Patent Publication Number: US-10316654-B2

Title: Coring tools and related methods

Description:
RELATED APPLICATIONS 
     This application is continuation application of and claims priority to U.S. patent application Ser. No. 14/089,313, entitled “CORING TOOLS AND RELATED METHODS,” now U.S. Pat. No. 9,410,423, which was a divisional of and claimed priority to U.S. patent application Ser. No. 13/433,788, entitled “CORING TOOLS AND RELATED METHODS,” now U.S. Pat. No. 8,613,330, which claims the benefit of the filing date of U.S. Provisional Application No. 61/504,635, filed on Jul. 5, 2011, the entire disclosures of which are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     Wellbores or boreholes may be drilled to, for example, locate and produce hydrocarbons. During a well development operation, it may be desirable to evaluate and/or measure properties of encountered formations, formation fluids and/or formation gasses. Some formation evaluations may include extracting a core sample (e.g., a rock sample) from sidewall of a wellbore. Core samples may be extracted using a coring tool coupled to a downhole tool that is lowered into the wellbore and positioned adjacent a formation. A hollow coring shaft or bit of the coring tool may be extended from the downhole tool and urged against the formation to penetrate the formation. A formation or core sample fills the hollow portion or cavity of the coring shaft and the coring shaft is removed from the formation retaining the sample within the cavity. The formation or core sample may then be removed from the coring shaft for further evaluation at, for example, a laboratory. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. 
         FIG. 1A  is a schematic view of coring apparatus according to one or more aspects of the present disclosure. 
         FIG. 1B  is a schematic view of another coring apparatus according to one or more aspects of the present disclosure. 
         FIG. 2  is a schematic view of a coring apparatus according to one or more aspects of the present disclosure. 
         FIG. 3  is a perspective view of a coring apparatus according to one or more aspects of the present disclosure. 
         FIGS. 4A and 4B  depict a known coring shaft or bit. 
         FIG. 5A  is a sectional view of a coring shaft according to one or more aspects of the present disclosure. 
         FIG. 5B  is an end view of the coring shaft of  FIG. 5A . 
         FIG. 6  is a sectional view of another coring shaft according to one or more aspects of the present disclosure. 
         FIG. 7  is a sectional view of another coring shaft according to one or more aspects of the present disclosure. 
         FIGS. 8A-8C  depict inner surfaces for coring shafts according to one or more aspects of the present disclosure. 
         FIG. 9  is flowchart diagram of at least a portion of a method according to one or more aspects of the present disclosure. 
         FIG. 10  is a flow chart diagram of at least a portion of another method according to one or more aspects of the present disclosure. 
         FIG. 11  is a sectional view of a coring tool according to one or more aspects of the present disclosure. 
         FIG. 12  is a sectional view of another coring tool according to one or more aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     It is to be understood that the following disclosure provides many different embodiments or examples for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the present disclosure. These are merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact. Embodiments in which additional features may be formed interposing the first and second features such that the first and second features may not be in direct contact may also be included. 
     The example apparatus and methods described herein relate to coring tools and coring bits or shafts that may be used to collect samples (e.g., rock samples, tar sand samples, etc.) from subterranean formations adjacent a borehole or a wellbore. The example coring shafts described herein may be used in conjunction with sidewall coring apparatus and methods. The example coring shafts generally include a cylindrical body having a leading edge to contact and penetrate a subterranean formation to be sampled. The cylindrical body has a cavity defined at least in part by an inner surface of the cylindrical body. Additionally, the inner surface of the cylindrical body may include a plurality of raised features to engage and retain a sample from the formation. The raised features may be shaped so that the raised features deform and/or an exterior surface of the sample in the cavity deforms, thereby increasing an amount of force required to remove the sample from the cavity. In this manner, the raised features of the inner surface of the example coring shafts may become at least partially embedded in a sample captured within the cavity. As a result, the example coring shafts or bits described herein may provide a substantially greater amount of sample retention force compared to many known coring bits or shafts. 
     The example coring shafts described herein may use one or more types of raised features and/or surface treatments. For example, knurls or a knurled surface, a helical ridge, a spiraled ridge, threads, serrations and/or axial ridges may be used. Such raised features are shaped to provide portions or areas of relatively greater stress or force concentration against a formation or core sample and, thus, may be capable of causing the above-mentioned deformation(s). Additionally, different leading edge configurations may be used to implement the example coring shafts including, for example, bevels, lips, wedges and/or a diamond cutter to suit a particular application or applications. 
