Abstract:
A wellbore plug and method for retrieving two or more wellbore plugs simultaneously from the wellbore. The wellbore plug can be actuated to an open position and released from engagement in the wellbore. The plug can be locked in an open position, and remain in an open position without regard to weight or tension applied to the plug. The released and locked open plug can be lowered to next plug to be retrieved. Prior to connecting to the next plug, reverse and/or normal fluid circulation can be utilized to clean the next plug. Upon connecting the first plug to the second plug, the second plug can be locked open and released in by applying tension in the same manner as the first plug. The process can continue to retrieve multiple plugs.

Description:
RELATED APPLICATIONS 
     This application is a continuation of application Ser. No. 11/773,308 filed on Jul. 3, 2007, now U.S. Pat. No. 7,950,468, which claims the benefit of provisional application No. 60/818,870, filed Jul. 6, 2006. 
    
    
     FIELD OF THE INVENTION 
     The invention relates in general to wellbore operations and more specifically to a multipurpose plug that facilitates circulation and simultaneous retrieval of two or more multipurpose plugs from the wellbore. 
     BACKGROUND 
     This section provides background information to facilitate a better understanding of the various aspects of the invention. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art. 
     It is common practice in the oil and gas industry to set a number of plugs in a wellbore. This commonly occurs when it is desired to separate various productions zones for stimulation such as fracturing or acid treatment. After stimulation the operator runs into the wellbore with tubing and circulates at the top of the uppermost plug to remove debris. The uppermost plug is then removed either by drilling the plug out or by releasing the plug and retrieving. 
     It is a therefore a desire to provide a multipurpose plug that facilitates circulating. It is a still further desire to provide a multipurpose plug that permits connection to other multipurpose plugs while facilitating circulation at the lowest most multipurpose plug in a manner such that two or more multipurpose plugs may be retrieved from the wellbore in a single trip. 
     SUMMARY 
     In view of the foregoing and other considerations, the invention relates to a wellbore plug and method wherein the plug can be retrieved from the wellbore without being drilled out, without applying tension or weight in combination with rotation, and facilitates the removal of multiple plugs simultaneously while circulating through the plugs. 
     A plug for use in a wellbore of the type having an internal bore formed through its length includes a valve actuatable to an open position allowing fluid flow through the internal bore; a mechanism for locking the valve in an open position; a sealing element that is urged outward from the internal bore into sealing engagement with a tubular positioned therearound; and a mechanism for securing the sealing mechanism in a refracted position wherein the sealing element is disengaged from the surrounding tubular. 
     A method of retrieving at least a first plug and a second plug of the same type from a wellbore, wherein when the plugs are set in the wellbore each plug has a valve in a closed position blocking flow of fluid through the plug and a sealing mechanism expanded into engagement with a wellbore casing providing a seal between the plug and the casing, comprising connecting a conveyance to the first plug; releasing the first plug; moving the first plug into connection with the second plug; and retrieving the first and the second plug from the wellbore simultaneously. 
     A method of using a plug in a wellbore includes the steps of providing a first plug having a bore formed therethrough, a valve in operational connection with the bore and a casing sealing mechanism; setting the first plug in the wellbore with the valve in a closed position and the casing sealing mechanism engaging the casing; and retrieving the plug from the wellbore. The step of retrieving the plug includes connecting a conveyance to the plug; actuating the valve via the conveyance to the open position; locking the valve in the open position; actuating the casing sealing mechanism to a refracted position; and securing the casing sealing mechanism in the retracted position for retrieval from the wellbore. 
     The foregoing has outlined some of the features and technical advantages of the invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or reduced for clarity of discussion. 
         FIG. 1  is a wellbore schematic illustrating an aspect of the invention. 
         FIG. 2A to 2D  are sectional views of an embodiment of a wellbore plug of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. 
     As used herein, the terms “up” and “down”; “upper” and “lower”; and other like terms indicating relative positions to a given point or element are utilized to more clearly describe some elements of the embodiments of the invention. Commonly, these terms relate to a reference point as the surface from which drilling operations are initiated as being the top point and the total depth of the well being the lowest point. 
       FIG. 1  is a schematic illustration of wellbore plugs  10   a ,  10   b  of the invention disposed in a wellbore  12 . Wellbore  12  may be completed with casing  14 . Perforations  16  may be formed through casing  14  before or after placement and setting of plugs  10 . For example, a first plug  10   a  may be run into wellbore  12  and position for treating and/or perforating the first formation  18 . After performing operations at the first formation  18 , a second plug  10   b  may be run into wellbore  12  and set for conducting operations on second formation  20 . This process may continue until the desired formations have been addressed. 
     Once operations are completed, retrieval of plugs  10  may commence. A workover rig or coiled tubing unit  19  is brought on site. Plugs  10  may be retrieved by conveyance  22  singularly or all in a single trip. Conveyance  22  is run into wellbore  12  with a retrieving head  24  and circulating to remove debris from wellbore  12 . Retrieving head  24  is then connected to first plug  10   b . Plug  10   b  is opened to allow circulation through plug  10   b . Plug  10   b  may then be released from sealing connection with casing  14 . Upon actuating plug  10   b  to the released and valve open position, plug  10   b  is locked in the open and released position. Plug  10   b  may then be conveyed down wellbore  12  and connected to plug  10   a . The process of opening, circulating and releasing may be continued until all the plugs have been released. The multiple plugs  10  may then be retrieved from wellbore  12  without requiring multiple trips into wellbore  12 . The ability to lock each plug in a valve open and sealing element retracted position facilitates the retrieval of multiple plugs in a single trip. 
