Abstract:
The present invention generally relates to an apparatus and a method for conveying and operating tools into a wellbore. In one aspect, a method of performing a downhole operation in a wellbore is provided. The method includes pushing a continuous rod into the wellbore, wherein the continuous rod includes a member disposed therein. The method further includes positioning the continuous rod proximate at a predetermined location in the wellbore and performing the downhole operation. In yet another aspect, a system for performing a downhole operation in a wellbore is provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation-in-part of co-pending U.S. patent application Ser. No. 10/127,021, filed Apr. 19, 2002, which claims benefit of U.S. provisional patent application Ser. No. 60/285,891, filed Apr. 23, 2001. This application is also a continuation-in-part of co-pending U.S. patent application Ser. No. 10/867,389, filed Jun. 14, 2004. This application is also a continuation-in-part of co-pending U.S. patent application Ser. No. 10/848,337, filed May 18, 2004, which claims benefit of U.S. Pat. No. 6,736,210, filed Feb. 6, 2001. This application is also a continuation-in-part of co-pending U.S. patent application Ser. No. 10/999,818, filed Nov. 30, 2004, which claims benefit of U.S. Pat. No. 6,825,459, filed Sep. 10, 2001 which was a continuation-in-part of U.S. patent application Ser. No. 09/225,029, filed Jan. 4, 1999 (now abandoned). This application is also a continuation-in-part of co-pending U.S. patent application Ser. No. 10/068,555, filed Feb. 6, 2002. Each of the aforementioned related patent applications is herein incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention generally relates to the operation of instrumentation within a wellbore. More particularly, the invention relates to an apparatus and a method for conveying and operating tools into a wellbore.  
         [0004]     2. Description of the Related Art  
         [0005]     In the drilling of oil and gas wells, a wellbore is formed using a drill bit that is urged downwardly at a lower end of a drill string. After drilling a predetermined depth, the drill string and the drill bit are removed, and the wellbore is lined with a string of steel pipe called casing. The casing provides support to the wellbore and facilitates the isolation of certain areas of the wellbore adjacent hydrocarbon bearing formations. An annular area is thus defined between the outside of the casing and the earth formation. This annular area is typically filled with cement to permanently set the casing in the wellbore and to facilitate the isolation of production zones and fluids at different depths within the wellbore. Numerous operations occur in the well before or after the casing is secured in the wellbore. Many operations require the insertion of some type of instrumentation or hardware within the wellbore. For instance, logging tools are employed in the wellbore to determine various formation or structural parameters including hydrocarbon saturation and cement bond integrity.  
         [0006]     Early oil and gas wells were typically drilled in a vertical or near vertical direction with respect to the surface of the earth. As drilling technology improved and as economic and environmental demands required, an increasing number of wells were drilled at angles which deviated significantly from vertical. In the last several years, drilling horizontally within producing zones became popular as a means of increasing production by increasing the effective wellbore wall surface exposed to the producing formation. It is not uncommon to drill sections of wellbores horizontally (i.e. parallel to the surface of the earth) or even “up-hill” where sections of the wellbore were actually drilled toward the surface of the earth.  
         [0007]     The advent of severely deviated wellbores introduced several problems in the performance of some wellbore operations. Conventional logging was especially impacted. Conventional logging utilizes the force of gravity to convey logging instrumentation into a wellbore. Gravity is not a suitable conveyance force in highly deviated, horizontal or up-hill sections of wellbores. Numerous methods have been used, with only limited success, to convey conventional instrumentation or “tools” in highly deviated conditions. These methods include the use of conveyance members such as electric wireline, slickline, coiled tubing, or jointed pipe.  
         [0008]     Electric wireline or “wireline” is generally a multi-strand wire or cable for use in oil or gas wells. Wireline typically comprises at least a single conductor cable surrounded by a plurality of braided non-conductive cables. The non-conductive cables provide structural support for the single conductor cable during transport of the wireline into the wellbore. In a logging operation, a logging tool is attached to the wireline and then the tool string is either lowered into the wellbore utilizing the force of gravity or pulled into the wellbore by a tractor device. As discussed above, gravity is not a suitable conveyance force in highly deviated, horizontal, or up-hill sections of wellbores, and tractor devices are expensive and complex.  
