Patent Publication Number: US-9428997-B2

Title: Multi-zone bypass packer assembly for gravel packing boreholes

Description:
BACKGROUND OF THE DISCLOSURE 
     In the field of oil and gas exploration and production, it is common for sand and other fine solid particles to be present in reservoir fluids. These particles are highly abrasive and cause damage to the well components. Therefore, in many formations, it is necessary for the wellbore completion to control the sand and other fine particles that enter the production tubing and are brought to surface with the production fluid. A wide range of sand control technologies are used in the industry, and typically comprise a system of sand control devices (such as sand screens) displaced along the completion string that filter sands and fine particles from the reservoir fluids. In the end, the sand control devices prevent the particulate from entering the production tubing. 
     Sand control devices are typically used in conjunction with one or more gravel packs, which comprise gravel or other particulate matter placed around the sand control device to improve filtration and to provide additional support to the formation. In a gravel pack operation, for example, a slurry of gravel solids in a carrier fluid is pumped from surface along the annulus between the sand control device and the open or cased hole. The gravel then preferably packs with a good distribution in the annulus at the sand control device. 
     In many subterranean formations, a wellbore may pass through multiple hydrocarbon bearing zones that are of interest to the operator so that it may be necessary to gravel pack the individual zones. An example of a multi-zone completion system is shown in  FIG. 1 . The system  100  includes a production facility at surface, which in this case is a floating production storage and offloading (FPSO) vessel  102 , coupled to a wellbore  104  via a subsea tree  106 . The wellbore  104  in this case is a deviated wellbore that extends through multiple production zones or intervals  107   a - c  in the formation  108 . The production tubing  110  provides a continuous flow path that penetrates through the multiple zones  107   a - c.    
     The production tubing  110  can be provided with ports or inflow control devices (not shown) that allow production fluid to flow into the production tubing  110  and uphole to the subsea tree  106 . To provide control over the production process, the annulus  112  is sealed by packers  114  between the different production zones  107  to prevent fluid flowing in the annulus between the different zones. Sand control devices  116  prevent solid particles of the gravel pack and the formation from entering the production tubing  110 . 
     In a conventional approach to sand control, a gravel pack is installed across the first isolated zone  107   c  by running gravel pack tools in a dedicated gravel pack operation. Subsequently, in a separate gravel pack operation, a gravel pack is installed across an adjacent isolated zone  107   b . The procedure can be performed multiple times to place gravel packs across all of the zones of interest. 
     In some formations where adjacent zones are particularly close together, it may not be possible to perform separate gravel pack operations in this manner. Moreover, even where it is possible to perform separate gravel pack operations, it is generally desirable to install gravel packs across all of the zones of interest in a single trip when multiple production zones are in close proximity to one another. Tool systems and methods for achieving this are referred to as single trip multi-zone systems. In these methods, the gravel pack slurry is pumped with the gravel pack tools positioned across each of the intended zones, and the gravel is placed across multiple zones in a single trip, but with distinct and separate pumping operations for each zone. 
     These single trip multi-zone systems reduce the overall time of the gravel pack operation significantly, but they do suffer from some major disadvantages. For example, the operations are complicated and require a lot of specialized equipment to be installed into the wellbore. Service tools must be repositioned for gravel packing each zone, and pumping must be stopped upon the completion of one zone and then restarted when the tools have been positioned at the next zone. 
     To improve the delivery of gravel slurries, sand control devices have been provided with shunt tubes, which create alternate flow paths for the gravel and its carrier fluid. These alternate flow paths significantly improve the distribution of gravel in the production interval, for example, by allowing the carrier fluid and gravel to be delivered through sand bridges that may form in the annulus before the gravel pack has been completed. Examples of shunt tube arrangements can be found in U.S. Pat. Nos. 4,945,991 and 5,113,935. The shunt tubes may also be internal to the filter media, as described in U.S. Pat. Nos. 5,515,915 and 6,227,303. 
     U.S. Pat. No. 6,298,916 describes a multi-zone packer system that has an arrangement of cup packers with shunt tubes used in a gravel pack operation. An upper packer is bypassed by a crossover device to deliver the gravel pack slurry to a first production zone, and the shunt tubes allow the slurry to be placed at the subsequent zones beneath the zonal isolation packers. U.S. Pat. No. 7,562,709 describes an alternative method in which the zonal isolation is achieved by the use of swellable packers, which include a mantle of swellable elastomeric material formed around a tubular body. Shunt tubes run underneath the swellable mantle to allow the gravel pack slurry to bypass the isolation packers. 
     It is also proposed in WO 2007/092082 and WO 2007/092083 to provide packers with alternate path mechanisms that may be used to provide zonal isolation between gravel packs in a wellbore. Embodiments described in WO 2007/092082 and WO 2007/092083 include packers with swellable mantles that increase in volume on exposure to a triggering fluid. US 2010/0155064 and US52010/0236779 also disclose the use of swellable isolation devices in shunt tube gravel packing operations. US52011/0203793 is yet another example that uses cup packers and swellable isolation devices. 
     Although the shunt tube systems allow zonal isolation in gravel pack operations, the reliance on shunt tubes as a bypass mechanism for gravel slurry placement is undesirable. Reliance on shunt tubes adds to the general complexity of the completion and installation operation. For example, the shunt tubes must be aligned and made up to jumper tubes of adjacent sand control devices when the production tubing is assembled. The use of shunt tubes may also cause complications for maintaining the required annular barrier or fluid seal functions of the isolation packers, as they are required to expand around shunt tubes. 
     In swellable elastomer systems, problems may arise due to removal of a volume of elastomer from the isolation device, improper sealing around the shunt tubes, displacement of the conduits due to expansion of the element, and/or coupling of the conduits at opposing ends of the isolation device. Accommodation of shunt tubes may necessitate a reduction in the overall volume of the expanding element, and in particular a reduction in the volume of the expanding element which is radially outward of the shunt tube. A shunt tube system with swellable isolation may therefore take longer than desirable to achieve a seal and/or may not have sufficient pressure sealing performance. Mitigating these problems may require the run-in diameter of the swellable packer to be increased, which can impact on the success of deployment operations, or reduction in the effective production bore size, which is detrimental to production rates. 
