Patent Publication Number: US-2020300068-A1

Title: Integration of in-well wetmate esp motor connector with high pressure hydraulic line

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 62/270,753, filed Dec. 22, 2015, which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The invention relates installation and operation of electrical submersible pumps (ESPs), and in particular to a permanent installation of an ESP. 
     BACKGROUND 
     A variety of fluid lifting systems pump fluids such as hydrocarbons from wellbores to surface holding and processing facilities. Commonly, one of a number of various types of downhole pumping systems pumps subterranean formation fluids from a particular wellbore to surface collection equipment for transport to processing locations. 
     One such system is a submersible pumping assembly that is supported immersed in production fluid within the wellbore. The submersible pumping assembly has a pump and a motor to drive the pump to pressurize and pass the production fluid through production tubing to a surface location. A typical electric submersible pump assembly (ESP) includes a submersible pump, an electric motor and a seal section interdisposed between the pump and the motor. The purpose of the seal section is to protect the motor from contamination as the production fluid usually contains deleterious substances such as particulate solids and other debris from the formation. Much research focuses on improved seal sections to prevent or at least reduce environmental contamination of the motor. Other efforts have involved development of motors that function even with contaminants present. Nonetheless, over time, ESPs still fail, most frequently from contamination. In some environments, such as deep-sea applications, the retrieval and remediation or replacement of an ESP is very expensive. 
     Thus, there is a need for manner of effectively preventing deleterious substances, such as particulate solids and other matter contained in formation fluids, from entering the motor where such contaminants can interfere with the efficient operation of the motor and can reduce the operational life of the motor. 
     SUMMARY 
     An apparatus includes a pump, a motor, a pressure intensifier, and a hydraulic fluid port. The motor is configured to drive the pump. The pressure intensifier is configured to maintain pressure of hydraulic fluid in the motor at a predetermined level. The hydraulic fluid port configured to provide hydraulic fluid to the pressure intensifier by mating with an external hydraulic fluid source when the apparatus is in a hydrocarbon producing wellbore. The apparatus is dimensioned for lowering and retrieving through the string of production tubing. 
     A method includes placing an apparatus in a subsea wellbore, and hydraulically connecting the apparatus with an external hydraulic fluid source. The apparatus of this method includes a pump, a motor, a pressure intensifier, and a hydraulic fluid port. The motor is configured to drive the pump. The pressure intensifier is configured to maintain pressure of the hydraulic fluid in the motor at a predetermined level. The hydraulic fluid port is configured to provide hydraulic fluid to the pressure intensifier by mating with the external hydraulic fluid source when the apparatus is in a hydrocarbon producing wellbore. The apparatus is dimensioned for lowering and retrieving through the string of production tubing. 
     Another method includes placing an apparatus in a subsea wellbore and hydraulically connecting the apparatus with an external hydraulic fluid source. Pressure of the external hydraulic fluid source acts to maintain pressure of hydraulic fluid in a motor of the apparatus at a predetermined level. The apparatus includes a pump, the motor, and a hydraulic fluid port. The motor is configured to drive the pump. The hydraulic fluid port is configured to provide hydraulic fluid by mating with the external hydraulic fluid source when the apparatus is in a hydrocarbon producing wellbore. The apparatus is dimensioned for lowering and retrieving through the string of production tubing. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a cross-sectional view of an apparatus, in accordance with the present disclosure, deployed in a wellbore. 
         FIG. 2  is a flowchart of a method of using the apparatus of  FIG. 1 , in accordance with the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an apparatus  101  (e.g., an ESP or other electric pump) installed in a hydrocarbon producing wellbore  102  (e.g., an onshore well, an offshore well, a deep sea well). Apparatus  101  may include a pump  103 , an optional seal  104 , and a motor  105  that drives the pump. Pressurized hydraulic fluid is present in the apparatus  101  for lubrication and cooling, as well as for preventing intrusion of production fluid  106  into the motor  105 . The hydraulic fluid may be mineral oil, glycol based, transformer oil, or other similar fluids. A motor housing (not shown), pressure, and the seal  104  may protect the motor  105  from the intrusion of damaging production fluid  106 . However, over time, the hydraulic fluid will begin to leak into the environment, due to wear, vibration, age, etc. The leakage rate is dependent on fluid properties, differential pressure, the transient operating conditions of the pump, and the tightness of the seal(s). 
