Abstract:
A downhole tool having a body, a transducer within the body, and an opening formed through a sidewall of the body. The opening provides a port through which the transducer can communicate from within the body. An elastomeric boot in the body covers the opening and is a barrier that prevents fluid ingress into the downhole tool. An expandable sleeve envelopes the elastomeric boot and provides support that limits bulging of the elastomeric boot from within the body through adjacent openings in the body. An example sleeve is made from elongated members woven into a tubular.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to and the benefit of co-pending U.S. Provisional Application Ser. No. 61/305,839, filed Feb. 18, 2010, the full disclosure of which is hereby incorporated by reference herein. 
     
    
     BACKGROUND 
       [0002]    1. Field of Invention 
         [0003]    The invention relates generally to the field of downhole acoustic measurement. More specifically, the present invention relates to a downhole tool having a rubber boot covered by an expandable sleeve. 
         [0004]    2. Description of Prior Art 
         [0005]      FIG. 1  illustrates a side partial sectional view of a downhole tool  10  deployed on wireline  14  within a wellbore  12 . The downhole tool  10  is used for interrogating a formation  16  adjacent the wellbore  12 , gathering information about the formation  16 , and either storing or transmitting the information via the wireline  14  to a surface truck  18  shown controlling the downhole tool  10 . In this prior art example, the downhole tool  10  includes an elongated body  20  for housing components within the downhole tool  10 . One example of a component shown is a transducer  22 ; which in this example is illustrated as an acoustic transmitter and emitting an acoustic signal from within an opening  26  formed through a side wall of the body  20 . The signal propagates into the formation  16 ; a portion of the acoustic signal reflects back towards the downhole tool  10 . A second transducer  24  is shown, also housed within the body  20 , and in this example is an acoustic receiver configured for receiving the acoustic signal reflecting from the formation  16 . A corresponding opening  28  is formed through the body  20  so the transducer  24  can receive the reflected signal. 
         [0006]    A portion of the logging tool  10  is shown in sectional view to illustrate boots  30 ,  32  within the tool that cover the openings  26 ,  28 . The hoots  30 ,  32  are typically made from an elastomeric material, such as rubber or another type of flexible polymer. Often, dielectric fluid, such as silicone, fills the inside of the body  20  for electrically insulating components within the body  20 . Because fluids in the wellbore  12  typically include conductive materials damaging to components within the body  20 ; the boots  30 ,  32  form a harrier for preventing wellbore fluid ingress into the body  20 . Also, as wellbore pressure overcomes dielectric fluid pressure, wellbore pressure through the openings  26 ,  28  causes the pliable boots  30 ,  32  to bow inward and impinge the dielectric fluid; thereby equalizing wellbore and dielectric fluid pressure. 
         [0007]      FIG. 2  illustrates a side partial sectional view of a portion of the downhole tool  10  of  FIG. 1 . In this view, the tool  10  is being raised from within the wellbore  12  after having been immersed in wellbore fluids. While immersed downhole, wellbore fluid constituents, such as lower molecular weight compounds, can migrate through the boots  30 ,  32  and become trapped within the boots  30 ,  32  in the body  20 . Raising the downhole tool  10  toward the surface reduces the hydrostatic pressure applied to the boots  30 ,  32  and dielectric fluid to allow lighter molecular weight fluids to expand or vaporize. As the trapped fluids expand and/or vaporize, the hoots  30 ,  32  can bow outward through the opening  26 ,  28  and into contact with the inner walls of the wellbore  12 . Contact against the wall of the wellbore  12  may damage the boots  30 ,  32 . Additionally, once removed from within the wellbore  12 , the trapped high pressure fluid within the boot  30 ,  32  must be vented so the tool  10  can be serviced. This can present added turnaround time and steps. 
       SUMMARY OF INVENTION 
       [0008]    Disclosed herein is a downhole tool insertable within a wellbore. In an example embodiment the downhole tool includes a housing, a space in the housing, and an opening that is formed through a sidewall of the housing. The tool further includes a barrier between the opening and the space a membrane. A series of elongate members are arranged on a side of the membrane that faces the opening. The members restrain the membrane from bulging through the space when pressure in the space exceeds pressure ambient to the housing. A transducer may be included within the housing, example transducers are acoustic transmitters, acoustic receivers, and those that can transmit and receive. In an example embodiment, the transducer acoustically communicates from within the housing and through the membrane and the series of elongate members. In an example embodiment, the barrier is formed from an elastomeric material and formed into a sleevelike configuration and wherein the elongate members define a sleeve that circumscribes the barrier. In an example embodiment, a mandrel is in the space and a coupling anchors the sleeve and barrier to the mandrel. In an example embodiment, the tool may further include a plurality of openings from through the sidewall of the housing, a barrier between each of the openings and the space, wherein each of barrier comprises a membrane, and a series of elongate members on the surface of each membrane facing the opening. In an example embodiment, at least some of the elongate members intersect some of the other elongate members to define a mesh. 
         [0009]    Also disclosed herein is a method of wellbore operations. In an example embodiment, the method includes providing a downhole tool made up of a housing with an inside space and an opening through a sidewall of the housing. A barrier is set between the inside space and the openings. The method includes shielding the barrier from direct contact with a borehole wall by applying a series of elongate members between the barrier and the opening. Thus when the tool is inserted into the wellbore the barrier is protected from contact. The barrier elongate members also prevent the barrier from ballooning outward by retaining the barrier within the housing when the pressure in the space exceeds pressure ambient to the housing. The downhole tool is deployed in the wellbore. In an example embodiment, the elongate members are arranged in a mesh-like configuration and intertwined to form a cohesive member. In an example embodiment, the barrier and the cohesive member are tubular members; the method can then further include clamping the barrier and cohesive member to a mandrel within the housing. In an example embodiment, the method further includes acoustically communicating from within the housing and through the barrier and elongate members. In an example embodiment, acoustically communicating includes actuating a transducer within the housing. In an example embodiment, the transducer can be an acoustic transmitter, an acoustic receiver, or can transmit and receive. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0010]    Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which: 
           [0011]      FIG. 1  is a partial side sectional view of a prior art downhole system. 
           [0012]      FIG. 2  is a partial side sectional view of a portion of the system of  FIG. 1 . 
           [0013]      FIG. 3  is a side sectional view of an embodiment of a downhole tool with an expandable sleeve. 
           [0014]      FIG. 4  is side perspective view of an example of an expandable sleeve. 
           [0015]      FIG. 5  is a side partial sectional view of a portion of the downhole tool of  FIG. 3 . 
       
