Abstract:
Application of the method and device to a water well will permanently seal the well casing in order to prevent hydraulic cross-contamination with other water wells in the area. The method employs a string to explosive modules in spaced relation along the depth of a well casing. This weighted string of explosive modules is lowered into the well casing, wet concrete should then be introduced into the casing, after which the explosive elements are detonated sequentially, starting at the top of the well. Detonation of the elements in such a manner should force the wet concrete or cement out through the well casing perforations, so that the well casing will be entirely captured within the cured concrete. The individual explosive elements are made from detonating cord and metallic ball bearings wrapped into bundles, and then the bundles are bound in suitable adhesive tape.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to water well operations and, more specifically, to a Shot Perforator Device and Method for Water Well Bore Decommissioning. 
     2. Description of Related Art 
     At the end of the life of a water well, it is generally not desirable to simply leave the well as an abandoned hole. The fear is that fall hazards, source contamination, or terrain collapses may occur and so it is not uncommon to be required to decommission the well by some means. 
     In the past, wells have been decommissioned through a variety of unsafe and/or ineffective methods. These methods have included attempts to fill the well casing with sand or gravel or even with concrete or cement. The problem with filling the casing is that only the inside of the casing is being filled as a result of these approaches and the surrounding area around the outside of the well casing remains a void that can cause future safety issues. 
     A more recent example of a method for well decommissioning is shown in Turley, et al., U.S. Patent Publication No. 2008/0128133. While Turley seeks to safeguard the abandoned well, it essentially uses a plug to do so. Although this approach will safeguard the top of the well for the purposes of falling hazards, it will not prevent cross contamination and future erosion of the terrain surrounding the well. What is needed is a system and method that will decommission a well and leave it in a condition that is safe from hydraulic cross contamination, erosion issues and fall hazards. 
     SUMMARY OF THE INVENTION 
     In light of the aforementioned problems associated with the prior systems and methods, it is an object of the present invention to provide a Shot Perforator Device and Method for Water Well Bore Decommissioning. Application of the method and device to a water well should permanently seal the well casing in order to prevent cross-contamination with other water wells in the area. The method should employ a string of explosive modules in spaced relation along the depth of a well&#39;s blank casing. This weighted string of explosive modules should be lowered into non-perforated sections of the well casing, wet concrete should then be introduced into the casing, after which the explosive elements should be detonated sequentially, starting at the top of the well. Detonation of the elements in such a manner should force the wet concrete or cement out through the newly-created well casing perforations, so that the well casing will be entirely encapsulated within the cured concrete. The individual explosive elements should be made from detonating cord and metallic ball bearings wrapped into bundles, and then the bundles should be wrapped up in suitable adhesive tape. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The objects and features of the present invention, which are believed to be novel, are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages, may best be understood by reference to the following description, taken in connection with the accompanying drawings, of which: 
         FIG. 1  is a partial side view of a preferred embodiment of a perforation element of the system of the present invention; 
         FIG. 2  is a shot perforation module utilizing three of the elements of  FIG. 1 ; 
         FIG. 3  is a partial cutaway side view of a seal cap used in the module of  FIG. 2 ; 
         FIG. 4  is a side view of a shot perforation assembly of the present invention using the modules and elements of  FIGS. 1 and 2 ; 
         FIG. 5  is a cutaway side view of a well casing where the method of the present invention is being executed; and 
         FIGS. 6A and 6B  are a flow chart depicting the steps of a preferred embodiment of the well decommissioning method by catastrophic perforation of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description is provided to enable any person skilled in the art to make and use the invention and sets forth the best modes contemplated by the inventor of carrying out his invention. Various modifications, however, will remain readily apparent to those skilled in the art, since the generic principles of the present invention have been defined herein specifically to provide a Shot Perforator Device and Method for Water Well Bore Decommissioning. 
     The device of the present invention and the method to use it involves the use of a custom-built, liner-shaped explosive device that will catastrophically destroy and decommission an abandoned water well bore. The objective of the device and method is to perforate and/or breach the well&#39;s casing while simultaneously injecting liquid cement or concrete just outside the well&#39;s casing (through the holes in the well casing). This process will prevent any hydraulic cross contamination from the well being decommissioned with any surrounding active or future well sites. 