     While the use of swellable elastomer packers and isolation devices have several advantages over conventional packers including passive actuation, simplicity of construction, and robustness in long term isolation applications, their use in conventional gravel pack applications described above may increase the time taken to perform the entire gravel pack operation. This is because in a conventional approach, the isolation devices are set against the wall of the open or cased hole to isolate the zones prior to placement of the gravel pack. This sequence means that the gravel pack cannot be placed until the swellable isolation device has swollen, which in many cases may be a number of days. This introduces a delay before pumping of the gravel slurry which may be undesirable to the operator. 
     Particular implementations for mitigating at least some of the above issues are disclosed in US2013/0161000, filed 23 Dec. 2011 by John Broussard, Brian Nutley, Ross Clarke, and Kim Nutley, and entitled “Downhole Isolation Methods and Apparatus Therefor,” which is incorporated herein by reference in its entirety. Although these implementations are effective, operators are continually striving for versatile techniques for gravel packing and isolating multiple sections of a borehole. 
     The subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above. 
     SUMMARY OF THE DISCLOSURE 
     A two element packer apparatus uses one packer to serve as a barrier to annular flow during a gravel pack operation. This barrier packer is placed between upper and lower zones in a borehole. In one embodiment, a bypass flow area internal to the packer apparatus connects to one or more transport tubes attached to the screens across the upper zone. Gravel packing the upper zone can then take place in a normal fashion with the slurry dehydrating through the upper screen section. Once the upper screen section is covered, the slurry diverts into the transport tubes and flows through the bypass of the packer apparatus, entering the annulus around the lower screen section for the lower zone to be gravel packed. The slurry is pumped until an increase in pressure indicates that the lower screen section is covered with slurry. At this point, a second packer on the apparatus expands and seal against the borehole wall or casing in a void space below the first packer. 
     The packer apparatus can be used for cased and open hole applications. For cased holes, the upper packer can be a cup packer to form a friction seal with the surrounding casing wall. Thus, the cup packer can act as a barrier at least to the gravel from the slurry during gravel packing of the upper zone. The packer apparatus can be adapted for open hole applications by making the upper packer hydraulically or hydrostatically-actuated with a compressible packing element that expands enough to seal on the irregularities of an open hole. This arrangement could also be used in a cased hole. 
     The second packer can be a swellable packer, a mechanically-actuated packer, a hydraulically-actuated packer, or a hydrostatically-actuated packer. However, either one or both of these first and second packers can be actuated through the use of radio-frequency identification (RFID) tags or pressure pulse signals. Preferably, the second packer has a compressible packing element and is independently compressible to isolate fluid passage between the uphole and downhole annulus portions. 
     In another embodiment, gravel packing an annulus of a borehole with gravel communicated in a slurry starts with sealing a section of a washpipe in an internal passage of an assembly disposed in a borehole. Slurry is communicated down the annulus around the assembly disposed in the borehole, and passage of at least the gravel is restricted with a first packer element from an uphole portion of the annulus to a downhole portion of the annulus. However, the slurry can communicate from the uphole annulus portion to the downhole annulus portion through an internal bypass on the assembly. 
     The gravel from the slurry packs around a downhole screen section on the assembly in the downhole annulus portion, and the internal passages of the washpipe takes the fluid returns from the slurry. Eventually, a port on the washpipe is opened uphole of the washpipe&#39;s sealed section in the first internal passage of the assembly. At this point, the gravel from the slurry packs around an uphole screen section on the assembly in the uphole annulus portion. The fluid returns from the slurry are taken in through the washpipe&#39;s open port and up the internal passage of the washpipe. In the end, fluid communication can be isolated between the uphole and downhole annulus portions by activating a second packer element disposed on the assembly between the uphole and downhole screen sections. 
     The foregoing summary is not intended to summarize each potential embodiment or every aspect of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic sectional view of a multi-zone production system according to the prior art. 
         FIG. 2  illustrates a schematic view of a gravel pack assembly according to one embodiment of the present disclosure. 
         FIGS. 3A-3D  illustrate portions of the gravel pack assembly in  FIG. 2  during stages of a gravel pack operation. 
         FIG. 4A  illustrates an embodiment of a concentric bypass packer apparatus having a transport tube; a concentric bypass; a cup packer; and a mechanically-actuated, compression-set packer for the disclosed gravel pack assembly. 
         FIG. 4B  illustrates an embodiment of a concentric bypass packer apparatus having a transport tube; a concentric bypass; a cup packer; and a hydraulically-actuated, compression-set packer for the disclosed gravel pack assembly. 
         FIG. 4C  illustrates an embodiment of a concentric bypass packer apparatus having a transport tube, a concentric bypass, a cup packer, and a swellable packer for the disclosed gravel pack assembly. 
         FIG. 5  illustrates a schematic view of a gravel pack assembly according to another embodiment of the present disclosure. 
         FIGS. 6A-6B  illustrate portions of the gravel pack assembly in  FIG. 5  during stages of a gravel pack operation. 
         FIG. 7A  illustrates an embodiment of a concentric bypass packer apparatus having a concentric bypass; a cup packer; and a mechanically-actuated, compression-set packer for the disclosed gravel pack assembly. 
         FIG. 7B  illustrates an embodiment of a concentric bypass packer apparatus having a concentric bypass; a cup packer; and a hydraulically-actuated, compression-set packer for the disclosed gravel pack assembly. 
         FIG. 7C  illustrates an embodiment of a concentric bypass packer apparatus having a concentric bypass, a cup packer, and a swellable packer for the disclosed gravel pack assembly. 
         FIGS. 8A-8B  illustrate an isolation tool for the washpipe of the gravel pack assembly in  FIGS. 5 and 6A-6B  in closed and opened conditions. 
         FIG. 8C  illustrates the isolation tool disposed in a concentric bypass packer apparatus of the present disclosure. 
