Patent Publication Number: US-2012031669-A1

Title: Memory Logging Drill Bit With Connectable Pulser

Description:
TECHNICAL FIELD OF INVENTION 
     The present invention relates to a new tool for use in subterranean exploration. In particular, the invention relates to a drill bit having an integral downhole data collection system having selectable on-board sensors and a centralized compact and removable pulser locatable internal to the drill bit. The new system has unique capabilities, functions and operations which are improvements over the known measurement-while-drilling (MWD) and logging-while-drilling (LWD) systems. The present invention provides rapid at the drill bit data collection and communication. 
     BACKGROUND OF THE INVENTION 
     In the exploration of oil, gas, and geothermal energy, drilling operations are used to create boreholes, or wells, in the earth. In many locations, the law requires creation of a log, or record, indicating the precise disposition of the descending wellbore. For vertical wellbores, inclination is usually the only required measurement of the path of the wellbore. It is also important to monitor the temperature of the well, which affects the calculation of the well angle data obtained from the onboard accelerometers. 
     Measurement-while-drilling (MWD) involves the evaluation of physical properties, such as pressure, temperature and wellbore trajectory in three-dimensional space, while extending a wellbore. The measurements are made downhole, stored in solid-state memory for a short time, and then transmitted to the surface. Data transmission usually involves digitally encoding data and transmitting the stored sensor measurements to the surface as pressure pulses in the mud system. The pressures may be positive, negative or continuous sine waves. Some MWD tools have the ability to store the measurements for later retrieval with wireline or when the tool is tripped out of the hole if the data transmission link fails. 
     For the purpose of optimizing the economics of the drilling operation, it is highly desirable to monitor numerous physical variables at the drill bit, including vibration and impact forces, torque, internal and external pressure, temperature, and other variables. Technological and economic barriers have prevented the development of an acceptable tool for measuring and recording this data at positions near to the bit. Likewise, there is no commercially available means for real time transmission of such data to the rig floor, where it could be used to optimize the parameters of the well being drilled and potentially avoid catastrophic failure of the drill bit and well. 
     Memory logging without real time transmission eliminates the need for an interface between data measurement and data transmission by sending sensor signals directly to memory storage. This eliminates processing and allows unlimited transfer and storage of large amounts of data which can be readily processed and analyzed when downloaded and as needed. Naturally, it would be even better to transmit this data to the surface in real time if the technology was available. 
     It is highly desirable to have down-hole measurements taken from a point nearest to the drill bit. This data is desirable for the purpose of obtaining a meaningful understanding or reconstruction of what happened during the drilling process. A principal disadvantage of conventional logging-while-drilling and measurement-while-drilling systems is that they must be mounted away from the drill bit. Conventional systems include actuators, a pulser, a motor, sensors, and battery systems which collectively comprise lengthy systems that are mounted on the surface side of the mud motor used to rotate the drill bit. This reduces the accuracy of the measurements taken and fails to provide near bit data for analysis. Also, it is necessary to locate the mud motor very close to the drill bit to prevent destruction and premature failure of the mud motor that results from high-speed rotation of longer and heavier drill string components below the mud motor. 
     Thus, it remains highly desirable to locate the sensors closer to the drill bit to provide data of greater value related to the forces acting on the bit itself. It is also highly desirable to provide an option for real-time communication of dynamic measurements of the drill bit such that indications of its wear and movement can be used to avoid catastrophic failure. It is also highly desirable to provide these capabilities 
     Prior art tool configurations that attempt to do this have failed to meet the economic and reliability requirements necessary to achieve commercial application. The harsh drilling environment, length and complexity of logging, and pulsing equipment have prevented efforts to accomplish this goal in the past. In particular, it has proven impractical to separate the drill bit from the mud motor by more than approximately 36 inches, and thus not possible to accommodate a lengthy MWD tool section below the mud motor. 
     Therefore, there is a need to develop an improved drill bit system which drills the well, takes measurements at the drill bit, records the measurements, and optionally sends real time data to the rig floor. There is a need for this system to be readily serviceable and highly compact, specifically, to have a length of approximately less than approximately 36 inches. There is also a need to develop a flexible system that can be configured to the requirements of the particular well being drilled. There is also a need to accomplish these goals at a reasonable cost. 
