Abstract:
There is disclosed a battery system to be used in downhole application. The battery system provides energy to operate the measurement devices associated with drilling. The system includes a plurality of cells, each comprising an electrically insulating mandrel which is shaped to fit over an inner tube, and a combination of an anode, a cathode and a solid polymer electrolyte, all disposed over the mandrel. The individual cells are mounted end to end and are interlocked together to prevent rotation of the cells relative to one another. The cells are electrically connected together and they are all mounted between an inner and an outer tube.

Description:
BACKGROUND OF INVENTION 
     a) Field of the Invention 
     This invention relates to a high temperature solid state hollow cylindrical rechargeable battery. More particularly, the present invention is concerned with a high temperature rechargeable lithium battery system for downhole application, such as oil and gas well logging and drilling. Still more specifically, the present invention is directed to a battery system for well logging and drilling apparatuses which can be operated even at temperatures up to 125° C. and higher for extended periods of time. 
     b) Description of Prior Art 
     In oil well logging and drilling operations, primary lithium batteries such as those based on a liquid thionyl chloride electrolyte have been used to power monitoring systems to collect information such as pressure, temperature, stress, magnetic field, and the like during the drilling operation. Although these batteries have excellent energy density (typically in the range of 900 Wh/L), the task of replacing them is relatively time consuming as compared to the usable life time of the batteries. For example, a typical liquid thionyl chloride battery used in oil drilling has about 70 hours of usable operating capacity, because it is a primary cell, only about 75% of its full capacity is used to avoid facing premature battery end of life condition during a drilling mission. Furthermore, it will be noted that the operation of replacing a battery requires approximately three days. 
     It will be realized that from the standpoint of operation and cost, an obvious solution to the problem of having to frequently replace the battery would be to use a rechargeable battery. However, to Applicant&#39;s knowledge, high temperature rechargeable batteries for liquid or gel electrolyte systems are not presently available to achieve the above goal, unless they are provided with sufficient cooling device. Of course this is not possible nor economical in a drilling environment. 
     In spite of the other defects of liquid electrolyte batteries, in the context of a well logging and drilling operation, it will be obvious to one skilled in the art that, unless liquid electrolyte cells are assembled each in their own containers, it is not possible to mount them in series in a single container, which is highly desirable in well logging and drilling operations. 
     A review of the prior art does not seem to provide an answer to the problems outlined above. Of course, rechargeable solid polymer electrolyte batteries have been known for a number of years, and have been developed especially because they are highly rechargeable and do not have the known disadvantages of liquid electrolyte batteries. Since liquid electrolyte batteries have to be discarded after discharge in well logging and drilling operations, and because the batteries contemplated should be hollow cylindrical. U.S. Pat. Nos. 3,023,260, 4,262,064 and 4,937,154 have to be discarded as not being adaptable for the contemplated use. On the other hand, U.S. Pat. No. 5,571,632 discloses a cylindrical non aqueous electrolyte cell which is mostly characterized by the sealing means disposed at the ends of the battery. This battery does not provide an answer to the need of arranging a stack of batteries which are fixed relative to one another and operate together as a single battery container. 
     It is an object of the present invention to provide a solid polymer battery with a design suitable for oil and gas well logging and drilling application. 
     It is another object of the invention to provide a solid state battery for downhole application which can be operated even at temperatures of up to about 125° C. for long periods of time. 
     It is another object of the present invention to provide a hollow cylindrical shaped solid polymer electrolyte battery which is made of a plurality of cells, each being laminated in a hollow cylindrical design. 
     It is another object of the present invention to provide a solid polymer electrolyte battery which is rechargeable and consequently can be used repeatedly in an oil well drilling environment for extended periods of time without the need to remove it from the ground. 
     It is another object of the present invention to provide a rechargeable solid polymer electrolyte battery that can be situated within a space provided between an inner tube and an outer tube, and to use the inner space for communication and power input wiring. 
     is another object of the present invention to provide a battery system wherein individual cells thereof do not require to be placed in individual containers. 
     It is another object of the present invention to provide a solid state battery system for downhole application that can be assembled in almost any desired shape within a drilling equipment, because of its thin solid film laminate construction. 
     It is another object of the present invention to provide a battery system which enables heat generated therein to dissipate through the inner and outer tubes between which the cells are mounted, while maintaining an uninterrupted operation. 
     It is another object of the present invention to provide a battery system wherein individual cells are interlocked to prevent their rotation relative to one another. 
