Abstract:
A downhole valve assembly, including a line operatively arranged to carry a fluid, a splitter arranged on the line, the splitter dividing the line into a control leg and an injection leg. The injection leg terminating in an injection port, and a valve mechanism actuatable for selectively sealing the injection port, the valve mechanism controllable via a fluid pressure in the line, the fluid pressure communicated to the valve mechanism via the control leg for actuating the valve mechanism.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of an earlier filing date from U.S. Provisional Application Ser. No. 61/501,007 filed Jun. 24, 2011, the entire disclosure of which is incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    Chemical injection systems are used in the downhole drilling and completions industry. Check valves are included to prevent natural gas and other fluids from undesirably migrating up through the chemical injection lines. The performance of these check valves is not always adequate to prevent all fluid migration, particularly under static conditions (no chemical being injected) or while chemicals are being injected at lower rates. Faulty differential pressure devices for the check valves may also result in some chemical fluid undesirably flowing downhole under static conditions, which can create a vacuum in the injection line, causing vaporization of the chemical carrier and formation of precipitates that tend to clog the injection line. Problems with check valves may include debris caught in the valves, wear or degradation of the valves over time, problematic installations, etc. Accordingly, advances to prevent fluid migration and improve chemical injection are always well received by the industry. 
       BRIEF DESCRIPTION 
       [0003]    A downhole valve assembly, including a line operatively arranged to carry a fluid, a splitter arranged on the line, the splitter dividing the line into a control leg and an injection leg. The injection leg terminating in an injection port, and a valve mechanism actuatable for selectively sealing the injection port, the valve mechanism controllable via a fluid pressure in the line, the fluid pressure communicated to the valve mechanism via the control leg for actuating the valve mechanism. 
         [0004]    A method of injecting fluid downhole, including pumping a fluid in a line. The line including a splitter for dividing the line into a control leg and an injection leg, the injection leg terminating in an injection port; and selectively controlling a valve mechanism to open and close the injection port based on the fluid pressure of the fluid in the line, the fluid pressure communicatable to the valve mechanism via the control leg. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
           [0006]      FIG. 1  is schematic view of a shut-off assembly in an open position; 
           [0007]      FIG. 2  is a schematic view of the shut-off assembly of  FIG. 1  in a closed position; 
           [0008]      FIG. 3  is an enlarged view of the area encircled in  FIG. 2 ; 
           [0009]      FIG. 4  is a schematic view of an alternate embodiment shut-off assembly; 
           [0010]      FIG. 5  is a schematic view of another alternate embodiment shut-off assembly; 
           [0011]      FIG. 6  is a schematic view of a piston valve mechanism in an open position; and 
           [0012]      FIG. 7  is a schematic view of the valve mechanism of  FIG. 6  in a closed position. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
         [0014]    Referring now to  FIG. 1 , a downhole system  10  is shown. The system  10  includes a chemical injection assembly  12  for injecting chemical fluids into a production tube  14  located in a borehole. The production tube  14  is for directing natural gas or the like from formations downhole to a surface of the borehole where it can be harvested, collected, processed, etc. The injection assembly  12  includes a tube or line  16  that extends to the surface where the borehole is drilled, where chemicals, such as demulsifiers, clarifiers, corrosion inhibitors, scale inhibitors, dewaxers, surfactants, etc., can be pumped downhole into the production tubing  14  for assisting in the production process. 
         [0015]    The line  16  is split into an injection leg  18  and a control leg  20  at a splitter  22 . The injection leg  18  terminates at an injection port  24  into the production tubing  14 . A check valve  26  is located upstream of the injection port  24  for preventing the back flow of fluids, migration of gas, etc., up the line  16  to the surface. The check valve  26  may be accompanied by a differential pressure device  28 , e.g., a heavy-duty spring or other biasing feature, for creating a pressure differential across the check valve  26  in order to keep the valve  26  closed when chemical fluids are not being pumped down the line  16  from the surface with sufficient pressure. 
         [0016]    The check valve  26  and/or the differential pressure device  28  may leak or weep over time, such as from the buildup of debris, normal wear and tear, etc. As a result, a valve mechanism  30  is included in the injection assembly  12  of the downhole system  10  described herein. In this illustrated embodiment, the valve mechanism  30  includes a sleeve  32  slidably mounted within the production tubing  14 . The sleeve  32  includes seal elements  34 ,  36 , and  38  between the sleeve  32  and an inner surface of the production tubing  14  in order to seal the sleeve  32  to the tubing  14  as the sleeve  32  slides along the tubing  14 . 
         [0017]    The seal elements  34  and  36  define an isolation chamber  40 , while the seal elements  36  and  38  define a control chamber  42 , with both chambers  40  and  42  fluidly sealed from the tubing  14 . Although two chambers are formed utilizing three seals in the illustrated embodiment, it will be appreciated that a single chamber could be created using only two seal elements (e.g., removing seal element  36 ), or that a fourth seal element could be included to seal each of the two chambers with two separate elements, etc. 
