Abstract:
An improved expandable well screen and associated methods of servicing a subterranean well provide enhanced functionality, while increasing the convenience of manufacture and deployment of the screen, and reducing the screen&#39;s cost. In one described embodiment of the invention, an expandable well screen includes a pleated woven metal filter element disposed overlying a perforated base pipe. When the screen is appropriately positioned within a well, an expanding tool is utilized to radially enlarge the base pipe and filter element.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to a provisional application entitled WELLBORE CASING U.S. Ser. No. 60/111,293, filed Dec. 7, 1998, and having Robert L. Cook, David Brisco, Bruce Stewart, Lev Ring, Richard Haut and Bob Mack as inventors thereof, and to a provisional application entitled ISOLATION OF SUBTERRANEAN ZONES U.S. Ser. No. 60/108,558, filed Nov. 16, 1998, and having Robert L. Cook as an inventor thereof, the disclosure of each of these applications being incorporated herein by this reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to operations performed in conjunction with subterranean wells and, in an embodiment described herein, more particularly provides an improved expandable well screen for use in such operations. 
     It is well known in the art to convey a well screen into a subterranean well in a radially reduced configuration and then, after the screen has been appropriately positioned within the well, to radially expand the screen. Such expandable screens are beneficial where it is desired to position the screen below a restriction in the well, such as a restriction due to damaged casing, variations in open hole wellbore diameter, the need to pass the screen through a relatively small diameter tubular string before placing the screen in operation in a larger diameter tubular string or open hole, etc. 
     Presently available expandable well screens are constructed of multiple circumferentially distributed screen segments overlying an expandable inner tubular member. An outer shroud protects the screen segments against damage as the screen is being conveyed in the well, and ensures that each segment is appropriately positioned in contact with the inner tubular member and the adjacent segment, so that each segment is supported by the inner tubular member and no fluid leakage is permitted between adjacent segments, when the screen is expanded downhole. The inner tubular member has a large number of longitudinally extending slots formed therethrough, with the slots being circumferentially and longitudinally distributed on the tubular member. When the inner tubular member is expanded, each of the slots expands laterally, thereby becoming somewhat diamond-shaped. 
     Unfortunately, there are several problems associated with these types of expandable well screens. For example, manufacture is quite difficult due to the requirement of attaching individual screen segments to the inner tubular member in a circumferentially overlapping manner, and the requirement of positioning the segments within the outer shroud. Construction of the outer shroud is critical, since the shroud must be expandable yet sufficiently strong to maintain each screen segment in contact with an adjacent segment when the screen is expanded. If the screen segments are not in contact with each other, fluid may flow into the screen between the segments. Additionally, the inner tubular member configuration makes it difficult to connect the screen to other tubular members, such as blank sections of tubing, other screens, etc. 
     From the foregoing, it can be seen that it would be quite desirable to provide an improved expandable well screen. It is accordingly an object of the present invention to provide advancements in the technology of expandable well screens. 
     SUMMARY OF THE INVENTION 
     In carrying out the principles of the present invention, in accordance with an embodiment thereof, an expandable well screen is provided in which a filter element thereof is circumferentially pleated. The filter element may circumscribe an inner perforated base pipe. Associated methods are also provided. 
     In one aspect of the present invention, a disclosed well screen includes a filter element which is constructed in a radially compressed pleated configuration. The filter element may be made of a woven metal material. Subsequent radial expansion of the filter element “unpleats” the material, so that the filter element takes on a more circular cross-section. 
     In another aspect of the present invention, the filter element is constructed in multiple layers. An inner layer has openings therethrough of a size which excludes larger particles from passing through the openings, thus filtering fluid flowing through the openings. An outer layer has openings therethrough which are larger than the openings through the inner layer. The outer layer may be utilized to protect the inner layer against damage. 
     In still another aspect of the present invention, the well screen may be utilized in a method of servicing a subterranean well. In the method, the well is gravel packed with the screen in its radially compressed configuration. After gravel has been deposited in an annulus about the screen, the screen is radially enlarged, thereby displacing the gravel in the annulus. 
     In yet another aspect of the present invention, the well screen may be utilized in another method of servicing a subterranean well. In this method, perforations formed outwardly from the wellbore are pre-packed, that is, sand flow inhibiting particulate matter is deposited in the perforations. The screen is then radially enlarged opposite the perforations. In this manner, the screen retains the particulate matter in the perforations. 
