Abstract:
Downhole tools for gravel pack completion processes in wellbores comprise a screen, an isolation device comprising a sealing element disposed above the screen, and an artificial lifting device disposed above the isolation device. Upon actuation, the sealing element divides the wellbore into an upper zone and a lower zone so that the screen is disposed in the lower zone and the artificial lifting device is disposed in the upper zone. The two zones are in fluid communication with each other through a longitudinal bore within the downhole tool. In operation, the artificial lifting device of the downhole tool creates a negative pressure so wellbore fluid is transported from the lower zone into the upper zone. Due to this flow of fluid through the downhole tool, gravel disposed within the wellbore becomes sufficiently fluidized to facilitate the screen being inserted into the gravel form the gravel pack completion.

Description:
BACKGROUND 
   1. Field of Invention 
   The invention is directed to gravel packs in oil and gas wells and, in particular, to downhole tools comprising screens for insertion into the gravel pack completions in wellbores. 
   2. Description of Art 
   In completing wells having production or injection zones which lie adjacent to incompetent formations formed from unconsolidated matrixes such as loose sandstone, or which lie adjacent formations that have been hydraulically-fractured and propped such as through fracturing processes, sand control problems often arise during the operational life of the well. These sand control problems are encountered when large volumes of sand and/or other particulate material such as backflow of proppants from a hydraulically-fractured formation dislodge from the formation and become entrained in the formation fluids and are produced therewith into the wellbore. These produced materials have an adverse effect on the operation of the well because they can cause erosion and plugging of the well equipment which, in turn, leads to high maintenance costs and considerable downtime of the well. 
   One technique for controlling sand production in a wellbore is referred to as “gravel packing” or forming a “gravel pack completion.” In general, a gravel pack completion comprises a screen, such as a fluid-permeable liner, a perforated liner, a slotted liner, a pre-packed screen, that is disposed within an open-hole or cased wellbore adjacent the incompetent or fractured zone and is surrounded by aggregate or particulate material collectively referred to as “gravel.” As known in the art, the gravel particles are sized to block or filter out the formation particulates that may become entrained in the produced fluids, while the openings in the screen are sized to block the gravel from flowing into the screen. 
   One method for installing a typical gravel pack completion in a wellbore involves placing the gravel in the wellbore first and then driving, rotating, or washing the screen into the gravel to form the gravel pack. To assist in installing the screen in gravel disposed in a wellbore, the liner may include one or more auger blades, referred to herein as an “auger-flighted screen.” 
   SUMMARY OF INVENTION 
   In accordance with the disclosure herein, a screen is included as part of a downhole tool designed to assist in the installation of the screen into gravel disposed in a wellbore. Broadly, the downhole tool includes the liner or screen having at least one port disposed in the screen&#39;s outer wall surface, a dynamic isolation device comprising a sealing element, and an artificial lifting device. The artificial lifting device is disposed above the dynamic isolation device which, in turn, is disposed above the screen so that the sealing element can divide the wellbore into two zones, an upper zone and a lower zone. The screen will, therefore, be disposed in the lower zone and the artificial lifting device will be disposed in the upper zone. The two zones are in fluid communication with each other through a longitudinal bore within the downhole tool. 
   In operation, the artificial lifting device of the downhole tool creates a negative pressure such that wellbore fluid is transported from the lower zone, through the downhole tool and into the upper zone. Due to this flow of fluid through the downhole tool, gravel disposed within the wellbore becomes sufficiently fluidized due to an increase in pressure within the lower zone. This fluidization of the gravel facilitates the screen to be inserted into the gravel form the gravel pack completion. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is a perspective view of one specific embodiment of a downhole tool having an auger-flighted screen disclosed herein shown in the run-in position. 
       FIG. 2  is cross-sectional view of the downhole tool of  FIG. 1  shown in the set position. 
       FIG. 3  is a detailed cross-sectional view of the artificial lift device of the downhole tool of  FIGS. 1 and 2 . 
       FIG. 4  is a perspective view of another embodiment of the downhole tool having a screen disclosed herein shown in the run-in position. 
   

   While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims. 
