CLAIM OF PRIORITY

[0001] This application claims priority to U.S. Patent Application No. 62/434,756 filed on December 15, 2016, and U. S. Patent Application No. 15/626,455 filed on June 19, 2017, the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

[0002] This disclosure relates to wellbore tools, for example, pumps such as electric submersible pumps.

BACKGROUND

[0003] When a hydrocarbon reservoir is produced, a wellbore is drilled into the reservoir for production. Once this hydrocarbon well has been completed, it is sometimes necessary to utilize tools to boost production. The tools are placed either inside or outside of the wellbore. One such method for boosting production involves placing an electric submersible pump (ESP) within the wellbore.

SUMMARY

[0004] This disclosure relates to wellbore tools including smart materials.

[0005] Certain aspects of the subject matter described here can be implemented as an electric submersible pump utilized within a wellbore. The wellbore pump includes a pump housing, a pump stage positioned within the pump housing, the pump stage including a stationary diffuser and a rotating impeller positioned within the diffuser, the impeller rotates to provide kinetic energy to flow fluid through the wellbore pump, the diffuser converts the kinetic energy received from the rotating impeller to head to flow the fluid through the wellbore pump, a pump head attached to the first end of the pump housing, a compression tube attached between the pump head and the diffuser, the compression tube increasing a contacting force to prevent rotation of the diffuser with the impeller, and a ring-shaped memory material positioned around the diffuser, the memory material capable of reversibly expanding from a temporary state to a permanent state in response to wellbore operating conditions to form an interference fit with an inner surface of the pump housing during operation of the wellbore pump under the wellbore operating conditions.

[0006] The wellbore pump can also include a pump base attached at the second end of the pump housing. The wellbore pump can also include a lower diffuser spacer attached between the pump base and the diffuser. The ring-shaped memory material has a memory material inner surface that contacts an outer surface of the diffuser and a memory material outer surface that is at a distance from the inner surface of the pump housing. During the operation of the wellbore pump under the wellbore operating conditions, the ring-shaped memory material expands from the temporary state to the permanent state to at least the inner surface of the pump housing. The pump of any one of the previous claims, wherein the wellbore operating conditions comprises a wellbore operating temperature, wherein a wellbore pump temperature when the wellbore pump is not operating is lower than the wellbore operating temperature, wherein the ring-shaped memory material is in the temporary state at the wellbore pump temperature and is configured to return to the original state at the wellbore operating temperature. In the temporary state, a width of the ring-shaped memory material along a radius of the pump housing is less than a gap thickness between the inner surface of the pump housing and an outer surface of the diffuser. In the permanent state, the width of the ring-shaped memory material along the radius of the pump housing is equal to the gap thickness. The ring-shaped memory material is able to reversibly transition between the temporary state and the permanent state multiple times, without degradation as a temperature, as the wellbore pump changes between the wellbore operating temperature and the wellbore pump assembly temperature multiple times.

[0007] The impeller is a first impeller, the diffuser is a first diffuser, the ring- shaped memory material is a first ring-shaped memory material, the first impeller and the first diffuser form a first pump stage. The pump can also include a second pump stage connected in series with the first pump stage. The second pump stage includes a second rotating impeller the second impeller that rotates to provide kinetic energy to flow fluid through the wellbore pump, a second stationary diffuser positioned within the pump housing, the second diffuser positioned uphole of the second impeller, the second diffuser receiving the kinetic energy from the second impeller and responsively converting the kinetic energy to head to flow the fluid through the wellbore pump, and a second ring-shaped memory material positioned around the second diffuser. The memory material is able to reversibly expand from a temporary shape to a permanent shape in response to wellbore operating conditions of the wellbore pump to form an interference fit with the inner surface of the pump housing before pump operation downhole or during operation of the wellbore pump under the wellbore operating conditions. An axial height of the first ring-shaped memory material along a longitudinal axis of the pump housing is the same as or different from an axial height of the second ring-shaped memory material along the longitudinal axis of the pump housing. The memory material forms the interference fit with a strength sufficient to prevent rotation of the diffuser. A radial thickness of the diffuser at a location at which the ring-shaped memory material is positioned is greater than a radial thickness of the diffuser at other locations along a longitudinal axis of the pump housing. The ring- shaped memory material has an axial height along a longitudinal axis of the pump housing, wherein the axial height is based on a wall thickness of the diffuser.

