Abstract:
A jet pumping system for use in a wellbore drilled for the production or petroleum products includes a packer disposed within the wellbore, an intake pipe extending through the packer, an injection system configured to inject pressurized gas into the wellbore and a jet pump connected to the intake pipe. The jet pump further includes a removable vortex generator. A method for selectively generating foam in-situ in a subterranean well includes the steps of installing a vortex generator in the jet pump with a wire line procedure and pumping a foam generating solution into the jet pump. Pressurized gas is injected into the annulus of the well, which creates a vortex in the jet pump as the pressurized gas is directed into the jet pump through injection ports. The resultant vortex aerates and mixes the foam generating solution and petroleum fluids to generate a foam in the jet pump.

Description:
RELATED APPLICATIONS 
     The present application claims the benefit of U.S. Provisional Patent Application No. 61/068,047, entitled “Foam Generator,” filed Mar. 3, 2008, the disclosure of which is herein incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to the field of gas lift and foam lift methodologies of fluid recovery in oil and gas wells and more particularly to an apparatus and method for improving the recovery of petroleum products from a subterranean well. 
     BACKGROUND OF THE INVENTION 
     Wells are drilled to extract oil and gas from subterranean reservoirs. Oil and gas typically enter the well from the producing reservoir through perforations in the well casing. Initially, the reservoir pressure may be sufficient to overcome the force of gravity and force oil and gas out of the well. As the reservoir pressure decreases, however, fluids may accumulate at the bottom of the wellbore and it may become necessary to employ artificial lift systems to harvest the oil and gas. Examples of artificial lift systems include surface-mounted sucker rod pumps, electrical submersible pumps, plunger-lifts and gas-lift systems. 
     Gas lift systems involve injecting gas through the tubing-casing annulus of the well to aerate the accumulated fluid at the bottom of the well. The injected gas aerates the fluid to reduce its density and the reservoir pressure is then able to lift the oil column and forces the fluid out of the wellbore. Gas may be injected continuously or intermittently, depending on the producing characteristics of the well and the arrangement of the gas-lift equipment. 
     Generally, the use of density-reducing foam in conjunction with gas lift systems has proven to be an efficient and cost effective method for improving the recovery of petroleum products from the wellbore. However, many current foam generators require that the foam be generated at the surface and then pumped down into the wellbore. Alternatively, foam generation equipment must be installed in the equipment string in the well, which requires shutting-in the well while the new equipment is installed and removed. There is therefore a need for an improved foam generator that can generate foam in-situ in the well-bore and that can be selectively activated without interrupting the production of oil and gas. 
     SUMMARY OF THE INVENTION 
     In a preferred embodiment, the present invention provides a jet pumping system for use in a wellbore drilled for the production or petroleum products. The jet pumping system includes a packer disposed within the wellbore, an intake pipe extending through the packer, an injection system configured to inject pressurized gas into the wellbore and a jet pump connected to the intake pipe. The jet pump further includes a removable vortex generator. 
     In another aspect, the present invention includes a method of selectively generating foam in-situ in a subterranean well. In a preferred embodiment, the method includes the steps of providing a jet pump in the subterranean well, installing a vortex generator in the jet pump with a wire line procedure and pumping a foam generating solution into the jet pump. The foam is generated by injecting pressurized gas into the annulus of the well with a gas injection system, which creates a vortex in the jet pump as the pressurized gas is conducted into the jet pump through injection ports. The resultant vortex in the jet pump aerates and mixes the foam generating solution and petroleum fluids to generate a foam in the jet pump. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1 . is a side view of a jet pump system deployed in a wellbore. 
         FIG. 2 . is a side view of a jet pump constructed in accordance with a preferred embodiment of the present invention. 
         FIG. 3 . is a side cross-sectional view of the jet pump of  FIG. 2  with the vortex generator removed. 
         FIG. 4 . is a cross-sectional view of the jet pump of  FIG. 3 , illustrating the angular disposition of the intake ports. 
         FIG. 5 . is a perspective view of the vortex generator and locking collar of the jet pump of  FIG. 2 . 
         FIG. 6 . is a partial cross-sectional perspective view of the jet pump of  FIG. 2  with the vortex generator installed. 
