Patent Publication Number: US-7913775-B2

Title: Subsurface formation core acquisition system using high speed data and control telemetry

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates generally to the field of devices and methods for obtaining samples (cores) of subsurface Earth formations during the drilling of wellbores. More specifically, the invention relates to coring devices and methods that use high speed data and control signal telemetry to improve the efficiency of core recovery. 
     2. Background Art 
     During drilling of wellbores through subsurface Earth formations, it is known in the alt to drill samples of such formations for recovery from the wellbore and subsequent analysis at the surface. Such sample taking is referred to as “coring.” Coring typically includes drilling the wellbore using an annular drill bit, such that a substantially cylindrical sample of the formation is moved into a recovery chamber or “barrel” during the coring operation. It is desirable to maintain environmental conditions in the sample as close as is practicable to those existing in the subsurface at the depth of the core sample so that an accurate analysis of the fluid content, mineral composition and fluid transport properties of the sample may be made. Various devices are known in the art for maintaining such conditions and for making measurements of various physical parameters on the sample during its acquisition. One such device is disclosed in U.S. Pat. No. 5,984,023 issued to Sharma et al. 
     A limitation common to all coring techniques and devices known in the art is that they rely in indirect indicators to inform the wellbore operator as to the status of the core sampling operation. For example, it is necessary to infer that the entire core sample chamber (“core barrel”) has been filled with a core sample by having drilled a length of the wellbore that is substantially equal to the axial length of the core barrel. It is not possible, using techniques known in the art, to determine whether the core barrel is in fact full of core sample without retrieval of the core drilling tool assembly from the wellbore. Further, it is not possible to be assured of the quality of a particular core sample, or that the core sample has even been retained in the core barrel, during retrieval of the core drilling tool assembly from the wellbore. All of the foregoing limitations can result in costly, inefficient coring operations. 
     Recently, a type of drill pipe (“wired drill pipe”) that enables transmission of electrical power and/or electrical signals along a drilling tool assembly has been developed. One example of such wired drill pipe is disclosed in U.S. Patent Application Publication No. 2006/0225926 filed by Madhavan et al. and assigned to the assignee of the present invention. Such wired drill pipe has been adapted to transmit, substantially in real time to the surface measurements made of various properties of the subsurface formations. While such measurements are quite useful, they cannot entirely replace analysis of actual samples of the subsurface formations in order to accurately evaluate properties of subsurface oil, gas and/or water reservoirs. 
     There continues to be a need for improved coring devices and methods that better assure core recovery and core condition. 
     SUMMARY OF THE INVENTION 
     A core sample acquisition device according to one aspect of the invention includes a core receiving barrel configured to couple to a drill string proximate a core drilling bit. The device includes a sensor for measuring a property of a core sample urged into the receiving barrel by drilling the core sample. The sample acquisition device includes a communication device for transmitting signals from the sensor over at least one of an electrical and an optical communication channel associated with the drill string. 
     A method for acquiring a core sample according to another aspect of the invention includes drilling a core sample. The core sample is urged into a receiving barrel during the drilling of the core sample. A parameter related to a property of the core sample disposed in the receiving barrel is measured during the drilling of the core sample. The measured parameter is communicated to the Earth&#39;s surface using at least one of an electrical and optical communication channel in a drill string. 
     Other aspects and advantages of the invention will be apparent from the following description and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an example drilling system including an example of a core recovery device according to the invention. 
         FIG. 2  shows an example core acquisition and storage device in more detail. 
         FIG. 3  shows an example of a core bit. 
