Patent Application
20080105437
In many wellbore applications, sand laden fluids are filtered to return a clean fluid to the surface or to dehydrate a slurry at a desired location in a wellbore. The filtering is performed by a filtering media created from a wire wrapped or wire mesh structure. This type of filtering media is susceptible to plugging over a period time which can cause premature job failure.
Attempts have been made to reduce plugging by using powered tools associated with the filtering media. For example, screens have been designed with rotatable sleeves to help reduce plugging. Other screens utilize movable components that can be actuated to close off the screen during certain operations. However, such devices have limited effectiveness. Additionally, these devices tend to be complex, expensive devices requiring a power source for operation.
In general, the present invention provides a system and method of filtering in a wellbore during various well related operations. A well screen is combined with a tool string for movement downhole into a wellbore. The well screen may be flexed via pressure differentials created across the well screen. For example, pressure inputs create pressure differentials able to flex the well screen between a normal mode and one or more deflection modes. Examples of deflection modes comprise a radially inward deflection mode and/or a radially outward deflection mode. Once the actuating pressure differential is diminished, the well screen automatically returns to the normal mode. The flexing of the well screen is used for adjusting flow gap size and for removing accumulated materials to unplug the well screen for continued use, thereby avoiding premature job failure.
Certain embodiments of the invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and:
In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those of ordinary skill 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.
The present invention generally relates to a system and methodology for filtering particulates from a fluid stream at a location within a wellbore. A compliant well screen is moved downhole into a wellbore for use in one or more well related operations. The well screen is compliant and cooperates with the overall system in a manner that enables removal of or prevention of plugging along the well screen. The well screen also can be used to facilitate downhole operations, such as the dehydration of a slurry in the wellbore. The compliant well screen is flexed between different modes of deflection via differential pressures across the well screen. For example, the pressure inputs resulting from the differential pressures across the well screen can be used to flex the well screen between a normal or intermediate mode and, for example, a radially inward mode of deflection or a radially outward mode of deflection.
Referring generally to
In the example illustrated, wellbore assembly 22 further comprises a well screen 44 that is carried downhole into wellbore 26 on a tool string 46. Well screen 44 is a compliant well screen that may be moved between a plurality of deflection modes via pressure differentials created between an exterior region 48 surrounding well screen 44 and an interior region 50 within well screen 44 and tool string 46. Tool string 46 may be formed in a variety of configurations and with a variety of components depending on the specific well application for which it is designed. In some operations, for example, tool string 46 comprises a bottom hole assembly 52 coupled to a tubing 54. However, other components and component arrangements can be used with well screen 44 to facilitate a variety of well related operations.
One embodiment of well screen 44 is illustrated in
The slots 62 provide gaps for fluid flow across well screen 44 from exterior region 48 to interior region 50 or from interior region 50 to exterior region 48. The gap size of slots 62 controls the size of particulars that are filtered from the flow of fluid. However, this gap size is adjusted as the compliant well screen 44 is transitioned between different deflection modes via flexing of elongate members 60 in, for example, a radially inward direction or a radially outward direction between screen ends 56 and 58.
As further illustrated in
Well system 20 also may comprise a support structure 68 positioned to limit deflection of compliant well screen 44. One example of support structure 68 is illustrated in
In the specific example illustrated, support structure 68 comprises a tubular member having a plurality of radial openings 70 to accommodate fluid flow between exterior region 48 and interior region 50. Support structure 68 further comprises standard connection ends 72 and 74 that allow support structure 68 to be coupled to tool string 46. By way of example, standard connection ends 72 and 74 may comprise threaded connection ends or flange-style connection ends. Support structure 68 also comprises a tubular midsection 76 sized to fit within compliant well screen 44 so as to limit the radially inward deflection of well screen 44.
As best illustrated in
In the embodiment illustrated, support elements 78 are mounted to tubular midsection 76 and are interchangeable to enable adjustment of the maximum deflection limitation. By way of example, each support element 78 may comprise a cap 80 of predetermined thickness. The cap 80 is mounted to tubular midsection 76 by a fastener 82, such as a threaded fastener received in a threaded opening 84 formed in tubular midsection 76 of support structure 68. Accordingly, the maximum deflection limitation can be changed by unthreading each threaded fastener 82, removing each corresponding cap 80, and reattaching the same or different threaded fasteners 82 with alternate caps 80 of a different thickness.
