Downhole gas ventilation system for artificial lift applications

A downhole gas ventilation system includes a perforated tubing positioned within a production tubing installed in a wellbore. The perforated tubing couples to wellbore equipment positioned uphole of the perforated tubing within the wellbore to flow multiphase hydrocarbons received within the perforated tubing into the wellbore equipment. The perforated tubing includes two ends and a sidewall connecting the two. Multiple perforations formed in the sidewall receives the multiphase hydrocarbons within the perforated tubing. The perforated tubing outer diameter is smaller than the production tubing inner diameter. The perforated tubing facilitates separation of the liquid phase from the gaseous phase. A one-way check valve is coupled to the upper end of the perforated tubing to vent the gaseous phase that rises towards the upper end out of the perforated tubing, out of the production tubing and into an annulus defined between the production tubing and the wellbore inner wall.

TECHNICAL FIELD

This disclosure relates to wellbore operations, for example, producing hydrocarbons through wellbores.

BACKGROUND

Hydrocarbons entrapped in subsurface reservoirs are raised to the surface, i.e., produced, through wellbores formed from the surface to the subsurface reservoirs through a subterranean zone (e.g., a formation, a portion of a formation, multiple formations). The hydrocarbons (e.g., petroleum, natural gas, water, combinations of them) are multiphase fluids including a liquid phase and a gaseous phase. In a first stage of hydrocarbon recovery, the multiphase fluid flows through the wellbore under reservoir pressure. Over time, reservoir pressure decreases. Then, secondary (and sometimes tertiary) stages of hydrocarbon recovery are implemented in which the multiphase fluids are produced using artificial lift techniques. In one such technique, a pump is disposed at a downhole location. The pump draws the multiphase hydrocarbons that is downhole of the pump and flows the hydrocarbons towards the surface. The presence of gaseous phase in the flowing hydrocarbons can result in inefficiency in pump operations.

SUMMARY

This disclosure describes technologies relating to downhole gas ventilation systems for artificial lift applications.

Certain aspects of the subject matter described here can be implemented as a downhole gas ventilation system. The system includes a perforated tubing configured to be positioned within a production tubing installed in a wellbore formed in a subterranean zone to a subsurface reservoir in which multiphase hydrocarbons including a liquid phase and a gaseous phase are entrapped. The perforated tubing can fluidically couple to wellbore equipment configured to be positioned uphole of the perforated tubing within the wellbore and to permit flow of the multiphase hydrocarbons received within the perforated tubing into the wellbore equipment. The perforated tubing includes an upper end, a lower end and a sidewall connecting the upper end and the lower end. The perforated tubing includes multiple perforations formed in the sidewall and configured to receive the multiphase hydrocarbons within the perforated tubing. An outer diameter of the perforated tubing is smaller than an inner diameter of the production tubing. The perforated tubing can facilitate separation of the liquid phase from the gaseous phase of the received multiphase hydrocarbons. The system includes a one-way check valve fluidically coupled to the upper end of the perforated tubing. The check valve is configured to vent the gaseous phase that rises towards the upper end of the perforated tubing out of the perforated tubing, out of the production tubing and into an annulus defined between the production tubing and an inner wall of the wellbore.

An aspect combinable with any other aspect includes the following features. The wellbore equipment includes a mandrel configured to receive the multiphase hydrocarbons from which a portion of the gaseous phase has been separated through the upper end of the perforated tubing.

An aspect combinable with any other aspect includes the following features. The system includes a seating nipple that can connect to the perforated tubing. The seating nipple, on one end, can attach to the upper end of the perforated tubing, and on the opposite end, can attach to the mandrel. The seating nipple can flow the liquid phase that is separated from gaseous phase within the perforated tubing into the mandrel.

An aspect combinable with any other aspect includes the following features. The upper end of the perforated tubing is directly connected to the mandrel.

An aspect combinable with any other aspect includes the following features. The mandrel is a gas lift mandrel that includes a gas lift valve fluidically coupled to the production tubing. The one-way check valve is installed within the gas lift mandrel.

An aspect combinable with any other aspect includes the following features. At least a portion of the perforated tubing including the upper end passes through the gas lift mandrel.

An aspect combinable with any other aspect includes the following features. An outer diameter of the gas lift mandrel is greater than an outer diameter of the production tubing and smaller than an inner diameter of the wellbore.