     The present invention can best be understood by initial consideration of  FIG. 1 .  FIG. 1  is a partial side view of a preferred embodiment of a perforation element of the system of the present invention. The discrete item used to make up the decommissioning system is a perforation element  10 . A perforation element is a bundle of custom detonating cord wrapped in an explosive bundle along with several carbon steel ball bearings that will essentially create an explosive device that will shoot these ball bearings into the walls of the casing thereby creating perforations through which liquid concrete or cement can pass to the outside of the well casing. 
     The perforation element  10  comprises an explosive bundle made of a number of wraps  14  in a detonating cord  12 . The detonating cord preferably has a double layer PVC jacket that provides a water-tight environment and additional protection to the explosive material on the inside of the cord  12 . Since it is not uncommon for the system to be left sitting in water and/or liquid concrete or cement for ten hours or more in the course of the decommissioning process, the number of wraps  14  is guided by the size and condition of the well itself. For example, a perforation element  10  may have five to seven wraps  14  for well casings having a four- to six-inch diameter. In another example, 21 to 23 wraps  14  are used for a diameter of 20 to 22 inches. While the wraps  14  are created, a plurality of ball bearings  16  are being added along the way. These ball bearings  16  are preferably ⅜-inch diameter of carbon steel material; however, other size and composition bearings may be suitable. Once the wraps are complete for the element  10 , the element  10  will be bound with tape  8  such as conventional electrical tape. The binding tape  18  serves to increase the load factor of the explosives so that less explosives will create a more severe detonation and damage to the well casing. As shown here, the detonating cord  12  extends both upwardly and downwardly to the next element in the string. 
     If we now turn to  FIG. 2 , we can examine how these elements are interrelated.  FIG. 2  is a shot perforation module utilizing three of the elements of  FIG. 1 . It should be understood that this is merely an example of how a series of elements  10  are interconnected to create each module  20 . Each module  20  is generally forty-six (46) feet in length, with the spacing  11  between elements  10  being between two and three feet (per element). 
     In this depiction, the first shot perforation module  20  is shown. This module  20  would be the top module in a string of modules making up the entire assembly as will be shown in more detail below in connection with  FIG. 4 . The detonating cord  12  interconnects three shot perforation elements  10  as depicted above in  FIG. 2 . The elements  10  are spaced by element spacing  11 . This spacing  11  will change depending on the diameter and condition of the well casing. For example, it is typical to have two-foot spacing for well casings having diameters of less than 12 inches while three-foot spacing would be used for those well casings equal to or greater than 12 inches in diameter. At the top end of the first shot perforation module  20 , the detonating cord terminates in a seal cap  22  which will be discussed below in connection with  FIG. 3 . A detonator  24  is attached to the seal cap  22  and this detonator  24  will control the detonation of the entire first shot perforation module  20 . The other modules discussed below in  FIG. 4  each have their own detonator. A lead line  26  extends from the first detonator to a safe area away from the well casing. The lead line  26  is an electrical cable that&#39;s used to detonate the detonators  24 . At the bottom end of the module  20 , a second seal cap  22  isolates the detonating cord  12  of the first shot perforation module  20  from the rest of the modules making up the system. 
       FIG. 3  discusses the structure of the seal cap.  FIG. 3  is a partial cutaway side view of a seal cap used in the module of  FIG. 2 . As shown here, the detonating cord  12  terminates in an end  13  which could be just a blank end as shown here or it could be an end where a detonator would be located. The seal cap  22  is a metal cap slid over the end  13  and then maintained in place permanently by a series of crimps  24 . The seal cap  22  prevents liquid from penetrating into the detonating cord and interfering with the explosive capability of the cord  12 . 
       FIG. 4  shows the overall shot perforation assembly.  FIG. 4  is a side view of a shot perforation assembly of the present invention using the modules and elements of  FIGS. 1 and 2 . As shown here, a series of modules  20 ,  32 ,  34  are interconnected and spaced out along the length of the well casing. At the bottom end, a weight  36  is hung from a long piece of wire, such as piano wire, that runs the entire length of the assembly  30 . The wire (not shown) supports all of the elements of the modules  20 ,  32 ,  34 , and is tied off at its end at the weight  36 . The wire relieves the stress of the hanging weight from the detonating cord interconnecting the modules and elements. 
