Patent Publication Number: US-11655694-B2

Title: Tubing and annular gas lift

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. patent application Ser. No. 17/162,593 that was filed on Jan. 29, 2021, U.S. patent application Ser. No. 16/945,102 that was filed on Jul. 31, 2020, U.S. patent application Ser. No. 16/374,544 that was filed on Apr. 3, 2019, and U.S. patent application Ser. No. 15/916,256 that was filed on Mar. 8, 2018. 
     BACKGROUND 
     Generally when a well is drilled at least one hydrocarbon bearing formation is intersected. Part of the process of completing the well includes installing a liner within the well where the liner also intersects the hydrocarbon bearing formation. Once the liner is in place ports are opened up through the liner so that fluids, usually at least water and oil, may flow from the hydrocarbon bearing formation to the interior of the liner. In a newly completed well, in many instances, there is sufficient pressure within the hydrocarbon bearing formation to force the fluid from the hydrocarbon bearing formation to the surface. After some period of time the pressure gradient drops to the point where the fluids from a hydrocarbon bearing formation are no longer able to reach the surface. 
     Once the fluids are no longer able to naturally reach the surface artificial lift may be employed. One form of artificial lift is known as gas lift. Gas lift involves, at various downhole points in the well, injecting gas into the central passageway of the production tubing string to lift the well fluid in the string. The injected gas, which is lighter than the well fluid displaces some amount of well fluid in the string. The displacement of the well fluid with the lighter gas reduces the hydrostatic pressure inside the production tubing string and allows the reservoir fluid to enter the wellbore at a higher flow rate. 
     In a conventional gas lift operation a production tubular is assembled on the surface and includes a packer and a number of gas lift mandrels. Each mandrel has a check valve and a conventional injection pressure operated gas lift valve. 
     The production tubular is then run into the well so that the packer may be set at some point above the ports in the liner that provide access to the hydrocarbon bearing formation. Once the packer is set fluid may flow from a hydrocarbon bearing formation into an annular area between the liner and the production tubular. The packer prevents the fluid from flowing into the annular area above the packer however the fluid may flow to the bottom of the production tubular and into the production tubular. Once the fluid is in the production tubular it may flow upwards to a level dependent upon the hydrocarbon bearing formation pressure gradient. The fluid in the production tubular will generally flow up past the annular packer and will flow upwards past at least one of the side pocket mandrels. Each check valve in the side pocket mandrels prevents the fluid within the production tubular from flowing through the side pocket mandrel and into the annular area above the packer. 
     In order to begin producing the fluid to the surface, high-pressure gas such as nitrogen is injected into the annular area between the liner and the production tubular. The only outlet for the high-pressure gas is through the gas lift valves into the gas lift mandrels and then into the interior of the production tubular. As the high-pressure gas reaches the gas lift valve the high-pressure gas flows into the gas lift valve through ports in the side of the gas lift valve. The ports are located between the gas lift valve seat and the bellows. The high-pressure gas acts on the bellows adapter and the bellows compressing the bellows which in turn lifts the ball off of the seat. With the ball off of the seat the high-pressure gas is able to flow through the seat into the check valve. The high-pressure gas then acts upon the check valve, where the check valve has a check dart that the high pressure gas compresses against a spring lifting the check dart off of a check pad allowing the high-pressure gas to flow through the check valve and into the gas lift mandrel. As the gas flows out of the gas lift mandrel and into the interior of the production tubular adjacent the gas lift mandrel the high-pressure gas causes the fluid to become a froth. The effect is similar to blowing bubbles into milk through a straw. The column of fluid which is now froth has a much lower density and therefore a lower head pressure than a pure liquid column. The natural formation pressure in conjunction with the flow of high pressure gas now flowing upward through the production tubular lifts the froth, and thus the hydrocarbons and other fluid, to the surface. 