    
    
       [0016]    While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION OF INVENTION 
       [0017]    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 through and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
         [0018]    It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. Accordingly, the invention is therefore to be limited only by the scope of the appended claims. 
         [0019]    Shown in a side partial sectional view in  FIG. 3  is an example of a downhole acoustic logging system in accordance with the present disclosure. More specifically shown is a downhole logging tool  50  inserted within a wellbore  52 . The downhole tool  50  includes an elongated body  54  shown deployed in the wellbore  52  on wireline  56 . A surface truck  57  is shown for raising and lowering the downhole tool  50  within the wellbore  52 , the surface truck  57  may also include data recording devices for recording data from within the wellbore  52 . The downhole tool  500   f    FIG. 3  also includes transducers  58 ,  60  housed within the body  54 . Shown adjacent each of the transducers  58 ,  60  are openings  64 ,  66  through the body  54  so that signals may communicate to and/or from the transducers  58 ,  60  to the outside of the downhole tool  50 . In the example of  FIG. 3 , the transducer  58  is an acoustic transmitter shown emitting an acoustic signal into the formation  62  surrounding the wellbore  52 . Also the transducer  60  illustrated is shown as a receiver for receiving acoustic signals reflected from or otherwise propagating through the formation  62 . 
         [0020]    Boots  68 ,  70  are shown housed within the body  54  and covering openings  64 ,  66 . The boots  68 ,  70  may be formed from any type of elastomer or other pliable material that may be used for sealing and transmitting or communicating pressure. In the embodiment of  FIG. 3 , expandable sleeves  72 ,  74  are shown included over the boots  68 ,  70 . In this example, the sleeves  72 ,  74  may extend past the ends of the boots  68 ,  70 . However, other arrangements are available wherein the sleeves  72 ,  74  cover a portion of the boot  68 ,  70 ; as well as configurations where multiple sleeves  72 ,  74  may be placed over a single boot  68 ,  70 . 
         [0021]    Shown in  FIG. 4  is a side perspective view of an example of an expandable sleeve  72 ,  74 . The sleeve  72 ,  74  of  FIG. 4  is made up of a series of elongated members  76 , where the members  76  may be a filament, a monofilament, or a braided line. The elongated members  76  of  FIG. 4  are illustrated as woven into a tubular-shaped configuration. The weave of the element  76  is such that axial forces applied to opposing ends of the sleeve  72 ,  74  can elongate the sleeve  72 ,  74  and reduce the radius of the sleeve  72 ,  74 . Similarly, applying a force on the inside wall of the sleeve  72 ,  74  and directed radially outward from its axis A X  can reduce the length of the sleeve  72 ,  74  while increasing the diameter of the sleeve  72 ,  74 . An example of material for the elongated member  76  is a polyetheretherketone (PEEK). The expandable sleeve  72 ,  74  may be obtained from Federal-Mogul Corporation, 26555 Northwestern Highway, South Field, Mich.  48033 , Ph: 248-354-7700. 
         [0022]    Shown in  FIG. 5  is an example of a portion of the downhole tool  50  of  FIG. 3  being raised from within the wellbore  52 . In this example, although lighter molecular weight fluids may have become trapped within the boot  68 ,  70 , the sleeve  72 ,  74  covering the boot  68 ,  70  limits outward radial movement of the boot  68 ,  70 , thereby maintaining a pressure within the body  54  of the downhole tool  50 . The increased pressure can accelerate the escape of the trapped fluids within the boot  68 ,  70  to permeate through the wall of the boot  68 ,  70  and to outside of the tool  50 . Because outward bulging of the boot  68 ,  70  may result in contact against the wall of the wellbore  52 ; the expandable sleeve  72 ,  74  can provide a protective layer between the boot  68 ,  70  and wall of the wellbore  52 . Also, by limiting the boot  68 ,  70  from outwardly bulging through an adjacent opening  64 ,  66 , the boot  68 ,  70  is less likely to grab or catch the wellbore wall, thus the expandable sleeve  72 ,  74  better facilitates removal of the tool  50  from within the wellbore. The sleeve  72 ,  74  may also protect the boot  68 ,  70  during maintenance, since high pressure water is often used for cleaning the downhole tool  50 . 
         [0023]    Referring back to  FIG. 5 , a clamp  78  is schematically illustrated for anchoring the expandable sleeve  72  and boot  68  within the downhole tool  50 . In the example of  FIG. 5 , the clamp  78  couples both the expandable sleeve  72  and boot  54  around a mandrel  80  in the downhole tool  68 ; wherein the mandrel  80  may also be used to secure the transducer  58 . The expandable sleeve  72  and boot  54  may be the same or different lengths, but both are shown having a length exceeding that of the opening  64 . 
         [0024]    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.