Abstract:
A downhole separator has a housing defining an interior cavity divided into a first chamber and a second chamber by a flow restricting bearing housing. A shaft driven impeller pumps production fluid into the first chamber and to the bearing housing. The bearing housing generates a pressure drop in production fluid entering the second chamber, separating gas from liquid. A vortex generator in the second chamber segregates the liquid to the outside and the gas to the inside of the second chamber. A downhole separation method includes pumping production fluid into a first chamber, and generating a pressure drop in the fluid as the fluid enters a second chamber to separate gas and liquid.

Description:
TECHNICAL FIELD 
     The present invention relates to separators for oil and gas wells, and more particularly to a rotary, downhole, gas and liquid separator and a downhole method of separating gas and liquid from production fluid. 
     BACKGROUND ART 
     Liquids are substantially incompressible fluids while gases are compressible fluids. The production fluid in an oil or gas well is generally a combination of liquids and gases. In particular, the production fluid for methane production from coal formation includes the gas and water. Pumping such production fluid is difficult due to the compressibility of the gas. Compression of the gas reduces the efficiency of the pump and the pump can cavitate, stopping fluid flow. Downhole gas and liquid separators separate the gas and liquid in the production fluid at the bottom of the production string, before pumping the liquid up the production string, and thereby improve the efficiency and reliability of the pumping process. In some cases, the waste fluids from the production fluid may be reinjected above or below the production formation, eliminating the cost of bringing such waste fluids to the surface and the cost of disposal or recycling. 
     U.S. Pat. No. 5,673,752 to Scudder et al. discloses a separator that uses a hydrophobic membrane for separation. U.S. Pat. No. 6,036,749 to Ribeiro et al., U.S. Pat. No. 6,066,193 to Lee and U.S. Pat. No. 6,382,317 to Cobb disclose powered rotary separators. U.S. Pat. No. 6,155,345 to Lee et al. discloses a separator divided by flow-through bearings into multiple separation chambers. 
     DISCLOSURE OF THE INVENTION 
     A downhole separator includes a housing defining an interior cavity, a means for restricting fluid flow, an internal pump and a vortex generator. The means for restricting fluid flow is located in the housing and divides the interior cavity into a first chamber and a second chamber. The internal pump pumps production fluid into the first chamber and through the means for restricting flow. The means for restricting flow generates a pressure drop in production fluid entering the second chamber, causing the gas and liquid to separate. The vortex generator segregates the liquid to the outside and gas to the inside of the second chamber. The method of separating liquid and gas from production fluid includes pumping production fluid into a first chamber, generating a pressure drop in the production fluid as the production fluid flows from the first chamber into a second chamber, and generating a vortex in the production fluid in the second chamber. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Details of this invention are described in connection with the accompanying drawings that bear similar reference numerals in which: 
     FIG. 1 is a side elevation view of a separator embodying features of the present invention. 
     FIG. 2 is a side cut away view of the separator of FIG.  1 . 
     FIG. 3 is a partially cut away view of the head of the separator of FIG.  1 . 
     FIG. 4 is a partially cut away view of the lower diffuser of the separator of FIG.  1 . 
     FIG. 5 is a partially cut away view of the upper diffuser of the separator of FIG.  1 . 
     FIG. 6 is a partially cut away view of the bearing housing of the separator of FIG.  1 . 
     FIG. 7 is a partially cut away view of the impeller of the separator of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to FIGS. 1 and 2, a separator  10  embodying features of the present invention includes a housing  11 , a base  12 , and a head  14 . The housing  11  is a hollow, elongated, cylinder defining an interior cavity  15 . The separator housing  11  has spaced, internally threaded lower and upper ends  17  and  18 . 
     Describing the specific embodiments herein chosen for illustrating the invention, certain terminology is used which will be recognized as being employed for convenience and having no limiting significance. For example, the terms “top”, “bottom”, “up” and “down” will refer to the illustrated embodiment in its normal position of use. “Inward” and “outward” refer to radially inward and radially outward, respectively, relative to the axis of the illustrated embodiment of the device. Further, all of the terminology above-defined includes derivatives of the word specifically mentioned and words of similar import. 
