Patent Publication Number: US-7708074-B2

Title: Downhole valve for preventing zonal cross-flow

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention generally relates to the field of subterranean well completions and controlling flow of production fluid from wells comprising primary and lateral wells. 
   2. Description of the Related Art 
   In many instances, a hydrocarbon producing wellbore includes not only the primary well drilled into a subterranean formation, but also one or more lateral wells extending into the surrounding formation adjacent the primary wellbore.  FIG. 1  provides a cross sectional view of an example of a wellbore production system  10  installed in a wellbore having lateral wells. In this example, the primary wellbore  5  extends from the surface and into a producing zone within a subterranean formation  6 . The associated casing  7  cemented within the wellbore  5  extends substantially along the entire length of the wellbore and also into the formation  6 . Perforations  11  formed through the side of the wellbore  5  and through the casing  7  into the surrounding formation  6  provide fluid pathways for production fluid (hydrocarbon gas and liquid) to flow into the wellbore  5 . The wellbore production system  10  includes completion tubing  13  coaxially inserted within the casing  5 . The completion tubing  13  extends along the length of the wellbore  5  up to the wellhead  14  and delivers the production fluid therein to the wellhead for distribution to a production line  16 . 
   In addition to the production fluid from the subterranean formation  6 , the lateral wellbores ( 3 ,  4 ) extend into corresponding production zones within corresponding subterranean formations ( 8 ,  9 ). These lateral wellbores ( 3 ,  4 ) also include perforations  11  providing fluid communication between the wellbore and their associated formation. In the embodiment of  FIG. 1 , the produced fluids from the primary wellbore  5  and the lateral wellbores ( 3 ,  4 ) are deposited into a single completion tubing  13  where these fluids are mixed. It should be pointed out that other configurations exist wherein dedicated tubing is provided to each production zone thereby preventing commingling of fluids within the wellbore  5 . One disadvantage of installing dedicated tubing is the presence of additional hardware within the wellbore as well as the difficulty of introducing and maintaining the hardware in these individual circuits. 
   The producing zones ( 6 ,  8 ,  9 ) may operate or produce at varying pressures. To prevent an imbalanced pressure situation within the completion tubing  13 , chokes ( 18 ,  20 ,  22 ) are provided in the fluid flow pathway between the respective producing zones and the completion tubing  13 . Chokes provide a regulating effect on the fluid by adjusting the flow rate and pressure to compensate for pressure differences between these different producing zones. Also shown in  FIG. 1  are packer seals  26  proximate to the junctions between the primary wellbore  5  and the laterals that seal the flow pathway between the annulus between the tubing  13  and casing  5  and forces fluid flow through perforations  24  in the tubing string  13  and through the respective chokes ( 18 ,  20 ,  22 ). 
   While existing chokes, or other flow control mechanisms regulate or adjust fluid flow and fluid pressure, these devices do not limit flow direction therethrough. Accordingly, in situations wherein pressure within the production tubing  13  may exceed pressure within a particular lateral wellbore or its associated producing zone, the fluid in the higher pressure tubing string may migrate into the production zone through any one of these known devices. This situation could occur if a flow regular of a high pressure producing zone fails or if the well is suddenly shut in and the respective valves are not closed prior to the shut in. Because migration of producing fluids from one zone into another zone having a different pressure may cause deleterious effects on the lower pressure formation, this is an undesired situation. Therefore, it would be advantageous to develop a device for preventing the cross flow of production fluids from producing zones having different pressures. It would also be advantageous to develop and implement a device that can regulate flow in addition to preventing cross flow of production fluids. 
   SUMMARY OF THE INVENTION 
   The device disclosed herein is a downhole control valve for use in a tubing completion string disposed in a wellbore. In one embodiment the control valve comprises a housing defining a plenum therein, a tubular member extending into the plenum and having a first end in the plenum. Also included is an aperture on a portion of the tubular member within the plenum, wherein the aperture is formed through the side of the tubular member and a plug assembly. The plug assembly includes a disk having a shaft extending therefrom wherein the shaft is coaxially disposed within the first end of the tubular member, and wherein the plug assembly is reciprocatingly slideable within the tubular member in response to a pressure differential on the disk. The tubular member is in pressure communication with a corresponding downhole producing zone. 
   In one mode of operation of the control valve, the plug assembly is slideable into a first position urging the shaft adjacent the aperture thereby blocking fluid flow through the aperture. In another operational mode of the control valve, the plug assembly is slideable into a second position urging the shaft away from the aperture thereby allowing fluid flow through the aperture. 