     
    
    
     DETAILED DESCRIPTION 
     An example wellbore drilling system is shown in  FIG. 1  and includes an example of a formation sample (“core”) acquisition and storage device according to the invention. A drilling rig  24  or similar lifting device suspends a conduit called a “drill string  20 ” within a wellbore  18  being drilled through subsurface Earth formations  11 . The drill string  20  may be assembled by threadedly coupling together end to end a number of segments (“joints”)  22  of drill pipe. The drill string  20  may include a formation sample-taking drill bit  12  (“coring bit”) at its lower end. A coring bit typically includes cutting elements that drill an annular hole through the subsurface formations, leaving an uncut, centrally disposed cylinder of formation as a result of drilling. One example of a coring bit is described in U.S. Pat. No. 6,412,575 issued to Harrigan et al. and assigned to the assignee of the present invention. See also U.S. Pat. No. 5,460,230 issued to Dekoster. Particular features of the drill bit  12  will be further explained with reference to  FIG. 2 , however, the configuration of the drill bit  12  other than its capability to drill a core sample is not a limit on the scope of this invention. 
     When the (frill bit  12  is axially urged into the formations  11  at the bottom of the wellbore  18  by the applying some of the weight of the drill string  20 , and when it is rotated by equipment (e.g., top drive  26 ) on the drilling rig  24 , such urging and rotation causes the bit  12  to axially extend (“deepen”) the wellbore  18  by drilling the formations  11 . As explained above and as will be further explained with reference to  FIG. 2 , such drilling may enable acquiring a sample of the formations  11  as a result of such drilling. The lower end of the drill string  20  may include, at a selected position above and typically proximate to the drill bit  12 , a core sample acquisition and storage unit  10 . The core sample acquisition and storage unit  10  may include one or more sensors ( FIG. 2 ) for measuring selected properties of a formation core sample ( FIG. 2 ) passed therethrough by the action of the dill bit  12 . The one or more sensors ( FIG. 2 ) in the sample storage unit  10  may be coupled to a telemetry transmitter or transceiver ( FIG. 2 ) to communicate the measurements made thereby to the Earth&#39;s surface along an electrical and/or optical conductor (not shown separately) in the drill string  20 . Proximate its lower end of the drill string  20  may also include an MWD instrument  14  and an LWD instrument  16  of types well known in the art. 
     During drilling of the wellbore  18 , a pump  32  lifts drilling fluid (“mud”)  30  from a tank  28  or pit and discharges the mud  30  under pressure through a standpipe  34  and flexible conduit  35  or hose, through the top drive  26  and into an interior passage (not shown separately in  FIG. 1 ) inside the drill string  20 . The mud  30  exits the drill string  20  through courses or nozzles ( FIG. 2 ) in the drill bit  12 , where it then cools and lubricates the drill bit  12  and lifts drill cuttings generated by the drill bit  12  to the Earth&#39;s surface. Some examples of MWD instrument  14  or LWD instrument  16  may include a telemetry transmitter (not shown separately) that modulates the flow of the mud  30  through the drill string  20 . Such modulation may cause pressure variations in the mud  30  that may be detected at the Earth&#39;s surface by a pressure transducer  36  coupled at a selected position between the outlet of the pump  32  and the top drive  26 . Signals from the transducer  36 , which may be electrical and/or optical signals, for example, may be conducted to a recording unit  38  for decoding and interpretation using techniques well known in the art. The decoded signals typically correspond to measurements made by one or more of the sensors (not shown) in the MWD instrument  14  and/or the LWD  16  instrument, and may, in some examples, include measurements made by the storage unit  10 . In the present example, such mud pressure modulation telemetry may be used in conjunction with, or as backup for an electromagnetic telemetry system included in “wired” drill pipe. 
     An electromagnetic transmitter (not shown separately) may be included in the either or both the sample storage unit  10  and LWD instrument  16 , and may generate signals that are communicated along electrical conductors in the wired drill pipe. One type of “wired” drill pipe, as mentioned above in the Background section herein, is described in U.S. Patent Application Publication No. 2006/0225926 filed by Madhavan et al. and assigned to the assignee of the present invention. A wireless transceiver sub  37 A may be disposed in the uppermost part of the drill string  20 , typically directly coupled to the top drive  26 . The wireless transceiver  37 A may include communication devices to wirelessly transmit data between the drill string  20  and the recording unit  38 , using a second wireless transceiver  37 B associated with the recording unit. 