         [0009]     A slickline is generally a single-strand non-conductive wire with an outer diameter between 5/16″ to ⅜″. Due to the slickline&#39;s small diameter (particularly in relation to typical wellbore diameters) and hence minimal columnar buckling resistance, slickline cannot be pushed or urged into the wellbore, but rather slickline must rely on utilizing the force of gravity. For example, in a logging operation, a logging tool is attached to the slickline and then the tool string is lowered into the wellbore utilizing the force of gravity. As discussed above, gravity is not a suitable conveyance force in highly deviated, horizontal, or up-hill sections of wellbores. Both slickline and wireline are “impossible” to push for any appreciable distance in a wellbore. The old adage “like pushing a rope” indicating extremely difficult is applicable to attempts to deploy wireline or slickline by means of axial force applied from the surface (of the Earth). The structural component of wireline is typically braided cable. As such, wireline performs reasonably well under axial tension, but particularly poorly under axial compression. The buckling strength of wireline having a given apparent diameter is greatly diminished because the strands of cable comprising the wireline are capable of relative axial movement. Even slickline, which is typically single strand construction, has a fairly low buckling strength because of its small diameter (and therefore large length to diameter ratio when deployed).  
         [0010]     Coiled tubing can be “pushed” into a wellbore more readily than wireline or slickline but still has limitations. Coiled tubing is a long continuous length of spooled or “reeled” thin walled pipe. Coiled tubing units utilize hydraulic injector heads that push the coiled tubing from the surface, allowing it to reach deeper than slickline, but ultimately the coiled tubing stops as well. Coiled tubing is susceptible to a condition known as lockup. As the coiled tubing goes through the injector head, it passes through a straightener; but the tubing retains some residual bending strain corresponding to the radius of the spool. That strain gives the tubing a helical form when deployed in a wellbore. Therefore it winds axially along the wall of the wellbore like a long, stretched spring. Ultimately, when a long enough length of coiled tubing is deployed in the well bore, frictional forces from the wellbore wall rubbing on the coiled tubing cause the tubing to bind and lock up, thereby stopping its progression. Such lock up limits the use of coiled tubing as a conveyance member for logging tools in highly deviated, horizontal, or up-hill sections of wellbores.  
         [0011]     Another limitation of coiled tubing is the limited capability of pushing coiled tubing into the wellbore due to known structural characteristics of coiled tubing. Coiled tubing comes in a range of diameters and wall thicknesses. For instance, coiled tubing could have a 1″ diameter with a wall thickness of 0.080″ to approximately a 3.5″ diameter with a wall thickness of 0.203″. The ability of a pipe to withstand buckling under axial end loading is proportional to the pipe diameter and the pipe wall thickness as indicted by generally accepted equations for calculating column buckling. In the Eulerian equation below for buckling of cylindrical cross sections under axial end loading, the critical buckling load P cr  is a function of material properties (properties of steel are most often applicable in the case of coiled tubing) and the outer and inner diameters of the cylindrical column (note: outer diameter minus inner diameter divided by two equals wall thickness). 
 
 P   cr =4π 3   E ( D   4   −d   4 )/64 L   2  
        E=Youngs&#39;s Modulus for steel (3×10 7 )     D=outer diameter     d=inner diameter     L=length        
 
         [0016]     Further, the above equation illustrates that as the length of deployed tubing increases the load at which that tubing will buckle decreases. In a typical extended reach well (thousands of feet deep) readily coiled tubing buckles due to the friction loading between lower portions of the tubing and the walls of the wellbore. Once buckling occurs such frictional loading increases and ultimately exceeds the capacity of the surface equipment and/or the coiled tubing to sustain further loading. At that point, the coiled tubing has gone as far into the wellbore as it can go. Thus, the structural characteristics of coiled tubing limits the capability of using coiled tubing as a conveyance member for logging tools in highly deviated, horizontal, or up-hill sections of wellbores.  
