Abstract:
A hybrid dump bailer is disclosed herein comprising a bailer tubes for containing a material, such as cement slurry, to be dumped. The hybrid dump bailer comprises a pressure pulse piston that is accelerated by a spring causing a pressure pulse to expel the material to be dumped. The hybrid dump bailer further comprises a collet, a retaining rod, a piston, valve, and a supply of pressurized fluid which is holds the pressure pulse piston in place while the spring is compressed. Once the valve is opened, releasing the pressurized fluid, the retaining rod separates from the collet allowing the pressure pulse piston to accelerate can produce the pressure pulse to dump the material.

Description:
TECHNICAL FIELD 
     This invention relates to a hybrid dump bailer for use in a wellbore, and a method of using a hybrid dump. 
     BACKGROUND OF THE INVENTION 
     In subterranean wells, such as oil and gas wells, there are occasions when material, such as cement slurry or other chemicals, need to be introduced into the well bore. One common example is the introduction of cement slurry into a well bore to seal the well bore or the introduction of cement slurry above a bridge plug to seal off a section of the well bore. This is typically accomplished by what is commonly known in the industry as a dump bailer. Dump bailers are introduced or carried into a subterranean well on a conduit, such as wire line, electric line, continuous coiled tubing, threaded work string, or the like, and discharge or “dump” the cement slurry into the well bore. 
     There are two general types of dump bailers: (1) gravity feed bailers and (2) positive displacement bailers. Gravity feed dump bailers are some of the most commonly used dump bailers in the industry. One reason for this is its simplicity. However, gravity dump bailers present many drawbacks. Chief among them is the possibility of “stringing,” which occurs when the cement slurry does not completely discharge at the desired depth and the cement slurry is strung out through the well. Additionally, most gravity dump bailers include a seal, such as a ceramic disk, that is broken to allow the cement slurry to flow. The seal can be broken by a pin or, more frequently, shattered by an explosive charge. Positive displacement dump bailers address many of the deficiencies of the gravity dump bailers by elimination of the explosive charge and by providing force to expel the cement slurry out of the bailer. 
     There are several types of positive displacement dump bailers. Most positive displacement dump bailers rely on a sweep piston use to force the cement slurry or material out of the bailer. These systems may use a weight, either alone or with some actuating system, to force the piston down the bailer or the systems may use the pressure differential between atmospheric (well bore) pressure and the internal tool pressure to push the piston down the length of the bailer. While the positive displacement bailers overcome many of the deficiencies of the gravity dump bailers, they have several drawbacks. One of the main drawbacks is the use of bailer tubes, which hold the cement slurry. Because the sweep piston is forced through the bailer tubes, the bailer tubes must have a consistent inner diameter with a smooth wall bore to prevent the sweep piston from becoming lodged in the bailer tube and to reduce the friction between the pipe wall and the cement slurry. Additionally, because multiple bailer tubes are typically used, care must be taken not to damage the threaded connections. If the threaded connections are over tightened, the inner diameter of the bailer tube could neck down, causing the sweep piston to hang up. 
     Therefore there exists to address the shortcomings of the current art exists. 
     BRIEF SUMMARY OF THE INVENTION 
     In one aspect, the present invention utilizes a hybrid dump bailer for use in introducing material, such as cement slurry, into a well bore. The hybrid dump bailer includes a tool body having a longitudinal tool bore; at least one bailer tube; the bore including a piston with a seal rod and a pressure pulse piston with a connector rod and collet, wherein the collet has been configured to receive the seal rod; and a lower connection mechanism for connecting the tool body to bailer tubes. The dump bailer also includes a piston spring and a pressure pulse piston spring used to move the piston and pressure pulse piston. 
     Preferably, the hybrid dump bailer includes a head space above the piston and also includes a passageway, wherein the passageway is configured to allow fluid communication between the head space and tool body. 
     It is preferred that the hybrid dump bailer include a fluted connector, wherein the fluted connector and the lower tandem sub limits the travel of the pressure pulse piston. 
     It is also preferred that the hybrid dump bailer also includes a solenoid valve, wherein the solenoid valve can be remotely opened to allow fluid communication between the headspace and the upper solenoid housing. 
