Abstract:
In combination, an inverted electric submersible pump (ESP) sized to fit within a downhole production path and a coiled tubing string. The coiled tubing string has an internal bore, and one or more supply lines housed within the internal bore and connected between surface and the inverted ESP. The inverted ESP has a pump section and a motor section, the motor section disposed above the pump section, and the pump section having one or more inlet ports and one or more outlet ports. At least one sealing element is positioned between the one or more inlet ports and the one or more outlet ports and is sized to seal against the downhole production path. A coiled tubing connection sealably connects the motor section to the coiled tubing string.

Description:
FIELD 
       [0001]    This relates to a method of installing or removing an electric submersible pump in a well with a positive well head pressure. 
       BACKGROUND 
       [0002]    In wells with a positive well head pressure, such as SAGD (steam assisted gravity drainage) wells, the well must be depressurized, generally by cooling the well, in order to install or remove the electric submersible pump. The process to cool the well and reheat the well afterward adds a number of days onto the servicing of the well. 
       SUMMARY 
       [0003]    According to an aspect, there is provided a method of servicing an electric submersible pump in a well with a positive well head pressure. The well comprises a casing and a wellhead mounted to the casing. The wellhead has a sealable injection port and at least one production port. The method comprises the steps of providing production tubing in the casing connected to the wellhead such that production fluids flow through the production tubing and out the at least one production port of the wellhead; a coil tubing string having an electric submersible pump at a downhole end of the coil tubing string and control lines through the coil tubing string for controlling the electric submersible pump; and a pump-receiving housing above the injection port of the wellhead, the pump-receiving housing being sealed to atmosphere when the injection port is open, and openable to atmosphere when the injection port is sealed. The injection port is sealed and the pump-receiving housing is opened to insert or remove the electric submersible pump from the pump-receiving housing. The pump-receiving housing is closed and the injection port is opened to move the electric submersible pump to or from the production tubing in the well. The electric submersible pump may be an inverted electric submersible pump whereby the motor and customized components to attach the motor to the coiled tubing is at the top of the assembly, and the pump is at the bottom of the assembly. The control lines may comprise an oil feed line for continuously providing the electric submersible pump with clean oil and to maintain a positive pressure relative to the well pressure at the electric submersible pump location. 
         [0004]    According to another aspect, there is provided a method of removing an electric submersible pump from the well. The method comprises the steps of providing production tubing in the casing connected to the wellhead such that production fluids flow through the production tubing and out the at least one production port of the wellhead; a coil tubing string positioned through the injection port and the production tubing, the coil tubing string having an electric submersible pump at a downhole end of the coil tubing string and control lines through the coil tubing string for controlling the electric submersible pump, the electric submersible pump being sized to pass through the production tubing; and a pump-receiving housing above the injection port of the wellhead, the pump-receiving housing being sealed to atmosphere when the injection port is open, and openable to atmosphere when the injection port is sealed. The coil tubing is retracted from the well such that the electric submersible pump is withdrawn through the injection port and into the pump-receiving housing. The injection port is sealed and the pump-receiving housing is opened to atmosphere. The electric submersible pump is removed from the pump-receiving housing. 
         [0005]    According to another aspect, there is provided a method of inserting an electric submersible pump in the well. The method comprising the steps of providing production tubing in the casing connected to the wellhead such that production fluids flow through the production tubing and out the a least one production port of the wellhead; a coil tubing string having an electric submersible pump at a downhole end of the coil tubing string and control lines through the coil tubing string for controlling the electric submersible pump, the electric submersible pump being sized to pass through the production tubing; and a pump-receiving housing above the injection port of the wellhead, the pump-receiving housing being sealed to atmosphere when the injection port is open, and openable to atmosphere when the injection port is sealed. With the injection port sealed, the electric submersible pump is positioned in the pump-receiving housing. The pump-receiving housing is sealed to atmosphere, and the injection port is opened. The coil tubing and the electric submersible pump is lowered into the production tubing in the well with a positive well head pressure through the injection port of the wellhead and is seated into a pressure sealing seat located at the downhole end of the tubing. 
