Patent Publication Number: US-10309197-B2

Title: System and method for autonomous downhole power generation

Description:
RELATED APPLICATIONS 
     The present application is a divisional of and claims prior to U.S. patent application Ser. No. 14/496,682, filed on Sep. 25, 2014, titled “System And Method for Autonomous Downhole Power Generation,” the entire content of which is incorporated herein by reference. The present application is related to U.S. patent application Ser. No. 14/496,673, titled “Downhole Power Generation System And Method,” and filed concurrently herewith; and U.S. patent application Ser. No. 14/496,688, titled “Downhole Power Generation System with Alternate Flow Paths,” and filed concrurrently herewith. 
    
    
     TECHNICAL FIELD 
     The present application relates to downhole power generation. Specifically, the present application relates to an autonomous downhole power generation system with extended life. 
     BACKGROUND 
     In certain downhole operations, power is needed to run various components of a downhole assembly. For example, power is needed to drive actuators for valves and other components, and to power various sensors and communication devices. In many cases, power is generated downhole via a downhole power generation device that is coupled to the downhole assembly. Some of the devices may be designed to use mechanical power from the fluid flow to generate electric power downhole such as the mechanisms using flow induced vibration, turbomachinery, and the like. However, when such power generation mechanism is designed to run continuously, it must endure a large amount of stress and wear. This leads to a short operating device life. This is a problem because maintenance of such devices is extremely difficult and often impossible, and the expected life of such devices is much shorter than the life of the well. Additionally, such power generation devices typically generate more power than is needed to carry out the functions of the downhole assembly. Thus, the stress and wear seen by the power generation mechanism in generating the excess power does not translate into increased utility. 
     SUMMARY 
     In general, in one aspect, the disclosure relates to an autonomous downhole power generation system. The system includes a power generation device configured to be disposed in an annular space around a portion of a production tubing, wherein the power generation device is switchable between a power generation mode and a bypass mode. The system further includes a power storage device electrically coupled to the power generation device and configured to store power generated by the power generation device. The system also includes a control processor communicatively coupled to the power storage device and the power generation device, wherein the control processor receives a measure of power stored in the power storage device and switches the power generation device between the power generation mode and the bypass mode based on the measure of stored electric power in the storage device. 
     In another aspect, the disclosure can generally relate to an autonomous downhole power generation system. The system includes a power generation device configured to be disposed in an annular space around a portion of a production tubing, wherein the power generation device is switchable between a power generation mode and a bypass mode. The system also includes a power storage device electrically coupled to the power generation device and configured to store power generated by the power generation device. The system further includes a control processor communicatively coupled to the power generation device, wherein the control processor switches the power generation device between the power generation mode and the bypass mode based on a preprogrammed operational protocol. 
     In another aspect, the disclosure can generally relate to a method of generating power in a downhole environment. The method includes detecting, by a control processor, a measured power level of a power storage device or an operational condition. The method also includes determining, by the control processor, that the measured power level of the power storage device is below a first threshold level or that the operational condition matches one of a plurality of predefined activation conditions. The method further includes switching, by the control processor, a power generation device from a bypass mode to a power generation mode, wherein the power generation device generates power via a power generation mechanism when in the power generation mode, and bypasses the power generation mechanism in the bypass mode. 
     These and other aspects, objects, features, and embodiments will be apparent from the following description and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings illustrate only example embodiments of the present disclosure, and are therefore not to be considered limiting of its scope, as the disclosures herein may admit to other equally effective embodiments. The elements and features shown in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the example embodiments. Additionally, certain dimensions or positions may be exaggerated to help visually convey such principles. In the drawings, reference numerals designate like or corresponding, but not necessarily identical, elements. In one or more embodiments, one or more of the features shown in each of the figures may be omitted, added, repeated, and/or substituted. Accordingly, embodiments of the present disclosure should not be limited to the specific arrangements of components shown in these figures. 
         FIG. 1  illustrates a schematic diagram of a well site in which an autonomous downhole power generation system has been deployed, in accordance with example embodiments of the present disclosure; 
         FIG. 2  illustrates a cross-sectional diagram of the power generation system disposed around the production tubing, in accordance with example embodiments of the present disclosure; 
         FIG. 3  illustrates a block diagram of the power generation system, in accordance with example embodiments of the present disclosure; 
         FIG. 4  illustrates a method of autonomous control of the power generation system based on the current power level of the power storage device, in accordance with example embodiments of the present disclosure; and 
         FIG. 5  illustrates a method of autonomous control of the power generation system based on a preprogrammed operational protocol, in accordance with example embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS 
     Example embodiments directed to an autonomous downhole power generation system will now be described in detail with reference to the accompanying figures. Like, but not necessarily the same or identical, elements in the various figures are denoted by like reference numerals for consistency. In the following detailed description of the example embodiments, numerous specific details are set forth in order to provide a more thorough understanding of the disclosure herein. However, it will be apparent to one of ordinary skill in the art that the example embodiments disclosed herein may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description. The example embodiments illustrated herein include certain components that may be replaced by alternate or equivalent components in other example embodiments as will be apparent to one of ordinary skill in the art. 