     In this aspect of the invention, the hybrid dump bailer also includes a plug, wherein the plug is secured in the bailer cage by a shear pin. 
     In another aspect, the present invention hybrid dump bailer includes a tool body having a longitudinal tool bore. The tool body also includes a top contact sub, a solenoid valve housing, a solenoid valve base, an inflow housing, a metering collet sub, a pressure chamber, a lower tandem sub, and a lower piston housing at least one bailer tube. The bore includes a piston with a seal rod and a pressure pulse piston with a connector rod and collet, wherein the collet has been configured to receive the seal rod; and an lower connection means for connecting the tool body to bailer tubes. 
     Preferably, the hybrid dump bailer also includes a piston spring and a pressure pulse piston spring. 
     It is also preferred that the hybrid dump bailer also includes a head space above the piston and a passageway through the solenoid valve base, wherein the passageway is configured to allow fluid communication between the head space and solenoid valve housing. 
     This aspect of the invention also includes a fluted connector, wherein the fluted connector and the lower tandem sub limit the travel of the pressure pulse piston. 
     It is also preferred that the hybrid dump bailer also includes a solenoid valve, wherein the solenoid valve can be remotely opened to allow fluid communication between the headspace and the upper solenoid housing. 
     The hybrid dump bailer also includes a plug, wherein the plug is secured in the bailer cage by a shear pin. 
     It is also preferred that the hybrid dump bailer where in the top contact sub, solenoid valve housing, solenoid valve base, inflow housing, metering collet sub, pressure chamber, lower tandem sub, and lower piston housing are connected by a threaded connection; however other connections such as welded connections are contemplated. 
     In another aspect, the invention provides a resetting tool for a hybrid dump bailer, which includes an inlet valve; a relief valve; a compression piston; and a compression rod. 
     Further aspects of the invention will be apparent from the following description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically depicts one embodiment of the hybrid bailer of this invention in the ready to run position; 
         FIG. 1A  schematically depicts a close up view of the contact sub and solenoid housing of the hybrid dump bailer of this invention; 
         FIG. 1B  schematically depicts a close up view of the solenoid valve base and the inflow housing of the hybrid dump bailer of this invention; 
         FIG. 1C  schematically depicts a close up view of the metering sub and pressure pulse chamber of the hybrid dump bailer of this invention; 
         FIG. 1D  schematically depicts a close up view of the tandem sub and lower pressure pulse chamber of the hybrid dump bailer of this invention; 
         FIG. 1E  schematically depicts a close up view of the lower sub and the bailer cage of the hybrid dump bail of this invention; 
         FIG. 2  schematically depicts one embodiment of the hybrid dump bailer of this invention after the tool has been run; 
         FIG. 3  shows a typical gel strength v. time curve for a cement slurry; 
         FIG. 4  schematically depicts the hybrid dump bailer and resetting tool of this invention; and 
         FIG. 5  schematically depicts the hybrid dump bailer and resetting tool of this invention once the tool case has been reset with the resetting tool. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As used herein, “a” or “an” means one or more than one. Additional, distal refers to the end of the element closest to the setting mandrel of the setting tool and proximal end refers to the end of the element closest to the firing head of the setting tool. 
     The methods and apparatus of the present invention will now be illustrated with reference to  FIGS. 1 through 5 . It should be understood that these are merely illustrative and not exhaustive examples of the scope of the present invention and that variations which are understood by those having ordinary skill in the art are within the scope of the present invention. 
     Turning now to  FIG. 1 , which shows hybrid bailer  100  loaded and energized to discharge cement slurry into a well bore. While this example will discuss the discharge of cement slurry into the well bore, it is also contemplated that the hybrid dump bailer  100  could be used to deposit other material such as sand and chemicals. The hybrid dump bailer  100  includes a tool body made up of top contact sub  10 , solenoid valve housing  20 , solenoid valve base  30 , inflow housing  40 , metering collet sub  51 , pressure pulse chamber  50 , lower tandem sub  60 , and lower piston housing  70 . Bailer tubes  81 , bottom sub  80 , and bailer cage  90  are also connected to the tool body to complete to hybrid dump bailer. Each section will be discussed in further detail below. 