         [0006]    According to another aspect, there is provided, in combination, a coil tubing string and an inverted electric submersible pump (ESP). The coil tubing string comprises an internal bore and control lines housed within the internal bore. The control lines extend from the surface end to the pump connection end. An oil supply supplies oil to the inverted ESP through at least one control line at a pressure greater than the pressure of a wellbore. The inverted ESP is sized to fit within production tubing and comprises a pump section and a motor section. The motor section is disposed above the pump section. The pump section comprises at least one inlet port and at least one outlet port. A coil tubing connection sealably connects the motor section to the coil tubing string. A seat engagement seal is provided on the pump section between the at least one inlet port and the at least one outlet port. The seat engagement seal engages a downhole end of the production tubing, such that the inlet ports are in communication with wellbore fluids, and the outlet ports are in communication with an interior of the production tubing. 
         [0007]    According to another aspect, there is provided, in combination, an inverted electric submersible pump (ESP) sized to fit within a downhole production path and a coiled tubing string. The coiled tubing string comprises an internal bore, and one or more supply lines housed within the internal bore and connected between surface and the inverted ESP. The inverted ESP comprises a pump section and a motor section, the motor section disposed above the pump section, the pump section comprising one or more inlet ports and one or more outlet ports; at least one sealing element positioned between the one or more inlet ports and the one or more outlet ports that is sized to seal against the downhole production path; and a coiled tubing connection for sealably connecting the motor section to the coiled tubing string. 
         [0008]    According to another aspect, the inverted ESP may comprise one or more of the following features: the one or more supply lines may comprise an oil delivery line connected between a supply of oil on surface and the inverted ESP; the one or more supply lines may comprises one or more transmission lines, each transmission line comprising an electric power line or a temperature and pressure data acquisition and transmission line, and wherein the oil delivery line is a metal capillary tube and provides structural support to the one or more transmission lines; the inverted ESP may comprise a thrust chamber between the pump section and the motor section, and the oil may be supplied by the oil delivery line passes through the motor section and the thrust chamber prior to being ejected from the inverted ESP; the oil may be ejected into the interior of the production path; the oil may be ejected from the inverted ESP from a check valve; the oil may be supplied to the oil delivery line by a positive displacement pump; the at least one pump sealing ring may be mounted to an exterior surface of the thrust chamber; the at least one pump sealing ring and the pump seating nipple may be made from metal and the at least one pump sealing ring engages the pump seating nipple in an interference fit engagement; the pump sealing ring and the pump seating nipple may be sized such that interference fit engagement causes the at least one pump sealing ring to elastically deform; the pump sealing ring and the pump seating nipple may be passive sealing elements; and the one or more inlet ports may be directly open to a hydrocarbon formation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    These and other features will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to be in any way limiting, wherein: 
           [0010]      FIG. 1  is a side elevation view of the apparatus for servicing an electric submersible pump. 
           [0011]      FIG. 2  is a side elevation view of the well completion with the electric submersible pump. 
           [0012]      FIG. 3  is a detailed side elevation view in section of the coiled tubing string. 
           [0013]      FIG. 4  is a detailed side elevation view in section of a pump seating nipple and pump sealing rings. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    A method of servicing an electric submersible pump in a well with a positive well head pressure will now be described with reference to  FIGS. 1-4 . 
