Abstract:
An apparatus and method is used in the cleaning out of sand in underbalanced gas wells. The present invention includes a valve subassembly equipped with an emergency shutin device to remotely control the actuation of the valve via an air or hydraulic control line. Operatively coupled to the inlet of the valve subassembly is a swivel subassembly which further enables the coupling to a tubing string. A lifting assembly attaches the valve subassembly to an elevator of a well service rig. A hardened elbow coupled to an outlet of the valve subassembly directs the gas/sand mixture being removed from the well through a hose to a collection pit. The use of the apparatus of the present invention in a sand cleanout operation allows joints of pipe to be tripped into and out of the tubing string all the while keeping the emergency shutdown device actuator connected and operational.

Description:
FIELD OF THE INVENTION 
   The present invention relates to the field of tubing valves used in the removal of sand from underbalanced hydrocarbon producing wells. 
   BACKGROUND OF THE INVENTION 
   In hydrocarbon producing wells, in particular, natural gas wells, multiple gas producing formations in the vertical strata of the gas field may be present. A well may pass from multiple formations along its vertical height. When drilling a well that contains multiple formations, it is common practice to place a plug in the well to separate vertically adjacent formations. To protect the plug itself, it is known to place a sufficient amount of sand on top of the plug. A well having sand placed in this manner is referred to an “underbalanced well”. In a well D with multiple formations A, as shown in  FIG. 1 , plug B is placed in well D to separate each formation A. Sand C is then placed on top of each plug B. 
   When the uppermost formation has almost been depleted, the plug and the sand separating the uppermost formation and the formation beneath it needs to be removed. To remove the sand, it is known to lower a string of tubing into the well until the lower end of the tubing is near the sand. Coupled on top of the tubing is a valve subassembly, such as a ball valve subassembly commonly known to those skilled in the art. A safety valve subassembly is often used on top of the first valve subassembly. The safety valve subassembly typically incorporates a valve actuator known as an emergency shut-in device or “ESD”. Due to the explosive nature of natural gas, the ESD is operated by a compressed air or hydraulic line as opposed to an electrically-controlled actuator. The ESD is controlled by a remotely located switch situated near the floor of the well service rig so that it is easily accessible by an operator. 
   When a joint of tubing is lowered into a well, the first valve subassembly is closed. The tubing may be rotated about its longitudinal axis so that it may descend into the well easily. This requires that the control line to the ESD of the safety valve subassembly to be disconnected as the safety valve subassembly will also rotate as the tubing is lowered into the well. Once the tubing is positioned to remove the sand in the well, the control line is reconnected to the ESD and the first valve subassembly is opened thereby allowing the pressure of the formation to force gas up the tubing drawing along sand with it. In the event of an emergency, the ESD can be activated by an operator to close the safety valve subassembly and stop the sand cleanout operation. 
   If additional joints of tubing are required to be tripped into the tubing string, the first valve subassembly is closed and the control line to the ESD is disconnected. The connection between the first valve subassembly and safety valve subassembly is broken and another joint of tubing is inserted between the first valve subassembly and the safety valve subassembly. The second valve subassembly is also placed between the second joint of pipe and the safety valve subassembly. The second valve subassembly is initially placed in the closed position. The first valve subassembly is then opened and the string of tubing is then lowered further into the well. When the string is in position, the control line is reattached to the ESD and the second valve subassembly is then opened to continue with the sand cleanout operation. If multiple joints of tubing are required, this procedure is repeated for each joint of tubing placed in the tubing string. 
   As the safety valve subassembly with the ESD is part of the tubing string, the control line must be repeatedly disconnected and reconnected for each joint of tubing added to the tubing string. This procedure adds considerable time and inconvenience to the operation. To avoid this inconvenience, some well service operators may choose not to use a safety valve subassembly with an ESD at all. This causes a potentially hazardous situation for operators as there is no standby emergency shutdown mechanism to shut down the operation in the event of an emergency. 
   Therefore, it is desirable to have a safety valve subassembly with an ESD that does not have to have its control line disconnected and reconnected every time a joint of tubing is tripped into or out of the tubing string. 
   SUMMARY OF THE INVENTION 
   The present invention is an apparatus and method for use in cleaning out sand from an underbalanced well that allows the ESD of a safety valve subassembly to remain connected to its control line when joints of tubing are tripped into the tubing string. 
   The apparatus of the present invention is a valve subassembly, as well known to those skilled in the art, having a tubing swivel subassembly rotatably coupled to the lower or inlet end of the valve subassembly. The valve subassembly has a valve mechanism, such as a ball valve, adapted to be operated by a valve actuator or ESD. The ESD is connected to a control line operated by a remotely located switch near the platform of the well service rig. 