         [0017]     Further exacerbating the aforementioned buckling issue is the fact that coiled tubing is supplied from the manufacturer on a reel. For practical transportation and handling matters such reels have size (outer diameter) limits that are not to be exceeded. As such, coiled tubing is plastically deformed when reeled at the manufacturing mill because it must be made to fit on a given reel regardless of its cross-sectional diameter. The tubing is not only deformed axially by such installation on the reel, it is also deformed cross-sectionally such that it assumes a permanent ovality. Such “factory” ovality specifications are published by the various manufacturers of coiled tubing. The capability of employing coiled tubing in highly deviated, horizontal, or up-hill sections is therefore further limited due to the ovality of the coiled tubing because the ovality decreases the buckling resistance of the tubing. The ovality in conjunction with the residual axial strain (from being reeled) also causes the tubing to assume an inherent helical profile when deployed in a wellbore and therefore at even relatively small axial compression loads the tubing winds helically against the wall of the well bore thereby increasing its frictional engagement of that wall. Ovality also decreases the ability of the tube to resist collapse under external differential pressure. Thus, the ovality limits of coiled tubing also limits the capability of using coiled tubing as a conveyance member for logging tools in highly deviated, horizontal, or up-hill sections of wellbores.  
         [0018]     Jointed pipe has been used for the deployment of certain downhole devices even where “pushing” is required. In a given diameter range jointed pipe has greater buckling resistance than any of wireline, slickline, or coiled tubing. Each threaded connection (typically every thirty feet) in a string of jointed pipe acts as a column stiffener and upset threaded connections also tend to stand the bulk of the pipe away from the wall of the wellbore thereby reducing cumulative frictional engagement. Jointed pipe is deficient in that it requires a rig (including some form of derrick or crane) for deployment and deployment is very time consuming. Each threaded connection must be made and unmade when correspondingly deploying or retrieving jointed pipe. The additional time consumption and the logistics of moving a rig onto a work location make the use of jointed pipe very expensive as compared with reeled deployment options such as wireline, slickline, and coiled tubing.  
         [0019]     A need therefore exists for a reliable and operationally efficient apparatus and method to convey and operate a wellbore tool, such as a logging tool, in a wellbore which is deviated from the vertical.  
       SUMMARY OF THE INVENTION  
       [0020]     One embodiment generally relates to an apparatus and a method for conveying and operating tools into a wellbore. In one aspect, a method of performing a downhole operation in a wellbore is provided. The method includes pushing a continuous rod into the wellbore, wherein the continuous rod includes a communication member disposed therein. The method further includes positioning the continuous rod proximate a predetermined location in the wellbore and performing the downhole operation.  
         [0021]     In another aspect, a method of performing a downhole operation in a wellbore is provided. The method includes pushing a continuous rod into the wellbore, wherein the continuous rod includes a small bore disposed therein. Optionally the small bore may be coated with a material. The method further includes positioning the continuous rod proximate a predetermined location in the wellbore and transmitting a signal through the small bore.  
         [0022]     In further aspect, a method of performing a downhole operation in a deviated wellbore is provided. The method includes pushing a continuous rod into the deviated wellbore. The method further includes positioning the continuous rod proximate a predetermined location in the deviated wellbore and transmitting a signal.  
         [0023]     In yet another aspect, a system for performing a downhole operation in a wellbore is provided. The system includes a continuous rod having a data communication member operatively attached thereto. The system further includes a delivery apparatus for pushing the continuous rod into the wellbore, wherein the delivery apparatus includes a depth encoder for tracking the amount of continuous rod pushed into the wellbore. Additionally, the system includes a member having circuitry for receiving and analyzing data from the data communication member and the depth encoder. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]     So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.  
         [0025]      FIG. 1  is a sectional view illustrating a continuous sucker rod (“COROD”®)) string positioned in a wellbore, wherein the COROD string includes a signal transmission line disposed therein.  
         [0026]      FIG. 1A  is one embodiment that illustrates steps of operating a tool in a wellbore.  
         [0027]      FIG. 2  is a sectional view illustrating a COROD string positioned in the wellbore, wherein the COROD string includes a member coaxially disposed therein.  
         [0028]      FIG. 3  is a sectional view illustrating a COROD string positioned in the wellbore, wherein the COROD string includes a small bore coaxially disposed therein.  
         [0029]      FIG. 4  is a cross-section view taken along lines  4 - 4  in  FIG. 3 .  
         [0030]      FIG. 5  is a sectional view illustrating a solid COROD string positioned in the wellbore.  
         [0031]      FIG. 6  is a sectional view illustrating a COROD string positioned in the wellbore, wherein the COROD string includes a slot for housing a cable.  
         [0032]      FIG. 7  is a cross-section view taken along lines  7 - 7  in  FIG. 6 .  
         [0033]      FIG. 8  is a sectional view illustrating a COROD string with a pump system.  