   Optionally, a lip may be formed on an end of the housing, wherein the lip radially extends inward towards the housing axis and the lip retains the plug assembly within the plenum. A first perforation may be formed on the disk and a corresponding second perforation formed on the lip, wherein the first and second perforations are substantially aligned thereby providing a flow path from the plenum to the outside of the housing through the perforations. Additional apertures may be formed on the tubular member. 
   The present disclosure also includes a completion system disposed within a subterranean wellbore having more than one producing zone. The completion system comprises a tubing string and a control valve. The control valve comprises, a housing, a plenum within the housing, a tubular member extending into the plenum, an aperture formed through the member wall on a portion of the member within the plenum, and a plug coaxially disposed in the end of the tubular member within the plenum in sliding response to pressure differences between a corresponding producing zone and pressure in the tubing string. 
   The plug is configured to slidingly respond to a closed position when the pressure in the tubing string exceeds the corresponding producing zone pressure. The plug is also configured to slidingly move to an open position when the first producing zone pressure exceeds the pressure in the tubing string thereby allowing fluid flow from the first producing zone into the tubing string. The control valve also regulates fluid flow into the production string. The completion system may comprise a second control valve 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     So that the manner in which the features, advantages and objects of the invention, as well as others which will become apparent, may be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiment thereof which is illustrated in the appended drawings, which form a part of this specification. It is to be noted, however, that the drawings illustrate only a preferred embodiment of the invention and is therefore not to be considered limiting of the invention&#39;s scope as it may admit to other equally effective embodiments. 
       FIG. 1  shows a prior art well production system. 
       FIG. 2  shows in side partial cross sectional view an example of a control valve. 
       FIGS. 3   a - 3   e  show side and frontal views of components of a control valve. 
       FIGS. 4   a - 4   d  show operational modes of a control valve in accordance with the disclosure. 
   

   DETAIL DESCRIPTION 
   The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
   The device and system described herein is useful for preventing cross flow or migration of production fluids between different producing zones. In one embodiment the device comprises a control valve disposed in the flow path between a subterranean zone producing a hydrocarbon fluid and a tubing completion string. The device is configured to allow flow from its corresponding producing zone into the completion string, but to prevent migration flow from fluid within the completion string into the corresponding producing zone. If the completion string pressure exceeds the pressure of a producing zone, it is likely due to another producing zone communicating with the completion string is at a pressure higher than the first producing zone. Therefore, the control valve and device disclosed herein provides a zonal isolation function between different producing zones of the same wellbore circuit. 
   With reference now to  FIG. 2 , one embodiment of a control valve  30  in accordance with the present disclosure is shown in a side partial cross sectional view. The control valve  30  comprises a generally hollow housing  32  forming a plenum  33  therein. The housing  32  is closed on its rear wall  37  and generally open on the opposite end. A tubular member  44  is shown extending into the plenum  33  through the rear wall  37 . Apertures  46  are formed through the wall of the tubular member  44  thereby communicating the inner confines of the tubular member  44  to the plenum  33 . The first end of the tubular member  44  terminates within the plenum  33  wherein the second end (not shown) of the member  44  is in fluid communication with a corresponding production zone of a subterranean formation. 
   Slidingly disposed within the open first end of the tubular member  44  is a plug assembly  39 . The plug assembly  39 , also shown in cross sectional view in  FIG. 2   a , comprises a disk  38  with a shaft  42  extending from one side of the disk  38 . Perforations  40  are formed through the disk  38  that are substantially parallel to the disk axis. A lip  34  is formed on the open end of the housing  32 . Perforations  36  are formed through the lip that are substantially parallel with the axis  35  of the control valve  30 . In the embodiment of  FIG. 2 , it is shown that the perforations  40  of the disk  38  are in substantial alignment with the perforations  36 . 
     FIGS. 3   a - 3   c  illustrate a side view of the tubular member  44  and side and front views of plug assembly  39  components. With reference now to  FIG. 3   a , a portion of the tubular member  44  is shown in a side view illustrating perforations  46  formed through the wall of the tubular member  44 . In  FIG. 3   b , a side view of the shaft  42  is shown; as discussed above, the shaft is formed to coaxially slide within the annular confines of tubular member  44 . In one embodiment, the shaft  42  may be a Boston shaft obtainable from Boston Gear at 14 Hayward Street, Quincy, Mass. 02171, phone 617-328-3300.  FIG. 3   c  illustrates the frontal view of the disk  38  having perforations  40  formed therethrough at substantially the same radial distance from the center of the disk  38 .  FIG. 3   d  is a rear view of the rear wall  37  illustrating an embodiment where the control valve  32  has a substantially cylindrical configuration.  FIG. 3   e  is a perspective view of a cutaway portion of the control valve  32 . In this embodiment, the lip  34  is shown having perforations  36  formed at roughly the same radial distance from the center of the lip  34 . 