     Referring now to the drawings,  FIG. 1  illustrates a schematic diagram of a well site  100  in which an autonomous downhole power generation system  102  has been deployed, in accordance with example embodiments of the present disclosure. In certain example embodiments, and as illustrated, the autonomous downhole power generation system  102  (hereinafter “power generation system”) is deployed in a wellbore  108 . The wellbore  108  is formed in a subterranean formation  118  and coupled to a rig  110  on a surface  112  of the formation  118 . The formation  118  can include one or more of a number of formation types, including but not limited to shale, limestone, sandstone, clay, sand, and salt. The surface  112  may be ground level for an on-shore application or the sea floor for an off-shore application. In certain embodiments, a subterranean formation  118  can also include one or more reservoirs in which one or more resources (e.g., oil, gas, water, steam) are located. In certain example embodiments, the wellbore  108  is cased with cement or other casing material, which is perforated to allow fluids to flow from the formation  118  into the wellbore  108 . In certain example embodiments, the well  108  is a multi-zone well. A production tubing  106  is disposed downhole within the wellbore  108 . Fluids are recovered and brought to the rig  110  through the production tubing. In certain example embodiments, a production packer  105  is coupled to the production tubing  106 . 
     In certain example embodiments, the power generation system  102  is disposed in an annular space  114  around a portion of the production tubing  106 . The annular space  114  is the space between the production tubing  106  and the wellbore  108 .  FIG. 2  illustrates a cross-sectional diagram  200  of the power generation system  102  disposed around the production tubing  106 , in accordance with example embodiments of the present disclosure. Referring to  FIGS. 1 and 2 , in certain example embodiments, the power generation system  102  is sealed between the production tubing  106  and the wellbore  108  such that fluid traveling from a first portion of the annular space  114   a  to a second portion  114   b  of the annular space is forced to travel through the power generation system  102 , in which the first portion of the annular space  114   a  is adjacent a first end  104  of the power generation system  102  and the second portion of the annular space  114   b  is adjacent a second end  107  of the power generation system  102 . In certain example embodiments, a portion of the wellbore  108  adjacent the first portion of the annular space  114   a  is perforated, allowing production fluid to flow into the first portion of the annular space  114   a.    
     In certain example embodiments, a first portion of the production tubing  106   a  adjacent the first portion of the annular space  114   a  and the first end  104  of the power generation system  102  is not perforated, such that production fluid flowing into the first portion of the wellbore  108   a  does not flow directly into the first portion of the production tubing  106   a . Rather, in certain example embodiments, the production fluid flowing to the first portion of the wellbore  108   a  is forced to flow through the power generation system  102  and into the second portion of the annular space  114   b . In certain example embodiments, a second portion of the production tubing  106   b  adjacent the second portion of the annular space  114   b  contains flow control valves  202 , which allow the production fluid to flow from the second portion of the annular space  114   b  into the production tubing  106 . The production fluid can then travel to the surface  112  where it is recovered. 
     In certain example embodiments, the inside of the production tubing  106  is only in communication with the annular space  114  via the power generation system  102 , and thus production fluid is forced to travel through the power generation system  102  in order to enter the production tubing  106  and ultimately be recovered. In certain example embodiments, flow of production fluid through the power generation system  102  allows the power generation system  102  to generate power, which is stored in a power storage device  210 , such as a rechargeable battery, capacitor, or the like. 
     In certain example embodiments, and as best shown in  FIG. 2 , the power generation system  102  includes at least one power generation path  204  and at least one bypass path  206 . In certain example embodiments, production fluid must travel through either the power generation path  204  or the bypass path  206  in order to enter the production tubing  106 . In certain example embodiments, the power generation path  204  includes one or more power generation mechanisms  208  disposed therein, which generate power when traversed by the flow of production fluid. In certain example embodiments, the power generation mechanism  208  can include piezoelectric power generation elements, turbomachinery, or other electromagnetic power generation devices. Thus, these components are activated and energy is generated when production fluid flows through the power generation path  204 . 