     SUMMARY 
     Generally an operator may utilize a gas lift system wherein high-pressure gas is injected into a well in the annular area between the casing and the production tubular. The gas then enters the production tubular at intervals along the production tubular in order to lift any liquid within the production tubular to the surface. However in certain instances it has been found advantageous to be able to reverse the high-pressure gas injection and therefore the lift direction. The high pressure gas is injected into the production tubular where the gas then flows through the production tubular and into the well where at predetermined points along the production tubular the high pressure gas is directed through a gas lift mandrel having a gas tight chamber and into the annular area between the production tubular and the casing. 
     More specifically a system has been envisioned where a production tubular is assembled on the surface. In order to facilitate production through the tubular to the surface a series of gas lift mandrels are installed as a part of the production string. The gas lift mandrels are spaced some preset distance apart from one another along the length of the production string. Each mandrel includes an externally mounted check valve and an externally mounted gas lift valve. The production tubular with the gas lift mandrels are then installed within the well. Each check valve prevents flow of any fluid or gas including the high-pressure injected gas, within the production tubular into the annular area between the production tubular and casing. The gas lift valve tends to prevent the flow of high pressure gas from the annular region into the production tubular until a particular preset pressure is reached. Upon reaching the preset pressure the system allows high-pressure gas to be injected into the production tubular. 
     In order to allow reverse flow, as may be required or desired by the operator, when that same system described above is assembled on the surface, an additional, different set of gas lift mandrels is installed as part of the same production string. The second set of gas lift mandrels has an external, gas tight chamber where a flow path through the external, otherwise gas tight chamber is through a check valve and a gas lift valve both installed within the external, gas tight chamber. The second set of gas lift mandrels allow high-pressure gas to be injected into the interior of the production tubular from the surface. As the high-pressure gas reaches the second set of mandrels the high-pressure gas flows through a port from the interior of the mandrel into the external, gas tight chamber. The high-pressure gas then surrounds the gas lift valve. The gas lift valve prevents the high-pressure gas from flowing from the external chamber into the annular area of the well between the production tubular and the casing until the pressure within the external chamber reaches up a particular preset pressure. Upon reaching the particular preset pressure the gas within the external chamber causes the gas lift valve to open allowing the high-pressure gas to flow from the external chamber through the check valve and into the annular region of the well between the production tubular and the casing. The check valve is typically placed between the gas lift valve and the annular region of the well preventing any fluid or gas, including high-pressure gas, in the annular region of the well from flowing into the gas lift valve, the external chamber, and the interior of the production tubular. 
     By having a first set of exterior mounted gas lift valves that allow gas to be injected from the annulus into the interior of the production tubular while also having a second set of exterior mounted gas lift valves that allow gas to be injected from the interior of the production tubular into the annular area between the production tubular and the casing or wellbore an operator can produce fluid in either direction as required by well conditions. The first set of exterior mounted valves include a check valve that prevent the flow of high pressure gas or fluid from the interior of the production tubular into the annular area. The second set of exterior mounted valves include an exterior gas tight chamber having a flow path that forces all flow through the gas lift valve and the check valve. In the second set of exterior mounted valves however the check valve prevents the flow of high pressure gas or fluid from the annular area into the interior of the production tubular. 
     Advantages and other features of the invention will become apparent from the following drawing, description and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    depicts a gas lift system using high pressure gas injected into the annular area to assist in moving fluids in the interior of the tubular to the surface. 
         FIG.  2    depicts a gas lift system using high pressure gas injected into the interior of the production tubular to assist in moving fluids in the annular region to the surface. 
         FIG.  3    depicts a gas lift system using both high pressure gas injected into the annular area to assist in moving fluids in the interior of the tubular to the surface and using high pressure gas injected into the interior of the production tubular to assist in moving fluids in the annular region to the surface. 
         FIG.  4    depicts a packer less and plug less gas lift system injecting gas into the annular region. 
         FIG.  5    depicts a packer less and plug less gas lift system injecting gas into the production tubular. 
         FIG.  6    depicts a gas lift system injecting gas into the annular region having a packer in place. 
         FIG.  7    depicts a gas lift system injecting gas into the annular region having a packer and landing nipple in place. 