[0008] Certain aspects of the subject matter described here can be implemented as a method. A wellbore pump stage of a wellbore pump is assembled. The wellbore pump stage includes a rotating impeller that rotates to provide kinetic energy to flow fluid through the wellbore pump, a stationary diffuser positioned within the pump housing, the diffuser positioned uphole of the impeller, the diffuser configured to receive the kinetic energy from the impeller and responsively convert the kinetic energy to head to flow the fluid through the wellbore pump. A pump head is attached to the uphole-facing end of the pump housing. A compression tube is attached between the pump head and the diffuser. The compression tube increases a contacting force between the diffusers. An inner surface of the pump housing and an outer surface of the diffuser are separated by a gap. A memory material is formed into a ring shape having an inner diameter that is equal to or greater than an outer diameter of the diffuser and having an outer diameter that is less than an inner diameter of the pump housing. The ring-shaped memory material is positioned around the outer diameter of the diffuser. Forming the memory material into the ring shape includes deforming the ring-shaped memory material from a permanent state in which the outer diameter of the memory material is greater than or equal to the inner diameter of the pump housing to a temporary state in which the outer diameter of the memory material is less than the inner diameter of the pump housing. The memory material is more rigid in the permanent state than the temporary state. The memory material is in the temporary shape during assembly before installation downhole, and the material is in the permanent state at a wellbore pump temperature at which the wellbore pump is positioned downhole in the wellbore and is not operating. The memory material is in the permanent state at a wellbore operating temperature at which the wellbore pump is operating when the wellbore pump is positioned downhole in the wellbore. Forming the memory material into the ring shape includes forming the memory material to reversibly transition between the temporary state and the permanent state multiple times without degradation as a temperature of the wellbore pump changes between the wellbore operating temperature and the wellbore pump assembly temperature multiple times. The ring-shaped memory material is positioned at a location. A radial thickness of the diffuser at the location at which the ring-shaped memory material is positioned is greater than a radial thickness of the diffuser at other locations along a longitudinal axis of the pump housing.

[0009] The wellbore pump stage is a first wellbore pump stage, the impeller is a first impeller, the diffuser is a first diffuser, the memory material is a first memory material. A second wellbore pump stage of the wellbore pump is assembled. The second wellbore pump stage includes a second rotating impeller that rotates to provide kinetic energy to flow fluid through the wellbore pump, a second stationary diffuser positioned within the pump housing positioned uphole of the second impeller. The second diffuser receives the kinetic energy from the second impeller and responsively converts the kinetic energy to head to flow the fluid through the wellbore pump. A second memory material is formed into a ring shape having an inner diameter that is equal to an outer diameter of the diffuser and having an outer diameter that is less than an inner diameter of the pump housing. The second ring-shaped memory material is positioned around the outer diameter of the second diffuser. The first wellbore pump stage is attached in series with the second wellbore pump stage.

[0010] Certain aspects of the subject matter described here can be implemented as a downhole pump. The downhole pump can include a pump housing, a rotating impeller that rotates to provide kinetic energy to flow fluid through the wellbore pump, a stationary diffuser positioned within the pump housing uphole of the impeller that receives the kinetic energy from the impeller and responsively converts the kinetic energy to head to flow the fluid through the wellbore pump, a pump head attached to the first end of the pump housing, a pump base attached to the second end of the pump housing, a compression tube attached between the pump head and the diffuser that increases a contacting force between the diffuser to prevent rotation of the diffuser with the impeller, a lower diffuser spacer attached between the pump base and the diffuser, and a ring-shaped memory material positioned around the diffuser. The memory material is able to reversibly expand from a temporary state to a permanent state in response to wellbore operating conditions of the wellbore pump. The memory material is less rigid in the temporary state than in the permanent state.

