, it may be necessary to perforate the walls of the well to facilitate flow of hydrocarbons into the well. Wells require perforation because the drilling process causes damage to the formation immediately adjacent to the well. This damage reduces or eliminates the pores through which the oil or gas would otherwise flow. Perforating the well creates a channel through the damage to undamaged portions of the formation. The hydrocarbons flow through the formation pores into the perforation channels and through the perforation channels into the well itself. 
     In addition, steel casing may be set within the hole adjacent to the hydrocarbon bearing formation. The casing forms a barrier that prevents flow of the hydrocarbons into the well. In such situations, the perforations go through the casing before entering the formation. 
     Traditional methods of perforating the well (both casing and the formation) involved lowering tools that contain explosive materials into the well adjacent to the hydrocarbon bearing formation. Discharge of the explosive would either propel a projectile through the casing and into the formation or, in the case of shaped charges, directly create a channel with explosive force. Such devices and methods are well known in the art. 
     In vertical wells, gravity may be used to lower the perforating device into position with wireline being used to hold the device against gravity and retrieve the device after discharge. For lateral wells, which may be horizontal or nearly horizontal, gravity may only be used to lower the perforating device to a point where the friction of the device against the well bore overcomes the gravitational force. The perforating device must then be either pushed or pulled along the lateral portion of the well until the device reaches the desired location. 
     For wireline conveyed devices, motorized devices called tractors, which are well known in the art, are sometime used to pull the explosive perforating device into position. Tractors, however, can be unreliable and may be damaged by the explosive force of the perforating device. 
     Another method for positioning the perforating device is with coiled tubing. This technique is sometimes called tubing conveyed perforation or TCP. One advantage of TCP is that the perforating device is attached to the end of the coiled tubing and the coiled tubing pushes the device into the proper location. For lateral wells, the tubing will often contain wireline within the coiled tubing. The wireline can be used to carry an electric current to discharge the explosive contained within the perforating device. 
     Another advantage of tubing conveyed perforation is the ability to set a hydraulic bridge plug at a location in the well below (distal in relation to the wellhead) the relevant hydrocarbon bearing formation, or between two hydrocarbon bearing formations. This allows the producing zones of the well to be isolated. Once the bridge plug is set, the perforating device can be fired and any fluids from the newly perforated zone will not flow into any regions separated by the bridge plug. 
     Special explosive perforating devices have been developed that contain a channel for the flow of hydraulic fluid. Thus, the bridge plug can be set, and the perforating device discharged with a single trip of the coiled tubing. Without a flow channel in the perforating device, the tubing end would have to return to the surface, have a perforating device attached, and return to the hydrocarbon bearing formation before perforation can be performed. Thus, the ability to set the bridge plug and perforate in a single trip saves significant time. 
     While the perforating devices used in prior art methods of TCP have provided the ability to set a bridge plug and perforate the well in a single trip, the methods are still limited. For example, the length of the perforated zone is limited to the length of perforating gun assembly. In other words, to perforate along a 100 foot length of the well, the perforating gun assembly must be at least 100 feet long. This does not include the length of the bridge plug at the end of the gun assembly. However, the increased length also increases the mass of the gun assembly, making the assembly more difficult to deploy in horizontal wells. 
     Long gun assemblies have an additional disadvantage. The gun assembly is introduced into the well using a lubricator. The lubricator is a device attached to the well head below the coiled tubing or wireline injector, depending on whether tubing or wireline is used to convey the gun assembly. The length of the lubricator is directly related to the length of the gun assembly. If the gun assembly is 100 feet long, the lubricator is at least the same length. In such a case, the injector, either coiled tubing or wireline, above the lubricator is at least 100 feet in the air which creates difficulties running hydraulic hoses, control lines, and with maintenance should the injector head fail. 
     One alternative to the explosive perforating device is an abrasive perforating device. Abrasive perforating devices direct a concentrated stream of fluid against the casing and, once the casing is penetrated, the surrounding formation. The fluid contains a suspended solid or solids, such as sand, to wear away the metal and rock of the casing and formation. Abrasive perforation is well known in the art. 