     Traditionally, once enough hydraulic fluid has left the apparatus  101 , the pressure therein will drop to that of the production fluid  106 , allowing for intrusion of production fluid  106  into the motor  105 , eventually causing the apparatus  101  to fail. However, the presently disclosed design may maintain the pressure of the hydraulic fluid indefinitely by providing an external hydraulic fluid source  107  connected to the apparatus  101  via a hydraulic fluid conduit  108 . The external hydraulic fluid source  107  may be located on the host and connect via umbilical or the external hydraulic fluid source  107  may be located at the mud line. In this manner, even when the seal  104  fails and hydraulic fluid leaks, pressure can be maintained at a level sufficient to prevent the deleterious effects of production fluid  106  entering the motor  105 . 
     Thus hydraulic fluid flows to the apparatus  101  for distribution to the motor  105  and or the pump  103  for lubrication internal structures, such as pump rotor bearings, seals and timing gears. The pressure in the lubrication fluid circuit of the motor  105  and pump  103  may thus be maintained above the pressure of the production fluid displaced through the pump, in order to prevent intrusion of process fluid and particles into pump hearings, seals, and timing gears. 
     The mechanism for maintaining a predetermined level of pressure of hydraulic fluid in the motor  105  may include a pressure intensifier  109  such as is described in U.S. Pat. No. 9,097,267 or other similar device for providing a boost to the pressure in the motor  105 . However, in the present apparatus  101 , the pressure intensifier  109  may recharge without removing the apparatus  101  from the wellbore  102 . Instead, a hydraulic fluid port  110  may provide hydraulic fluid to the pressure intensifier  109  such that the pressure intensifier  109  can adequately maintain pressure of hydraulic fluid in the motor  105  at the predetermined level. 
     A string of casing  111  may be cemented to an inner surface of the wellbore  102 , and a string of production tubing  112  may be located within and generally coaxial with casing  111  to form an annulus  113  between casing  111  and production tubing  112 . A packer  114  (e.g., a swab cup) may be located at a lower end of production tubing  112  and may lie between casing  111  and production tubing  112  to prevent production flow or other fluids from entering annulus  113 . A check valve  115  in the lower portion of production tubing  112  may prevent fluid loss from fluid flowing downward. Check valve  115  may also allow for pressure-assisted removal of apparatus  101 . An additional swab cup, or other type of packer  116 , may be located between pump  103  and the inner surface of production tubing  112 . Packer  116  may be a lip seal and may be run with apparatus  101 . Packer  116  may allow upward flow while preventing downward flow therethrough. As apparatus  101  moves into place, packer  116  may slide on the interior of production tubing  112 , allowing displaced fluid to flow past packer  116 . 
     Apparatus  101  may be assembled by securing a lower end of pump  103  to an upper end of seal  104  and securing a lower end of seal  104  to an upper end of motor  105 . A running tool (not shown) may releasably engage a neck  117  on the upper end of pump  103 , such that production fluid  106  may flow out of neck  117 . The apparatus  101  may then move into the wellbore  102  with the running tool on a line (not shown), such as coiled tubing or cable, through production tubing  112  until the apparatus  101  and corresponding elements reach the desired depth. The running tool and coiled tubing may then be retrieved. Apparatus  101  may pass through an orienting sleeve  118  where it may rotate by engagement with a helical shoulder  119  that may assist in rotationally aligning apparatus  101  to the required orientation for positioning within a mating profile  120 . The running tool may have a swivel, or other bearing, to allow apparatus  101  to rotate during installation without rotating the coiled tubing. 