         [0034]      FIG. 9  is a block diagram of a logging system for use with a COROD string. 
     
    
     DETAILED DESCRIPTION  
       [0035]     Typically, a continuous sucker rod or COROD string is made from a round cross section solid or near solid rod having for example at least a ⅝″ outer diameter. While the outer diameter dimensions may vary, the relatively small diameter to thickness ratios of COROD is distinctive. For solid cross section COROD the diameter to thickness ratio can be stated as equaling 2 (taking thickness from the cross section centerline). For COROD with a small inner diameter such as ⅛″ and an outer diameter of 1⅛″ the diameter to thickness ratio could be stated as equaling 2.25. If the inner diameter of such a 1⅛″ COROD were larger than ⅛″ the diameter to thickness ratio would increase correspondingly. The diameter to thickness ratios for COROD is however significantly less than those for coiled tubing for which the ratios are typically 15 and higher. Unlike a jointed sucker rod which is made in specific lengths and threaded at each end for sequential connection of those lengths, COROD is made in one continuous length and placed on a reel. Because COROD has fairly low diameter to thickness ratios (often equaling 2 as previously discussed), such reeling does not impart any significant ovality to the COROD. Further the COROD diameter in relation to the diameter or apparent diameter of the reel is such that residual bending strain in the COROD is minimized or eliminated. As such the COROD retains its buckling resistance characteristics when deployed into a wellbore. Unlike wireline or slickline, COROD can be “pushed” into a wellbore and unlike coiled tubing it can be pushed further because it doesn&#39;t tend to helix within the wellbore. Also, because COROD has material across a substantial portion of its cross section it retains relatively high tensile and compressive strength under axial loading as well as internal or external differential pressure. COROD is superior to jointed pipe because it can be deployed using a more cost effective and logistically versatile system and in a more time efficient manner.  
         [0036]     The COROD string works equally well in vertical and highly deviated wells. The COROD can be used for multiple runs into a well or wells with no fatigue because unlike coiled tubing it is not plastically deformed when cycled on and off the reel. The COROD string can be run through tubing thereby eliminating the additional cost and time required to deploy a jointed pipe, or tractor conveyed systems. It is also noteworthy that the COROD string for conveying equipment is not limited to oil and gas well applications. It is equally applicable to use in a pipeline where pipeline inspection services are run. To better understand the novelty of the apparatus of the present invention and the methods of use thereof, reference is hereafter made to the accompanying drawings.  
         [0037]      FIG. 1  is a sectional view illustrating a COROD string  100  positioned in a wellbore  10 . As shown, the wellbore  10  is lined with a string of casing  15 . The casing  15  provides support to the wellbore  10  and facilitates the isolation of certain areas of the wellbore adjacent hydrocarbon bearing formations. For purposes of discussion, the wellbore  10  is illustrated as a deviated wellbore. It should be understood, however, that the COROD string  100  may be employed in a vertical wellbore without departing from principles of the present invention.  
         [0038]     Generally, the COROD string  100  is positioned at the wellsite on a rotatable storage reel  35 . Next, an end of the COROD string  100  is inserted into a delivery apparatus  30  that is affixed to a wellhead  20 . The delivery apparatus  30  provides the force required to insert the COROD string  100  into the wellbore  10  and to withdraw the COROD string  100  out of the wellbore  10 . Preferably, the delivery apparatus  30  includes a depth encoder  25  to record the amount of COROD string  100  within the wellbore  10  at any given time thereby determining the position of a tool  110  within the wellbore  10 . For example, when the COROD string  100  is used in a logging operation, the downhole tool  110  records data of interest in a memory module within the downhole tool  110 . Data is subsequently retrieved from the memory module when the tool  110  is withdrawn from the wellbore  10 . Optionally such data can be transmitted in real time using embodiments of COROD comprising signal transmission paths. Data measured and recorded by the downhole tool  110  is then correlated with the depth encoder reading thereby defining the position of the tool  110  in the wellbore  10 . This information is then used to form a “log” of measured data as a function of depth within the wellbore  10  at which the data is recorded.  
         [0039]     The delivery apparatus  30  may include circuitry for receiving and analyzing data. Alternatively, a surface acquisition member (not shown) or a data acquisition member (not shown) may be employed to provide the circuitry for receiving and analyzing data.  
