Multi-stage, limited entry downhole gas separator

Abstract

A gas separator for use in a wellbore. The separator has an annular, staged separator system, whereby a liquid-gas mixture is separated into its liquid and gas components. Gas components are allowed to escape up the annulus around the separator, while liquid components are captured on each stage and removed through an inner tube. The inner tube has limited entry ports. These ports may be sized such that ports at the top of the string have a smaller, more limited entry than those toward the bottom.

The invention claimed is: 
     
         1 . A method of separating a multi-phase fluid into a liquid component and a gaseous component, the method comprising:
 receiving the multi-phase fluid into a first annular region defined between a casing and an outer tube;   transmitting at least a portion of the multi-phase fluid from the first annular region into a plurality of separator stages defined within a second annular region between the outer tube and an inner tube, each separator stage bounded by a first isolation member and a second isolation member;   within each separator stage, separating the multi-phase fluid into a gaseous component and a liquid component;   directing the gaseous component from each separator stage into the first annular region;   directing the liquid component from each separator stage into the inner tube through a corresponding limited entry port, wherein the limited entry ports of the plurality of separator stages are arranged in order of increasing cross-sectional area from the topmost stage to the bottom-most stage.   
     
     
         2 . The method of  claim 1  further comprising disrupting a velocity of the multi-phase fluid using an annular velocity disruptor apparatus. 
     
     
         3 . The method of  claim 2  in which the annular velocity disruption apparatus defines a slot having a width of at least two inches. 
     
     
         4 . The method of  claim 3  in which the slot has an axial length of at least eight inches. 
     
     
         5 . The method of  claim 1  further comprising allowing fluid to flow from the first annular region into the inner tube through a bottom entry port located below the plurality of separator stages. 
     
     
         6 . The method of  claim 5  further comprising regulating flow through the bottom entry port with a pressure-responsive variable valve. 
     
     
         7 . The method of  claim 6  in which the pressure-responsive variable valve adjusts flow into the bottom entry port in response to pressure differential between the first annular region and the inner tube. 
     
     
         8 . The method of  claim 6  in which the pressure-responsive variable valve opens proportionally in response to reduced flow through one or more of the plurality of limited entry ports. 
     
     
         9 . The method of  claim 1 , wherein each of the plurality of separator stages is configured to intake fluid at a different elevation than an adjacent one of the plurality of separator stages. 
     
     
         10 . The method of  claim 1  in which each of the limited entry ports is a different size. 
     
     
         11 . The method of  claim 1  further comprising pumping the liquid component to a surface location through the inner tube. 
     
     
         12 . The method of  claim 1  further comprising plugging the first annular region below the bottom-most of the plurality of separator stages. 
     
     
         13 . The method of  claim 1  in which at least one of the plurality of separator stages has an axial length of forty-eight inches or more. 
     
     
         14 . The method of  claim 1  further comprising:
 producing the liquid component at a surface location from the inner tube; and 
 producing the gaseous component at a surface location from within the casing. 
 
     
     
         15 . The method of  claim 1  in which each of the plurality of separator stages defines an intake slot within the outer tube, wherein the intake slot is approximately one-sixth the axial length of its associated separator stage. 
     
     
         16 . The method of  claim 1  in which no multi-stage fluid may directly enter a separator stage from the second annular region of an adjacent separator stage. 
     
     
         17 . A method, comprising:
 diverting portions of a multi-stage fluid travelling upward through an annular space between a casing and a separator body into the separator body through spaced-apart intake openings within a set of vertically stacked and isolated separator stages arranged along the body;   causing the multi-stage fluid to slow, settle, and separate into a gaseous portion and a liquid portion within each of the isolated separator stages, such that the gaseous portion escapes into the annular space and the liquid portion remains; and   pumping the liquid portion from each of the isolated separator stages through a corresponding port, into an internal tube that directs the liquid portion upward toward a surface, wherein none of the ports have a smaller cross-sectional area than the port within the top-most of the stages, and none of the ports has a larger cross-sectional area than the port within the bottom-most of the stages, and at least two of the ports have different cross-sectional areas.   
     
     
         18 . The method of  claim 17  further comprising:
 regulating flow through the bottom entry port with a pressure-responsive variable valve.