     One or more wet-mateable hydraulic fluid connectors  121  may provide hydraulic fluid to motor  105 . Hydraulic fluid connector  121  may affix to production tubing  112  and lie fully within annulus  113  or may slightly protrude within production tubing  112 . The hydraulic fluid connector  121  may connect to a hydraulic fluid conduit  108  that feeds hydraulic fluid from an external hydraulic fluid source  107  to hydraulic fluid connector  121 . Hydraulic fluid conduit  108  may extend alongside and be strapped to production tubing  112 . Hydraulic fluid conduit  108  may provide high-pressure (e.g., in the range of 15-45 psi higher than the wellbore pressure) hydraulic fluid to the apparatus  101 . Apparatus  101  may include a hydraulic fluid port  110  positioned for mating with hydraulic fluid connector  121 . In this illustration, outer hydraulic fluid connector  121  engages the hydraulic fluid port  110 . The wet-mateable hydraulic fluid connectors  121  may be analogous to the connections described in U.S. Pat. No. 8,381,820, although modifications would be necessary to adapt the technology described therein to provide hydraulic fluid to the intensifier  109  of the present disclosure. In addition to hydraulic connections, electrical connections may be provided via a connector and line configured for such purpose. For example, the hydraulic fluid connector  121  and the hydraulic fluid port  110  may also include electrical connections and the hydraulic fluid conduit  108  may run alongside an electrical cable. 
     Referring now to  FIG. 2 , a method of using the apparatus  101  described above may include various steps. At step  201 , the apparatus  101  may be placed in the wellbore  102 . Next, at step  202 , the apparatus  101  may be hydraulically connected to the external hydraulic fluid source  107 . Alternatively, hydraulically connecting the apparatus  101  with the external hydraulic fluid source  107  may occur prior to placing the apparatus  101  in the wellbore  102 . In either event, the step of hydraulically connecting may be accomplished via the hydraulic fluid connector  121 . At step  203 , the method may further include maintaining pressure of the hydraulic fluid in the motor  105  at a predetermined level via the pressure intensifier  109 . This may involve actively measuring and making adjustments or alternatively passive means such as a pressure limit valve. In either event, over time, the pressure intensifier  109  loses pressure without introduction of additional pressure andior hydraulic fluid. Therefore, at step  204 , it is determined whether the pressure in the pressure intensifier  109  has dropped below an intensifier pressure level or that the level in the intensifier  109  is low. Again, this may involve either active or passive methodology. In any event, at step  205 , hydraulic fluid is provided to the pressure intensifier  109  via the hydraulic fluid port  110 , which is fed from the external hydraulic fluid source  107 . In addition to the above steps, the external hydraulic fluid source  107  may be used to flush the motor  105 , clearing any debris that may have entered, despite precautionary measures having been taken. Similarly, the external hydraulic fluid source  107  may be used to flush the wat-mateable connection during mate-up. Alternatively, the external hydraulic fluid source  107  may be used to flush the motor  105  without performing most of the steps noted above. For example, once the apparatus is placed at step  201  and hydraulically connected at step  202 , the remaining steps may be omitted and only flushing may occur. Alternatively, flushing may occur in conjunction with the connecting step  202 , to flush fluids during makeup of the connection. 
     In another example, the external hydraulic fluid pressure may act directly and the pressure intensifier  109  may not be required. In such instance, the method may be as described above but without the inclusion of the pressure intensifier and the addition of pressure of the external fluid source acting to maintain pressure of hydraulic fluid in the motor at a predetermined level. 
     The advantages of using the present invention may include a permanently deployed source of high-pressure hydraulic fluid replenishment. By permanently deploying a source of high-pressure hydraulic fluid, the cost and difficulty of removing the pump assembly to remediate wear caused by insufficient hydraulic fluid may be mitigated.