Patent Publication Number: US-2011073305-A1

Title: Multisection Downhole Separator and Method

Description:
This application is a continuation-in-part of Ser. No. 12/567,933 filed Sep. 28, 2009. 
    
    
     TECHNICAL FIELD 
     The present invention relates to separators for oil and gas wells, and more particularly to a multisection, 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., and U.S. Pat. No. 6,382,317 to Cobb disclose powered rotary separators. U.S. Pat. No. 6,066,193 to Lee discloses a separation system having at least two separators with different internal diameters to provide different fluid capacities. 
     U.S. Pat. No. 6,155,345 to Lee et al. discloses a separator divided by flow-through bearings into multiple separation chambers. U.S. Pat. No. 6,761,215 to Morrison et al. discloses a rotary separator with a restrictor that creates a pressure drop. U.S. Pat. No. 7,461,692 to Wang discloses a separator having multiple separation stages with each separation stage having a rotor and each rotor having an inducer and an impeller. 
     DISCLOSURE OF THE INVENTION 
     A downhole separator includes at least two separation sections. Each of the separation sections has 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 means for restricting fluid flow limits the fluid flow into the second chamber which releases the pressure on the gas, allowing the gas bubbles to expand and separate from the liquid. The vortex generator segregates the liquid to the outside and gas to the inside of the second chamber. The number of separation sections, and the size of the means for restricting for each separation section are selected based on the required pumping rate of the well and the gas content of the production fluid entering each separation stage. The capacity of the means for restricting in each separation section controls the capacity of that separation section. Upstream separation sections have higher capacity due to the higher gas content and therefore the higher mass being pumped through the separation section. 
    
    
     
       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 first separation section of the separator of  FIG. 1 . 
         FIG. 3  is a partially cut away view of the head of a separation section of the separator of  FIG. 1 . 
         FIG. 4  is a partially cut away view of a diffuser of a pumping stage of a separation section of the separator of  FIG. 1 . 
         FIG. 5  is a partially cut away view of an impeller of a pumping stage of a separation section of the separator of  FIG. 1 . 
         FIG. 6  is a partially cut away view of the bearing housing a separation section of the separator of  FIG. 1 . 
         FIG. 7  is a side cut away view of the second separation section of the separator of  FIG. 1 . 
         FIG. 8  is a side cut away view of the first separation section of the separator of  FIG. 1  with an alternative internal pump and vortex generator. 
         FIG. 9  is a side cut away view of the second separation section of the separator of  FIG. 1  with an alternative internal pump and vortex generator. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to  FIGS. 1 and 2 , a separator  10  embodying features of the present invention includes a lower, upstream first separation section  11  and an downstream second separation section  12 . The first separation section  11  includes a housing  14 , a base  15 , and a head  16 . The housing  14  is a hollow, elongated, cylinder defining an interior cavity  17 . The housing  14  has spaced, internally threaded lower and upper ends  19  and  20 . 
     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. “Upstream” and “downstream” refer to normal direction of fluid flow during operation. Further, all of the terminology above-defined includes derivatives of the word specifically mentioned and words of similar import. 
     The base  15  has an upper portion  22 , an intermediate portion  23  and a lower portion  24 . The upper portion  22  is an externally threaded, hollow, cylinder sized and shaped to thread into the lower end  19  of housing  14 , and includes an upwardly opening, centered, generally cylindrical upper cavity  26 . The intermediate portion  23  has an exterior surface  27  that, in the illustrated embodiment, extends downwardly and inwardly from the upper portion  22  and has a centered lower bearing aperture  28  extending downward from the upper cavity  26 . A lower bearing  30  is mounted in the lower bearing aperture  26 . A plurality of circumferentially arranged inlet ports  29  extend from the exterior surface  27  upwardly and inwardly into the upper cavity  26 . The lower portion  24  is hollow and generally cylindrical, and extends downward from the intermediate portion  23  to an outwardly projecting flange  31 , with a lower cavity  32  extending from the lower bearing aperture  28 . 
     Referring to  FIG. 3 , the head  16  includes an upper portion  34 , an intermediate portion  35  extending downwardly from the upper portion  34 , and a lower portion  36  extending downwardly 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  16  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  20  of the housing  14 . 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 first separation section  11  includes an internal pump  50  with first and second pumping stages  51  and  52 , a first sleeve  53 , a means for restricting flow  54 , and a second sleeve  56 , with each having a cylindrical exterior sized and shaped to fit into the interior cavity  17  of the housing  14 , and with each being assembled into the interior cavity  17  in the above listed order from the base  15  to the head  16 . In the illustrated embodiment the means for restricting fluid flow  54  is a bearing housing  55 . Other means for restricting fluid flow  54  are suitable for the present invention. 