An aspect combinable with any other aspect includes the following features. The one-way check valve is installed in a portion of the gas lift mandrel that extends into the annulus.

An aspect combinable with any other aspect includes the following features. The perforated tubing is substantially concentric with respect to the production tubing.

An aspect combinable with any other aspect includes the following features. The perforated tubing is installed adjacent an inner surface of the production tubing.

An aspect combinable with any other aspect includes the following features. The perforated tubing is an elongate, cylindrical tubing.

An aspect combinable with any other aspect includes the following features. The perforated tubing is an elongate, helical tubing.

An aspect combinable with any other aspect includes the following features. The perforated tubing includes alternating portions of larger and smaller volumes arranged along an axis of the perforated tubing.

An aspect combinable with any other aspect includes the following features. The perforated tubing is a gas anchor or a dip tube.

Certain aspects of the subject matter described here can be implemented as a method performed in a wellbore formed in a subterranean zone to a subsurface reservoir in which multiphase hydrocarbons including a liquid phase and a gaseous phase are entrapped. The multiphase hydrocarbons flow from the subsurface reservoir through the wellbore. A separator is positioned at a downhole location in the wellbore. A portion of the gaseous phase is separated from the liquid phase before flowing into the separator through the intake resulting in multiphase hydrocarbons with reduced gaseous phase. A production tubing is fluidically coupled to the separator. The production tubing extends to the surface and can flow the multiphase hydrocarbons with reduced gaseous phase received via the intake to the surface. A gas ventilation system including a one-way check valve is fluidically coupled to the production tubing. The gas ventilation system can receive the multiphase hydrocarbons with reduced gaseous phase, further separate gaseous phase in the multiphase hydrocarbons with the reduced gaseous phase, and flow gaseous phase in the multiphase hydrocarbons with reduced gaseous phase received through the intake into an annulus defined between the production tubing and an inner wall of the wellbore.

An aspect combinable with any other aspect includes the following features. The wellbore includes a substantially vertical portion and a deviated portion extending from a downhole end of the substantially vertical portion through the subterranean zone. The wellbore includes a bend connecting the substantially vertical portion to the deviated portion. When positioning the separator at the downhole location, the separator is positioned in the bend.

Certain aspects of the subject matter described here can be implemented as a method performed in a wellbore formed in a subterranean zone to a subsurface reservoir in which multiphase hydrocarbons including a liquid phase and a gaseous phase are entrapped. The multiphase hydrocarbons flow from the subsurface reservoir through the wellbore. The multiphase hydrocarbons are flowed into a gas separator positioned at a downhole location in the wellbore. The gas separator separates a portion of the gaseous phase from the liquid phase in multiphase hydrocarbons with reduced gaseous phase. The multiphase hydrocarbons with the reduced gaseous phase are flowed through a production tubing fluidically coupled to the gas separator and extending to the surface. The production tubing defines an annulus with an inner wall of the wellbore. In a perforated tubing installed downstream of the gas separator and fluidically coupled to the production tubing, the portion of the multiphase hydrocarbons with the reduced gaseous phase are received. The perforated tubing further separates gaseous phase from the portion of the multiphase hydrocarbons with the reduced gaseous phase. The one-way check valve flows the gaseous phase separated by the perforated tubing.

An aspect combinable with any other aspect includes the following features. The wellbore includes a substantially vertical portion and a deviated portion extending from a downhole end of the substantially vertical portion through the subterranean zone. The wellbore includes a bend connecting the substantially vertical portion to the deviated portion. When positioning the separator at the downhole location, the separator is positioned in the bend.

DETAILED DESCRIPTION

This disclosure describes a downhole gas ventilation system (DGVS) that includes a mandrel (or piping or tubing) coupled with a dip tube, gas anchor or smaller tubing with openings for liquids to enter and a one-way check valve. When the DGVS is positioned in the flow path of a multiphase hydrocarbon stream, the DGVS creates fluid isolation between upstream and downstream fluid, which enables separation between the liquid and gaseous phases. As described below, the gaseous phase is removed via the check valve allowing higher liquid phase to flow towards the surface or towards an inlet of a downhole pump installed in a wellbore to flow the hydrocarbons through the wellbore towards the surface.

FIG.1is a schematic diagram of a downhole gas ventilation system (DGVS)100. Specifically,FIG.1shows an implementation of the DGVS100installed in a production tubing102, which, in turn, is installed within a wellbore104formed from a surface (not shown) to a subsurface reservoir (not shown). The wellbore104can be uncased or cased with a casing106installed within the wellbore104. The casing106and the production tubing102define an annulus108.

In some implementations, the DGVS100includes a perforated tubing110that is positioned within the production tubing102. For example, the perforated tubing110can be a dip tube or a gas anchor. An outer diameter of the perforated tubing110is smaller than that of the production tubing102so that the perforated tubing110can fit entirely within the production tubing102. The perforated tubing110has an upper end112, a lower end114and a sidewall116connecting the upper end112and the lower end114. Multiple perforations (e.g., the perforation118) are formed on the sidewall116of the perforated tubing110. Each perforation is a hole, a slit, a radial slot, a radial port (or any combination of them or similar perforations) that extends through the sidewall116. Each perforation is large enough to permit the multiphase hydrocarbons to enter into an inner volume of the perforated tubing110through the multiple perforations.

An outer diameter of the upper end112is at least equal to an inner diameter of the production tubing102. Consequently, when the perforated tubing110is installed within the production tubing102, the upper end112seals against the inner diameter of the production tubing102. Any fluid that flows into an annular space between the production tubing102and the perforated tubing110cannot flow around or flow past the upper end112, and is forced to enter the inner volume of the perforated tubing110through the multiple perforations. The uphole end112is fluidically coupled to wellbore equipment uphole of (i.e., downstream of) the upper end112such that fluid that flows into the inner volume of the perforated tubing110flows downstream into the wellbore equipment.

A one-way check valve120is fluidically coupled to the upper end112of the perforated tubing110. Alternatives or additions to the one-way check valve120include a relief valve, a back pressure valve, or any orifice or opening that permits gas to pass from within the perforated tubing110to outside the perforated tubing110. In some implementations, the check valve112is attached directly to the upper end112or to the sidewall116near the upper end112of the perforated tubing110.

In some implementations, the perforated tubing110and the check valve112are each mounted to wellbore equipment122, which is then connected to the production tubing102. For example, as shown in the schematic inFIG.1, the wellbore equipment112includes a mandrel122(e.g., a tubing) that is separate from and removably connected to the production tubing102. In particular, the mandrel122can be a gas lift mandrel that includes a gas lift valve fluidically coupled to the production tubing102. In such implementations, the perforated tubing110can be mechanically coupled to the wellbore equipment112, for example, by direct welding, using threads or otherwise. The coupling is such that multiphase hydrocarbons can flow both from the production tubing102and from the perforated tubing110through the wellbore equipment122towards the surface of the wellbore104. The check valve120can be installed on an inner side wall of the wellbore equipment122. In such installations, one end of the check valve120resides within the wellbore equipment122and the other end opens to the annulus108. An outer diameter of the wellbore equipment122can be the same as or greater than an outer diameter of the production tubing102. In implementations in which the outer diameter of the wellbore equipment122is greater than that of the production tubing102and less than that of the wellbore104, the check valve120can be installed on a portion of the wellbore equipment122that radially extends into the annulus108. In implementations with the wellbore equipment122, the wellbore equipment122can seal to the inner diameter of the production tubing102to prevent downstream flow of the multiphase hydrocarbons through the annular space between the production tubing102and the perforated tubing110, thereby forcing the multiphase hydrocarbons to flow into the inner volume defined by the perforated tubing110.

In some implementations, the DGVS100includes a seating nipple124to which the perforated tubing110can be connected, for example, by direct welding, using threads or otherwise. Alternatively, the seating nipple124can be screwed on top of the mandrel122, e.g., the gas lift mandrel with the check valve120. The seating nipple124can be any wellbore coupling equipment (e.g., a piece of tubing) that can facilitate a coupling between the perforated tubing110and equipment uphole of the perforated tubing110, for example, additional tubing that extends to the surface or connects to an intake of a pump (not shown). On one end, the seating nipple124attaches to the upper end112of the perforated tubing110. On the opposite end, the seating nipple124can attach to the wellbore equipment122, for example, the mandrel. The seating nipple124resides uphole of the perforated tubing110.