         [0018]    The valve mechanism  30  for the assembly  12  is shown in its open position in  FIG. 1 . In the open position, the sleeve  32  is actuated away from injection port  24  such that the injection port  24  is in fluid communication with the production tubing  14 . In  FIG. 2 , however, the valve mechanism  30  of the assembly  12  is in its closed position, with the sleeve  32  actuated toward the injection port  24 , thereby positioning the injection port  24  in the chamber  40  sealed from the production tubing  14  by the seal elements  34  and  36 . In the closed position, the injection port  24  and the production tubing  14  are no longer in fluid communication with each other. Thus, the valve mechanism  30  enables selective control over whether the injection port  24  is open with respect to the production tubing  14 . For example, by closing the injection port  24  with the valve mechanism  30 , the migration of fluids from the production tubing  14  up the injection leg  18  and into the injection line  16  can be prevented because the injection port  24  is isolated in the chamber  40  from the production tubing  14 . Similarly, by closing the injection port  24  with the valve mechanism  30 , the chemical injection line  16  will not readily leak, and therefore be kept full for preventing the creation of a vacuum in the line  16 . 
         [0019]    In one embodiment, a spring  44  (or some other actuation device) is utilized to urge the valve mechanism  30  into its closed position by default, i.e., by preloading the spring  44  to exert at least a minimum force on the sleeve  32 , e.g., a force greater than the hydrostatic pressure of the chemical fluid in the line  16 . In order to transition the valve mechanism  30  from the closed position ( FIG. 2 ) into the open position ( FIG. 1 ), a pressure in the control leg  20  must overcome the actuation force by the spring  44  or other actuation device. As shown more clearly in  FIG. 3 , the sleeve  32  includes a profile  46  in the chamber  42  for enabling creation of a pressure differential across the sleeve  32 . That is, for example, by increasing the pressure in the chamber  42 , the increased surface area provided by the profile  46  results in a net force on the sleeve  32  for actuating the sleeve  32  away from the injection port  24  in order to open the injection port  24 , thereby enabling chemicals or the like to be injected into the production tubing  14 . It is to be appreciated that the parameters of the spring  44  and geometry of the sleeve  32  (e.g., surface area of the profile  46 ), can be set to predetermine a threshold pressure that overcomes the spring force. 
         [0020]    In summation, the pressure in the line  16  sets the pressure in the control leg  20 , the pressure in the control leg  20  sets the pressure in the chamber  42 , and the pressure in the chamber  42  is used to control the operation of the valve mechanism  30 . Accordingly, it is to be understood that it is the pressure in the line  16  that ultimately controls the operation of the valve mechanism  30 . Pressure will be increased in the line  16  when it is desired to pump fluid down the line  16 , and advantageously, it is the very act of pumping fluid down the line  16  that also actuates the valve mechanism  30  into its open position. Thus, the valve mechanism  30  is only open when fluid is being pumped down the line  16  at a sufficiently high pressure, and then closes by default due to the spring  44  once pumping has stopped and pressure in the line  16  drops. 
         [0021]    By pumping a chemical down the line  16  at a sufficient pressure, the chemical fluid will act on the profile  46  to force the sleeve  32  away from the injection port  24 , releasing the injection port from the sealed chamber  40 , and enabling fluid communication between the injection port  24  and the production tubing  14 . When fluid is being pumped downhole through the line  16  with sufficient pressure to open the mechanism  30 , this fluid is also at a sufficient rate to prevent the back flow or migration of fluids through the check valve  26 , up the leg  18 , up the line  16 , etc. Then, when the fluid is no longer being pumped downhole, the pressure is relieved and the mechanism  30  closes due to the biasing force of the spring  44 . Advantageously, the valve opens in response to the very act for which it is desired for the valve to be open, i.e., the act of pumping the fluid downhole, and the valve closes in response to the very act for which it is desired for the valve to be closed, i.e., pumping has stopped. As a result, separate control lines do not have to be run downhole, maintained, monitored, controlled, etc., the injection port  24  is closed by default to block the migration of fluids up the injection line  16  in static conditions, and the injection port  24  is opened reliably under active conditions when fluid needs to be injected into the production tubing  14 . 
         [0022]    The valve mechanism  30  takes the form of a sliding sleeve mechanism (i.e., it includes the sleeve  32 ) in the illustrated embodiments, but it will be appreciated that other devices could be used, such as a flapper valve, ball valve, shuttle valve, etc., in order to use the pressure in the line  16  (and the control leg  20 ) to selectively enable fluid communication between the injection port  24  and the production tubing  14 . 
