Abstract:
Methods and apparatus for evaluating a formation include conveying a formation evaluation tool in a borehole on a tubular carrier extending from a surface location at least to the formation evaluation tool. A cable is conveyed to the formation evaluation tool and communication between the formation evaluation tool and the cable is established after the formation evaluation tool is moved to a selected borehole location.

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure generally relates to formation evaluation and in particular to methods and apparatus for formation evaluation after drilling. 
     2. Background Information 
     Oil and gas wells have been drilled at depths ranging from a few thousand feet to as deep as 5 miles. Wireline and drilling tools often incorporate various sensors, instruments and control devices in order to carry out any number of downhole operations. These operations may include formation testing and monitoring and tool monitoring and control. 
     Typical well development includes a primary drilling system that drills the well through one or more producing formations to a total depth (“TD”). Formation evaluation tools used in a while-drilling arrangement provide some information relating to the traversed formations, but relatively slow transmission methods during drilling result limitations on the information available in real time. As a result, the knowledge gained from while-drilling tools provides at best a rough estimate as to the content and production ability of the formations. Furthermore, the primary drilling operation is extremely harsh on sensitive test instruments and protecting some of the more sensitive instruments from the shock and vibration environment experienced during primary drilling is expensive and sometimes limited by the space requirements in the drill string. Completion operations and the design of production processing facilities at the well head require information about the producing formations that is more precise and complete than provided by current while-drilling formation evaluation tools. 
     Wireline systems are sometimes used after primary drilling operations are complete at least through a suspected producing zone or zone of interest to gather more information about the zone of interest in order to better design the completion operations and surface processing facilities. The drill string is tripped and the wireline is run into the well to the zone of interest. The wireline tool provides a communication cable to the surface that provides information transmission rates higher than mud pulse telemetry and other while-drilling transmission methods. Wireline systems, however, cannot be conveyed into ultra-deep wells (up to 30,000 feet and more) without running the risk of losing the tool in the borehole due to strength limitations of the supporting cable. A broken wireline cable and lost tool may cost millions of dollars in lost time, lost equipment and the cost of drilling a bypass borehole. 
     Pipe-conveyed logging (“PCL”) tools are sometimes used to convey a formation evaluation tool in wells too deep for conventional wireline tools. A PCL tool includes a cable like a wireline tool, but the weight of the PCL tool is supported by a pipe allowing deeper penetration. Using a pipe also provides the ability to push the PCL tool in boreholes deviated from vertical. These PCL tools suffer in that the sensitive instruments can be damaged or destroyed if the operator pushes the pipe too hard through a well borehole zone that is of poor dimensional quality. Therefore, the PCL tool is typically lowered or pushed very slowly, which is a time cost. Even when the pipe is lowered slowly, an obstruction may still exist in the pre-drilled borehole. The operator must choose between tripping the PCL tool and increasing the weight on the pipe to force the pipe through the obstruction. There is a risk that the PCL tool becomes stuck in the borehole or even broken off due to the attempted forcing. This results in the need to drill a bypass borehole, which may cost the drilling operations millions of dollars in lost time and equipment. 
     SUMMARY 
     The following presents a general summary of several aspects of the disclosure in order to provide a basic understanding of at least some aspects of the disclosure. This summary is not an extensive overview of the disclosure. It is not intended to identify key or critical elements of the disclosure or to delineate the scope of the claims. The following summary merely presents some concepts of the disclosure in a general form as a prelude to the more detailed description that follows. 
     Disclosed is a method for evaluating a formation. The method includes conveying a formation evaluation tool in a borehole on a tubular carrier extending from a surface location at least to the formation evaluation tool. A cable is conveyed to the formation evaluation tool. Communication between the formation evaluation tool and the cable is established after the formation evaluation tool is moved to a selected borehole location and the formation evaluation tool is operated in-situ. 