     SUMMARY OF THE INVENTION 
     The present invention provides a substantially improved and entirely unique drill bit system. In one embodiment of the present invention, the drill bit system is generally comprised of a bit head having a plurality of cutters attached to the bit head. A bit body having a hollow center extends upwards from the bit head. A threaded connection is located opposite to the bit head for connection to a drill string component. A plurality of sealed chambers is located in substantially symmetrical orientation on the bit body. At least one battery source is located in one of the chambers. Additional battery sources can be located in other chambers. An electrical circuit board is located in a chamber, and has an electronically connected data storage unit. Sensors are also located in one or more chambers. A chamber passage is provided for connecting adjacent chambers. A first electrical connection is located in the chamber passage for electrically connecting the battery source to the electrical circuit board. 
     In another embodiment, an interior portal is provided for connecting the hollow center of the drill bit to a chamber. A compact and removable pulser assembly is provided that is centrally positionable within the hollow center of the bit body. An electrical pulser connection electrically connects the pulser to the electrical circuit board and the battery source through an interior portal. In the embodiment, electrical signals from the circuit board actuate the pulser to generate momentary restrictions of the mud flow through the hollow center of the drill bit assembly. 
     In another embodiment, a second battery source is located in a chamber, and is electrically connected to the first battery source. In another embodiment, a third battery source is located in a chamber and is electrically connected to the first battery and second battery sources. The electrical connections pass through chamber passages to connect the first battery source, the second battery source, and the third battery source in electrical series connection. 
     In another embodiment, an external pressure transducer is mounted on an external surface of the drill bit body. An electrical connection is provided between the circuit board and the external pressure transducer. In this embodiment, electrical signals reflecting the pressure on the exterior of the drill bit are received by the circuit board, where they may be processed or recorded on the electronic data storage unit. 
     In another embodiment, an internal pressure transducer is mounted on the surface of the hollow interior of the drill bit body. An electrical connection is provided between the circuit board and the internal pressure transducer. In this embodiment, electrical signals reflecting the pressure on the hollow interior of the drill bit body are received by the circuit board, where they may be recorded on the electronic data storage unit. 
     In another embodiment, a download portal extends between the exterior of the bit body and a chamber. A download plug is located in the portal, and is electrically connected to the circuit board in a chamber. A sealed plug cover encloses the download portal and plug from the environment. 
     In another embodiment, the pulser has a flow diverter located on its upper end. A tubular centralizer body is attached to the diverter. Centralizer fins are positioned on the exterior of the centralizer body for centralizing the pulser within the hollow interior of the bit body. A motor is located inside the centralizer body. A hollow pulser plug is secured to the lower end of the centralizer body. A wheel housing is attached to the lower end of the pulser plug. A rotatable wheel is mounted on the lower end of the drive shaft, and is located inside the wheel housing. 
     A pulser portal is provided through the centralizer body and centralizer fins in alignment with the interior portal of the bit body. A feed-through pin extends through the interior portal and the pulser portal to provide a sealed passage for an electrical connection. An electrical pulser connection is positioned inside the feed-through pin, electrically connecting the motor to the electrical circuit board and the battery source. 
     A bolt portal is located inside a chamber. A fastener is located in the bolt portal and thread connected to the wheel housing to secure the pulser in place inside the drill bit. 
     Previous field tests have shown it is possible to acquire data that can help determine equivalent circulating density of the mud flow system and this or these sensors will also be a part of the memory data system that is stored for later study. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The objects and features of the invention will become more readily understood from the following detailed description and appended claims when read in conjunction with the accompanying drawings in which like numerals represent like elements. 
       The drawings constitute a part of this specification and include exemplary embodiments to the invention, which may be embodied in various forms. It is to be understood that in some instances various aspects of the invention may be shown exaggerated or enlarged to facilitate an understanding of the invention. 
         FIG. 1  is a side view of a prior art PDC drill bit. 