     The first and second pumping stages  51  and  52  each include an impeller housing  58  and a diffuser  59  sized and shaped to fit into the interior cavity  17  of the housing  14 , and an impeller  60 . As shown in  FIG. 4 , the diffuser  59  includes a diffuser aperture  62  extending upwardly through the center of diffuser  59 , a cylindrical outer wall  63 , and a plurality of spaced, radially arranged, upwardly, inwardly and helically extending passages  64  between the diffuser aperture  62  and the outer wall  63 , with the passages  64  being separated by radial fins  65 . Referring again to  FIG. 2 , the impeller housing  58  and diffuser  59  define an impeller cavity  67 .  FIG. 5  shows the impeller  60  having a hub  69  and a plurality of spaced, radially arranged, upwardly, outwardly and helically extending passages  70  around the hub  69 . 
     The bearing housing  55 , as shown in  FIG. 6 , is generally cylindrical with an intermediate bearing aperture  72  and a plurality of spaced, radially arranged passages  73  extending through the bearing housing  55 . An intermediate bearing  74  is mounted in the intermediate bearing aperture  72 . Passages  73  are configured to restrict fluid flow so that bearing housing  55  divides the interior cavity  17  into an upstream, first chamber  75  and a downstream, second chamber  76 . In the illustrated embodiment the passages  73  extend upwardly, inwardly and helically, so that the passages  73  initiate vortex generation in the production fluid as the production fluid flows into the second chamber  76 . 
     By way of example, and not as a limitation, the bearing housing  55  can be a bearing housing that would normally be used to stabilize a long shaft in a well pump. Such bearing housings are available in different capacities to compliment the capacity of the well pump. The bearing housing  55  has a selected capacity that is less than the capacity of the first and second stages  51  and  52 , to provide pressure build-up in the first chamber  75 , to limit fluid flow into the second chamber  76 , and to generate a pressure drop in fluid entering the second chamber  76 . Referring back to  FIG. 2 , the first and second third sleeves  53  and  56  are each relatively thin walled hollow cylinders. The first sleeve  53  spaces the bearing housing  55  from the pump  50 . The second sleeve  56  spaces the bearing housing  55  from the head  16 . 
     An elongated cylindrical shaft  78  extends through the interior cavity  17  with a splined lower end  79  extending into the lower cavity  32  of the base  15  and a spaced, splined upper end  80  extending into the upper cavity  40  of the head  16 . Lower, intermediate and upper bearing journals  81 ,  82  and  83  are sized and spaced along the shaft  78  to fit the lower, intermediate and upper bearings  30 ,  74  and  45 , respectively. A keyway  84  extends longitudinally along shaft  78  with a key  85  mounted therein. The impellers  60  mount on the shaft  78  with the hub  69  secured on shaft  78  by key  85 . A vortex generator  87  is shown in  FIG. 2  as a paddle assembly  88  positioned in the second chamber  76  and having a hub  89  on shaft  78  secured by key  85  and a plurality of spaced vertical paddles  90  that extend radially from the hub  89 . Other styles of vortex generator, such as spiral or propeller, are also suitable. The second chamber  76  is elongated, and the vortex generator  87  is positioned near the bearing housing  55  and spaced from the head  16  to allow more time for gas to separate from the liquid in the production fluid. 
     Referring to  FIG. 7 , the second separation section  12  includes a housing  92 , a base  93 , and a head  94 . The housing  92  and the head  94  are the same shape and configuration as the housing  14  and the head  16  of the first separation section  11 , with the housing  92  defining an interior cavity  95 . The housing  92  has spaced, internally threaded lower and upper ends  96  and  97 . The head  94  has an upper bearing  98 . 
     The base  93  has an upper portion  99 , an intermediate portion  100  and a lower portion  101 . The upper portion  99  is an externally threaded, hollow, cylinder sized and shaped to thread into the lower end  96  of housing  92 , and includes an upwardly opening, centered, generally cylindrical upper cavity  103 . The intermediate portion  100  has an exterior surface  104  that, in the illustrated embodiment, extends downwardly and inwardly from the upper portion  99  and has a centered lower bearing aperture  105  extending downward from the upper cavity  103 . A lower bearing  106  is mounted in the lower bearing aperture  105 . The lower portion  101  is hollow and generally cylindrical, and extends downward from the intermediate portion  100  to an outwardly projecting flange  107 , with a lower cavity  108  extending from the lower bearing aperture  105 . A plurality of circumferentially arranged inlet ports  109  extend from the lower cavity  108  upwardly into the upper cavity  103 . 