     The top contact sub  10 , which is shown in close-up in  FIG. 1A , is connected to solenoid valve housing  20  by a threaded connection. While other connections, such as welded connections, are contemplated, the threaded connection is preferred because it allows the top contact sub to easily be removed for service or replacement. To further seal the connection, o-rings  18  are used. Polymer and copolymer o-rings such as Buna-N or nitrile rubber are preferred; however, other materials are contemplated and the selection will depend on the service conditions the hybrid dump bailers are exposed to. The top contact sub  10  includes a central bore  12 , which houses a spring  14  and a contact pin  16 . The central bore  12  is lined with an insulating material  13 , such as polyether ether ketone (“PEEK”), to prevent top contact sub  10  from becoming energized. Other electrical insulators, such as ceramics, carbon, rubbers, and plastics, can also be used. When the top contact sub  10  is fully mated with solenoid valve housing  20 , spring  14  is compressed as contact pin  16  is connected to electrical contact receptacle  21 . The force exerted by compression of the spring  14 , forces the contact pin  16  to seat within the receptacle of contact receptacle  21  thereby passing electrical current from contact pin  16  to receptacle  21 . 
     Electrical contact receptacle  21  is located within solenoid valve housing  20  and is surrounded by PEEK insulator  23 . As discussed above, other insulating material may be used. The receptacle is connected to brass contact  22 . A ceramic electrical feed-thru  24  is connected to brass contact  22 . Feed-thru  24  passes electrical current from brass contact  22  to flex spring contact  25  and flex spring  26 , which is in contact with solenoid valve contact  27 . Solenoid valve housing  20  also includes an opening, which is plugged by plug  29 . 
     Solenoid valve base  30  and inflow housing  40  are shown in close-up in  FIG. 1B . Solenoid valve base  30  is connected on top side to solenoid valve housing  20  and on the bottom side to inflow housing  40  by a threaded connection. As previously discussed other connection mechanisms, such as welded connections and the like, are contemplated; however, the threaded connection is preferred. Additionally, o-rings  38  are incorporated to seal the device. Solenoid valve base  30  has recess designed to receive solenoid valve  32 , a side opening, which is plugged by plug  33 , check valve  35 , and a passageway  36 . Check valve  35  is located in a passageway that provides fluid communication between the side opening and the bottom of solenoid valve base  30 . When plug  33  is removed, fluid is allowed to pass through check valve  35  and into head space  41 , which is created by the bottom of solenoid valve base  30 , inflow hosing  40 , and piston  42 . Check valve  35  prevents flow of fluid from head space  41  through the check valve to the side opening. 
     Passageway  36  connects head space  41  with solenoid valve  32 . When solenoid valve actuator  31  (see  FIG. 1A ) is energized, the solenoid valve  32  opens, allowing fluid to flow from head space  41  through passage way  36  and into head space  28  of solenoid valve housing  20  (see  FIG. 1A ). Passageway  36  also includes a side opening  37 . When solenoid valve base  30  is completely connected to solenoid valve housing  20 , side opening  37  is sealed. Solenoid valve housing  20  can be backed off from solenoid valve base  30 , thus exposing side opening  37  to allow any pressure in head space  41  to be bled off, should, for example, solenoid valve  32  not function properly. 
     As shown in  FIG. 1C , inflow housing  40  is connected on its other end to metering collet sub  51  via a threaded connection. As previously discussed, this is the preferred connection; however, other connections are contemplated. Inflow housing  40  also includes inflow passageway  49 . This allows this section of bailer  100  to operate at atmospheric pressure. Piston  42 , which is located within the centre bore of inflow hosing  40 , is connected to seal rod  43 . A piston spring  44  is positioned between piston  42  and metering collet sub  51 . 
     Metering collet sub  51  has a central bore through which seal rod  43  passes. Seal rod  43  is designed to be received and held by collet  52 . Plug  33  is removed and a fluid is pumped through check valve  35  into head space  41 . Although hydraulic fluid is preferred, other fluids such as compressed air or other gases can be used. In normal operation, the pressure in head space  41  is increased to approximately 400 psig above ambient. This pressure provides the force necessary to push piston  42  down and compress piston spring  44 , thus forcing sealing rod  43  into collet  52 . 
