Patent Application
20080217002
This invention relates, in general, to a sand control device used during the production of oil, gas or water and a manufacturing process related to the same and, in particular, to a sand control screen having a micro-perforated filtration layer.
Without limiting the scope of the present invention, its background will be described with reference to producing fluid from a subterranean formation, as an example.
After drilling each of the sections of a subterranean wellbore, individual lengths of relatively large diameter metal tubulars are typically secured together to form a casing string that is positioned within each section of the wellbore and cemented in place. This casing string is used to increase the integrity of the wellbore by preventing the wall of the hole from collapsing and to prevent movement of fluids from one formation to another formation.
Once the process of drilling and installing casing is finished, the completion process may begin. The completion process comprises numerous steps including the creation of hydraulic openings or perforations through the casing string, the cement and a short distance into the desired formation or formations so that production fluids may enter the interior of the wellbore. In addition, the completion process may involve formation stimulation to enhance production, installation of sand control devices to prevent sand production and the like. The completion process also includes installing a production tubing string within the well casing. Unlike the casing string that forms a part of the wellbore itself, the production tubing string is used to produce the well by providing the conduit for formation fluids to travel from the formation depth to the surface.
Typically, the production tubing string extends from the surface to the formations traversed by the well and includes one or more production packers. The purpose of the packers is to support the production tubing and other completion equipment, such as one or more sand control screens that may be placed adjacent to the producing formations, and to seal the annulus between the outside of the production tubing and the inside of the well casing to block movement of fluids through the annulus past the packer locations. Accordingly, once the production tubing string, including the production packers and sand control screens are in place, all production from the formation that enters the production tubing must pass through a sand control screen.
One purpose of the sand control screens is to prevent the movement of unconsolidated formation particles such as sand into the production tubing. Such particle movement commonly occurs during production from completions in loose sandstone or following hydraulic fracture of a formation. Production of these materials causes numerous problems in the operation of oil, gas or water wells. These problems include plugging of formations, tubing and flow lines, as well as erosion of tubing, downhole equipment and surface equipment. These problems lead to poor productivity, high maintenance costs and unacceptable well downtime.
Existing screens typically use a wire wrap filter media or a wire mesh filter media attached to a base pipe to achieve sand control. Wire wrap sand screens may comprise a continuous single wire wrapped around the base pipe. More recent versions use a jacket that is fully formed from a single wire prior to attachment to the base pipe, with vertical ribs providing a stand-off from the base pipe. Variations in the gauge of wire and corresponding variations in the spacing between wraps of the wire provide sand screens for different conditions. Wire mesh sand screens use one or more woven metal layers to trap particulate matter. As with wire wrap screens, wire mesh sand screens are available in a number of gauges having openings of various sizes.
In addition, some screen designs use prepacked sand confined around the perforated base pipe. These prepacked screens are constructed by fabricating the metal components, then forcing pack sand, either resin coated or uncoated, between the perforated base pipe and an inner wire screen or between an inner wire screen and an outer wire screen of a multi-layer screen. Alternatively or additionally, a gravel pack may be placed in the production interval surrounding the installed sand control screens.
It has been found, however, that existing sand screens continue to have a number of drawbacks. For example, variations in the gauge of the wire or improper manufacture can result in inconsistencies in the opening size. Larger gauges of wire become increasingly difficult to bend, while smaller gauges are more easily damaged in the processes of manufacture and installation or during production. Additionally, screens that use multiple filter layers are, by their nature, difficult or impossible to clean. Still further, the attachment of the wire wrap screen or wire mesh screen to the base pipe is an ongoing cause of concern. The sand screen filters are typically attached to the base pipe with conventional welding at both ends of the filter layer. A failure of any portion of the weld results in an uncontrolled opening and a loss of sand control. Therefore, a need has arisen for a sand screen that provides the desired sand control function, is robust, easy to clean and simple to manufacture.
The present invention disclosed herein comprises a sand control screen having a micro-perforated filter layer for filtering particles out of fluid produced from a wellbore and a method for manufacturing the same. The sand screen of the present invention allows for precise, reliably reproducible and infinitely variable opening size, shape, density and pattern in the micro-perforated filter layer, thereby providing the desired sand control function. In addition, the sand control screen of the present invention is robust, easy to clean and simple to manufacture.
The sand control screen having a micro-perforated filter layer of the present invention includes a base pipe having a plurality of openings that allow fluid flow therethrough and a filter layer having a plurality of micro-perforations. The filter layer wraps around the base pipe and is attached thereto. A drainage layer such as channels, wire wrap or wire mesh between the base pipe and filter layer allows production fluid to flow between the filter layer and the base pipe.
In one embodiment of the sand control screen having a micro-perforated filter layer, the filter layer is made of sheet metal that is wrapped around the base pipe. The sheet metal may be flat or corrugated. In the flat sheet metal embodiments of the sand control screen, channels may be formed in the outside surface of the base pipe or on the inside surface of the filter layer. In the corrugated sheet metal embodiments of the sand control screen, the corrugations form the channels between the filter layer and the base pipe.
