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FIELD OF THE INVENTION 
     The present invention relates generally to the production of reservoir fluids, and particularly to a well construction technique that utilizes an insertion guide placed in an open-hole section of a wellbore. 
     BACKGROUND OF THE INVENTION 
     In the conventional construction of wells for the production of petroleum and gas products, a wellbore is drilled through a geological formation to a reservoir of the desired production fluids. For a variety of reasons, e.g. local geology and strength of formation, tortuosity of the well, quality of drilling fluid, diameter of tubing, etc., the usable diameter of the wellbore tends to decrease with depth. Consequently, the suite of casings, liners and/or completion tubulars becomes sequentially smaller in diameter when progressing downhole. The diameter reduction is necessary both to compensate for the narrowing usable space of the wellbore in the open-hole section of the well and to permit insertion of the latest tubular through the previous tubular. In many cases, the diameter of the subsequent tubular element must be at least one and a half inches smaller than the inside diameter of the open-hole section of the well. 
     The diameter reduction generates an open-flow annulus between the formation or wellbore wall and the tubular component. Generally, this open-flow annulus is undesirable. Outside the reservoir region, the open-flow annular space often is cemented to provide isolation between the formation and the adjacent tubular component. This avoids corrosion of the tubular component, axial migration of liquids and gas along the annulus and other undesirable effects. 
     Within the reservoir region, hydraulic communication from the formation to the wellbore is necessary for the production of the reservoir fluids. The open-flow annular space can be cemented or kept open. When this annular is cemented, the formation is later put back in communication with the wellbore by perforating the casing and the cement sheath. This technique permits good isolation of different intervals of the reservoir. If this annular is not cemented, we can maximize the contact between the formation and the wellbore but then it becomes much more difficult to get isolation between different intervals. In both cases, cemented or not cemented, the loss of diameter of the completion relative to the diameter of the open hole can be detrimental to maximizing productivity of the well. For example, if the completion is a slotted liner or sand control screen, the necessarily smaller diameter of the liner or screen reduces the section available for flow. Also, as mentioned above, the presence of the open annulus creates difficulty in isolating specific intervals of the formation. As a result, selective sensing of production parameters as well as selective treatment, e.g. stimulation, consolidation or gas and water shut-off, of specific intervals of the formation is difficult, if not impossible. Additionally, in certain wells prone to sand production, the particulates can freely wash along the annulus, repeatedly hitting the completion and causing wear or erosion of the completion. 
     Because of these problems, most operators continue to cement and perforate casings and liners set in reservoirs so as to allow repair of well problems over the life of the well. Completions, such as slotted liners and screens, are only used in cases where production problems are not anticipated or where cost is an issue. Some attempts have been made to minimize diameter reduction from one piece of tubular to the next and to eliminate or reduce the open annulus without resorting to cementing, but the attempts have met with limited success. 
     For example, one method is to simply improve the drilling and well conditions to minimize diameter reduction. Such improvement may include controlling the well trajectory and selecting high performance muds. Although this approach may slightly reduce the size of the open annulus surrounding the completion, a substantial open annulus still remains. 
     Another attempt to alleviate the problems of diameter reduction and open annulus involves drilling new sections of the wellbore with a larger diameter than the previous tubular. This can be achieved with a bi-center bit, for example. With the increased diameter of the subsequent wellbore portion, the next succeeding section of tubular can be provided with an outside diameter very close to the inside diameter of the previous tubular. However, the open-flow annulus in the open-hole section of the wellbore still remains. 
     More recently, expandable tubular completions have been introduced. In this approach, a tubular completion is inserted into an open-hole section of the wellbore in a reduced diameter form. The completion is then expanded against the formation, i.e. against the open-hole sides of the wellbore. This approach helps alleviate the diameter reduction problem as well as the problem of open-flow annular space. However, in some applications additional problems can arise. If the well is not in good gauge, for example, there can still be communication of well fluids external of the tubular completion. There may also be limits on the types of completions that may be utilized. 
     SUMMARY OF THE INVENTION 
     The present invention features a technique for reducing or eliminating the diameter reduction and annular space problems without incurring the difficulties of previously attempted solutions. The technique utilizes an insertion guide that is introduced into an open-hole section of the wellbore. The insertion guide is moved through the wellbore in a contracted state. Once placed in its desired location, the insertion guide is expanded, e.g. deformed, radially outwardly at least partially against the formation, i.e. against the wall of the wellbore. Subsequent to expansion of the insertion guide, a final completion element, e.g. a tubular completion component, is deployed within the insertion guide. 