     The base  12  has an upper portion  20 , an intermediate portion  21  and a lower portion  22 . The upper portion  20  is an externally threaded, hollow, cylinder sized and shaped to thread into the lower end  17  of separator housing  11 , and includes an upwardly opening, centered, generally cylindrical upper cavity  24 . The intermediate portion  21  has an exterior surface  25  that, in the illustrated embodiment, extends downwardly and inwardly from the upper portion  20  and has a centered lower bearing aperture  26  extending downward from the upper cavity  24 . A lower bearing  28  is mounted in the lower bearing aperture  26 . A plurality of circumferentially arranged inlet ports  27  extend from the exterior surface  25  upwardly and inwardly into the upper cavity  24 . The lower portion  22  is hollow and generally cylindrical, and extends downward from the intermediate portion  21  to an outwardly projecting flange  29 , with a lower cavity  30  extending from the lower bearing aperture  26 . 
     Referring to FIG. 3, the head  14  includes an upper portion  34 , an intermediate portion  35  extending downward from the upper portion  34 , and a lower portion  36  extending downward from the intermediate portion  35 . The upper portion  34  is generally cylindrical and includes a plurality of spaced, radially arranged, upwardly extending, threaded studs  38 . An external, circumferential channel  39  extends around the head  14  between the upper portion  34  and the intermediate portion  35 . The intermediate portion  35  is externally threaded, and sized and shaped to thread into the upper end  18  of the separator housing  11 . An upwardly opening, inwardly and downwardly tapering, generally conical upper cavity  40  extends through the upper portion  34  and the intermediate portion  35 . 
     The lower portion  36  has a downwardly and inwardly tapering exterior surface  41 , and a downwardly opening, downwardly and outwardly tapering lower cavity  42  that connects to the exterior surface  41  at a lower end  43 . An upper bearing aperture  44  extends between the upper cavity  40  and the lower cavity  43 , and has an upper bearing  45  mounted therein. A plurality of circumferentially arranged liquid outlet ports  47  extend upwardly and inwardly from the exterior surface  41  to the upper cavity  40 . A plurality of circumferentially arranged gas outlet ports  48  extend upwardly and outwardly from the lower cavity  42  to the channel  39 . 
     Referring again to FIG. 2, the separator  10  includes a lower diffuser  50 , an upper diffuser  51 , a first sleeve  52 , a means for restricting flow  53 , a second sleeve  55  and a third sleeve  56 , with each having a cylindrical exterior sized and shaped to fit into the interior cavity  15  of the separator housing  11 , and with each being assembled into the interior cavity  15  in the above listed order from the base  12  to the head  14 . In the illustrated embodiment the means for restricting fluid flow  53  is a bearing housing  54 . Other means for restricting fluid flow  53  are suitable for the present invention. 
     As shown in FIG. 4, the lower diffuser  50  is substantially cup shaped with a generally flat round bottom  58 , an outer wall  59  extending upward from the periphery of the bottom  58 , and a lower diffuser aperture  60  extending through the center of the bottom  58 . Referring to FIG. 5, the upper diffuser  51  includes an upper diffuser aperture  62  extending upwardly through the center of upper diffuser  51 , a cylindrical outer wall  63 , and a plurality of spaced, radially arranged, upwardly, inwardly and helically extending passages  64  between upper diffuser aperture  62  and the outer wall  63 , with passages  64  being separated by radial fins  65 . The outer wall  59  of the lower diffuser  50  extends upwardly and the outer wall  63  of the upper diffuser  51  extends downwardly to space the lower and upper diffusers  51  and  52  apart to define an impeller cavity  67  therebetween. 
