Abstract:
A tube wave reduction system for a borehole includes a tubular member; one or more openings in the tubular member, the one or more openings having a through-passage and a deformation region surrounding the through-passage; and an absorber in fluid communication with the one or more openings. Also included is a method for reducing an effect of a tube wave.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. Non Provisional application Ser. No. 13/209,065 filed Aug. 12, 2011, the entire disclosure of which is incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    In the drilling and completion arts, and indeed in all arts where flowing fluid is occasionally interrupted by a quickly closing valve, tube waves exist. Those of skill in arts associated with fluid flow are familiar with tube waves, known otherwise as “Stoneley waves” and in the vernacular as “water hammer”. These waves can range from low magnitude inconsequential forms to astoundingly high magnitude destructive forms characterized by hundreds to thousands of PSI pressure spikes. 
         [0003]    A number of factors influence the amplitude, frequency and duration of tube waves. Some important factors are velocity and specific gravity of the moving fluid as well as the rapidity with which the flowing fluid is subjected to change in rate of flow. Each of these will affect how energetic and therefore destructive the tube wave will be. In downhole arts, in both injection and production systems, tube waves can be very significant with respect to equipment and formation face damage and therefore are a concern for operators. The art, then, would be very receptive to systems and methods capable of reducing, dampening, alleviating or eliminating tube waves. 
       SUMMARY 
       [0004]    A tube wave reduction system for a borehole includes a tubular member; one or more openings in the tubular member, the one or more openings having a through-passage and a deformation region surrounding the through-passage; and an absorber in fluid communication with the one or more openings. 
         [0005]    A tube wave reduction system includes a tubular member; and one or more openings in the tubular member, the openings having a through-passage and a deformation region about the through-passage. 
         [0006]    A method for reducing an effect of a tube wave includes burping at least pressure from a tube wave through one or more openings in a tubular member through which the tube wave propagates; and absorbing energy from the tube wave thereby reducing a magnitude of the tube wave. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Referring now to the drawings wherein like elements are numbered alike in the several Figures: 
           [0008]      FIG. 1  is a schematic view of a tube wave reducing system; 
           [0009]      FIG. 2  is a schematic view of an alternate tube wave reducing system; 
           [0010]      FIG. 3  is a schematic view of another alternate tube wave reducing system; 
           [0011]      FIG. 4  is a schematic view of another alternate tube wave reducing system; 
           [0012]      FIG. 5  is a representative cross section of the one or more openings as disclosed herein; 
           [0013]      FIG. 6  is an alternate representative cross section of the one or more openings as disclosed herein; 
           [0014]      FIG. 7  is another alternate representative cross section of the one or more openings as disclosed herein; 
           [0015]      FIG. 8  is another alternate representative cross section of the one or more openings as disclosed herein 
           [0016]      FIG. 9  is a schematic view of another alternate tube wave reducing system; and 
           [0017]      FIG. 10  is a schematic representation of three openings configured to burp as disclosed herein. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    Referring to  FIG. 1 , a system  10  is illustrated that will reduce, mitigate, dampen, alleviate or eliminate tube waves by absorption. The mechanisms of absorption predominantly used in the following embodiments are friction and work. The system  10  comprises a section of tubular member  12  having an axial flow channel  14  defined by the tubular member  12  and one or more openings  16  whose axes are oriented to intersect the channel  14 . The member may be a housing of its own or other stub member or may simply be a modified joint of tubing string. In one embodiment the openings will be radially oriented and in others the openings may be angularly oriented relative to the channel  14  or where more than one opening is used, combinations of radial and angular (both illustrated in  FIG. 1 ) relative to the axial flow channel  14  may be used. The one or more openings  16  may be rounded (circular, oval, etc.) in cross section or may be slots (rectangular, square, etc.) in cross section or may be in any other geometric form for their cross sections. It is to be appreciated that the openings may be in a regular pattern, an irregular pattern, may be all of the same dimensions or may be of different dimensions from each other. Any combination of these attributes is also contemplated. Differing sizes of openings and different spacings of openings can be advantageous with respect to creating destructive interference in waveforms that are propagated through the openings. 