         FIG. 9A  illustrates an embodiment of a concentric bypass packer apparatus having a transport tube; a concentric bypass; a cup packer; a hydraulically-actuated, compression-set packer; and an electronic control unit for the disclosed gravel pack assembly. 
         FIG. 9B  schematically illustrates details of an electronic control unit for the disclosed packer apparatus. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     Turning to  FIGS. 2 and 3A-3D , a gravel pack assembly  200  according to the present disclosure is disposed in a borehole  10 . In general, the borehole  10  can be an open hole as in  FIG. 2 , or it can be a cased hole as in  FIGS. 3A-3D  having perforations  18 U-D at zones of interest. Although shown as vertical, the borehole  10  can be deviated, depending on the implementation. 
     As shown in  FIG. 2 , the assembly  200  extends downhole from a packer  14  and has a tubular body  220 , conduit, liner, or the like, which can comprise one or more components interconnected together. The tubular body  220  and borehole  10  define an annulus  16  about the body  220 , and the body  220  defines an internal passage  222  for passage of production fluid, tools, and the like. 
     Along its length, the body  220  has at least two screen sections  240 U-D disposed next to zones of interest in the formation. For a cased hole as in  FIGS. 3A-3D , perforations  18 U-D in the casing  12  may be provided to communicate the borehole  10  with the zone of interest. Either way, each screen section  240 U-D can have one or more screens, which can be any suitable type of screen for gravel pack operations. 
     During operations, the assembly  200  is disposed in the borehole  10  using known techniques so that the tubular body  220  can eventually be used for production from the various zones. To control sand and other fines, gravel packing operations are performed in the annulus  16  around the tubular body  220  of the assembly  200 . To do this, operators install a workstring  110  into the assembly  200  and begin pumping slurry down the annulus  16  around the assembly  200  to gravel pack around the screen sections  240 U-D. 
     As shown in  FIG. 2 , the work string  110  installs in the packer  14 , and a washpipe  214  on the work string  110  extends into the assembly  200  through the screen sections  240 U-D. At the packer  14 , a cross-over tool  210  diverts a slurry of gravel and carrier fluid conveyed down the workstring  110  out the cross-over&#39;s outlet ports  212  and into the annulus  16  around the assembly  200 . Meanwhile, fluid returns from the slurry entering the screen sections  240 U-D can flow up the washpipe  214  and can pass through the cross-over tool  210  and into the annulus  15  uphole of the packer  14  toward the surface. 
     The uphole screen section  240 U disposed on the body  220  toward an uphole end communicates the uphole annulus  16 U of the borehole  10  with the body&#39;s interior passage  222 . In a similar fashion, the downhole screen section  240 D disposed on the body  220  toward a downhole end communicates the downhole annulus  16 D of the borehole  10  with the interior passage  222 . Any suitable type of screens can be used for the screen section  240 U-D and can include wire-wrapped screens, pre-packed screens, direct-wrapped screens, meshes, etc. 
     Disposed between these two screen sections  240 U-D is a concentric bypass packer apparatus  250  according to the present disclosure. In general, any number of screen sections  240  separated by concentric bypass packer apparatus  250  can be disposed along the length of the assembly&#39;s body  220 . Finally, an isolation packer  235  can be disposed at the downhole end of the assembly  200 . 
     The concentric bypass packer apparatus  250  includes at least two packers  270  and  275  and a concentric bypass  256 . One or more transport tubes  260  extend from the concentric bypass  256  along the upper screen section  240 U in the upper annulus  16 U. As will be discussed below, the transport tube  260  and concentric bypass  256  selectively communicate the uphole annulus  16 U with the downhole annulus  16 D during stages of a gravel pack operation. 
     As shown, the at least two packers  270  and  275  on the concentric bypass packer apparatus  250  include a first uphole packer  270  and a second downhole packer  275 . The uphole packer  270  restricts passage of at least gravel (and not necessarily fluid) from the uphole annulus  16 U to the downhole annulus  16 D, although the uphole packer  270  could be used to achieve at least some fluid isolation of the annulus  16 . This uphole packer  270  can be a passive type of packer, such as a cup packer, that freely engages the sidewall of the borehole  10  or casing  12 . 
     By contrast, the downhole packer  275  is independently-actuated to engage the sidewall of the borehole  10  or casing  12  and to form a fluid isolation seal between zones. As such, the downhole packer  275  is an active type of packer that deploys unexpanded into the borehole  10  and is later activated to engage the borehole or casing wall as detailed below. Once activated, the downhole packer  275  isolates fluid passage between the uphole and downhole annuli  16 U-D to isolate the two zones. 
     This second packer  275  can have a swellable packer element. In some applications, however, a swellable packer element may not be the best choice because the time required to achieve sufficient swelling can be hard to manage. In particular, the swelling needs to be timed to ensure that enough space remains in the annulus around the swellable packer element when pumping gravel pack slurry downhole before the element actually swells and creates a seal with the borehole or casing wall. 
     For this reason, the second packer  275  is preferably independently compressible and can use a compression-set packing element that is mechanically, hydrostatically, hydraulically, and/or electronically activated. The compressive force used to activate the downhole packer  275  can be delivered through hydrostatic pressure, hydraulic (applied) pressure, or mechanical action. As the compressive force is delivered to the downhole packer  275 , its compressible element is compressed in length and expands radially until contacting the wellbore  10  or casing  12  to create a seal between the packer apparatus  250  and the wellbore  10  or casing  12 . 
     As noted above, the concentric bypass packer apparatus  250  also includes the bypass  256  between the two annuli  16 U-D. As shown, an uphole end of the concentric bypass  256  communicates with at least one transport tube  260 , and a downhole end of the concentric bypass  256  communicates with the downhole annulus  16 D. As noted above, the transport tubes  260  are used as shunt tubes and are not attached to packing tubes carrying gravel. Thus, multiple stages can be set up with each lower stage having transport tubes  260  open at the distal ends with the intent of taking diverted slurry and delivering it to the next lower zone as that upper zone is filled. Finally, the screen section  240 D below the packer apparatus  250  may or may not be equipped with transport tubes (not shown). 
     Turning to more details of the assembly  200 ,  FIGS. 3A-3D  illustrate portions of the gravel pack assembly  200  in  FIG. 2  during stages of a gravel pack operation. As shown in  FIG. 3A  at the start of the gravel pack operation, the downhole packer  275  is run downhole in an unactivated state. Meanwhile, the uphole packer  270 , such as a cup packer, is adapted to passively engage the surrounding borehole  10  or casing  12  to at least partially seal the uphole annulus  16 U from the downhole annulus  16 D. 
     Gravel packing can then be started by communicating slurry having carrier fluid and gravel down the uphole annulus  16 U using conventional techniques, such as the cross-over tool discussed above. As shown in  FIG. 3B , gravel packing begins as the slurry of gravel and carrier fluid passes out of the cross-over tool ( 210 :  FIG. 2 ) and into the uphole annulus  16 U. Gravel from the slurry begins to pack around the upper screen section  240 U, being checked from passing to the downhole annulus  16 D by the uphole packer  270 . The carrier fluid in the slurry enters the uphole screen section  240 U, and the remaining gravel deposits in the annulus  16 U around the upper screen section  240 U. Once the carrier fluid enters the assembly&#39;s body  220 , the fluid is circulated up the washpipe  214  disposed in the interior passage  222  of the assembly  200 . 
     Once the upper screen section  240 U is covered with gravel as shown in  FIG. 3C , the slurry in the uphole annulus  16 U diverts into the one or more transport tubes  260 . At this point, the slurry flows through the tubes  260  to the concentric bypass  256  inside the packer apparatus  250 . Leaving the concentric bypass  256 , the slurry then begins to pack gravel around the downhole screen section  240 D. Returns of the carrier fluid passing through the downhole screen section  240 D also pass up the washpipe  214 . 
     During gravel packing, a pressure drop can be created through the concentric bypass  256 . The resulting back pressure on the upper annulus  16 U could result in fluid loss to the formation (i.e., through perforations  18 U), which can end the pumping operation prior to placing sufficient gravel in downhole annulus  16 D and across perforations  18 D. By installing the one or more transport tubes  260  along the upper screen section  240 U and across the upper perforations  18 U, however, the slurry can have a direct route to the lower annulus  16 D. In this way, gravel packing the downhole annulus  16 D is not dependent on keeping the upper annulus  16 U open for flow. 
     As shown, the one or more transport tubes  260  preferably do not include nozzles for distributing the slurry in the uphole annulus  16 U and preferably do not connect to a shunt tube or the like. Instead, the distal ends of the one or more transport tubes  260  are disposed freely inside the uphole annulus  16 U. In fact, the distal ends may preferably extend to a point uphole of the uphole screen section  240 U to receive slurry during the gravel pack process after the uphole screen section  240 U is packed. The orifices at the distal ends of the tubes  260  can be modified to facilitate entry of the slurry if necessary. 
     Additionally, instead of passing the transport tubes  260  through the element of the uphole packer  270 , the packer apparatus  250  preferably has the uphole packer  270  disposed about an outer housing, body, mandrel, or the like disposed concentrically about an inner housing, body, mandrel, or the like of the packer apparatus  250 . One or more outlets of such an outer mandrel can communicate with the downhole annulus  16 D. Thus, once the downhole packer  275  is activated as detailed below, the downhole packer  275  closes off communication of the transport tubes  260  and concentric bypass  256 . 
     As finally shown in  FIG. 3D , slurry flow is stopped once the downhole screen section  240 D is covered with gravel. The annulus  16 D immediately below the bypass packer apparatus  250  will be free of gravel, which has tended to gravitate and pack around the downhole screen section  240 D. In particular, as the circulation of slurry stops, a section of the wellbore between the uphole packer  270  and the lower well screen section  240 D will be free of gravel. It is in this area that the downhole packer  275  of the bypass packer apparatus  250  can then be expanded to seal inside the borehole  10  or casing  12  and isolate the two zones. Sealing of the downhole packer  275  closes off any fluid communication between the uphole annulus  16 U and the downhole annulus  16 D via the concentric bypass  256  and transport tubes  260 . 
     As noted previously, the second downhole packer  275  can include different types of packer elements. For example, this downhole packer  275  may be a swellable packer. For those instances where a swelling elastomer is not a good choice, the packing element of the downhole packer  275  as noted previously can be a compressible packing element that is actuated mechanically, hydrostatically (with hydrostatic pressure), and/or hydraulically (with applied pressure). In other alternatives, the downhole packer  275  can be electronically actuated by using electronic receivers to start a motor, operate a pump, open a valve, or cause a delivery of force to set a compressible packing element once a signal is sent to the receiver. These alternatives will be discussed herein below. 
     In one embodiment shown in  FIG. 4A , the concentric packer apparatus  250  has one or more transport tubes  260 ; a concentric bypass  256 ; an upper packer  270  having a cup packer  272 ; and a downhole packer  275  having a mechanically-actuated, compression packer  280 . As before, the packer apparatus  250  allows for gravel packing multiple zones in a single pumping operation. The uphole packer  270  serves as a foundation supporting the gravel pack for the upper annulus. Thus, the uphole packer  270  serves as a base on which gravel pack sand can settle once circulation through the concentric bypass  256  stops due to a downhole screen ( 240 D) below the cup packer  272  becoming covered with gravel pack sand. Although the uphole packer  270  is shown as a cup packer  272 , the uphole packer  270  can be a mechanically-actuated packer, a hydraulically-actuated packer, or other type of packer actuated by other means to stop at least the flow of gravel in the annulus outside the apparatus  250  and to force slurry through the bypass  256  of the packer apparatus  250 . 
     Here, the mechanically-actuated, compression-set packer  280  has a compressible packing element  282  disposed between end-rings  284  and  286 . When activated mechanically, the downhole packer  280  serves to isolate the upper annulus ( 16 U) from the downhole annulus ( 16 D) after the gravel packing operation so the packer  280  can stop the flow of fluids and gravel in the annulus outside the packer apparatus  250  to isolate the wellbore&#39;s zones. As before, the packing element  282  can remain unset (unexpanded) until after the gravel pack is performed. 