[0011] In the permanent state, the memory material forms an interference fit between the diffuser and the pump housing. The interference fit has a strength to prevent rotation of the diffuser. The memory material can expand from the temporary state to the permanent state in response to wellbore operating conditions at which the wellbore pump operates downhole in the wellbore. The memory material contracts from the permanent state to the temporary state in response to a change in the wellbore operating conditions. The wellbore operating conditions can include a wellbore operating temperature at which the wellbore pump operates downhole in the wellbore. The memory material remains in the temporary state when a wellbore pump temperature is below the wellbore operating temperature and expands to the original state when the wellbore pump temperature is at or greater than the wellbore operating temperature.

[0012] The details of one or more implementations of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

[0013] FIG 1A is a schematic diagram of a portion of an electric submersible pump installed in a wellbore with its anti-rotation rings in their temporary shape.

[0014] FIG IB is a schematic diagram of a portion of an electric submersible pump installed in a wellbore with its anti-rotation rings in their permanent shape.

[0015] FIG 1 C is a schematic diagram of a portion of an electric submersible pump with two stages installed in a wellbore. [0016] FIG. 2 is a schematic diagram of a shape-memory-polymer anti-rotation band.

[0017] FIG. 3 shows a flow-chart of an example method to utilize shape- memory-polymer bands on a downhole piece of equipment.

[0018] Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

[0019] An electric submersible pump (ESP) system consists of a centrifugal pump, a protector, a motor, and a monitoring sub. The pump is used to lift well-fluid to the surface. The motor provides energy to drive the pump. The protector absorbs the thrust load from the pump, transmits power from the motor to the pump, and prevents well-fluid from entering the motor. The monitoring sub provides information on the well fluid characteristics such as pump intake and discharge pressures, pump intake temperature, motor internal temperature, and vibration to mention a few. The pump consists of stages, each of which is made up of an impeller and a diffuser. The impeller, which is rotating, adds energy to the fluid to provide flow, whereas the diffuser, which is stationary, converts the kinetic energy of fluid from the impeller into head. The pump stages are typically stacked in series to form a multi-stage system. All the stages are contained within a pump housing and capped on either end with a pump head and base. The sum of head generated by each individual stage is cumulative; that is, the total head developed by the multi-stage system increases linearly from the first to the last stage. An ESP operates in a production wellbore.

[0020] One of the steps done during ESP pump assembly is diffuser compression. This step is performed to ensure that the stacked diffusers, or stages, stay in contact with one another and to prevent rotation during operation. In this process, a compression tube is first cut to size based on the total diffuser compression required and is sandwiched between the pump head and the topmost final diffuser to provide the desired compression force. During pump operation, the impeller transmits torque to the fluid which is transmitted to the walls of the diffuser. Sometimes, however, either due to improper compression during assembly or higher than expected head generation at the specified flow conditions, the diffuser compressive force is overcome by the pressure based force from the diffusers. When such total loss in compression occurs, the diffuser rotates in the same direction as the impeller resulting in a phenomenon known as a spinning diffuser. The consequence is production fluid escaping into the annulus space between the housing inner diameter and diffusers' outer diameter, putting unnecessary stress on the diffuser walls from the escaped high pressure fluid, which can lead to diffuser wall collapse leading to pump failure. In addition, insufficient head is developed by the diffusers since they are spinning. The diffusers can rub against any contact surfaces with other diffusers, or the diffusers' outside diameter can also rub on the internal walls of the housing, resulting in material loss both for the diffuser and housing, which creates excessive heat generation due to friction and consequently leads to premature pump failure.