     It is another object of the present invention to provide a battery system which incorporates removable and replaceable venting devices and especially adapted terminals. 
     SUMMARY OF INVENTION 
     These and other objects of the present invention may be achieved in a battery system to be used in downhole application, having measurement means, the battery system being adapted for providing energy to operate said measurement means. The battery system comprises 
     a plurality of solid polymer electrolyte cells, 
     each cell comprising 
     an electrically insulating mandrel shaped to slidably fit over an inner tube, 
     a combination of an anode, a cathode and a solid polymer electrolyte disposed over the inner tube, 
     means for mounting the plurality of solid polymer electrolyte cells end to end, 
     means for interlocking same together so as to prevent rotation thereof relative to one another, 
     means for electrically connecting the plurality of cells, and 
     an outer tube of heat dissipating material to mount the plurality of cells therein to constitute the battery system. 
     The anode, cathode, polymer electrolyte combination may be disposed over the mandrel in a jelly roll design, in a flat roll design, or in a flat stack design, 
     The inner and outer tubes are preferably made of heat dissipating material such as stainless steel, and the mandrel is preferable made of anodized aluminum, although any other suitable material may be used. 
     In accordance with a preferred embodiment of the invention, each mandrel is formed with a partial flange at one end thereof, and a complementary flange at the other end thereof, and these flanges are arranged so that when one cell is joined to another similar cell the partial flange of one cell and the complementary flange of the another cell constitute a continuous interlocking flange. The partial and complementary flanges are suitably of the same dimensions. 
     In accordance with another preferred embodiment, the battery system according to the invention comprises a ring fixedly mounted over the continuous interlocking flange, and means are provided to insulate the ring from two thereby interconnected cells 
     The ring preferably is size adjustable, and means are provided to tighten the ring over the interlocking flange. For example, the ring is made size adjustable by providing a radial discontinuity therein to form mating ends. In addition, the ring may have tangential bores formed at the mating ends and a tensioning screw may be disposed through the bores to tighten the ring against the continuous interlocking flange. 
     The ring may also comprise radial threaded bores formed therein, radial holes formed in the partial and complementary flanges opposite the radial bores and set screws are then used to extend through the radial threaded bores into the holes to further prevent rotation of the plurality of batteries relative to one another. 
     An end cap may be mounted at both free ends of the battery system; between the inner and outer tubes. Also foam insulating washers may be mounted on both sides of the ring between the ring and two adjoining cells. 
     The preferred means for electrically connecting the plurality of cells comprise cell connection insulated tabs electrically disposed between two adjoining cells. For that purpose, slots are formed in the ring, the tabs then extending from one cell to the next one through the slots. 
     According to another preferred embodiment, at least one safety vent is provided on at least one end cap, to permit purging of the battery system and escape of gases therefrom in case of undesirable pressure increase. This may be achieved by providing at least one vent opening in at least one end cap, and threaded means are provided to enable to screw the vent into the end cap. 
     According to the invention, the vent may include a rupture disc which is adapted to a maximum predetermined pressure to be maintained in the battery system. In detail, such a vent may comprise a threaded member adapted to be screwed at one end into the above threaded means of the end cap, and there is provided a disc holding member which is formed with a collar and which is screwable at the other end of the threaded member, a first O-ring disposed between the threaded member and the entrance to the vent opening, the rupture disc thereby being held against the collar, and a second O-ring is provided between the rupture disc and said threaded member. 
     In accordance with yet another embodiment, the battery system according to the invention comprises terminal openings formed in the end caps, and one positive and one negative terminal are disposed in respective terminal openings. Preferably, the terminals are made of copper and an insulating lining material such as polypropylene is disposed in the respective openings to isolate the terminals from the material of the respective end cap. The terminals can also be made of other metals sealed in glass to insulate them from the body of the end cap. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     The above and further objects and advantages of the present invention will be apparent to one skilled in the art from the following detailed description of a preferred embodiment given by way of illustration but without limitation, in which 
     FIG. 1 is a schematic exploded view of a battery system according to the invention; 
     FIG. 2 is a schematic illustration is longitudinal cross-section of the battery system illustrated in FIG. 1; 
     FIG. 3 is a perspective view of a battery unit which is part of a battery system according to the invention, including an interlocking ring and an insulating foam washer; 
     FIG. 4 is a partial cross-section view of a battery system according to the invention prior to interconnecting the battery units; 
     FIG. 5 is another partial cross-section view of a battery system according to the invention showing the outer container in part and the end caps; 
     FIG. 6 is a cross-section view through one end cap and vent mounted thereon; 
     FIG. 7 is a cross-section view of a terminal mounted in one end cap; 
     FIG. 8 is a schematic view of a solid lithium polymer battery arranged in a jelly roll design; 
     FIG. 9 shows a flat roll design; 
     FIG. 10 shows a flat stack design; 
     FIG. 11 is a schematic illustration of a drilling rod used for well logging application, provided with a battery system according to the invention; and 
     FIG. 12 is a cross-section view of an interconnecting ring. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     Referring to the drawings, it will generally be seen that the battery system illustrated in FIG. 1 is made of a plurality of battery units  1  all interconnected by means of interconnecting rings  3  as shown schematically in the exploded view of FIG.  1 . The battery system  5  is illustrated in longitudinal cross-section in FIG.  2 . 
