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CROSS REFERENCE TO RELATED APPLICATIONS 
     This invention claims the benefit under 35 U.S.C. § 119 to U.S. Provisional Application No. 60/352,664, filed on Jan. 29, 2002. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention relates to the field of well completions. More specifically, the invention relates to a device and method for obtaining proper space-out in a well. 
     2. Related Art 
     When completing wells, there is a need to achieve a proper spacing, or space-out, between the well components. The space-out can also affect the force or weight applied to certain downhole components that can affect, among other things, proper sealing and proper function of the components. 
     As an example, it is necessary to perform a wet connect operation in some completions. Such an operation connects a cable or control line (e.g., fiber optic, electrical, hydraulic) contained in an upper string to a cable of same type contained in a lower string that is already part of the permanent completion in the well. Completing the wet connect requires weight to be set down onto the upper string to ensure that the connection is properly made. Likewise, the production string, or final string, that is left in the hole contains pup joints and a tubing hanger. It is necessary to have the right amount of pipe between the tubing hanger and the wet connect so that the appropriate set-down weight can be applied to make up the wet connection with the tubing hanger landed onto the wellhead. 
     In another example, some other types of completions are performed in two stages (a “two stage completion”). For instance, if a conventional gravel pack completion is run, the lower completion is performed with a seal bore packer as the upper most component in the lower completion string. The upper completion is then run with a seal assembly at the bottom. The upper completion can contain components such as a safety valve, permanent gauges, gas lift mandrels, and other completion jewelry. This application also requires a space out to insure the seals are engaged when the upper completed is landed. 
     Obtaining the proper space-out is often not difficult when the wellhead lies only a few hundred feet below the rig floor. In such cases, using the wet connect example for illustration purposes, a service string with the wet connect at its lowest point is lowered into the well in a first run into the well, and the wet connection is made with the appropriate set-down weight. With the wet connection completed, the pipe is marked on the rig floor and the service string is pulled from the well. The marking on the pipe enables space-out calculations and some sections of the service string can be replaced with pup joints and the tubing hanger assembly as appropriate. The modified production string is run in the hole in a second run into the well and the tubing hanger lands on the wellhead ensuring that an appropriate set-down weight is set onto the wet connect. This procedure also applies to the case of the two stage completion. 
     However, when the wellhead is further below the rig floor, a conventional space-out such as the one described above cannot be performed because of high uncertainties in length. Marking the pipe at the surface is insufficient in such a case and will not ensure that the spaceout is correct. 
     SUMMARY 
     In general, according to one embodiment, the present invention provides an apparatus and method for achieving proper space-out of well components. 
     Other features and embodiments will become apparent from the following description, the drawings, and the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The manner in which these objectives and other desirable characteristics can be obtained is explained in the following description and attached drawings in which: 
     FIG. 1 illustrates schematically an embodiment of the present invention showing the upper and lower completions. 
     FIGS. 2 through 5 illustrate schematically an embodiment of the method for obtaining proper space-out of the present invention. 
    
    
     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. 
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible. 
     As used here, the terms “up” and “down”; “upper” and “lower”; “upwardly” and downwardly”; and other like terms indicating relative positions above or below a given point or element are used in this description to more clearly described some embodiments of the invention. However, when applied to equipment and methods for use in wells that are deviated or horizontal, such terms may refer to a left to right, right to left, or other relationship as appropriate. 
     The present invention relates generally to apparatuses and methods for obtaining proper space out of components in wells. For ease of description the following discussion of the invention will focus primarily on one example of use of the space out method, namely making a wet connection downhole. However, the present invention is equally applicable to other situations in which proper space out is desired, such as two stage completions and other situations. 
     FIG. 1 shows a sample completion  10  that has an upper completion  12  and a lower completion  14  in a well  15 . The lower completion  14  in the example has two isolated zones  16 , although more may be completed. In addition, although the completion is shown as a sand control completion, other types of completions may be used. As an example, the completion could be some other form of two stage completion. Each zone is completed with a sand screen  18  and the zones are separated by an isolation packer  20 . A sump packer  22  at the bottom of the completion isolates the lowest zone from the rathole. Within the zones of the example lower completion  14  are various intelligent completion devices  24 ,  26 ,  28  communicating with the surface via a control line  30 . Examples of control lines are electrical, hydraulic, fiber optic and combinations of thereof. Note that the communication provided by the control lines  30  may be with downhole controllers rather than with the surface and the telemetry may include wireless devices and other telemetry devices such as inductive couplers and acoustic devices. An upper packer  32  isolates the uppermost zone. 