     The bearing housing  54 , as shown in FIG. 6, is generally cylindrical with an intermediate bearing aperture  68  and a plurality of spaced, radially arranged passages  69  extending through the bearing housing  54 . An intermediate bearing  70  is mounted in the intermediate bearing aperture  68 . Passages  69  are configured to restrict fluid flow so that bearing housing  54  divides the interior cavity  15  into a first chamber  71  and a second chamber  72 . In the illustrated embodiment the passages  69  extend upwardly, inwardly and helically, so that the passages  69  initiate vortex generation in the production fluid as the production fluid flows into the second chamber  72 . Referring back to FIG. 2, the first, second and third sleeves  53 ,  55  and  56  are each relatively thin walled hollow cylinders. The first sleeve  52  spaces the bearing housing  54  from the upper diffuser  51 . The second and third sleeves  55  and  56  together space the bearing housing  54  from the head  14 . 
     An elongated cylindrical shaft  74  extends through the interior cavity  15  with a splined lower end  75  extending into the lower cavity  30  of the base  12  and a spaced, splined upper end  76  extending into the upper cavity  40  of the head  14 . Lower, intermediate and upper bearing journals  77 ,  78  and  79  are sized and spaced along the shaft  74  to fit the lower, intermediate and upper bearings  28 ,  70  and  45 , respectively. A keyway  80  extends longitudinally along shaft  74  with a key  81  mounted therein. An internal pump  82  mounts on the shaft  74 . Internal pump  82  is shown in the illustrated embodiment in FIG. 7 as impeller  83 , in the impeller cavity  67 , having a hub  84  on shaft  74  secured by key  81  and a plurality of spaced, radially arranged, upwardly, outwardly and helically extending passages  85  around the hub  84 . Other styles of internal pump  82 , such as an auger pump, are suitable. A vortex generator  86  is shown in FIG. 2 as a paddle assembly  87  positioned in the second chamber  72  and having a hub  88  on shaft  74  secured by key  81  and a plurality of spaced vertical paddles  89  that extend radially from the hub  88 . Other styles of vortex generator, such as spiral or propeller, are also suitable. 
     In a typical installation of the separator  10  mounts between a motor on the flange  29  of the base  12  and a well pump secured to the head  14  by the studs  38 . The impeller  83  pulls production fluid into the first chamber  71  of the separator  10  through the inlet ports  27  and lower diffuser  50  and pumps the production fluid into the upper diffuser  51 . The upper diffuser  51  directs production fluid up to the bearing housing  54 . 
     The passages  69  restrict the flow of production fluid through the bearing housing  54  between the first and second chambers  71  and  72 , generating a pressure drop and rapid expansion of the production fluid enter the second chamber  72 . The rapid expansion of the production fluid causes gas in the production fluid to expand and separate from liquid in the production fluid. From the bearing housing  54  the liquid and gas travel upward to the vortex generator  87 . The paddles  89  push the liquid and gas in a circular direction and thereby centrifugally segregate the liquid at the outside and the gas at the inside of the second chamber  72 . The liquid passes upwardly to the liquid outlet ports  47  and into the well pump. Gas passes upwardly to the gas outlet ports  48  and out of the separator  10  at the channel  39 . 
     A method of separating gas and liquid from production fluid in a well, embodying features of the present invention, includes providing connected first and second chambers, pumping production fluid into the first chamber, generating a pressure drop in the production fluid as the fluid passes between the first and second chamber, and generating a vortex in the second chamber. More particularly, the first step of the method includes providing connected first and second chambers, a bearing housing between the first and second chambers, a rotary paddle in the second chamber, and gas outlet ports and liquid outlet ports connected to the second chamber, with the bearing housing having a plurality of restrictive passages extending helically between the first and second chambers. The next step includes pumping the production fluid into the first chamber. The next step includes passing said the production fluid through the passages to generate a pressure drop in said production fluid as the production fluid flows into the second chamber to separate the gas and the liquid. Passing the production fluid through the passages also imparts a helical flow to the production fluid and thereby initiates generation of a vortex. The next step includes rotating the paddle to continue vortex generation to further separate the gas and the liquid. The gas is then diverted out of the second chamber through the gas outlet ports, and the liquid is diverted out of the second chamber through the liquid outlet ports. 
     Although the present invention has been described with a certain degree of particularity, it is understood that the present disclosure has been made by way of example and that changes in details of structure may be made without departing from the spirit thereof.