         FIG.  8    depicts a reversible gas lift system with both a packer and plug at the lower end of the production tubular. 
         FIG.  9    depicts a reversible gas lift system with an isolation sub straddling ports in the production tubular. 
         FIG.  10    depicts a lower portion of an alternate embodiment of a reversible gas lift system having a sliding sleeve. 
         FIG.  11    depicts a configuration of the gas lift system including a sliding sleeve assembly in the closed position. 
         FIG.  12    depicts a reversible gas lift system having a packer with a one-way valve and plug at the lower end of the production tubular. 
         FIG.  13    depicts the system from  FIG.  12    in tubular lift flow. 
     
    
    
     DETAILED DESCRIPTION 
     The description that follows includes exemplary apparatus, methods, techniques, or instruction sequences that embody techniques of the inventive subject matter. However, it is understood that the described embodiments may be practiced without these specific details. 
       FIG.  1    depicts a gas lift system  10  where a production tubular  12  running from the surface  14  has a gas lift mandrel  16  assembled into the production tubular  12  using collars  20  and  22 . The gas lift mandrel  16  includes a port  24  that provides access from the annular region  26 , between the casing  28  and the exterior of the production tubular  30 , to the interior of the production tubular  32 . The check valve  36  is a one-way valve that is oriented to prevent oil or gas, including high-pressure gas, from flowing through this particular mandrel from the interior of the production tubular  32  to the exterior of the production tubular  30  while allowing the flow of fluid or gas from the annular region  26  to the interior of the production tubular  32 . 
     In operation this particular configuration of the gas lift system  10  utilizes high-pressure gas as depicted by arrow  40  injected into the annular region  26  which then flows to gas lift valve  42  and into port  44  in gas lift valve  42  to enter the interior of gas lift valve  42 . The gas then flows through gas lift valve  42  towards check valve  36 . The high-pressure gas causes check valve  36  to open allowing the flow of high pressure gas from the annular region  26  to the interior of the production tubular  32 . The high-pressure gas then enters the interior of the production tubular  32  forming areas of lower density  46 . The areas of lower density  46  may be commonly referred to as bubbles. The bubbles  46  are utilized to reduce the density of the column of fluid  48  within the production tubular  12  so that the natural reservoir pressure may lift the column of fluid and bubbles to the surface. 
       FIG.  2    depicts a gas lift system  110  where a production tubular  112  running from the surface  114  has a gas lift mandrel  116  assembled into the production tubular  112  using collars  120  and  122 . The gas lift mandrel  116  includes a gas tight external chamber  150 . The gas tight external chamber  150  is attached to the gas lift mandrel  116  and provides a port  152  to allow gas inside the gas lift mandrel  116  to flow through the port  152  and into the interior of the gas tight external chamber  150 . Gas in the external gas tight chamber  150  is then forced into gas lift valve  142  via port  144 . The gas then continues on to check valve  136  where the gas causes the check valve  136  to open further allowing the gas access to port  124  which then provides access to the annular region  126 , between the casing  128  and the exterior of the production tubular  130 . The check valve  136  is a one-way valve that is oriented to prevent oil or gas, including high-pressure gas, from flowing from the annular region  126  and into the gas tight external chamber  150  thereby preventing oil or gas from flowing from the annular region  126  to the interior of the production tubular  132 . 
     In operation this particular configuration of the gas lift system  110  utilizes high-pressure gas as depicted by arrow  140  injected into the interior of the production tubular  132 . The high-pressure gas then flows into gas lift mandrel  116  and thereafter through port  152  and into the gas tight external chamber  150 . The gas tight external chamber  150  forces the high-pressure gas to surround both the check valve  136  and the gas lift valve  142 . The high-pressure gas then flows into the interior of the gas lift valve  142  through ports  144 . The gas lift valve  142  further directs the high-pressure gas into the interior of check valve  136 . The high-pressure gas causes check valve  136  to open allowing the flow of high pressure gas from the interior of the production tubular  132  to the annular region  126  while preventing oil or gas from flowing from the annular region  126  to the interior of the production tubular  132 . As the high-pressure gas enters the annular region  126  areas of lower density or bubbles  146 . The bubbles  146  are utilized to reduce the column of fluid  148  within the annular region  126  so that the natural reservoir pressure may lift the column of fluid  148  and bubbles  146  to the surface. 