     Another aspect disclosed is an apparatus for evaluating a formation that includes a tubular carrier, and a formation evaluation tool is coupled to the carrier. The carrier extends from a surface location at least to the formation evaluation tool, and an interface establishes communication between the formation evaluation tool and a cable after the formation evaluation tool is moved to a selected borehole location. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a detailed understanding of the present disclosure, reference should be made to the following detailed description of the several non-limiting embodiments, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals and wherein: 
         FIG. 1  illustrates a non-limiting example of a measurement-after-drilling system according to the disclosure; 
         FIG. 2  illustrates a partial cross-sectional view of a downhole sub according to the disclosure that includes a ballistic sidewall coring tool; 
         FIG. 3  illustrates another partial cross-sectional view of a downhole sub according to the disclosure that includes a fluid sampling tool; 
         FIG. 4  illustrates a non-limiting example of a downhole sub according to the disclosure that includes a rotary sidewall coring tool; and 
         FIG. 5  illustrates one example of a non-limiting method for formation evaluation after drilling according to the disclosure. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       FIG. 1  schematically illustrates a non-limiting example of a formation evaluation (“FE”) system  100  in a measurement-after-drilling (“MAD”) arrangement according to several non-limiting embodiments of the disclosure. The FE system  100  is shown disposed in a well borehole  102  penetrating earth formations  104 . The borehole  102  can be filled with a fluid having a density sufficient to prevent formation fluid influx. In one or more embodiments, the borehole  102  may be a reinforced borehole. For example, the borehole  102  can be reinforced with cement, a casing, or both. Reinforcing the borehole  102  can support the borehole and prevent formation fluid influx into the borehole  102 . 
     A derrick  106  may be used to support a first carrier or (“drill string”)  108 , which may be a coiled tube or drill pipe. The drill string  108  may carry a downhole sub  110  and a drill bit  112  at a distal end of the drill string  108 . In several non-limiting examples, the drill bit  112  may be used for cleaning or reaming a borehole  102 , which has been drilled to total depth (“TD”) by a primary drilling system not shown in this example. A drill motor  116  is shown disposed below the downhole sub  110 . In one or more embodiments, the motor  116  may include a mud motor having a torque less than a primary drilling system mud motor. A higher torque primary motor is not necessary where only cleaning the predrilled borehole is desired. However, those skilled in the art with the benefit of the present disclosure will recognize that a primary drill motor may be used without departing from the scope of the disclosure. 
     The downhole sub  110  includes a formation evaluation (“FE”) tool  114 . As used herein, an FE tool  114  may include a sampling tool, a measurement tool or a combination thereof. Exemplary sampling tools include core sample tools, fluid sample tools or a combination of core and fluid sampling tools. Measurement tools may include pressure measurement tools, gamma ray positioning tools, temperature measurement tools, neutron detectors, spectrometers, chemical analysis tools, nuclear magnetic resonance (NMR) tools, acoustic tools, resistivity tools, dielectric measurement tools, or any combination of these and other tools. 
     The FE system  100  also includes a second carrier or (“slickline”)  126  that may be run into the borehole  102 . The drill string  108  may include a side entry sub  122  having a port  124  for receiving the slickline  126  at a selected position along the drill string  108 . As illustrated the slickline  126  can be spooled and unspooled from a winch or drum  132 . The winch or drum  132  may be disposed on a truck  134 . 
     The exemplary downhole sub  110  disposed on the drill string  108  and the slickline  126  operate as carriers, but any carrier is considered within the scope of the disclosure. The term “carrier” as used herein means any device, device component, combination of devices, media and/or member that may be used to convey, house, support or otherwise facilitate the use of another device, device component, combination of devices, media and/or member. Exemplary non-limiting carriers include drill strings of the coiled tube type, of the jointed pipe type and any combination or portion thereof. Other carrier examples include casing pipes, wirelines, wireline sondes, slicklines, slickline sondes, drop shots, downhole subs, BHAs, drill string inserts, modules, internal housings and substrate portions thereof. 
     The downhole sub  110  may be configured to convey information signals to a first set of surface equipment  136  by the slickline  126 . As will be described in more detail later with reference to  FIG. 2 , a wet connect  120  may be used to establish communication between the slickline  126  and the downhole sub  110  after the downhole sub  110  has been positioned at a selected location in the borehole  102 . The surface equipment  136  can include one part of a telemetry system  138  for communicating control signals and data signals to the downhole sub  110  and may further include a computer  140 . The surface equipment  136  can also include a data recorder  142  for recording measurements acquired by the downhole sub  110  and transmitted to the surface equipment  118 . 
     The system  100  may be configured to convey information signals to a second set of surface equipment  144  that may be substantially similar to the first set of surface equipment  136 . In several non-limiting embodiments the first set of surface equipment  136  and the second set of surface equipment  144  may be a single set of surface equipment. In other non-limiting embodiments the first set of surface equipment  136  and the second set of surface equipment  144  may be combined within a single unit or housing. 