In an example operation, the DGVS100is mounted to the production tubing102, which is installed within the wellbore104. A downhole end of the production tubing102extends to the subsurface reservoir in which the multiphase hydrocarbons are entrapped. The liquid phase (schematically shown inFIG.1by solid black circles) and gaseous phases (schematically shown inFIG.1by black circles with cross hatches) of the multiphase hydrocarbons flow into the production tubing102at the downhole end and flow through the production tubing102towards the surface. Downstream from (i.e., uphole of) the downhole end of the production tubing102, the multiphase hydrocarbons flow towards the perforated tubing110and, through the multiple perforations118, into an inner volume of the perforated tubing110. The upper end112of the perforated tubing102forms a seal that prevents downstream flow of the multiphase hydrocarbons in the annular space defined by the production tubing102and the perforated tubing110. In implementations with the wellbore equipment122(e.g., the mandrel), the wellbore equipment122forms the seal. Consequently, the multiphase hydrocarbons is forced to flow into the inner volume of the perforated tubing110.

The positioning of the perforated tubing110in the flow pathway of the multiphase hydrocarbons causes an isolation between upstream and downstream fluid. The isolation improves separation of the liquid phase from the gaseous phase, for example, due to gravimetric separation. The separated gaseous phase (schematically shown inFIG.1by hollow black circles) flows past the perforated tubing110towards the check valve120into the annulus108. The multiphase fluid that flows past the perforated tubing110and towards the check valve120has a higher gaseous fraction compared to the multiphase fluid upstream of the perforated tubing110. The multiphase fluid with higher liquid fraction flows into the perforated tubing110through the perforations118and into the production tubing102that is fluidically coupled to the perforated tubing110.

Due to the separation of the gaseous phase from the liquid phase, the hydrocarbons that flow through the production tubing102(or other flow tubing) downstream of the perforated tubing110has a higher liquid fraction compared to the hydrocarbons upstream of the perforated tubing110. In implementations in which a pump is installed downstream of the perforated tubing110, the hydrocarbons with the higher liquid fraction will enter a pump intake and be pumped to the surface. By reducing a quantity of gaseous phase that enters the pump intake, pump efficiency can be improved.

FIG.2is a schematic diagram of another implementation of the downhole gas ventilation system (DGVS)200. The DGVS200can be fluidically coupled to the production tubing102. The DGVS200includes substantially similar features as the DGVS100, e.g., a perforated tubing210, an upper end212of the perforated tubing210, a lower end214of the perforated tubing210, multiple perforations218on a sidewall216of the perforated tubing210, and a check valve220. The DGVS200is designed and constructed such that the perforated tubing210is substantially concentric with respect to the production tubing102. In other words, the perforated tubing210is installed at a center of the production tubing102. When installed, the perforated tubing210and the production tubing102define an annular space that surrounds all sides of the perforated tubing210. In addition, the DGVS200excludes the seating nipple124. Instead, the upper end212of the perforated tubing210attaches directly to a mandrel or other flow equipment (e.g., tubing) that is uphole of the DGVS200. The check valve220is downhole of (i.e., upstream of) the upper end212. The upper end212seals against the inner diameter of the production tubing102, thereby forcing the multiphase hydrocarbons to enter the inner volume of the perforated tubing210through the multiple perforations218formed on the sidewall216.

FIG.3is a schematic diagram of another implementation of the downhole gas ventilation system (DGVS)300. The DGVS300can be fluidically coupled to the production tubing102. The DGVS300includes substantially similar features as the DGVS200, e.g., a perforated tubing310, an upper end312of the perforated tubing310, a lower end314of the perforated tubing310, multiple perforations318on a sidewall316of the perforated tubing310, and a check valve320. The DGVS300is designed and constructed such that the perforated tubing310is substantially eccentric with respect to the production tubing102. In other words, the perforated tubing310is installed away from a center of the production tubing102, such as against an inner sidewall of the production tubing102or in a space in between the inner side wall and the center of the production tubing102.