     In another aspect, the example coring shafts described herein may employ a circumferential groove or grooves on an exterior surface of the cylindrical body of the coring shaft to provide a relatively weakened portion or area on the coring shaft. In particular, the groove or grooves may result in at least a portion of a wall of the coring shaft having a reduced thickness sufficient to cause the cylindrical body to fracture and shear off in response to a predetermined load, torque, or force, thereby facilitating withdrawal of a coring tool from a sidewall of a borehole despite the coring shaft becoming stuck in the sidewall. 
     The example methods described herein may involve selecting a coring shaft type for use in sampling a formation based on a property of the formation. For example, in the case where the formation property relates to formation strength or formation lithology (e.g., tar sand), such a property or properties may be used to select a coring shaft having a relatively larger diameter or a relatively smaller diameter. The property of the formation may also result in selection of a coring shaft having a particular leading edge configuration such as, for example, a wedge or a diamond cutter configuration. The example methods may be employed with the example coring shaft or bits described herein or any other coring shafts or bits. 
     In another aspect, the example methods described herein may involve selecting an operational mode(s) for a coring tool based on a property or properties of a formation to be sampled. More specifically, the lithology of a formation may be used to select a punching or drilling operational mode for the coring tool and/or selecting whether each coring shaft of the coring tool is to collect one or multiple formation samples. Thus, the example methods noted above and described in more detail below can be used to enhance or optimize a coring operation through the selection of a particular coring shaft or bit configuration and/or a manner in which the coring tool is to be operated for use with a formation having particular properties. 
       FIG. 1A  depicts a coring tool  10  with which the example methods and coring shaft or bit apparatus described herein can be used. As shown, the coring tool  10  may be used in a drilled well to obtain core samples from a downhole or subterranean geologic formation. In operation, the coring tool  10  is lowered into a borehole  11  defined by a bore wall  12 , commonly referred to as the sidewall. The coring tool  10  is connected by one or more electrically conducting cables  16  to a surface unit  17  that includes a control panel  18  and a monitor  19 . The surface unit  17  is designed to provide electrical power to the coring tool  10 , to monitor the status of downhole coring and activities of other downhole equipment, and to control the activities of the coring tool  10  and other downhole equipment. 
     The coring tool  10  is generally contained within an elongate housing suitable for being lowered into and retrieved from the borehole  12 . The coring tool  10  may include an electronic sonde  51 , a mechanical sonde  53 , and a core magazine  55 . The mechanical sonde  53  contains a coring assembly including at least one motor  44  powered through the cables  16 , a coring bit or shaft  24  having a distal, open end  26  for cutting and receiving a core sample from a formation  46 , and a mechanical linkage (not shown) for deploying and retracting the coring shaft  24  relative to the coring tool  10  and for rotating the coring shaft  24  against the sidewall  12 . 
       FIG. 1A  shows the coring tool  10  in an active, cutting configuration. The coring tool  10  is positioned adjacent the formation  46  and urged firmly against the sidewall  12  by anchoring shoes  28  and  30 , which are extended from a side of the coring tool  10  opposing the coring shaft  24 . The distal, open end  26  of the coring shaft  24  may be rotated via the motor  44  against the formation  46  to cut a core sample from the formation  46 . 
       FIG. 1B  shows the general features of another type of coring tool  1121  with which the example methods and apparatus described herein can be used. This coring tool  1121  includes a plurality of coring shafts  1123 ,  1124 ,  1125 ,  1126 , each of which may be used to collect and store a single formation sample. 
     While  FIGS. 1A and 1B  show coring tools deployed at the end of a wireline cable, a coring tool may be deployed in a well using any known or future-developed conveyance means, including drill pipe, coiled tubing, etc. 
