Abstract:
Method and apparatus used to deploy and process eutectic metal alloy material into an oil, gas or water well for the purpose to plug and seal selected downhole casing leaks. The apparatus includes a power control unit located at surface and a downhole tool that is lowered into the well by standard wireline cable. The downhole tool delivers the necessary quantity of metal alloy, forms the required temporary bridge plug support for containing the molten alloy, melts the alloy by means of electric heating, heats the surrounding wellbore formation, squeezes the molten alloy through the perforations and recovers any excess alloy for subsequent recycling.

Description:
This application claims priority of Provisional Application No. 60/715,553 filed on Sep. 8, 2005 by Thomas A. La Rovere, sole inventor. 
    
    
     CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not applicable 
     REFERENCES CITED 
     
         
         U.S. Pat. No. 6,828,531 B2 Dec. 7, 2004 Spencer 
         U.S. Pat. No. 6,664,552 B2 Dec. 16, 2003 Spencer 
         U.S. Pat. No. 6,384,389 B1 May 7, 2002 Spencer 
       
    
     BACKGROUND 
     1. Field of Invention 
     This invention relates to equipment and methods of use for repairing cracks and plugging holes in the casing of operational wells using a molten metal alloy. The intention of the present invention is to plug said holes with a surface flush to the net inside diameter of the production casing. 
     The particular advantage of the present invention is that it provides a completely integrated tool that performs all processing in a single pass deployment by means of industry standard wireline cable; thereby eliminating the need for workover rigs, multiple tool deployments, the installation of temporary bridge plugs and the subsequent milling or drilling out of residual alloy material. The present invention is particularly suitable for precision plugging of intended perforations which enable fluid communication between the wellbore formation and the production casing and to repair damaged casings in otherwise operational wells caused by corrosion, abrasion, earth movement, pressure bursting or other destructive factors. 
     It is contemplated that the present invention is advantageous for use in shutting off selected intervals in gas wells. 
     2. Description of Prior Art 
     U.S. Pat. No. 6,828,531 B2 Dec. 7, 2004 Spencer describes the use of eutectic metal sealing for oil and gas wells using an electrical resistance or inductive heating tool and forcing the molten alloy through perforations and into the formation or the well cement for the repair of a fault, but does not contemplate or claim the method or means to remotely control the dispensing of controlled amounts of alloy into the heater. The invention does not contemplate, describe nor claim a method or apparatus for use in selective plugging of perforations in producing wells. In addition, the process described by Spencer requires the separate installation setting of a temporary bridge plug and the subsequent drilling out and removal of excess solidified alloy material and the bridge plug. 
     U.S. Pat. No. 6,664,552 B2 Dec. 16, 2003 Spencer describes the use of eutectic metal among other various materials useful for sealing leaks within annuli of well casings of oil and gas wells using an electrical resistance or inductive heating tool. The invention describes the injection of material separately through the annulus vent tube where the material to be melted is deposited within any annulus between the production and surface casing of the well and above the well cement between the casings of interest. The invention does not contemplate the flow of melted sealing material through perforations in the casings and into the formation or the annulus. 
     U.S. Pat. No. 6,384,389 B1 May 7, 2002 Spencer describes the use of eutectic metal among other various materials useful for sealing leaks within annuli of well casings of oil and gas wells using an electrical resistance or inductive heating tool. The invention describes the injection of material separately through the annulus vent tube where the material to be melted is positioned within any annulus between the production and surface casing of the well and above the well cement between the casings of interest. The invention does not contemplate the flow of melted sealing material through perforations in the casings and into the formation or the annulus. 
     Various other processes and methods are utilized by the oil and gas industry for plugging and sealing of well casings including cements, gels and resins, a number of which are cited by the Spencer patents referenced above. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG. 1  is a system block diagram of overall equipment layout. 
         FIG. 2  is a diagrammatic cross sectional view of the entire downhole tool, as suspended by a wireline cable, and nominally positioned within the well production casing adjacent to the perforation zone. 
         FIG. 3  is a diagrammatic cross view of the downhole tool plugging section. 
         FIG. 4  is a system block diagram embodiment of a hydraulic system to actuate a molten alloy flow control valve, expansion collar, expansion squeeze sleeve and bridge plug. 
         FIG. 5  illustrates the downhole tool with bridge plug set prior to melting alloy. 
         FIG. 6  illustrates the process of melting and partial penetration of alloy into a heated zone encompassing well perforations and earth formation channels. 
         FIG. 7  illustrates the process of melting and full penetration of alloy into a heated zone encompassing well perforations and earth formation channels. 
         FIG. 8  illustrates the downhole tool in the process of squeezing molten alloy from the annulus between the casing inside surface and the tool. 
         FIG. 9  illustrates the process of the expansion sleeve retracted subsequent to alloy solidification. 
         FIG. 10  illustrates the final casing plug formed after the tool is retracted. 
         FIG. 11-A  illustrates an alloy material supplied in billet form. 
         FIG. 11-B  illustrates alloy material supplied in pellet form. 
         FIG. 12  is a process sequence flowchart describing the basic operation of the apparatus. 
     
