Abstract:
A battery for downhole use configured for fluid-based replenishment. The battery may include separate anode and cathode fluid tanks which may be refilled at various times throughout the life of the well. Upon coupling of a replenishment tool to the battery, it may be fully replenished in a matter of minutes. Further, the nature of the fluid tanks allows for decreased battery bulk in even as increase power and life are afforded due to overall tank volume. Thus, with minimal total intervention time, extended life and replenishable character may be achieved for a battery well suited for use in downhole environments.

Description:
BACKGROUND 
       [0001]    Exploring, drilling and completing hydrocarbon and other wells are generally complicated, time consuming and ultimately very expensive endeavors. In recognition of these expenses, added emphasis has been placed on efficiencies associated with well completions and maintenance over the life of the well. Over the years, ever increasing well depths and sophisticated architecture have made reductions in time and effort spent in completions and maintenance operations of even greater focus. 
         [0002]    In terms of architecture, a well often includes a variety of lateral legs emerging from a main bore. For example, the terminal end of a cased well often extends into an open-hole region branching out into multiple lateral legs providing reservoir access. Of course, such open-hole lateral legs are also often found extending from other regions of the main bore as well. This type of architecture may enhance access to the reservoir, for example, where the reservoir is substantially compartmentalized. Regardless, such open-hole lateral leg sections often present their own particular challenges when it comes to completions installation and maintenance. 
         [0003]    Similarly, another layer of well architecture sophistication may be provided through zonal isolation at various well locations. So, for example, the well may be effectively divided into different perforated production zones or regions based on overall well depth, lateral leg location or other factors. Regardless, production tubing may traverse the well through the various zones which are in turn annularly isolated from one another by packers or other isolating features. Thus, production from any particular zone may be regulated based on whether or not fluid access to the production tubing is provided at the zone. 
         [0004]    Depending on the nature of the zonal isolation and hardware, the noted production at any given zone may be selectively determined. For example, sliding sleeves may be provided at the production tubing of each zone. Thus, production from the zone may be altered over the life of the well as the production profile changes. Indeed, this same type of concept may be employed with sliding sleeves located directly at perforated casing regions even without the use of packer-based zonal isolation or separate production tubing. 
         [0005]    To avoid running a separate costly intervention dedicated to opening and closing sliding sleeves as described above, a dedicated power source such as a lithium ion battery may be positioned downhole as part of the permanently installed hardware. Thus, an operator may transmit a signal through the well from the oilfield surface so as to direct opening and closing of such sliding sleeves. Indeed, this same concept may be employed for a host of different downhole maneuvers set to take place over the life of the well. For example, downhole flow-control, data acquisitions, actuator triggering and a host of other maneuvers may be powered by a downhole permanently installed battery configured for use over a potentially extended period of time. 
         [0006]    Unfortunately, current downhole battery life is relatively limited. For example, a conventional downhole lithium ion battery capable of such use is unlikely to survive for a period exceeding about 3-5 years in the well. Thus, such batteries may be largely ineffective as a power source for intelligent production, where parameters of fluid uptake from various well regions is sought to be modified over the more extended life of the well. More specifically, intelligent production that involves sliding a sleeve open or closed ten years into the life of the well will most likely require a shut down in well operations followed by an interventional application directed at the sleeve. 
         [0007]    Efforts to extend the life of the battery may be undertaken. However, basic physics in terms of the conventional cathode/anode structural relationship render diminishing returns for such efforts, particularly in the downhole environment. For example, the relationship between power storage and density of these components is such that significant increases in size may yield slightly moderate increases in battery life. Further, the size increase results in a package of substantial bulk that may not be tailored down to narrower profiles due to geometric requirements of the noted cathode/anode component relationship. This may be particularly problematic in the limited space of the downhole environment where any increase in bulk creates added challenges. 
         [0008]    In theory, however, drawbacks associated with limited battery life may alternatively be addressed by battery replacement and/or recharging. That is, as opposed to waiting to run a dedicated intervention to shift a sleeve open or closed at a potentially inopportune time, a battery change-out or recharge may be attempted at another time. For example, a change-out or recharge may be performed in conjunction with other downhole interventions undertaken throughout the life of the well. Thus, dedicated battery power for performing certain downhole applications may be supplied at the outset of hardware installations and re-supplied whenever any subsequent intervention is undertaken. 