In such implementations, baffle plates are installed within the production tubing102adjacent the perforated tubing310. For example, a horizontal plate322is installed uphole of the lower end314of the perforated tubing314. An end of the horizontal plate322extends to the inner wall of the production tubing102. The other end of the horizontal plate322extends away from the inner wall of the production tubing102past the lower end314of the perforated tubing314. A vertical plate324is attached to the horizontal plate324, specifically to the other end of the horizontal plate322, with the other end of the vertical plate324being a free end. The baffle plates are sized such that the multiple perforations (or at least a portion of the perforations) are downhole of the free end of the vertical plate324. Such an arrangement creates a flow path for the multiphase fluids in a downhole direction as shown by the arrow324. The multiphase hydrocarbons flow past the baffle plates and into the multiple perforations318in the sidewall316of the perforated tubing310. The check valve320is downhole of (i.e., upstream of) the upper end312. The upper end312seals against the inner diameter of the production tubing102, thereby forcing the multiphase hydrocarbons to enter the inner volume of the perforated tubing310through the multiple perforations318formed on the sidewall316. In some implementations, the DGVS300can be implemented with the seated nipple124(FIG.1).

FIG.4is a schematic diagram of another implementation of the downhole gas ventilation system (DGVS)400. The DGVS400can be fluidically coupled to the production tubing102. The DGVS400includes a spiral tubing410coupled to a straight tubing411. The spiral tubing410includes an upper end412and a lower end414. When installed within the production tubing102, the lower end414can be an inlet to receive the multiphase hydrocarbons including the liquid and gaseous phases. The multiphase hydrocarbons flow through the spiral pathway of the spiral tubing410. The spiral pathway includes perforations418that facilitates separation of the gaseous and liquid phases. As the multiphase fluid flows through the spiral, the gaseous phase will have a tendency to be on the inner diameter of the spiral while the liquid (heavier) hydrocarbons will be on the outer portion of the spiral. The gaseous rich hydrocarbons will flow through perforations418while the liquid heavier will remain on the outer portion of the spiral to continue flowing upwards towards the upper end of the spiral tubing412. A check valve420can be fluidically coupled to the inner diameter of411allowing the separated gaseous phase to vent through the check valve420unto the annulus (not shown inFIG.4). In some implementations, a housing416can be installed within the production tubing102, and the spiral tubing410and the straight tubing411can be installed within the housing416. In addition to housing the tubings, the housing416seals against the inner diameter of the production tubing102forcing fluid to flow into the spiral tubing410. In such implementations, the lower end414can reside downhole of (i.e., upstream of) the housing416, and the upper end412can reside uphole of (i.e., downstream of) the housing416.

FIG.5is a schematic diagram of another implementation of a perforated tubing510for use with a downhole gas ventilation system (DGVS), for example, the DGVS100,200or300. Like the perforated tubing110(FIG.1) of the DGVS100(FIG.1), the perforated tubing510includes an elongate body with a cylindrical cross-section. In addition, the perforated tubing512defines spiral or helical grooves512around an outer surface of the perforated tubing512. The grooves512facilitate greater separation of the gaseous phase before exiting the check valve (not shown). At least some of the perforations can be formed on the grooves512.

FIG.6is a schematic diagram of another implementation of a perforated tubing600for use with a downhole gas ventilation system (DGVS), for example, the DGVS100,200or300. The perforated tubing610includes regions of varying volume across an axial length of the perforated tubing610. For example, the perforated tubing610includes alternating portions of larger volumes (e.g., a portion612) and smaller volumes (e.g., a portion614) arranged along an axis of the perforated tubing. The variation in volume across the length of the perforated tubing610creates extra pressure drop to allow more free gas to escape to the annulus via the check valve (not shown).

FIG.7is a schematic diagram showing a deployment of a downhole gas ventilation system in a wellbore700with a deviated portion. The DGVS schematically shown inFIG.7can be any of the DGVS' described in this disclosure with reference toFIGS.1-4and can include any of the perforated tubings described in this disclosure with reference toFIGS.1-6. The wellbore700includes a vertical portion702that extends from a surface (not shown) through a subterranean zone. The wellbore700includes a deviated portion704(e.g., a horizontal portion or any length of a wellbore that is offset from the vertical). The operations of the DGVS are described with reference to a wellbore700that includes vertical and deviated portions, but can be implemented in a wellbore with only a vertical portion or in multi-lateral wells with only vertical or vertical and horizontal portions.

The multiphase hydrocarbons, which includes liquid phase (schematically shown in solid black inFIG.7) and gaseous phase (schematically shown as black circles inFIG.7), flow from the subsurface reservoir (not shown) through the deviated portion704, through the vertical portion702and towards the surface. A production tubing706(for example, one substantially similar to the production tubing102) can be installed within the wellbore700. The production tubing706extends from the surface (not shown) of the wellbore700through the vertical portion702and into a bend708at which the downhole end of the vertical portion702connects with an entrance to the deviated portion704. The production tubing706can be made up of multiple lengths of tubing that are of same or different diameters. A tubing anchor catcher (TAC)710can be used to support certain lengths of tubing installed downhole in the wellbore700.

