Abstract:
An annular pack for a cylindrical member for use in a wellbore includes a housing adapted to be mounted about an exterior circumference of the cylindrical member. The housing has mutually engagable annular segments. At least one of the annular segments defines a chamber for housing an electrical device.

Description:
This application is a divisional of U.S. application Ser. No. 09/209,912, filed Dec. 11, 1998 now U.S. Pat. No. 6,280,874. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The invention relates generally to annular packs for use in a wellbore. 
     2. Background Art 
     Tools requiring electrical power are often used for conducting various operations in a wellbore. This creates a need for portable electrical power, preferably power that can be mounted directly onto a downhole tool. One way of providing electrical power downhole is through the use of a battery pack. Typically, the battery pack is constructed of rigid plastic, epoxy, fiberglass, or aluminum and is mounted on or inside a downhole tool. One or more annular cells or cylindrical cells are contained within the battery pack. The cells generally are immobilized inside the battery pack by an epoxy. In order to mount or dismount the annular battery pack onto the downhole tool, the tool may have to be disassembled. Disassembly of the tool makes replacing a battery pack time consuming and, in certain cases, is impossible at the job site. For quicker job turnaround, it is desirable that the battery be removable from the tool without use of specialized equipment not available at the job site. 
     SUMMARY OF THE INVENTION 
     In general, in one aspect, an annular pack for a cylindrical member for use in a wellbore has a housing adapted to be mounted about an exterior circumference of the cylindrical member having a plurality of mutually engageable annular segments. At least one of the segments defines a chamber for housing an electrical device. 
     In accordance with one or more embodiments of the invention, the annular pack may have a cell for providing electrical power. The cell for providing electrical power may be shaped to match a shape of the chamber. The shape of the chamber may be cylindrical. The shape of the chamber may match a shape of the segment having that chamber. Each of the segments may have an alignment key and a cut-out for mating a respective alignment key on another segment. The segments may be electrically connected to one another when engaged. At least two of the segments may be electrically connected in parallel or series. A segment may have a plug for electrical connection to a tool. The segments may be electrically isolated from one another when engaged. The annular pack may include an electrical circuit disposed within the chamber. 
     In general, in one aspect, a power cell for mounting in an annular pack for providing power to a downhole tool, includes a housing having a top, bottom, and sides shaped to fit within a chamber in the annular pack, battery means for generating electricity disposed within the housing and a seal element arranged to provide a passage for electricity from the battery means through the housing. 
     In accordance with one or more embodiments of the invention, the power cell may include a strain relief tab within the housing for electricity connecting the battery means to the seal element. The seal element may be a glass seal integrally mounted in the cell. The power cell may include a lid, wherein the glass seal is integrally mounted in the lid. The seal element may be a glass-to-metal seal with a chamfered rim. The power cell may include a spring for biasing the battery means to one side of the housing under downhole conditions. The spring may be a C-shaped spring. 
     In general, in one aspect, a method of integrally forming a glass seal includes providing a lid for a cell, forming a hole in the lid, disposing a post surrounded by an annular layer of glass within the hole and heating the cell until the glass seals to the lid. 
     In general, in one aspect, a method of providing power to a downhole tool includes providing a housing adapted to be mounted about an exterior circumference of the cylindrical member having a plurality of mutually engageable annular segments. At least one of the segments defines a chamber. The method also includes placing a cell for producing power within the chamber, mounting the plurality of annular segments about the cylindrical member and providing power to the tool from the cell. 
     Other advantages and features will become apparent from the following description and from the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a split annular battery pack mounted on a downhole tool; 
     FIG. 2 shows the split annular battery pack of FIG. 1 disassembled; 
     FIG. 3 shows a split annular battery pack mounted on a downhole tool having alignment mechanisms and respective cut-outs; 
     FIG. 4 shows the split annular pack of FIG. 3 disassembled; 
     FIG. 5 shows an exploded view of one embodiment of the split annular battery pack with floating terminals; 
     FIG. 6 shows an exploded view of one embodiment of the split annular battery pack with a contact block; 
     FIG. 7 shows a cross-sectional view of the contact block shown in FIG. 6; 
     FIG. 8 shows an exploded view of the split annular pack in an embodiment having the half packs electrically connected; 
     FIG. 9 is a schematic of the half packs electrically coupled in series; 
     FIG. 10 is a schematic of the half packs electrically coupled in parallel; 
     FIG. 11 shows an exploded view of the split annular pack with annular or cylindrical cells; 
     FIG. 12 shows a top view of the split annular pack with cylindrical cells electrically coupled in a combination of series and parallel connections; 
     FIG. 13A is a schematic of one half pack shown in FIG. 12; 
     FIG. 13B is a schematic of the other half pack shown in FIG. 12; 
     FIG. 14 shows a top-mounted glass-to-metal seal on a split annular cell; 
     FIG. 15 shows a side-mounted glass-to-metal seal on a split annular cell; 
     FIG. 16 shows a top mounted integral glass seal on a split annular cell; 
     FIG. 17 shows the lid of the split annular cell of FIG. 16; 
     FIG. 18 shows a cross-sectional view of a chamfered glass-to-metal seal; 
     FIG. 19 shows an exploded view of the split annular pack with insulation layers; 
     FIG. 20 shows a cross-sectional internal view of one half of an annular cell with a top-mounted glass-to-metal seal; 
     FIG. 21 shows a cross-sectional internal view of an annular cell with a side-mounted glass-to-metal seal; 
     FIG. 22 shows a cross-sectional view of a split annular cell with a side-mounted glass-to-metal seal; 
     FIG. 23A shows a top view of a hinged split annular cell in an open position; and 
     FIG. 23B shows a top view of a hinged split annular cell in a closed position. 