     The operator merely increases flow of the abrasive fluid to begin perforation and decreases flow to stop perforation. The depth and size of perforations are controlled by the fluid pressure and by the length of perforation time. With an abrasive perforator, perforations can be made across a long interval of the well in a single trip and without increasing the size of the tool string. Thus abrasive perforators avoid the problems created by the increased size and weight of long gun assemblies. 
     Prior art abrasive perforation devices have been run on the end of tool strings. Thus, the fluid channel ends at the bottom of the abrasive perforating device. This configuration has prevented the addition of other tools, such as bridge plugs, below the abrasive perforating device. As mentioned above, running a bridge plug or other tool below the abrasive perforator is sometimes desirable. 
     SUMMARY OF THE INVENTION 
     The present disclosure describes a number of embodiments of a tubing conveyed abrasive perforating tool that utilizes a sliding sleeve or the like to permit fluid communication through the tool to a bridge plug. The fluid communication to the bridge plug permits setting the bridge plug. Once the bridge plug is set, the sliding sleeve or similar device is actuated to close the fluid path through the perforating tool, and open the fluid paths to the perforating orifices. The tool can then be used for abrasive perforating moving up the well bore for as many perforations as are needed. With the addition of an eccentric weight bar or the like, the perforating can be performed directionally. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The forgoing summary, preferred embodiments, and other aspects of subject matter of the present disclosure will be best understood with reference to a detailed description of specific embodiments, which follows, when read in conjunction with the accompanying drawings, in which: 
         FIGS. 1A-1B  illustrate an elevation view and a cross-sectional view of an embodiment of the perforating tool according to certain teachings of the present disclosure showing the sliding sleeve in a position that permits fluid communication through the tool. 
         FIGS. 2A-2B  illustrate an elevation view and a cross-sectional view of the embodiment of  FIGS. 1A and 1B  wherein the sliding sleeve has moved to a position where fluid communication is directed to the perforating orifices. 
         FIGS. 3A-3B  illustrate an elevation view of the perforating tool of  FIG. 1  in a tool string with a bridge plug at the bottom of the string and with the bridge plug set and disconnected from the string. 
         FIG. 4  illustrates an elevation view of an embodiment of the perforating tool according to certain teachings of the present disclosure showing the sliding sleeve in a position that permits fluid communication through the tool. 
         FIGS. 5A-5B  illustrate an elevation view and a cross-sectional view of the embodiment of  FIG. 4  wherein the sliding sleeve has moved to a position where fluid communication is directed to the perforating orifices. 
         FIG. 6  illustrates an elevation view of an embodiment of the perforating tool according to certain teachings of the present disclosure showing a sliding sleeve configuration with three rows of jet nozzles. 
         FIG. 7  illustrates a cross-sectional view of an eccentric weight bar according to certain teachings of the present disclosure. 
         FIG. 8  illustrates an elevation view of the eccentric weight bar of  FIG. 7  in a tool string. 
     
    
    
     DETAILED DESCRIPTION 
     One embodiment of the current invention pertains to an abrasive perforating device that contains a flow channel through which fluid may pass for operation of additional tools.  FIG. 1A  is a diagram of such a tool in the closed position. Fluid enters the device  10  (referred to herein as a perforating sub) through inlet  11 , flows through channel  12  and exits the device through outlet  14 . Additional tools may be connected to device  10  via threads or other connecting means near inlet  11  and outlet  14 . The device  10  is designed so that inlet  12  is closer, along the path of the well, to the earth&#39;s surface than outlet  14 . 
     Device  10  contains a sleeve  20  that is disposed in the channel  12 . Sleeve  20  may slide longitudinally within channel  12 . Sleeve  20  has two sealing elements  22  that prevent fluid from passing between the sleeve  20  and the wall of the channel  16 . Device  10  also contains one or more jet nozzles  26 .  FIG. 1B  is a cross-sectional view illustrating one configuration of perforating jet nozzles. 