     Typically, the outside diameter of the completion element is selected such that it is nearly equal to the inside diameter of the insertion guide subsequent to expansion. Thus, the outside diameter of the completion element diameter is nearly equal the nominal inside diameter of the open-hole reduced only by the thickness of the wall of the insertion guide. Consequently, the completion element is readily removable while having a larger diameter than otherwise possible. Additionally, the detrimental annular space is substantially if not completely eliminated. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and: 
     FIG. 1 is a front elevational view of an exemplary insertion guide system disposed within a wellbore; 
     FIG. 2 is a front elevational view of the insertion guide of FIG. 1 being expanded at a desired location; 
     FIG. 3 is a front elevational view similar to FIG. 2 but showing an alternate technique for expansion; 
     FIG. 4 is a front elevational view of an expanded insertion guide having a solid wall; 
     FIG. 5 is a front elevational view of an expanded insertion guide having multiple openings for fluid flow therethrough; 
     FIG. 6 is a cross-sectional view of an exemplary insertion guide; 
     FIG. 7 is a cross-sectional. view illustrating an alternate embodiment of the insertion guide; 
     FIG. 8 is a cross-sectional view illustrating another alternate embodiment of the insertion guide; 
     FIG. 8A is a cross-sectional view illustrating another alternate embodiment of the insertion guide; 
     FIG. 9 is a front elevational view of an insertion guide having a sand screen completion element disposed therein; 
     FIG. 10 is a front elevational view of an insertion guide having an external axial flow inhibitor; 
     FIG. 11 is a view similar to FIG. 10 but showing an internal axial flow inhibitor; 
     FIG. 12 illustrates an insertion guide having one or more signal communication leads as well as one or more tools, e.g. sensors, incorporated therewith; and 
     FIG. 13 is a diagrammatic illustration of one technique for deploying the insertion guide into a wellbore while in its contracted state. 
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The present technique utilizes an insertion guide that may be introduced into a variety of subterranean environments. Typically, the insertion guide is deployed through a wellbore while in a reduced diameter state. The insertion guide is then expanded against the formation at a desired location to permit insertion of a final completion with a full size diameter. 
     Referring generally to FIG. 1, an exemplary insertion guide  20  is illustrated in an expanded state deployed in a subterranean, geological formation  22 . In the illustrated embodiment, the insertion guide  20  is utilized in a well  24  accessed by a wellbore  26 . The exemplary wellbore  26  comprises a generally vertical section  28  and a lateral section  30 . Insertion guide  20  can be placed at a variety of locations along wellbore  26 , but an exemplary location is in a reservoir or reservoir region  32  to facilitate the flow of desired production fluids into wellbore  26 . Non-reservoir regions  34  also exist in subterranean formation  22 . 
     In many applications, wellbore  26  extends into subterranean formation  22  from a wellhead  36  disposed generally at a formation surface  38 . The wellbore extends through subterranean formation  22  to reservoir region  32 . Furthermore, wellbore  26  typically is lined with one or more tubular sections  40 , such as a liner. 
     Typically, insertion guide  20  is disposed in an open-hole region  42  of wellbore  26  subsequent to tubular sections  40 . In other applications, the insertion guide can be placed within a cased wellbore. Thus, when insertion guide  20  is expanded, e.g. deformed to its expanded state, an insertion guide sidewall  44  is effectively moved radially outwardly to reduce the annular space between the insertion guide  20  and the formation in open-hole region  42  or cased wellbore section. In one typical application, the insertion guide  20  is expanded outwardly to abut against the formation, thereby minimizing annular space as more fully described below. 
     Upon expansion of insertion guide  20 , a final completion  46  is inserted into an interior  47  of the insertion guide, as illustrated in FIG.  1 . Although a gap between final completion  46  and the interior of insertion guide  20  is illustrated in FIG. 1 to facilitate explanation, the final completion can and often will have an outside diameter that is very close in size to the inside diameter of insertion guide  20 . Consequently, very little annular space exists between final completion element  46  and insertion guide  20 . The final completion  46  may be deployed by a variety of known mechanisms, including a deployment tubing  48 . Other mechanisms comprise cable, wireline, drill pipe, coiled tubing, etc. 
     Expansion of insertion guide  20  at a desired location within wellbore  26  can be accomplished in several different ways. As illustrated in FIG. 2, the insertion guide may be connected to a lead end of final completion  46  and delivered to the appropriate open-hole location within wellbore  26 . This allows the insertion guide and the internal completion element to be deployed with a single run into the well. 
     In this embodiment, final completion  46  is coupled to insertion guide  20  by an appropriate coupling mechanism  50 . Coupling mechanism  50  may include a sloped or conical lead end  52  to facilitate expansion of insertion guide  20  from a contracted state  54  (see right side of insertion guide  20  in FIG. 2) to an expanded state  56  (see left side of FIG.  2 ). As the sloped lead end  52  and final completion  46  are moved through insertion guide  20 , the entire insertion guide is changed from the contracted state  54  to the expanded state  56 . Other coupling mechanisms also may be utilized to expand insertion guide  20 , such as bicenter rollers. Expansion also can be accomplished by pressurizing the insertion guide or by relying on stored energy of insertion guide  20 . 