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings wherein like characters are used for like elements throughout the several views, FIG. 1 illustrates a split annular battery pack assembled on a downhole tool in accordance with an embodiment of the invention. In this particular embodiment, the split annular battery pack is made up of two half packs  10  and  12  held together around downhole tool  14  as described with reference to FIG. 5 below. Tool  14  may be any type of tubular member designed for downhole use. Although two half packs are shown in this embodiment, a split annular pack may be made from three or more elements as well. FIG. 2 shows halves  10  and  12  disassembled and apart from downhole tool  14 . The split battery pack design facilitates replacement of a battery on downhole tools at the job site. The split annular design can be used on any downhole tool including, for example, logging while drilling (“LWD”) tools and measuring while drilling (“MWD”) tools. The design also is applicable to any sized wellbore diameter. 
     In one embodiment, to ensure proper alignment, faces  13  of the split battery pack are provided with alignment mechanisms  24  and respective cut-outs  26  to facilitate alignment of both halves as shown in FIG.  3 . Alignment mechanisms  24  are shown to be rectangular keys, but can take any shape or size as may be required by a given application. FIG. 4 is an exploded view of the embodiment having alignment mechanisms  24  and respective cut-outs  26 . 
     When assembled on a tool, half packs  10  and  12  are secured to each other with four screws (not shown). Two screws engage holes  16  and  18  through cut-outs  20  and  22  on one side as shown in FIG.  5 . The other two screws secure the other side in the same fashion. Inserts  32 , isolating bushings  36  and floating positive and negative terminals  28  are inserted into holes  40  on top of pack half  10 . Similarly, floating positive and negative terminals  30 , inserts  34 , and isolating bushings  38  are inserted into holes  42  on the top of half pack  12 . Holes  40  may be located on the bottom or both the top and bottom of a split battery pack. Holes  42  may be located similarly. If the walls of the housing are thick enough, terminals can be located on the outer diameter (“OD”) or inner diameter (“ID”) of the cell. 
     Alternatively, as shown in FIG. 6, a contact block  21  may be used instead of holes  40 . Contact block  21  is curved so as to fit within a top portion of chamber  11  of half packs  10  and  12 . While only one contact block  21  is shown in the figure, one may be provided in each chamber  11 . Floating positive and negative terminals  28 ,  30 , inserts  32 ,  34  and isolating bushings  36 ,  38  shown in FIG. 5, in the embodiment of FIG. 6 are disposed within holes  23 . Chamber  25  houses a fuse (not shown). Chamber  25  allows the fuse to be more accessible and therefore easier to replace. 
     An epoxy, mechanical mounting, or similar mechanisms may be used to secure the contact block in place. Generally, the contact block will be secured within the chamber so that the top of the contact block is flush with the top of the half pack. If an epoxy is used as the securing mechanism, contact block  21  may be connected to a flat member by screws (not shown) that engage holes  27 . By placing the flat member onto half pack  10  or  12  during the curing of the epoxy, the top of the contact block is certain to be flush with the top of the half pack. FIG. 7 shows a cross sectional view of contact block  21 . As can be seen in FIG. 7, holes  29  provide a path for electrical connections into chamber  23 . Also, holes  27  are provided in both the top and bottom of contact block  21 . 