       FIG.  3    is an embodiment of the current invention where either the high-pressure gas may be injected into the production tubular to lift fluid through the annular region or, as desired, the high-pressure gas may be injected into the annular region allowing fluid within the production tubular to be lifted to the surface. The operator may switch between one direction or the other without pulling the production tubular or running a wireline system into the well to change out to gas lift valves. 
     The gas lift system in  FIG.  3    includes a first mandrel  216  configured to allow a gas lift valve  242  and a check valve  236  to be attached providing for high-pressure gas to be injected from the annular region  226  into the interior of the production tubular  232 . The gas lift system  210  also includes a second gas lift mandrel  266  provided with an external chamber  290  to allow a gas lift valve  292  and a check valve  286  to be attached that provide for high-pressure gas to be injected from the interior the production tubular  232  into the annular region  226  of the well which may be cased or open hole. 
     More specifically the gas lift system  210  includes a production tubular  212  running from the surface  214 . The production tubular  212  has a first gas lift mandrel  216  assembled into the production tubular  212  using collars  220  and  222  and a second gas lift mandrel  266  also assembled into the production tubular  212 . While only a first and a second gas lift mandrel are depicted is envisioned that numerous gas lift mandrels will be used within a single well. The first gas lift mandrels and second gas lift mandrels may be spaced consecutively or may be interspersed with one another. 
     The first gas lift mandrel  216  includes a port  224  that provides access from the annular region  226 , between the casing  228  and the exterior of the production tubular  230 , to the interior of the production tubular  232 . The check valve  236  is attached to port  224  and is a one-way valve that is oriented at the first gas lift mandrel  216  to prevent oil or gas, including high-pressure gas, from flowing through the first gas lift mandrel  216  and port  224  from the interior of the production tubular  232  to the exterior of the production tubular  230  while allowing the flow of fluid or gas from the annular region  226  to the interior of the production tubular  232 . A gas lift valve  242  is attached to check valve  236 . Port  224 , check valve  236 , and gas lift valve  242  form a gas or fluid pathway between the interior of the production tubular  232  and annular region  226 . 
     The second gas lift mandrel  266  includes a port  274  that provides access between the interior of the production tubular  232  through port  274  and a gas tight external chamber  290  such that the fluid and gas flow path between the interior of the gas lift mandrel  266  and the annular region  226 , between the casing  228  and the exterior of the production tubular  230 , goes through port  274 , gas tight external chamber  290 , into gas lift valve  292 , check valve  286 , through a second port in the gas tight external chamber  290 , and then into the annular region  226 . The check valve  286  is is a one-way valve that is oriented at the second gas lift mandrel  266  to prevent oil or gas, including high-pressure gas, from flowing from the annular region  226  and into the gas tight external chamber  290  which also precludes the flow of fluids into the interior of the production tubular  232  via gas lift mandrel  266  while allowing the flow of fluid or gas from the interior of the production tubular  232  through the gas tight external chamber  290 , gas lift valve  292 , and check valve  286  to the annular region  226 . Port  274 , check valve  286 , and gas lift valve  292  form a gas or fluid pathway between the annular region  226  and the interior of the production tubular  232 . 