   In an illustrative embodiment of the present invention, one end of a hardened elbow, such as a Chicksan™ elbow, is coupled to the upper or outlet end of the valve subassembly. A high pressure hose is coupled to the other end of the elbow to direct sand to a pit. The use of a hardened elbow is beneficial as the material wear properties of the elbow absorb the brunt of the abrasive effects of sand being blown out of the well by the formation pressure and through the valve subassembly. This embodiment is suitable for wells having formation pressures greater than 2500 psi. 
   In this illustrative embodiment, the valve subassembly is supported by a valve cradle in which the valve subassembly is fastened to. The valve cradle also provides the interconnection between the valve subassembly and the swivel subassembly. A fork assembly attached to the elevator of the service rig supports the valve cradle by having the ends of the fork legs pivotally attached to said valve cradle. A singular rod projecting upwards from the upper end of the fork provides the means to attach to the apparatus to the elevator of a well service rig. 
   In an alternate embodiment, the valve subassembly has an exit port extending through the sidewall of the valve, the port located above the valve mechanism. The exit port has a hardened elbow, such as a Chicksan™ elbow, attached to it. A high pressure hose is connected to the other end of the elbow directs the sand to a pit. In place of a fork assembly, this alternate embodiment uses a pickup subassembly threaded into the upper or outlet end of the valve subassembly. The pickup subassembly, in turn, couples the valve subassembly to the elevator of the service rig. A sand plug is fitted within the valve subassembly between the exit port and the pickup subassembly. The sand plug is placed within the valve subassembly to absorb the brunt of the abrasive effects of the sand flowing through the valve subassembly and out the exit port. Due to the sharp bend the flow of sand makes as it passes through the valve subassembly and the exit port, the sand can wear or abrade the internals of the valve subassembly. Accordingly, this embodiment is more suitable for wells having formation pressures less than 2500 psi. 
   The method of the present invention comprises attaching the apparatus of the present invention to the elevator of a well service rig. The ESD control line is attached to the valve actuator on the valve subassembly and remains connected all throughout the sand cleanout operations. A hardened elbow and hose are attached to the valve subassembly to direct the sand removed from the well to a pit. A second valve subassembly is coupled to coupling means disposed on the lower end of the swivel subassembly of the apparatus followed by a joint of tubing being coupled to the second valve subassembly. Initially, the second valve subassembly is closed. As the joint of tubing is lowered into the well, the tubing may be rotated during its descent into the well. The swivel subassembly allows the tubing string to rotate while the valve subassembly remains stationary. Once the tubing has been lowered into position, the second valve subassembly is opened allowing the gas to rise up through the tubing and drawing the sand with it. The gas/sand mixture rises up the tubing, through the open second valve subassembly, through the apparatus of the present invention, and out through the hardened elbow and hose into the pit. The sand lands into the pit whereas the gas is simply released into the atmosphere. 
   When another joint of tubing is needed to be tripped into the tubing string, the second valve is closed and a joint of tubing along with a third valve subassembly (also in a closed position) is tripped into the tubing string between the swivel subassembly and the second valve subassembly. The second valve subassembly is opened and the tubing string is then further lowered into the well. Once the tubing string has been lowered into position, the third valve subassembly is opened allowing gas to clear out the sand in the procedure described above. 
   All the while, the control lines of the ESD of the valve subassembly remains connected. It does not have to be disconnected and reconnected every time a joint of tubing is tripped into the tubing string. This saves time and speeds the sand cleanout operation. In the event of an emergency, the cleanout operation can be stopped by operating the remove switch for the ESD thereby closing the valve subassembly. 
   Broadly stated, one aspect of the present invention is an apparatus for cleaning out sand from an underbalanced hydrocarbon producing well, comprising: a valve subassembly having a valve body comprising: an upper end having coupling means, a lower end adapted to couple to a swivel subassembly, a passageway disposed within said valve body providing communication between said upper and lower ends, and a valve mechanism disposed in said passageway for opening and closing said passageway; a swivel subassembly operatively coupled to said lower end of said valve body. 
   Broadly stated, another aspect of the present invention is a method for cleaning out sand from an underbalanced hydrocarbon producing well, the method comprising the steps of: attaching an apparatus consisting of: a valve subassembly having a valve body comprising: an upper end having coupling means, a lower end adapted to couple to a swivel subassembly, a passageway disposed within said valve body providing communication between said upper and lower ends, and a valve mechanism disposed in said passageway for opening and closing said passageway, a swivel subassembly operatively coupled to said lower end of said valve body, and lift support means operatively coupled to said valve subassembly for attaching with an elevator of a well service rig to an elevator of a well service rig, the valve mechanism of said apparatus in an open position; attaching a first joint of tubing to a lower end of second valve subassembly; attaching an upper end of said second valve subassembly to the swivel assembly of said apparatus, said second valve subassembly in a closed position; lowering said first joint of tubing into said well; and opening said second valve subassembly whereby the pressure of a hydrocarbon formation in said well forces said sand up said tubing and exiting through said apparatus. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is a front cross-sectional view of a well formation during sand cleanout operations of an underbalanced hydrocarbon producing well. 