         [0040]     The foregoing apparatus and its methods of use are equally useful with a variety of conveyance members including solid, continuous rod, coiled tubing, jointed pipe and slickline.  
         [0041]     Additionally, the memory module may include a processor. As shown in  FIG. 1A , previously generated log data may be entered into the memory and the processor may generate a signal or actuate a tool carried by a conveyance member in response to arriving at a predetermined location in the wellbore. Such a predetermined location can be identified by logging the well while running and comparing that real time data to the previously generated data to verify arrival at the predetermined location. It should be noted that the conveyance member could be any conveyance member known in the art, such as a continuous reelable rod (COROD), jointed pipe, coiled tubing or slickline. The general use of real time data for placement of downhole tools is shown in U.S. Publication No. U.S. 2002/0104653, which is incorporated herein by reference.  
         [0042]     Referring back to  FIG. 1 , the COROD string  100  includes a fiber line  105 . Preferably, the fiber line  105  is coaxially disposed within the COROD string  100 . In one embodiment, the fiber line  105  may be used to transmit signals to a downhole apparatus to effect the operation thereof. For instance, the tool  110  may have a valve arrangement. A signal from the surface of the wellbore  10  may be transmitted through the fiber line  105  in the COROD string  100  and processed by a controller to actuate the valve arrangement of the tool  110 . It is contemplated that other forms of types of tools may be employed without departing from the aspects of the present invention.  
         [0043]     In another embodiment, the tool  110  may be a sensor that is designed to provide real time data regarding wellbore parameters such as pressure, temperature, strain, and/or other monitored parameters. Generally, perturbations in these parameters induce a phase shift in the optical signal, which is received from the tool  110  by a receiver (not shown). When the receiver receives the signal, the phase shift is detected. The phase shift is processed using interferometric techniques such as Mach-Zehnder, Michelson, Fabry-Perot, and Sagnac.  
         [0044]     In a further embodiment, the tool  110  may include multiple optical sensors arranged in a network or array configuration with individual sensors multiplexed using time division multiplexing or frequency division multiplexing. The network of sensors may provide an increased spatial resolution of temperature, pressure, strain, or flow data in the wellbore  10 . One form of sensor networks is known as distributed sensing. Distributed sensor schemes typically include Bragg grating sensors and optical time domain reflectometry (“OTDR”). For example, Bragg grating sensors may be formed in one or more positions along the length of the fiber line  105 . These sensors provide real time data at each of these positions, which can be processed to give a clearer picture of the conditions along the length of the wellbore  10 . In another example, Raman OTDR may be used to collect temperature data to provide a temperature gradient inside the wellbore  10 . It is contemplated that other schemes of optical sensors  100  may be used without departing from the aspects of the present invention.  
         [0045]      FIG. 2  is a sectional view illustrating a COROD string  200  positioned in the wellbore  10 , wherein the COROD string  200  includes a member  205  coaxially disposed therein. It should also be noted that member  205  has a small diameter relative to the diameter of the COROD string  200  and therefore the strength of the COROD string  200  is not substantially affected. For convenience, components in  FIG. 2  that are similar to the components in  FIG. 1  will be labeled with the same number indicator.  
         [0046]     In one embodiment, the member  205  is a capillary tube coaxially disposed within the COROD string  200 . The capillary tube may be employed for injecting chemicals to an area of interest in the wellbore  10 . In this embodiment, the COROD string  200  is positioned proximate an area of interest to be chemically treated. Next, a chemical injector (not shown) at the surface of the wellbore  10  is attached to the capillary tube in the COROD string  200 . Thereafter, the chemical injector urges a chemical through the capillary tube to the area of interest. If required, the COROD string  200  may be moved to another area of interest and the injection process may then be repeated as many times as necessary.  
         [0047]     In another embodiment, the capillary tube (member  205 ) may also be used for pressure measurement. In this embodiment, the COROD string  200  is positioned at a predetermined location in the wellbore  10 . Next, a pressure gage (not shown) is connected to the capillary tube to measure the pressure at the predetermined location. The COROD string  200  could then be moved to another location and then another pressure measurement could be taken. Thereafter, the pressure measurement data could be correlated with the depth encoder reading thereby defining the pressure at various locations in the wellbore  10 . This information is then used to form a “log” of measured data as a function of depth within the wellbore  10  at which the data was recorded.  
         [0048]     In a further embodiment, the capillary tube (member  205 ) may be used to actuate a tool  210  at the lower end of the COROD string  200 . In this embodiment, the COROD string  200  is urged into the wellbore  10  to position the tool  210  proximate a predetermined point. Next, a signal, such as a pressure signal or a pulse signal, may be transmitted from the surface of the wellbore  10  through the capillary tube to the tool  210 . Thereafter, the signal may be processed by a downhole controller (not shown) or may otherwise physically act upon a portion of the tool to actuate tool  210 .  
         [0049]     In another embodiment, the member  205  is a conductor cable capable of transmitting electrical power for use in performing various down hole operations, such as welding or melting paraffin. In this embodiment, the COROD string  200  is positioned in the wellbore  10  proximate an area of interest. Next, the conductor cable in the COROD string  200  is attached to an electrical generation apparatus (not shown) at the surface of the wellbore  10 . Thereafter, an electrical power generated by the apparatus is transmitted through the conductor cable in the COROD string  200  to the area of interest to perform a downhole operation. The conductor cable may be surrounded by an insulating layer within the COROD or the COROD may be insulated about its exterior.  
         [0050]      FIG. 3  is a sectional view illustrating a COROD string  300  positioned in the wellbore  10 , wherein the COROD string  300  includes a small bore  305 . For convenience, components in  FIG. 3  that are similar to the components in  FIG. 1  will be labeled with the same number indicator. As shown in  FIG. 4 , the bore  305  may be coaxially disposed within the COROD string  300  and the bore has a small diameter relative to the diameter of the COROD string  300  and therefore the strength of the COROD string  300  is not substantially affected. In one embodiment, the bore  305  has a ¼″ diameter.  
         [0051]     In another embodiment, the small bore  305  is coated with a low dielectric material, such as plastic (i.e. polymer), that is used to transmit microwave signals or other electromagnetic waveform signals up and down the COROD string  300  and to provide real time data. In this embodiment, the COROD string  300  is positioned in the wellbore  10 . Next, a microwave signal is generated and transmitted through the bore  305  of the COROD string  300 . Thereafter, a microwave receiver (not shown) positioned proximate the wellbore  10  receives the microwave signal and records data. After the data is collected, the data may be correlated with the depth encoder reading thereby defining the data points at various locations in the wellbore  10 . This information is then used to form a “log” of measured data as a function of depth within the wellbore  10  at which the data was recorded.  
         [0052]     In another embodiment, the small bore  305  is coated with a reflective material that is used to transmit light signals up and down the COROD string  300  and to provide real time data. In this embodiment, the COROD string  300  is positioned in the wellbore  10 . Next, a light signal is generated and transmitted through the bore  305  of the COROD string  300 . Thereafter, a receiver (not shown) positioned proximate the wellbore  10  receives the light signal and records data. After the data is collected, the data may be correlated with the depth encoder reading thereby defining the data points at various locations in the wellbore  10 . This information is then used to form a “log” of measured data as a function of depth within the wellbore  10  at which the data was recorded.  
         [0053]      FIG. 5  is a sectional view illustrating a solid COROD string  400  positioned in the wellbore  10 . For convenience, components in  FIG. 5  that are similar to the components in  FIG. 1  will be labeled with the same number indicator. In one embodiment, the COROD string  400  includes a plurality of centralizers  405 . Each centralizer  405  is a mechanical device that is used to position the COROD string  400  concentrically in the wellbore  10 . More specifically, the centralizer  405  is used to provide a constant annular space around the COROD string  400 , rather than having the COROD string  400  lying eccentrically against the wellbore  10 . For straight holes, bow spring centralizers are sufficient and commonly used. For deviated wellbores, where gravitational force pulls casing to the low side of the hole, more robust solid or solid-bladed centralizers are typically used. Optionally the centralizers may be constructed of an acoustic insulating material. In other embodiments the centralizers or stabilizers may have other insulating properties as needed (e.g. electrically insulating).  