     The weight  36 , hanging from the assembly  30  below the third module  34  serves to prevent the shot perforation assembly  30  from floating upward from its desired pre-detonation position when the wet cement or concrete is introduced into the well casing. The weight  36  is at least ten pounds in weight and has a length that is greater than the casing diameter. These aspects will also aid in preventing the assembly  30  from floating away from its placement position. As discussed above, the lead line  26  terminates at the detonator  24  and seal cap  22  which comprised the top end of the first perforation module  20 . The second perforation module  32  terminates in a seal cap at its top end and a seal cap  22  and detonator  24  at its bottom end. Similar to the first module  20 , the third module  34  has a seal cap  22  and detonator  24  at its top end and terminates in a seal cap  22  at its bottom end. Generally the upper seal cap  22  and detonator  24  for the complete assembly  30  is placed approximately 6 to 10 feet below the surface of the wet cement or concrete and can extend as deep as 100 or 150 feet. A typical module length is approximately 46 feet, with a elements spaced at approximately 2 to 3 feet. The lead line  26  is generally fifteen (15) feet long, with its conductive end fitting being connected to a Shooting Panel (device outside of the well area that controls the detonation). 
       FIG. 5  depicts the initial steps of the perforation process.  FIG. 5  is a cutaway side view of a well casing where the method of the present invention is being executed. In  FIG. 5  we see prior to detonation of the assembly  30 . A trim pipe  38  has been inserted into the well casing  40  so that liquid concrete or cement can be introduced to the well casing  40  all the way at the bottom of the well casing  40  without damage to the assembly  30 . A concrete pumper would be hooked up to the top end of the trim pipe  38  in order to introduce the concrete. The perforation assembly  30  is dropped into the well casing  40  and the lead line  26  is threaded out through a protective sleeve  42 . The protective sleeve  42  is typically going to be made from a plastic material that is hard to prevent crushing yet flexible to allow for adjustment due to terrain or orientation of the other elements in the system. Once the concrete has been completely introduced into the well casing, the trim pipe is removed and the cover plate  44  is laid atop the protective sleeve  42  and then chained to the ground. 
     As discussed above, the lead line  26  extends approximately ten (10) feet down into the well casing  40 , leaving approximately five (5) feet of lead line  26  outside of the well casing  40 , connected to the shooting panel (not shown). 
     The flow chart of  FIGS. 6   a  and  6   b  provide additional detail regarding this new method.  FIGS. 6   a  and  6   b  are a flow chart depicting the steps of a preferred embodiment of the well decommissioning method by catastrophic perforation of the present invention. The well decommissioning method by catastrophic perforation  46  commences by lowering the trim pipe into the well  100  as shown above in  FIG. 5 ; however, in order to create the perforation assembly, the well casing must first be inspected by camera in order to derive the placement and number of wraps on the perforation elements of binding tape as well as the spacing of the perforation elements which is a function of the diameter, age and condition of the well casing. The only way to truly ascertain these conditions is through visual inspection. Once the trim pipe has been lowered into the well  100  the shot perforation assembly is lowed into the well casing beside the trim pipe  102 . At this point, liquid concrete or cement is injected into the well until the well casing is full  104 . The trim pipe is then removed  106  and the well is covered with a cover plate that is then attached to the ground with chains  108 . Generally a safety weight is placed atop the cover plate  110  such as a 300-pound dead weight that can be easily lifted by a forklift or crane. Once the safety weight is in place, the shot perforation modules are detonated  112 . What is unique here is that the elements are not detonated simultaneously, but rather are detonated sequentially. The top module is detonated first  112   a  after which the middle module is detonated  112   b  and then the bottom module is finally detonated  112   c . The modules are detonated at approximately one-and-a-half second intervals. The result is to utilize the weight and viscosity of the cement or concrete and to sequentially cause the concrete to compress down into the well and push out through the perforations formed in the wall of the well casing. This creates a continuous squeezing effect, forcing wet concrete or cement to be pushed down and out through the perforations into the surrounding area around the well casing. Once the detonations have occurred, the cover plate is removed  114  and a mechanical depth sounding is performed in order to confirm that the liquid concrete or cement level has dropped adequately. It is common for that liquid level to drop one-third the overall length of the shot perforation assembly  30 . The well is then refilled with cement or concrete  118  to within five feet of the top of the well. Approximately 24 hours later after the initial cure is complete, the area around the well casing is excavated to a depth of approximately ten feet, the top of the well casing is cut off and removed, a cement or concrete “mushroom cap” is poured over the casing, and, finally, the hole is refilled with the dirt that was initially removed  120  which then completes the method  122 . 
     Those skilled in the art will appreciate that various adaptations and modifications of the just-described preferred embodiment can be configured without departing from the scope and spirit of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.