         [0019]    In each embodiment, the openings  16  will lead from the channel  14  to an energy absorber  18 . In the embodiment of  FIG. 1 , the energy absorber may be changeable in volume while in  FIG. 2 , the absorber is a high-friction flow-through material such as an open cell foam. By absorbing and dissipating the energy of the tube wave, the wave itself is reduced to a level where significant damage is not likely to occur to at least the component or formation portion that it is desired to protect. In some cases the wave can be completely eliminated. It will be appreciated however that complete elimination is not critical but rather that mitigation of the wave to a level where components of the downhole system and/or the formation itself would not be damaged is all that is needed for a fully successful endeavor to be realized. 
         [0020]    Still referring to  FIG. 1 , one embodiment employs a configuration where the absorber is configured as a chamber  20  in fluid connection with the one or more openings  16 . The chamber can change its volume in response to a change in pressure thereby enabling the chamber to absorb the pressure spike of a tube wave. Reduction of the energy of the tube wave is the result. 
         [0021]    The chamber  20  is defined by a flexible material  22  connected to the tubular member  12  that may be a monomeric or polymeric material or may be another type of material such as metal providing that it has flexibility sufficient to allow the chamber it defines to expand in volume. In the case of a metal, one embodiment would be a metal bellows  22   a  (see  FIG. 2 ) type configuration so that a change in internal volume of the chamber  20  is possible. 
         [0022]    The material  22  may be elastic or inelastic. Elastic materials will absorb the pressure spike through elastic deformation as well as through friction and destructive wave reflection interference. Where the material is not elastic it must be loose enough to generally gather about the one or more openings  16  such that it is able to change volume as noted above. In the case of the material being inelastic or substantially inelastic, the pressure spike inherent in the tube wave will simply be absorbed through the work necessary to produce movement of the inelastic material  22  itself. Without an elastic property or in cases where an elastic property exists but the change in volume of the chamber defined by the material is less than that required to elastically deform the material, the energy of the tube wave effectively dies in the friction presented by the flow of fluid into the chamber and the work required to inflate the chamber  20 . 
         [0023]    In some embodiments configured generally as illustrated in  FIG. 1  or  2 , the material and chamber defined thereby function alone to reduce the tube wave but in other embodiments, one or more obstructions  24  such as baffles, etc. (also illustrated in  FIGS. 1 and 2 ) can be added in the chamber area to cause fluid to travel in a tortuous path thereby causing it to lose more energy. The obstructions may be a part of the material  22  or attached to an outside of the member  12  within the area bounded by the material  22  or both. In each case, the propagating wave front from the tube wave will encounter these obstructions  24  experiencing friction and in some instances reflect a part of the waveform causing destructive wave interference. 
         [0024]    For each of the embodiments disclosed herein an option is to include within the downhole system an isolation device such as an isolation packer or seal  26  within the annulus  28  toward which the pressure is propagated through the one or more openings  16 . The placement of the isolation packer or seal  26  would be within the annulus between the component or formation the operator wants to protect from the pressure spike and the location of the one or more openings  16 . It is also contemplated that two packers or seals  26  might be employed in the annulus  28 , one uphole and one downhole of the one or more openings  16 . It is noted that the greater the distance between packers  26  in a two packer system, the larger the pressure spike that can be absorbed. Hence, packers should be placed as far as is convenient from the openings  16  in some embodiments while still being between those openings  16  and the feature that is to be the subject of protection. 
         [0025]    Referring to  FIG. 3 , the absorber  18  is configured as high-friction flow-through material  30  such as an open cell foam. The absorber is positioned against the tubular member  12  as illustrated. In this embodiment, the axial flow fluid is not physically separated from the annulus but rather is allowed to move into the annulus through the absorber  18 . The friction of the fluid moving through the absorber effectively dissipates the energy of the pressure spike of the tube wave. In another related embodiment, the material  30  is placed within a material  22  (see  FIG. 4 ) to provide for even more energy absorption and additionally physical fluid segregation. 