     In an alternate embodiment, as illustrated in FIG. 3, insertion guide  20  is delivered to a desired location within the wellbore during an initial run downhole via deployment tubing  48 . The insertion guide  20  is mounted between deployment tubing  48  and a spreader mechanism  58  disposed generally at the lead end of insertion guide  20 . Spreader mechanism  50  has a conical or otherwise sloped lead surface  60  to facilitate conversion of insertion guide  20  from its contracted state to its expanded state. As illustrated in FIG. 3, spreader mechanism  58  is pulled through insertion guide  20  by an appropriate pulling cable  62  or other mechanism. Once spreader mechanism  58  is pulled through insertion guide  20 , the spreader mechanism  58  is retrieved through wellbore  26 , and final completion  46  is deployed within the expanded insertion guide during a second run into the well. 
     Insertion guide  20  may be formed in a variety of sizes, shapes, cross-sectional configurations and wall types. For example, insertion guide sidewall  44  may be a solid wall, as illustrated in FIG. 4. A solid-walled insertion guide  20  typically is used in a non-reservoir region, such as one of the non-reservoir regions  34 . In a reservoir region, such as region  32 , insertion guide  20  typically comprises a plurality of flow passages  64 , as best illustrated in FIG.  5 . Flow passages  64  permit fluid, such as the desired production fluid, to flow from reservoir region  32  through insertion guide  20  and into wellbore  26 . Illustrated flow passages  64  are radially oriented, circular openings, but they are merely exemplary passages and a variety of arrangements and configurations of the openings can be utilized. Additionally, the density and number of openings can be adjusted for the specific application. 
     Expandability of insertion guide  20  may be accomplished in a variety of ways. Examples of cross-sectional configurations amenable to expansion are illustrated in FIGS. 6,  7  and  8 . As illustrated specifically in FIG. 6, the insertion guide sidewall  44  comprises a plurality of openings  66  that become flow passages  64 , e.g. radial flow passages, upon expansion. In this embodiment, openings  66  are formed along the length of insertion guide  20  and upon deforming of insertion guide  20 , the openings  66  are stretched into broader openings. The configuration of slots  66  and the resultant openings  64  may vary substantially. For example, openings  66  may be in the form of slots, holes or a variety of geometric or asymmetric shapes. 
     In an alternate embodiment, sidewall  44  is formed as a corrugated or undulating sidewall, as best illustrated in FIG.  7 . The corrugation allows insertion guide  20  to remain in a contracted state during deployment. However, after reaching a desired location, an appropriate expansion tool is moved through the center opening of the insertion guide forcing the sidewall to a more circular configuration. This deformation again converts the insertion guide to an expanded state. The undulations  68  typically extend along the entire circumference of sidewall  44 . Additionally, a plurality of slots or openings  70  may be formed through sidewall  44  to permit fluid flow through side wall  44 . 
     Another exemplary embodiment is illustrated in FIG.  8 . In this embodiment, sidewall  44  comprises an overlapped region  72  having an inner overlap portion  74  and an outer overlap portion  76 . When outer overlap  76  lies against inner overlap  74 , the insertion guide  20  is in its contracted state for introduction through wellbore  26 . Upon placement of the insertion guide at a desired location, an expansion tool is moved through the interior of insertion guide  20  to expand the sidewall  44 . Essentially, inner overlap  74  is slid past outer overlap  76  to permit formation of a generally circular, expanded insertion guide  20 . As with the other exemplary embodiments, this particular embodiment may comprise a plurality of slots or openings  78  to permit the flow of fluids through sidewall  44 . 
     In FIG. 8A, another embodiment is illustrated in which a portion  79  of sidewall  44  is deformed radially inward in the contracted state to form a generally kidney-shaped cross-section. When this insertion guide is expanded, portion  79  is forced radially outward to a generally circular, expanded configuration. 
     Many types of final completions can be used in the present technique. For example, various tubular completions, such as liners and sand screens may be deployed within an interior  80  of the expanded insertion guide  20 . In FIG. 9, a sand screen  82  is illustrated within interior  80 . This type of completion generally comprises a filter material  84  able to filter sand and other particulates from incoming fluids prior to production of the fluids. Because of the expandable insertion guide, the sand screen  82  may have a full size diameter while retaining its ability to be removed from the wellbore. Additionally, the risk of damaging sand screen  82  during installation is minimized, and the most advanced filter designs can be inserted because there is no requirement for expansion of the sand screen itself. 