     These and other features, advantages, benefits and objects of the present invention will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of representative embodiments of the invention hereinbelow and the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of a well screen embodying principles of the present invention; 
     FIG. 2 is a cross-sectional view through the well screen, taken along line  2 — 2  of FIG. 1; 
     FIG. 3 is an enlarged view of a filter element of the well screen; 
     FIG. 4 is a schematicized view of a first method of servicing a subterranean well, the method embodying principles of the present invention; 
     FIG. 5 is a schematicized view of a second method of servicing a subterranean well, the method embodying principles of the present invention; and 
     FIG. 6 is an enlarged view of a portion of the well of FIG.  5 . 
    
    
     DETAILED DESCRIPTION 
     Representatively illustrated in FIG. 1 is a well screen  10  which embodies principles of the present invention. In the following description of the screen  10  and other apparatus and methods described herein, directional terms, such as “above”, “below”, “upper”, “lower”, etc., are used for convenience in referring to the accompanying drawings. Additionally, it is to be understood that the various embodiments of the present invention described herein may be utilized in various orientations, such as inclined, inverted, horizontal, vertical, etc., without departing from the principles of the present invention. 
     The screen  10  includes a filter element  12 , which is shown in FIG. 1 in its radially compressed pleated configuration. The filter element  12  is generally tubular and is circumferentially pleated, that is, it is folded multiple times circumferentially about its longitudinal axis. In this manner, the filter element  12  circumference as shown in FIG. 1 is substantially smaller than its circumference when it is in an “unpleated” or radially enlarged configuration. As used herein, the term “pleat” is used to include any manner of circumferentially shortening a circumferentially continuous element, and the term “unpleat” is used to include any manner of circumferentially lengthening a previously pleated element. 
     Referring additionally now to FIG. 2, the screen  10  is shown from a cross-sectional view thereof. In this view, it may be more clearly seen how the filter element  12  is folded so that it is alternately creased and thereby circumferentially shortened. In this view it may also be seen that the filter element  12  radially outwardly overlies an inner generally tubular perforated base pipe  14 . The base pipe  14  is optional, since the filter element  12  could be readily utilized in a well without the base pipe. However, use of the base pipe  14  is desirable when its structural rigidity is dictated by well conditions, or when it would be otherwise beneficial to provide additional outward support for the filter element  12 . 
     The base pipe  14  is preferably made of metal and is radially expandable from its configuration shown in FIGS. 1 &amp; 2. Such radial expansion may be accomplished by utilizing any of those conventional methods well known to those skilled in the art. Additional methods are described in the application entitled WELLBORE CASING referred to above. For example, a device commonly known as a “pig” may be forcefully drawn or pushed through the base pipe  14  in order to radially outwardly extend the base pipe&#39;s wall. 
     Note that opposite ends  16  of the base pipe  14  are generally tubular and circumferentially continuous. In this manner, each of the ends  16  may be provided with threads and/or seals, etc. for convenient interconnection of the screen  10  in a tubular string. Specialized expandable end connections are not necessary. Thus, if it is desired to connect the screen  10  to another screen or to a blank (unperforated) tubular section, each end  16  may be connected directly thereto. 
     The filter element  12  is preferably made of a woven metal material. This material is well adapted for use in a filter element which is folded and unfolded, or otherwise pleated and unpleated, in use. The metal material may also be sintered. However, it is to be clearly understood that other materials, other types of materials, and additional materials may be utilized in construction of the filter element  12  without departing from the principles of the present invention. 
     Referring additionally to FIG. 3, an enlarged cross-sectional detail of the filter element  12  is representatively illustrated. In FIG. 3 it may be clearly seen that the filter element  12  is made up of multiple layers  18 ,  20 ,  22 ,  24  of woven material. Fluid (indicated by arrows  26 ) flows inwardly through the layers  18 ,  20 ,  22 ,  24  in the direction shown in FIG. 3 when the screen  10  is utilized in production of fluid from a well. Of course, if the screen  10  is utilized in injection of fluid into a well, the indicated direction of flow of the fluid  26  is reversed. 
     It will be readily appreciated upon a careful examination of FIG. 3 that layer  22  has openings  28  in its weave that are smaller than those of the other layers  18 ,  20 ,  24 . Thus, the layer  22  will exclude any particles larger than the openings  28  from the fluid  26  passing inwardly therethrough. The layers  18 ,  20  inwardly disposed relative to the layer  22  are not necessary, but may be utilized as backup filtering layers in case the layer  22  were to become damaged (e.g., eroded), and may be utilized to provide structural support in the filter element  12 . 