     In certain example embodiments, the bypass path  206  is isolated from the power generation mechanism  208  and provides a path for production fluid to flow through the power generation system  102  without interacting with the power generation mechanism  208 . Thus, the power generation mechanism  208  is bypassed and does not generate power when fluid flows only through the bypass path  206 . 
     Both the power generation path  204  and the bypass path  206  provide a path for the production fluid to travel through. In certain example embodiments, the power generation path  204  and the bypass path  206  can be opened and closed in order to direct production fluid through the selected path. In certain example embodiments, the bypass path  206  is closed when the power generation path  204  is open. Thus, production fluid must travel through the power generation path  204 , engage with the power generation mechanism  208 , and power is generated. Alternatively, in certain example embodiments, the bypass path  206  is opened when the power generation path  204  is closed. As such, production fluid flows through the bypass path  206  and the flow is isolated from the power generation mechanism  208 . Thus, the power generation mechanism is not active. This allows the power generation mechanism to rest when power generation is not needed, which increases the overall life of the power generation mechanism. 
     In certain example embodiments, the power generation system  102  can be controlled to switch between a power generation mode and a bypass mode. Accordingly, when the power generation system  102  is in the power generation mode, the power generation path  204  is open, production fluid flows therethrough, activating the power generation mechanism  208 , and power is generated. In certain example embodiments, the generated power is saved in the power storage device  210 . The power stored in the power storage device can then be used to power various electronic parts of the downhole assembly, such as actuators, valves, sensors, communication modules, and other devices. When the power generation system  102  is in the bypass mode, the power generation path  204  is closed, production fluid flows through the bypass path  206 , and power is not generated. In certain example embodiments, both the bypass path  206  and the power generation path  204  are open during the power generation mode. In certain example embodiments, at least one power generation path  204  is inter-connected to at least one bypass path  206  such that the flow passing through the power generation mechanism  208  can exit through the bypass paths  206 . 
     In certain example embodiments, the power generation system  102  includes a control system  212 , which includes various control components such as a microprocessor, sensors, controllers, and the like. In certain example embodiments, the control system  212  controls the switching of the power generation system  102  between the power generation mode and the bypass mode. In certain example embodiments, the control system  212  controls the switching based on one or more parameters or predetermined operational conditions. For example, in a first group of embodiments, the control system  212  controls the switching based on actual power demand by measuring the amount of power currently stored in the power storage device  210 . In certain such embodiments, the control system  212  senses the current power level of the power storage device  210  via one or more sensors and compares the current power level to a first threshold level. If the measured power level is below the first threshold level, then the control system  212  switches the power generation system  102  into the power generation mode. In certain example embodiments, when the power generation system  102  is in the power generation mode, the control system  212  may switch the power generation system  102  to the bypass mode after a certain period of time, or when the measured power level of the power storage device  210  is above a second threshold value. In certain example embodiments, the second threshold value is higher than the first threshold value. Effectively, the power generation system  102  is used to generate power when the stored power is running relatively low and not used when the store power is still relatively high, rather than continuously generating power regardless of actual demand. This reduces the amount of wear on the power generation mechanism  208 , increasing the overall lifespan of the power generation system  102 . 
     In a second group of example embodiments, not exclusive of embodiments in the first group, the control system  212  controls switching between the power generation mode and the bypass mode based on current operational conditions, operational demands, and/or a preprogrammed protocol. For example, in one embodiment, the control system  212  switches the power generation system  102  to the power generation mode in anticipation of a power-consuming event such as actuating a valve. In certain example embodiments, the power generation system  102  is put in the power generation mode during or after such an event. In certain example embodiments, the power generation system  102  is put in the bypass mode after such an event occurs. In certain example embodiments, the control system  212  switches the power generation system  102  to the power generation mode at certain time intervals. In certain example embodiments, the control system  212  is preprogrammed to control the power generation system  102  in accordance to a protocol or program. The protocol or program defines the conditions under which the power generation system  102  is to be put in the power generation mode and the conditions under which the power generation system  102  is to be put in the bypass mode. Such conditions may include stored power level, time interval, actuation, certain events, and so forth. This allows the power generation system  102  to autonomously switch between the power generation mode and bypass mode without intervention, and further allows the power generation system  102  to provide maximum utility and reduce waste. 
     In certain example embodiments, switching between the power generation mode and the bypass mode includes mechanical actuation, such as driving a motor, which mechanically opens and closes the power generation path  204  and the bypass path  206 . In certain example embodiments, the switching includes expansion, contraction, or axial movement of a plug or packer type device in the power generation path  204  and the bypass path  206 , in which the device blocks the respective path when expanded. In certain example embodiments, the power generation system  102  may operate in the bypass mode as a default when the control system  212 , the power generation mechanism  208 , or other necessary component fails or is out of commission. 