   DETAILED DESCRIPTION OF INVENTION 
   Referring now to  FIGS. 1-3 , one embodiment of downhole tool  40  is shown disposed in wellbore  20  within an earthen formation. Wellbore  20  comprises casing  30 . This embodiment of downhole tool  40  comprises screen  50  having bore  51 , and one or more sections  52  having ports  53  in fluid communication with bore  51  and the outer wall surface of screen  50  so that bore  51  can be placed in fluid communication with annulus  21  of wellbore  20 . As shown in  FIGS. 1-2 , screen  50  has three sections  52  connected in series through any known device or method, for example, threads (not shown). Closed end  54  of screen  50  includes bit  56  to facilitate insertion of screen  50  into the gravel (not shown) disposed within wellbore  20 . Auger  58  is spiraled or “flighted” around the outer wall surface of screen  50  to further facilitate insertion of screen  50  into the gravel. Thus, screen  50  in this embodiment is referred to as an auger-flighted screen. 
   In the embodiment of  FIGS. 1-3 , screen  50  is releasably secured to lower coupler  60  through any known device or method, for example, threads (not shown). Lower coupler  60  comprises bore  61  and is releasably secured to ported member or pup  62  through any known device or method, for example, threads (not shown). Ported member  62  includes bore  63  and one or more ports  64  in fluid communication with bore  63  and an outer wall surface of ported member  62  so that bore  63  can be placed in fluid communication with annulus  21  of wellbore  20 . 
   Ported member  62  is releasably secured to isolation device  66  through any known device or method, for example, threads (not shown). Isolation device  66  comprises bore  67 . Isolation device  66  contacts the inner wall surface of wellbore  20  when isolation device  66  is placed in the set position ( FIG. 2 ). 
   In the set position, isolation device  66 , separates annulus  21  of wellbore  20  into two zones, upper zone  22  disposed above isolation device  66  and lower zone  23  disposed above isolation device  66 . Isolation device  66  comprises a dynamic seal against the inner wall surface of wellbore  20  such that isolation device  66  is in sliding engagement with the inner wall surface of wellbore  20 . Accordingly, downhole tool  40  is capable of sliding downward along the inner wall surface of wellbore  20  during insertion or installation of screen  50  into the gravel disposed within wellbore  20 . Isolation device  66  is shown in the embodiment of  FIGS. 1-3  as comprising two swab packer cups  68 ,  70 . Such isolation devices  66  are known in the art. 
   Isolation device  66  is not required to form a leak-proof seal with the inner wall surface of wellbore  20 . Fluid is permitted to flow between isolation device  66  and the inner wall surface of wellbore  20 , provided that the connection between isolation device  66  and the inner wall surface of wellbore  20  is sufficient to allow wellbore fluid to be transported from the lower zone to the upper zone as discussed in greater detail below. 
   Isolation device  66  is releasably secured to upper coupler  72  through any known device or method, for example, threads  71  (shown in  FIG. 3 ). Upper coupler  72  comprises bore  73  and is releasably secured to artificial lift device  74  through threads  71  ( FIG. 3 ) or any other known device or method. As discussed in greater detail below, artificial lift device  74  functions by lifting, transporting, of flowing fluid from lower zone  23  of annulus  21  of wellbore  20  when isolation device  66  and, thus, downhole tool  40  is in the set position within wellbore  20 . Therefore, fluid from lower zone  23  of annulus  21  of wellbore  20  can be lifted, transported, or flowed above isolation device  66  into upper zone  22  of annulus  21  of wellbore  20  so that the fluid can be lifted, transported, or flowed up and out of wellbore  20 . 
   Artificial lift device  74  may be any device known to persons of ordinary skill in the art. In the embodiment shown in  FIGS. 1-3 , artificial lift device  74  comprises jet pump  80 . Suitable jet pumps  80  are available from Oilwell Hydraulics, Inc. of Odessa, Tex. 
   In the embodiment shown in  FIGS. 1-3 , jet pump  80  includes valve  82 , shown as a one-way check valve having ball  83 , cavity  84 , flow path  86 , fluid injector tubing  88 , fluid accelerator  90  with fluid exhaust port  92 , chamber  94 , and outlet  96 . As shown in  FIG. 3 , chamber  94  has a conical-shape to facilitate movement of fluid out from fluid exhaust port  92  and through outlet  96 . 
   Once assembled, longitudinal bore  76  is formed between screen  50 , lower coupler  60 , ported member  62 , isolation device  66 , and upper coupler  72  by placing bores  51 ,  61 ,  63 ,  67 ,  73  in fluid communication with each other. Longitudinal bore  76  is in fluid communication with outlet  96  of jet pump  80  through valve  82 , cavity  84 , flow path  86 , fluid exhaust port  92 , and chamber  94 . 