     In operation, the drill string  108  may be run in the borehole  102  after the borehole has been drilled with a primary drilling system. Positioning devices  118 , such as a gamma ray positioning device, accelerometers, magnetometers or the like disposed within or near the downhole sub  110  are used to position the downhole sub  110  at a selected borehole location and orientation. The slickline  126  may be fed into the borehole  102  and then into the drill string  108  via the side entry sub  122 . The slickline  126  may be pumped through the drill string  108  using drilling fluid or “mud” from a mud pit  128  and a circulation system  130  to move the slickline through an inner bore or (“drilling fluid flow line”) of the drill string  108 . The mud exits at the drill bit  112  and returns to the surface through an annular space between the drill string  108  and inner wall of the borehole  102 . The pressurized drilling fluid may further be used to drive the motor  116  and may provide lubrication to various elements of the drill string  108  and/or the slickline  126 . 
     Those skilled in the art will recognize that a pre-drilled borehole may have one or more zones with poor quality dimensions that will hinder a wireline or pipe-conveyed logging (PCL) system. An operator will recognize entry into one of these zones by a weight-on-bit (“WOB”) indicator that exceeds a specified value. Using one or more of the disclosed embodiments, the operator may activate the mud motor  116  using mud pulse telemetry and the second set of surface equipment  144  to begin rotating the bit  112  in the affected zone. Rotating the bit  112  in the affected zone will clean the borehole, thereby making running the sub  110  through the borehole much easier and will greatly reduce the risk of damaging the FE tool  114  carried by the drill string  108 . In one or more embodiments, the drill bit may be a rotary cutting bit, a reaming bit, a roller bit or any other suitable bit for cleaning the borehole ahead of the FE tool  114 . In one or more embodiments, the motor  116  and bit  112  may be operated substantially in a continuous manner while the FE tool  114  is being run in the borehole  102 . 
     Once the FE tool  114  is positioned, the slickline  126  may be run through the drill string and communication may be established via the wet connect device  120  coupled to the downhole sub  110 . The FE tool  114  may then be operated under control by the surface equipment  136  to collect information and/or samples at the selected downhole location. Those skilled in the art with the benefit of the present disclosure will appreciate that any of several FE tools or combinations of FE tools may be included. The FE tool illustrated in the non-limiting example of  FIG. 1  includes one or more ballistic coring devices  146 , which will be described further with reference to  FIG. 2 . 
       FIG. 2  illustrates a partial cross-sectional view of a downhole sub  200  according to the disclosure that includes an FE tool  202  that includes a ballistic sidewall coring tool  204 . The downhole sub  200  may be substantially similar to the downhole sub  110  described above and shown in  FIG. 1 . The downhole sub  200  includes an elongated section  206  having a first end  208  and a second end  210 . The first end  208  includes a coupling  212  suitable for connecting the sub  200  to a drill string  108  as described above and shown in  FIG. 1 . A fluid passage  214  extends through the downhole sub  200  and is routed to bypass the FE tool  202 . The passage  214  may then exit the downhole sub second end  210  at a connection  216  that establishes fluidic communication with a motor  116  and bit  112  substantially as described above and shown in  FIG. 1 . 
     The ballistic coring tool  204  may include several individual coring devices  146 . Each coring device  146  may include an explosive charge section  218  and a releasable bullet  220 . The releasable bullet  220  includes an inner passage  222  that cuts a core sample when the bullet  220  is shot into a sidewall of the borehole. A tether  224  connects the bullet  220  to the tool  204 . The tether  224  may be a stranded fiber or stranded metal tether such as a stainless steel tether that has a tensile strength sufficient to pull the bullet from the formation. After firing, the tether  224  may be used to extract the bullet  220  and core sample from the sidewall by lifting the drill string  108  from the borehole. 
     Each coring device  146  may be electrically connected to a surface controller by electrical conductors  226  that are connected to the slickline  126 . The slickline  126  is connected to the FE tool  202  via a wet connector  120  suitable for establishing an electrical connection after the slickline is pumped down to the FE tool  202 . 