     Referring to the drawings, more particularly FIGS. 2 and 5, it will be seen that the most prominent feature of battery system  5  according to the invention is the fact that a plurality of cells or battery units  1 , here twelve in number, although this number can vary to a large extent, are connected in series while being mounted over inner tube  6  in one single battery containers, here outer tube  7 . Battery system  5  is closed at both ends by means of hollow end caps  9 ,  11  (FIG.  2 ). Each cell  1  being hollow cylindrical or tubular as shown, more particularly in FIG. 3, once connected together as will be discussed in detail hereinafter, they form a continuous mandrel  13 , as particularly shown in FIGS. 1,  2  and  5 . Both inner and outer tubes  6  and  7  are welded to hollow end caps at both ends of the battery system during assembly. 
     For more detail of a cell or battery unit  1  according to the invention, reference will now be made to FIGS. 3 and 4. The cellular part of the battery has been schematically illustrated and consists of a jelly roll design (shown for example in FIG. 8) which consists of a solid polymer electrolyte lithium battery which is well known to those skilled in the art. This electrochemical generator will generally be referred to by reference numeral  15 , and consists in known manner of a lithium anode, a V0 x  based cathode placed on inert plastic material, a polymer electrolyte and a current collector all in sheet forms and rolled together as schematically illustrated in FIG. 8 Of course, any other arrangement of electrochemical generator, for example the one illustrated in FIGS. 9 and 10 could also be utilized, although it has been found more practical to produce a hollow cylinder shaped battery merely by winding the sheet components of the electrochemical generator around an inner tube  13 . Other cell designs (FIGS. 9 and 10) can of course be shaped into a tube, however this procedure would involve more technical problems. The present battery unit is therefore based on a jelly roll design. 
     Referring again to FIGS. 3 and 4, for a detailed description of battery unit  1 , it will be seen that each unit comprises mandrel  13  made of electrically insulating and heat dissipating material, here anodized aluminum, and the electrochemical generator  15  is wound around this mandrel as shown. Mandrel  13  is formed with a partial flange  19  at one end and a complementary flange  21  at the other end. Usually, the two flanges are of similar dimension and in the illustrated embodiment they are both exactly half circular, so that when one cell unit is joined to another similar cell  1 , partial flange  19  of the first cell and complementary flange  21  of the other cell will constitute a continuous interlocking flange  23  as particularly shown in FIG.  5 . 
     To constitute a unitary battery system, a plurality of cells  1  are joined together as will now be discussed in detail. This is made possible by providing a plurality of stiffening rings  25  and insulating foam washers  27 ,  29 . In other words, when joined together two similar cells  1  will mate by having partial flange  19  and complementary flange  21  joined to form complementary interlocking flange  23 . The latter is maintained fixed by having ring  25  fixedly mounted thereon with insulating foam washers  27 ,  29  placed on either side of ring  25  to insulate the latter from the two adjoining batteries  1 . It should be remembered that once fixed together as indicated above, the two connected cells should be completely fixed relative to one another so that once the twelve units are assembled as indicated, the battery system forms an assembly wherein all the parts are fixed relative to one another. In other words, while the battery system may rotate as a whole, the different cells cannot rotate individually relative to one another. 