     In operation the operator may determine some point that gas lift is required to produce well fluid, which is typically a hydrocarbon water mix, through the interior of the production tubular  232  to the surface  214 . In this instance high-pressure gas as depicted by arrow  240  is injected into the annular region  226 . The high-pressure gas will generally have a flowpath to both the exterior of the first gas lift mandrel  216  and the exterior of the second gas lift mandrel  266 . The high-pressure gas that reaches the second mandrel  266  has a flowpath through check valve  286 , gas lift valve  292 , the gas tight external chamber  290 , and port  274 . However at the second mandrel  266  the check valve  286  is oriented to prevent the high-pressure gas or other fluids from flowing from the annular region  226  and into the flowpath that includes the gas tight external chamber  290 . The high-pressure gas that reaches the first mandrel  216  has a flowpath into port  243  and into gas lift valve  242 . Gas lift valve  242  then directs the high-pressure gas into check valve  236  which in this case is oriented to allow the high-pressure gas to flow through the check valve  236  and further through port  224  into the interior of the first gas lift mandrel  216  which is part of production tubular  232 . As the high-pressure gas enters the interior of the production tubular  232  bubbles  246  are formed by the high-pressure gas within the fluid. The bubbles  246  reduce the density of the column of fluid  248  within interior of the production tubular  232  so that the natural reservoir pressure may lift the column of fluid  248  and the bubbles  246  to the surface. 
     In contrast the operator may determine some point that gas lift is required to produce well fluid through the annular region  226  to the surface  214 . In this instance high-pressure gas as depicted by arrow  291  is injected into the interior of the production tubular  232 . In this instance the high-pressure gas will generally have a flowpath to both the interior of the first gas lift mandrel  216  and the interior of the second gas lift mandrel  266 . The high-pressure gas that reaches the first gas lift mandrel  216  has a flowpath through port  224 , check valve  236 , and gas lift valve  242 . However at the first gas lift mandrel  216  the check valve  236  is oriented to prevent the high-pressure gas or other fluids from flowing from the interior of the production tubular  232  and into the flowpath that includes the gas lift valve  242 . The high-pressure gas that reaches the second gas lift mandrel  266  has a flowpath into port  274 , gas tight external chamber  290 , gas lift valve  292 , and check valve  286 . As the high-pressure gas flows from the interior of the production tubular  232  it flows through the port  274  and into the interior of the gas tight external chamber  290 . The gas tight external chamber  290  then causes the high-pressure gas to flow through port  295  and into the interior of gas lift valve  292 . Gas lift valve  292  then directs the high-pressure gas into check valve  286 , provided that the high-pressure gas has sufficient pressure to open the gas lift valve. Check valve  236  is oriented to allow the high-pressure gas to flow through the check valve  236  and into the annular region  226 . As the high-pressure gas enters the interior of the annular region  226  bubbles  247  are formed by the high-pressure gas within the fluid. The bubbles  247  reduce the density of the column of fluid  249  and within the annular region  226  so that the natural reservoir pressure may lift the column of fluid  248  and the bubbles  246  to the surface. 
       FIG.  4    depicts a packer less and plug less gas lift system in the configuration shown the well  300  has a casing  302  and a production tubular  304  the production tubular  304  includes a first mandrel  306 . The first mandrel  306  includes a port  310  that allows fluid and/or gas access from the interior the production tubular  304  to the annular area  308  between the interior of casing  302  and the exterior of the production tubular  304 . The port  310  is adapted to accept check valve  312  where check valve  312  is configured to allow one-way fluid flow from the annular area  308  to the interior of mandrel  306  while preventing fluid flow from the interior mandrel  306  to the annular area  308 . 
     The production tubular  304  also includes a second mandrel  314  including a port  316 . The port  316  is adapted to provide fluid access to chamber  318 . Chamber  318  is adapted to incorporate gas lift valve  320  and check valve  322  such that fluid entering the chamber through port  316  is directed into gas lift valve  320  and then into check valve  322  and finally into port  324 . Where port  324  allows fluid access from check valve  322  through port  324  and into annular area  308 . The gas flow from the interior of the second mandrel  314  through port  316  into chamber  318  then into gas lift valve  320 , through check valve  322 , through port  324  and finally into the hydrocarbons in the annular area  308  is depicted by arrows  326  and  328 . 