       FIG. 3  illustrates another partial cross-sectional view of a downhole sub  300  according to the disclosure that includes a FE tool  302  incorporating a fluid sampling tool  304 . The fluid sample tool  304  in one or more embodiments may be used to sample fluid from the formation surrounding the borehole. The downhole sub  300  in this non-limiting example includes an elongated section  306  having a first end  308  and a second end  310 . The first end  308  includes a coupling  312  suitable for connecting the sub  300  to a drill string  108  as described above and shown in  FIG. 1 . A fluid passage  314  extends through the downhole sub  300  and is routed to bypass the FE tool  302 . The passage  314  may then exit the downhole sub second end  310  at a connection  316  that establishes fluidic communication with a motor  116  and bit  112  substantially as described above and shown in  FIG. 1 . 
     In one or more embodiments, the fluid sampling tool  304  may include an elastomeric pad  318  mounted on an extendable probe  320 . The extendable probe  320  may be in fluid communication with a fluid mover  322  such as a piston within the extendable probe  320 , a fluid pump or a combination thereof via a flowline  324 . In some embodiments, one or more back-up feet  326  or a backup shoe may be provided to extend to a borehole wall portion substantially opposite the area engaged by the pad  318 . Construction and operational details of a suitable non-limiting fluid sample tool  304  for extracting fluids are more described by U.S. Pat. No. 5,303,775, the specification of which is incorporated herein by reference. The exemplary sub  300  may include a recess  336  into which the probe  320  and pad  318  may be retracted during transport in the borehole. O-ring seals  338  may be provided to provide a fluid barrier between internal portions of the tool  302  and the borehole. A similar recess  336  and O-ring seals  338  may be provided for the back-up feet  326  when used. 
     A controller  328  may be included to control operation of the extendable probe  320 , the back-up feet  326  and the fluid mover  322 . One or more positioning devices  118  may be disposed in a suitable location to provide precise positioning and orientation of the sub  300  and FE tool  302  for MAD operations. A fluid analyzer  330  may be included to analyze fluid samples entering the tool  302 . In one or more embodiments, the fluid analyzer may include a spectrometer, a resistivity tool, a dielectric tool, a neutron detector, a gas chromatograph or a combination thereof. 
     In one or more non-limiting embodiments, a sample container  332  may be disposed in the FE tool  302  to collect fluid samples for further testing at a surface laboratory. Although two sample containers are shown, a single container or more than two containers may be included without departing from the scope of the disclosure. A compensator  334  may be incorporated with each sample container  332 . A compensator  334  may include any number of devices for maintaining the sample at a pressure and temperature sufficient to avoid precipitates while the fluid sample is removed from the borehole. Several examples of suitable sampling chamber configurations capable of maintaining sample pressure are described in U.S. Pat. Nos. 5,303,775 and 5,377,755 for “Method and Apparatus for Acquiring and Processing Subsurface Samples of Connate Fluid,” which patents are assigned to the assignee of the present application and incorporated herein in their entireties by reference. 
     In one or more non-limiting operational embodiments, the FE tool  302  is conveyed on the downhole sub  300  after a primary drilling system has drilled a borehole through a zone of interest. The drilling motor  116  may be operated to rotate the drill bit  112  when the drill string encounters an obstruction of otherwise poor quality borehole zone. 
     The positioning devices  118  are operated to position and orient the FE tool  302  at a selected position in the borehole. A slickline  126  is conveyed in the borehole to a side-entry sub  122  at which point the slickline enters the drill string  108  and is pumped down the drill string using surface equipment as discussed above and shown in  FIG. 1 . 
     The slickline  126  includes a wet connect connector  120  that engages a corresponding wet connect connector mounted on the downhole sub to establish communication with the FE tool  302  after the FE tool is positioned. The FE tool  302  may then be operated under control by the surface equipment  136  to collect information and/or samples at the selected downhole location. The slickline  126  provides high bandwidth data communication between the surface equipment and the tool, and the high bandwidth enables more information and commands to be transmitted. 
       FIG. 4  illustrates a non-limiting example of a downhole sub  400  according to the disclosure that includes FE tool  402  incorporating a rotary sidewall coring tool  404 . The rotary sidewall coring tool  404  in one or more embodiments may be used to collect a core sample from the formation surrounding the borehole. The downhole sub  400  in this non-limiting example includes an elongated section  406  having a first end  408  and a second end  410 . The first end  408  includes a coupling  412  suitable for connecting the sub  400  to a drill string  108  as described above and shown in  FIG. 1 . A fluid passage  414  extends through the downhole sub  400  and is routed to bypass the FE tool  402 . The passage  414  may then exit the downhole sub second end  410  at a connection  416  that establishes fluidic communication with a motor  116  and bit  112  substantially as described above and shown in  FIG. 1 . 