     The second separation section  12  includes an internal pump  112  with first and second pumping stages  113  and  114 , a first sleeve  115 , a means for restricting flow  116 , and a second sleeve  118 , with each having a cylindrical exterior sized and shaped to fit into the interior cavity  95  of the housing  92 , and with each being assembled into the interior cavity  95  in the above listed order from the base  93  to the head  94 . In the illustrated embodiment the means for restricting fluid flow  116  is a bearing housing  117 . Other means for restricting fluid flow  116  are suitable for the present invention. 
     The first and second pumping stages  113  and  114  are the same in configuration as the first and second pumping stages  51  and  52  of the first separation section  11 , with each having an impeller housing  120  and a diffuser  121  sized and shaped to fit into the interior cavity  95  of the housing  92 , and an impeller  122 . The bearing housing  117  supports an intermediate bearing  124 , and divides the interior cavity  95  into an upstream, first chamber  125  and a downstream, second chamber  126 . 
     By way of example, and not as a limitation, the bearing housing  117  can be a bearing housing that would normally be used to stabilize a long shaft in a well pump. Such bearing housings are available in different capacities to compliment the capacity of the well pump. The bearing housing  117  has a selected capacity that is less than the capacity of the first and second stages  113  and  114 , to provide pressure build-up in the first chamber  125 , to limit fluid flow into the second chamber  126 , and to generate a pressure drop in fluid entering the second chamber  126 . 
     An elongated cylindrical shaft  128  extends through the interior cavity  95  with a splined lower end  129  extending into the lower cavity  108  of the base  93  and a spaced, splined upper end  130  extending through the head  94 . Lower, intermediate and upper bearing journals  132 ,  133  and  134  are sized and spaced along the shaft  128  to fit the lower, intermediate and upper bearings  106 ,  124  and  98 , respectively. A keyway  135  extends longitudinally along shaft  128  with a key  136  mounted therein. The impellers  122  mount on the shaft  128 . A vortex generator  139  is shown as a paddle assembly  140  positioned in the second chamber  126  and having a hub  141  on shaft  128  secured by key  136  and a plurality of spaced vertical paddles  142  that extend radially from the hub  141 . Other styles of vortex generator, such as spiral or propeller, are also suitable. The second chamber  126  is elongated, and the vortex generator  139  is positioned near the bearing housing  117  and spaced from the head  94  to allow more time for gas to separate from the liquid in the production fluid. 
     A coupler  143  connects the upper end  80  of the shaft  78  of the first separation section  11  to the lower end  129  of the shaft  128  of the second separation section  12 . As shown in  FIG. 1 , the studs  38  on the head  16  of the first separation section  11  connect to the flange  107  on the base  93  of the second separation section  12  to connect the first separation section  11  to the second separation section  12 . In a typical installation of the separator  10  mounts between a motor on the base  15  of the first separation section  11  and a well pump secured to the head  94  of the second separation section  12 . The impeller  60  of the first pumping stage  51  of the first separation section  11  pulls production fluid in through the inlet ports  29  and increases the velocity of the production fluid. The diffuser  59  of the first pumping stage  51  of the first separation section  11  converts the increased velocity into pressure. The impeller  60  of the second pumping stage  52  of the first separation section  11  pulls the pressurized production fluid from the first pumping stage  51  and increases the velocity of the production fluid. The diffuser  59  of the second pumping stage  52  of the first separation section  11  converts the increased velocity of the pressurized production fluid into additional pressure, forcing the production fluid into the first chamber  75  of the first separation section  11 . 
     The passages  73  in the bearing housing  55  limit the flow of production fluid through the bearing housing  55  between the first and second chambers  75  and  76 , and thereby generate a pressure drop and rapid expansion of the production fluid entering the second chamber  76 . 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  55  the liquid and gas travel upward to the vortex generator  87 . The paddles  90  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  76 . The liquid passes upwardly to the liquid outlet ports  47  and into the inlet ports  109  in the base  93  of the second separation section  12 . Gas passes upwardly to the gas outlet ports  48  and out of the first separation section  11  at the channel  39  into the well annulus. 
     The second separation section  12  separates any gas remaining in the production fluid by the same process, and the production fluid flows from the second separation section  12  into the well pump. The capacity of the separator  10  is selected based on the required pumping rate and the gas content of the production fluid. The capacity of the separator  10  is determined by the capacity of the first and second separation stages  11  and  12 . The capacity of each of the first and second separation stages  11  and  12  is determined by the size and number of pumping stages and the restriction of the bearing housing. 
