System and methodology for facilitating gravel packing operations

A technique facilitates formation of a gravel pack in a wellbore. Gravel slurry is delivered downhole to a desired gravel packing zone located along an annulus surrounding a gravel packing completion. Dehydration of the gravel pack is facilitated by providing a return flow path for a carrier fluid along drainage layers of adjacent screen assemblies. The drainage layers of adjacent screen assemblies are coupled by drainage layer shunt tubes which bypass corresponding couplings between the adjacent screen assemblies. In some applications, the drainage layer shunt tubes facilitate delivery of the returning carrier fluid to a sliding sleeve assembly.

BACKGROUND

Gravel packs are used in wells for removing particulates from inflowing hydrocarbon fluids. In a variety of applications gravel packing is performed in long horizontal wells by pumping slurry comprising gravel suspended in a carrier fluid down the annulus between the wellbore wall and screen assemblies. The slurry is then dehydrated by returning the carrier fluid to the surface after depositing the gravel in the wellbore annulus. To return to the surface, the carrier fluid flows inwardly through the screen assemblies and into a production tubing which routes the returning carrier fluid back to the surface. In some applications, inflow control devices have been combined with the screen assemblies to provide control over the inflow of production fluids.

Sometimes the inflow control devices may be combined with alternate path type screen assemblies which utilize shunt tubes for transporting slurry. For example, the slurry may be moved through shunt tubes once bridging has occurred in the annulus surrounding the screen assemblies. The slurry flows through the shunt tubes and exits through nozzles to enable bypassing of the bridging and to enhance gravel packing of the annulus. When inflow control devices are utilized, however, the complexity of the dehydration process is increased because return flow of the carrier fluid through the inflow control devices may be insufficient to obtain reasonable pumping times for gravel packing an entire production zone.

SUMMARY

In general, a system and methodology are provided for facilitating formation of a gravel pack in a wellbore. Gravel slurry is delivered downhole to a desired gravel packing zone located along an annulus surrounding a gravel packing completion. Dehydration of the gravel pack is facilitated by providing a return flow path for a carrier fluid along drainage layers of adjacent screen assemblies. The drainage layers of adjacent screen assemblies are coupled by drainage layer shunt tubes which bypass corresponding couplings between the adjacent screen assemblies. In some embodiments, the drainage layer shunt tubes facilitate delivery of the returning carrier fluid to a sliding sleeve assembly.

DETAILED DESCRIPTION

The disclosure herein generally involves a system and methodology which facilitate formation of gravel packs in wellbores. A gravel packing system is constructed so that gravel slurry is delivered downhole to form a gravel pack in a wellbore. The gravel slurry is delivered to a desired gravel packing zone located along an annulus surrounding a gravel packing completion. Once placed in the desired gravel packing zone, the gravel pack is dehydrated through removal of a carrier fluid from the gravel used to form the gravel slurry.

Dehydration of the gravel pack is facilitated by providing a return flow path for the carrier fluid which improves the flow rate of the carrier fluid flowing from the gravel pack region to an interior of the gravel packing completion for return to the surface. As described in greater detail below, the return flow path allows the carrier fluid to flow along drainage layers of adjacent screen assemblies. The drainage layers of the adjacent screen assemblies are coupled by drainage layer shunt tubes which bypass corresponding couplings between the adjacent screen assemblies. The drainage layer shunt tubes improve the flow rate of returning carrier fluid, particularly in embodiments utilizing screen assemblies with solid base pipes combined with a flow control devices. In some embodiments, the drainage layer shunt tubes facilitate delivery of the returning carrier fluid to a sliding sleeve assembly.

The drainage layer shunt tubes and overall improved drainage system may be constructed in various embodiments for use in several different applications in which it is useful to connect drainage layers of sequential sections of a gravel packing completion. For example, one or more drainage layer shunt tubes may be employed between sequential sections of gravel packing multistage completions and/or in gravel packing completions using alternate path screen assembly sections having inflow control devices. The drainage layer shunt tubes may be used to couple sequential drainage layers without the use of specialized couplings between base pipes.