         [0009]    Unfortunately, battery change-out and/or recharge is largely impractical in the downhole environment. For example, due to limited space, a battery change-out would require an intervention that employs advanced robotics or other currently unavailable change-out system. Similarly, setting aside the added expense of rechargeable batteries, the recharge itself, through a hard-wired, contact based coupling tool, would likely take several hours to a day&#39;s worth of time to complete. Therefore, as a practical matter, operators are generally left a downhole battery of limited life that is later replaced by costly and untimely interventional applications dedicated to performing tasks no longer powered by the now dead battery. 
       SUMMARY 
       [0010]    A downhole battery is provided for substantially permanent placement at a location in a well. The battery includes separate refillable anode and cathode fluid tanks along with a reaction chamber. The reaction chamber is in fluid communication with the tanks and configured to supply power for a downhole application in the well. In one method, a battery media tool is delivered to the location of the battery and utilized in replacing the anode and cathode fluid. Of course, this summary is provided to introduce a selection of concepts that are further described below and is not intended as an aid in limiting the scope of the claimed subject matter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a side sectional view of an embodiment of a downhole replenishable battery assembly. 
           [0012]      FIG. 2  is an overview of an oilfield with a well accommodating multiple of the battery assemblies of  FIG. 1 . 
           [0013]      FIG. 3  is a side partially sectional view of an embodiment of a battery replenishment tool for coupling to the battery of  FIG. 1 . 
           [0014]      FIG. 4  is an enlarged view of the tool of  FIG. 3  revealing wet-mate flow path coupling for fluid replenishment of the battery of  FIG. 1 . 
           [0015]      FIG. 5  is a flow-chart summarizing an embodiment of employing a downhole replenishable battery assembly. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Embodiments are described with reference to certain downhole architecture and applications. For example, embodiments herein are detailed with reference to a downhole architecture and assembly that allow for zonally isolated production. Indeed, the production is dynamic in that downhole power is provided on a near permanent basis such that a changing production profile over time may be responsively addressed. That is, sliding sleeves in different downhole isolated zones may be shifted open or closed depending on the nature of the changing production profile. However, such power requirements may be met in a manner capable of addressing a variety of other downhole applications. For example, long term sensors, electrical submersible pumps and any number of valve or other actuators may be powered by embodiments of downhole replinishable batteries as detailed herein. Regardless, embodiments described herein include a downhole replenishable battery that utilizes separate fluidly refillable anode and cathode tanks adjacent a reaction chamber. Thus, downhole power requirements may be met in a manner less constrained by conventional anode cathode architectural limitations. 
         [0017]    Referring now to  FIG. 1 , a side sectional view of an embodiment of a downhole replenishable battery assembly  100  is shown. The assembly  100  includes a battery  105  with separate anode  129  and cathode  127  fluid tanks. As detailed further below, separate anode and cathode fluids may be circulated in and out of the tanks  127 ,  129 . Thus, an adjacent reaction chamber  175  may be supplied for obtaining electrical output from membrane segregated voids  177 . Similarly, fluid spent in the process of such electrical generation may be circulated back to the tanks  127 ,  129  from the chamber  175  for later replenishment as also detailed further below. 
         [0018]    The battery  105  is shown incorporated into a wall of downhole production tubing  185 . As such, applications involving the tubing  185  or other adjacent well architecture may be powered by the battery  105 . However, the battery  105  may be located in a variety of different downhole locations, whether incorporated with tubing or other types of hardware. 
         [0019]    Once more, the architecture of the battery  105  itself may take a variety of different forms. That is, due to the fluidly circulating and replenishable nature of the battery  105 , the dimensions of the reaction chamber  175  need not be structurally tied to the size of the noted tanks  127 ,  129 . In fact, the tanks  127 ,  129  may be increased or elongated to any practical volumetric size without effect on the dimensions of the chamber  175 . Thus, to a large extent, the overall shape of the battery  105  may be largely determined irrespective of power requirements or intended life expectancy. 