     It will be appreciated by those skilled in the art that the top drive  26  may be substituted in other examples by a swivel, kelly, kelly bushing and rotary table (none shown in  FIG. 1 ) for rotating the drill string  20  while providing a pressure sealed passage through the drill string  20  for the mud  30 . Accordingly, the invention is not limited in scope to use with top drive drilling systems, but may be used with any type of rotary drilling system. 
     In the example shown in  FIG. 1 , equipment (not shown separately) in the recording unit  38  may transmit command or control signals to the storage unit  10  using) the one or more electrical conductors (not shown separately) in the drill string  20 . Operation of the core acquisition and storage unit  10  in response to such command or control signals will be further explained below. 
     One example of a core acquisition and storage unit is shown in more detail in  FIG. 2 . The core acquisition and storage unit  10  may be disposed in a generally cylindrical housing  10 A configured to be coupled within the drill string ( 20  in  FIG. 1 ), typically directly adjacent to the drill bit ( 12  in  FIG. 1 ). A core sample of the formation formed by the drill bit ( 12  in  FIG. 1 ) as the wellbore is drilled is urged longitudinally into a core barrel  40 , which may be rotatably mounted inside the housing  10 A. The core barrel  40  may be in the form of a sleeve  40 A that is rotatably and sealingly mounted inside the housing  10 A to enable acquiring and retaining core samples while rotary drilling processes. One non-limiting example of a core drilling bit and a core barrel that may be used in various implementations is described in U.S. Pat. No. 7,124,841 issued to Wada et al. and incorporated herein by reference. It should be clearly understood that the foregoing example is only one possible implementation of a core drilling bit and a core receiving barrel, and therefore such example is not a limit on the scope of the present invention. Another example configuration of core barrel and core drilling bit is disclosed in U.S. Pat. No. 7,168,508 issued to Goldberg et al. A particularly useful feature of the device disclosed in the Goldberg et al. patent is that the core barrel is longitudinally disposed in approximately the same position along the drill string ( 20  in  FIG. 1 ) as certain sensors in the LWD instrument ( 14  in  FIG. 1 ). Such feature can enable more precise determination of where a core sample is desired to be obtained. 
     Initially, before any core sample is urged into the core barrel  40 , a core receiving and ejecting piston  46  disposed in and cooperatively arranged with the core barrel  40  may be disposed toward the lower end of the core barrel  40 . Such extension may be performed, for example, by a combination of ejector piston  48  disposed in an ejector cylinder  48 A longitudinally above the core barrel  40 . The ejector piston  48  may be coupled to the receiving and ejector piston  46  by a rod or link  50  coupled between the two pistons  46 ,  48 . A solenoid operated hydraulic valve  56  may admit hydraulic fluid such as oil under pressure into the ejector cylinder  48 A to urge the ejector piston  48  downwardly. Such motion is communicated to the receiving and ejecting piston  46  by the link  50 . Corresponding downward motion of the receiving and ejecting piston  46  ejects the core sample through the central opening in the drill bit ( 12  in  FIG. 1 ) when so desired by the system operator. Conversely, as a core sample is urged longitudinally into the core barrel  40  during drilling, such core sample urges the receiving and ejecting piston  46  to move upwardly and consequently to move the ejector piston  48  into its cylinder  48 A. The solenoid valve  56  may be configured to enable, during such core sample acquisition, release of hydraulic fluid from the cylinder  48 A through a selected orifice (not shown) so as to cause the receiving and ejecting piston  46  to maintain a selected axial pressure on the top of the core sample (not shown). Such pressure may provide that the longitudinal position of the receiving and ejecting piston  46  is substantially related to the amount of core sample filling the core barrel  40 . As will be explained below, such positional relationship may be used in some examples to provide a signal indicative of when a core sample fully fills the core barrel  40 . In such circumstances, the system operator may elect to retrieve the core acquisition unit  10  from the wellbore, or may elect to eject the core sample from the core barrel  40 . In other examples, the core barrel  40  may be retrievable without removing the drill string ( 20  in  FIG. 1 ) from the wellbore, and the system operator may retrieve the core sample by retrieval of the core sample-filled core barrel  40 . 