         FIG. 7 . is a partial cross-sectional view of the jet pump of  FIG. 6  with the vortex generator installed. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In accordance with a preferred embodiment of the present invention,  FIG. 1  shows an elevational view of a jet pumping system  100  attached to production tubing  102 . The jet pumping system  100  and production tubing  102  are disposed in a wellbore  104 , which is drilled for the production of a fluid such as water or petroleum. As used herein, the term “petroleum” refers broadly to all mineral hydrocarbons, such as crude oil, gas and combinations of oil and gas. The production tubing  102  connects the jet pumping system  100  to a wellhead  106  located on a surface  108 . The surface  108  may be the ground, a vehicle, a drilling rig or an offshore production platform. Petroleum products enter the wellbore  104  from a producing formation through perforations  110 . Although the pumping system  100  is primarily designed to pump petroleum products, it will be understood that the present invention can also be used to move other fluids. 
     The jet pumping system  100  generally includes a packer  112 , an intake pipe  114 , an injection system  116  and a jet pump  118 . The packer  112 , jet pump  118  and intake pipe  114  are preferably installed below the top of the fluid level in the wellbore  104 . The packer  112  is installed in the annulus of the wellbore  104  and substantially isolates the jet pump  118  from the intake pipe  114 . The injection system  116  generally includes a compressor and associated equipment and is configured to force air, produced hydrocarbon gas or other gas into the annulus of the wellbore  104 . It will be appreciated by those of ordinary skill in the art that the injection system  116  may recycle some or all of the gas petroleum products recovered from the wellbore  104 . Unless otherwise noted, all of the components of the jet pumping system  100  are constructed from steel, stainless steel or other metal suitable for use in a downhole environment. 
     The packer  112  prevents the injected gas from entering the jet pumping system  100  through the intake pipe  114  and from exiting the wellbore  104  through the perforations  110 . In this way, the packer  112  forces the injected gas to enter the jet pumping system  100  through the jet pump  118 . The intake pipe  114  extends through the packer  112  and provides a path for fluids to travel from the bottom of the wellbore  104  into the jet pumping system  100 . It will be understood by those skilled in the art that the jet pumping system  100  may include additional components to facilitate the recovery of petroleum products from the wellbore  104 . 
     Turning to  FIGS. 2 and 3 , shown therein are elevational and cross-sectional views, respectively, of the jet pump  118 . The jet pump  118  preferably includes a main body  120 , an intake  122 , a discharge  124  and a plurality of injection ports  126 . In the preferred embodiment, the main body  100  is substantially cylindrical in shape. The intake  122  is tapered and externally threaded for connection with the intake pipe  114 . The discharge  124  is internally tapered and threaded for connection with the production tubing  102 . It will be understood by those skilled in the art that there are alternative ways to connect the jet pump  118  to the production tubing  102  and intake pipe  114 . 
     The main body  120  includes an exterior surface  128 , an interior surface  130 , a central passage  132  that longitudinally extends along the length of the jet pump  118  and a locking slot  134 . The locking slot  134  is positioned below the plurality of injection vents  126  and is recessed into the interior surface  130  of the jet pump  118 . Injection ports  126  extend through the main body  120  from the exterior surface  128  to the interior surface  130 . The injection ports  126  place the central passage  132  in fluid communication with the wellbore  104  surrounding the jet pump  118 . In the presently preferred embodiment, the jet pump  118  includes six injection ports  126 . It will be appreciated, however, that fewer or more injection ports  126  may also be used with the jet pump  118 . 
     As shown in the cross-sectional view of  FIG. 3 , the injection ports  126  are disposed at a non-horizontal angle and upward direction through the main body  120 . As shown in the cross-sectional representation of  FIG. 4 , the injection ports  126  are also radially distributed around the main body  120  in an equally offset, tangential fashion that increases the length of the injection port  126 . The elevated, angular disposition of the injections ports  126  promotes an upward, rotating flow profile within the central passage  132  of the jet pump  118 . 
     Turning to  FIG. 5 , shown therein is a perspective view of a vortex generator  136  and locking collar  138 . The vortex generator  136  includes a tube body  140  and a plurality of locking tines  142 . The tube body  140  is preferably configured as a hollow cylinder configured with an outer diameter that is slightly less than the diameter of the interior surface  130  of the main body  120 . Each of the plurality of locking tines  142  includes a locking flange  144 . Each locking flange  144  extends outward from the locking tine  142 . The locking flanges  144  are sized and configured to be received by the locking slot  134  in the main body  120 . 