         FIG. 2  is an isometric view of the drill bit assembly of the present invention. 
         FIG. 3  is a cross-sectional view of the drill bit assembly of  FIG. 2  illustrating the bit body chambers and network of passages between the chambers, and illustrating the portals between the chambers and the hollow interior of the drill bit. 
         FIG. 4  is an exploded view illustrating the primary electrical components present in the chambers and further illustrating the externally accessible download plug. 
         FIG. 5  is a side view of the compact pulser, made in accordance with the present invention. 
         FIG. 6  is a cross-sectional side view of the pulser of  FIG. 5 , illustrating the relationship of its component parts. 
         FIG. 7  is an exploded view of the preferred embodiment in which a compact, removable pulser is located internally within the drill bit. 
         FIG. 8  is an isometric cross-section illustrating the drill bit assembly shown with the pulser centralized inside the drill bit and connected to the electric components located in the chambers of the bit body. 
         FIG. 8A  is a sectional view taken from  FIG. 8  illustrating a feed through pin connecting the bit body and the pulser. 
         FIG. 8B  is a sectional view taken from  FIG. 8  illustrating fasteners securing the pulser inside the hollow interior of the drill bit. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description is presented to enable any person skilled in the art to make and use the invention, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein. 
       FIG. 1  is a side view of a prior art PDC drill bit. As shown in this view, drill bit  10  has a hollow pin connection  20  on its upper end, a shank, or bit body  30  extending downward from pin  20 , and a bit head  40  on the opposite end of body  30 . A plurality of cutters  42  are positioned on bit head  40  for disintegration on formation. One or more nozzle outlets  404  (not shown) are located on bit head  40 , providing an exit passage for drilling fluid from the interior of drill bit  10 . 
       FIG. 2  is an isometric view of drill bit assembly  100  of the present invention. Drill bit  100  has a hollow pin connection  200  on its upper end, a bit body  300  extending downward from pin  200 , and a bit head  400  on the opposite end of body  300 . A plurality of cutters  402  are positioned on bit head  400  for disintegration on formation. One or more nozzle outlets  404  are located on bit head  400 , providing an exit passage for drilling fluid from the interior of drill bit  100 . 
     Pin  200  comprises a threaded pin  202  for connection to a drill string component, and a slot  204  for applying torque between the drill string and pin  202  for securing drill bit  100  to the drill string. 
     Body  300  of drill bit  100  has a hollow center  110  (illustrated in  FIG. 3 ). A plurality of chamber covers  310  is removably secured to body  300 . In another embodiment, a separate download plug cover  320  is removably secured to body  300 . 
       FIG. 3  is cross-sectional view of the drill bit assembly  100  of  FIG. 2  with chamber covers  310  and plug cover  320  removed and primary electrical components removed. Bit  100  has a hollow interior  110 . A plurality of chambers  330  are formed on the exterior surface of bit body  300 . In a preferred embodiment, chambers  330  are located in substantially symmetrical orientation on bit body  300 . Chamber passages  332  connect adjacent chambers to form an interconnected subsurface network beneath the exterior surface of bit body  300 . 
     In a preferred embodiment, a plurality of interior portals  334  are located in chambers  330  and intersect hollow interior  110  of drill bit  100 . In a more preferred embodiment, interior portals  334  are generally cylindrical and have a centerline approximately intersecting the centerline of hollow interior  110 . 
     In another preferred embodiment, a download port  340  is located beneath the exterior surface of bit body  300 . Download port  340  is covered and sealed from the external environment by port cover  320  ( FIG. 2 ). A download channel  336  extends between download port  340  and one of sealed chambers  330 . 
       FIG. 4  is an exploded view of the embodiment disclosed in  FIG. 2 , illustrating the primary electrical components present in chambers  330  and further illustrating the externally accessible download plug  342 . Batteries  350  are located in sealed chambers  330 . A circuit board  352  having an associated memory storage unit is also located in a sealed chamber  330 . One or more sensors  354  are also located in a sealed chamber  330  and are electrically connected to circuit board  352 . 