     In one embodiment of the present invention, perforating sub  10  is attached to coiled tubing, directly or via additional tools, on the inlet end and to a hydraulic bridge plug on the outlet end. One arrangement for the tools is shown in  FIGS. 3A and 3B . In  FIG. 3A  the perforating sub  10  of  FIG. 1A  is placed in a tool string  50  comprising a coiled tubing connector  62 , back pressure valve  64 , hydraulic disconnect  66 , crossover setting tool  70 , setting sleeve  72  and bridge plug  51 . Each of the devices in the tool string  50  of  FIG. 3A , other than the perforating sub  10 , are well known to those of skill in the art.  FIG. 3A  shows a tool string of the present disclosure as it is run in to the hole. The coiled tubing is injected into the well until the bridge plug is adjacent to the desired location. Fluid is run into the coiled tubing, through the inlet  11 , channel  12 , outlet  14 , and into the bridge plug  51 .  FIG. 3B  shows the same tool string  50  after the bridge plug  51  has been set. 
     In one embodiment of the present invention, the fluid inflates the bridge plug such that the bridge plug forms a seal against the walls of the well. When the fluid pressure reaches a certain level, the bridge plug setting tool is activated to release the bridge plug from the tool string  50 . Those skilled in the art will appreciate that any method for hydraulically inflating and releasing a bridge plug may be used in conjunction with this device, provided that any object conveyed through the device  10  must be small enough to pass through the opening  28  in the sleeve  20 . 
     The bridge plug  51  may also be set by other means that are well known in the art. Any bridge plug that is set in the well by controlling the fluid flow and/or pressure may be used as part of the present invention. As will further be appreciated by those of skill in the art, the bridge plug could be set with an explosion or through inflation as long as the plug once set is releasable from the perforating tool. For instance a simple shearing arrangement could be used. 
     When the bridge plug has been set and released, the abrasive perforating device  10  is positioned adjacent to the hydrocarbon bearing formation and a ball  21  is pumped down the coiled tubing into the device  10 . The ball  21  must be of appropriate size and material to seal against the top of sleeve  20 . The fluid pressure against sleeve  20  and the ball  21  is increased until sufficient pressure is obtained to shear the shear screws  25 . When the shear screws are sheared, the hydraulic pressure against sleeve  20  and ball  21  causes the sleeve to slide longitudinally along channel  12 . 
       FIG. 2A  shows device  10  with sleeve  20  in the open position after sliding along channel  12 . The movement of sleeve  20  is stopped by shoulder  29 . When sleeve  20  is in this position, as shown in  FIG. 2A , the jet nozzles  26  are open to channel  12 . As can be appreciated by those skilled in the art, the jet nozzles  26  contain a very narrow opening. Pressure in channel  12  forces fluid through the jet nozzles  26  to create a high velocity fluid stream. Solid particles, such as sand, are conveyed in this stream at or near the same velocity as the fluid. As the sand impacts on the casing or formation, it erodes the metal or rock and creates the desired perforation channels. In a preferred embodiment, 100 mesh sand is used as the abrasive to reduce tool erosion due to abrasive splash back in the well bore. 
       FIG. 4  shows an alternate abrasive perforating device that contains jet nozzles  26  at intervals along the length of device  40 . The sleeve  30  is modified so that it contains an extension  31  along the channel  12 . The extension contains a plurality of openings  34 . Sealing elements  32  isolate each opening such that fluid may not flow between the extension  31  and the wall of the channel  16 . When the ball  21  is engaged with the sleeve  30 , fluid pressure causes the shear screws  35  to break and the sleeve  30  with its extension  31  to slide longitudinally in the channel  12 . The sliding of sleeve  30  brings the openings  34  into line with the jet nozzles  26  and allowing fluid communication between channel  12  and the jet nozzles  26 . This fluid communication allows pressure on the fluid in the channel  12  to produce the high velocity fluid stream necessary for abrasive perforation. 
       FIG. 4  illustrates an abrasive perforating device with six jet nozzles  26  within a single longitudinal section of the device. However, embodiments with as few as one jet nozzle in any single longitudinal section are envisioned. The maximum number of jet nozzles in a single longitudinal section is limited only by the operational requirements and mechanical limitations of the device. 