       FIG. 2  is a schematic view of an example mechanical sonde, such as the mechanical sonde  53  of  FIG. 1A . As shown in  FIG. 2 , the mechanical sonde  53  includes a coring assembly having the coring bit or shaft  24  and a housing  42 . To cut a core sample from the formation  46  with the coring shaft  24 , the mechanical sonde  53  uses a thrusting actuator to urge (e.g., punch, press, drive, etc.) the coring shaft  24  into the formation  46  and applies a weight-on-bit (WOB), which is a force that urges the coring shaft  24  into the formation  46 . The mechanical sonde  53  may include a rotating actuator to apply a torque to rotate the coring shaft  24 , thereby drilling the coring shaft  24  into the formation  46 . 
     For example, the WOB provided by the mechanical sonde  53  and applied to the coring shaft  24  may generated by an electric motor  62  and a control assembly  61  that includes a hydraulic pump  63 , a feedback flow control (“FFC”) valve  64 , and a kinematics piston  65 . The electric motor  62  supplies power to the hydraulic pump  63 . The flow of hydraulic fluid from the hydraulic pump  63  is regulated by the FFC valve  64 , and the pressure of hydraulic fluid drives the kinematics piston  65  to apply a WOB to the coring shaft  24 . The FFC valve  64  may regulate the flow of hydraulic fluid to the kinematics piston  65  based on the hydraulic pressure applied to a hydraulic coring motor  44 . Also, for example, to rotate the coring shaft  24 , torque may be provided by an electric motor  66  and a gear pump  67 . The electric motor  66  drives the gear pump  67 , which supplies flow of hydraulic fluid to the hydraulic coring motor  44 . The hydraulic coring motor  44 , in turn, imparts a torque to the coring shaft  24  that causes the coring shaft  24  to rotate. 
       FIG. 3  shows a perspective view of an example coring apparatus, such as the apparatus including the coring shaft  24 , the housing  42  and the hydraulic motor  44  of  FIGS. 1A and 2 , when the coring apparatus is cutting or has cut into the formation  46 . A core sample  48  may be received into a hollow interior or cavity of the coring shaft  24  as cutting progresses. 
       FIGS. 4A and 4B  depict a partial side view and an end view of a known coring shaft or bit. More specifically, the coring bit of  FIGS. 4A and 4B  is a surface set diamond bit. A more detailed description of such a coring bit can be found in U.S. Pat. No. 4,189,015, the disclosure of which is hereby incorporated by reference herein in its entirety. The known coring shaft or bit shown in  FIGS. 4A and 4B  typically provides an internal cavity diameter of between about 1 and 1.5 inches, which may be substantially smaller than the examples described below in connection with  FIGS. 5-7 . 
       FIGS. 5A and 5B  show a sectional view and an end view of an example coring bit or shaft  500  according to aspects of this disclosure. The example coring shaft  500  has a generally cylindrical body  502  having a leading edge  504  to contact and penetrate a formation (e.g., the formation  46 ). The cylindrical body  502  includes a cavity  506  that is defined at least partially by an inner surface  508  of the cylindrical body  502 . The inner surface  508  is to engage and facilitate the retention of a core sample cut from a formation. For example, a substantial portion of the inner surface  508  may have a surface treatment such as a plurality of raised features  510 . 
     Turning briefly to  FIGS. 8A, 8B and 8C , various types of surface treatments or example implementations of the raised features  510  are shown.  FIG. 8A  depicts a knurled surface or knurls  800 ,  FIG. 8B  depicts a spiraled ridge, a helical ridge or threads  802 , and  FIG. 8C  depicts axial ridges or serrations  804 . The axial ridges or serrations of  FIG. 8C  may have an asymmetrical profile. In the case of the example of  FIG. 8B , the threads may have a pitch of twelve threads per inch and have a v-groove profile about 0.1 inch deep. The threads may span about 1.4 inches and may be left or right-handed. However, other pitches, dimensions and spans may be used without departing from the scope of the present disclosure. 
     Returning to  FIG. 5A , the raised features  510  are shaped to increase a stress concentration or force at the points of contact between the raised features  510  and a sample within the cavity  506 . Such increased stress and/or force may deform an exterior surface of the sample and/or may deform the raised features, depending on the relative hardness of the sample and the material from which the raised features  510  are formed. In any event, such deformation may result in the raised features becoming at least partially embedded within the sample or at least creating a increased amount of mechanical interference contact between the sample and the inner surface  508 , thereby substantially increasing the force applied to remove the sample from the cavity  506 . 