         [0020]    With a greater degree of morphological flexibility available, operators may more freely configure the battery  105  with downhole placement and positioning in mind. Stated another way, as energy requirements increase, tanks  127 ,  129  may be elongated without a commensurate requirement of increasing the overall bulk of the reaction chamber  175 . The fluid replenishment nature of the battery  105  affords more streamlined, lower profile morphologies, particularly advantageous for increased energy requirements in downhole environments. 
         [0021]    Continuing with reference to  FIG. 1 , the noted circulation of fluids within the battery  105  is driven by pumps  150 ,  155  located in fluid communication with the tanks  127 ,  129  and the reaction chamber  175 . More specifically, an anode pump  155  may be utilized to direct fluid from the anode tank  129  into certain membrane segregated voids  177  of the reaction chamber  175 . Similarly, a cathode pump  150  may be utilized to direct fluid from the cathode tank  127  into other segregated voids  177  of the chamber  175 . Further, this pump-assisted fluid direction ultimately results in voids  177  of alternating fluid types, an adjacently repeating fluid sandwich of anode, then cathode, then anode fluid material. In this manner, enhanced surface area interfacing is provided for electrically generating fluid reaction between the different anode and cathode fluids. This is achieved in a manner that also allows for the morphological advantages of the battery  105  as noted above. 
         [0022]    Positive  160  and negative  165  charge plates may be coupled to the chamber  175  as a manner by which to take electrical advantage of the above indicated reactions. Once more, spent cathode and anode fluid may continue circulation through return lines  140 ,  145 , respectively. In the embodiment shown, check valves  130 ,  135  are provided so as to govern the return of spent fluid from the lines  140 ,  145 . That is, such fluid may be returned to the tanks  129 ,  127  or directed toward a sealable outlet  195  as detailed further below. Further, new fluids may be delivered to replenish the tanks  127 ,  129  via delivery lines  152 ,  157  as also detailed further below. 
         [0023]    Continuing with reference to  FIG. 1 , with added reference to  FIG. 3 , access to the sealable outlet  195  may be governed by a shiftable seal  197  disposed at a recess  190  of the tubing  185 . Thus, as also detailed further below, a battery replenishment tool  300  may be delivered through the channel  180  of the tubing  185  for shifting open of the seal  197  and circulating out spent fluids and delivering new fluids to the assembly  100 . 
         [0024]    Referring now to  FIG. 2 , an overview of an oilfield  200  is shown with a well  280  accommodating multiple battery assemblies  100  of the  FIG. 1  variety. In the embodiment shown, the battery assemblies  100  are utilized for opening and closing sliding sleeves  250  of the production tubing  185  in various isolated zones of the well  280 . That is, power for opening and closing the sliding sleeves  250  is independently provided at each isolated zone as a manner of governing production, for example, as the production profile of the well  280  changes over time. This manner of utilizing the assemblies  100  to provide independent power within each isolated zone avoids the need for running a power cable or interventional application from surface so as to shift each sleeve  250 . Of course, power supply advantages afforded by the assemblies  100  may be available for any number of downhole actuations, monitoring or other applications as well. 
         [0025]    Continuing with reference to  FIG. 2 , the exemplary downhole architecture and techniques for taking advantage of replenishable battery assemblies  100  is described in further detail. Namely, the production tubing  185  and well  280  traverse various formation layers  290 ,  295  in reaching a host of production regions  210 ,  220 ,  230 ,  240 . In the embodiment shown, these regions  210 ,  220 ,  230 ,  240  each include perforations  285  into the adjacent formation  295  as a manner of enhancing hydrocarbon production  287  therefrom. 