       FIG. 3  illustrates a block diagram  300  of the power generation system  102 , in accordance with example embodiments of the present disclosure. In certain example embodiments, the block diagram  300  includes the control system  212 , the power storage device  210 , the power generator mechanism  208  which is coupled to a power generator actuator  302 , and one or more actuators  306  and sensors or transmitters  304  that the downhole assembly may have. In certain example embodiments, the control system  212  sends control commands to the power generator actuator  302 , which then actuates the power generator mechanism  208  accordingly. The power generator mechanism  208  generates power and sends the power to be stored in the power storage device  210 . The power storage device  210  provides power to the control system  212 , the actuators  306 , and sensors and transmitters  304 . In certain example embodiments, the control system  212  also controls and communicates with the sensors/transmitters  304  which are coupled to and communicate with the actuators  306 . In certain example embodiments, the power storage device  210  provides a signal to the control system  212  indicative of the amount of power stored in power storage device  210 . 
       FIG. 4  illustrates a method  400  of autonomous control of the power generation system  102  based on the current power level of the power storage device  210 , in accordance with example embodiments of the present disclosure. In certain example embodiments, controlling of the power generation system  102  is performed by the control system  212  of the power generation system  102  and includes switching between operating the power generation system  102  in the power generation mode and operating the power generation system  102  in the bypass mode. Referring to  FIG. 4 , the method includes detecting the current power level of a power storage device  210  (step  402 ). In certain example embodiments, the control system  212  is coupled to a sensor or electrical connection which senses the amount of power stored in the power storage device  210  and receives the value as data. The method  400  further includes determining if the measured power level of the power storage device is below a first threshold level (step  404 ), and switching the power generation device from a bypass mode to a power generation mode when the measured power level of the power storage device  210  is below the first threshold level (step  406 ). In certain example embodiments, the control system  212  compares the measured power level to the first threshold value stored in memory and puts the power generation system  102  into the power generation mode if the measured power level is lower than the first threshold value. Thus, the power generation path  204  is opened and production fluid is directed to flow therethrough, engaging the power generation mechanism  208  and generating power (step  408 ). In certain example embodiment, the method  400  includes switching the power generation system  102  from the power generation mode to the bypass mode when the measured power level of the power storage device  210  is equal to or greater than a second threshold value (step  410 ). In certain example embodiments, the second threshold value may represent the full charge capacity of the power storage device. 
       FIG. 5  illustrates a method  500  of autonomous control of the power generation system  102  based on a preprogrammed operational protocol, in accordance with example embodiments of the present disclosure. In certain example embodiments, controlling of the power generation system  102  is performed by the control system  212  of the power generation system  102  and includes switching between operating the power generation system  102  in the power generation mode and operating the power generation system  102  in the bypass mode. Referring to  FIG. 5 , the method includes detecting a current operational condition or parameter of the downhole assembly to which the power generation system  102  is coupled (step  502 ). The method  500  further includes determining if the current operational condition or parameter matches one of a plurality of activation conditions (step  504 ), and switching the power generation device from a bypass mode to a power generation mode when the current operational condition or parameter matches one of a plurality of activation conditions (step  506 ) saved in memory as a part of a preprogrammed operational protocol. For example, the plurality of activation conditions may include actuation of a valve, a certain time parameter, and any other event in which it is desirable or advantageous to trigger the power generation mode and generate power. When the power generation system  102  is put into the power generation mode, the power generation path  204  is opened and production fluid is directed to flow therethrough, engaging the power generation mechanism  208  and generating power (step  508 ). In certain example embodiment, the method  500  includes switching the power generation system  102  from the power generation mode to the bypass mode when a deactivation condition is met (step  510 ). In certain example embodiments, the deactivation parameter is when the current operational state no longer matches one of the plurality of activation conditions. In other example embodiments, the deactivation parameter is a certain time period after switching to the power generation mode. In certain example embodiments, events or conditions which trigger the control system  212  to automatically put the power generation system  102  into the power generation mode or the bypass mode can be any type of condition that can be programmed into the memory or processor of the control system  212 , and are not limited to the examples discussed above. 
     Although embodiments described herein are made with reference to example embodiments, it should be appreciated by those skilled in the art that various modifications are well within the scope and spirit of this disclosure. Those skilled in the art will appreciate that the example embodiments described herein are not limited to any specifically discussed application and that the embodiments described herein are illustrative and not restrictive. From the description of the example embodiments, equivalents of the elements shown therein will suggest themselves to those skilled in the art, and ways of constructing other embodiments using the present disclosure will suggest themselves to practitioners of the art. Therefore, the scope of the example embodiments is not limited herein.