       FIG. 2  is a front elevational view of a first embodiment of the apparatus of the present invention. 
       FIG. 3  is a side elevational view of the first embodiment of the apparatus of the present invention. 
       FIG. 4  is an exploded front view of the first embodiment of the apparatus of the present invention. 
       FIG. 5  is a front elevational view of a second embodiment of the apparatus of the present invention. 
       FIG. 6  is a side elevational view of the second embodiment of the apparatus of the present invention. 
       FIG. 7  is an exploded front view of the second embodiment of the apparatus of the present invention. 
       FIG. 8  is a front elevational view of the first embodiment of the apparatus of the present invention in operation. 
   

   DETAILED DESCRIPTION OF EMBODIMENTS 
   Referring to  FIGS. 2 ,  3  and  4 , a first embodiment of the present invention shown. Apparatus  50  comprises a valve subassembly  62  having ball valve  63 . Valve subassembly  62  can be provided as a 5000 psi, 27/8″ slimline ball valve subassembly which is readily and commercially available and as well known to those skilled in the art. Swivel subassembly  70  is rotatably coupled to valve subassembly  62  with swivel cap  74 . Disposed between valve subassembly  62  and swivel subassembly  70  are o-rings  64 , teflon ring  66  and thrust bearing  68 . Disposed between swivel subassembly  70  and swivel cap  74  are thrust bearings  72 . As shown in  FIG. 4 , swivel subassembly  70  can be a cylindrical or tubular member having upper end  90 , lower end  92  and retaining ring  94  disposed therebetween. Upper end  90  passes through thrust bearing  68 , teflon ring  66  and o-rings  64  into opening  91  disposed at the lower end of valve subassembly  62  that is adapted to receive swivel subassembly  70 . Upper end  90  is inserted into opening  91  until stopped by retaining ring  94 . Thrust bearing  72  is fitted over lower end  92  of swivel subassembly  70 . Swivel cap  74 , having opening  93  extending therethrough, is slipped over coupling threads  88  disposed on lower end  92  of swivel subassembly  70  and is operatively coupled to valve subassembly  62  thereby sandwiching retaining ring  94  between valve subassembly  62  and shoulder  95  of swivel cap  74 . As obvious to those skilled in the art, swivel cap  74  can be threaded to valve subassembly  62  or it can be fastened using any other suitable means. By coupling swivel subassembly  70  to valve subassembly  62  in this manner, swivel subassembly  70  can rotate relative to valve subassembly  62  while valve subassembly  62  remains stationary. 
   Sandplug  54  is threaded onto pickup subassembly  52  before pickup subassembly  52  is threaded into box end  61  of valve subassembly  62 . Ring  80  provides means for attaching a chain or a hook from a winch cable to apparatus  50  whereby apparatus  50  can be raised or lowered. O-ring  56  provides a seal between sand plug  54  and valve subassembly  62 . Sleeve  60  and breakout band  58  further secure pickup subassembly  54  to valve subassembly  62 . Port  65  extends through the sidewall of valve subassembly  62  and is positioned between ball valve  63  and box end  61 . A hardened elbow, such as those made by Chicksan™ is attached to port  65  to direct the flow of sand through a hose (not shown) to a pit for collecting the sand. 
   Due to the abrasive effects of sand flowing through the apparatus and the sharp bend taken by the flow of sand takes to exit valve subassembly  62  through port  65 , the use of this first embodiment is generally limited to cleaning sand from wells having formations pressures not greater than 2500 psi. ESD actuator  78  is mounted to valve subassembly  62  via ESD mounting tower  76  and operates the ball valve mechanism (not shown) of valve subassembly  62 . The control line (not shown) connects ESD actuator  78  to a remotely located control switch (not shown) typically mounted near the platform of a well service rig (not shown). 