     Referring to FIG. 8, the half packs can be connected in series or parallel by mounting floating connections along the face  13  of the split section of each half pack  15 ,  17  so that electrical connections are established when the half packs are mated. Floating positive and negative terminals  128  and  130  are located in holes  19  and a complementary hole in half pack  15  (not shown) with inserts  132  and  134  and isolating bushings  136  and  138 . Since both packs are electrically connected, floating positive and negative terminals  30  only need to be included on the top of half pack  17 . As before, the floating terminals alternatively can be located on the bottom or on both the top and the bottom of the split battery pack, if desired. Also, if the housing is thick enough, the terminals can be located on the OD or ID of the cell. FIGS. 9 and 10 show schematics of the battery circuit in series and in parallel respectively. BAT 1  and BAT 2  denote batteries in the respective half packs. CR 1  denotes a diode and F 1  denotes a fuse. In either embodiment, positive terminal P 1  and negative terminal N 1  are electrically coupled to a connector CN 1  compatible with the equipment to be powered. Generally, the connector will consist of a receptacle capable of accepting a plug on electronics being powered. Alternatively, the terminals P 1  and N 1  may be directly electrically coupled with electronic equipment. 
     As shown in FIG. 11, each half pack of the split annular battery pack has an annular chamber  11 . The chamber may be used to house any type of electrical device. In the embodiment shown, half pack  12  is shown to house split annular cells  46 , while half pack  10  houses cylindrical cells  44 . The cylindrical and split annular cells can be connected in series, in parallel, or a combination of both to achieve the desired voltage and capacity required to operate the tool. The cylindrical or split annular cells may be secured in place by means of epoxy or a mechanical means. In embodiments made up of more than two halves, every fractional part of the whole has such an annular chamber. The design of the annular cell allows the number of cells and cell-to-cell connections of a pack to be decreased. Also, the annular cell&#39;s efficient use of the space available inside a pack leads to greater battery capacity. 
     The cells contained within the half pack are electrically connected to the terminals. The cells themselves may be connected to one another in series, parallel or a combination of both series and parallel. FIG. 12 shows view of cylindrical cells B 1 -B 20  electrically connected to one another. Cells B 1 -B 20  are electrically isolated from the half packs  10  and  12  by insulating material  83 . Insulating material  83  will be described with reference to FIG. 19 below. In this embodiment, adjacent cells are connected in series in sets of two. The sets of series connected cells are then connected together in parallel. A diode is placed between the series connected cells and the parallel connection to protect the cells. Finally, the cells are electrically connected to the floating terminals through a fuse. FIGS. 13A and 13B shows a schematic of this embodiment. The ten cells contained within each half pack are denoted by B 1 -B 20  respectively. CR 1  refers to a diode and F 1  refers to a fuse. The selection and purpose of CR 1  and F 1  are well known in the art and may differ given specific applications. Positive terminals P 1 , P 2  and negative terminals N 1 , N 2  may be connected as described above. 
     Referring to FIGS. 14,  15  and  16 , a split annular cell can use a glass-to-metal seal or an integral glass seal that is top-mounted or side-mounted. In any case, the seal may exist on one half as shown or on both halves (not shown) of the split annular cell. FIG. 14 illustrates a top-mounted glass-to-metal seal  66  on split annular cell  65 . 
     The side-mounted glass-to-metal seal, shown in FIG. 15, is implemented due to the need for thin cross-sectional cells. Because the cross-sectional size of the walls of a cell are made thinner, welding a nominal sized glass-to-metal seal onto that cross-section becomes more difficult. This continues to the point where welding a commercially available glass-to-metal seal is impossible. Therefore, the glass-to-metal seals are placed on the OD of the cell can. This allows thin cross-sectional annular cells to be developed for use in downhole tools for use in a range of diameter wellbores. In order to place glass-to-metal seal  66  onto the side of annular cell  65 , a portion  67  of the outer wall is flattened or dented. Portion  67  provides a flat surface on which the glass-to-metal seal can be mounted. Alternatively, the glass to metal seal could be placed on a flattened portion of the ID of the cell can in a similar manner. 
     Referring to FIG. 16, an integral glass seal  69  is shown which does not require the outer metal ring used in the glass-to-metal seal. The integral glass-to-metal seal is disposed within the lid of the split annular cell. Referring to FIG. 17, the process of integrating a glass seal involves cutting or drilling a hole  71  in the lid of the split annular cell  73  and arranging the glass and post in the hole. The assembly is then placed in an oven and fired to fuse the glass and post to the lid of the split annular cell. The above process could also be implemented in an annular cell design. The integral glass seal establishes a reliable top-mount cell connection, alleviates heat distortion caused by laser welding, facilitates easier and quicker assembly, and allows the design and manufacture of thin cross-section annular or split annular cells. 
