Abstract:
According to the present invention, there is provided a well pumping system comprising a length of coiled tubing extending to the surface of the well, a first electric pump, a first electric motor, and a sealing means that seals against the side of the well. The sealing means include a first fluid path through which coiled tubing is in fluid communication with the well beneath the sealing means, and a second fluid path through which first electric pump is in fluid communication with the well beneath the sealing means.

Description:
This invention relates to Electric Submersible Pumps that can be deployed on a length of coiled tubing. 
     BACKGROUND 
     Electrical submersible pumps are commonly used in oil and gas wells for producing large volumes of production fluid. An electrical submersible pump (hereinafter referred to “ESP”) normally has a centrifugal pump with a large number of stages of impellers and diffusers. The pump is driven by a downhole motor, which is a large three-phase motor. A seal section separates the motor from the pump to equalise the internal pressure of lubricant within the motor to the pressure of the well bore. Often, additional components will be included, such as a gas separator, a sand separator and a pressure and temperature measuring module. 
     An ESP is normally installed by securing it to a string of production tubing and lowering the ESP assembly into the well. Production tubing is made up of sections of pipe, each being about 30 feet in length. The well will be ‘dead’, that is not be capable of flowing under its own pressure, while the pump and tubing are lowered into the well. To prevent the possibility of a blowout, a kill fluid may be loaded in the well, the kill fluid having a weight that provides a hydrostatic pressure significantly greater than that of the formation pressure. 
     In normal operations it is desirable to access the reservoir below the ESP to perform a production log to determine where the different fluids are flowing from and perform treatments using coiled tubing to either stimulate a section of reservoir or seal a section of the reservoir producing too much water. 
     Coiled tubing has been used for a number of years for deploying various tools in wells, including wells that are live. A pressure controller, often referred to as a stripper and blowout preventer, is mounted at the upper end of the well to seal around the coiled tubing while the coiled tubing is moving into or out of the well. The coiled tubing comprises steel tubing that wraps around a large reel. An injector grips the coiled tubing and forces it from the reel into the well. 
     SUMMARY 
     It is an objective of this invention to be able to provide an electric submersible pump banded to the coiled tubing and lowered into a well. 
     Another objective is to be able to access the well below the ESP via the bore of the coiled tubing while the ESP is running. 
     Another objective is to have a conventional sub surface safety valve in the ESP discharge flow path 
     Another objective is to have multi barriers in the coiled tubing to ensure it does not provide a leak path to surface. 
     Another objective is to install two pumps in parallel to either double the production capability of the well or provide redundancy 
     According to the present invention, there is provided a well pumping system comprising
         a length of coiled tubing extending to the surface of the well   a first electric pump and a first electric motor   a sealing means that seals against the side of the well   the sealing means wherein the sealing means include a first fluid path through which coiled tubing is in fluid communication with the well beneath the sealing means, and a second fluid path through which first electric pump is in fluid communication with the well beneath the sealing means.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following figures will be used to describe embodiments of the invention. 
         FIG. 1  is a side view of the well from surface to total depth, showing the ESP relative to the coiled tubing, well tubing, wellhead and wiring. 
         FIG. 2  is a side view of the well from surface to total depth, showing the ESP relative to the coiled tubing, well tubing, wellhead and wiring, and in addition the inclusion of a sub surface safety valve in the downstream path from the ESP 
         FIG. 3  is a similar view to  FIG. 2  with the reservoir being accessed below the ESP by a wireline logging tool via the inside of the coiled tubing. 
         FIG. 4  is a similar view to  FIG. 2  with the reservoir being accessed below the ESP by a coiled tubing work string via the inside of the coiled tubing. 
         FIG. 5  is a side view of the ESP handed to the coiled tubing 
         FIG. 6  is a side view of a two ESP installation, one stacked on top of the other each having individual inlets from the reservoir and a common discharge into the production tubing surrounding the ESP&#39;s and external to the coiled tubing. 
         FIG. 7  is a plan view of the single ESP installation of  FIG. 5 . 
         FIG. 8  is a plan view of the tandem ESP installation of  FIG. 6 . 
         FIG. 9  is a side view of the coiled tubing and sub surface safety valve arrangement situated at a suitable depth below surface. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , the ESP system comprises an electric motor  22  and electric pump  24  suspended on a length of coiled tubing  20  which extends down a well tubing  30 , hanging from a well head  25 . The end of the coiled tubing  20  and the electric pump  24  terminate in a stinger  26 . 
     In order to install the ESP system, electric motor  22 , electric pump  24  are secured to the coiled tubing  20 , and stinger  26  is secured to the ends of the electric pump  24  and coiled tubing  20 , and the whole system is lowered down the well tubing  30  on the coiled tubing until the stinger  26  abuts against a locating profile  45 . As the system is lowered, a power cable  32  supplying the motor is banded to the coiled tubing and is terminated in a wellhead in a conventional manor. When the stinger  26  has located in the well tubing, the top of the coiled tubing is secured on a tubing hanger in the Christmas tree upper flange  37 . 