         [0023]    It is also to be appreciated that the check valve  26  and pressure differential device  28  could play an important role even if the valve mechanism  30  prevents fluid migration up-hole. That is, the pressure differential device  28  could be set to ensure that the pressure required to open check valve  26  is greater than the pressure required to open the valve mechanism  30 . If the reverse were true, then there would be little control over the rate at which fluid is pumped, as the fluid would be pressurized at the injection port  24  and ready to rush out when the port  24  is opened. For example, assume a first pressure is required to actuate the valve mechanism  30  to its open position, and a second pressure is required to overcome the pressure differential device  28  to enable flow through the check valve  26 . In this example, the pressure in the line  16  can first be set to be equal to or greater than the first pressure, but less than the second pressure, at which point the valve mechanism  30  opens. Since the second pressure has not been reached, the fluid is pressurized at the check valve  26 , and is not yet injected into the production tubing  14 . Then, by further pressurizing to the second pressure and above, the differential device  28  can be overcome, and the flow of fluid can be more accurately controlled into the tubing  14 . Since the pressure in the injection line  16  will change when the valves  30  and/or  26  are opened, a pump controller and a flowmeter could be included fluidly coupled to the line  16 , for example at the surface of the borehole, for enabling more precise control of fluid rate regardless of changing pump resistance or fluid pressures. Under some conditions, a pressure differential device may not be required. For example, a pressure differential device will not be necessary if the pressure in the production tubing  14  is high enough that the pressure required to inject fluid into the production tubing  14  is greater than the pressure required to open the mechanism  30 . 
         [0024]    The system  10  is shown in  FIGS. 4 and 5  incorporating an assembly  12   a  and an assembly  12   b , respectively, in lieu of the assembly  12 . The assembly  12   a  incorporates a valve mechanism  30   a . The valve mechanism  30   a  includes a piston  48  actuatable by pressure supplied to a chamber  50  via the control leg  20 . The piston  48  includes a passage  52  therethrough for selectively connecting the portions of the injection leg  18  on opposite sides of the valve mechanism  30   a  when properly positioned. A spring  54  is included to bias the piston  48  into a closed position, wherein the passage  52  is misaligned with the injection leg  18  so that fluid can not pass to the injection port  24 . The mechanism  30   a  includes a plurality of seal elements  56  to seal the piston chamber  50 , the passage  52 , the injection leg  18 , etc. from each other. Thus, it is to be appreciated that even though some degree of fluid migration may occur up the portion of the injection leg  18  downstream of the valve mechanism  30   a , the valve mechanism  30   a  provides an alternate embodiment for selectively opening and closing the injection port  24  in order to selectively enable or disable fluid communication between the line  16  and the production tubing  14 . 
         [0025]    The assembly  12   b  includes a valve mechanism  30   b . The valve mechanism  30   b  resembles the mechanism  30   a  in that it includes a piston  58  actuatable by pressure in a chamber  60  supplied by the control leg  20 . Further, the mechanism  30   b  includes a passage  62  therethrough for selectively connecting the portions of the injection leg  18  on opposite sides of the valve mechanism  30   b  when the piston  58 , and therefore the passage  62 , is properly positioned. A spring  64  is similarly included to bias the piston  58  into a closed position, wherein the passage  62  is misaligned with the injection leg  18  so that fluid can not pass to the injection port  24 . The mechanism  30   b  also similarly includes a plurality of seal elements  66  to seal the piston chamber  60 , the passage  62 , the injection leg  18 , etc. from each other. The mechanism  30   b  differs from the mechanism  30   a  in that the mechanism  30   b  is positioned upstream from the injection valve  24 . Also from mechanism  30   b , it can be appreciated that the splitter  22  can be incorporated into a housing  68  for the valve mechanism  30   b  in order to save on the number of components that need to be manufactured or installed. 
         [0026]    The valve mechanism  30   b  is shown in more detail in  FIGS. 6 and 7 , actuated between a closed and an open position, respectively. Similar to the mechanism  30 , to open the injection port  24 , the line  16  is pressurized, e.g., by pumping fluid down the line  16 , and the fluid pressure is communicated to the valve mechanism via the control leg  20 . The increased pressure actuates the piston  58  to against the force of the spring  64  in order to align the passage  62  with the injection leg  18  for enabling fluid to pass from the line  16  through the valve mechanism  30   b  to the port  24  and into the production tubing  14 . In order to seal off the injection port  24  from the line  16 , the pressure in the line  16 , control leg  20 , and chamber  60  is lessened so that the spring urges the piston  58  to misalign the passage  62  and the portions of the injection leg  18 . When the passage  62  is misaligned, fluid can not flow through the mechanism  30   b , and therefore, can not flow between the line  16  and the port  24 . It is to be understood that the mechanism  30   a  operates in essentially the same way as described for the mechanism  30   b . Further, all three mechanisms  30 ,  30   a , and  30   b  operate in generally the same way, i.e., by pressuring the fluid injection line  16 . Moreover, the check valve  26  and the differential pressure device  28  can operate with either  30   a  or  30   b  as described above in order to more accurately inject chemicals or other fluids into the production tubing  14 . 
         [0027]    While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.