     As can be seen in  FIG.  4    production tubular  304  does not include a plug below mandrel  314 . In this configuration the operator relies on produced fluids  330  within production tubular  304  having sufficient pressure to provide a gas tight seal and forcing any pressurized gas as depicted by arrow  332  within the production tubular  304  to flow through port  316  and ultimately out of port  324  before pushing the fluid gas interface  338  below the lower end  340  of production tubular  304 . As gas is injected into the annular region  308  through ports  316  and  324  the produced fluid and the annular region  308  is transported to the surface causing a reduction in the fluid pressure below the gas fluid interface  338 . As more of the produced fluid is moved to the surface eventually the gas fluid interface  338  moves to the lower end  340  of the production tubular  304  with the gas fluid interface  338  below the lower end  340  of production tubular  304  the pressurized gas within the production tubular  304  escapes around the lower end  340  the production tubular  300  for into the annular area  308  stopping the produced fluid from moving to the surface. 
     With annular production stopped the gas flow is reversed as indicated in  FIG.  5   . Again the operator relies on produced fluids  330  now in the annular area  308  having sufficient pressure to provide a gas tight seal and forcing any pressurized gas as depicted by arrow  350  within the annular area  308  to flow into gas lift valve  352 . The pressurized gas then flows from gas lift valve  352  into check valve  312  which is oriented to allow gas to flow from the gas lift valve  352  into port  310  and then into the interior of mandrel  306 . 
     As gas is injected into the interior of mandrel  306  and thus into production tubular  304  through port  310  the produced fluid within the interior of mandrel  306  and production tubular  304  is transported to the surface causing a reduction in the fluid pressure below the second gas fluid interface  356 . As more of the produced fluid is moved to the surface eventually the second gas fluid interface  356  moves to the lower end  340  of the production tubular  304 . Once the second gas fluid interface  356  reaches the lower end  340  of production tubular  304  the pressurized gas within the annular area  308  escapes around the lower end  340  the production tubular into the production tubular  304  stopping the produced fluid from moving to the surface. 
       FIG.  6    depicts a variation on the system described in  FIG.  4   . As before and the well  300  has a casing  302  and a production tubular  304  the production tubular  304  includes a first mandrel  306 . The first mandrel  306  includes a port  310  that allows fluid and/or gas access from the interior the production tubular  304  to the annular area  308  between the interior of casing  302  and the exterior of the production tubular  304 . The port  310  is adapted to accept check valve  312  where check valve  312  is configured to allow one-way fluid flow from the annular area  308  to the interior of mandrel  306  while preventing fluid flow from the interior mandrel  306  to the annular area  308 . 
     The production tubular  304  also includes a second mandrel  314  including a port  316 . The port  316  is adapted to provide fluid access to chamber  318 . Chamber  318  is adapted to incorporate gas lift valve  320  and check valve  322  such that fluid entering the chamber through port  316  is directed into gas lift valve  320  and then into check valve  322  and finally into port  324 . Where port  324  allows fluid access from check valve  322  through port  324  and into annular area  308 . The gas flow from the interior of the second mandrel  314  through port  316  into chamber  318  then into gas lift valve  320 , through check valve  322 , through port  324  and finally into the hydrocarbons in the annular area  308  is depicted by arrows  326  and  328 . 
     As can be seen in  FIG.  6    however production tubular  304  now includes a plug  360  below mandrel  314 . In this configuration the operator relies on plug  360  within production tubular  304  to provide a gas tight seal and forcing any pressurized gas as depicted by arrow  332  within the production tubular  304  to flow through port  316  and ultimately out of port  324 . In the configuration including plug  360  higher gas pressures may be included within production tubular  304  providing higher rates of gas flow through port  24  and into the produced fluids increasing the rate of production of fluids to the surface. At some point there will be insufficient hydrocarbons or produced fluid available in the annular area for the annular lift system to function. Upon reaching the point where annular lift no longer functions the plug  360  is removed, typically by wireline. In some instances the plug  360  may remain within the production tubular  304  provided that fluid access is facilitated between the interior of the production tubular  304  and the hydrocarbons or produced fluids below the plug  360 . Some examples of fluid access through or around the plug may be where fluid access is provided by one or more burst disks. The burst disk may be provided within the plug or in the subassembly sitting above the plug where the burst disks are directed radially outward. In other instances a wireline tool may simply puncture the plug rather than removing the plug, while an even other instances pressure cycles may shift a portion of the plug to provide fluid access through or around the plug. 