According to an embodiment, a drainage layer shunt tube is used to transport returning carrier fluid from a drainage layer of one screen assembly section to the drainage layer of another screen assembly section (and/or to another completion section). The returning carrier fluid is the fluid flowing from the gravel slurry as the gravel pack is dehydrated. The returning carrier fluid passes inwardly through filter screens of the screen assembly sections. The drainage layer shunt tube may be in the form of a single tube or a plurality of tubes extending between adjacent drainage layers. Use of drainage layer shunt tubes to connect adjacent drainage layers improves the rate of flow with respect to the returning carrier fluid and also provides for reduced complexity on the rig floor. Drainage layer shunt tubes are easily connected and provide an economical and time efficient methodology for connecting drainage layers, e.g. sequential drainage layers along a gravel packing completion.

In alternate path applications, shunt tubes and packing tubes are used for transporting and delivering gravel slurry to a desired well zones even when bridging occurs along the annulus. Some alternate path applications utilize screen assemblies with solid walled base pipes combined with inflow control devices. When using inflow control devices alone for return flow of carrier fluid, the flow rate of the returning carrier fluid may be undesirably low. The drainage layer shunt tubes, however, may be connected to the drainage layers of adjoining screen assemblies to improve the flow rate. In some embodiments, a drainage layer shunt tube also may be connected to an opening/port in a sliding sleeve assembly to facilitate rapid flow of the returning carrier fluid into an interior of the gravel packing completion for return to a surface collection location.

Referring generally toFIG. 1, an example of a well system20deployed in a wellbore22is illustrated. In this example, well system20comprises a gravel packing completion24deployed downhole into wellbore22on a tubing string26. The gravel packing completion24is deployed to a desired gravel packing zone28to facilitate formation of a gravel pack. By way of example, the gravel packing completion24may be a multistage completion and/or an alternate path completion. In the embodiment illustrated, the gravel packing completion24comprises a plurality of screen assembly sections30, i.e. screen assemblies, coupled together sequentially on a rig floor32and deployed downhole into wellbore22to the gravel packing zone28. The deployment of tubing string26downhole may be facilitated via a rig34.

Referring generally toFIG. 2, a portion of an embodiment of gravel packing completion24is illustrated. In this embodiment, sequential screen assembly sections30of a desired number of screen assembly sections30are coupled together and disposed at gravel packing zone28to enable formation of a gravel pack36. The gravel pack36may be formed in an annulus38generally between a surrounding wellbore wall40and the gravel packing completion24.

In the embodiment illustrated inFIG. 2, each screen assembly section30comprises a base pipe42within a filter screen44disposed at least partially about an exterior of the corresponding base pipe42. In a variety of applications, the filter screen44may be cylindrical in shape and may encircle the entire corresponding base pipe42. As illustrated, each filter screen44is positioned with respect to its corresponding base pipe42to create a drainage layer46located therebetween. In some applications, each base pipe42may be a solid walled base pipe combined with an inflow control device48. Each inflow control device48comprises at least one flow port50, e.g. nozzle, through which fluid may flow from an exterior of the base pipe42to an interior52. The interior52provides a flow passage extending through each base pipe42and through the interior of the overall gravel packing completion24.

Adjacent screen assembly sections30are joined by couplings54. For example, each coupling54may be used to connect sequential, adjacent base pipes42. Additionally, a drainage layer shunt tube system56may be used to connect drainage layers46of at least some of the adjacent screen assembly sections30. By way of example, the drainage layer shunt tube system56may comprise drainage layer shunt tubes58with at least one tube58coupled between selected pairs of adjacent screen assembly sections30. Each shunt tube58may be arranged to extend from a drainage layer46of one screen assembly section30to the drainage layer46of the next adjacent screen assembly section30independently of coupling54. In some embodiments, the shunt tube58is disposed externally of the corresponding coupling54and extends past the corresponding coupling54at a position radially outward of the coupling54. One or more shunt tubes58may be used to bypass each corresponding coupling54between adjacent screen assembly sections30, as illustrated.