     Referring now to  FIGS. 2A-2D , a cross-sectional view of an embodiment of multipurpose plug  10  is illustrated. Plug  10  comprises an elongated body, generally denoted by the numeral  5 , that forms an internal bore  92  therethrough. Plug  10  includes a top valve seat  26 , crossover sub  28 , bottom valve seat  30 , control finger  32 , thread lock  34 , clip ring  36 , upper collet  38 , lift ring  40 , valve seat  42 , ball valve  44 , valve rotation pin  46 , bottom skirt lock  48 , spacer sub  50 , upper valve body  52 , cage bottom  54 , bottom cone nut  56 , lower collet  58 , sealing element ring  60 , bottom guide ring  62 , sealing element sleeve  64 , upper guide  66 , lifting mandrel  68 , retrieving head sub  70 , retrieving head  72 , wash sleeve  74 , upper cone  76 , lower cone  78 , slip  80 , slip cage  82 , stand off pin  84 , slip cage spring  86 , casing to plug sealing element  88  and lock ring  90 . Valve rotation pin  46  connects ball  44  and control finger  32  facilitating movement of ball  44  between the open and closed positions. 
     Thread lock  34 , also referred to as a shear sub, includes shoulders  94  that are tapered to fit the stop on stand off pin  84 . In the illustrated example the taper of shoulders  94  is forty-five degrees. 
     Sheer pins  96   a  are positioned between upper guide  66  and upper collet  38  to maintain plug  10  in the contracted, or run-in, position. Upon placement of plug  10  in the desired position, weight is applied to plug  10  shearing pins  96   a  and expanding elements  88  into sealing engagement with casing  14 . 
     Stand off pin  84  is held in connection with retrieving head  72  via shear pins  96   c , holding retrieving head  72  and wash sleeve  74  off of the valve assembly permitting circulation of fluid to clean the ball valve and assembly of well debris, for example fracturing sand, before opening the valve. By applying weight via conveyance  22  shear pins  96   c  part and retrieving head  72  moves down for connection to upper valve body  52  for retrieval of plug  10 . 
     Bottom skirt lock  48  is connected to bottom valve seat  30  by sheer pins  96   b  that maintain the valve assembly ( 26 ,  30 ,  42 ,  44 ) in the closed position with ball  44  blocking fluid flow through bore  92  when in the run-in position. Tension applied to plug  10  will shear pins  96   b  moving valve  44  to the open position. 
     Clip ring  36  includes a face having a taper corresponding to the taper of a face of spacer sub  50 . For example, the matching faces may be tapered at ten degrees. Thus, when tension is applied to plug  10 , sub  50  urges clip ring  36  inward and into engagement with bottom valve seat  30  (e.g., groove  36 A). This locking mechanism and method locks ball valve  44  in the open position and facilitates the ability to retrieve multiple plugs in a single trip. 
     Crossover sub  28  and upper collet  38  are connected to one another by shear pins  96   d . Shear pins  96   d  anchor the members together so that sufficient tension may be applied to shift ball valve  44  to the open position. Upon application of sufficient tension the shear mechanism will be released and the valve assembly will be released from collet  38  and the valve assembly, crossover sub  28  and bottom collet  58  are moved up; bottom collet  58  is locked in cone  76 . Slips  80  then retract allowing disengagement of sealing elements  88 . Slip cage spring  86  then urge slip cage  82  into the released position. 
     With reference to FIGS.  1  and  2 A- 2 D, a plug  10  is run into wellbore  12  with ball valve  44  in the closed position to the desired position in wellbore  12 . Plug  10  is actuated expanding sealing elements  88  outward into sealing engagement with casing  14 . Conveyance  22  may then be released from plug  10  for placement of additional plugs  10  or conducting wellbore operations. It is noted that conveyance  22  may be connected to and disconnected from retrieval head sub  70  or disconnection from plug  10  may be at the retrieval head sub  70  and retrieval head  72  connection. 
     When it is desired to retrieve plugs  10  a workover rig or coiled tubing unit  19  may be rigged up. Conveyance  22  is run into wellbore  12  circulating fluid to clean off the plug. Conveyance  22  is then connected to plug  10  via the retrieving head assembly. With wash sleeve  74  and the retrieval head held off of the valve assembly by stand off pin  84 , circulation can continue to clean debris from valve  44 . 
     Weight may then be applied to plug  10  via conveyance  22  parting pins  96   c  thereby moving retrieval head  72  down and into connection to upper valve body  52 . Applying tension to plug  10  via conveyance  22  then actuates valve  44  to the open position and actuates the valve locking mechanism into the locked position holding valve  44  in the open position whether tension or weight is applied to plug  10 . Further tension releases sealing elements  88  from engagement with casing  14  and locks the sealing assembly including elements  88 , slip cage  82 , and slip cage spring  86  into a retracted position. It is noted that circulation through plug  10  and the release and retrieval of plug  10  is accomplished without utilization of any J-slot device. 
     The upper most plug  10   b  may then be retrieved or run down wellbore  12  and connected to plug  10   a  for retrieval by repeating the above release and retrieval process. The invention provides the ability to circulate through more than one plug and to retrieve more than one plug simultaneously. 
     The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the disclosure. Those skilled in the art should appreciate that they may readily use the disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the disclosure. The scope of the invention should be determined only by the language of the claims that follow. The term “comprising” within the claims is intended to mean “including at least” such that the recited listing of elements in a claim are an open group. The terms “a,” “an” and other singular terms are intended to include the plural forms thereof unless specifically excluded.