     In some instances, as depicted in  FIG.  7   , it may be desirable to provide a landing nipple  370  above the plug  360 . The landing nipple  370  may be useful for landing a second plug or other tooling as desired by the operator. 
       FIG.  8    depicts a reversible gas lift system  700  with both a packer  702  and plug  704  at the lower end  706  of the production tubular  708 . Initially gas will be injected into the interior of the production tubular  708  as indicated by arrow  710 . Check valve  712  prevents the gas from exiting through port  714  in mandrel  716 . Plug  704  prevents the gas from exiting through the lower end  706  of the production tubular  708 . The gas must then exit through port  718  in mandrel  720 . The gas then flows from port  718  to the interior of chamber  722  where then flows into the inlet of gas lift valve  724  into check valve  726  through port  728  and into the annular area  730  as indicated by arrow  732 . Port  728  connects the interior of chamber  722  with the annular area  730 . Packer  702  isolates the annular area  730  from the lower end of the well forcing the wellbore fluid to enter the lower end  706  of production tubular  708 . The wellbore fluid then enters the annular area  730  through ports  736  in the production tubular below plug  704  as indicated by arrow  734 . Port or ports  736  may simply be a ported sub assembled into the production tubular. 
     At some point within the life of the well the operator will change the well from annular lift to production tubular lift where gas is injected into the annular region and fluids are produced to the surface through the production tubular  708  as indicated in  FIG.  9   . In order to facilitate the switchover, fluid access will have to be provided through plug  704  (from  FIG.  8   ). In many instances a wireline tool will be run into the production tubular to latch onto plug  704  and remove it to the surface. In other instances the plug may be released so they can fall to the bottom of the well. In other instances a simple burst disk may be burst to allow fluid access below the plug  704 . As indicated the plug  704  has been removed from the production tubular  708 . With plug  704  removed an isolation tool  740  is run into the well and located within the production tubular so that the isolation tool  740  straddles ports  736  and is then set so that the isolation tool  740  will prevent fluid flow between the annular area  730  and the interior the production tubular  708  through ports  736 . With ports  736  now closed gas may be injected into the annular area  730  where packer  702  prevents the gas from exiting the annular area into the wellbore below the lower end  706  of production tubular  708 . Previously in the annular lift configuration pressurized gas entered into the annular area  706  through port  728 . In production tubular lift check valve  726  prevents flow into production tubular  708 . The pressurized gas is then forced into gas lift valve  742  after which interest check valve  712  which allows the gas to flow into port  714  and finally into the interior of mandrel  716 , as indicated by arrows  748 . Mandrel  716  is part of production tubular  708 . The gas that is been injected into the interior of production tubular  708  reduces the overall density of the fluid within the production tubular as indicated by bubbles  744  allowing the fluid to be to produced to the surface as indicated by arrow  746 . 