     Looking at the bypass packer apparatus  250  in detail, a housing or mandrel  252  of the packer apparatus  250  defines an internal bore  254  therethrough. An uphole end of the mandrel  252  has a manifold  262  disposed thereon, which couples in a conventional manner to the upper zone screen section ( 240 U). A downhole end of the mandrel  252  couples in a conventional manner to the lower zone screen section ( 240 D). The concentric bypass  256  is configured through the mandrel  252  to bypass the uphole packer  270  and to convey slurry from the transport tubes  260  above the uphole packer  270  to an outside space below the uphole packer  270 . 
     In particular, the transport tubes  260  on the upper zone screen section ( 240 U) extend to the manifold  262  on the top of the packer&#39;s mandrel  252 . The connection of the manifold  262  on the packer&#39;s mandrel  252  can allow the manifold  262  and associated transport tube  260  to be swiveled around the central mandrel  252 , allowing for easier attachment to the transport tubes  260  on well screens and other components during assembly. This can eliminate the need for costly connections, e.g., timed threads, to make up the disclosed packer apparatus  250  to a screen joint and have the transport connections aligned. 
     The manifold  262  defines an annular space  264  around the end of the mandrel  262 , which is closed off by a cap ring  266 . One or more upper ports  258   a  in the mandrel  252  communicate the bypass  256  with the manifold&#39;s space  264 . Downhole of the cup packer  270 , the mandrel  252  defines one or more downhole ports  258   b  for communicating the bypass  256  outside the mandrel  252 . 
     Although not specifically shown in detail, it will be appreciated that the mandrel or housing  252  of the packer apparatus  250  can be comprised of multiple components, such as inner and outer mandrels with the concentric bypass  256  formed between them. Thus, as represented in  FIG. 4A , the packer apparatus  250  preferably has the uphole packer  270  disposed about an outer mandrel  253 , which is disposed concentrically about an inner mandrel  251  of the apparatus  250 . In this way, the outer mandrel  253  can form the internal concentric bypass  256  with the inner mandrel  251 . Additionally, the inner mandrel  251  can have the internal bore  254 , and the outer mandrel  256  can have the uphole and downhole external ports  258   a - b . These and other details will be evident to one skilled in the art having the benefit of the present disclosure. 
     During operations as disclosed herein after then upper screen section  240 U is packed, slurry travels through the transport tubes  260  and into the manifold&#39;s space  264 . Passing through the upper ports  258   a , the slurry enters the concentric bypass  256  and bypasses the cup packer  270 . The slurry then exits the concentric bypass  256  below the cup packer  270  through the lower ports  258   b  defined above the compression-set packer  280 . The slurry flows around the compression-set packer  280  and into the annulus ( 16 D) around the lower screen section  240 D when gravel packing is completed. 
     As noted previously, the downhole packer  275  in the present example is the mechanically-actuated, compression-set packer  280 , which stops the flow of fluids in the annulus. The packer  280  has a compressible packing element  282  disposed between end rings  284  and  286 . An inner sleeve  288  disposed in the packer&#39;s bore  254  can be mechanically shifted using a shifting tool, wireline, coil tubing, or other appropriate technique to compress the compressible element  282  between the end rings  284  and  286 . 
     In one embodiment, for example, the compressible packing element  282  is expanded by using a shifting tool (not shown) made up on a string of pipe (i.e., washpipe  214 ) run inside the screen sections  240 U-D as part of the gravel pack assembly. The shifting tool engages the inner mandrel  288  of the downhole packer  280  using keys, collet, or the like and force is delivered though this mandrel  288  into the packer element  288 , causing the radial expansion. Alternatively, the compressible element&#39;s setting force can be delivered on a separate trip in the well for the purpose of expanding the element  288  using a pipe, a wireline, or a shifting tool made up on pipe stung though the gravel pack assembly. These and other procedures can be used to set the downhole packer  280  during gravel pack operations. 
     Regardless of how the sleeve  288  is mechanically moved, the sleeve  288  can connected by transmission rods, lugs, or the like (not shown) to external components of one of the end rings  284  and  286  to compress the packing element  282 . Lock rings and the like (not shown) can be used to lock the inner sleeve  288  in an upper position once shifted so as to maintain the packing element compressed. 
     As noted herein, transport of the slurry from the transport tubes  260  and the bypass  256  does not pass underneath the downhole packer  280 . Thus, radial expansion of the compressible packing element  282  is not hindered because the element  282  is disposed about the outside of the packer apparatus  250 . Moreover, the packing element  282  can have a greater mass of sealing material and can have more uniform element expansion and less complicated pack-off mechanism. 
     In another embodiment shown in  FIG. 4B , the concentric bypass packer apparatus  250  has a transport tube  260 ; a concentric bypass  256 ; an uphole packer  270  having a cup element  272 ; and a downhole packer  275  having a hydraulically-actuated, compression-set packer  290 . Many features of this bypass packer apparatus  250  are similar to those disclosed above with reference to  FIG. 4A  so that like reference numerals are used for similar components. Additionally, use of the packer apparatus  250  is similar to the steps outlined previously. 
     Overall, the uphole cup packer  272  serves as a base on which gravel pack sand can settle once circulation through the concentric bypass  256  stops due to the downhole screen section  240 D below the cup packer  272  becoming covered with gravel pack sand. Additionally, the hydraulically-actuated, compression-set packer  290  serves to isolate the upper annulus ( 16 U) from the downhole annulus ( 16 D) after the gravel packing operation so that this packer  290  can remain unset (unexpanded) until after the gravel pack is performed. 