[0021] To prevent diffuser spinning, conventional pump assembly relies on high compression force to ensure enough frictional contact force between the diffusers. However, pump conditions can vary quite considerably during operation to favor the spinning diffuser effect. As such, supplemental diffuser anti-rotation techniques have been implemented, namely, a secondary compression device, which could be a spring member, is attached in conjunction with the primary compression device. The combination is such that, should the primary compression device lose its compressive capability, the spring member becomes the primary compression device to ensure the diffusers remain in contact with one another. A potential shortcoming of such an arrangement can arise from spring relaxation after many cycles of operation. When this occurs, the spring member's function is lost, leading to the spinning diffuser effect.

[0022] Other anti-rotation techniques have lugs extending axially from each diffuser that nest with corresponding axially positioned recesses formed along the circumference of the diffuser above it to prevent relative motion between the diffusers. In addition, within each lug-recess mating faces, O-rings are installed on the exterior of each diffuser to form a seal. At the uppermost end of the stack, a retaining ring is mounted within a recess in the housing to lock the diffusers mechanically to the housing and prevent rotation. One shortcoming of this technique is that there is added machining operation to create the lugs and recesses in the diffusers, resulting in increased manufacturing time and higher unit product or equipment cost.

[0023] Another anti-rotation technique involves a variable compression device or ring, which could be plastic or hard rubber that is placed between the compression tube and the uppermost diffuser. If the compression tube is cut too short, the variable compression ring expands to maintain the required compression load on the diffusers to prevent diffuser spinning during pump operation. Conversely, if the compression tube is cut too long, the variable compression device contracts to maintain the desired compression load on the diffuser to prevent diffuser spinning. One of the potential shortcomings of this method is the ability for the hard rubber or plastic to undergo compression set after many cycles of expansion and compression, thereby losing its effectiveness, which makes the material susceptible to the diffuser spinning effect similar to conventional assembly methods.

[0024] This disclosure describes an anti-rotation apparatus for use with ESPs, also known as wellbore pumps, that are made of a shape memory polymer (SMP) or other similar shape-memory material. The SMP is shaped into a ring that fits snuggly around the ESP diffuser. The SMP is configured to expand at the wellbore operating temperature and create an interference fit between the ESP diffuser and ESP housing. The SMP is configured to expand at wellbore operating temperature rather than the pump operating temperature so that the SMP material is expanded to create the interference fit prior to pump start-up. The interference fit provides an anti-rotation force via a high frictional resistance. The SMP is utilized either alone or in conjunction with compression tubes or other structural devices that can be used to prevent anti- rotation.

[0025] FIG. 1A shows a portion of an assembled ESP 100 with anti-rotation bands 108 in a temporary shape. The ESP 100 can include multiple pump stages (a first pump stage 126 is shown as an example; other similar pump stages are also possible), each of which includes an impeller (for example, a first impeller 118) and a diffuser (for example, a diffuser 112a). The multiple stages can collectively be referred to as a bundle 116. The bundle 116 is encased within a housing 114. The housing 114 has two ends: an uphole end 128 and a downhole end 130. A pump head 102 is attached to the uphole end 128 of the housing 114. A compression tube 104 is placed in between the pump head 102 and a diffuser 112b of the pump stage nearest to the uphole end 128. The compression tube 104 provides a compressive force to prevent the diffuser 112b of the pump stage nearest the uphole end 128 from spinning. The bundle 116 has two ends: a suction-end 122 and a discharge-end 106. The diffuser 112a of the pump stage nearest the suction end 106 is supported by a pump base 134. [0026] The ESP 100 takes in production fluids from the wellbore at the suction-end 122 which is the located downhole of the discharge-end 106. The discharge-end 106 sends the production fluids into the production tubing (not shown) and in the uphole direction toward a topside facility. In the implementation shown in FIGS. 1A-1B, the diffuser 112b nearest the uphole end 128 is immediately uphole (that is, downstream) of the impeller 118. The head added by each stage is summative as production fluid moves through the ESP 100.

[0027] The multiple stages 116 are placed into a housing 114 during assembly. On the uphole end 128 of the housing 114, the ESP 100 is held within the housing 114 via a pump head 102. On the downhole end 130 of the housing 114, the multiple stages 116 are in contact with a lower diffuser spacer 132. The lower diffuser spacer is rigidly secured by the pump base 134 which is threaded into the downhole end 130 of the housing 114 to keep the bundle 116 in compression. The unexpanded SMP anti- rotation bands 108, which are in their temporary shape, are located around each diffuser of each pump stage.

[0028] SMPs are polymers that can change from a temporary shape to their permanent shape in the presence of external stimuli, such as temperature or other stimuli. Another property of shape memory materials is the two-way shape memory effect. This is the ability for the material to remember its shape when heated to a high temperature and also remember its shape when cooled to a low temperature. SMPs are characterized by a glass transition temperature, T , below which they are stiff. Below T , the SMP is in a temporary shape. When the material is heated above T , it returns to a permanent shape. This process is reversible and can be repeated many times without the polymer degrading. In addition, the polymer can be engineered to have a specified glass transition temperature, for example between -22°F to 500°F. The SMP is first engineered and fabricated to its desired permanent shape using conventional manufacturing methods, which include molding and curing, before being processed to the desired temporary shape. This is achieved by heating the manufactured permanent shape above the glass transition temperature of the SMP (T ). Subsequently, a load is applied to the SMP to deform it to the target temporary shape. With the SMP still loaded/constrained in its temporary shape, it is cooled below its glass transition temperature (T ), typically to near room temperature. After reaching room temperature, the load/constraint is removed and the SMP retains this temporary shape. It is this temporary shape that the unexpanded anti-rotation band 108 has during the assembly process. For SMPs engineered and manufactured with a one-way shape memory effect, when the temporary shape is heated to a temperature above the SMP's glass transition temperature, the SMP is transformed to its permanent shape. For SMPs engineered and manufactured with a two-way shape memory effect, when the temporary shape is heated to a temperature above the SMP's glass transition temperature, the SMP is transformed to its permanent shape. However, cooling the SMP below its glass transition temperature causes the SMP to revert back to its temporary shape.

[0029] FIG. IB shows the same portion of the installed ESP 100 shown in FIG 1A, but with expanded SMP anti-rotation bands 110 now in their permanent shape. Unexpanded SMP anti-rotation bands 108 in their temporary shape fit securely around the pump diffuser 112a and the diffuser 112b. The outer surface of the unexpanded anti-rotation band 108 after installation around the diffuser 112a and the diffuser 120b leaves adequate clearance with the inner wall of the housing 114 for ease of installation. Anti-rotation band 108 is an SMP manufactured with a two-way shape memory effect. In its temporary unexpanded shape, the anti -rotation band 108 is a ring with an inner diameter that is equal to an outer diameter of the bundle 116 (within typical press-fit machining tolerances) and a radial thickness that is less than a clearance between the outer surface of the bundle 116 and the inner surface of the housing 114. The glass transition temperature of the SMP (T ) has been set prior to installation to be above temperatures experienced during assembly and installation, but below that of the operating temperature of the wellbore. The permanent shape of the expanded SMP anti-rotation band 110 is configured to provide an interference fit between the outer diameter of expanded SMP anti -rotation band 110 and the internal diameter of the housing 114. That is, in the permanent expanded shape, the inner diameter of the ring is equal to the outer diameter of the bundle (within standard machining tolerances for press-fit parts) and the radial thickness is at least equal to the clearance between the outer surface of the diffuser 112a and the diffuser 112b and the inner surface of the housing 114. The interference fit, working in conjunction with the compression tube 104, adds a frictional force to resist any rotation of the pump diffusers. The SMP bands will return to their temporary state after the pump has been removed from the wellbore and the SMP temperature has fallen below the glass transition temperature (T ). [0030] In some implementations, multiple stages can be used within the bundle 116. In such an implementation, which is shown in FIG 1C, an ESP can include, for example, a first stage 126a and a second stage 126b. Each pump stage 126 can include the anti -rotation bands 108 in the temporary shape that is installed during pump assembly. As in the previously discussed implementations, the anti -rotation bands 108 in the temporary shape expand to become the expanded SMP anti-rotation bands 110 in their permanent shape once the ESP 100 is positioned within the wellbore and experiences temperatures above glass transition temperature (Tg).

[0031] FIG. 2 shows a top view of a generic SMP anti-rotation band 200. The SMP anti-rotation band 200 is ring-shaped in its temporary shape for ease of installation. As described earlier, the temporary shape of SMP anti-rotation band 200 is pre-manufactured such that its inner surface conforms to the outer surface of the bundle 116, but the outer diameter of band 200 is less than the diameter of the inner surface of the pump housing 114. In general, the permanent shape of the outer and inner surfaces of the anti-rotation band 200 can be formed to conform to the inner surface of the pump housing 114 and the outer surface of the bundle 116, respectively. The glass transition temperature (T ) of the rotation band 200 is pre-engineered set to be below the operating temperature of the wellbore pump 100 in the wellbore and above that of the wellbore pump 100 during assembly. The wellbore temperature is warmer than the temperatures experienced during assembly.

[0032] The axial placement of the unexpanded SMP anti-rotation bands 108 in their temporary shape is ideally around the diffuser 112a and the diffuser 112b of the pump bundle 116 where the diffusers' radial thickness is greatest. An expanded SMP anti-rotation band 110 located around a thin- walled section of the bundle 116 could potentially collapse the diffuser 112a or the diffuser 112b. The specific temporary (unexpanded) and permanent (expanded) shapes of the anti-rotation bands 200 are manufactured in different sizes for each ESP 100 model due to dimensional differences. SMP anti-rotation bands 200 can be placed on one or multiple diffusers at various longitudinal heights.

[0033] The subject matter can be implemented with an example method 300 shown in FIG 3. The steps of method 300 can be performed in parallel, in series, or in a different order than that shown in FIG. 3. First, a pump base is picked up from a stock of pump bases. At 302, a lower diffuser spacer 132 is attached to a pump base 134. The pump base 134 can then be attached to the housing 114, or the pump base can be set aside until a pump stage 126 is completed. At that point, a pump stage can be connected to the lower diffuser spacer 132. Before that can occur, at 304, a wellbore pump stage 126 of a wellbore pump 100 is assembled. Assembling a pump stage can include placing an impeller 118 into a first diffuser 120. At 306, a memory material is formed into a ring shape having an inner diameter that is equal to the outer diameter of the diffuser 120 of the previously assembled pump stage 126 and having an outer diameter that is less than an inner diameter of a pump housing 114. At 308, The ring- shaped memory material is positioned around the outer diameter of the diffuser 120. The memory material is placed around the diffuser 120 in its unexpanded or temporary shape. At 310, a second wellbore pump stage of the wellbore pump is assembled. At 312, a second memory material is formed into a ring shape having an inner diameter that is equal to the outer diameter of the diffuser of the assembled pump stage assembled at 310 and having an outer diameter that is less than an inner diameter of a pump housing 114. At 314, the second ring-shaped memory material is positioned around the outer diameter of the diffuser of the second pump stage. The memory material is placed around the second diffuser in its unexpanded or temporary shape. At 316, the first wellbore pump stage 126a is attached in series with the second pump stage 126b to form a bundle 116. At 318, the bundle 116 is inserted into a pump housing 114. At 320, a compression tube 104 is attached between the pump bundle 116 and a pump head 102. At 322, the pump head 102 is attached to the uphole-facing end 128 of the pump housing 114. The pump head 102 and pump base 134 can be attached to the pump housing with a threaded connection.

[0034] A number of implementations of the subject matter have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the subject matter. For example, shape-memory alloys could be used instead of an SMP. Accordingly, other implementations are within the scope of the following claims.