    
    
     REFERENCE NUMERALS IN DRAWINGS 
     
         
         
           
               100  Well casing 
               101  Surface 
               102  Subsurface formation 
               103  Casing perforation 
               104  Perforation zone 
               110  Downhole tool 
               111  Power control unit (PCU) 
               112  Operator controls 
               113  Wireline spool 
               114  Wireline 
               115  Wireline pulley 
               116  Well lubricator 
               117  Sealing gland 
               118  External pressure source 
               119  External pressure valve 
               131  Wireline connector 
               132  Electrical control module 
               133  Hydraulics reservoir 
               134  Hydraulic pumps 
               135  Billet magazine loader 
               136  Alloy billet 
               137  Billet magazine 
               138  Billet dispenser 
               139  Dispense latch 
               140  Billet melting heating module 
               141  Alloy flow valve 
               142  Expansion collar 
               143  Zone heating module 
               144  Expansion squeeze sleeve 
               145  Expansion bridge 
               146  Temperature sensor 
               147  Level sensor 
               148  Inspection camera 
               149  Strain sensor 
               150  Vibration module 
               151  Overflow portal 
               160  Molten alloy 
           
         
       
    
     DESCRIPTION 
     FIGS.  1  Through  12   
     Preferred Embodiment 
     A preferred embodiment of the present invention is illustrated in  FIGS. 1 through 12 .  FIG. 1  illustrates the general configuration of equipment including a power control unit (PCU)  111 , operator controls  112 , wireline spool  113  and wireline pulley  115  located at the surface  101  in proximity to the well casing  100 ; and the downhole tool  110  suspended by the wireline  114  and lowered to a desired depth position within the well casing  100 . Typically the wireline is routed through a well lubricator device  116  mounted at the top of the well casing and passed through a sealing gland  117  to prevent gases from leaking from the well during the process. An external pressure source  118  and pressure valve  119  supplied at the well surface may also be incorporated to control pressure applied to the well casing to beneficially squeeze the molten alloy through the casing perforations and into the heated formation zone. 
       FIG. 2  illustrates the downhole tool assembly  110  as suspended within the well casing  100  to a desired depth in vertical proximity to the casing perforation  103  to be plugged. The downhole tool  110  may conveniently be attached mechanically and electrically to the wireline  114  by means of a wireline connector  131 . An electrical and electronic control module  132  is contained within a pressure vessel. An inspection camera  148  may be conveniently be integrated to allow remote visual inspection by an operator before and after the plugging process. The electronic controls may also conveniently integrate pressure sensors, temperature sensors and wireline strain sensors to provide useful real time process information to the operator. 
       FIGS. 3 and 4  illustrates a preferred embodiment of the downhole tool  110  utilizing an integrated hydraulic reservoir  133  and hydraulic pumps  134  to actuate the billet dispense latches  139 , expansion and retraction of an expansion bridge plug  145 , expansion collar  142 , expansion squeeze sleeve  144  and the molten alloy flow valve  141 . As an alternative to hydraulic power, expansion and retraction functions of the plug, collar, sleeve and valve could be accomplished using electromechanical actuators. 
       FIG. 5  illustrates the downhole tool  110  in the desired position; an alloy billet  136  dispensed into the billet melting heating module  140  and the expansion bridge plug  145  in the expanded condition prior to melting the alloy billets  136 . 
       FIG. 6  illustrates the downhole tool  110  with the expansion bridge plug  145  in the expanded position supporting a pool of molten alloy  160  partially penetrating the casing perforations  103  and formation zone  104 . The alloy flow valve  141  is shown in the position to allow molten alloy  160  to flow to the outside of the zone heating module  143 . 
       FIG. 7  illustrates the downhole tool  110  with the expansion bridge plug  145  in the expanded position supporting a pool of molten alloy  160  fully penetrating the casing perforations  103  and the heated formation zone  104 . The alloy flow valve  141  is shown in the position to allow molten alloy  160  to flow to the outside of the zone heating module  143 . 
       FIG. 8  illustrates the downhole tool  110  with the expansion bridge plug  145 , expansion squeeze sleeve  144  and expansion collar  142  in the expanded positions. Expansion of the squeeze sleeve  144  causes the flow of displaced molten alloy  160  through overflow portals  151  located at the top end of zone heating module  143  where it is received and retained for recovery subsequent to tool extraction. The alloy flow valve  141  is shown in the position to allow molten alloy  160  to flow into and be received and accumulated within the zone heating module  143 . 
       FIG. 9  illustrates the downhole tool  110  with the expansion bridge plug  145 , the expansion squeeze sleeve  144  and expansion collar  142  in their respective retracted positions subsequent to alloy solidification. 
       FIG. 10  illustrates the final solidified casing plug formed in the perforation zone  104  after the tool  110  is retracted. 
       FIG. 11A  illustrates a preferred embodiment of a dimensionally fabricated alloy billet which provides for ease of handling and reliable dispensing. Alternatively,  FIG. 11B  illustrates alloy material provided in pellet form. 
       FIG. 12  is a simplified process description flowchart of a preferred embodiment as described herein. 
     METHOD OF OPERATION 
     Preferred Embodiment 
     The present invention is useful for plugging perforations in an operational well that includes one or more of the following conditions:
         a. a single casing or a plurality of concentric casings positioned within a wellbore.   b. non-intentional perforations or damage caused by corrosion, drill abrasion, earth movement, pressure bursting or other factors that are considered detrimental to the operational purposes of the well.   c. intentional perforations specified for the purpose to allow ingress of gas or fluids from the wellbore formation into the central production casing.   d. leakage through casing collars or couplings used to connect casing sections.       