     The other end of metering collet sub  51  is connected by threaded connection to pressure pulse chamber  50 . In addition to collet  52 , pressure pulse chamber  50  includes upper connector rod  53 , pressure pulse piston spring  54 , collet base  55 , fluted connector  56  (see, e.g.  FIG. 1 ), inflow passageways  57  (see  FIG. 1D ), and lower connector rod  58 . Collet  52  is connected to upper connector rod  53  via a threaded connection. The other end of upper connector rod  53  is connected to fluted connector  56  via a threaded connection. Again, other connection means, such as a welded connection, are contemplated; however a threaded connection is preferred to allow for ease of replacement of parts and assembly of the hybrid dump bailer. Pressure pulse piston spring  54  is located between collet base  55  and fluted connector  56 . Pressure chamber inflow passageways  57 , like inflow passageways  49 , allow well bore fluid to enter bailer  100 , thus equalizing the pressure difference between the well bore and the bailer. Because the pressure chamber is open to the atmosphere and well bore fluid is in the interior, connector  56  is fluted to allow fluid to flow past the connector. 
     Referring to  FIG. 1D , lower connector rod  58  is connected to fluted connector  56  via a threaded connection. Lower connector rod  58  passes through tandem sub  60 , which is connected on its upper end to pressure chamber  50  and on its lower end to lower piston housing  70  via a threaded connection. Again, other connections are contemplated, but a threaded connection is preferred. The bottom end of lower connector rod  58  is connected to lower pressure pulse piston  71 . Lower piston housing  70  is connected at its lower end via threaded connection to bailer tube  81 . Depending on the amount of material to be introduced into the well bore, one or more bailer tubes may be connected. 
     One advantage of the invention is that the bailer tubes do not have to meet the exacting standards, nor do they need to be treated with as much care, as the prior art bailer tubes. The prior art bailer tubes had to be manufactured with exacting internal diameter tolerances because small restrictions in the inner diameter could cause mis-runs in gravity bailers. Moreover, in prior art positive displacement bailers, which force a piston through the bailer tubes to dump the cement, variances in the inner diameter, can cause the piston to hang up, also causing mis-runs. Further, extra care must be taken when making up a section of bailer tubes because over torqueing the connection can cause the inner diameter to narrow at the connection. The new design of this invention is not dependent on the consistency of the inner diameter. This allows the bailer tubes to be manufactured from less expensive material and methods. 
     Referring to  FIG. 1E , the last bailer tube  81  is connected to bottom sub  80 . Bottom sub  80  has a plug  82 . Plug  82  is attached to bottom sub  80  by shear pin  83 . Shear pin  83  can be a screw or other pin which holds the plug in pace. In the preferred embodiment, shear pin  83  is a brass screw that has a hole drilled in the center of the screw to reduce the amount of shear force necessary to shear the screw to approximately 200-250 lb F . Alternative materials, such as metal alloys and plastics can also be used as long as the shear force can be controlled. Bottom sub  80  is then connected to bailer cage  90 . Bailer cage  90  includes many openings used to direct the dump material in the well. As shown in  FIG. 2 , bailer cage  90  also serves to capture plug  82  so it can be reused. 
     Referring back to  FIG. 1 , hybrid bailer  100  is shown in the ready-to-run position. In this position, hydraulic fluid, which has been pumped into head space  41 , forces piston  42  down, compressing piston spring  44  between piston  42  and collet base  51 . Collet  52 , which receives the distal end of seal rod  43 , is a spring finger collet that grips the distal end of seal rod  43  when pressure pulse piston spring  54  is compressed between fluted connector  56  and collet base  51 . Depending on the amount of cement slurry to be dumped, a number of bailer tubes  81  containing cement slurry are attached to the lower piston housing  70 . In the preferred embodiment, a water pad of the type know in the art is placed on top of the cement slurry. 