     This is made possible by a special construction of interlocking ring  25  and providing fixing holes  31 ,  33  respectively in flanges  19  and  21 . As illustrated, stiffening ring  25  is rectangular in cross-section, and in order to be size adjustable for enabling it to be tightened over interlocked flanges  19 ,  23  the stiffening ring is provided with a slit  35  forming a discontinuity which defines two mating ends  37 ,  39 . It will be obvious to one skilled in the art that by urging mating ends  37 ,  39  towards one another, ring  25  will press against flanges  19 ,  21 . To achieve this, tangential bores  41 ,  43  are formed respectively at mating ends  37 ,  39 , bore  41  being larger in diameter than bore  43  to accommodate tensioning screw  44  which is adapted to be disposed through bores  41 ,  43  to tighten the ring against interlocked flanges  19 ,  21  thereby fixing two adjacent battery units together. To further accommodate the tensioning screw, bore  41  is preceded by a recess  45  of larger diameter than bore  41  and defining a collar  47  against which the head of the tensioning screw comes to rest. Of course a thread  49  is formed in bore  43  into which the tensioning screw is engaged (FIG.  12 ). 
     Referring more particularly to FIGS. 3,  4  and  12 , it will be noted that ring  25  additionally comprises threaded radial bores  51 ,  53  which are designed to be opposite fixing holes  31 ,  33  when the ring is properly engaged over the interlocked flanges  19 ,  21 . Set screws (not shown) extend through threaded radial bores  51 ,  53  into fixing holes  31 ,  33  to further assist in preventing any rotation of adjacent battery units  1 , relative to one another or sliding at the ring along the mandrels. Finally, for a reason that will be explained below, there is provided a rectangular depression  55  (FIG. 12) in the inner face of the ring preferably located diametrically opposite slit  35 , in the embodiment which has been illustrated, although this positon may vary as one skilled in the art will appreciate. Similar depressions  55 a are also formed in foam washers  27 ,  29 , and for the same reason. 
     Of course, when the cell units have been joined together by means of a plurality of rings  25  (the latter being isolated by means of insulating foam washers  27 ,  29  respectively disposed between rings  25  and two adjacent cell units) the units must be electrically connected together. This is made possible by providing a cell connection tab  57  of reversed U construction, as shown, although any other type of cell connection may be used as will be appreciated by those skilled in the art. As illustrated, cell connection tab  57  extends under washers  27  and  29  and ring  25 , particularly through depression  55 , where it comes to rest against the other end of an adjacent cell unit as particularly shown in FIG.  5 . The assembly of cell units connected together as previously indicated is placed in an outer tube  7 , which is made of heat dissipating material, such as stainless steel. The battery system is closed at both ends by means of hollow end caps  9 ,  11 , each having safety vents  65  mounted therein. Additionally, positive and negative terminals  67 ,  69  are mounted in one of the two caps, here cap  9 . As will be obvious to one skilled in the art, the vents are used to permit purging of the battery system, preferably when assembling it, and also to enable the escape of gases therefrom in case of undesirable pressure increase inside the battery system. 
     For a detailed description of a vent  65 , reference will be made particularly to FIG.  6 . To accommodate vent  65 , it is first necessary to provide a thread opening  71  in end cap  9 , wherein vent  65  is screwed as shown. The body of vent  65  consists of threaded member  73  which is shaped to be screwed at one end into threaded opening  71 , a rupture disc  75 , a disc holding member  77  and two O-rings  79 ,  81  which serve to perfectly seal the vent. Since there is a large selection of rupture discs available, they provide a wide choice of venting pressures under which vent  65  should operate. 
     Finally, as indicated, positive and negative terminals  67 ,  69  are mounted in end cap  9 . For a detailed construction of a terminal according to the invention reference will now be made to FIG. 7 of the drawings. In a suitable location of the end cap a terminal hole  87  is formed. To isolate the metal terminal from the end cap, an insulating polymer member  89  is placed into hole  87  as shown. The terminal itself is fixed into hole  87 , by means of fixing washer  91 . 
     In operation, the battery according to the invention is mounted in a drilling assembly schematically illustrated in FIG. 11 of the drawings in a space provided between two concentrically located pipes  93 ,  95 . This arrangement becomes particularly significant when one considers the heat management aspect of the battery according to the invention under abusive conditions. In addition, the open space at the center of a battery according to the invention enables to place communication cables with other devices used in downhole assemblies. The open space may also be used to mount other devices within the overall space of the battery. 
     Another advantage of the battery according to the invention results from the fact that the parts do not move relative to one another. This is particularly important in MWD (measurement while drilling) application in which the entire battery rotates together with the drill bit. The relative rotation of one cell in relation to the neighboring cell has caused many problems with primary batteries in the past since this leads to the breaking of the interconnection tabs. With the battery according to the invention, the interconnecting tabs remain unaffected. 
     Although this invention has been described with reference to one particular embodiment it is understood that modifications are possible without departing from the spirit and scope of the invention.