   Referring to  FIGS. 5 ,  6  and  7 , a second embodiment of the apparatus of the present invention is illustrated. Apparatus  10  comprises valve subassembly  16 , valve cradle  20 , swivel crossover  22 , swivel subassembly  26 , swivel cap  24 , lifting assembly  12 , lifting lugs  18  and elbow  14 . In this embodiment, valve subassembly  16  is the same type of subassembly as valve subassembly  62  with exception of valve subassembly  16  not having a port  65 . Valve subassembly  16  sits in valve cradle  20  and is secured in place with setscrews. Swivel crossover  22  is threaded into valve cradle  20 . Swivel subassembly  26  can comprise upper end  40 , lower end  42  and retaining ring  41  disposed therebetween. Lower end  42  can further comprise threads  43 . Upper end  40  of swivel subassembly fits within swivel crossover  22 . Swivel cap  24  slips over swivel subassembly  26  and is threaded onto swivel crossover  22 . This secures swivel subassembly  26  to swivel crossover  22  but still allows swivel subassembly  26  to rotate within swivel crossover  22 . Coupled to the top of valve subassembly  16  is elbow  14 . Elbow  14  is a hardened device, as made by Chicksan™ as an example, for bearing the brunt of the abrasive effects of sand flowing through apparatus  10  under pressure. As the placement of elbow  14  on top of valve subassembly  16  allows sand to flow straight through valve subassembly  16 , this second embodiment is generally suitable for cleaning sand from underbalanced wells having formations pressure greater than 2500 psi, but not more than the pressure rating of valve subassembly  16 , where the abrasive effects of sand flowing under such pressures would quickly wear out the first embodiment of the apparatus of the present invention. 
   ESD actuator  34  is mounted to valve subassembly  16  via ESD mounting tower  36  and operates the ball valve mechanism (not shown) of valve subassembly  16 . The control line (not shown) connects ESD actuator  34  to a remotely located control switch (not shown) typically mounted near the platform of a well service rig (not shown). 
   To support apparatus  10 , lifting assembly  12  is pivotally attached to valve cradle  20 . Lifting assembly  12  includes fork head  22  having two legs  13  secured to it by locking caps  30 . At the bottom of legs  13  are ends  15  having apertures for fitting over lugs  18 . Lugs  18  are threaded into valve cradle  20 . Ends  15  slide over lugs  18  and are secured by circlips  21  fitted into grooves  19  of lugs  18 . Rod  32  is threaded into yoke  28  and is capable of being connected to an elevator of a well service rig. 
   In operation, as shown in  FIG. 8 , the first embodiment of the apparatus of the invention, apparatus  50  is supported by pickup subassembly  52  which, in turn, is attached to an elevator of a well service rig (not shown). Operatively coupled to the inlet of valve subassembly  62  via swivel subassembly  70  is valve  82   a  which is, in turn, coupled to tubing  84   a . Valve  82   a  is coupled to coupling threads  88  disposed on lower end  92  of swivel subassembly  70 . Additional valves  82   b  and tubing  84   b  may be included to form string  38  that is inserted to the well through wellhead  86 . Attached to valve subassembly  62  is ESD actuator  34 . Control line  35  couples ESD actuator  34  to a remotely located switch (not shown). Elbow  14  connects a port (e.g.,  65  shown in  FIG. 4 ) of valve subassembly  62  to hose  67 . Hose  67  leads to an open pit (not shown) where sand is directed. 
   Valve  82  is closed when tubing  84  is inserted into the well through wellhead  86 . Once valve  82  is positioned above wellhead  86 , valve  82  is opened to allow gas from the well formation to rise through tubing  84  and to exit through the port of valve subassembly  62 , carrying sand along with it. The gas/sand mixture flows through hose  67  to the pit where the sand collects and the gas is released to the atmosphere. Additional joints of tubing  84  and valves  82  can be added to string  38  to continue to process. 
   During the sand cleanout operation, line  35  is connected to ESD actuator  34 . In lowering tubing  84  into the well, string  38  may be rotated to ease the descent of string  38  into the well. Swivel subassembly  70  allows string  38  to rotate while keeping valve subassembly  62  stationary. In the event of an emergency requiring the sand cleanout operation to be terminated, an operator simply activates the remote control switch to cause ESD actuator  34  to close the ball valve of valve subassembly  62 . The advantage of the present invention is that when joints of tubing  84  are tripped into or out of string  38 , line  35  does not have to be continuously disconnected and reconnected to ESD actuator  34  for each joint of tubing. This speeds up the sand cleanout operation and results in considerable time savings for the operator. It also maintains a degree of safety during these operations as ESD actuator  34  is kept operational even when joints of tubing  84  are tripped into or out of string  38 . 
   Using the second embodiment of the apparatus of the present invention in operation is similar to that of the first embodiment. The only difference is that elbow  14  is attached to the top of valve subassembly  16 . As discussed above, the first embodiment is generally used to clean out wells having formation pressures not greater than 2500 psi whereas the second embodiment is used with well with formations pressures greater than 2500 psi. 
   Although a few illustrative embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention. The terms and expressions used in the preceding specification have been used herein as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims that follow.