Abstract:
A plug disposable in a well bore to block fluid from passing through the wellbore. The plug includes a body formed from water soluble glass. The body dissolvable in water. A method of utilizing water soluble glass is included.

Description:
BACKGROUND 
       [0001]    While drilling and producing wells for the recovery of petroleum and other subsurface deposits, it is often necessary to close off or plug a tubular conduit, such as a string of tubing extending from the well surface to a subterranean location, at a chosen point along the length of the conduit. Subsequently, it is necessary to be able to re-open the conduit for flow therethrough. A plug used to close off the tubing during setting of a well tool, such as a packer, may then be released so that fluid may be circulated through the tubing. 
         [0002]    Certain types of plugs are designed to be permanently installed, and they must be drilled or milled to be removed, which can be labor intensive. Other types of plugs are designed to be retrieved when the purpose for which the plug has been installed has been accomplished. Retrievable plugs generally employ some form of releasable anchoring device by which the plug may be secured to the internal bore of the well pipe and which may then be released to enable the plug to be withdrawn. One disadvantage of this prior art arrangement is that a restriction in the internal diameter of the tubing string often accompanies the design. Also, the prior art plugs were often retrieved on a wireline and the retrieval operation was complicated in the case of deviated well bores. Debris that sometimes accumulates on the top of the retrievable plug can also cause issues in the wellbore. 
         [0003]    Another prior art plug design involves the incorporation of a plug of expendable material and an actuating device used to dislocate or fracture the plug upon receipt of a triggering signal. The potential for remaining and problematic debris from the plug in the tubing string or wellbore must be carefully monitored in such devices. Sand plugs, for instance, have been provided for zonal isolation within wellbores, however the integrity of such sand plugs can be inconsistent and remaining particulates must be dealt with. 
       BRIEF DESCRIPTION 
       [0004]    A plug disposable in a well bore to block fluid from passing through the wellbore, the plug includes a body formed from water soluble glass, the body dissolvable in water. 
         [0005]    An apparatus which controls flow of well bore fluids from a production zone located within a subterranean formation adjacent the well bore to a well surface, the apparatus includes a tubular housing extending from the well surface to a selected depth within the well bore, the tubular housing having an internal bore for passage of fluids; and, a plug including a body formed from water soluble glass, the body dissolvable in water, the plug positioned within the tubular housing to initially close off the internal bore of the housing. 
         [0006]    A method of utilizing water soluble glass in a downhole fluid conducting system, the method includes employing an element formed of water soluble glass; performing a first function in the system when the element is present; dissolving the element in the presence of water; and performing a second function in the system different than the first function. 
         [0007]    A system which detects presence of formation water in an underground location, the system includes a casing insertable within a wellbore; a chemical sensor within the casing; and a first water detection body including a first detectable chemical element surrounded by water soluble glass, wherein the first water detection body is locatable within a fractured formation and the chemical sensor senses the first detectable chemical element when formation water dissolves the water soluble glass 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
           [0009]      FIG. 1  depicts a schematic view of a well bore completion showing an exemplary embodiment of a dissolvable plug; 
           [0010]      FIG. 2  depicts a cross sectional view of an exemplary embodiment of the dissolvable plug of  FIG. 1 ; 
           [0011]      FIG. 3  depicts a cross sectional view of another exemplary embodiment of the dissolvable plug of  FIG. 1 ; 
           [0012]      FIG. 4  depicts a cross-sectional view of an exemplary embodiment of a dissolution advancement system; 
           [0013]      FIGS. 5A-5C  depict various embodiments of a protective oil-based layer on the dissolvable plug of  FIG. 1 ; 
           [0014]      FIG. 6  depicts a schematic view of an exemplary embodiment of a chemical employing system for removing the protective oil-based layer of  FIGS. 5A-5C ; 
           [0015]      FIG. 7  depicts a schematic view of an exemplary embodiment of a mechanical device for removing the protective oil-based layer of  FIGS. 5A-5C ; 
           [0016]      FIG. 8  depicts a schematic view of an exemplary embodiment of a system for detecting formation water; 
           [0017]      FIG. 9  depicts a circuit diagram for use with a chemical sensor within the exemplary system of  FIG. 8 ; and, 
           [0018]      FIG. 10  depicts a circuit diagram of an exemplary embodiment of a closure device. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    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. 