     Although two pumping stages are shown for each of the first and second separation stages  11  and  12 , additional pumping stages can be added. Two of more pumping stages provide higher pressures and more effective separation. The capacity of each of the first and second separation stages  11  and  12  is selected separately. The first separation section  11  separates a portion of the gas in the production fluid and vents this gas to the well annulus, and therefore the mass of the production fluid that flows into the second separation section  12  is less than the mass of the production fluid that enters the first separation section  11 . The capacity of the first separation section  11  is selected to be greater than the capacity of the second separation section  12 . 
     The capacity of the first separation section  11  will generally be selected to be greater than the capacity of the second separation section  12  by selecting a bearing housing  55  for the first separation section  11  with a capacity that is greater than the capacity of the bearing housing  117  of the second separation section  12 . The number and capacity of the pumping stages in each separation section is selected to build up pressure in the first chamber. The capacity of the bearing housing in each separation section is selected to limit the fluid flow into the second chamber to be not greater than the fluid flow out of the second chamber to assure that the second chamber will not overfill with fluid, and that a pressure drop will be generated. The fluid flow out of the second chamber is the gas exiting through the gas outlet ports and the fluid being pulled out of the second chamber through the liquid outlet ports by the next downstream pump, whether that pump is in the next separation section or that pump is the well pump. 
     As an example, in a well pumping 1500 BPD where the production fluid is generally a mixture of water and gas, the first and second pumping stages  51 ,  52 ,  113  and  114  would each have a 6000 BPD capacity, the bearing housing  55  for the first separation section  11  would have a capacity of 2500 BPD and the bearing housing  117  for the second separation section  12  would have a capacity of 1000 BPD. As an example, in a well pumping 1500 BPD where the production fluid is generally a mixture of oil and gas, the first and second separation sections  11  and  12  would each include five pumping stages with a capacity of 6000 BPD each, the bearing housing  55  for the first separation section  11  would have a capacity of 3000 BPD and the bearing housing  117  for the second separation section  12  would have a capacity of 1500 BPD. 
     More than two separation sections can be used in the separator  10 . As an alternative structure for connecting the first and second separation stages  11  and  12 , the upper portion  34  of the head  16  of the first separation section  11  can be externally threaded, the studs on the head  16  of the first separation section  11  and the base  93  of the second separation section  12  can be eliminated, and the upper portion  34  of the head  16  of the first separation section  11  can thread directly into the lower end  96  of the housing  92  of the second separation section  12 . 
     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 separation sections each having a first and second chamber, pumping production fluid into the first chamber of the first separation section, limiting flow of production fluid into the second chamber of the first separation section, generating a pressure drop in the production fluid as the fluid passes between the first and second chamber of the first separation section, generating a vortex in the second chamber of the first separation section, pumping production fluid from the second chamber of the first separation section into the first chamber of the second separation section, limiting flow of production fluid into the second chamber of the second separation section, generating a pressure drop in the production fluid as the fluid passes between the first and second chamber of the second separation section, and generating a vortex in the second chamber of the second separation section. More particularly, the first step of the method includes providing, for each of the first and second separation sections, a plurality of pumping stages, 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 of the first separation section. The next step includes limiting fluid flow of the production fluid into the second chamber of the first separation section. The next step includes passing the production fluid through the passages in the first separation section to generate a pressure drop in the 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 into the second separation section. The steps of the first separation section are repeated in the second separation section. 
       FIG. 8  shows the first separation section  11  with an alternative internal pump  145  and an alternative vortex generator  146 . The internal pump  145  is an inducer  148  having an elongated, cylindrical hub  149  and a pair of opposed blades  150  that project radially from hub  149  in a helix around hub  149 . The hub  149  is mounted on shaft  78  and secured on shaft  78  by key  85 , so that the inducer  148  rotates with shaft  78 . The length of inducer  148 , the number of blades  150  and the angle of the blades  150  can vary. The vortex generator  146  includes a pair of spaced paddle assemblies  152 , each having a hub  153  on shaft  78  and secured by key  85 , and a plurality of spaced vertical paddles  154  that extend radially from the hub  153 . 
       FIG. 9  shows the second separation section  11  with an alternative internal pump  156  and an alternative vortex generator  157 . The internal pump  156  is an inducer  159  having an elongated, cylindrical hub  160  and a pair of opposed blades  161  that project radially from hub  160  in a helix around hub  160 . The hub  160  is mounted on shaft  78  and secured on shaft  78  by key  85 , so that the inducer  159  rotates with shaft  78 . The length of inducer  159 , the number of blades  161  and the angle of the blades  161  can vary. The vortex generator  157  includes a pair of spaced paddle assemblies  163 , each having a hub  164  on shaft  78  and secured by key  85 , and a plurality of spaced vertical paddles  165  that extend radially from the hub  164 . 