     Various placements of the glass to metal seal  66  have been discussed in the preceding embodiments. Regardless of placement, the glass to metal seal  66  typically is welded in place using a welding process, for example a laser welding or resistance welding. When the glass to metal seal is welded to the can or one of the lids of a cell, excessive heat may be generated causing undesirable distortion of the seal and/or the cell surface. In addition to distortion, differing thermal expensivity characteristics of the seal and the can surface might result in leakage when excessive heating occurs. To minimize these problems and facilitate attachment of the glass to metal seal  66 , an improved glass to metal seal  66  is illustrated in FIG.  18 . In this seal center post  75  is surrounded by an insulating ring of glass  77 . Disposed about glass ring  77  is a chamfered metal ring  79 . Metal ring  79  may be made of any appropriate metal including, for example, steel. The chamfering of metal ring  79  reduces the actual amount of metal that is being laser welded by roughly two-thirds. Because less metal is being welded, the dwell time required to weld a part is reduced. The reduced dwell time consequently reduces the total heat required for the welding operation, this minimizing the risk of distortion and leakage. 
     Referring to FIG. 19, the cells are electrically connected to the floating terminals in the half pack. At the same time, the cells may be electrically isolated from the half pack. To accomplish this electrical isolation, an insulating material  83  is placed between the cell and the chamber of the pack as shown. Insulating material  83  may completely encapsulate the cell. Any size or shape insulator may be used to separate the cell from the half pack. 
     Several insulation alternatives exist, for example, the housing of the cell may be coated with a high temperature glass tape or non-conductive composite end caps may be used. The non-conductive end caps would fit into the top and bottom of chamber  11 . The insulating material may be a false bottom, i.e., an insulating material poured into the chamber prior to the insertion of the cell. The epoxy securing a cell into chamber  11  may be used to electrically isolate the cell from the half pack. If an aluminum housing is used, another alternative is hard anodizing the housing. Several methods may be used in conjunction. Also, cells may be electrically isolated from one another by an additional insulating material  85 . The placement of insulating layers within the half pack and the electrical connections of the half pack will be determined by application. 
     FIG. 20 illustrates a cross-sectional view of a top-mounted glass-to-metal seal on a split annular cell, such as cell  46  shown in FIG.  11 . The split annular cell has an outer can sleeve  58 , an inner can sleeve  60 , a lower can lid  62 , and an upper can lid  64 . The top-mounted glass-to-metal seal  66  is mounted on upper can lid  64 . Post  75  of the top-mounted glass-to-metal seal  66  passes through a sheet of separator paper  68  and an insulating disk  70  to make contact with tab  72 . Tab  72  passes through a insulating disk  74  and a sheet of separator paper  76  to make contact with screen  78 . In one or more embodiments, tab  72  may be adapted to include a strain relief loop between the insulating disks  70  and  74  as shown. The loop in tab  72  between insulating disks  70  and  74  increases the cell&#39;s ability to perform under downhole conditions. Screen  78  is disposed against carbon cathode  80 . Separator paper  87  is placed on the opposite side of screen  78  from carbon cathode  80 . An electrolyte  81 , e.g., thionyl chloride, fills the interior of the cell. Those skilled in the art will appreciate that other electrolytes are suitable and may also be used. Generally, Teflon is used as an additional insulating material within the cell, for example, insulating disks  70  and  74  may be Teflon disks. Lithium anode  82  is disposed against the outer can sleeve  58  and separated from carbon layer  80  by a sheet of separator paper  84 . An insulating disk  86  is placed between the interior elements of the cell and lower can lid  62 . Finally, internal spring  88  is disposed within the cell to absorb shocks and maintain constant compression on the electrodes without incurring damage to the cell. The use of the internal spring allows the cell to operate at high shock levels, thus allowing the design to be used in hostile downhole environments. The internal spring may be “V” or “C” shaped. It will be understood by those skilled in the art that a “V” shaped spring also encompasses those shapes similar to a “V” shape, for example, “U”, “W”, “M”, “N”, “R”, “Z”, “Y”, “X” shapes, and a “C” shape spring also encompasses those shapes similar to a “C” shape, for example, “O”, “D”, “G”, “J”, “P”, “Q”, “S”, “B”shapes. 
     Alternatively, as shown in FIG. 21, the glass-to-metal seal may be side mounted on the annular cell. In a side-mounted configuration, the glass-to-metal seal  66  is mounted on a flattened portion of outer can  90 . The post of glass-to-metal seal  66  passes through separator paper  92  to contact screen  94 . Adjacent to the opposite side of screen  94  is a layer of lithium  96 . The lithium is isolated from carbon layer  98  by separator paper  92 . Current collector screen  100  is placed between carbon layer  98  and outer can  90 . Spring  102  borders screen  94  on the inner side where the post of glass-to-metal seal  66  makes contact. Spring  102  allows the cell to withstand shock without compromising performance by preventing internal components from moving and being shaken apart. Insulating layer  104  is disposed between spring  102  and inner can  106 . An electrolyte, e.g., thionyl chloride  108 , fills the interior of the cell to facilitate the electrochemical reaction that allows electricity production. 