         [0020]    Referring to  FIG. 1 , a wellbore  10  is shown lined with a casing  12 , also known as a tubular, tubular housing, string, etc. A tubing mounted valve  14  may be located within the string of casing  12 . A packer  16  isolates an annular region  18  between the casing  12  and the wellbore  10 . According to exemplary embodiments of the present invention, a dissolvable plug  20  initially closes off flow from a perforated zone  100  up the internal bore  22  of the casing  12  to the well surface  24 . The dissolvable plug  20  forms a portion of the well tool  26 , and may, in one exemplary embodiment, have an outer diameter which is approximately equal to an internal diameter of the casing  12  forming the flow path to the well surface  24  where the plug  20  is seated. Thus, the plug  20  advantageously need not require any significant constructions or devices that restricts an internal diameter of the internal bore  22  of the casing  12 , however, as shown in  FIG. 2 , a small seat  30  such as seating device or shoulder or other protrusion may be provided to ensure that the plug  20  does not slide out of place. In an exemplary embodiment, the seating device  30  may be made from the same dissolvable material as the plug  20 . 
         [0021]    In an alternative exemplary embodiment shown in  FIG. 3 , in lieu of seating device  30 , the casing  12  may include a section  36  have an internal diameter in an area for receiving the plug  20  that is larger than an internal diameter of a remainder of the internal bore  22  of the casing  12 . In this case, the plug  20  may be formed with the casing  12  prior to positioning the tubing in the wellbore  10 . 
         [0022]    The plug  20  may be formed and pre stressed within a section of the tubing string or casing  12  to provide sufficient strength against pressure within the tubing. In an alternative exemplary embodiment, the plug  20  may first be formed as a separate element and then secured within the casing  12  using an adhesive component such as, but not limited to, the same dissolvable material as the plug  20 . 
         [0023]    In these exemplary embodiments, the plug  20  is made of water soluble glass, which is made from silica and soda. Soda reduces the melting point of silica, which makes it easier to create glass, and soda also renders the glass water soluble. The most prevalent type of glass is soda-lime glass, also called soda-lime-silica glass, where the lime is added to restore insolubility. In one exemplary embodiment of the plug  20 , made from soda and silica and without lime, the water soluble glass plug  20  will dissolve when in contact with water or steam. Some samples have been shown to dissolve at a rate of about 0.0001″ per minute at about 180° F., however the solubility rate is temperature sensitive to the water that it is dissolved in, and salt water has been shown to dissolve the water soluble glass at a slower rate. In a non aqueous environment, the material remains intact at high temperatures, such as about 1500° F. to about 2000° F. As another important feature, the plug  20  is insoluble to oil and petroleum based liquids and this feature may be advantageously employed in the present invention. 
         [0024]    In one exemplary embodiment, the plug  20  is formed using water soluble glass with dimensions and content suitable for its intended applications. By varying and balancing both the thickness of the plug and the content of soda in the glass matrix, the solubility can be modulated. For example, the thickness and soda content of a plug  20  can be adjusted such that a wellbore tool  26 , such as a packer, remains plugged until the required operation is carried out. 
         [0025]    While the plug  20  may be installed in the casing  12  using conventional methods, the removal of the plug  20  may be determined based on intended use. In one exemplary embodiment, the plug  20  is installed in the wellbore tool  26  in a conventional manner and may be allowed to begin dissolving while the operation is being carried out, so long as the plug  20  is not completely dissolved until after the operation is completed. In another exemplary embodiment, the thickness of the plug  20  may be sufficiently thick and the soda content sufficiently low such that the plug  20  barely dissolves even in the presence of water to guarantee that a required operation is completed before dissolution. 
         [0026]    In an exemplary embodiment shown in  FIG. 4 , to advance the dissolution of the plug  20 , at least one fluid port  40 , or a plurality of fluid ports  40  may be provided in an area circumferentially surrounding the plug  20 . Water or heated water may be provided to the plug  20  at a time when the plug  20  is to be dissolved. The temperature of the water and the time the plug  20  is exposed to the water may both be selected to dissolve the plug  20  in a desired amount of time. The fluid ports  40  may be arranged such that the water or heated water is directed towards a portion of the plug  20  that is desired to be dissolved first. 
         [0027]    In yet another exemplary embodiment, as shown in  FIGS. 5A-5C , the plug  20  includes a protective oil-based layer  50  deployed on at least one surface of the plug  20  to prevent the plug  20  from coming into contact with water, thereby retaining its initial structure until the layer  50  is removed and water is introduced to the plug  20 . In an exemplary embodiment shown in  FIG. 5A , the layer  50  is deployed on an upper surface  52  of the plug  20 , such as a surface facing an uphole direction of the wellbore  10 . In another exemplary embodiment shown in  FIG. 5B , the lower surface  54  of the plug  20  includes a protective oil-based layer  50 , such as a surface facing a downhole direction of the wellbore  10 , and in yet another exemplary embodiment shown in  FIG. 5C , at least both the upper and lower surfaces  52 ,  54  of the plug  20  include a protective oil-based layer  50 , such as all surfaces of the plug  20 . 