     As examples, the intelligent completions devices may comprise gauges, sensors, valves, sampling devices, a device used in intelligent or smart well completion, temperature sensors, pressure sensors, flow-control devices, flow rate measurement devices, oil/water/gas ratio measurement devices, scale detectors, actuators, locks, release mechanisms, equipment sensors (e.g., vibration sensors), sand detection sensors, water detection sensors, data recorders, viscosity sensors, density sensors, bubble point sensors, pH meters, multiphase flow meters, acoustic sand detectors, solid detectors, composition sensors, resistivity array devices and sensors, acoustic devices and sensors, other telemetry devices, near infrared sensors, gamma ray detectors, H 2 S detectors, CO 2  detectors, downhole memory units, downhole controllers, and locators. In addition, the control line itself may comprise an intelligent completions device as in the example of a fiber optic line that provides functionality, such as temperature measurement, pressure measurement, and the like. 
     The annulus around the sand screens  18  may be gravel packed using conventional techniques and equipment. For example, once the lower completion  14  is set in place, a service string may be run into the well to gravel pack the annulus. In other embodiments, a gravel pack is not used. Likewise, the well may be fractured, stimulated, or treated with some other well treatment. As previously mentioned, although the completion is shown as a sand control completion, other types of completions may be used and the present application is not limited to a sand control completion. As an example, the completion could be some other form of two stage completion. For instance, it could have a flow control valve between two packers. 
     The upper completion  12  comprises a production tubing  34  that extends from the upper packer  32  to the surface. The tubing  34  is supported on the wellhead  36  by a tubing hanger  38 . The control line  30  extends along the production tubing  34  to the surface in the embodiment shown. Note that the upper completion  12  may have many other components not shown in the schematic of FIG. 1 (e.g., intelligent completion devices, safety valves, pumps, etc.). 
     In the embodiment used for discussion of the space-out method, the connection of the control line  30  of the upper completion  12  to the control line  30  of the lower completion  14  is made using a wet connect  40 . In general, a wet connect is a connection, such as an electrical connection, a fiber optic connection, or a hydraulic connection that is made downhole as opposed to being made at the surface. In this case, the connection  40  is made downhole to facilitate the placement of the lower completion  14  into the well before the upper completion  12 . In one embodiment, this is useful to allow for conventional gravel packing techniques using a service string that is pulled from the well before introduction of the production string of the upper completion. It is generally considered impractical to have a continuous control line  30  from the surface to the equipment below the upper packer  32  in such a case because the risk of damaging the control line  30  while making multiple trips with different strings is too great. 
     In one embodiment of the present invention, a first completion assembly, the lower completion  14 , is placed in the well. As discussed above, the lower completion  14  comprises, for example, a packer and packer extensions (e.g., circulating housing, safety shear joint, screens, intelligent completions devices, etc.) as well as a control line  30  (e.g., fiber optic, electrical). As shown in FIG. 2, the lower completion  14  also comprises a lower wet connect assembly  42  at its upper end. The schematic of FIG. 2 shows only the top portion of the lower completion  14 . The lower wet connect  42  is used to make up the connection to an upper wet connect assembly  44  of the connection  40 . 
     The lower completion  14  is generally run at the bottom of a service string, which is pulled from the hole when the necessary operations (e.g., setting the packer, gravel packing, etc.) have been performed. In one embodiment of the present invention, the typical service string is replaced with a dummy production string  46  that is very similar to (1) the final production string, (2) the upper completion  12  which contains the tubing hanger and (3) the upper wet connect assembly  44 . However, in the dummy service string  46 , the completion jewelry (e.g., intelligent completion devices, valves, nipples, tubing hanger, wet connect) is replaced by pup joints having substantially the same length as the completion jewelry. In some embodiments the pup joints also have other characteristics, such as diameter, wall thickness, materials, and the like, that are the same as the replaced completion jewelry. 