     The hydraulically-actuated, compression-set packer  290  has a compressible packing element  292  disposed between an end ring  294  and a hydraulic piston  296 . Fluid pressure communicated through an internal port  297  of the bypass packer&#39;s bore  254  forces the piston  296  against the element  292  and compresses it against the end ring  294 . Shear pins and the like (not shown) can be provided so that the hydraulic piston  296  does not move until a particular pressure level is reached. Additionally, lock rings and the like (not shown) can be provided to keep the piston  296  set once activated. 
     In one embodiment, the hydraulically-actuated packer  290  is set by using fluid pressure supplied to the internal port  296  via the gravel pack assembly or via an internal string of pipe (i.e., washpipe  214  or other tool) run inside the gravel pack assembly. Such a tool can deliver the fluid pressure when desired in the course of operations to set the element  292  against the wellbore or casing. In an alternative or in addition to the applied pressure, the downhole packer can use hydrostatic pressure in the wellbore against a hydrostatic chamber (not shown) in conjunction with a piston  296  to compress the compressible packing element  292 . 
     Finally, as noted above, the downhole packer  275  on the bypass packer apparatus  250  can also be a swellable packer if suitable for the implementation. Turning to  FIG. 4C  then, an embodiment of a concentric bypass packer apparatus  250  having a transport tube  260 , a concentric bypass  256 , an uphole packer  270  with a cup element  272 , and a downhole packer  275  having a swellable packer element  295  for the gravel pack assembly is shown in cross-section. The swellable packer element  295  can be configured to swell in response to various conditions. Additionally, the swellable packer element  295  can use features disclosed in incorporated US2013/0161000 to accommodate a volume of gravel displaced by the swellable packer  295  in the wellbore annulus. 
       FIG. 5  illustrates a gravel pack assembly  200  according to another embodiment of the present disclosure. Rather than gravel packing the upper annulus  16 U before the downhole annulus  16 D as in  FIGS. 2 and 3A-3D , gravel packing in this assembly  200  packs the downhole annulus  16 D and then the uphole annulus  16 U. As such, the concentric bypass packer apparatus  250  does not require transport tubes as used in previous embodiments. 
     As before, the concentric bypass packer apparatus  250  disposed between the two screen sections  240 U-D includes at least two packers  270  and  275  and a concentric bypass  256 . The first uphole packer  270  restricts passage of at least gravel (and not necessarily fluid) from the uphole annulus  16 U to the downhole annulus  16 D, although the uphole packer  270  could be used to achieve at least some fluid isolation of the annulus  16 . This uphole packer  270  can be a passive type of packer, such as a cup packer  272  shown, that freely engages the sidewall of the borehole  10  or casing  12 . 
     By contrast, the second downhole packer  275  is independently-actuated to engage the sidewall of the borehole  10  or casing  12 . As such, the downhole packer  275  is an active type of packer that deploys unexpanded into the borehole  10  and is later activated to engage the borehole or casing wall as detailed below. Once activated, the downhole packer  275  isolates fluid passage between the uphole and downhole annuli  16 U-D to isolate the two zones. 
     As shown in  FIG. 6A , the downhole packer  275  is run downhole in an unactivated state. Meanwhile, the uphole packer  270 , such as the cup packer  272  shown, is adapted to passively engage the surrounding borehole  10  or casing  12  to seal at least gravel passage from the uphole annulus  16 U to the downhole annulus  16 D. 
     A gravel pack operation begins by running the washpipe  214  down the assembly  220 , and a tool  300  on the washpipe  214  seals inside the packer apparatus  250 . In particular, a stinger  310  of the tool  300  seals inside the bypass packer apparatus  250 , while a valve  320  of the tool  300  remains closed. Slurry is communicated down the annulus  16  around the assembly  220  from the cross-over tool ( 212 :  FIG. 5 ) uphole. Because fluid communication up the washpipe  214  is isolated from the uphole screen section  240 U by the closed valve  320  and by the stinger  310  sealed inside the bypass packer apparatus  250 , the slurry enters the concentric bypass  256  from the uphole annulus  16 U and begins to pack around the lower screen section  240 D. 
     The carrier fluid in the slurry enters the downhole screen section  240 D so that gravel deposits in the downhole annulus  16 D around the lower screen section  240 D. Once the carrier fluid enters the assembly&#39;s body  220 , the fluid is circulated up the washpipe  214  disposed in the inner passage  222  of the assembly  200 . 
     Once the lower screen section  240 D is covered as shown in  FIG. 6B , the slurry flow through the concentric bypass  256  wanes and ceases. In particular, flow of slurry becomes more limited as the gravel packs around the lower screen section  240 D and less carrier fluid can flow through the lower screen section  240 D. Therefore, pressure builds, and the valve  320  on the washpipe tool  300  opens so that fluid returns can enter the washpipe  214  from the upper screen section  240 U instead. 
     With the valve  320  open, the slurry communicated down the uphole annulus  16 U and checked from passing to the downhole annulus  16 D by the uphole packer  270  begins to pack around the upper screen section  240 U. Fluid returns can enter the washpipe  214  from the upper screen section  240 U through the open valve  320  on the washpipe tool  300 . 
     As with the other embodiments of the present disclosure, the bypass packer apparatus  250  for the system  200  in  FIGS. 5 and 6A-6B  can use any of the various types of packing elements for the downhole packer  275 . For example,  FIG. 7A  illustrates an embodiment of the concentric bypass packer apparatus  250  having a mechanically-actuated compression-set packer  280  as the downhole packer  275 ; and  FIG. 7B  illustrates an embodiment of the concentric packer apparatus  250  having a hydraulically-actuated, compression-set packer  290  for the downhole packer  275 . Finally,  FIG. 7C  illustrates an embodiment of the bypass packer apparatus  250  having a swellable packer element  295  as the downhole packer  275 . 