     The ejector piston  48  may be made from, include or have associated therewith a magnetic material or a magnetically permeable material, so that its longitudinal position along the cylinder  48 A may be determined using a pickup coil  52  or similar device to locate the longitudinal position of the ejector piston  48 , and thus determine the longitudinal position of the receiving and ejecting piston  46 . The pickup coil  52  may be arranged, for example, in the form of a linear variable differential transformer (LVDT). An LVDT generates a signal, when excited by alternating current, that is related to the longitudinal position of a magnetically permeable material with respect to the LVDT coil. Other devices for determining longitudinal position of the ejector piston  48  will occur to those of ordinary skill in the art. It should also be clearly understood that a longitudinal position determining sensor may also be or may alternatively be associated with or functionally coupled to the receiving and ejecting piston  46 . 
     As is known in the art, some core samples are susceptible to falling out of the core barrel during or after acquisition. In the present example, to address such problem, a core sample may be held in place inside the core barrel  40  by suitably shaped retaining clamps or shoes  44  that are urged laterally inwardly to compress the core sample. Actuation of the shoes  44  may be performed by hydraulic cylinders  60 . The hydraulic cylinders  60  may be actuated by solenoid valves  58 . The solenoid valves  58  may be coupled to a source of hydraulic oil under pressure (not shown) just as the hydraulic valve  56  used to operate the ejector piston  48 . 
     The core barrel  40  in some examples may include features (not shown separately) to enable retrieval of the core barrel  40  from inside the drill string ( 20  in  FIG. 1 ) using a cable such as wireline of slickline, or coiled tubing or similar conveyance. After a core barrel having a core sample therein is retrieved, the same or a different core barrel may be reinserted into the drill string ( 20  in  FIG. 1 ) and placed within it intended position the housing  10 A. After replacement of the core barrel as described above, the process of drilling, evaluating and/or retrieving a core sample may be repeated if desired by the system operator. 
     A full diameter ball valve  42  or similar device may be included in some examples in order to selectively close and seal the bottom end of the core barrel  40 , to retain the core and to maintain fluid pressure therein at essentially the fluid pressure existing in the wellbore at the place from which the core sample was taken. Closing such ball valve  42  can seal the core barrel  40  to prevent loss of fluid pressure. The ball valve may be actuated by a solenoid valve  58 . 
     Operation of the foregoing solenoid valves  56 ,  58  may be performed by a controller  54 , which may be any suitable microprocessor based controller. The controller  54  may include or may be associated with telemetry circuits (not shown separately) for transferring command signals and data over the wired drill pipe conductor(s) (in the drill string  20  in  FIG. 1 ). Thus, all of the functions explained above with reference to measuring the position of a core sample within the core barrel  40 , with ejecting the core sample from the core barrel  40 , clamping the core sample in place in the core barrel  40 , and ejecting the core sample from the core barrel  40  may be performed by the operator at the surface by sending suitable commands over the wired drill pipe (pipe string  20  in  FIG. 1 ) to the controller  54 , which may operate the appropriate hydraulic valves  56 ,  58 . 