     In one or more embodiments, the rotary sidewall coring tool  304  may include a cutting element  418  mounted on an extendable bit body  420 . Suitable coring tools for the purposes of this disclosure may be substantially as described in U.S. Pat. No. 5,617,927 for “Sidewall Rotary Coring Tool” and in published U.S. patent application Ser. No. 11/215,271 having the publication number US 2007/0045005 A2, which patent and published application are assigned to the assignee of the present application and are incorporated in their entireties herein by reference. 
     The exemplary coring tool  404  may include back-up feet  422  or a shoe positioned substantially opposite the cutting element  418 . A core sample container  428  may be included to contain a core sample for retrieval to the surface. A sample compensator may also be included as described above and shown in  FIG. 3  to maintain the core sample and any fluid collected along with the core sample during transport to the surface. In one or more embodiments, a controller  430  may be included with the FE tool  402  to control operation of the coring tool  404 . The controller  430  may be electrically coupled to the surface equipment  136  via the slickline  126  and wet connector  120 . 
     The exemplary sub  400  includes a recess  424  into which the cutting element  418  may be retracted during transport in the borehole. O-ring seals  426  may be provided to provide a fluid barrier between internal portions of the tool  402  and the borehole. A similar recess  424  and O-ring seals  426  may be provided for the back-up feet  422  when used. 
     In one or more non-limiting operational embodiments, the FE tool  402  is conveyed on the downhole sub  400  after a primary drilling system has drilled a borehole through a zone of interest. The drilling motor  116  may be operated to rotate the drill bit  112  when the drill string encounters an obstruction of otherwise poor quality borehole zone. 
     The positioning devices  118  are operated to position and orient the FE tool  402  at a selected position in the borehole. A slickline  126  is conveyed in the borehole to a side-entry sub  122  at which point the slickline enters the drill string  108  and is pumped down the drill string using surface equipment as discussed above and shown in  FIG. 1 . 
     The slickline  126  includes a wet connect connector  120  that engages a corresponding wet connect connector mounted on the downhole sub to establish communication with the FE tool  402  after the FE tool is positioned. The FE tool  402  may then be operated under control by the surface equipment  136  to collect information and/or core samples at the selected downhole location. 
       FIG. 5  illustrates one example of a non-limiting method  500  for formation evaluation after drilling according to the disclosure. The method  500  includes drilling a borehole to TD  502  using a primary drilling system. A downhole tool may then be positioned at a selected depth  504  by conveying the downhole tool on a drill pipe having a drill bit on an end thereof for cleaning the borehole ahead of the tool. In one or more embodiments, the method may further include conveying or running a cable to the downhole tool and making a communication connection with the tool using a wet connector  506 . The downhole tool may then be operated  508  at the selected depth. In one or more embodiments, the tool may be operated and controlled using surface equipment in communication with the tool via the cable. An advantage of running the cable after the tool is that the drill pipe may be used to support the weight of the tool and the cable may better withstand the stress in very deep well applications. Another advantage is that the cable may be pumped through the drill pipe using a surface pumping system and the cable may be run in a well deviated from vertical. 
     The present disclosure is to be taken as illustrative rather than as limiting the scope or nature of the claims below. Numerous modifications and variations will become apparent to those skilled in the art after studying the disclosure, including use of equivalent functional and/or structural substitutes for elements described herein, use of equivalent functional couplings for couplings described herein, and/or use of equivalent functional actions for actions described herein. Such insubstantial variations are to be considered within the scope of the claims below. 
     Given the above disclosure of general concepts and specific embodiments, the scope of protection is defined by the claims appended hereto. The issued claims are not to be taken as limiting Applicant&#39;s right to claim disclosed, but not yet literally claimed subject matter by way of one or more further applications including those filed pursuant to the laws of the United States and/or international treaty. 
     Certain embodiments and features have been described using a set of numerical upper limits and a set of numerical lower limits. It should be appreciated that ranges from any lower limit to any upper limit are contemplated unless otherwise indicated. Certain lower limits, upper limits and ranges appear in one or more claims below. All numerical values are “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.