     Many of the components of the packer apparatus  250  in  FIGS. 7A-7C  are similar to those described above with reference to  FIGS. 4A-4C  so that like reference numerals are used for similar components. Therefore, these elements are not described again. However, because the assembly  200  of  FIGS. 5 and 6A-6B  gravel packs the downhole annulus  16 D first, each of these bypass packers  250  lacks a transport tube as in previous embodiments. Instead and as preferably shown, the upper port  258   a  of the concentric bypass  256  on the packers  250  has a hood  265 , down-hole facing passage, or other feature for creating a tortious path for the flow of slurry. Thus, slurry collecting on the upper cup packer  272  during gravel packing must follow along the tortious path into the hood  265  and then into the upper port  258  before entering the bypass  256 . Once the downhole section ( 240 D) is packed off, such a tortious path can help the upper section ( 240 U) begin to fill with gravel. 
     Because the assembly  200  of  FIGS. 5 and 6A-6B  gravel packs the downhole annulus  16 D first, a means for controlling fluid flow in the washpipe  214  is needed. To that end, the system  200  uses the washpipe tool  300  for the washpipe  214  that disposes inside the concentric packer apparatus  250  as discussed previously.  FIGS. 8A-8B  illustrate an embodiment of a washpipe tool  300  for the washpipe ( 214 ) in closed and opened conditions, and  FIG. 8C  illustrates the washpipe tool  300  disposed in a concentric bypass packer apparatus  250  of the present disclosure. 
     The washpipe tool  300  is equipped with a sealing stinger  310  connecting with a connector  302  to an uphole washpipe section ( 214 :  FIG. 5 ). The other end of the stinger  310  has a coupling  304  for connecting to a downhole washpipe section (not shown) so that the internal bore  312  of the stinger  310  acts as a section of the washpipe ( 214 ). The stinger  310  has the pressure differential valve  320  uphole of an engagement shoulder  315  on the outside of the stinger  310 . Downhole of the shoulder  315 , the stinger  310  has a polished surface  316  with an arrangement of seals  318 . 
     The tool  300  prevents the fluid component of the slurry from diverting into the upper screen section ( 240 U:  FIG. 5 ) and flowing instead inside the annulus of the screen section ( 240 U) and washpipe  214  during operations. As would be expected, loss of carrier fluid to the upper screen section ( 240 U) would prematurely dehydrate the slurry across the upper screen section ( 240 U), resulting in an incomplete gravel pack across the lower screen section ( 240 D:  FIG. 5 ). 
     During gravel pack operations, the washpipe  214  is run in until the engagement shoulder  315  engages an internal shoulder  255  inside the packer apparatus  250 , as best shown in  FIG. 8C . The seals  318  along the polished surface  316  of the stinger  310  seal inside the packer&#39;s internal bore  254 . Slurry in the uphole annulus ( 16 U:  FIG. 5 ) uphole of the packer  250  passes through the concentric packer apparatus  250  and fills the downhole annulus ( 16 D:  FIG. 5 ) as described above. Fluid returns passing through the lower screen section ( 240 D) can flow up the washpipe ( 214 ) and through the stinger  310  to the crossover tool ( 210 :  FIG. 5 ). 
     All the while, fluid entry into the upper screen section ( 240 U) is essentially blocked by the sealed tool  300  inside the packer apparatus  250 . Consequently, the hydrated sand slurry is forced to flow through the bypass  256  in the upper part of the concentric packer apparatus  250 , underneath the cup packer  272 , and into the annulus around the lower screen section ( 240 D) so the fluid returns can be taken up by the washpipe and tool  300 . The chance of successfully covering the lower screen section ( 240 D) with sand is increased. 
     Once the lower screen section ( 240 D) is covered, a pressure increase occurs, which opens the pressure differential valve  320  installed on the tool  300  inside the upper screen section ( 240 U). In particular, the valve  320  includes a housing  322  sealed with seals  324  on the tool. Shear pins  326  secure the housing  322  closed over the tool&#39;s ports  317 . Pressure buildup outside the valve&#39;s housing  322  relative to inside the tool  300  eventually breaks the shear pins  326 . The housing  322  then shifts away from the port  317 , allowing for fluid communication therethrough. 
     Once the valve  320  opens, fluid returns from the sand slurry can flow through the upper screen section ( 240 U), through the open differential valve  320 , into the stinger  310  via ports  317 , and eventually up the uphole washpipe section (not shown). This allows the gravel pack sand to dehydrate around the upper screen section ( 240 U). 
     As noted above, the packer apparatus  250  of the present disclosure can be used for cased or open holes. For cased holes, the upper packer  270  can be a cup packer  272  to form a friction seal with the surrounding casing wall. The packer apparatus  250  can be adapted for open hole applications by making the upper packer  270  hydraulically or hydrostatically-actuated with a compressible packing element that expands enough to seal on the irregularities of an open hole. This arrangement could also be used in cased hole. Finally, the second packer  275  can be a swellable packer, but is more preferably a compression-set packer that is mechanically-actuated, hydraulically-actuated, and/or hydrostatically-actuated packer. However, either one or both of these first and second packers  270  and  275  can be electronically-actuated through the use of radio-frequency identification (RFID) tags, pressure pulse signals, or other detected activation. 
     As one example,  FIG. 9A  shows an embodiment of a concentric bypass packer apparatus  250  having a downhole packer  275  that is compression-set and electronically-actuated. The packer apparatus  250  in this example includes a transport tube  260  as with the embodiments of  FIGS. 4A-4C , but it could lack such a transport tube comparable to other embodiments disclosed herein if used with a washpipe tool ( 300 ) as above. The packer apparatus  250  includes many of the same components as before so that like reference numerals are used for similar components. 
     In contrast to previous embodiments, the packer apparatus  250  has a control unit  400  for controlling operation of the packer apparatus  250 . During operation, gravel packing can occur as before in  FIGS. 2 and 3A-3D  with slurry first collecting in an upper screen section  240 U and then passing through the transport tube  260  and the concentric bypass  256  to pack around the downhole screen section  240 D. (Alternatively, without the transport tube  260 , gravel packing can occur as before in  FIGS. 5 and 6A-6B  with slurry first collecting in the lower screen section  240 D and then packing around the upper screen section  240 D.) All the while, fluid returns can pass up through a washpipe in the internal bore  254  of the packer apparatus  250 . 
