Abstract:
A method for sealing a wellbore includes moving a running tool with a sealing material disposed therein into a wellbore proximate a portion of the wellbore to be sealed. A cylinder is moved into the wellbore along with the running tool proximate to the portion to be sealed. The cylinder defines an annular space between an exterior thereof and an interior of the wellbore. The sealing material is deployed into the annular space. The running tool is then removed from the wellbore.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    Priority is claimed from U.S. Provisional Application No. 61/021,722 filed on Jan. 17, 2008. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable 
       BACKGROUND OF THE INVENTION 
       [0003]    1. Field of the Invention 
         [0004]    The invention is related generally to the field of wellbore construction and repair. More particularly the invention is related methods and devices for selectively repairing leaks or hydraulically closing perforations in strings of pipe disposed in a wellbore drilled through subsurface rock formations. 
         [0005]    2. Related Art 
         [0006]    Wellbores drilled through subsurface rock formations typically include one or more lengths of pipe (“strings”) disposed therein. The pipe may be cemented into the open, drilled wellbore (called a “casing” if extending to the surface or a “liner” if extending only part way of the wellbore) to hydraulically isolate the subsurface formations and to protect the mechanical integrity of the wellbore. Another pipe string may be coaxially inserted into a casing in the wellbore to increase fluid velocity along the wellbore (such string called production or injection “tubing” depending on fluid direction of movement) as fluid is withdrawn from a subsurface reservoir or is injected into a reservoir. 
         [0007]    In certain cases, casings or tubings can develop leaks. Such leakage may be caused by corrosion resulting in holes in the pipe, by threaded couplings on the pipe not being properly assembled (“torqued up”) during wellbore installation, among other causes of leaks. 
         [0008]    It is also known in the art that part of a wellbore drilled through a subsurface reservoir needs to be hydraulically closed (“shut off”) when the fluids entering the wellbore from certain parts of a reservoir are not the fluids intended to be produced to the Earth&#39;s surface, as for example, water. Such undesired fluid entry can occur, for example, in the later stage of production from a reservoir, for example due to wrongly placed perforations and water coning, among other reasons. 
         [0009]    The present invention relates to sealing wellbore sections that have such unwanted leakage or unwanted fluid production. In some examples, the method uses an induction-heating tool such as one described in U.S. Pat. No. 7,036,593, entitled Cement heating tool for oil and gas well completion, and issued to Thomas A. Larovere. Another such tool is described in Canadian Patent No. 2,592,556 entitled, Method and apparatus for plugging perforations, invented by Homer L. Spencer. 
       SUMMARY OF THE INVENTION 
       [0010]    A method for sealing a wellbore according to one aspect of the invention includes moving a running tool with a sealing material disposed therein into a wellbore proximate a portion of the wellbore to be sealed. A cylinder is moved into the wellbore along with the running tool proximate to the portion to be sealed. The cylinder defines an annular space between an exterior thereof and an interior of the wellbore. The sealing material is deployed into the annular space. The running tool is then removed from the wellbore. 
         [0011]    A method for sealing a wellbore according to another aspect of the invention includes moving an induction heating device with a thermally actuated sealing compound into a wellbore proximate a portion of the wellbore to be sealed. An annular cylinder is moved into the wellbore along with the induction heating device. The induction heating device is activated until the compound is actuated. The fused compound is moved into an annular space between the cylinder and the wellbore. The heating device is then withdrawn from the wellbore. 
         [0012]    The invention described herein is based on using a device such as induction heating tool in combination with a device that enables a cylindrical, hollow plug to be placed and sealingly engaged in a wellbore. 
         [0013]    Also, the invention described herein can be used for placing plugging materials by other tools, where plugging material can be epoxy, rubber-type compound, resins or other similar suitable fusible materials. 
         [0014]    Other aspects of the invention will be apparent from the description and claims that follow. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  shows an example wellbore having a leak in a tubing. 
           [0016]      FIG. 2  shows an example device used to emplace sealing compound proximate the leak shown in  FIG. 1 . 
           [0017]      FIG. 3  shows sealing compound after cure and after removal of the emplacing device of  FIG. 2 . 
           [0018]      FIG. 4  shows a section of a perforated casing after sealing using the device shown in  FIG. 2 . 
           [0019]      FIG. 5  shows an example of a two stage sealing device similar in principle to the device shown in  FIG. 2 , but in  FIG. 5  an upper seal bore is introduced in the lower (first installed) cylinder device. 
           [0020]      FIG. 6  shows an upper (second) cylinder device landed into the seal bore of the first (Lower) cylinder, forming a seal between upper and lower cylinder, and how sealing compound is placed by gravity in upper cylinder. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]      FIG. 1  illustrates a casing string ( 1 ) as it would appear disposed in a wellbore (not shown) having inserted therein a production tubing or injection tubing ( 2 ). The tubing string ( 2 ) shown in  FIG. 1  has a leak shown generally at ( 3 ). The arrangement shown in  FIG. 1  may be a tubing within a casing as described, or the arrangement can be two coaxial casing strings. In a method according to the invention it is desired to seal off the leak ( 3 ). 