     The split annular cell design is more economical and reliable to use in that the number of cell-to-cell connections required to obtain the desired capacity of the battery pack is reduced compared to cylindrical cells. At the same time, usage of the thin annular space available in the pack is more efficient than cylindrical cells. In most cases, this efficient use of available space yields higher battery capacity. FIG. 22 shows the internal structure of a split annular cell. In the illustrative embodiment shown, glass-to-metal seal  66  is side-mounted. Again, the glass-to-metal seal  66  is mounted on a flattened portion of outer sleeve  90 . The post of glass-to-metal seal  66  passes through separator paper  110  to screen  112 . Insulating shrink tubing  114  may be used on the connection tab  111  between glass-to-metal seal  66  and screen  112 . Adjacent to the opposite side of screen  112  is a layer of lithium  116 . The lithium is isolated from spring  118  by separator paper  119 . Spring  118  provides radial constraining forces to the cell. Spring  118  may have, for example, a “C” or “V” shape. Screen  120  is placed between carbon layer  122  and separator paper  110 . Insulating end layers  124  are placed in the splits in the annular cell bordered by outer end plates  126 . Insulating disks are also placed on the top and bottom of the cell (not shown). The insulating disks are used to electrically separate components from one another and electrically insulate the anode and cathode from the outer can. In order to withstand shocks and vibrations present during operation, the insulating disks are made to a width of, for example, ten to fifteen thousandths of an inch. At one of the ends a tab  128  is provided against screen  120  to make the positive termination contact to steel can  90 . An electrolyte  115 , e.g., thionyl chloride, is placed throughout the interior of the cell to facilitate the chemical reaction that allows electricity production. All of the above designs are equally applicable to cells with other anodes. Further, certain environments may call for the use of a combination of materials, e.g., a lithium anode with magnesium added. 
     Referring to FIGS. 23A and 23B, in one embodiment, the split half packs  10  and  12  are connected by a hinge  150 . Hinge  150  allows the half pack to be easily placed onto a downhole tool and further makes the battery pack one piece. FIGS. 23A and 23B show the hinged half packs open and closed respectively. 
     The foregoing description has concentrated on battery cells for placement in the chambers of the split annular pack. However, use of the split annular pack is not limited to housing a battery cell. To the contrary, in many applications it would be desirable for the chambers to house various types of electronic circuitry including, for example, control circuitry, data recording circuitry, and electronic sensors. Thus, the term “electrical device” as used herein refers to any type of electrical device that may be housed in the chambers, including but not limited to a battery cell, control circuitry, data recording circuitry, electronic sensors, etc. 
     When electronic devices other than battery cells are housed in the chambers, it is typically desired that they be mounted within the chamber in a secure fashion so as to prevent movement. Secure mounting of the electrical device may be achieved using an adhesive such as epoxy or by mechanical means such as screws or rivets. 
     The invention has many distinct advantages over conventional designs. The annular cell in accordance with an embodiment of the invention can fit in smaller annular widths and yet has a higher capacity than a comparable cylindrical cell of the same OD. The annular shape of a cell in accordance with an embodiment of the invention efficiently fills the annular space available. Split annular and annular cells in accordance with embodiments of the invention require fewer cells for given capacity, which reduces the number of necessary connections. Thus, the reliability of the battery pack is increased. 
     While the invention has been described with respect to a limited number of exemplary embodiments, those skilled in the art will appreciate numerous variations therefrom without departing from the spirit and scope of the invention. For example, while the exemplary electrode configuration is depicted in anode-cathode (“AC”) form, the invention is equally applicable to a plurality of anode and cathode configurations or a spiral wrap. Also, in the above configuration, the post of the glass-to-metal seal is at a positive potential and the walls of the cell are at a negative potential (as shown in FIG.  20 ). This configuration may be reversed to place the walls of the cell at a positive potential and the post of the glass-to-metal seal at a negative potential (as shown in FIGS.  21  &amp;  22 ). Further, it is to be understood that in any of the various embodiments any one or more of the segments may house types of electrical devices; including, but not limited to a power source, circuitry, or a sensor. Thus, the disclosed embodiments are for purposes of explanation and example only; the scope of the invention being defined solely by the appended claims.