With additional reference toFIG. 3, a specific embodiment of drainage layer shunt tube58is illustrated. In this example, the drainage layer shunt tube58is routed along a path radially outward of the corresponding coupling54, e.g. spaced from coupling54, to provide a flow path between drainage layers46independently of the coupling54connecting adjacent screen assembly sections30. In this example, the filter screen44of each screen assembly section30is coupled to the corresponding base pipe42via end rings60(see alsoFIG. 2). The end rings60may be coupled with the corresponding base pipe42via a variety of fastening techniques, including welding, separate fasteners, threaded engagement, or other suitable devices.

In this example, each drainage layer shunt tube58is connected between sequential drainage layers46via engagement with end rings60of adjacent screen assembly sections30, as illustrated inFIG. 3. By way of example, each end ring60may comprise a port62to which an and of the drainage layer shunt tube58is communicatively coupled for fluid flow. The drainage layer shunt tube58may comprise a pair of elbow sections64coupled to corresponding end rings60at ports62via suitable fasteners, such as clamping fasteners, threaded engagement, welding, or other suitable devices. The elbow sections64are coupled with a straight shunt tube section66via shunt tube connectors68. By way of example, the shunt tube connectors68may be in the form of cylindrical connectors having suitable seals, e.g. O-ring seals, for receiving the corresponding ends of straight section66and elbow sections64.

The shunt tube system56and the individual shunt tubes58provide a useful, inexpensive structure for connecting drainage layers46to enable flow communication of, for example, returning carrier fluid to enhance dehydration of the gravel pack. The drainage layer shunt tube (or tubes)58extending between each pair of adjacent screen assembly sections30provide a system which is readily assembled while on rig floor32and as the gravel packing completion24is assembled and deployed downhole into wellbore22.

The drainage layer shunt tubes58are particularly useful in gravel packing completions24which utilize alternate path technology. The drainage layer shunt tubes58are readily combined with alternate path type screen assembly sections30. InFIGS. 2 and 3, the alternate path tubes, e.g. packing tubes and slurry shunt tubes for bypassing bridging, are not shown so the dehydration layer shunt tubes58can be more easily illustrated and explained. However,FIG. 4illustrates an alternate path type system combined with the drainage layer shunt tube system56.

Referring again toFIG. 4, a cross-sectional view of one of the screen assembly sections30is illustrated. In this embodiment, the gravel packing completion24and the individual screen assembly sections30comprise an alternate path system70. The alternate path system70facilitates delivery of slurry past bridging and to desired regions in gravel packing zone28so as to ensure a thorough and complete gravel pack36. Although the alternate path system70may utilize a variety of tubes in various arrangements, an embodiment utilizes a plurality of slurry shunt tubes72for delivering slurry along the screen assembly sections30and a plurality of packing tubes74for delivering slurry to desired regions in gravel packing zone28.

The slurry shunt tubes72and packing tubes74may be mounted to the screen assembly sections30via a variety of mounting structures76. One embodiment of such a mounting structure76is a plurality of shunt rings78mounted along the exterior of the gravel packing completion24. By way of example, the shunt rings78may be mounted around filter screens44, end rings60, couplings54, and/or at other suitable locations along the gravel packing completion24to provide support for the slurry shunt tubes72and packing tubes74.

Depending on the application and environment, the various features of drainage layer shunt tube system56and overall gravel packing completion24may be changed or modified. For example, the drainage layer shunt tubes58may be slotted or otherwise perforated to keep out sand while facilitating dehydration of the gravel pack36in regions where there are no filter screens44. The drainage layer shunt tubes58also may incorporate other types of filters to facilitate dehydration in regions between filter screens44while also providing a flow path into tubes58between sequential drainage layers46.

Additionally, the size and shape of the drainage layer shunt tubes58may be selected according to the parameters of a given operation. For example, the drainage layer shunt tubes58may have cross-sections which are round, square, rectangular, or another suitable shape. Additionally, the flow area as well as the wall thickness may be selected according to the parameters of a specific application or applications. The shape of elbow sections64also may vary. For example, the elbow sections64may be formed with 90° angles, 45° angles, or with other suitable angles to appropriately position straight tube section66.