     The stinger  26  includes a sealing means  72  which seals against the well tubing  30 . The stinger also features a double bore through which the coiled tubing  20  and the inlet  27  of the pump  24  extend through into the reservoir beneath the stinger. The coiled tubing includes upper and lower seals  43 ,  42  which block its inner bore. As will be described in more detail later, these seals may be removable. 
     Once the stinger  26  has engaged with the locating profile  45 , the electric motor  22  and electric pump  24  may be activated to pump well bore fluids from the reservoir beneath the stinger up through the inside of the well tubing  30  above the stinger and the outside of the coiled tubing  20  to the wellhead to exit through a side port  39  of the Christmas tree. 
     Referring to  FIG. 2 , the ESP system may also include a sub-surface safety valve (SSSV). In this embodiment, an SSSV  41  is attached to the coiled tubing  20  at an intermediate region of the ESP system, by a packer  36 . In a similar manner to the stinger  26 , the packer  36  seals against the well tubing  30 , and has two bores, one of which the coiled tubing  20  extends through, and one of which the SSSV extends through. The packer  36  also has an electrical feedthrough for the power cable  32 ,  35 . The SSSV  41  is controlled via a SSSV control line  52  which exits the wellhead, for example through its own bulkhead. An additional seal  44  is provided in the coiled tubing  20  in the region of the SSSV. In a similar way as previously described, production fluid may be pumped through the pump inlet  27  from beneath the stringer  26 , through the pump  24  out of the outlet  29 , up the well bore to the packer, through the SSSV  41 , and out through the side port  39 . Where an emergency where the well has to be closed off, for example where the surface production facilities fail, the SSSV may be activated so that the well bore is closed off. 
     The SSSV  41  is shown in more detail in  FIG. 9 . The SSSV  41  has a packer portion  64  has a first bore  68  which constrains fluid communication in the well tubing  30  (not including the separate fluid path of the coiled tubing  20 ) through the safety valve means  65 , and a second bore  69  through which the fluid path of the coiled tubing  20  passes. Rubber packing elements  63  seal the packer  64  against the side of the well tubing  30 . When the valve means  65  is activated, the fluid path through the well tubing  30  by the flapper valve  70  (not including the coiled tubing  20 ) is blocked. This figure also shows a profile  67  into which the seal  44  is located; the other seals  42 ,  43 ,  46  may be located in similar profiles. 
     Referring to  FIG. 3 , tools such as a logging tool  47  may be run down the well through the coiled tubing  20 . To insert the tool  47 , a lubricator  50  is attached to the coiled tubing port, and the tool  47  lowered through the coiled tubing whilst attached to a wireline paid out from reel (not shown) over pulleys  21 . The seals  42 ,  43 ,  44  in the coiled tubing are removed in some manner, for example by retrieval through the coiled tubing  20  from the surface using a GS fishing tool. The tool  47  is then lowered past the end of the coiled tubing  20  as far as desired. The tool  47  may be winched up and removed from the well simply by reversing the operation. The seals  42 ,  43 ,  44  (or replacement seals) are then lowered or dropped down the coiled tubing  20  to their original position. Production fluid may still be pumped through the ESP system during the installation of the tool  47  in the well. 
     Referring to  FIG. 4 , a second length of coiled tubing  60 , having a smaller diameter than the bore of the coiled tubing  20 , may be introduced into the coiled tubing  20  through the coiled tubing port  37  using a coiled tubing injector  31 . As for the previous example, the seals  42 ,  43 ,  44  are removed before or during the introduction of the second coiled tubing  60  through the first coiled tubing  20 . The second length of coiled tubing may extended down through the end of the coiled tubing  20  to a lower part of the well. The coiled tubing  60  may for example be used to inject fluid or gas at a lower part of the well. The coiled tubing  60  may of course be removed from the well simply by reversing the operation. As for the previous example, the seals  42 ,  43 ,  44  in coiled tubing  20  may be replaced by various known methods. 
     Referring now to  FIG. 6 , a second electric motor  55 , motor protector  53  and electric pump  54  may be included in the ESP system. In this embodiment, the inlet  57  of the pump  54  ports onto the side of the coiled tubing  20  through a Y-tool  59 . An additional retrievable seal  46  is included in the coiled tubing  20 , immediately above where the second pump  54  ports onto the coiled tubing  20 . The electric motor  55 , and electric pump  54  are powered by a second power cable  58 . If an SSSV is included, the power cable  58  extends through an electrical feedthrough together with power cable  32 . 
     In normal use, this embodiment may be operated as for the previously described embodiments, with well fluid being drawn through the pump  24 , and up through the well to the surface, whilst the coiled tubing  20  may have its seals  42 ,  43 ,  44 ,  46  removed so that tools  47  or smaller diameter coiled tubing  60  may be run down the coiled tubing  20 . However, should a fault develop with the pump  24  or motor  22  which prevents the pump  24  from drawing well fluid, the seal  42  may be removed from the coiled tubing (which may involve removal and replacement of seals  43 ,  44 , and  46 ) and second motor  55  activated so that the pump  54  draws well fluid through the end of the coiled tubing  20 , past the stinger  26 , into the pump  54  via the Y-tool  59 , out of the pump outlet  71  and up through the well and out of the side port  39 .