         [0054]     In this embodiment, the COROD string  400  is lowered into the wellbore  10  to a predetermined depth. Thereafter, an acoustic signal is generated at the surface of the wellbore  10  and transmitted through the COROD string  400 . The acoustic signal is used to perform a downhole operation, such as actuation of a downhole tool  410 . As shown in  FIG. 5 , the centralizers  405  concentrically position the COROD string  400  in the wellbore  10 . This arrangement substantially insulates the COROD string  400  from the wellbore  10  and minimizes the dampening effects due to wellbore contact and thereby allowing the acoustic signal to pass through the COROD string  400  to perform the downhole operation. It is understood that such acoustic transmission can also be generated downhole and transmitted to the surface or to another location in the wellbore.  
         [0055]     In another embodiment, the outer diameter of the COROD string  400  may be coated with an acoustic insulator to facilitate signal transfer by reducing the dampening effects due to contact with the sides of the wellbore  10 . In this embodiment, the COROD string  400  is lowered into the wellbore  10  to a predetermined depth. Thereafter, an acoustic signal is generated at the surface of the wellbore  10  and transmitted through the COROD string  400  to perform a downhole operation, such as actuation of the downhole tool  410 . To further minimize the dampening effects of the acoustic signal due to contact between the COROD string  400  and the sides of the wellbore  10 , the acoustic insulator coating may be used in conjunction with the centralizers  405 . It is understood that such acoustic transmission can also be generated downhole and transmitted to the surface or to another location in the wellbore. The same is true of any signal transmission mechanism that may be used in conjunction with or that comprises COROD.  
         [0056]     In another embodiment, the COROD string  400  could be used as a data conductor by coating the outer diameter with an insulator. In this embodiment, the COROD string  400  could be lowered to a predetermined location in the wellbore  10 . Thereafter, a data signal could be generated at the surface of the wellbore and transmitted downhole via the insulated COROD string  400  to perform a downhole operation, such as actuation of a downhole tool or measurement of a downhole parameter. Alternatively, a data signal could be generated downhole and transmitted to the surface via the insulated COROD string  400 . In either case, the data could be collected and correlated with the depth encoder reading thereby defining the data points at various locations in the wellbore  10 . This information is then used to form a “log” of measured data as a function of depth within the wellbore  10  at which the data was recorded. Such a data signal or power signal may be electromagnetic, acoustic or any other type that would benefit from an insulating layer as described.  
         [0057]     In a further embodiment, the COROD string  400  includes a cross-section (not shown) with a first transmission path and a second transmission path. The paths may be coated with a material that allows the COROD string  400  to transmit signals, such as a microwave signal or a light signal. Alternatively, the paths may be used for performing a downhole operation, such as chemical injection, pressure measurement, or tool actuation. One or both of the paths may be located eccentrically within the cross-section of the COROD. Optionally the COROD may comprise more than two paths and further it may comprise a variety such as one or more electrically conductive paths in conjunction with one or more fluid, optical, or acoustic paths.  
         [0058]      FIG. 6  is a sectional view illustrating a COROD string  500  positioned in the wellbore  10 , wherein the COROD string  500  includes a slot  505  for housing a cable  510  or other suitable transmission members. For convenience, components in  FIG. 6  that are similar to the components in  FIG. 1  will be labeled with the same number indicator.  
         [0059]     As shown in  FIG. 7 , the COROD string  500  includes the slot  505  formed on an outer surface thereof. The slot  505  is substantially continuous the entire length of the COROD string  500 . The slot  505  is constructed and arranged to house the cable  510  within the COROD string  500 . The cable  510  may be secured in the slot  505  by any connection means known in the art, such as a plurality of connection members, glue, or a sheath surrounding the COROD. Typically, the cable  510  is placed in the slot  505  prior to placing the COROD string  500  into the wellbore  10 . The cable  510  may be used to perform a downhole operation in a similar manner as discussed herein. Alternatively, a capillary tube could be positioned in the slot  505 , wherein the capillary tube can be used to perform a downhole operation in a similar manner as discussed herein.  
         [0060]     In another embodiment, the COROD string of the present invention may also be used in other types of wellbore operations. For example, as shown in  FIG. 8 , a COROD string  550  may be used to deploy a rod driven pump system  555  in a wellbore  565 , locate the pump system  555 , activate an anchor mechanism  560  of the pump system  555 , and then drive the pump system  555  by transmitting rotational energy from the surface as indicated by arrow  570 . Alternatively, the pump system  555  may be driven by transmitting electrical, optical, hydraulic or reciprocating energy from the surface or combinations thereof. In the case of physical rotation or reciprocation, a solid rod may be used. Alternatively, a tubular rod could have a conductor therein.  