   As noted above, the control valve  30  described herein is primarily for use within a tubing completion string, such as that illustrated in  FIG. 1 . Accordingly, the scope of the present disclosure includes completion strings having multiple control valves. In one embodiment, a control valve as described herein is included with the completion string and disposed in the flow path between producing zones and the completion string. The tubular member  44  of each control valve  30  thus is in fluid and pressure communication with its corresponding producing zone and the disk outer surface is in pressure communication with the completion string. Thus, pressure differences or gradients between the corresponding producing zone and the completion string pressure exerted on the disk outer surface dictates the position of the plug assembly  39 . 
     FIGS. 4   a - 4   d  illustrate an operational sequence of an embodiment of the control valve of the present disclosure.  FIG. 4   a  provides a partial cross sectional view of the control valve  30  wherein the position of the plug assembly  39  is fully inserted within the tubular member  44 . This configuration, also referred to herein as a first or a closed position, has the disk  38  substantially flush with the terminal end of the tubular member within the plenum  33 . In the closed position the shaft  42  extends into the tubular member  44  residing adjacent each of the apertures  46 . Thus, the closed or first position of the control valve  30  blocks fluid and pressure communication between the inner confines of the tubular member and the plenum  33 . When in the closed position, the pressure within the associated completion tubing string exceeds the pressure within the tubular member  44  and thus also exceeds the pressure within the corresponding producing zone in communication with the tubular member  44 . 
     FIGS. 4   b - 4   d  illustrate the condition when the pressure in the tubular member  44  (and thus its corresponding producing zone) exceeds the completion string pressure thereby slidingly urging the disk  38  away from the tubular member  44 . With reference now to  FIG. 4   b , the plug assembly  39  is moving from its position in  FIG. 4   a  away from the terminal end of the tubular member  44  towards the lip  34 . Additionally the shaft  42  has moved away from a first row of perforations  46  thereby initiating pressure and fluid communication between the inner confines of the tubular member  44  and the plenum  33 .  FIG. 4   c  illustrates further movement of the plug assembly  39  within the plenum  33  towards the lip  34 . Ultimately, as shown in  FIG. 4   d , the increased pressure of the corresponding producing zone over that of the inside of the completion string fully urges the plug assembly  39  into substantial mating contact with the lip  34 . In this configuration, it can be seen that the perforations  40  are substantially aligned with perforations  36 . Thus in the open, or second position illustrated in  FIG. 4   d , full fluid and pressure communication would exist between the plenum  33  and the inner portion of a production/completion tubing string.  FIGS. 4   b  and  4   c  represent intermediate positions of the plug assembly between the open and closed positions. As illustrated and described herein the control valve  30  is a passive device responsive to pressure differentials across the opposing surfaces of the disk  38  and may reciprocate between the open and closed positions by the sliding action described above. 
   In normal operation while in the producing mode of the hydrocarbon bearing formation and associated wellbore, the apertures  46  combined with flow through the plenum and perforations ( 40 ,  36 ) provide a regulating pressure drop. It may be necessary to regulate the fluid flow when a wellbore production circuit comprises multiple lateral producing bores in addition to the primary wellbore. The regulating ability of the control valve  30 , when disposed in relation to each producing wellbore of the well system, can regulate pressure within the completion tubing without hindering production of other lateral wellbores. 
   The present device also has benefits in situations where production of the well is ceased for a period of time. In some instances well having multiple lateral wellbores may be shut in allowed to “settle out”. Settling out occurs by communicating all interconnected producing zones through the completion string without regulating or reducing pressure between the producing zone and the completion string. This exposes the lower pressure producing zones to the highest pressure producing zone; and if unchecked, enables high pressure zone production fluid to migrates into lower pressure zones. Implementation of the control valve disclosed herein reacts to such pressure differentials by pushing the plug assembly into the closed or first position as shown in  FIG. 4   a . The control valve  30  in the closed position blocks high pressure fluid from migrating into its corresponding producing zone. Accordingly, the passive system herein described has great advantages over present known systems that may require a manual valve closure prior to a shut in. Moreover, manual closure is not always possible since some shut in conditions occur with little or no warning. 
   The present invention described herein, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the invention has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the present invention disclosed herein and the scope of the appended claims.