     Electrical connections  360  (not shown) are located in chamber passages  332  electrically connecting batteries  350  to electrical circuit board  352 . A download plug  342  is located in download port  340 , and is accessible upon removal of plug cover  320 . Download plug  342  is electrically connected to circuit board  352  by wiring (not shown) located in download channel  336  ( FIG. 3 ). 
     In another preferred embodiment (not illustrated), an external portal is provided. An external pressure transducer is surface mounted on the external surface of drill bit body  300 . An electrical connection is provided between external pressure transducer and circuit board  352 . 
     In another preferred embodiment (not illustrated), an internal pressure transducer is mounted in an interior portal  334 , exposed to the fluid flow inside hollow interior  110  of drill bit body  300 . An electrical connection is provided between internal pressure transducer and circuit board  352 . 
       FIG. 5  is a side view of a compact, removable pulser  500  made in accordance with the present invention. Pulser  500  has a conical flow diverter  510  on its upper end. A hollow centralizer body  520  is located beneath diverter  510 . A plurality of centralizer fins  530  is located on centralizer body  520 . A body plug  540  is attached to the lower end of centralizer body  520 . A wheel assembly  550  is attached to the lower end of body plug  540 . 
       FIG. 6  is a cross-sectional side view of pulser  500  of  FIG. 5 , illustrating the relationship of its component parts. As shown in this view, a motor  522  is located inside hollow centralizer body  520 . A motor shaft  524  extends from the lower end of motor  522 . In a preferred embodiment, a flexible drive connector  526 , such as an Oldham connector, is connected to motor shaft  524 . In another preferred embodiment, flexible connector  526  is positioned in a holder  528 . 
     The upper end of plug  540  is located inside hollow centralizer body  520 . The lower end of plug  540  extends below centralizer body  520 . 
     Plug  540  has a hollow bore  542 . A drive shaft  544  is located in bore  542 . The upper end of drive shaft  544  is connected to motor  522  through flexible connector  526  such that rotation of motor  522  rotates drive shaft  544 . 
     Wheel assembly  550  includes a ventilated wheel housing  552 . A plurality of bolt receiving holes  554  is located on the outer diameter of wheel housing  552 . A rotatable wheel  556  is positioned inside wheel housing  552 . 
     A bearing end cap  558  secures wheel  556  inside wheel assembly  550 . Drive shaft  544  is attached at its lower end to wheel  556  by a drive shaft nut  548 , such that rotation of drive shaft  544  rotates wheel  556 . As best seen in  FIG. 6 , a plurality of wheel passages  562  extend through wheel  556  for selective alignment with complementary housing passages  564  in wheel housing  552 . 
     Referring again to  FIG. 6 , a pulser portal  532  extends through centralizer fin  530  and through hollow centralizer body  520 . In the preferred embodiment, a centralizer tube  534  is located in pulser portal  532 . 
       FIG. 7  is an exploded view of the preferred embodiment in which compact, removable pulser  500  is located inside hollow interior  110  of drill bit  100 . When so positioned, pulser  500  is axially aligned such that receiving holes  554  are in alignment with lower interior portals  334  (see  FIG. 3 ) nearest bit head  400 , and pulser portal  532  is in alignment with an upper interior portal  334  ( FIG. 3 ). 
       FIG. 8  is an isometric cross-section of pulser  500  centralized in hollow interior  110  of drill bit  100 . Pulser  500  is axially aligned such that receiving holes  554  are in alignment with lower interior portals  334 . Fasteners  600  are located in interior portals  334  to attach wheel assembly  550  to drill bit body  300 . A feed through pin  610  is located in upper interior portal  334  aligned with pulser portal  532  to provide a sealed passageway through which an electrical motor connection  612  can pass for connection of motor  522  to circuit board  352 . 
       FIG. 8A  is a sectional view taken from  FIG. 8  illustrating feed through pin  610  located in upper interior portal  334  to provide a sealed passage for electrical connection between batteries  350 , circuit board  352  and motor  522 . 