The filter layer may be attached to the base pipe using a variety of techniques including fusion bonding, a friction fit, adhesives or the like. Alternatively or additionally, the filter layer may be attached to the base pipe using connectors, such as end caps, that seal the ends of the filter layer to the base pipe. The end caps may be attached to the base pipe using welded, threading or similar techniques.
In some embodiments of the sand control screen, the filter layer has a thickness between about 1/32nd inch and about ¼th inch. In other embodiments, the opening shape of the micro-perforations at the surface of the filter layer can be a circle, an ellipse, a slot or other similar shape having a radius. Alternatively, the opening shape of the micro-perforations at the surface of the filter layer may have sharp edges such as squares, rectangles, triangles or other multi sided polygon or shape. In certain embodiments, the micro-perforations may have a tapering cross-section through the filter layer wherein the smaller opening of this tapering cross-section may be oriented to either the exterior or the interior of the filter layer.
In one embodiment of the sand control screen having a micro-perforated filter layer, the opening size of the micro-perforations has a maximum width of 500 microns. In other embodiments, the maximum width of the micro-perforations is between about 50 microns and 500 microns. In another embodiment of the sand control screen having a micro-perforated filter layer, the opening density of the micro-perforations is between about 100 and 200 openings per square inch. In other embodiments, the opening density of the micro-perforations may be less than 100 openings per inch or more than 200 openings per inch.
In one embodiment of the sand control screen having a micro-perforated filter layer, the opening pattern of the micro-perforations has a uniform distribution. In other embodiments, the opening pattern may include a nonuniform or selected distribution. For example, in the corrugated sheet metal embodiment, the micro-perforations can be placed at the peaks and valleys of the corrugations, in the sides of the corrugations or in any other arrangement that is desired. The size, shape, density and pattern of the micro-perforations are determined by the desired flow area, the desired filtration capacity, the constituents being separated from one another and the like.
In another aspect, the present invention is directed to a method of making a sand control screen that includes fabricating a plurality of openings in the wall of a base pipe and creating a plurality of micro-perforations in a length of sheet metal having a first and a second edge opposite each other to form a filtration media. The method further includes forming a plurality of channels that allow fluid flow between the filter layer and the base pipe, shaping the filter layer to fit around the base pipe, bringing the first edge and the second edge of the filter layer substantially adjacent each other, attaching the filter layer to the outer surface of the base pipe and coupling the first edge of the filter layer to the second edge.
In some embodiments, the step of creating a plurality of micro-perforations in a length of sheet metal may be accomplished using a water jet, a laser or similar technique. In certain installations, the steps of shaping the filter layer to fit around the base pipe, bringing the first edge and the second edge of the filter layer substantially adjacent each other, attaching the filter layer to the outer surface of the base pipe and coupling the first edge of the filter layer to the second edge may be performed at the location where the sand screen will be used.
For a more complete understanding of the features and advantages of the present invention, references now made to the detailed description of the invention along with the accompanying figures in which corresponding numerals in the different figures refer to corresponding parts and in which:
While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts which can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention, and do not delimit the scope of the invention.
Referring now to
Even though
Referring to
The typical opening sizes in existing sand screens, e.g., 100-300 microns, can be reproduced in the micro-perforated filter layer 50. Additionally, both larger and smaller opening sizes can be provided in the disclosed micro-perforated filter layer 50 without the manufacturing difficulties encountered when these sizes are manufactured in either wire wrap or wire mesh sand control screens. A wide variety of intermediate size openings can also be easily produced. Micro-perforated opening sizes for the disclosed micro-perforated filter layer can range between 50 and 500 microns, providing opening sizes that are not currently available from any manufacturer.
Due to the manufacturing processes used to create filter layer 50, the shape of micro-perforations 52 is precisely controllable and reliably reproducible. In the illustrated embodiment, micro-perforations 52 are depicted as circular, however, micro-perforations 52 may also be formed in the shape of an ellipse, a slot or other similar shape having a radius. Alternatively, micro-perforations 52 may have sharp edges such as squares, rectangles, triangles or other multi sided polygon or shape.
Due to the tight tolerances available in the manufacturing process used to create filter layer 50, the density and pattern of micro-perforations 52 are precisely controllable and reliably reproducible. For example, the opening density of micro-perforations 52 may be between about 100 and 200 openings per square inch. Opening densities both less than 100 openings per inch and more than 200 openings per inch are also contemplated by the present invention. The opening pattern of micro-perforations 52 can have a uniform distribution or a nonuniform distribution. With the infinitely variable opening size, shape, density and pattern in the micro-perforated filter layer available with the present invention, certain embodiments of the micro-perforated filter layer not only allow for filtration of particles from production fluids but also allow for separation of fluid constituents from one another. For example, the micro-perforations may be configured to allow the production of hydrocarbon fluids therethrough but prevent the production of water therethrough. Likewise, the micro-perforations may be configured to allow the production of liquid hydrocarbons therethrough but prevent the production of hydrocarbon gases therethrough.