         [0015]    The method described below may be used to install or remove an electric submersible pump  10  without having to cool or depressurize the well. This method may be particularly useful for thermal stimulated wells such as SAGD wells or other wells with a positive well head pressure, or other wells with a positive well head pressure that are required to be pressure relieved prior to being opened. Referring to  FIG. 2 , pressurized well  12  includes a casing  14  and a wellhead  16  mounted to casing  14 . Wellhead  16  has a sealable injection port  18 , and production ports  20 . Referring to  FIG. 1 , injection port  18  may be sealed by a BOP  32  (blowout preventer) as shown, or it may also be sealed by a valve, a plug, etc., which may be above or below the actual port  18 . Referring again to  FIG. 2 , the number of production ports  20  may vary depending upon the design of wellhead  16 . Production tubing  22  is positioned in casing  14  and is connected to wellhead  16 . Production fluids that are pumped upward by electric submersible pump  10  flow through production tubing  22  and out production ports  20  of wellhead  16 . Electric submersible pump  10  is carried by a coil tubing string  24  at a downhole end  26  of coil tubing string  24 , and is sized such that it is able to be run through production tubing  22 . Supply lines  28 , which may be instrumentation lines, control lines, or electrical or fluid delivery lines, are preferably all run through and enclosed within coil tubing string  24  and connect to electric submersible pump  10 . Supply lines  28  may include transmission lines such as power and communication lines for providing control signals, and oil feed lines that continuously provide clean oil to the electric submersible pump  10  and maintain a positive pressure relative to the well pressure at the ESP location. Preferably, fluids provided through supply lines  28  will be fed using positive displacement pumps at ground surface. Also preferably, electric submersible pump  10  is designed such that clean oil is constantly pumped through from surface, which prevents any unnecessary wear from dirty oil, and also helps create a positive seal against downhole contaminants This may be done through a capillary tube, such as a metal capillary tube that can provide structural support to other supply lines  28 , such as power or signal lines. A pump-receiving housing  30 , shown in  FIG. 1 , is located above injection port  18  of wellhead  16 . The height of pump receiving housing  30  will depend upon the size of electric submersible pump  10 . Pump-receiving housing  30  is designed such that is may be sealed to the atmosphere when injection port  18  is open, and openable to the atmosphere when injection port  18  is sealed. In other words, housing  30  works with injection port  18  to ensure that well  12  is always sealed when it is pressurized. Referring to  FIG. 1 , a blowout preventer  32  is located above wellhead  16  and below pump-receiving housing  30 . Coil tubing injector  34  is located above pump-receiving housing  30  and, referring to  FIG. 2 , is used to control the position of coil tubing string  24  and electric submersible pump  10  in well  12 . 
         [0016]    With the elements described above, electric submersible pump  10  may be installed or removed without having to cool well  12 . In order to insert electric submersible pump  10  into a well with a positive well head pressure, injection port  18  is first sealed by closing BOP  32  and pump-receiving housing  30  is opened. Electric submersible pump  10  is connected to coil tubing string  24  and inserted into housing  30 . Pump-receiving housing  30  is then closed and sealed to atmosphere and BOP  32  is opened to allow electric submersible pump  10  to be inserted through injection port  18  in wellhead  16  and into well  12  by operating coil tubing injector  34 . In order to remove electric submersible pump  10  from pressurized well  10 , the process is reversed, with coil tubing injector  34  lifting electric submersible pump  10  through wellhead  16  and into housing  30 . BOP  32  is then closed and sealed, and housing  30  is opened to provide access to electric submersible pump  10 . Electric submersible pump  10  may then be serviced or replaced, as necessary. 
         [0017]    As depicted, electric submersible pump  10  is preferably an inverted electric submersible pump, and is run off a 1¼″-3½″ coil tubing string  24  that contains the instrumentation lines. Other sizes may also be used, depending on the preferences of the user and the requirements of the well. When compared with traditional electric submersible pumps, electric submersible pump  10  lacks the seal section, motor pothead and wellhead feedthrough. As shown, electric submersible pump  10  includes a power head  27 , motor section  38 , thrust chamber  40 , electric submersible pressure sealing seat  42  and electric submersible pump section  44 . Thrust chamber  40  includes two mechanical seals with a check valve (not shown), and replaces the conventional seal/protector section that separates pump section  44  and motor section  38 . The check valve in thrust chamber  40  allows the lubricating fluid supplied by supply line  28  to exit thrust chamber  40  and comingle with, for example, produced fluids from the well with the pump discharge from outlet ports  50 . Pressure sealing seat  42 , commonly referred to in industry as a pump seating nipple, has a seal  46  between inlet ports  48  and outlet ports  50 . Inlet ports  48  are in communication with downhole fluids to be pumped to surface via outlet ports  50 , which are positioned within production tubing  22 . 