     The downhole tool  110  is prepared for deployment into a well by connection to the wireline  114  and loading a quantity of alloy billets  136  into the billet magazine  137  through the billet magazine loader  135 . Alternatively, the alloy material may be supplied as pellets or in wire form with appropriate mechanisms provided to control and direct the dispensing of the material as required. The total quantity of alloy to be supplied depends on the expected volume to be filled in the perforated casing and wellbore within the heated perforation zone  104 . 
     The downhole tool  110  is deployed through the well lubricator  116  and into the well casing  100  to a desired depth using conventional industry techniques, and positioned adjacent to the casing perforations  103  to be plugged. Said position would have the expansion bridge plug  145  to be located a few inches below the bottommost perforation. 
     Upon a telemetry command initiated by an operator, the expansion bridge plug  145 , comprised of an inflatable bladder, is actuated to expand to form a seal against the casing inside surface. An alloy billet  136  is then dispensed by the billet dispenser  138  into the billet melting heating module  4 - 30   140  and electric power controlled by the PCU  111  is applied to melt the billet. The melted alloy flow control valve  141  is commanded to cause melted alloy  160  to be routed from the billet melting heater to the outside of the tool zone heating module  143 . Electric power is also simultaneously applied to the zone heating module  143  to beneficially heat the perforation zone  104  to achieve a temperature to maintain a desired mass of molten alloy  160 . 
     As the billet located in the billet melting heating module  140  proceeds to melt, melted alloy flows down to accumulate as a molten pool above the bridge plug  145  and about the expansion squeeze sleeve  144  whereupon it flows through perforations  103  and also beneficially saturates into the heated permeable perforation zone  104  surrounding the casing. 
     Level sensors  147  incorporated in the zone heating module  143  determine the top of the molten alloy pool  160  in order to control the dispensing of additional alloy billets  136  to be melted. Said level sensors are of the inductive type which have been found to satisfactorily discriminate between molten metal alloy and typical well fluids such as water. The inductive sense coils can also be conveniently located remotely from their signal conditioning electronics and can be constructed to reliably function at the temperature of molten alloy. 
     Alloy billets  136  are singularly dispensed into the billet melting heating module  140  by sequential actuation of the upper and lower dispense latches  139 . 
     During the melting process, billets are dispensed such that the level of molten alloy  160  is maintained below the overflow portals  151  located at the top end of the zone heating module  143 . 
     During the melting process, the operator may send a command to the downhole tool  110  to actuate an integrated electromechanical vibration module  150  as a means to motivate molten alloy  160  through the casing perforations  103  and to saturate the permeable heated formation zone  104 . 
     During the melting process, the operator may command that a specified pressure supplied by an external pressure source  118  and controlled by an external pressure valve  119  be applied to the well casing  100  as a means to further motivate penetration of the molten alloy  160  through the casing perforations  103  and to saturate the permeable heated formation zone  104 . Said pressure may be either a pressurized gas such as air, or a fluid such as water supplied at the well surface. 