         [0061]     The COROD could be further used to then monitor one or all of pumping parameters, formation parameters, or production parameters and optionally to transmit data back to the surface to facilitate control of the pumping operation. Such a pump system may include an electric submersible, progressing cavity, or reciprocating rod type pump or other suitable pump. Such a system may further include packers and other downhole flow control devices. Further, the COROD string could be constructed and arranged for use in fishing services due to the high push/pull capability of the COROD string. In another example, the COROD string may be constructed and arranged for use in completion operations, such as placing a flat pack in the wellbore, wherein the flat pack includes hydraulic and electrical umbilicals. In yet another example, the COROD string may be used to locate a casing exit window by deploying a logging device and using original survey data either transmitted via the COROD or contained within a memory module attached thereto. Additionally, the COROD string may be used to position or orient tools in the wellbore and the COROD string may be used with a multifinger imaging tool (MIT) to evaluate dynamic flow conditions and borehole profile on a horizontal well. In another example, the COROD string may be used with a production logging tool (PLT) comprising a capacitor array tool, a quartz pressure gauge, a temperature tool, a fullbore spinner flowmeter tool, a fluid density tool, a gama ray tool and an accelerometer to measure hole deviation. The PLT may be used with the multifinger imaging tool  
         [0062]     As discussed above, the storage reel  35  is used with the delivery apparatus  30  to position the COROD string in the wellbore  10 . The storage reel  35  is also used to transport the COROD string to the wellsite. Typically, the storage reel  35  has a circular shape and is placed vertically on a trailer bed (not shown) for transport to the wellsite. However, as the depth of the wellbore increases so must the length of the COROD string. In turn, the diameter of the storage reel  35  also becomes larger. In order, to transport a larger diameter storage reel  35  to the wellsite, the storage reel  35  may be placed on the trailer bed at an angle, such as 45 degrees. Alternatively, the storage reel  35  may be formed in an elliptical shape with the minor axis in a vertical position or an angled position on the trailer bed. At the wellsite, the elliptical shaped storage reel may be transformed in a circular shape by means well known in the art, such as hydraulics. In another arrangement, the storage reel  35  may be folded such as in a “U” shape or “taco” shape and then placed on the trailer bed for transport. At the wellsite, the storage reel  35  may be unfolded and subsequently used with the delivery apparatus  30  to position the COROD string in the wellbore  10 .  
         [0063]      FIG. 8  is a block diagram of a logging system  650  for use with a COROD string  600  in accordance with the present invention. The COROD string  600  is used for transporting a downhole tool  615  into a wellbore. The downhole tool  615  is connected to a memory module  610 .  
         [0064]     The memory module  610  may be used with the COROD string  600  in any configuration described herein. Depending on the configuration of the COROD string  600 , the system  650  may include data acquisition member  605  or a surface acquisition member  620 . For instance, if the COROD string  600  is configured to transmit real time data, then the surface acquisition member  620  will be used and a memory module  610  will act as a log backup. On the other hand, if the COROD string  600  is configured not to transmit real time data, then the data acquisition member  605  will be used and the memory module  610  will act as a data collector. After the data is collected, then the data acquisition member  605  may be used to correlate data from the depth encoder reading and the memory module  610  to define data points at various locations in the wellbore. This information is then used to form a “log” of measured data as a function of depth within the wellbore at which the data was recorded. In this respect, the arrangement of the memory module  610  standardizes the use of the tool  615 , wherein the tool  615  is capable of working with either the data acquisition member  605  when no real time data is transmitted from downhole or the surface acquisition member  620  when real time data is transmitted from downhole. The arrangement of the memory module  610  also allows the tool  615  the capability of working with other types of conveyance members such as wireline, slickline, coiled tubing, or other types of tools such as digital telemetry tools.  
         [0065]     The tool  615  may be any combination of downhole tools, without departing from principles of the present invention. For instance, the tool  615  may include a pulsed neutron lifetime logging tool which is used to identify prospective hydrocarbon zones by measuring neutron capture cross-section of the formation. The tool  615  may also include a spectral saturation tool for use in identifying prospective hydrocarbon zones by comparing hydrogen and chlorine in the formation and for use to determine water saturation of a zone. The tool  615  may also include an SSwT™ pulse neutron tool and capacitance array tools and other production logging tools.  
         [0066]     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.