In some implementations, a downhole end of the production tubing706, which is positioned at a downhole location (e.g., in the vertical portion702, in the horizontal portion704or in the bend708) can serve as an intake into which the multiphase hydrocarbons flows to enter the production tubing706. That is, the production tubing706can receive the multiphase hydrocarbons directly and without any intermediate well component.

In some implementations, a gas separator712can be fluidically coupled to the downhole end of the production tubing706. The gas separator712includes an intake714to receive the multiphase hydrocarbons. The gas separator712can facilitate separation of the liquid phase and the gaseous phase, for example, by gravimetric separation. For example, the flow direction of the multiphase hydrocarbons can be reversed (e.g., from uphole direction to downhole direction) within the gas separator712causing the gaseous phase to rise in the uphole direction and the liquid phase to fall in the downhole direction, resulting in a separation of the two phases.

The gas separator712can be installed at a downhole location within the wellbore702. For example, the gas separator712can be installed in the vertical portion702. In some implementations, the gas separator712can be installed in the bend708. As the multiphase hydrocarbons flow into the bend708, at least a portion of the liquid and gaseous phases are gravimetrically separated resulting in multiphase hydrocarbons with reduced gaseous phase (i.e., higher liquid fraction) to enter the intake714of the gas separator712. Gaseous phase continues to rise towards the surface through an annulus716defined by the production tubing706and the wellbore700.

The DGVS100(or any of the other DGVS' described in this disclosure with any of the perforated tubings described in this disclosure) can be installed in the vertical portion702downstream of (i.e., uphole of) the gas separator712. In implementations without a gas separator712, the DGVS100can be installed downstream of the intake into the production tubing706. In any implementation, multiphase hydrocarbons flow towards the DGVS100, which separates at least a portion of the gaseous phase from the liquid phase, and releases the separated gaseous phase into the annulus716through the check valve included in the DGVS100.

The phase separation within the DGVS100and release of the gaseous phase through the check valve is aided by several flow conditions. For example, a specific gravity of the multiphase hydrocarbons in the production tubing706is different from the specific gravity of the fluids (e.g., the gaseous phase) in the annulus716. The difference in specific gravities creates a pressure differential within the DGVS100. In another example, in implementations that include the gas separator712, the removal of a portion of the gaseous phase from the multiphase hydrocarbons by the gas separator712creates a pressure differential within the DGVS100. In a further example, in implementations in which the DGVS100has a greater diameter than the production tubing706such that the DGVS100extends radially into the annulus716, the distance between the outer surface of the DGVS100and the inner wall of the wellbore700is less than the distance between the outer surface of the production tubing706and the inner wall of the wellbore700. The reduced distance creates a venturi effect as the free gas that rises through the annulus716flows past the DGVS100. Each of the pressure differentials or the venturi effect or any combination of them aid in the gas separation within the DGVS100and release of the separated gas by the check valve into the annulus716.

FIG.8is a schematic diagram showing a deployment of stages (for example, a first stage100, a second stage802a, a third stage802b) of downhole gas ventilation systems in a wellbore with a deviated portion. The wellbore schematically shown in and described with reference toFIG.8can be identical to that shown in and described with reference toFIG.7. In addition to the DGVS100shown in and described with reference toFIG.7, multiple DGVS' can be implemented as multiple stages in the wellbore700. For example, a DGVS can be implemented as a first stage802adownhole of (i.e., upstream of) of the DGVS100. Another DGVS can be implemented as a second stage802bdownhole of the first stage802a. Additional DGVS' can be implemented at different locations uphole or downhole of the DGVS100. The multiphase hydrocarbons can flow through each stage in which the gaseous phase can be separated and released into the annulus716. By deploying multiple DGVS in multiple stages, more gaseous phase can be removed from the multiphase hydrocarbons produced through the wellbore700.