     Determination of the completion of the process is based telemetry data transmitted from the downhole tool  110 . These parameters include temperatures sensed at the downhole tool, the time period and quantity of power applied to melt the alloy, the volume of alloy dispensed, the estimated casing and perforation volume to fill, the height of the molten alloy, formation thermal characteristics, etc. 
     Once a sufficient volume of alloy has been melted and the decision is made to complete the process, a command is sent to the tool  110  to actuate expansion of the squeeze sleeve  144 , expansion of the collar  142  and to redirect the alloy flow valve  141 . The squeeze sleeve  144  and expansion collar  142  are each comprised of inflatable bladders. The expanded squeeze sleeve  144  then presses uniformly against the inside surface of the casing  100  thereby causing molten alloy  160  to be displaced upward and thereby flow through overflow portals  151  provided in the zone heating module  143 . Excess molten alloy is thereby directed by the alloy flow valve  141  into the central bore of the zone heating module  143  where it is captured for recovery. The collar  142  beneficially prevents any molten alloy  160  from flowing upward beyond the overflow portals  151  to an unheated section of the tool. 
     Once the squeeze sleeve  144  is fully expanded, electrical power supplied to the downhole tool billet melting heating module  140  and zone heating module  143  is switched off in order to allow the molten alloy to cool and solidify. Downhole temperature telemetry data is monitored in order to determine when the alloy attains solidification. 
     Once the temperatures measured at the downhole tool  110  drop a point to ensure the alloy has solidified, a command is sent to the tool  110  to retract the expansion collar  142 , to retract the expansion squeeze sleeve  144  and to retract the expansion bridge plug  145 , whereupon the tool  110  is extracted from the well casing  100 . Removal of the tool then leaves all casing perforations  103  plugged while the inside volume of the casing  100  is left clear and flush to the net inside surface bore of the production casing. 
     During extraction of the tool  110  from the plugged location, tension on the wireline  114  as measured by the strain sensor  149  is used to ensure tension exerted on the wireline is kept within operational stress limits and that the tool is clear and not frozen in place by alloy that may have detrimentally solidified within the casing  100  or by other interfering obstructions within said casing. 
     After tool extraction from the well at the surface  101 , recovered alloy is melted and drained from the tool  110  by applying electric power to the zone heating module  143 . 
     The diameter of the downhole tool  110  is scalable to accommodate different casing sizes. The length of the downhole tool  110  is determined as required to provide adequate length of heated zone and to store sufficient amount of alloy billets  136  in the billet magazine  137 . 
     Embodiments of methods and apparatus to plug perforations and to seal leaks in a well casing have been described. In the description, for purposes of explanation, numerous specific details are set forth to provide a thorough understanding of the present invention. It will be appreciated, however, by one skilled in the art that the present invention may be practiced without these specific details. In other instances, structures and devices are shown in block diagram form. Furthermore, one skilled in the art can readily appreciate that the specific sequences in which methods are presented and performed are illustrative and it is contemplated that the sequences can be varied and still remain within the spirit and scope of the present invention. 
     In the foregoing detailed description, apparatus and methods in accordance with embodiments of the present invention have been described with reference to specific exemplary embodiments. Accordingly, the present specification and figures are to be regarded as illustrative rather than restrictive.