     Referring to  FIG. 2 , once hybrid bailer  100  is lowered into the well bore to the location were the cement slurry is to be dumped, solenoid valve  32  is opened, allowing the hydraulic fluid to flow from head chamber  41  through passageway  36  and into void space  28  of solenoid valve housing  20 , thereby relieving the pressure in head chamber  41 . This allows spring  44  to push piston  42  up, thereby disconnecting rod  43  from collet  52 . Once rod  43  is disconnected from collet  52 , spring  53  then forces fluted connector  56  down, thereby accelerating pressure pulse piston  71 . As pressure pulse piston  71  accelerates it strikes the water pad creating a pressure pulse, or shock wave, that is transmitted to the cement slurry. The pressure pulse creates a force that shears shear pin  83 , there by freeing plug  82 , which travels to and is contained by the bottom of bailer cage  90 . 
     Once the cement slurry is mixed and added to the bailer tubes, the cement slurry begins to gel. This is due to a number of factors including: (1) the ionic charges from the various slurry components; (2) the density of the slurry; (3) the slurry remaining static in the bailer tubes; (4) the elevated temperatures and pressures the slurry is subject to prior to dumping; and (5) the long time delay between the time the slurry is mixed and the time it is dumped. Once the cement slurry begins to gel, it becomes static has a tendency to remain static. Thus, once the cement slurry gels, it resists flow. In gravity and positive displacement bailers, this is one of the most common causes of mis-runs and stringing of cement in the well bore.  FIG. 3  shows a predicted cement slurry gel strength time curve. As shown in the time curve, once the cement slurry is mixed and poured into the bailer tube, it begins to quickly gain gel strength while the bailer is run in the well bore. It may take upwards of two hours from the time the cement is mixed before it is dumped into the well bore. Thus, to guarantee that the cement slurry will flow out of the dump bailer, pressure pulse piston  71  must create sufficient force to break the cement slurry gel. Once the gel is broken, the cement slurry has favorable rheological properties, allowing the cement slurry to flow out of bailer cage  90 .  FIG. 3  shows that once hybrid bailer  100  is dumped, the shock wave breaks the gel causing the gel strength to quickly drop. Once the cement slurry is in the well casing, it once again becomes static and the gel strength rapidly increases until the cement is set. 
     Once hybrid bailer  100  has dumped the cement slurry into the well bore, it is raised to the surface and bailer tubes  81  are removed. Bailer cage  90  is also removed, cleaned, and plug  82  is recovered and shear pin  83  is removed. Plug  82  is then inspected and, if there is no damage, it is reinstalled in bailer cage  90  using a new shear pin  83 . Bailer tubes  81  are cleaned and inspected. Depending on the amount of cement slurry to be dumped, additional bailer tubes may be added or removed and the bailer tubes can then be refilled with cement slurry and a water pad. 
     Referring to  FIG. 4 , hybrid bailer  100  is now reset by attaching lower piston housing  70  to resetting tool  200 . Resetting tool  200  includes inlet valve  205 , relief valve  210 , compression rod  220 , and compression piston  225 . Compression rod  220  is connected to compression piston  225  on one end and has a notch that mates with the bottom of pressure pulse piston  71 . Referring to  FIG. 5 , after resetting tool  200  is attached to the bailer, relief valve  210  is closed and inlet valve  205  is opened, allowing a high pressure fluid to be introduced into resetting tool  200 . This fluid can be high pressure water, air, or any other fluid with sufficient pressure to force lower piston  71  up, thereby compressing pressure pulse piston spring  54  between connector  56  and collet base  55 . Once pressure pulse piston spring  54  has been compressed, plug  33  is removed. A solenoid valve  32 , which is normally closed, is energized to open so the hydraulic fluid can be pumped into head chamber  41  forcing piston  42  down, thereby compressing piston spring  44  and forcing rod  43  into collet  52 . Once head chamber  41  is charged, plug  33  is replaced, inlet valve  205  is closed, and resetting tool  200  is removed. Once removed, relief valve  210  is opened to relieve the pressure in resetting tool  200 . Finally, the bailer tubes can then be reattached and hybrid bailer  100  is ready to run again.