In some embodiments, the compliant well screen 44 can deflect in both an expanding mode and a collapsing mode to remove accumulation and prevent plugging of well screen 44. The ability to deflect well screen 44 also facilitates a variety of well operations, such as dehydration of slurry in the wellbore during, for example, a gravel packing operation. The prevention of plugging is accomplished without employing any powered control mechanism downhole. Instead, elongate members 60 of well screen 44 are flexed upon application of sufficient pressure inputs created by internal and/or external pressure differentials formed along the well screen 44. The application of pressure differentials also alters slots 62 which, in turn, changes the gap size through which fluid flows through well screen 44. Pressure differentials may be generated by, for example, flow, mechanical crushing or drag resulting from movement of the bottom hole assembly 52, mechanical radial force from a tool having a sliding sleeve, or other mechanisms or procedures for developing pressure differentials.
Until the pressure differential between exterior region 48 and interior region 50 is sufficiently great, elongate members 60 remain in an intermediate or normal mode, as illustrated schematically in
Once the predetermined differential pressure is reached as a result of fluid flow from the exterior annulus region 48 to the interior region 50 within the tool string, the elongate members or beams 60 collapse, as illustrated schematically in
The radially inward deflection mode also forces the elongate members 60 into closer proximity with each other, thereby crushing particles that are within the gaps or slots 62 between elongate members 60. Upon sufficient reduction or removal of the pressure differential across well screen 44, the well screen 44 returns to its intermediate deflection mode. Fluid flow can then be directed into interior region 50 within tool string 46 to create an outward flow of fluid through well screen 44 from interior region 50 to exterior region 48. The fluid flow can be directed to interior region 50 via flow through coiled tubing or jointed pipe of system 20, for example. This backflow can be used to create a pressure differential able to transition the well screen to a radially outward deflection mode in which elongate members 60 are bowed radially outwardly, as illustrated schematically in
The ability to flex well screen 44 between radially inward and/or outward deflection modes and to control the gap size between elongate members 60 effectively allows well screen 44 to breathe by removing plugging proppant or other materials. Furthermore, the well screen gap size can be adjusted to an optimum size during usage of well screen 44 simply by using internal and external differential pressures across well screen 44. One result is an increase in running time for well screen 44 which, in turn, facilitates the performance and efficiency of well operations by reducing the running in and out of the wellbore to change screen assemblies.
In some well applications, the deflection due to expansion is controlled by pressure drop because flow to the interior of tool string 46 can either leave through well screen 44 or through the bottom of bottom hole assembly 52. In these embodiments, flushing at a predetermined, controlled rate provides the pressure differential needed to expand well screen 44 to the radially outward deflection mode.
Well system 20 can be designed for a variety of well related operations that can benefit from the ability to use simple pressure differentials in controlling gap size for conducting flow through the well screen 44 and in preventing plugging of the well screen 44. As illustrated by the flowchart of
The utilization of compliant well screen 44 may be incorporated into a variety of well operations. For example, compliant well screen 44 can be used in a producing well or to facilitate the return of clean fluid to a surface location in a gravel packing operation. Compliant well screen 44 also can be used to facilitate a fracturing operation or a well stimulation operation. Additionally, compliant well screen 44 can be used in a clean-out operation or to facilitate the reverse circulation of fluid through a bottom hole assembly. Furthermore, the well screen 44 can be flexed to create a desired gap size and/or to remove accumulation along the well screen while the well screen is moved along wellbore 26. For example, well screen 44 can be flexed to prevent plugging and/or to adjust gap size as the well screen is run in hole, pulled out of hole, or moved between wellbore zones.
In any of these operations, well screen 44 is flexed via a created pressure differential to remove accumulation and prevent plugging and/or to adjust the gap size between elongate members 60, as indicated by block 96. During or after flexing of compliant well screen 44 to a desired deflection mode or modes, the well operation is continued without any need to pull well screen 44 from the wellbore, as represented by block 98. Accordingly, no separately powered tools are required to clean the well screen, and well screen 44 can be operated with simple pressure differentials between an exterior and an interior of the well screen.
It should be noted that well system 20 may have a variety of configurations and components for use in many types of well operations. Additionally, the diameter, length, shape and materials of well screen 44 can be adjusted to accommodate system requirements, environmental factors or other design considerations.
Accordingly, although only a few embodiments of the present invention have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this invention. Accordingly, such modifications are intended to be included within the scope of this invention as defined in the claims.