     The inducer  148  in the first separation section  11  pumps production fluid through the first chamber  75  to the bearing housing  55 . The bearing housing  55  restricts the fluid flow into the second chamber  76 , so that as the fluid enters the second chamber  76  the pressure on the gas is released, allowing the gas bubbles to expand and separate from the liquid. The paddles  154  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  76 . The liquid passes upwardly to the liquid outlet ports  47  and into the inlet ports  109  in the base  93  of the second separation section  12 . Gas passes upwardly to the gas outlet ports  48  and out of the first separation section  11  at the channel  39  into the well annulus. 
     The second separation section  12  separates any gas remaining in the production fluid by the same process, and the production fluid flows from the second separation section  12  into the well pump. The capacity of the first separation section  11  is controlled by the capacity of the bearing housing  55 , and the capacity of the second separation section  12  is controlled by the capacity of the bearing housing  117 . The capacity of the bearing housing  55  of the first separation section  11  restricts the fluid flow rate from the first chamber  75  to the second chamber  76  to a selected first flow rate. The capacity of the bearing housing  117  of the second separation section  12  restricts the fluid flow rate from the first chamber  125  to the second chamber  126  to a selected second flow rate. 
     The well pump is connected downstream of the second separation section  12 , pulling fluid out of the second chamber  126  through the head  94  and pumping the fluid to the surface. The capacity of the bearing housing  117  of the second separation section  12  is selected to maintain a reduced pressure in the second chamber  126 . If the capacity of the bearing housing  117  is too large, the second chamber  126  will fill up and the pressure will increase, inhibiting separation of the gas from the liquid. If the capacity of the bearing housing  117  is too small, the well pump will pull separated gas as well as liquid from the second chamber  126 . The capacity of the bearing housing  55  of the first separation section  11  is selected in a similar manner, to maintain a reduced pressure in the second chamber  76 . 
     The first separation section  11  processes all of the production fluid that is pulled into the separator  10 . The production fluid processed by the second separation section  12  equals the production fluid processed by the first separation section  11  minus the gas separated by the first separation section  11 . Therefore the first flow rate needs to be greater than the second flow rate, and the capacity of the first separation section  11  is selected to be greater than the capacity of the second separation section  12 . The capacity of the second separation section  12  is reduced relative to the first separation section  11  by selecting a bearing housing  117  for the second separation section  12  with a capacity that is smaller than the capacity of the bearing housing  55  of the first separation section  11 . Modification of the housing sizes, housing inner diameters or the internal pumps is not required to provide reduced capacity in the second separation section  12  relative to the first separation section  11 . 
     A method of separating gas and liquid from production fluid in a well, embodying features of the present invention, includes the steps of providing a first separation section with connected first and second chambers, pumping the production fluid into the first chamber of the first separation section, restricting flow of the production fluid from the first chamber into the second chamber of the first separation section to a selected first flow rate, generating a vortex in the second chamber of the first separation section to further separate the gas and the liquid, providing a second separation section connected to the first separation section and having connected first and second chambers, pumping the production fluid from the second chamber of the first separation section into the first chamber of the second separation section, restricting flow of the production fluid from the first chamber into the second chamber of the second separation section to a selected second flow rate that is less than the first flow rate, and generating a vortex in the second chamber of the second separation section, to further separate the gas and the liquid. 
     The step of restricting flow of the production fluid into the second chamber of the first separation section can also include the steps of providing a bearing housing between the first and second chambers with the bearing housing having a plurality of restrictive passages extending between the first and second chambers, and passing the production fluid through the passages. The step of restricting flow of the production fluid into the second chamber of the second separation section can also include the steps of providing a bearing housing between the first and second chambers with the bearing housing having a plurality of restrictive passages extending between the first and second chambers, and passing the production fluid through the passages. The bearing housing in the first separation section has a selected capacity and the bearing housing in the second separation section has a selected capacity that is less than the capacity of the bearing housing in the first separation section. The step of generating a vortex in the second chamber of the first separation section can include the steps of providing a pair of spaced paddle assemblies and rotating the paddle assemblies. The step of generating a vortex in the second chamber of the second separation section can include the steps of providing a pair of spaced paddle assemblies and rotating the paddle assemblies. 
     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.