FIG.9is a flowchart of an example of a process900of separating gaseous phase from multiphase hydrocarbons using a DGVS. For example, the process900can be implemented by an operator of the equipment described in this disclosure and/or an operator of any of the DGVS' described in this disclosure. The process900can be implemented in a wellbore formed in a subterranean zone to a subsurface reservoir in which multiphase hydrocarbons that include a liquid phase and a gaseous phase are entrapped. The multiphase hydrocarbons flow from the subsurface reservoir through the wellbore. For example, the wellbore can be the wellbore108(FIG.1) or the wellbore700(FIGS.7,8). At902, a separator is positioned at a downhole location in the wellbore. For example, the well operator can lower the gas separator to any downhole location within the wellbore, e.g., within a vertical portion or within a deviated portion or at a bend that connects the vertical portion and the deviated portion. The gas separator separates a portion of the gaseous phase from the liquid phase. In some implementations (e.g., implementations in which the gas separator is positioned in the bend), a portion of the gaseous phase can be separated from the liquid phase before the multiphase hydrocarbons flow into the gas separator.

At904, a production tubing is fluidically coupled to the separator. For example, the operator can couple the production tubing to the separator and lower both into the wellbore. The production tubing is configured to flow the multiphase hydrocarbons to the surface. In some implementations, the gas separator need not be used, and the production tubing alone can be lowered into the wellbore. In such implementations, a downhole end of the production tubing serves as the intake for the multiphase hydrocarbons.

At906, a gas ventilation system (e.g., a DGVS) is fluidically coupled to the production tubing. For example, the DGVS can be coupled to the production tubing at the surface of the wellbore, and the production tubing and the DGVS can be lowered into the wellbore. As described earlier, the DGVS receives the multiphase hydrocarbons, separates the gaseous phase from the multiphase and flows the gaseous phase into an annulus defined between the production tubing and an inner wall of the wellbore. The fluid that is flowed into the annulus after the separation can include liquid phase, but the liquid fraction in such multiphase fluid is smaller than the liquid fraction upstream of the DGVS. At908, hydrocarbons are produced through the production tubing and the DGVS.

FIG.10is a flowchart of an example of a process1000of operating the DGVS. For example, the process100can be implemented by the wellbore equipment disclosed in this disclosure including the DGVS. The process1000can be implemented in a wellbore formed in a subterranean zone to a subsurface reservoir in which multiphase hydrocarbons that include a liquid phase and a gaseous phase are entrapped. The multiphase hydrocarbons flow from the subsurface reservoir through the wellbore. For example, the wellbore can be the wellbore108(FIG.1) or the wellbore700(FIGS.7,8). At1002, multiphase hydrocarbons are flowed into a gas separator positioned at a downhole location in the wellbore. In some implementations, the gas separator is fluidically coupled to the production tubing. In some implementations, a gas separator is not used and the multiphase hydrocarbons flow directly into a downhole end of a production tubing. In implementations involving a wellbore with a vertical portion and a deviated portion, the downhole end of the production tubing or the gas separator is positioned at the bend so that a portion of the gaseous phase is removed from the multiphase hydrocarbons before the multiphase hydrocarbons flow into the intake, either of the production tubing or the gas separator.

At1004, the gas separator separates a portion of the gaseous phase from the liquid phase. In implementations in which the gas separator is positioned in the bend connecting the vertical portion and the horizontal portion, the gas separator separates a portion of the gaseous phase from the liquid phase that already has a reduced gaseous phase.

At1006, a production tubing fluidically coupled to the gas separator and extending to the surface flows the multiphase hydrocarbons with the reduced gaseous phase. The production tubing defines an annulus with an inner wall of the wellbore.

At1008, a perforated tubing of the DGVS, which is installed downstream of the gas separator and is fluidically coupled to the production tubing, receives the portion of the multiphase hydrocarbons with the reduced gaseous phase. At1010, the perforated tubing further separates gaseous phase from the multiphase hydrocarbons received by the perforated tubing. At1012, the check valve in the DGVS flows the separated gaseous phase into the annulus. The liquid phase flows through the production tubing towards the surface, e.g., towards a pump installed downstream of the DGVS. The multiphase fluid that flows through the perforated tubing of the DGVS into the annulus has a higher gaseous fraction compared to the multiphase fluid upstream of the DGVS. Conversely, the liquid phase that flows through the production tubing downstream of the DGVS has a higher liquid fraction compared to the multiphase fluid upstream of the DGVS.

Thus, particular implementations of the subject matter have been described. Other implementations are within the scope of the following claims.