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Filter layer 50 is a surface-type filter, which removes particles that are entrained in the production fluid at the surface of the filter. Because the particles remain on the surface, filter layer 50 is inherently easy to clean as particles can be washed away by a back-flow of fluid. This ability contrasts with depth filters, which trap the particles within the filter and are inherently difficult or impossible to clean.
Referring now to
With reference now to
When the micro-perforated filter layer is corrugated, the placement of the micro-perforations can be varied as necessary or desirable to prevent long term plugging of the filter and to maintain the desired flow area. With reference now to
The use of a corrugated filter layer with the sand control screen of the present invention provides certain advantages over the non-corrugated embodiments. For example, the addition of corrugations to the filter layer provides an increased flow area over the non-corrugated version. Additionally, the corrugated configuration reduces thermal effects relative to the bond between the filter layer and the base pipe.
With reference now to
Referring now to
Micro-perforating results in more reliably shaped and sized openings than either wire wrapping or wire mesh screen methods, while tolerances for spacing of openings can be more easily controlled. Virtually infinitely variable screen ratings can be provided by varying the size, shape, density and pattern of the micro-perforations. Very small micron ratings can be produced by micro-perforation without loss of strength in the filter material. Similarly, large micron ratings formed by micro-perforation do not require the manipulations of large gauge wire and can be produced in sizes previously impossible to manufacture.
Once the sheet metal is micro-perforated to create the filter layer, channels are provided in step 404 to allow fluid flow between the filter layer and the base pipe. For corrugated embodiments of the micro-perforated filter layer, the corrugations of the filter layer are designed to form channels between the filter layer and the base pipe when the filter layer and base pipe are attached. For non-corrugated embodiments, channels are formed in either the outer surface of the base pipe or in the surface that will be the interior surface of the filter layer. In a preferred embodiment, the base pipe is placed in a knurling machine and knurls are created while the pipe is rotated, creating a spiral pattern of channels down the length of the base pipe that will lie under the filter layer. Cross-connections between adjacent channels can also be formed to increase available cross-flow.
The filter layer is shaped to fit around the base pipe in step 406 and the filter layer and base pipe are attached to each other in step 408. In one embodiment, the filter layer is fusion bonded to the base pipe to form a direct metal-to-metal attachment. In fusion bonding, the filter layer and the base pipe are placed in close contact with each other. A high current is run through the adjacent filter layer and base pipe, causing the two pieces to fuse. With this technique, the filter layer can be attached to the base pipe along the entire length of the filter layer, providing an extremely strong attachment. End caps, if necessary or desired, can be added as part of this step. Once the filter layer is attached to the base pipe, the edges of the filter layer are sealed to each other. In at least one embodiment, a seam weld is applied down the full length of the filter layer, sealing the edges of the filter layer together and forming a true one-piece, 360° filter.
In another embodiment of the attachment method, a friction fit is used to join the filter layer to the base pipe. The filter layer is first joined to itself to create an open-ended cylindrical shape that is sized to fit snugly over the base pipe. The cylindrical filter layer is then heated to increase the diameter across the filter and slipped over the base pipe. When sized properly, the cooled filter layer forms a tight fit to the base pipe.
One of ordinary skill in the art will realize that other methods of attachment can also be used without deviating from the scope of the invention. For example, a glue or other bond-inducing chemical means can be used. Additionally, a variety of connections, such as threads, screws or welds provide another means of attachment.
The disclosed method of manufacturing a sand control screen provides a number of advantages over current manufacturing methods for sand screens. The most critical step in the production of the present sand control screen is micro-perforating the sheet metal. This step can be performed under controlled conditions to produce reliable opening sizes and shapes with close tolerances in the spacing. The later steps of shaping the sheet metal and attaching the shaped filter layer to the base pipe can be performed in less controlled conditions without adversely affecting the quality of the sand control screen. Final assembly can be performed closer to the point of use, such as at the well site. Overhead can also be reduced by stocking only the micro-perforated sheet metal and assembling the sand control screens on user-provided base pipe. Specific configurations of micro-perforations can be produced quickly and shipped to the site to provide a custom-made filter that more closely meets the need of the user's than the stock sizes currently available.
The disclosed sand control screen having a micro-perforated filter layer also provides additional advantages over existing sand control screens. The use of a micro-perforated filter layer can result in a sand control screen having a reduced outside diameter for a given base pipe size. The decreased outside diameter and strong attachment can make installation easier and may allow an increased base pipe size for a given hole diameter. Additionally, the attachment of the filter layer and base pipe along the entire length of the filter layer provides a strong attachment with a lower incidence of detachment. Manufacturing costs are decreased, while the quality and durability of the filter are increased.
While this invention has been described with a reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to the description. It is, therefore, intended that the appended claims encompass any such modifications or embodiments.