   In one particular operation of downhole tool  40 , a tubing string (not shown) is used to dispose downhole tool  40  into wellbore  20 . After disposition within wellbore  20 , isolation device  66  is activated so that annulus  21  of wellbore  20  is divided into upper zone  22  above isolation device  66  and lower zone  23  below isolation device  66 . Activation of isolation device  66  can be accomplished using known methods. 
   With particular reference to the arrows shown in  FIG. 3  that illustrate fluid flow through downhole tool  40 , after setting isolation device  66  within wellbore  20 , fluid, such as water, is pumped down fluid injector tubing  88  through fluid accelerator  90 , and out of fluid exhaust port  92  into chamber  94 . Fluid accelerator  90  and fluid exhaust port  92  increase the pressure at which the fluid is expelled from fluid injector tubing  88  thereby creating a venturi effect. Due to the increased pressure expulsion of fluid through fluid exhaust port  92 , negative pressure is created within jet pump  80  and, thus, in upper zone  22  so that wellbore fluid located within lower zone  23  of annulus  21  below isolation device  66  is lifted, transported, or flowed through ports  64  of ported member  62  and through ports  53  in screen  50 , into longitudinal bore  76 . The wellbore fluid continues to be lifted, transported, or flowed up through longitudinal bore  76  and into jet pump  68  through valve  82 . The wellbore fluid is then lifted, transported, or flowed through flow path  86  until it mixes with the fluid being pumped down fluid injector tubing  88 , through fluid accelerator  90 , and out of fluid exhaust port  92  into chamber  94 . This mixture of wellbore fluid with the fluid being pumped down fluid injector tubing  88  then exits jet pump  80  through outlet  96  into upper zone  22  of annulus  21  of wellbore  20  so that it can travel within wellbore  20  up toward the surface of wellbore  20 . 
   As a result of the activation of jet pump  80 , the wellbore fluid is lifted, transported, or flowed from lower zone  23  of annulus  21  to pull hydrostatic pressure off of the upper surface of the gravel (not shown) which lessens the overburden pressure acting downward on the top of the gravel. Therefore, the gravel is fluidized sufficiently to facilitate installation of screen  50  into the gravel. In other words, as a result of fluidization of the gravel due to wellbore fluid being lifted, transported, or flowed from lower zone  23  into upper zone  22 , downhole tool  40  and/or screen  50  can be moved downward more easily so that screen  50  is inserted or installed into the gravel. In one particular embodiment, screen  50  is rotated to facilitate installation of screen  50  into gravel. In another embodiment, downhole tool  40  and, thus, screen  50 , is rotated to facilitate installation of screen  50  into gravel. 
   As mentioned above, the methods of installing the liner or screen into the gravel temporarily relieve an overbalance or overburden pressure acting on the top of the gravel relative to the earthen formation. This overburden pressure is relieved by decreasing the pressure above isolation device  66  and increasing the pressure below isolation device  66  so that the gravel becomes fluidized as a result of wellbore fluid being lifted, transported, or flowed from and through lower zone  23  and into upper zone  22 . This fluidization of the gravel facilitates insertion of screen  50  into the gravel. 
   Referring now to  FIG. 4 , in another embodiment, downhole tool  140  includes screen  150 , isolation device  166 , and artificial lifting device  174 . Each of these three components is releasably connected directly to each other so that screen  150  is disposed below isolation device  166  and isolation device  166  is disposed below artificial lifting device  174 . With the exception of screen  50  comprising auger  58  in the embodiment shown in  FIGS. 1-3 , each of screen  150 , isolation device  166 , and artificial lifting device  174  in the embodiment shown in  FIG. 4  is identical to screen  50 , isolation device  66 , and artificial lifting device  74  in downhole tool  40  ( FIGS. 1-3 ). Additionally, downhole tool  140  operates in the same manner as described above with respect to downhole tool  40  ( FIGS. 1-3 ). 
   It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. For example, the screen is not required to include an auger. Additionally, the artificial lift device is not required to be a jet pump. Further, the jet pump is not required to include a valve or any of the other the specific components described with respect to the jet pump shown in  FIGS. 2-3 . Moreover, the isolation device can be any type of isolation device known in the art used to divide a wellbore and be in sliding engagement with the inner wall surface of the wellbore. Additionally, the upper and lower couplers are not required. Further, the inner wall surface of the wellbore may be disposed along the open hole formation, along wellbore casing (as shown in  FIGS. 1-2  and  4 ), or along a tubular member, including a packer or bridge plug, disposed within the wellbore casing or open hole formation. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.