       FIG. 5A  shows device  40  with sleeve  30  in position after sliding along channel  12 . Sleeve  30  stopped by a shoulder  38  on sleeve  30  and a retaining washer  39 . When sleeve  30  is in this position, the extension  31  is aligned in channel  12  so that the nozzles  34  in extension  31  are aligned with nozzles  26  in the body of device  40 . 
       FIGS. 1B and 2B  show six jet nozzles  26  in the cross sectional view and  FIG. 5B  shows 4 jet nozzles  26  in the cross sectional view. Those skilled in the art will appreciate that the present invention encompasses a range of jet nozzle configurations within a single cross section or across a number of cross sections. Depending on the requirements of the job, as few as one jet nozzle may be used. 
     By modifying the jet nozzles  26 , further functionality can be obtained. For example, those skilled in the art will appreciate that removing or “popping out” the jet nozzles  26  will create openings in the device that allow fluid to flow back into the device and through the tubing to the wellhead. Such flow back may be useful for well test or other operations. 
     The jet nozzles  26  may be removed using excess pressure on the nozzles, by reducing the strength of the nozzle material with a chemical treatment, or other means. In addition, removal of the jet nozzles  26  may allow fracture, acidizing, consolidation, cementing, or other fluids to be pumped into the well after perforations are complete. A packer may be included in the tool string above the abrasive perforating device to facilitate operations involving these fluids. Such packers are well known in the art. 
       FIG. 6  illustrates an embodiment of a three row jet nozzle embodiment of an abrasive perforating sub  65 . In this embodiment, there is a sliding sleeve  67  that slides within outer body  75 . When the perforating sub  65  is first run in the “open” position to allow fluid flow through the tool, the annular fluid channel  71  is sealed off with o-rings  69  on the sliding sleeve  67 . The sliding sleeve  67  is held locked open by shear pins  77 . When it is time to perforate, the sliding sleeve will be moved to the “closed” position by dropping a ball that seats on seat  79 . Shear pressure is then applied to shear pins  77  and the whole sleeve  67  moves down until fluid begins to pass into annular channel  71  and out jet nozzles  73 . 
       FIG. 7  illustrates an embodiment of an eccentric weight bar  80  that can be included in the tool string utilizing any configuration of the disclosed perforating tool. By use of the eccentric weight bar  80 , along with a standard swivel sub, the perforating tool can be made directional in wells that are not vertical. As seen in  FIG. 7 , eccentric weight bar  80  is designed so that the fluid channel  82  is not centered through the bar. This causes more metal to appear on one side of the fluid channel than on the other, as shown by A and B in  FIG. 7 . This causes the eccentric weight bar  80  to have naturally heavy side so that the side with the cross section shown as B on  FIG. 7  will gravitate to the bottom side of a non-vertical wellbore. The fluid channel  82  is preferably bored as far off center as possible while still allowing the tool joint to meet API Specifications. The length of the eccentric weight bar  80  can vary depending on overall tool string requirements but a preferred length is five feet. By using such an eccentric weight bar  80 , it allows for directional perforating as the device will align itself with the eccentric weight bar  80  as the bar notates due to gravity. The eccentric weight bar is preferably placed either just above or just below the perforating tool in the tool string shown in  FIG. 3 . A standard swivel sub can then be placed between the upper most device of either the eccentric weight bar, or the perforating sub, and the coiled tubing connector. As will be appreciated by those of skill in the art, the eccentric weight bar and the perforating sub could be combined into one unit. Further the perforating sub itself could be constructed with the counterbalance technique of the eccentric weight bar to provide alignment. 
       FIG. 8  shows an illustration of a tool string  100  with the perforating sub  65  of  FIG. 6  along with the eccentric weight bar  80  of  FIG. 7 . Common components to tool string  50  of  FIG. 3  are labeled the same as those labeled in  FIG. 3 . The other components are a swivel sub  84 , a lockable swivel sub  86 , a hydraulic setting tool  88 , a wireline adapter kit  90 , and a composite plug  92 . The illustrated tool string  100  is but one possible configuration of a tool string utilizing the eccentric weight sub and perforating sub of the present disclosure. Those of skill in the art will clearly configure tool strings to meet their particular needs without departing from the present disclosure.