Patent Publication Number: US-8967276-B2

Title: Non-ballistic tubular perforating system and method

Description:
BACKGROUND 
     Opening perforations through walls of a tubular to allow fluid flow therethrough after deployment of the tubular within a structure is not uncommon. One method of opening such perforations is through ignition of ballistic devices, referred to as guns. Due to the explosive nature of the guns shipment of them through some jurisdictions is not permitted. The art is, therefore, always receptive to alternate methods of opening perforations in tubulars that do not require guns. 
     BRIEF DESCRIPTION 
     Disclosed herein is a non-ballistic tubular perforating system. The system includes, a tubular having a wall with perforations therethrough, and plugs positioned within the perforations that are configured to dissolve in response to exposure to a first environment thereby creative of a second environment that can dissolve or increase porosity of cement. 
     Further disclosed herein is a method of opening perforations in a tubular system. The method includes, positioning a tubular having degradable plugs plugging perforations therein within a borehole, cementing an annular space between the tubular and the borehole with cement, exposing the degradable plugs to a first environment that dissolves the degradable plugs, dissolving the degradable plugs, exposing the cement radially of the perforations to a second environment that dissolves or increases porosity of the cement, and opening an inside of the tubular to fluid communication with the borehole through the perforations and openings or porous channels dissolved in the cement. 
     Further disclosed herein is a non-ballistic tubular perforating system. The system includes a tubular having a wall with perforations therethrough, plugs positioned within the perforations configured to dissolve in response to exposure to a first environment, and bristles oriented radially of the tubular proximate the perforations configured to be degradably removed to leave radial channels through cement surrounding the tubular. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
         FIG. 1  depicts a partial side cross sectional view of a non-ballistic tubular perforating system disclosed herein in a plugged condition; 
         FIG. 2  depicts a partial side cross sectional view of the non-ballistic tubular perforating system of  FIG. 1  in an unplugged and an open perforated condition; 
         FIG. 3  depicts a partial side cross sectional view of an alternate embodiment of a non-ballistic tubular perforating system disclosed herein in a plugged condition; and 
         FIG. 4  depicts end cross sectional view of the non-ballistic tubular perforating system of  FIG. 3  taken at arrows  4 - 4 . 
     
    
    
     DETAILED DESCRIPTION 
     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. 
     Referring to  FIG. 1 , an embodiment of a non-ballistic tubular perforating system disclosed herein is illustrated at  10 . The system  10  includes, a tubular  14  having a wall  18  with perforations  22  therethrough. Plugs  26  are positioned within the perforations  22  thereby preventing fluid from flowing therethrough. The plugs  26  are made of a material that is dissolvable in a selected environment as will be elaborated on below. Cement  30  is positionable radially of the tubular  14  in an annular space defined between the tubular  14  and a borehole  34 , defining a wellbore in this embodiment, in an earth formation  38 . The cement  30 , at least in an area  42  positioned radially of the perforations  22 , is dissolvable or becomes porous or its porosity increases when exposed to a selected environment. 
     Referring to  FIG. 2 , after dissolution of the plugs  26  and the dissolution or increase in porosity of the cement  30  positioned radially of the perforations  22  an inside  44  of the tubular  14  is in fluidic communication with walls  46  of the borehole  34  through the perforations  22  and openings or porous channels  50  in the cement  30 . This configuration would allow for treatment of the earth formation  38 , for example, by pumping treatment fluid down through the inside  44  of the tubular  14  out through the perforations  22  and openings or porous channels  50  and into the formation  38 . Such treatments include fracturing, pumping proppant and acid treating, for example. Additionally, the system  10  would allow for production of fluids, such as hydrocarbons, for example, from the formation  38 . 
     The plugs  26  can be made of a degradable material such as a high strength controlled electrolytic metallic material that is degradable in brine, acid, or an aqueous fluid. For example, a variety of suitable materials and their methods of manufacture are described in U.S. Patent Application Publication No. 2011/0135953 (Xu et al.), the Patent Application Publication of which is hereby incorporated by reference in its entirety. The invention is not limited to this material, however, and the plugs  26  can be made of other degradable or dissolvable materials. For example, the plugs  26  can be made of calcium carbonate or a material containing amounts of calcium carbonate sufficient to cause the plugs  26  to dissolve when exposed to a solution that causes calcium carbonate to dissolve. 
     Optionally, the cement  30  can also be made of materials that contribute to dissolution thereof when exposed to a second environment. Such materials can include the materials employed in the plugs  26  described above, for example, if the cement  30  is made more highly degradable it could be made so only in the area  42 . In so doing, the operator can provide further control to an amount of the cement  30  that is dissolvable or porous or increases its porosity when exposed to a particular environment, thereby better controlling what portion of the cement  30  remains and provides structural support to the walls  46  of the borehole  34 . 
     Regardless of whether all, none or just the area  42  of the cement  30  is made of more readily degradable material or material with adjustable porosity dissolution of the cement  30  can still take place. Dissolution or increasing porosity of the cement can take place in a second environment created, at least in part, from byproducts of dissolution of the plugs  26 . This second environment can also include fluid employed to form a first environment dissolvable of the plugs  26 . 
     Additional control as to what portion of the cement  30  is dissolved or had an increase in porosity thereof can be accomplished through timing of exposure of the cement  30  to the dissolving environment. This can be done in at least a couple of different ways. One way is to only expose the cement  30  to the second environment through the perforations  22 . This method assures that the cement  30  adjacent to the perforations  22  is exposed first and consequently the longest of all the cement  30 . 
     Still further control of degradation of the cement  30  can be accomplished through dimensional parameters. This control is based on the ability of select materials to have a rate of depth of dissolution that is proportional, perhaps linearly, with time. Under such a scenario by making a radial dimension  54  between the tubular  14  and borehole  34  in the area  42  less than half a dimension  58  between adjacent perforations  22  the openings or porous channels  50  (defined by dissolution of the cement  30 ) will extend first from the tubular  14  to the walls  46  before they extend to open the space between adjacent openings or porous channels  50 . This may be desirable since it could leave some of the cement  30  structurally engaged between the walls  46  and the tubular  14  in the area  42 . 
     Another embodiment could employ a second environment that is configured to dissolve the cement  30  at different rates in different directions. For example, by dissolving the cement  30  faster in radial directions than in directions orthogonal to radial, the cement  30  will form openings or porous channels  50  that are longer than they are across. 
     Referring to  FIGS. 3 and 4  an alternate embodiment of a non-ballistic tubular perforating system disclosed herein is illustrated at  110 . The system  110  differs from the system  10  in a way that the cement  30  in the area  42  is made porous. Degradablebristles  112  are positioned to extend radially outwardly of the tubular  14  in the area  42 . The bristles  112  may be attached to a belt  116  that can be secured around the tubular  14  to simplify attachment of the bristles  112  to the tubular  14 . The bristles  112  are flexible to allow them to bend without breaking while contacting the walls  46  of the borehole  34  while being run therethrough. The bristles  112  are made sufficiently resilient to orient themselves radially (as shown in the Figures) after cement  120  has filled the annular space between the tubular  14  and the walls  46 . Since in this embodiment the bristles  112  are made of a degradable material, the cement  120  need not be. The bristles  112  can be made of a polymer, for example, that is degradable or meltable at temperature below those required to have detrimental effects on the rest of the components that make up the non-ballistic tubular perforating system  110 . Once the degradable bristles  112  are degraded and essentially removed they leave voids in the cement  120  where the bristles  112  had been. These voids provide fluidic communication between the perforations  22  and the formation  38 . 
     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.