         [0018]    Referring to  FIG. 4 , a detailed view of an example of an engagement between pump seating nipple  42  and electric submersible pump  10  is shown. Pump seating nipple  42  is shown as being located on an inner surface toward the end of production tubing  22 , and seal  46  is provided by pump sealing rings  52  carried by electric submersible pump  10  that engage pump seating nipple  42  in an interference fit and engagement shoulders  47 . Pump seating nipple  42  and pump sealing rings  52  are preferably made from metal or other hard surfaces that are manufactured to provide an interference seal between pump seating nipple  42  when installed. As shown, pump seating nipple  42  defines a tapered seal seat that engages sealing rings  52  as electric submersible pump  10  is lowered toward the bottom of production tubing  22 . Sealing rings  52  are preferably designs such that they are compressible to provide the interference fit with pump seating nipple  42 . Sealing rings  52  preferably deform elastically to a small degree to ensure a proper engagement. It will be understood that the number of pump sealing rings  52  and their actual dimensions may vary depending on the preferences of the user, the materials used, and the circumstances under which electric submersible pump will be used. In some embodiments, pump sealing rings  52  may be manufactured into the body of thrust chamber  40 , which may be installed at the factory when electric submersible pump  10  is manufactured. Pump sealing rings  52  may also be manufactured as a separate component that is connected between thrust chamber  40  and pump section  44 . 
         [0019]    As depicted in  FIG. 4 , the top-most pump seal ring  52  is positioned immediately below outlet ports  50  to minimize the amount of debris that may accumulate between the seal and outlet ports  50 . If a seal were provided closer to inlet ports  48 , there would be a greater amount of space in which debris could accumulate, which would make it more difficult to disengaged and remove electric submersible pump  10  for servicing. 
         [0020]    Preferably, electric submersible pump  10  is installed using the passive seal provided by pump seating nipple  42  and pump sealing rings  52  as depicted such that a packer, such as a sealbore packer, or other active sealing element is not required. As a result of this design, it is preferred that the full weight of the submersible pump  10  will not be borne by pump seating nipple  42 , but that most or substantially all of the weight of electric submersible pump  10  will be supported by coiled tubing string  24 . During installation, electric submersible pump  10  will be lowered until it engages pump seating nipple  42 . The operator will be notified of this as a certain depth is reached and by monitoring the weight supported by coiled tubing injector  34 . Once sufficient weight to cause pump sealing rings  52  and pump seating nipple  42  has been applied to properly seal electric submersible pump  10 , the remaining weight will continue to be supported along coiled tubing string  24 . After properly engaged, and depending on the specifications of the various components, coiled tubing injector  34  may be backed off to support additional weight, while still allowing sufficient weight to maintain the seal between pump seating nipple  42  and pump sealing rings  52 . 
         [0021]    Referring to  FIGS. 2 and 3 , the motor oil delivery system comprises of a surface mounted pumping and control unit that maintains a very constant flow of oil through the stainless steel capillary tubing  5  of  FIG. 3  and into the motor section  38  and thrust chamber  40  of  FIG. 2  regardless of the pump discharge pressure. In this way, the internal pressure of the capillary tubing  5  of  FIG. 3  and the motor section  38  and thrust chamber  40  of  FIG. 2  is maintained at a pressure that is 10 psi to 50 psi higher than the bottom hole pressure at the pump discharge. This will ensure that no bottom hole fluids shall enter and contaminate the motor section  38  or thrust chamber  40 . 
         [0022]    In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements. 
         [0023]    The following claims are to be understood to include what is specifically illustrated and described above, what is conceptually equivalent, and what can be obviously substituted. Those skilled in the art will appreciate that various adaptations and modifications of the described embodiments can be configured without departing from the scope of the claims. The illustrated embodiments have been set forth only as examples and should not be taken as limiting the invention. It is to be understood that, within the scope of the following claims, the invention may be practiced other than as specifically illustrated and described.