         [0026]    While the production tubing  185  traverses the entire well  280 , zonal isolation is provided by packers  260 , disposed in the annulus about the tubing  185  for defining each region  210 ,  220 ,  230 ,  240 . Thus, production into the tubing  285  may be independently governed at each region  210 ,  220 ,  230 ,  240 . More specifically, the position of a sleeve  250  disposed at the production tubing  185  of each region  210 ,  220 ,  230 ,  240  may be used to determine whether or not the uptake of fluid production  287  takes place at the given region  210 ,  220 ,  230 ,  240 . So, for example, in the embodiment depicted, fluid production  287  into the tubing  185  is prevented from taking place in the most terminal region  240  but allowed to take place in each of the others  210 ,  220 ,  230 . This is due to the closed position of the sleeve  250  in the terminal region  240 , for example, in response to water or other undesirable production thereat. 
         [0027]    The sleeve positioning for governing production as detailed above may be powered by the battery assemblies  100  of each region  210 ,  220 ,  230 ,  240 . Once more, these assemblies  100  may be utilized for powering a whole range of additional or different applications. For example, in one embodiment, sensors associated with the downhole hardware may acquire region specific data such as pressure, temperature, flow and other profile information. The acquisition, storage, processing and/or relay of such data to surface equipment  201  may be powered by the available battery assemblies  100 . 
         [0028]    Continuing with reference to  FIG. 2 , a control unit  275  is shown disposed at the oilfield surface  200  adjacent the well head  277 . The unit  275  may be utilized for directing a host of downhole applications, perhaps even including the region specific opening and closing of the sleeves  250  as detailed above. Thus, the character of production fluid uptake  287  to the production line  279  may be ensured and/or enhanced over time, as the profile of the well  280  changes. 
         [0029]    Referring now to  FIG. 3 , with added reference to  FIG. 1 , a side partially sectional view of an embodiment of a battery replenishment tool  300  is shown. The tool  300  is configured for physically coupling to the battery assembly  100  so as to circulate new cathode  353  and anode  358  fluids into the battery tanks  129 ,  127 . Similarly, spent cathode  341  and anode  346  fluids may be simultaneously recovered from the assembly  100 . Thus, a true replenishment of battery capacity may be provided. 
         [0030]    With added reference to  FIG. 2 , the tool  300  is shown secured to coiled tubing  310  via a conventional coupling  315 . Thus, a suitable manner for delivery of the tool  300  to downhole locations in a horizontal section of a well  280  may be provided. In the coiled tubing embodiment shown, the tool  300  includes a central passage  380  to allow for the other, possibly unrelated, fluid-based applications to also take place during battery replenishment as described below. Of course, in other embodiments, other types of conveyances may be utilized such as wireline or slickline, particularly where the well  280  is vertical in nature 
         [0031]    Continuing with reference to  FIG. 3  and added reference to  FIG. 1 , the tool  300  is made up of various sections between the noted coupling  315  and the mating section  375  of the tool  300 . Namely, a tool power source  320  and pump  325  are provided to drive the above noted circulation. Of course, given the temporary interventional nature of the tool  300 , the power source  320  may not necessarily be rechargeable or ‘replenishable’ as detailed herein. Indeed, a conventional lithium ion battery or other suitable downhole battery may suffice. 
         [0032]    Additionally, mobile containers  350 ,  360  filled with new cathode  353  and anode  358  fluids are incorporated into the tool  300 . In fact, the spent fluids  341 ,  346  may be drawn into the containers  350 ,  360  via tool intake lines  340 ,  345  in conjunction with the same circulation that delivers the new fluids  353 ,  358  to the assembly  100  via output lines  352 ,  357 . With added reference to  FIG. 1 , this circulation takes place upon the shifting open of the seal  197  by a shifting extension  377  of the tool  300 . 
         [0033]    A closer examination of this circulation and the ‘wet’ mating of the tool  300  to the assembly  100  is described and depicted with reference to the enlarged view of  FIG. 4  detailed below. Once more, the manner and rates of circulation, types of materials constituting the anode  346 ,  358  and cathode  341 ,  353  fluids and other battery-specific details may be akin to those described in  Semi - Solid Lithium Rechargeable Flow Battery , Duduta et al., Advanced Energy Materials Vol. 1, 2011, incorporated by reference herein in its entirety. 