     The leading edge  504  of the coring shaft  500  may be urged into a formation via a thrusting, punching or pressing operation using, for example, WOB provided by the electric motor  62 , the control assembly  61 , the hydraulic pump  63 , the FFC valve  64 , and the kinematics piston  65  as discussed above in connection with  FIG. 2 . In that case, the leading edge  504  may include a bevel, a lip or a wedge-shaped profile. In the example of  FIG. 5A , the leading edge has a taper angle  512 , which may, for example, be about ten degrees. However, the taper angle  512  may be selected to suit a particular application. The leading edge  504  may also be rotated or drilled into a formation. For example, the leading edge  504  may include a diamond cutter bit similar to that shown in  FIGS. 4A and 4B . 
     The inner surface  508 , including the innermost surfaces or edges of any surface treatment thereon, may be tapered over at least a portion  514 . This taper may be about two degrees or any other taper angle to enable removal of the sample from the cavity  506 . 
     In contrast to many known coring shafts, the example coring shaft  500  may provide a relatively large formation sample. For example, the cavity  506  may have a diameter of approximately two inches and a length of approximately two inches. However, other diameters and lengths can be used without departing from the scope of this disclosure. 
     The cylindrical body  502  has a wall having reduced thickness portion  516  to cause the cylindrical body  502  to fracture or shear (at the portion  516 ) in response to a predetermined load (e.g., torque, force, etc.). The portion  516  may be formed as a continuous circumferential groove as depicted in  FIG. 5A  or may be an interrupted (i.e., discontinuous) groove, a plurality of holes or thinned sections, or any other configuration that serves to provide a relatively weaker portion of the cylindrical body  502 . In this manner, in the event that the cylindrical body  502  of the coring shaft  500  becomes stuck in a sidewall, the coring tool carrying the coring shaft  500  (e.g., the coring tool  10  of  FIG. 1A ) can impart a sufficient load to shear off the cylindrical body  502  at the reduced thickness portion  516 , thereby enabling removal of the coring tool. 
     The example coring shaft  500  also includes an end  518  that enables the coring shaft  500  to be removably coupled to a thrusting actuator (see one example in  FIG. 2 ) and optionally a rotating actuator (see one example in  FIG. 2 ). 
       FIGS. 6 and 7  are sectional views of alternative example coring shafts  600  and  700  that may be used with a coring tool such as the coring tool  10  of  FIG. 1A . The example coring shaft  600  of  FIG. 6  has a leading edge configuration having a lip  602  and the example coring shaft  700  of  FIG. 7  has a catcher ring type leading edge  702 . The lip  602  and the leading edge  702  shown in  FIGS. 6 and 7 , respectively, may be used to provide a space or gap between an outer surface of a drill shaft and the inner surface of a wellbore. Such a gap or space may be used to enable a drill motor to rotate about an axis perpendicular to the longitudinal axis of the wellbore (e.g., cock) at its end of travel to snap off the core. 
     The example coring shafts described herein may be used in conjunction with the example method  900  of  FIG. 9 . Initially, a formation evaluation tool (e.g., the coring tool  10  or a downhole tool coupled to the coring tool  10 ) is positioned in a borehole adjacent a subterranean formation (e.g., the formation  46 ) (block  902 ). One or more properties of the formation are then determined (block  904 ). For example, a strength of the formation, a lithology of the formation (e.g., tar sand), and/or other properties may be determined at block  904 . A coring shaft type is then selected based on the one or more properties determined at block  904  (block  906 ). For example, the example coring shafts of  FIGS. 5-7  may be used to obtain samples from formations having an unconsolidated compressive strength that is less than 500 pounds per square inch and/or tar sand formations. The coring shaft selected at block  906  may also be selected based on whether the formation property (or properties) is defined within a value set. Such a value set may include particular target properties and/or formations that have been identified as being of particular interest for development. 
     Once the coring shaft type has been selected at block  906 , a coring shaft having the selected type is coupled to a coring tool (block  908 ). The coring shaft coupled to the coring tool may be selected from a plurality of coring shafts stored in the coring tool or a portion of a downhole tool carrying the coring tool. The coring shafts may have different diameters and/or leading edges for use with different types of formations. For example, any or all of the coring shafts described here may be used. In cases where multiple coring shafts are kept at the surface, the formation evaluation tool may be withdrawn from the borehole and an appropriate one of the coring shafts (e.g., selected based on the property) may be attached to the coring tool. The coring tool may then be lowered into the borehole. Once the selected coring shaft has been coupled to the coring tool at block  908 , the coring tool may then obtain a sample (for transport back to the Earth&#39;s surface) from the formation using the selected coring shaft (block  910 ). 