       FIG. 8B  is a sectional view taken from  FIG. 8  illustrating fasteners  600  located in lower interior portals  334  and secured to bolt receiving holes  554  on wheel housing  552 , thus securing pulser  500  inside hollow interior  110  of drill bit  100 . Referring back to  FIG. 8 , centralizer fins  530  centralize the upper portion of pulser  500  inside hollow interior  110  of drill bit  100 . 
     OPERATION OF THE INVENTION 
     The present invention provides a substantially improved drill bit system in which drill bit  100  may be optionally configured as a conventional drill bit, as a memory logging drill bit, or as an MWD drill bit including a novel compact and removable pulser  500 . In one embodiment of the present invention, drill bit  100  is generally comprised of a bit head  400  having a plurality of cutters  402  attached for disintegration of the formation. Bit body  300  has a hollow center  110  extending upwards from bit head  400 . 
     A conventional threaded pin connection  200  is located opposite to bit head  400  for connection to a drill string component. Sealed chambers  330  are located in substantially symmetrical orientation on bit body  300 . Interior portals  334  extend from chambers  300  to hollow interior  110  of drill bit  100 . In one embodiment, interior portals  334  may be plugged, such as with threaded fasteners  600 , or plugs attached by other means. In this embodiment, drill bit  100  functions in a manner similar to that of prior art PDC drill bit  10  (see  FIG. 1 ). 
     In a more preferred embodiment, drill bit  100  is configured for memory logging. Referring to  FIG. 4 , in this embodiment, at least one battery source  350  is located in one of the chambers  330 . Additional battery sources can be located in other chambers  330 . One or more electrical circuit boards  352  are located in another chamber  330 . Circuit board  352  has an electronic data storage unit and sensors  354 . Sensors  354  may be of various types well known in the oil and gas industry, and may typically include accelerometers. Cover plates  310  protect the contents of chambers  330  from the drilling fluid and cuttings. 
     Chamber passages  332  form a network of subsurface passages  332  between chambers  330  through which electrical connections  360  (not shown) are located to facilitate electrical connection between the batteries  350 , circuit boards  352  and sensors  354  in a manner protected from the drilling fluid environment. 
     In a preferred embodiment, download port  340  is provided. Download plug  342  is located in download port  340  and covered by download plug cover  320  for protection from the drilling fluid during drilling operations. Download passage  336  connects download port  340  to a chamber  330  where circuit board and data storage unit  352  are located. Electrical wiring in download passage  336  connects download plug  342  to circuit board and data storage unit  352 . 
     As drilling progresses, sensors  354  provide data to circuit board and data storage unit  352 . When drill bit  100  is brought to the surface, download plug cover  320  can be removed for access to download plug  342 . This permits rapid download of the data stored on circuit board and data storage unit  352 . The immediate access to the data can be used to change operating parameters on the drilling rig, change the drilling bit, make adjustments to the drill string configuration, or used in other decisions for the optimization of the drilling operation. Additionally, download plug  342  can be configured to permit charging of batteries  350 . As generally described above, drill bit  100  is configured as a memory logging drill bit  100  with sensors  354  located advantageously near to drill bit head  400 . 
     In another embodiment, an external pressure transducer (not illustrated) is mounted on an external surface of drill bit body  300 . An electrical connection is provided between circuit board  352  and the external pressure transducer. In this embodiment, electrical signals reflecting the pressure on the exterior of drill bit  100  are processed and/or recorded on the electronic data storage unit of circuit board  352 . 
     In another embodiment, an internal pressure transducer (not illustrated) is mounted on the surface of hollow center  110  of drill bit body  300 . An electrical connection is provided between circuit board  352  and the internal pressure transducer. In this embodiment, electrical signals reflecting the pressure on the interior of drill bit  100  are processed and/or recorded on the electronic data storage unit of circuit board  352 . 
     In another embodiment, drill bit  100  is configured as an MWD drill bit capable of sending real time data to the surface of the rig by means of mud pulses sent through a compact and removable pulser  500 . Unlike conventional MWD tools, in the present invention, the power source (batteries  350 ) and electronics (circuit board and data storage unit  352  and sensors  354 ) are located generally concentrically around pulser  500 . By electrically connecting to the electronics ( 350 ,  354 ,  352 ,  360 ) built integrally into drill bit body  300  for memory logging through alignment of pulser portal  532  located in centralizing fin  530  with internal portal  334 , an extremely compact MWD drill bit can be made to provide real time data transmission from sensors  354  located advantageously near to drill bit head  400 . 