         [0034]    Referring now to  FIG. 4 , an enlarged view of the tool  300  is shown revealing wet-mate flow path coupling for fluid replenishment of the battery assembly  100 . More specifically, coupling of the tool  300  and assembly  100  is initiated by the shifting open of the seal  197  and the alignment of intake  340 ,  345  and return  140 ,  145  lines with one another. Similarly, the output  352 ,  357  and delivery  152 ,  157  lines are aligned with one another. This mating for the described circulation may take place with assembly  450  and tool  475  seals aligning and adjacently defining flow paths for each line connection. 
         [0035]    With the above noted alignment achieved, spent cathode  341  and anode fluids  346  may be routed out of the assembly  100  and into the mating section  375  of the tool  300  as alluded to above. As also indicated above, this circulation may also include the simultaneous delivery of new cathode  353  and anode  358  fluids from containers  350 ,  360  of the tool  300  to the assembly  100  (see  FIG. 3 ). 
         [0036]    Continuing with reference to  FIG. 4 , the circulating anode fluids  346 ,  358  may include anode particles suspended in electrolyte whereas the circulating cathode fluids  341 ,  353  accordingly include cathode particles suspended in electrolyte. Thus, the assembly  100  may be referred to as a semi-solid flow battery assembly  100 . More specifically, in one embodiment, the cathode fluids  341 ,  353  include a lithium nickel manganese oxide or other suitable lithium-based material. Further, the anode fluids  346 ,  358  may include a lithium titanium oxide or other suitable lithium-based material. In still other embodiments, a variety of different types of cathode and anode materials may be suspended in electrolyte, perhaps as powders providing solids content ranging between about 40-60% depending on the nature of the formulation. Of course, other formulation percentages may also be utilized. 
         [0037]    The described circulation of fluids  341 ,  346 ,  353 ,  358  may proceed at any number of practical replenishment rates. For example, in one embodiment, a replenishment cycling in and out of the various new  353 ,  358  and spent  341 ,  346  fluids may take place at between about 10 to 30 ml per minute. Thus, depending on the particular size of the battery tanks  127 ,  129 , the overall duration of replenishment is likely to take place in well under an hour, likely over the course of a matter of minutes. This is in sharp contrast to conventional hard-wire contact based, electrical battery recharge, which may take hours to achieve in circumstances where the battery is to provide any substantial degree of power. Therefore, in the context of a downhole environment, where reduction in intervention time may be of substantial benefit, replenishment as described may be particularly advantageous. 
         [0038]    Referring now to  FIG. 5 , a flow-chart summarizing an embodiment of employing a downhole replenishable battery assembly is depicted. Namely, the battery assembly may be disposed at a downhole well location on a near permanent basis to provide power for any number of downhole applications as detailed above. However, as power is drained over time, a battery fluid replenishment tool may be deployed into the well as indicated at  515 . Upon advancement to the assembly, the tool may be fluidly coupled thereto as noted at  530 . Thus, new or ‘unspent’ anode and cathode fluids may be circulated into the assembly from the tool (see  545 ,  560 ). Indeed, at this same time, the spent anode and cathode fluids may be circulated out of the assembly, for example, back into the tool for removal from the well. 
         [0039]    With the battery assembly replenished, the tool, along with recovered spent fluids, may be withdrawn from the well as indicated at  575 . Thus, as noted at  590 , power for subsequent well application may again be available via the battery assembly. 
         [0040]    Embodiments described hereinabove include an assembly and techniques for addressing limited battery life in a downhole environment. The assembly and replenishment techniques detailed allow for renewal of battery functionality in a manner that does not require a complete battery hardware change-out or long-term recharge on the scale of several hours. Indeed, the detailed replenishment is even flexible enough in nature to allow for intervention to occur at a time of operator choosing, for example, in conjunction with other interventions not necessarily dedicated to downhole battery issues. Thus, the costs in terms of time or resources dedicated to battery replenishment may be kept to a minimum. 
         [0041]    The preceding description has been presented with reference to presently preferred embodiments. Persons skilled in the art and technology to which these embodiments pertain will appreciate that alterations and changes in the described structures and methods of operation may be practiced without meaningfully departing from the principle, and scope of these embodiments. Furthermore, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings, but rather should be read as consistent with and as support for the following claims, which are to have their fullest and fairest scope.