     The example coring shafts described herein may also be used in conjunction with the example method  1000  of  FIG. 1000 . Initially, a formation evaluation tool (e.g., the coring tool  10  or a downhole tool coupled to the coring tool  10 ) is positioned in a borehole adjacent a subterranean formation (e.g., the formation  46 ) (block  1002 ). One or more properties of the formation are then determined (block  1004 ). A coring operational mode is then selected based on the one or more properties determined at block  1004  (block  1006 ). For example, a punching or thrusting operational mode (i.e., where the coring shaft is pushed into the formation) may be selected where the one or more properties indicate a relatively soft formation. Any one of the example coring shafts of  FIGS. 5-7  may, for example, be used in conjunction with a punching or thrusting operational mode. On the other hand, a drilling mode may be selected at block  1006  where the one or more properties indicate a relatively hard formation. In that case, the diamond cutter shaft/bit of  FIGS. 4A and 4B  may be used. Still further, the operational mode selected at block  1006  may involve determining that one formation sample is to be collected with each or a particular coring shaft or, alternatively, determining that multiple samples are to be collected with each or a particular coring shaft. Once the operational mode has been selected at block  1006 , the coring tool may then obtain a sample (for transport back to the Earth&#39;s surface) from the formation using the selected operational mode (block  1008 ). 
     While in the methods  900  and  1000 , the coring shafts are used to obtain samples from a subterranean formation adjacent a borehole, the example coring shafts described herein may also be used to acquire other types of samples, such as soil samples, ice samples, or samples of materials used in masonry. 
     The example of  FIG. 11  shows a portion of a sectional view of a coring tool. An outer hollow coring shaft  460  is to extend through a wall of a wellbore penetrating a subterranean formation. A rotationally uncoupled internal sleeve  464  is disposed inside the outer hollow coring shaft  460 . U.S. Pat. No. 7,431,107, the entire disclosure of which is hereby incorporated by reference herein, describes a manner in which a sleeve may be rotationally uncoupled within a coring tool. An inner surface of the internal sleeve  464  includes any of the surface treatments or raised features described herein (e.g.,  FIGS. 8A-8C ). 
     The embodiment of  FIG. 12  shows a portion of a sectional view of a coring tool. The coring tool comprises a plurality of core holders to retain samples from a subterranean formation penetrated by a borehole, for example as described in U.S. Patent Application Pub. No. 2009/0114447, the entire disclosure of which is hereby incorporated by reference herein. As shown, a hollow coring shaft  300  is to receive one of the plurality of core holders, such as core holder  308 . An inner surface of the core holder  308  includes any of the raised features described herein (e.g.,  FIGS. 8A-8C ). 
     In view of the foregoing description and the figures, it should be clear that the present disclosure introduces coring apparatus and methods to use the same. According to certain aspects of this disclosure, an example apparatus includes a coring tool to obtain a sample. The coring tool includes a cylindrical body having a leading edge to and a cavity defined at least in part by an inner surface of the cylindrical body. The inner surface is to engage and retain a sample with a plurality of raised features, and the raised features are shaped so that at least one of the raised features or an exterior surface of a sample in the cavity deforms to increase a force required to remove the sample from the cavity. 
     According to other aspects of this disclosure, a method involves disposing a coring tool in a borehole adjacent a subterranean formation to be sampled, determining a property of the formation, selecting a coring shaft type based on the property, coupling a coring shaft having the selected type to the coring tool, and obtaining a sample from the formation using the coupled coring shaft. 
     According to other aspects of this disclosure, a method involves disposing a coring tool in a borehole adjacent a subterranean formation to be sampled, determining a property of the formation, selecting a coring tool operational mode based on the property, and obtaining a sample from the formation using the coring tool operational mode 
     The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure. 
     The Abstract at the end of this disclosure is provided to comply with 37 C.F.R. § 1.72(b) to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.