     Deciding whether to retain or eject a particular core sample may be facilitated by including one or more sensors  62  proximate an entry end of the core barrel  40 . The sensors  62  may be any type known in the art, including, by way of example and without limitation, electrical resistivity, acoustic velocity, density, neutron slowing down length (porosity) and/or capture cross-section; natural gamma radiation and/or neutron activated gamma radiation. The measurements made by the various sensors  62  may be communicated to the surface using the conductor(s) in the wired drill pipe (drill string  20  in  FIG. 1 ). The system operator may have opportunity to evaluate the measurements communicated from the sensors  62 , and decide on the basis of such measurements whether the particular core sample should be retained or should be ejected. In the latter case, as explained above, the hydraulic valve  56  may be operated to move the ejector piston  48  downwardly to eject the core sample. The ejected core sample may be ground up by action of the drill bit ( 12  in  FIG. 1 ) thereon. Core acquisition may resume at a place of the system operator&#39;s choosing. If the system operator elects to retain the particular core sample, suitable commands may be communicated along the conductor(s) in the wired drill pipe so that either or both the ball valve  42  is closed and the shoes  44  are moved inwardly. 
     An example core bit that may be controlled using wired drill pipe (e.g., drill string  20  in  FIG. 1 ) is shown schematically in  FIG. 3 . The drill bit  12  in the present example may be selectively configured to drill ordinary well hole when cores are not desired, and selectively configured to drill core samples when so desired. Such core bit  12  may be advantageously used in conjunction with the core acquisition and storage device shown in  FIG. 2 . The bit  12  in this example may include a bit body  12 A formed from steel, or from powdered metal carbide (e.g., tungsten carbide) in a binder alloy. Cutting elements  12 B such as polycrystalline diamond compact (PDC) cutters may be affixed to the bit body  12 A in selected positions such that rotation of the bit body  12 A causes cutting of the formations in the wellbore. A central passageway  80  in the bit body is configured to receive core samples therein as the bit  12  drills the subsurface formations. The passageway may be generally axially aligned with the core barrel ( 40  in  FIG. 2 ). 
     A closure plug  74  having one or more cutting elements  12 B on it end face, may be disposed in a bypass passage  70  that connects to the central passage  80 . The closure plug  74  may be coupled to an hydraulic ram  72  by a link  76 . The ram  72  may be extended and retracted along the bypass passage by admitting or releasing hydraulic pressure, such as by a solenoid operated valve  58 A. Such solenoid operated valve  58 A may be in signal communication with the controller ( 54  in  FIG. 2 ). A hinge mounted door  78  may close the bypass passage  70  when the closure plug  74  is retracted therein. When the hydraulic ram  72  is extended, the closure plug  74  may be moved into the central opening out to the lowermost surface of the bit body  12 A. When the plug  74  is in such position, the bit  12  is configured as an ordinary drill bit that drills the entire cross sectional area of the face of the bit. When the plug is retracted (as shown in  FIG. 3 ), the bit  12  acts in the manner of a core bit. Thus, when measurements made by the various sensors explained with reference to  FIG. 1  and  FIG. 2  suggest that it is desirable to acquire a core sample, the system operator may cause the surface equipment to transmit a command along the conductor in the drill string ( 20  in  FIG. 1 ), which may be decoded by the controller ( 54  in  FIG. 2 ) to cause the solenoid valve  58 A to operate to retract the plug  74 . When ordinary drilling is to resume, the above procedure may be reversed. Such configuration of a bit as shown in  FIG. 3  may reduce the need to “trip” the drill string ( 20  in  FIG. 1 ) to change bits from a core bit to a conventional full cross section bit. Such configuration may also eliminate the need to insert specialized tools into the interior of the drill string to effect closure of the drill bit. See, for example U.S. Pat. No. 6,269,891 issued to Runia as illustrative of bit closures known in the art prior to the present invention. 
     A core sample acquisition device according to the various aspects of the invention may increase the efficiency of coring operations by providing analysis of the suitability of the core sample during acquisition and the capability of ejecting the core sample and acquitting an additional sample in the event the acquired sample is unsuitable. A core sample acquisition device according to the invention may provide more positive indication of when a core sample is fully acquired, so that unnecessary “tripping” of drill string from the wellbore, where a core sample is incompletely acquired, is reduced. 
     While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.