         [0022]      FIG. 2  illustrates how the leak ( 3 ) can be sealed off using an induction-heating tool ( 4 A) or similar device suspended from a running tool ( 4 ). The running tool ( 4 ) may be suspended from the end of a pipe string such as a workover string, drill string, coiled tubing or other device known in the art to deploy tools in a wellbore. The running tool ( 4 ) is used to insert an annular cylinder ( 9 ) explained below into the wellbore tubing ( 2 ) or casing ( 1 ). On the lower side of the running tool ( 4 ) a seal and hanger system ( 6 ) secures a cylindrically shaped device (“cylinder”) ( 9 ), having a sealing system ( 10 ) in the lower end of the cylinder ( 9 ). The sealing system may be metal or elastomer, for example and is used to sealingly engage the cylinder ( 9 ) to the interior of the tubing or casing. A centralizer ( 7 ) in the upper section of the cylinder ( 9 ) may be provided to ensure centralization. When the cylinder ( 9 ) has been lowered into the wellbore (inside the casing  1  or the tubing  2 ) to the required position (depth), the induction-heating tool ( 4 A) is actuated, causing a sealing compound ( 8 ) disposed within the body of the heating tool ( 4 A) to be melted or activated. The heating tool ( 4 A) may include devices such as a temperature sensor (not shown) to indicate to the system operator that the sealing compound ( 8 ) is ready for deployment. As soon as the operator determines that the sealing compound ( 8 ) is fully fused or activated, and is ready to be released, dump port(s) ( 5 ) in the running tool ( 4 ) are opened, causing the sealing compound ( 8 ) to be released into the annular space between the cylinder ( 9 ) and the interior of the casing ( 1 ) or tubing ( 2 ). The sealing compound ( 8 ) is preferably made from material having a higher density than the fluids in the wellbore, so that the sealing compound ( 8 ) will then flow to the annular area between the cylinder ( 9 ) and the pipe (casing ( 1 ) or tubing ( 2 )) to be repaired or sealed off. The lower sealing system ( 10 ) will ensure that the compound ( 8 ) does not flow past the longitudinal end of the cylinder ( 9 ). After the sealing compound ( 8 ) is deployed, the heating tool ( 4 A) can be switched off, and the sealing compound ( 8 ) is allowed to cure, creating a sealing plug in the wellbore tubing or casing. In the present example, the sealing compound ( 8 ) can be any thermally activated or thermochemically activated material, such as thermoplastic, thermoset plastic, elastomer, certain low melting point metals, heat activated resin or the like. 
         [0023]    As soon as the compound ( 8 ) has solidified or fully cured, a pressure test can be performed to ensure proper sealing in the casing ( 1 ) or tubing ( 2 ). Thereafter, the induction-heating tool ( 4 A) can be released from the cylinder ( 9 ) and retrieved to the surface. 
         [0024]    The cylinder ( 9 ), as well as the sealing system ( 10 ) and the centralizer ( 7 ) can be manufactured from materials susceptible to easy removal from the wellbore. One example is a composite material such as glass fiber or carbon fiber reinforced plastic. Another example metal such as aluminum. Aluminum has the advantages of higher strength that composites, and can be dissolved after a short time in a wellbore having suitable caustic agents, thus causing the annular cylinder shaped sealing plug created by the sealing compound ( 8 ) to have a larger internal pass through diameter. If the cylinder ( 9 ), sealing device ( 10 ) and the centralizer ( 7 ) are made from composite material, the foregoing devices may be removed from the casing or tubing by milling or grinding, using a mill or grinding device that will not damage the casing or tubing. 
         [0025]    The same method of repair plug placement can be used without the heating tool ( 4 A). In such examples, other types of sealing compounds that do not require heating for activation may be used, such as such as chemically activated resins, chemically activated rubber generating compounds, epoxy, and the like. In such examples, the sealing material may be transported to the running tool from the surface either through a casing or tubing inserted into the well, or by an intervention pipe deployed in the well, such as coiled tubing or small diameter threadedly coupled tubing. 
         [0026]      FIG. 3  illustrates how the cylindrical sealing material ( 8 ) will appear after the cylinder ( 9 ) and centralizer ( 7 ) have been removed such as by solution (in the case of aluminum or other chemically sacrificial metal) or by milling (in the case of composite materials). 
         [0027]      FIG. 4  illustrates how the example method explained above can be used to seal part or all of a perforated wellbore section, where the example shows lower perforations ( 11   b ) sealed off using a plugging, cylindrical shaped sealing compound ( 8 ). Upper perforations ( 11   a ) are not sealed off. The foregoing example is typical in the circumstances that the lower perforations ( 11   b ) allow high water content in the produced fluid to enter the casing or tubing, while the upper perforations ( 11   a ) would continue producing relatively water free hydrocarbons. In such circumstances, the wellbore operator would desire to seal the lower perforations ( 11   b ) while leaving the upper perforations ( 11   a ) open. 
         [0028]      FIG. 5  illustrates an example where a sealing operation is performed in two stages including first installing a lower cylinder ( 14 ) substantially as described above with reference to  FIG. 2 . After the lower cylinder ( 14 ) is installed, and referring to  FIG. 6 , an upper cylinder ( 12 ) is landed into the lower cylinder ( 14 ) using a seal system ( 13 ) to seal the annular space longitudinally between the upper ( 14 ) and lower ( 12 ) cylinders. The foregoing method creates two sealing material plugs ( 8 ) which also function as an anchor for the cylinders ( 12 ,  14 ). The cylinders ( 12 ,  14 ) then can remain in the wellbore to provide added erosion protection for the sealing material plugs ( 8 ) with respect to wellbore fluids flowing from the reservoir to the Earth&#39;s surface. In addition, a leaking section of the tubular can be sealed off, where short or long length lower section of upper cylinder can be used to space out a sealing system according to the particular length required. 
         [0029]    While the invention has been described in terms of a limited number of specific examples, those skilled in the art, having the benefit of the present disclosure will readily devise other implementations which do not depart from the scope of what has been invented. Accordingly, the invention shall be limited in scope only by the following claims.