     In any event, in addition to the passive pack off provided by the upper packer  270 , operations will activate the isolation provided by the downhole packer  275  of the apparatus  250  to close the uphole and downhole screen sections  240 U-D. Here, the downhole packer  275  has a hydraulically-actuated, compression-set packer  290  as described previously with reference to  FIGS. 4B , but any of the other independently compressible arrangements can be used to isolate fluid passage between uphole and downhole annulus portions. For instance, the downhole packer  275  can use a mechanically-actuated or a hydrostatically-actuated packer. 
     To activate the compression-set packer  290 , an activation is detected with the control unit  400 , and the control unit  400  in turn initiates the activation of the packer  290 . Any of a number of activations can be used. For example, the control unit  400  can be activated with any number of techniques—e.g., RFID tags in the flow stream may be used alone or with plugs; chemicals and/or radioactive tracers may be used in the flow stream; mud pressure pulses (if the system is closed chamber, e.g. gravel bridges off in the annular area between the assembly  220  and borehole); mud pulses (if the system is actively flowing); etc. Once activation is detected, the control unit  400  operates the packer&#39;s compression setting mechanism and compresses the packer&#39;s compressible element  292  to close off the wellbore annulus. 
     In one embodiment, the control unit  400  can include components as schematically illustrated in  FIG. 9B . As shown, the control unit  400  includes a controller  402 , which can include any suitable processor for a downhole tool. The controller  402  is operatively coupled to a sensor or reader  404  and to an actuator  406 . The type of sensor or reader  404  used depends on how commands are conveyed to the control unit  400  while deployed downhole. Various types of sensors, readers  402 , or the like can be used, including, but not limited to, a radio frequency identification (RFID) reader, sensor, or antenna; a Hall Effect sensor; a pressure sensor; a telemetry sensor; a radioactive trace detector; a chemical detector; and the like. 
     As an alternative to RFID, for example, the control unit  400  can be configured to receive mud pulses from the surface or may include an electromagnetic (EM) or an acoustic telemetry system, which includes a receiver or a transceiver (not shown). An example of an EM telemetry system is discussed in U.S. Pat. No. 6,736,210, which is hereby incorporated by reference in its entirety. 
     For the purposes of the present disclosure, reference to the control unit  400  and the sensor  402  will be to an RFID based system, which may be preferred in some instances. As will be appreciated, the sensor  402  for such an arrangement can be an RFID reader that uses radio waves to receive information (e.g., data and commands) from one or more electronic RFID tags  450 , which can be active or passive, attached to a plug or other object, and deployed in the flow stream of the slurry. The information is stored electronically, and the RFID tags  450  can be read at a distance from the reader  402 . 
     To convey the information to the packer apparatus  250  at a given time during operations, the RFID tags  450  are inserted into the slurry at surface level and are carried downhole in the fluid stream. When the tags  450  come into proximity to the packer apparatus  250 , the electronic reader  402  on the tool&#39;s control unit  400  interprets instructions embedded in the tags  450  to perform a required operation. Further details of a radio-frequency identification (RFID) electronics package for the control unit can be found in WO 2010/054407, filed 10 Nov. 2009, which is incorporated herein by reference. 
     Logic of the controller  402  can count triggers, such as the passage of a particular RFID tag  450 , a number of RFID tags  450 , or the like. In addition and as an alternative, the logic of the controller  402  can use timers to actuate the actuator  406  after a period of time has passed since a detected trigger (e.g., after passage of an RFID tag  450  or after a previous operation is completed). These and other logical controls can be used by the controller  402 . 
     When a particular activation is detected, for example, the controller  402  operates the actuator  406 , which can be a switch or the like, to supply power from a power source  408  to a control&#39;s compression mechanism  410 . The power source  408  can be a battery deployed downhole with the unit  400 . The control&#39;s compression mechanism  410  can be a pump, a solenoid, a motor, or other mechanism. 
     The control&#39;s mechanism  410  (e.g., pump, solenoid, motor, etc.) couples to a packer&#39;s compression mechanism  414 , which can be a valve, piston, or sleeve of the packer  250 . For instance, the control&#39;s mechanism  410  can be operatively coupled between a pressure source or reservoir  412  and to the packer&#39;s compression mechanism  414 . In this example, the pressure source or reservoir  412  can be a reservoir of fluid, and the control&#39;s mechanism  410  can be a pump activated by the power to pump fluid pressure against the packer&#39;s mechanism  414  (e.g., valve, piston, or sleeve). Alternatively, the pressure source or reservoir  412  may be fluid communicated from the packer&#39;s internal bore  254 , and the control&#39;s mechanism  410  can be a solenoid  410  operated to open flow from the internal bore  254  to the packer&#39;s mechanism  414  (e.g., valve, piston, or sleeve). Additionally, the control&#39;s mechanism  410  may simply be a motor that moves the packer&#39;s mechanism  414  (e.g., valve, piston, or sleeve  414 ) compression-set the packer  275 . 
     In the particular embodiment shown in  FIG. 9A , for example, the control unit  400  connects an internal port  413  of the packer&#39;s bore  254  with a fluid passageway  415  to a piston chamber  299 . When activation is detected from the RFID tag  250  or the like, the control unit  400 , which can have a solenoid valve arrangement, opens fluid flow from the port  413  to the passageway  415 . Fluid pressure from the internal bore  254  can then fill the piston chamber  299  and push the piston  296  to compress the compressible packing element  292  of the packer  275 . Other arrangements of the control unit  400  as disclosed herein could also be used. 
     The foregoing description of preferred and other embodiments is not intended to limit or restrict the scope or applicability of the inventive concepts conceived of by the Applicants. It will be appreciated with the benefit of the present disclosure that features described above in accordance with any embodiment or aspect of the disclosed subject matter can be utilized, either alone or in combination, with any other described feature, in any other embodiment or aspect of the disclosed subject matter. 
     In exchange for disclosing the inventive concepts contained herein, the Applicants desire all patent rights afforded by the appended claims. Therefore, it is intended that the appended claims include all modifications and alterations to the full extent that they come within the scope of the following claims or the equivalents thereof.