     In one unique feature of the filter element  12 , the layer  24  outwardly the inner layer  22  and has openings  30  in its weave which are larger than the openings  28  through the inner layer  22 . Thus, the outer layer  24  will allow particles to pass therethrough which will not be permitted to pass through the inner layer  22 . However, one of the principle benefits achieved by use of the outer layer  24  is that the inner layer  22  is protected against abrasion, impact, etc. by the outer layer  24  during conveyance, positioning and deployment of the screen  10  in a well. 
     Referring additionally now to FIG. 4, a method  40  of servicing a subterranean well embodying principles of the present invention is representatively and schematically illustrated. In the method  40 , the screen  10  is utilized in a gravel packing operation in which gravel  42  is deposited in an annulus  44  formed between the screen and a wellbore  46  of the well. Methods of depositing the gravel  42  in the annulus  44  about the screen  10  are well known to those skilled in the art and will not be further described herein. However, it is to be clearly understood that a method of servicing a well embodying principles of the present invention may be performed using a variety of techniques for depositing the gravel  42  in the annulus  44  and using a variety of types of gravel (whether naturally occurring or artificially produced). 
     As shown in FIG. 4, the screen  10  is interconnected between a plug or sump packer  48  and a packer  50 . The construction of the screen  10 , particularly the configuration of the base pipe  14  as described above, convenient interconnection of the screen. In actual practice, one or more other tubular members may be interconnected between the screen  10  and each of the plug  48  and the packer  50 . 
     Perforations  52  extend outwardly through casing  54  and cement  56  lining the wellbore  46 . The screen  10  is positioned in the wellbore  46  opposite the perforations  52 . It is not necessary, however, for the screen  10  to be positioned opposite the perforations  52 , nor is it necessary for the perforations to exist at all, in keeping with the principles of the present invention, since the method  40  could alternatively be performed in an open hole section of the well. 
     When the gravel  42  has been deposited in the annulus  44  about the screen  10 , the screen is radially expanded from its initial radially reduced configuration to its radially enlarged configuration. Such radial expansion of the screen  10  redistributes the gravel  42  in the annulus  44 , for example, causing the gravel to displace upwardly about the screen in the annulus, eliminating voids in the gravel, etc. Additionally, radial expansion of the screen  10  may displace a portion of the gravel  42  into the perforations  52 . Note that it is not necessary for the filter element  12  of the screen  10  to be completely unpleated in the method  40 . 
     Referring additionally now to FIG. 5, another method  60  of servicing a subterranean well embodying principles of the present invention is representatively and schematically illustrated. Elements shown in FIG. 5 which are similar to those previously described are indicated in FIG. 5 using the same reference numbers. The screen  10  is depicted interconnected between the plug  48  and the packer  50  in the wellbore  46 , but other positionings and interconnections of the screen may be utilized without departing from the principles of the present invention. 
     In the method  60 , sand flow inhibiting particulate matter  62 , such as gravel, is deposited in the perforations  52 . This operation of depositing the particulate matter  62  in the perforations  52  is commonly referred to as “prepacking” and is well known to those skilled in the art. Therefore, it will not be further described herein. However, it is to be clearly understood that any technique of depositing the particulate matter  62  in the perforations  52  may be utilized without departing from the principles of the present invention. 
     After the particulate matter  62  has been deposited in the perforations  52 , the screen  10  is radially expanded from its initial radially reduced configuration to its radially enlarged configuration as described above. In one unique feature of the method  60 , the filter element  12  contacts the inner side surface of the casing  54  adjacent the perforations  52  when the screen  10  is radially expanded. 
     Referring additionally now to FIG. 6, an enlarged cross-sectional view representatively illustrating the interface between the screen  10  and one of the perforations  52  is shown. In this view it may be clearly seen that the filter element  12  of the screen  10  is in contact with the casing  54  surrounding the illustrated perforation  52 . In this manner, the screen  10  in its radially expanded configuration retains the particulate matter  62  within the perforation  52 . 
     It will be readily appreciated by one skilled in the art that the method  60  eliminates the need for depositing gravel  42  (see FIG. 4) in the annulus  44  about the screen  10  for retaining the particulate matter  62  in the perforations  52 , since the screen itself retains the particulate matter in the perforations. Note that it is not necessary for the filter element  12  of the screen  10  to be completely unpleated in the method  60 . 
     Of course, many modifications, additions, deletions and other changes to the embodiments described above will be apparent to a person of ordinary skill in the art upon consideration of the above descriptions, and these changes are contemplated by the principles of the present invention. Accordingly, the foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims.