Check valve for well stimulation

Check valve assemblies operable to inject treatment fluids during stimulation operations are described. One check valve assembly includes a valve body defining an inlet, one or more discharge ports, and a cylindrical passageway fluidly communicating the inlet with the one or more discharge ports, the valve body further defining a valve body seat within the passageway. A valve cap is configured to be coupled to the valve body and defines an opening therein that fluidly communicates with the cylindrical passageway, the valve cap further providing a valve cap seat. A spherical piston is disposed within the passageway and movable between a closed configuration where the spherical piston engages the valve body seat and an open configuration where the spherical piston engages the valve cap seat and allows fluid communication between the inlet and the one or more discharge ports.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a National Stage entry of and claims priority to International Application No. PCT/US2012/045365 filed on Jul. 3, 2012.

BACKGROUND

The present invention relates to equipment utilized in subterranean well operations and, more particularly, to check valve assemblies operable to inject treatment fluids during stimulation operations while preventing inflow of production fluids.

In the course of drilling and construction of wellbores that traverse hydrocarbon bearing formations, it is oftentimes desirable to inject treatment fluids into the wellbore for a number of purposes. For example, hydrochloric acid solutions are often injected into the wellbore to stimulate the hydrocarbon bearing formation. In such cases, the hydrochloric acid solution can be injected into the subterranean formation to react with acid-soluble materials disposed in the formation, thereby enlarging pore spaces in the formation. These acidizing treatments are designed to improve the formation permeability, which consequently enhances production of reservoir fluids. Typically, such acidizing operations are performed at a high flowrate, but at a treatment pressure below the fracture pressure of the formation such that the acid is able to penetrate an extended distance into the formation without damaging the formation.

Attempts have been made to inject treatment fluids as reverse flow through conventional inflow control devices that utilize one or more flow restrictors such as flow tubes, nozzles, labyrinths, or the like. Inflow control devices are often used to control the rate of fluid inflow into a production casing and generally feature a dual-walled tubular housing with one or more inflow passages laterally disposed through the inner wall of the housing. A sand screen often surrounds a portion of the tubular housing, and production fluid can enter the sand screen and then negotiate, for example, a tortuous pathway between the dual walls to reach the inflow passages. The tortuous pathway serves to slow the rate of flow and maintain it in an even manner.

It has been found, however, that the flowrate required for acidizing operations is typically higher than the production flowrate from the formation. As such, reverse flow through conventional inflow control devices can result in an unacceptably high pressure drop in the treatment fluid. Accordingly, a need has arisen for an apparatus that is operable to enable injection of a treatment fluid into the wellbore and the surrounding formation. A need has also arisen for such an apparatus that is operable to enable injection of the treatment fluid at a high flowrate. Further, a need has also arisen for such an apparatus that is operable to enable injection of the treatment fluid without an unacceptably high pressure drop.

SUMMARY OF THE INVENTION

The present invention relates to equipment utilized in subterranean well operations and, more particularly, to check valve assemblies operable to inject treatment fluids during stimulation operations while preventing inflow of production fluids.

In some embodiments, a check valve assembly is disclosed. The check valve assembly may include a valve body defining an inlet, one or more discharge ports, and a cylindrical passageway fluidly communicating the inlet with the one or more discharge ports, the valve body further defining a valve body seat within the passageway; a valve cap configured to be coupled to the valve body and defining an opening therein that fluidly communicates with the cylindrical passageway, the valve cap further providing a valve cap seat; and a spherical piston disposed within the passageway and movable between a closed configuration where the spherical piston engages the valve body seat to prevent fluid communication between the inlet and the one or more discharge ports and an open configuration where the spherical piston engages the valve cap seat and allows fluid communication between the inlet and the one or more discharge ports.

In other embodiments, another check valve assembly is disclosed. The check valve assembly may include a valve body defining an inlet, one or more discharge ports, and a cylindrical passageway fluidly communicating the inlet with the one or more discharge ports, the valve body further defining a valve body seat within the passageway; a valve cap configured to be coupled to the valve body and defining an opening therein that fluidly communicates with the cylindrical passageway, the valve cap further providing a valve cap seat; a piston disposed within the passageway and movable between a closed configuration where the piston engages the valve body seat to prevent fluid communication between the inlet and the one or more discharge ports and an open configuration where the piston engages the valve cap seat and allows fluid communication between the inlet and the one or more discharge ports; and a magnet arranged within the valve body and configured to bias the piston toward the closed configuration.

In yet other embodiments, a method for regulating the injection of a stimulation fluid into a subterranean formation is disclosed. The method may include arranging a base pipe within the subterranean formation, the base pipe having a check valve assembly arranged therewith, the check valve assembly having a valve body defining an inlet, one or more discharge ports, and a cylindrical passageway fluidly communicating the inlet with the one or more discharge ports, the check valve assembly further having a piston movably disposed within the passageway; magnetically-attracting the piston into engagement with a valve body seat defined in the passageway such that the piston is biased to a closed configuration that prevents fluid communication between the inlet and the one or more discharge ports; and injecting the stimulation fluid into the base pipe at a rate sufficient to induce the piston to move between the closed configuration and an open configuration where the piston engages a valve cap seat defined in a valve cap coupled to the valve body and defining an opening therein, the opening providing fluid communication between the cylindrical passageway and the subterranean formation.

The features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of the preferred embodiments that follows.

DETAILED DESCRIPTION

The present invention relates to equipment utilized in subterranean well operations and, more particularly, to check valve assemblies operable to inject treatment fluids during stimulation operations while preventing inflow of production fluids.

The exemplary check valve assemblies and methods of using the same disclosed herein may advantageously enhance well stimulation operations. For example, the exemplary check valve assemblies may be operable to enable injection of a treatment fluid into the wellbore and the surrounding formation. In addition, the exemplary check valve assemblies may be operable to enable injection of the treatment fluid at a high flowrate, but simultaneously without an unacceptably high pressure drop. Moreover, the exemplary check valve assemblies are designed to operate autonomously, that is, the check valve assemblies can switch between open and closed configurations as needed to control the injection of stimulation fluid without constant monitoring by a user, for example. As a result, the assemblies provide a simplified means of stimulating subterranean hydrocarbon bearing formations.

FIG. 1schematically illustrates a well system10including a plurality of injection assemblies embodying one or more aspects of the present disclosure. In the illustrated embodiment, a wellbore12extends through the various earth strata and has a substantially vertical section14, the upper portion of which has cemented therein a casing string16. The wellbore12also has a substantially horizontal section18that extends through a hydrocarbon bearing subterranean formation20. As illustrated, the substantially horizontal section18of the wellbore12may be arranged in an open hole portion of the wellbore12. In other embodiments, however, the horizontal section18be arranged in a completed portion of the wellbore12, with appropriate perforations defined in the casing string16and accompanying cement, without departing from the scope of the disclosure.

Positioned within the wellbore12and extending from the surface is a tubing string22. The tubing string22provides a conduit for formation fluids to travel from the formation20to the surface. At its lower end, the tubing string22is coupled to a completion string24that has been installed in the wellbore12and divides the completion interval into various production intervals adjacent the formation20. The completion string24includes a plurality of sand control screen assemblies26and a plurality of injection assemblies28. In addition, the completion string24includes a plurality of packers30that provides fluid seals between the completion string24and the wellbore12, thereby defining the various production intervals.

The sand control screen assemblies26primarily serve to filter particulate matter (e.g., sand and fines) out of the production fluid stream. The migration of particulate matter into the wellbore12or near-wellbore area can severely restrict production. In some applications, the sand control screen assemblies26may include one or more inflow control devices configured to control the flowrate of the production fluid stream into the completion string24. An exemplary inflow control device may utilize one or more flow restrictors such as flow tubes, nozzles, labyrinths, or the like, to control the production flowrate. Moreover, however, in certain completions, it may also be desirable to stimulate the formation20to improve permeability, which can enhance production of reservoir fluids. In one type of stimulation operation, acid, such as a hydrochloric acid solution, may be injected into the formation20via the inflow control devices at a flowrate significantly higher than the design production flowrate. Such reverse flow through the inflow control devices may result in an unacceptably high pressure drop in the treatment fluid.

In order to avoid unacceptably high pressure drop in the treatment fluid, the well system10may further include one or more injection assemblies28that may be positioned within each production interval. As will be described in more detail below, in operation the injection assemblies28may be configured to undertake stimulation operations capable of uniformly treating the formation20by injecting the desired treatment fluid at the desired high flowrate, and without experiencing an unacceptably high pressure drop.

It should be noted that whileFIG. 1depicts the injection assemblies28in an open hole environment, the injection assemblies28are equally well suited for use in cased wells. Moreover, whileFIG. 1depicts one sand control screen assembly26and one corresponding injection assembly28arranged in each production interval, those skilled in the art will readily recognize that any number of sand control screen assemblies26and any number of injection assemblies28in any ratio relative to each other may be deployed within a particular production interval without departing from the scope of the disclosure. In addition, even thoughFIG. 1depicts multiple production intervals separated by packers30, the completion interval may have any number of production intervals including a single interval with a corresponding number of packers30or no packers30.

Furthermore, even thoughFIG. 1depicts the injection assemblies28as arranged in the horizontal section18of the wellbore12, it should be understood by those skilled in the art that the injection assemblies28are equally well suited for use in wells having other directional configurations including vertical wells, deviated wells, slanted wells, multilateral wells and the like. Accordingly, it should be understood by those skilled in the art that the use of directional terms such as above, below, upper, lower, upward, downward, left, right, uphole, downhole and the like are used in relation to the illustrative embodiments as they are depicted in the figures, the upward direction being toward the top of the corresponding figure and the downward direction being toward the bottom of the corresponding figure, the uphole direction being toward the surface of the well and the downhole direction being toward the toe of the well.

Referring now toFIGS. 2A and 2B, illustrated are schematic representations of an exemplary completion string assembly35, according to one or more aspects of the disclosure. As shown, the completion string assembly35includes a base pipe40, one or more check valve assemblies42, and one or more inflow control devices44. While the illustrated embodiment shows a specific number of check valve assemblies42and inflow control devices44, it should be understood that any number of check valve assemblies42and/or inflow control devices44may be used, without departing from the scope of the disclosure. The completion string assembly35can form zonal isolations46when the completion string assembly35is placed in a well (e.g., the wellbore12ofFIG. 1) in order to prevent cross-flow of fluids during well production operations.

In particular,FIG. 2Aillustrates the flow direction (see arrows) of a stimulation treatment fluid during an exemplary well stimulation phase of a drilling operation. The direction of fluid flow is primarily determined by the difference between pressure inside of base pipe40and outside pressure; i.e., the pressure of the formation20(FIG. 1). In the embodiment shown inFIG. 2A, the pressure inside of the base pipe40is greater than the formation pressure during stimulation operations. The pressure inside of the base pipe40may be applied, for example, by a pump located at the surface which is used to inject the stimulation fluid into the base pipe40. The stimulation fluid travels downhole through the base pipe40and is eventually released into the formation20(FIG. 1) through the injection assemblies42and/or the inflow control devices44.

FIG. 2Billustrates the direction of the production fluid flow during an exemplary well production phase of a drilling operation. In the embodiment shown, the pressure of the formation20(FIG. 1) is greater than the pressure inside of base pipe40and therefore the production fluid is able to flow into the base pipe40. Those skilled in the art will recognize that this pressure differential is normal in the absence of a substantial external pressure applied downhole. As shown, this pressure differential forces the one or more check valve assemblies42to remain closed during well production, thus causing the production fluid from the formation20to enter into the base pipe40solely or primarily through the inflow control devices44.

Referring now toFIG. 3, illustrated is an exemplary injection assembly50used for well stimulation operations, according to one or more embodiments of the disclosure. As shown, the injection assembly50may include a base pipe52that defines one or more openings54where one or more corresponding check valve assemblies66may be seated or otherwise arranged. The injection assembly50may further include an upper connection assembly56and a lower connection assembly58disposed about the base pipe52and securably attached thereto by welding or other suitable means. The lower connection assembly58may define a plurality of channels60that provides a path for fluid injection from the injection assembly50and into the wellbore. Alternatively or additionally, the upper connection assembly56may provide a path for fluid injection from the injection assembly50and into the wellbore. An outer sleeve62may be coupled to both the upper and lower connection assemblies56,58at opposing ends of the injection assembly50.

In the illustrated embodiment, an insert ring64may be positioned within the opening54of the base pipe52. The insert ring64may be securably coupled within the opening54by welding, threading, or similar attachment techniques. In other embodiments, however, the insert ring64may be press-fit into the opening54and held in place with an interference fit. The insert ring64may have a inner diameter sized to receive and retain the check valve assembly66therein. In some embodiments, the insert ring64may include an extension (not pictured) designed to radially align the check valve assembly66and/or component parts thereof with the base pipe52such that any fluid discharged from the check valve assembly66is directed in the axial direction of the injection assembly50and not in the circumferential direction. As can be appreciated, such predetermined alignment of the check valve assembly66may substantially prevent erosion of the sleeve62. As illustrated, the sleeve62may have a close fitting relationship with the check valve assembly66which ensures that the check valve assembly66remains fixed in the insert ring64and the component parts of the check valve assembly66remain properly configured and oriented during operation.

Referring now toFIGS. 4A and 4B, illustrated are cross-sectional views of an exemplary check valve assembly100, according to one or more embodiments. The check valve assembly100may be similar in some respects to the check valve assembly66ofFIG. 3, and therefore may be best understood with reference thereto. Specifically,FIG. 4Adepicts the check valve assembly100in a closed configuration which restricts flow of fluid into the base pipe52(FIG. 3), andFIG. 4Bdepicts the check valve assembly in an open configuration which allows stimulation fluid to flow into the surrounding formation20(FIG. 1). In one or more embodiments, the check valve assembly100may include a valve body104that defines a cylindrical passageway106that leads to or is otherwise fluidly coupled to an inlet108. The inlet108may fluidly communicate with the interior of, for example, the base pipe52(FIG. 3). The valve body104may define or otherwise form a valve body seat110within the passageway106. In some embodiments, the inlet108may define a plurality of conduits that fluidly connect the passageway106with the base pipe52(FIG. 3).

A piston102may be movably disposed within the passageway106and generally free to move axially within the passageway106in order to control the injection of stimulation fluid into the surrounding formation20(FIG. 1). In one embodiment, the piston102may be a generally spherical ball, such as a ball bearing or the like. In other embodiments, however, the piston102may include other shapes such as, but not limited to, frustoconical, polygonal, ovoid, combinations thereof, or the like.

The valve body104may have a cylindrical section114configured to receive a valve cap112thereabout. In some embodiments, the valve cap112is mechanically fastened to the cylindrical section114such as by, but not limited to, welding, brazing, threadably engaging, combinations thereof, or the like. In other embodiments, the valve cap112may be press fit onto the cylindrical section such that an interference fit between the two components is generated, without departing from the scope of the disclosure. The valve cap112may define a central opening116and a valve cap seat118, and when the valve cap112is suitably coupled to the cylindrical section114, the central opening116may fluidly communicate with the passageway106and the valve cap seat118may engage or otherwise be in close contact with the cylindrical section114. The valve body104may also include an o-ring groove120operable to receive an o-ring (not shown) therein which provides a seal and support between the valve body104and the insert ring64(FIG. 3).

As shown, the valve body104may define a plurality of discharge ports122that extend radially from the passageway106. The discharge ports122may be in fluid communication with the inlet108via the passageway106. While only two discharge ports122are illustrated inFIGS. 4A and 4B, it will be appreciated that more than two discharge ports122may be employed, without departing from the scope of the disclosure. In one or more embodiments, one or more of the discharge ports122may be axially aligned with corresponding discharge ports124defined in the valve cap112and extending radially therethrough. As a result, the contiguously aligned discharge ports122,124defined in the valve body104and the valve cap112may provide fluid communication between the passageway106and the exterior of the check valve assembly100. In other embodiments, however, the valve cap112may be axially shorter, such that the discharge ports122provide direct fluid communication between the passageway106and the exterior of the check valve assembly100.

As illustrated, the discharge ports122may be oppositely disposed, and therefore may be referred to as a pair of oppositely disposed discharge ports122. It will be appreciated, however, that the valve cap112may have additional discharge ports122not particularly shown in the cross-sectional views ofFIGS. 4A and 4B. In some embodiments, the additional discharge ports may be angularly offset from the discharge ports122shown inFIGS. 4A and 4Bby about 90°. In other embodiments, however, the additional discharge ports may be angularly offset from the discharge ports122shown inFIGS. 4A and 4Bby angular configurations greater or less than 90° (e.g., 45°). As will be appreciated, this allows selective alignment of the discharge ports124defined in the valve cap112with the discharge ports122of the valve body104.

For example, when the discharge ports124are aligned with the discharge ports122, as shown inFIGS. 4A and 4B, flow through the additional (non-illustrated) discharge ports may be substantially prevented. In this manner, selective positioning of the valve cap112on the valve body104may determine which set of discharge ports122are available for flow which in turn may determine the resistance to flow encounter by the treatment fluid traveling through the check valve assembly100. In one or more embodiments, the discharge ports124defined in the valve cap112may have a flow area that is less restrictive than the flow area of the discharge ports122defined in the valve body104, which enables the adjustment of the flowrate and pressure drop of the treatment fluid through the check valve assembly100, as discussed in greater detail below.

Exemplary operation of the check valve assembly100will now be described. When the discharge ports124of the valve cap112are generally aligned with one or more of the discharge ports122of the valve body104, the check valve assembly100may be characterized as being in its more restrictive configuration. Prior to a stimulation operation, the piston102may be engaged with or otherwise seated on the valve body seat110. In this configuration, any pressure exhibited by the wellbore will communicate through the opening116of the valve cap112, which has the effect of biasing the piston102downwardly within the passageway106. The seal created between the piston102and valve body104(i.e., the valve body seat110) prevents fluid communication between the inlet108and the discharge ports122defined in the valve body104.

Once the stimulation operation commences, however, the piston102may be lifted off valve body seat110when the pressure inside of the check valve assembly100reaches a level sufficient to overcome the opposing wellbore pressure that holds the piston102against the valve body seat110. Once the piston102is lifted off the valve body seat110, the internal pressure of the check valve assembly100is now applied to a larger area on the piston102which means the pressure to maintain the check valve assembly100in the open configuration is less than the pressure required to open the check valve assembly100. As best seen inFIG. 4B, the piston102may travel upwardly (i.e., axially) in the passageway106until engaging the valve cap seat118and generally forming a seal therewith. In at least one embodiment, the piston102may be configured to be seated within or otherwise substantially occlude the central opening116. In this open configuration, the treatment fluid is able to enter the check valve assembly100via the inlet108and exit the check valve assembly100through the discharge ports122of the valve body102and the discharge ports124of the valve cap112.

In some embodiments, the pressure differential experienced across the check valve assembly100may act on the piston102such that the piston102may reside, at least temporarily, inside the passageway106without forming a seal with either the valve cap112or the valve body seat110, but is instead balanced between the two surfaces. Such a configuration can allow the stimulation fluid to exit into the formation20(FIG. 1) through the opening116defined in the valve cap112and/or through the injection ports122and124.

When the stimulation operation is complete, the internal pressure within the check valve assembly100may be reduced until it is no longer sufficient to overcome the opposing wellbore pressure. The piston102may then descend once again within the passageway106until reengaging the valve body seat110, as best seen inFIG. 4A. In this closed configuration, the production fluids are again generally prevented from entering the base pipe52(FIG. 3) through the check valve assembly100.

Referring now toFIGS. 5A and 5B, illustrated are cross-sectional views of another exemplary check valve assembly200, according to one or more embodiments of the disclosure. More particularly,FIG. 5Ashows a cross-sectional view of the check valve assembly200in the closed configuration, andFIG. 5Bshows a cross-sectional view of the check valve assembly200in the open configuration, thereby allowing free flow of stimulation fluids into the formation20(FIG. 1). The check valve assembly200may be best understood with reference toFIGS. 4A and 4B, where like numerals are used to indicate like elements. As with the check valve assembly100ofFIGS. 4A and 4B, the check valve assembly200may include the valve body104that defines the cylindrical passageway106. The valve body104may also define the inlet108. As shown inFIGS. 5A and 5B, the inlet108may be characterized or otherwise include one or more conduits202defined in the valve body104and configured to provide fluid communication between the passageway106and the interior of the base pipe52(FIG. 3). Each inlet conduit202may be arranged circumferentially about the bottom portion of passageway106and provide an angled configuration with respect to the central axis of the passageway106.

In some embodiments, a magnet204may be arranged within the valve body104adjacent the inlet108. For example, the magnet204may be seated within a recess206generally defined in the bottom portion of the valve body104. As illustrated, the inlet conduits202may extend through the valve body104about a radial periphery of the recess206, such that the inlet conduits202do not intersect any portion of the recess206but are otherwise arranged circumferentially about the periphery. In some embodiments, the magnet204may be a permanent magnet. In other embodiments, the magnet204may be an electromagnet configured to switch between magnetized and a non-magnetized modes of operation.

In at least one embodiment, the piston102may be made of a ferromagnetic material or otherwise attracted to the magnet204. The resulting magnetic attractive force applied on the piston102provides a downward force on piston102so that it is urged to engage or otherwise bias the valve body seat110. In other embodiments, portions of the valve body seat110may be magnetic and serve a similar purpose in magnetically attracting the piston102downwardly. The magnetic attractive force may be sufficient to maintain the piston102in the closed configuration (FIG. 5A) until the pressure differential experienced across the check valve assembly200overcomes the magnetic force.

Exemplary operation of the check valve assembly200will now be described. When the discharge ports114defined in the valve cap112are aligned with the discharge ports122of the valve body104, the check valve assembly200is in its more restrictive configuration. Prior to the stimulation operation, as best seen inFIG. 5A, the piston102may be engaged with the valve body seat110. In this configuration, the fluid pressure in the wellbore is able to communicate through the opening116defined in the valve cap112, which, along with any attractive force between piston102and the magnet204, urges the piston102downwardly. The mechanical seal created between the piston102and the valve body104prevents fluid communication between the inlet108and the discharge ports122.

Once the stimulation operation commences, the pressure within the base pipe502(FIG. 3) increases and serves to force the piston102off of the valve body seat110. For example, the fluid pressure applied for the stimulation operation is conducted to the passageway106through the one or more inlet conduits202of the inlet108and may eventually reaches a level sufficient to overcome the opposing wellbore pressure and attractive forces between the piston102and the magnet204. Once the piston102is lifted off the valve body seat110, the internal pressure of the check valve assembly100is then applied to a larger area on the piston102which means the pressure to maintain the check valve assembly200in the open configuration is less than the pressure required to open the check valve assembly200. As best seen inFIG. 5B, the piston102may be configured to translate upwardly within the passageway106until engaging the valve cap seat118, and forming a mechanical seal therewith. In at least one embodiment, the piston102may be configured to be seated within or otherwise substantially occlude the central opening116. In this configuration, the treatment fluid is able to enter the check valve assembly200via the inlet108and exit the check valve assembly200through the discharge ports122of the valve body202and the discharge ports114of the valve cap112.

In some embodiments, the pressure differential experienced across the check valve assembly200may act on the piston102such that the piston102may reside, at least temporarily, inside the passageway106without forming a mechanical seal with either the valve cap112or the valve body seat110, but is instead balanced between the two surfaces. Such a configuration can allow the stimulation fluid to exit into the formation20(FIG. 1) through the opening116defined in the valve cap112and/or through the injection ports122and124.

When the stimulation operation is complete, the internal pressure within the check valve assembly100may be reduced until it is no longer sufficient to overcome the combined opposing wellbore pressure and attractive force between the piston102and the magnet204. The piston102may then descend within the passageway106until once again engaging the valve body seat110, as best seen inFIG. 5A. In this closed configuration, the production fluids are again generally prevented from entering the base pipe52(FIG. 3) through check valve assembly200.