         [0028]    Removal of the oil-based layer  50  may be accomplished using a mechanical device and/or chemical means. To chemically remove the oil-based layer  50 , surfactants, such as emulsifiers, detergents, etc., may be used to break the bonds holding the molecules of the oil together so that the oil molecules can be separated and rinsed away. As shown in  FIG. 6 , the chemical introduction may occur using fluid ports  40  that direct the oil removing chemical substance towards the oil-based layer  50 . These may be the same ports  40  that direct water or heated water to the plug  20  for dissolution of the plug  20 . The fluid ports  40  may also be used to vacuum the oil removing chemical substance and oil-based layer  50  away from the plug  20 . While certain chemical removal embodiments are described, other devices to chemically remove the layer from the plug would be within the scope of these embodiments. 
         [0029]    As shown in  FIG. 7 , to mechanically remove the oil based layer  50  from the plug  20 , a mechanical device  56  may extend from the casing  12 , such as a scraper or brush which may be used to at least partially remove the protective layer. The scraper or brush may be a single blade used to wipe off the oil, matter used to absorb the oil, a series of bristles, etc. The mechanical device  56  may be actuated using known downhole tool actuators and may rotate along an interior of the casing  12  to wipe off the layer  56 . The mechanical device may also includes elements made of water soluble material, such as water soluble glass, such that it can also be dissolved in the presence of water. While certain mechanical removal embodiments are described, other devices to mechanically remove the layer from the plug would be within the scope of these embodiments. 
         [0030]    Although the plug  20  has been described as being removed by dissolving with water, in yet another exemplary embodiment, the plug may be removed by first breaking the glass structure of the plug  20 . Breaking the glass structure of the plug  20  may be accomplished by using any known fracturing technique. By fracturing the plug  20  and introducing water to interior surfaces of the plug  20 , the plug  20  will quickly dissolve and be absorbed by the wellbore fluid. 
         [0031]    The exemplary embodiments disclosed thus far have provided a glass water soluble plug  20  for use in plugging a tool  26  until removal of the plug  20  is warranted. Alternative exemplary embodiments of designs and methods for employing the water soluble glass material within the wellbore  10  will now be described. 
         [0032]    In one exemplary embodiment for employing water soluble glass in a wellbore  10 , as shown in  FIG. 8 , the water soluble glass is used as a carrier for long term curing chemicals, which are embedded in the glass matrix, for fracturing/stimulating operations. The glass body  104 , when sent down the well bore  10  or into perforations  100  would be able to store chemicals underground and release them only when exposed to formation water. When the glass body  104  is dissolved by formation water, the chemicals are released and enter the casing  12  through openings  108  in tool  110  and they may then be sensed by a chemical sensor  106 , which in turn may send a communication signal that indicates the presence of formation water, may actuate a downhole tool such as opening or closing a sleeve, or may increase a count on a counter. 
         [0033]    Similar to the above-described exemplary embodiment, in another exemplary embodiment for employing water soluble glass in a wellbore  10 , different detectable chemical elements are embedded in the glass matrix and glass bodies  112  including the different detectable chemical elements are pumped in multi-layered fractured formations. That is, a glass body or bodies  104  containing a first detectable chemical element may be pumped or otherwise directed into a first layer or perforation  100  of the well, while a glass body or bodies  112  containing a second detectable chemical element, different than the first detectable chemical element, is pumped into a second layer or perforation  102  of the well which is distanced from the first layer or perforation  100 . First and second chemical sensors  106 ,  114  may be positioned within the casing  12  for detecting the existence of the corresponding chemicals, and may trigger the appropriate response as described above. While only two different detectable chemical elements and layers are described, it would be within the scope of these embodiments to include multiple different chemical elements for detecting formation water from any number of layers. Thus, it is possible to detect from what specific layer formation water is coming from depending on which chemical sensor is activated. While two chemical sensors have been described, it would also be within the scope of these embodiments to employ a single chemical sensor, which reacts differently, depending on which chemical is detected. 
         [0034]    An exemplary embodiment of chemical sensor  106  is shown in  FIG. 9 . Sensor  106  is communicatively connected to and triggers switch  116  closing a circuit to battery  118  and powering actuation mechanism  120 . 
         [0035]    In yet another exemplary embodiment, the water soluble glass is used as an inexpensive override system to actuate a downhole tool. In one such exemplary embodiment, the water soluble glass may be used to shut down a non-deepset safety valve. In a condition where the chamber becomes flooded by water, replacing oil initially present, a passive dissolvable part made with the water soluble glass may then initiate a process that leads to the final closure of a flapper. The process may be completely mechanical, such as by the passive dissolvable part releasing a latch. Alternatively, as represented by  FIG. 10 , the dissolvable part  122  may include an electrode and when a water soluble glass covering of the part  122  is dissolved by water, the electrode is ground to the casing  12  or to the wellbore fluids and completes the circuit. Dissolving the encapsulated electrode completes the circuit and allows power to flow across the actuator mechanism  126  to actuate the downhole tool. 
         [0036]    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.