     In this embodiment, drill bit  100  is configured substantially the same as the memory logging bit described above, except in that interior portals  334  are not plugged. Referring to  FIG. 8 , compact pulser  500  is positioned inside hollow center  110  of drill bit  100 . Centralized fins  530  centralize pulser  500  in hollow center  110 . Pulser  500  is rotated until pulser portal  532  is in axial alignment with an interior portal  334 . At this point of alignment, bolt receiving holes  554  on wheel housing  552  are also in alignment with other interior portals  334 . 
     Fasteners  600  are placed through interior portals  334  and secured to bolt receiving holes  554  on wheel housing  552 . This holds pulser  500  in place inside hollow center  110  of drill bit  100 . In a preferred embodiment, a centralizer tube  534  is located inside pulser portal  532 , and a feed through pin  610  extends through interior portal  532  and centralizer tube  534 . An electrical connection  360  (not shown) is located inside feed through pin  610  to electrically connect motor  522  of pulser  500  with batteries  350  and circuit board and data storage unit  352 . 
     Chamber passages  332  form a network of subsurface passages  332  between chambers  330  through which electrical connections  360  (not shown) are located to facilitate electrical connection between the batteries  350 , circuit boards  352  and sensors  354  in a manner protected from the drilling fluid environment. 
     As drilling fluid is pumped down the interior of the drill string, it reaches hollow center  110  of drill bit body  300 , and flow diverter  510 . Flow diverter  510  reduces the pressure loss caused by the impingement of high speed fluid flow on pulser  500 . As drilling progresses, sensors  354  provide data to circuit board and data storage unit  352 . Circuit board and data storage unit  352  process the sensor signal and send an output signal to motor  522 . Referring to  FIG. 6 , the output signal activates rotation of motor  522 , which rotates drive shaft  544  and thus rotatable wheel  556 . 
     Rotation of wheel  556  moves wheel passages  562  and wheel housing passages  564  out of alignment, thus generating a momentary restriction of the mud flow through hollow center  110  of drill bit  100 . This restriction results in a system pressure spike that is detectable at the rig surface. The pulses detected at the rig surface communicate to rig personnel the data provided by sensors  354 . 
     Real time access to data generated proximate to drill bit head  400  can be used to change operating parameters on the drilling rig while drilling, or used to make a decision to remove the drill bit entirely. When drill bit  100  is brought to the surface, pulser  500  can be retained or removed. If pulser  500  fails for any reason, data stored on circuit board and data storage unit  352  can be downloaded through download plug  342 , and a new pulser  500  can be placed in hollow center  110  of drill bit body  300 . 
     As cutters  402  on drill bit  100  wear down, pulser  500  and electrical components such as batteries  350 , circuit board  352  and sensors  354  can be removed and installed inside a new drill bit  100 . 
     In the manner described above, drill bit assembly  100  can be manufactured and assembled to include pulser  500  such that the overall length is sufficiently short to permit real-time data transmission from below a mud motor. For example, an 8½ inch drill bit assembly  100  can be manufactured, including the internal assembly of pulser  500 , to have a length of 36 inches or less. For example, an 8¾ inch drill bit assembly  100  can have an overall length, including bit head  400 , pulser  500  and threaded pin  202 , of less than 30 inches. 
     It will be readily apparent to those skilled in the art that the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present invention. 
     Having thus described the present invention by reference to certain of its preferred embodiments, it is noted that the embodiments disclosed are illustrative rather than limiting in nature and that a wide range of variations, modifications, changes, and substitutions are contemplated in the foregoing disclosure and, in some instances, some features of the present invention may be employed without a corresponding use of the other features. Many such variations and modifications may be considered desirable by those skilled in the art based upon a review of the foregoing description of preferred embodiments. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.