         [0026]    Referring to  FIGS. 5-8 , exemplary geometries of the one or more openings  16  are illustrated.  FIG. 5  illustrates a circular geometry;  FIG. 6  an oval geometry;  FIG. 7  a rectangular geometry; and  FIG. 8  a tapering rectangular geometry. It is stressed that these are merely examples. Further it is noted that other shapes may include lead in angles like that illustrated in  FIG. 8  such as a frustoconical lead in if the cross sectional geometry is circular. Referring to  FIG. 8 , the lead in is identified as numeral  32 , which extends from a larger side  34  of the opening  16  to a smaller other side  36  of the opening  16 , which in this case is substantially a slit  36 . Lead in embodiments may help encourage fluid movement out of the tubular  12 . 
         [0027]    Configured slightly differently, the lead in embodiments create a thinner wall thickness of the tubular  12  allowing the system to “burp”. “Burp” and formatives thereof in this disclosure refer to a pressure buildup on one side of a structure that is configured to deform under that enhanced pressure and release the pressure build up. The opening size returns to a low pressure configuration after pressure has begun to equalize. This is better described in connection with  FIG. 10  hereunder. It is further to be understood that the burping concept can function on its own, venting to the annulus  28 , or can vent to a microannulus or can vent to a chamber like the chambers identified as  20  above. 
         [0028]    Referring to  FIG. 9 , a microannulus  40  can be created by attaching a tubular  42  to the OD of the tubular  12  leaving the microannulus  40  between the tubular member  12  and the additional tubular  42 . In each of these configurations the concept itself remains a “burp” concept wherein the tubular member  12  is supplied with one or more openings  116  (see  FIG. 10 ) that themselves are configured to maintain a relatively small through-passage at ambient pressures and change to a larger through-passage when a pressure spike is encountered such as when a tube wave arrives at the location of the tubular member  12 . Upon encountering the higher pressure, the one or more openings will deform for the duration of time that the pressure differential thereacross is high. The “burp” will be at least fluid pressure and generally will include fluid into the annulus or microannulus or chamber. 
         [0029]    Referring to  FIG. 10 , a schematic representation of the burping openings is provided. It is to be understood that merely three of the openings are illustrated. More or fewer are contemplated in any desired pattern as desired. The openings  116  comprise through-passages  118  that may be created via laser cutting, plasma cutting, traditional or electric discharge machining, etc. and are relatively small so that fluid at ambient pressure is not significantly exhausted through those passages. At elevated pressure however, as is experienced in the inside of the tubular  12  during a tube wave event, the openings  116  deform slightly to produce a larger through-passage  118  to “burp” fluid or at least pressure therethrough. Enabling the deformation capability is a deformation region  120  (which may or may not appear like the lead in area  32  of  FIG. 8 ) about the through passages  118  that exhibits a sufficient resilience to allow the deformation. In one embodiment the region  120  comprises an area of thinner material of the tubular  12 . This is accomplished in some embodiments by gradually thinning the material of the tubular member  12  as proximity to the through passage  118  increases. In other embodiments the material of tubular  12  might be modified in the regions  120  by changing the material entirely such as by substituting all or part of the thickness of the tubular member  12  in regions  120  with a different material such as rubber or the like. Such material will be selected to have greater flexibility than the material of tubular  12  and sufficient flexibility to enable the burping action desired for function of this embodiment. 
         [0030]    Each of the embodiments described in this disclosure are described as singular entities but it is to be appreciated that systems can comprise multiple iterations of the described entities. Further, in systems where multiple entities are used, they can each be of the same type or they can be different types of the above described embodiments. 
         [0031]    It is to be appreciated that configurations in accordance with the teaching herein offer no restriction to normal axial flow through the tubular member  12  nor any impediment to running of tools therethrough, each of which is advantageous to a downhole drilling and completions operator. 
         [0032]    While one or more embodiments have been shown and described, modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.