     In some environments, it may be desirable to compartmentalize the reservoir region  32  along insertion guide  20 . As illustrated in FIG. 10, an axial flow inhibitor  86  is combined with insertion guide  20 . Axial flow inhibitor  86  is designed to act between insertion guide sidewall  44  and geological formation  22 , e.g., the open-hole wall of wellbore  26  proximate insertion guide  20 . Inhibitor  86  limits the flow of fluids in an axial direction between sidewall  44  and formation  22  to allow for better sensing and/or control of a variety of reservoir parameters, as discussed above. 
     In the embodiment illustrated, axial flow inhibitor  86  comprises a plurality of seal members  88  that extend circumferentially around insertion guide  20 . Seal members  88  may be formed from a variety of materials including elastomeric materials, e.g. polymeric materials injected through sidewall  44 . Additionally, seal members  88  and/or portions of sidewall  44  can be formed from swelling materials that expand to facilitate compartmentalization of the reservoir. In fact, the insertion guide  20  may be made partially or completely of swelling materials that contribute to a better isolation of the wellbore. Also, axial flow inhibitor  86  may comprise fluid based separators, such as Annular Gel Packs available from Schlumberger Corporation, elastomers, baffles, labyrinth seals or mechanical formations formed on the insertion guide itself. 
     Additionally or in the alternative, an internal axial flow inhibitor  90  can be deployed to extend radially inwardly from an interior surface  92  of insertion guide sidewall  44 . An exemplary internal axial flow inhibitor comprises a labyrinth  94  of rings, knobs, protrusions or other extensions that create a tortuous path to inhibit axial flow of fluid in the typically small annular space between interior surface  92  of insertion guide and the exterior of completion  46 . In the embodiment illustrated, labyrinth  94  is formed by a plurality of circumferential rings  96 . However, it should be noted that both external axial flow inhibitor  86  and internal axial flow inhibitor  90  can be formed in a variety of configurations and from a variety of materials depending on desired design parameters for a specific application. 
     Insertion guide  20  also may be designed as a “smart” guide. As illustrated in FIG. 12, an exemplary insertion guide comprises one or more signal carriers  98 , such as conductive wires or optical fiber. The signal carriers  98  are available to carry signals to and from a variety of instruments or tools. The instrumentation and/or tools can be separate from or combined with insertion guide  20 . In the embodiment illustrated, for example, a plurality of sensors  100 , such as temperature sensors, pressure sensors, flow rate sensors etc., are integrated into or attached to insertion guide  20 . The sensors are coupled to signal carriers  98  to provide appropriate output signals indicative of wellbore and production related parameters. Additionally, well treatment tools may be incorporated into the system to selectively treat, e.g. stimulate, the well. 
     Depending on the type of completion and deployment system, signal carriers  98  and the desired instrumentation and/or tools can be deployed in a variety of ways. For example, if the signal carriers, instrumentation or tools tend to be components that suffer from wear, those components may be incorporated with the completion and/or deployment system. In one implementation, instruments are deployed in or on the insertion guide and coupled to signal carriers attached to or incorporated within the completion and deployment system. The coupling may comprise, for example, an inductive coupling. Alternatively, the instrumentation and/or tools may be incorporated with the completion and designed for communication through signal carriers deployed along or in the insertion guide  20 . In other embodiments, the signal carriers as well as instrumentation and tools can be incorporated solely in either the insertion guide  20  or the completion and deployment system. The exact configuration depends on a variety of application and environmental considerations. 
     Referring generally to FIG. 13, one exemplary way of introducing insertion guide  20  into a wellbore in its contracted state is via a reel  102 . The use of a reel  102  is particularly advantageous when relatively long sections of insertion guide are introduced into wellbore  26 . Reel  102  can be designed similar to reels used in the deployment and retrieval of coiled tubing. With such designs, the insertion guide is readily unrolled into wellbore  26 . Reel  102  also permits retrieval of insertion guide  20 , if necessary, prior to expansion of the guide at its desired wellbore location. 
     It should be understood that the foregoing description is of exemplary embodiments of this invention, and that the invention is not limited to the specific forms shown. For example, the insertion guide may be made in various lengths and diameters; the insertion guide may be designed with differing degrees of expandability; a variety of completion components may be deployed within the insertion guide; the insertion guide may comprise or cooperate with a variety of tools and instrumentation; and the mechanisms for expanding the insertion guide may vary, depending on the particular application and desired design characteristics. These and other modifications may be made in the design and arrangement of the elements without departing from the scope of the invention as expressed in the appended claims.

Summary:
A technique for facilitating the use of a variety of completion elements in a wellbore environment. The technique utilizes an insertion guide disposed within an open-hole section of a wellbore. The insertion guide may be radially expanded towards the surrounding formation to remove excess annular space. The expansion of the insertion guide further allows the use of a completion element having a greater diameter than would otherwise be afforded.