     In one embodiment, the dummy production string  46  also comprises a measurement device  48  that surrounds the tubing of the dummy production string  46 . Note that other devices that do not surround the tubing or comprise a “ring” may replace the ring  48 . For example, a device may be mounted to one side of the dummy production string  46 . For ease of description, the term “ring” is used to refer to a type of device that is moveable on the string  46  and not to a device having a ring shape necessarily. The term “measurement device” is used herein interchangeably with the term “ring.” The measurement device  48  is positioned at substantially the axial location of the dummy production string  46  that would be occupied by the lower part of the tubing hanger assembly  38  in the upper completion  12 . The axial position of the measurement device  48  is releasably maintained using a shear mechanism, such as a shear pin. Other manners of maintaining the axial position, such as the use of release mechanisms (e.g., dogs, collets, solenoids, sleeves, ratchet teeth) that operate in response to mechanical, electrical, or hydraulic action, may be used in the place of the shear mechanism. As the dummy production string  46  is run into the well  15 , the measurement device  48  will no-go on the wellhead as shown in FIG. 2 (which may indicate the proper setting position for the packer  32 ). At this point in the running operation, before the packer  32  is set, the dummy production string  46  is in tension with the weight of the equipment supported by the tubing  50 . After setting the packer, the amount of weight required for the wet connect  40  to work (i.e., to properly connect) is applied onto the dummy production string  46  causing the shear mechanism to shear and release the measurement device  48  from the tubing. The tubing  50  is now free to slide through the measurement device  48  that is restricted from further downward movement by the wellhead  36 . Thus, the dummy production string  46  is placed in compression with the set-down weight applied. FIG. 3 schematically shows the dummy production string  46  in the set-down, compressed condition and the measurement device  48  positioned relatively higher on the tubing  50 . The difference in the position of the measurement device  48  with respect to the tubing  50  is due to the change in length of the tubing  50  when the load of the tubing changes from tension (FIG. 2) to compression (FIG.  3 ). Note that some desired point on the dummy production string  46 , other than the position of the tubing hanger  38 , can be measured with the technique of the present invention. For example, a point one meter above the tubing hanger position could be measured. 
     The dummy production string  46  further comprises a position lock  52 . The position lock  52  cooperates with the measurement device  48  allowing the measurement device to move upward relative to the tubing  50 , but not allowing the measurement device  48  to move downward with respect to the tubing  50 . In one exemplary embodiment, the position lock  52  is a ratchet mechanism, such as ratchet teeth, formed on the tubing  50  that cooperate with a mating ratchet member on the measurement device  48 . An alternative embodiment of the position lock  52  is a friction device that relies on friction to hold the measurement device in place. So that, when the dummy production string  46  is pulled from the well as shown in FIG. 4, the distance “L” of FIG. 3, which is the correct and proper distance between the tubing hanger and the wet connect, is accurately measured and known. When the dummy production string  46  is pulled from the well  15 , the distance is accurately determined because the position of the measurement device  48  is locked with respect to the tubing. As the service string is removed from the hole, the length (L) is measured on the rig floor, and the actual completion string, with the correct space-out and the completion jewelry is then run in the hole. Accordingly, the measurement device  48  and associated equipment may be referred to generally as a sliding measurement device  54 . 
     In an alternative embodiment, the measurement device  48  and associated equipment is omitted. The relative positions between the tension position and the set-down compressed positions are instead measured in some other manner (e.g., by marking the tubing). Thus, in one example, the dummy production string  46  in the set-down, compressed condition and the tubing  50  is marked to indicate the desired position that the hanger  38 . 
     As the tubing hanger  38  lands on the wellhead  36  (FIG.  5 ), the space-out between the tubing hanger  38  and the wet connect  40  is such that the appropriate weight may be set onto the wet connect  40 . 
     In some applications where high changes in temperature are expected during the life of the well, the upper part of the completion (above the wet connect) may contain an additional anchor placed close to the wet connect  40 . Such an anchor may ensure that enough weight would be applied onto the wet connect throughout the life of the well. 
     Note that the example of the wet connect is one of many possible applications for the space-out method which may be used to accurately space out other equipment in the well. For example, the space out method may be used in two stage completions as well as other completions and situations. Similarly, although the above description primarily describes a sand control completion, the space out method of the present invention may be applied to other types of completions. 
     Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. § 112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function.

Summary:
The present invention provides an apparatus and method for achieving proper space-out of well components. One aspect of the invention utilizes a dummy production string with a sliding measurement device to measure the proper space-out distance.