Referring generally toFIGS. 5 and 6, another embodiment of gravel packing completion24is illustrated. In this embodiment, sequential screen assembly sections30have drainage layers46connected by drainage layer shunt tubes58of drainage layer shunt tube system56as described above. However, at least one of the drainage layers46is placed in communication with a sliding sleeve assembly80via at least one drainage layer shunt tube58. In this embodiment, the gravel packing completion24comprises the sliding sleeve assembly80which may be coupled to an adjacent screen assembly section30via one of the couplings54. For example, the coupling54may be used to couple base pipe42of the adjacent screen assembly section30with a corresponding housing82of the sliding sleeve assembly80.

As illustrated inFIG. 6, housing82comprises an opening84which may be in the form of a port or ports placed in fluid communication with the corresponding drainage layer shunt tube58. In the example illustrated, the end of the drainage layer shunt tube58proximate sliding sleeve assembly80is coupled with an outer housing86sealably engaged with housing82and surrounding opening, e.g. port(s),84. This arrangement provides a fluid communication passageway from the sequential drainage layers46to the opening84so as to route returning carrier fluid from the drainage layers46into an interior of housing82which is part of the overall interior52. The returning carrier fluid may then be routed to the surface or to another desired collection location.

The sliding sleeve assembly80further comprises a closure system86which may be selectively actuated to open or close opening84with respect to fluid flow through opening84. By way of example, closure system86may comprise a sliding sleeve88slidably mounted within housing82. As illustrated, the sliding sleeve88may be sealed with respect to an interior surface of housing82via a plurality of seals90. The closure system86, e.g. sliding sleeve88, is selectively shiftable to an open port position, as illustrated, which allows carrier fluid resulting from dehydrating of the gravel slurry to flow into the interior52of the gravel packing completion24.

Upon completion of the gravel packing operation, the closure system86, e.g. sliding sleeve88, may be shifted past opening84to a closed port position which blocks further flow through opening84. The opening84may be closed off during, for example, production operations in which well fluid flows into interior52via inflow control devices48for production to a surface collection location.

The closure system86may be actuated via a variety of mechanisms. If sliding sleeve88is utilized, for example, a shifting tool may be run downhole through the interior of gravel packing completion24to engage and shift the sliding sleeve88between the open port and closed port positions. The shifting tool may be run on a work string, wireline, coiled tubing, drill pipe, or other suitable conveyance. In some applications, however, a downhole actuator92may be coupled with sliding sleeve88to shift the sliding sleeve between the open port and closed port positions. By way of example, the downhole actuator92may be an electromechanical actuator or a hydraulic actuator coupled to a surface control by, for example, communication lines94. However, downhole actuator92also may be constructed to enable wireless control.

In some applications, returning carrier fluid is filtered prior to entry into interior52through opening84. By way of example, a filter96may be located upstream of opening84to filter the inflowing carrier fluid. In the specific example illustrated, the filter96is located within outer housing86and externally of housing82proximate opening/ports84.

Depending on the operation, the sliding sleeve assembly80may be coupled into gravel packing completion24at a variety of selected locations. For example, the sliding sleeve assembly may be connected to accept flow of returning carrier fluid from a downhole location or from both downhole and uphole locations. The sliding sleeve assembly80also may be utilized with alternate path systems comprising, for example, slurry shunt tubes72and packing tubes74.

Many types of materials, components, and component configurations may be used in constructing the gravel packing system described herein. For example, the filter screens may be made from a variety of woven and nonwoven materials in various patterns and arrangements. Similarly, the drainage layer shunt tubes may be made in various shapes, sizes and configurations. Additionally, the drainage layer shunt tubes may be made from solid walled tubes or from tubes having porous sections comprising meshes, screens, porous materials, and/or other suitable materials. The gravel packing system also may comprise different numbers of drainage layer shunt tubes, base pipes, filter screens, couplings, slurry shunt tubes, packing tubes, and/or other components and features to facilitate gravel packing of a desired well zone or zones.