     The locking collar  138  is a generally formed as a cylindrical ring that is configured to slide over the tube body  140  into a position adjacent the locking tines  142 . Alternatively, the locking collar  138  can be configured as a split-ring or “c-clamp.” The locking collar  138  prevents excessive vibration of the tube body  140  during operation of the jet pump  118 . 
     Turning to  FIGS. 6 and 7 , shown therein are perspective and elevational views in cross-section of the assembled jet pump  118 . The vortex generator  136  is installed within the central passage  132  of the main body  120 . During installation, the locking tines  142  deform slightly as the locking flanges  144  pass through the central passage  132 . When the locking flanges  144  reach the locking slot  134 , the locking flanges  144  expand outward to hold the vortex generator  136  in a stationary position within the jet pump  118 . The locking collar  138  can then be placed over the tube body  140  to dampen the vibration of the vortex generator  136 . 
     Significantly, installation of the vortex generator  136  creates an annular space  146  (see  FIG. 7 ) between the interior surface  130  and the tube body  140 . The confined geometry of the annular space  146  causes gases injected through the injection ports  126  to accelerate as they enter the central passage  132 . The acceleration of the injected gases increases turbulence within the central passage  132  and the formation of a vortex flow profile  148  near the discharge  124  of the jet pump  118 . The acceleration of the injected gases around the vortex generator  136  also creates a pressure drop that aids in the movement of petroleum products through the jet pump  118 . 
     The vortex generator  136  can be removed from the jet pump  118  without shutting in the well or removing the jet pump  118 . A vortex generator removal tool (not shown) is lowered into the jet pump  118  with a wire line. The vortex generator removal tool engages the locking tines  142  and compresses them inward so that the locking flanges  144  disengage from the locking slot  134 . Once the locking flanges  144  are disengaged from the locking slot  134 , the vortex generator  136  may be pulled back up the jet pump  118  and production tubing  102 . Removing the vortex generator  136  from the main body  120  of the jet pump  118  likewise removes the annular space  146 . Without the annular space  146 , gases and fluids flowing through the injection ports  126  will not experience an increase in velocity as they enter the central passage. 
     In a preferred method of operation, a foam generating solution is injected into the production tubing  102 . The foam generating solution mixes with the fluids near the jet pump  118 . After the foam generating solution has been added to the jet pumping system  100 , pressurized gas is injected into the wellbore  104  with the injection system  116 . The pressurized gas travels down the annulus of the wellbore  104  to the vicinity of the packer  112  and enters the plurality of injection ports  126  in the jet pump  118 . If a column of liquid is present in the annulus above the packer  112 , the column of liquid may also be pushed through the injection ports  126  into the jet pump  118 . 
     The angular and radial orientation of the injection ports  126  causes the pressurized injection gases to assume an upward rotational flow profile in the central passage  132 , as depicted by flow arrows  148  in  FIG. 7 . Additionally, the restricted flow path provided by the annular space  146  increases the velocity (both vertical velocity and rotational velocity) of the injected fluids due to the Venturi effect. As the pressurized gases travel upward through the annular space  146 , they obtain a uniform rotation such that when the pressurized gas passes from the annular space  146  into the discharge  124  of the jet pump  118 , the pressurized fluids assume the characteristics of a vortex. 
     The vortex agitates and mixes the injected gases with fluids present in the jet pump  118 . In the presence of foam generating solution, the agitation and mixing created by the vortex in the jet pump  118  creates a highly aerated, low-density foam consisting of petroleum products, injection gas and foam generating solution. The vortex significantly improves the effectiveness of the foam generating solution. As the vortex generator  136  creates foam within the jet pump  118 , the foam rises upward through the production tubing  102  to the wellhead  106  and surface-mounted separation, refining and storage facilities. 
     It will be appreciated that the present invention may find utility without the use of a foam generating solution. For example, the agitation and aeration provided by the vortex generator  136  may improve the recovery of petroleum products from the wellbore  104  without the addition of a foam generating solution. 
     It is to be understood that even though numerous characteristics and advantages of various embodiments of the present invention have been set forth in the foregoing description, together with details of the structure and functions of various embodiments of the invention, this disclosure is illustrative only, and changes may be made in detail, especially in matters of structure and arrangement of parts within the principles of the present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. It will be appreciated by those skilled in the art that the teachings of the present invention can be applied to other systems without departing from the scope and spirit of the present invention.