Downhole gas compression separator assembly

Abstract

Downhole Electric Submersible Pumps (ESP) in a production string often experience gas lock caused by free gas present in the production liquids which reduces intake pressure below the operating parameters of the ESP. A gas compression separator assembly, having a series of compressors and separation chambers, entrains or dissolves the free gas component of the production fluid and separates free gas for downhole disposal. The production fluid fed to the ESP intake has an increased fluid pressure, a reduced volumetric fluid flow, and a lower free gas content, and is less likely to induce gas lock of the ESP.

It is claimed: 
     
         1 . A method to produce fluid from a subterranean well having a production string positioned downhole in a wellbore extending through a formation, the method comprising the steps of:
 (a) flowing production fluid from the formation through an interior passageway defined in the production string, the production fluid having a free gas component and a liquid component;   (b) allowing uninterrupted production fluid flow through a gas compression separator assembly positioned along the production string while:
 compressing the production fluid in the production string; 
 separating at least some free gas from the production liquid; and 
   (c) flowing the compressed production fluid to the intake of an ESP.   
     
     
         2 . The method of  claim 1 , wherein step (b) further comprises dissolving or entraining at least a portion of the free gas into the production liquid. 
     
     
         3 . The method of  claim 1 , wherein step (b) further comprises venting the separated free gas to the exterior of the production string at a downhole location. 
     
     
         4 . The method of  claim 1 , wherein the step of compressing further comprises incrementally compressing the production fluid using a series of compressor assemblies. 
     
     
         5 . The method of  claim 4 , further comprising the step of sequentially reducing the volumetric fluid flow rate of the production fluid using the series of compressor assemblies. 
     
     
         6 . The method of  claim 4 , wherein each compressor assembly of the series has an operating range, and further comprising compressing the production fluid using a compressor assembly to within the operating range of a subsequent compressor assembly. 
     
     
         7 . The method of  claim 4 , wherein the compressor assemblies have at least one impeller and at least one diffuser. 
     
     
         8 . The method of  claim 4 , wherein at least one of the compressor assemblies of the series are assembled in compression. 
     
     
         9 . The method of  claim 4 , wherein the series of compressor assemblies are divided into a plurality compression stages, each compression stage having at least two compressor assemblies, and further comprising driving at least two compression stages utilizing different diameter shafts. 
     
     
         10 . The method of  claim 1 , wherein the step of compressing further includes reducing volumetric flow rate of the production fluid. 
     
     
         11 . The method of  claim 1 , wherein the step of compressing further includes increasing production fluid pressure. 
     
     
         12 . The method of  claim 1 , wherein the step of separating free gas from production liquid further comprises creating a vortex of production fluid in a fluid chamber. 
     
     
         13 . The method of  claim 12 , further comprising forcing lighter production free gas toward the center of the vortex and heavier production liquid toward the fluid chamber wall. 
     
     
         14 . The method of  claim 1 , further comprising venting a portion of free gas through a cross-over tool. 
     
     
         15 . The method of  claim 12 , wherein creating the vortex includes the step of rotating at least one paddle in the fluid chamber. 
     
     
         16 . The method of  claim 1 , further comprising the step of pumping the compressed production fluid to the surface using the ESP. 
     
     
         17 . The method of  claim 1 , further comprising the step of reducing the likelihood of gas lock occurring in the ESP. 
     
     
         18 . An apparatus to prepare production fluid, having a free gas and a liquid component, to be pumped to the surface from a wellbore extending through a subterranean formation, the apparatus comprising:
 (a) a gas compression separator assembly having a plurality of compression stages arranged in series and at least one gas separator assembly, the assemblies allowing uninterrupted production fluid flow therethrough;   (b) each compression stage having at least one compressor assembly having an impeller and at least one diffuser; and   (c) each separator assembly having at least one vent allowing flow of separated free gas to the exterior of the apparatus.   
     
     
         19 . The apparatus of  claim 18 , wherein at least one gas separator assembly is interposed between successive compression stages. 
     
     
         20 . The apparatus of  claim 18 , wherein at least one of the compressor assemblies is mounted in compression on a rotary shaft. 
     
     
         21 . The apparatus of  claim 20 , wherein the compressor assembly mounted in compression transmits torque through the shaft to at least one thrust bearing. 
     
     
         22 . The apparatus of  claim 20 , wherein the compressor assembly mounted in compression includes an impeller mounted to prevent axial movement along the shaft. 
     
     
         23 . The apparatus of  claim 18 , wherein the separator assemblies include a vortex inducer and wherein the at least one vent extends from proximate the axis of a produced vortex to the exterior of the apparatus. 
     
     
         24 . The apparatus of  claim 18 , wherein the compressor assemblies include an impeller made of a corrosion-resistant material. 
     
     
         25 . The apparatus of  claim 18 , wherein the plurality of compression stages comprises at least a first, second, and third compression stage, arranged in series with at least one separator assembly positioned between two compression stages. 
     
     
         26 . The apparatus of  claim 25 , wherein the first compression stage has at least one compressor assembly with a nominal operating range between about 4300 and 6000 BPD. 
     
     
         27 . The apparatus of  claim 25 , wherein the second compression stage has at least one compressor assembly with a nominal operating range of between about 3000 and 4300 BPD. 
     
     
         28 . The apparatus of  claim 25 , wherein the third compression stage has at least one compressor assembly with a nominal operating range of between about 650 and 2200 BPD. 
     
     
         29 . The apparatus of  claim 18 , further comprising at least one ESP in fluid communication with the gas compression separator assembly. 
     
     
         30 . The apparatus of  claim 18 , further comprising an electric motor having a drive shaft for powering the compressor assemblies and at least one gas separator assembly.