       FIG.  10    depicts a lower portion of an alternate embodiment of a reversible gas lift system wherein the ports  736  from  FIGS.  8  and  9    are replaced with a sliding sleeve assembly  770 . As before the reversible gas lift system  800  includes a packer  802  and plug  804  at the lower end  806  of the production tubular  808 . Initially gas will be injected into the interior of the production tubular  808  as indicated by arrow  810 . Plug  804  prevents the gas from exiting through the lower end  806  of the production tubular  808 . The gas must then exit the interior of the production tubular  808  through port  818  in mandrel  820 . The gas then flows from port  818  to the interior of chamber  822  where it then flows into the inlet  823  of gas lift valve  824  into check valve  826  through port  828  and into the annular area  830  as indicated by arrow  832 . Port  828  connects the interior of chamber  822  with the annular area  830 . Packer  802  isolates the annular area  830  from the lower end of the well forcing the wellbore fluid to enter the lower end  806  of production tubular  808 . The wellbore fluid flows upward into the production tubular  808  entering sliding sleeve assembly  770 . The wellbore fluid is prevented from flowing any further upwards in the production tubular  808  by plug  804 . However the sliding sleeve assembly  770  includes a housing  840  and an inner sleeve  842  where the housing  804  includes ports  844  and the inner sleeve  842  includes ports  846 . In the run in or open position ports  844  and  846  are aligned allowing fluid access between an interior of the sliding sleeve assembly  770  and the annular area  830  such that the wellbore fluid which is entered the lower end of the production tubular  888  and then the interior the sliding sleeve assembly  770  may continue upwards in the annular area  830  by passing through ports  844  and  846 . 
       FIG.  11    depicted configuration of the gas lift system  800  including sliding sleeve assembly  770  in the closed position. When it is required to change the production of wellbore fluids from annular lift to production tubular lift, as before fluid access is provided through the interior of the production tubular  808  past plug  804 . With fluid access past plug  804  the inner sleeve  842  is shifted so that ports  844  in the housing  840  and ports  846  in the inner sleeve  842  are no longer aligned wherein fluid access between the interior of the production tubular  808  and the annular area  830  is prevented allowing pressurized gas to be injected into the annular area  830  where packer  802  prevents the gas from exiting the annular area  830  into the wellbore below the lower end  806  of production tubular  808 . Where the pressurized gas is then injected into the interior of the production tubular  808  reducing the overall density of the wellbore fluids and allowing the wellbore fluids to be to produced to the surface. 
       FIG.  12    depicts a reversible gas lift system  900  having a packer  902  and plug  904  at the lower end  906  of the production tubular  908 . Initially gas will be injected into the interior of the production tubular  908  as indicated by arrow  910 . Check valve  912  prevents the gas from exiting through port  914  in mandrel  916 . Plug  904  is equipped with a one-way valve  905 . Together plug  904  and one-way valve  905  prevent the flow of fluids or gas from the upper region  907  of the production tubular past the plug  904  and one-way valve  905  towards the lower end  906  of the production tubular  908 . The one-way valve may be a check valve, a poppet valve, a flapper valve or other one-way valve. With the other potential pathways blocked the gas exits through port  918  in mandrel  920 . The gas then flows from port  918  to the interior of chamber  922  where the gas then flows into the inlet of gas lift valve  924  into check valve  926  through port  928  and into the annular area  930  as indicated by arrow  932 . Packer  902  is also equipped with a one-way valve  911 . In this instance the one-way valve  911  allows fluid below packer  906  to pass through the one-way valve  911  as indicated by arrow  909  and enter the annular region  930  where the fluids are injected with the gas flowing out of port  928  so that the fluids may be produced to the surface. 
       FIG.  13    depicts the system from  FIG.  12    when tubular lift flow or reverse flow is desired. Gas is injected into the annular region  930  and fluids are produced to the surface through the production tubular  908 . In this instance no further action by the operator is required as one-way valve  911  closes in the presence of flow from the annular region  930  towards the lower end  906  of production tubular  908  to prevent the downward flow of gas or fluid out of the annular region  930  while one-way valve  905  opens to allow the produced or other fluids below the plug  904  to move upwards past plug  904  as indicated by arrow  913  where the fluids are injected with gas thorough port  914  and produced to the surface. 
     The methods and materials described as being used in a particular embodiment may be used in any other embodiment. While the embodiments are described with reference to various implementations and exploitations, it will be understood that these embodiments are illustrative and that the scope of the inventive subject matter is not limited to them. Many variations, modifications, additions and improvements are possible. 
     Plural instances may be provided for components, operations or structures described herein as a single instance. In general, structures and functionality presented as separate components in the exemplary configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements may fall within the scope of the inventive subject matter.