ELECTRIC SUBMERSIBLE PUMP

FIELD

The present disclosure relates generally to electric submersible pumps. In particular, the present disclosure relates to electric submersible pumps for use in wellbores related to oil and gas production.

BACKGROUND

During various phases of oil and gas operations it can become necessary to increase pressure and/or withdraw fluid from within a wellbore. This can often be referred to as artificial “lift” or “pressure.” For example, after drilling a wellbore and during the withdrawal of hydrocarbons, it can be necessary to use a pump to increase the pressure within a wellbore when natural pressure is insufficient to withdraw the desired amount of hydrocarbons. An electric submersible pump (ESP) can be used to provide artificial lift for withdrawing hydrocarbons.

In order to increase pressure in a wellbore, the ESP is often provided downhole along a portion of a tubing string. The pump can have multiple stages provided within a housing, one stage stacked upon another stage. In order to prevent recirculation within the pump housing, an O-ring can be employed. If such O-rings are unsuccessful or fail, the pump must be brought to the surface. Such difficulties can lead to increased service intervals and increased costs.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations of the present technology will now be described, by way of example only, with reference to the attached figures, wherein:

FIG. 1 is a diagram illustrating an exemplary environment for an electric submersible pump (ESP) within a electric submersible pump string;

FIG. 2 is a diagrammatic cross section view illustrating an exemplary ESP within a housing;

FIG. 3 is a diagram illustrating an exemplary two stage diffuser stack of an ESP;

FIG. 4 is a diagram illustrating an exemplary ESP diffuser;

FIG. 5 is a diagram illustrating the exemplary diffuser of the ESP of FIG. 4 from a different aspect;

FIG. 6 is a diagram illustrating an exemplary impeller of an ESP;

FIG. 7 is a diagram illustrating an exemplary two stage diffuser stack of an ESP;

FIG. 8 is a diagram illustrating an exemplary ESP within a housing;

FIG. 9 is a diagram illustrating a second exemplary diffuser of an ESP having a strengthening insert; and

FIG. 10 is a diagram illustrating the strengthening insert of FIG. 9.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures and components have not been described in detail so as not to obscure the related relevant feature being described. Also, the description is not to be considered as limiting the scope of the embodiments described herein. The drawings are not necessarily to scale and the proportions of certain parts have been exaggerated to better illustrate details and features of the present disclosure.

In the following description, terms such as “upper,” “upward,” “lower,” “downward,” “above,” “below,” “downhole,” “uphole,” “longitudinal,” “lateral,” and the like, as used herein, shall mean in relation to the bottom or furthest extent of, the surrounding wellbore even though the wellbore or portions of it may be deviated or horizontal. Correspondingly, the transverse, axial, lateral, longitudinal, radial, etc., orientations shall mean orientations relative to the orientation of the wellbore or tool. Additionally, the illustrated embodiments are illustrated such that the orientation is such that the top of the page is toward the surface, and the lower side of the page is downhole. A “pump” as used herein can include Electric Submersible Pump (ESP). The term pump and ESP are used interchangeably within this disclosure.

Several definitions that apply throughout this disclosure will now be presented. The term “coupled” is defined as connected, whether directly or indirectly through intervening components, and is not necessarily limited to physical connections. The term “outside” refers to a region that is beyond the outermost confines of a physical object. The term “inside” indicate that at least a portion of a region is partially contained within a boundary formed by the object. The terms “comprising,” “including” and “having” are used interchangeably in this disclosure. The terms “comprising,” “including” and “having” mean to include, but not necessarily be limited to the things so described.

Disclosed herein is an electric submersible pump (ESP) which can reduce or assist in preventing recirculation within a pump housing. The ESP can be attached to a downhole tubing string and used for creating artificial pressure or lift in a wellbore. The pump can have a housing containing one or more stages. The housing has a head plate and a base portion at opposing ends, the head plate being at the end nearest the wellhead and the base portion at the end furthest from the wellhead. Each stage has a diffuser and/or an impeller to move or displace fluid or gas, thus generating lift pressure. The one or more stages can stack one upon the other, such that one diffuser sits substantially on top of another. The stack can be referred to as a diffuser stack. The impeller can be substantially received within the diffuser. The impeller can rotate around a longitudinal axis within the diffuser. During operation, the diffuser remains stationary relative to the housing.

The one or more stages and/or the diffuser stack can be under compression within the housing to assist in preventing recirculation of fluid and assist in preventing rotation of the diffuser(s). The housing can also have a filler provided between the inner surface of the housing and the exterior surface of the diffuser(s) to prevent recirculation and/or rotation of the diffuser within the housing. The gap between the inner surface of the housing and the outer surface of the diffuser wall can be referred to as an annular gap.

The filler can be a curable sealant injected into the annular gap, a sleeve disposed within the annular gap, or other sealing mechanism, or a combination thereof. For example, a curable sealant or expandable sleeve can be provided in the annular gap and cured or configured to expand at operating temperatures. The filler as disclosed herein can be provided in addition to an O-ring arranged in a groove in the side wall of the diffuser. Alternatively, the O-ring and the groove for receiving the O-ring can be omitted entirely, with the filler provided within the annular gap. By providing a diffuser without a groove in the side wall, the diffuser side wall will as a result have increased strength. Further, the filler aids in preventing recirculation and/or rotation of the diffuser. Therefore, by use of the filler as disclosed herein, the weakness in the diffuser wall associated with the O-ring groove can be avoided, while also preventing recirculation and/or rotation of diffusers.

Also disclosed herein is a reinforcement for the groove in the diffuser wall which receives the conventional O-ring. For example, a steel ring can be provided within the groove to provide support in view of the compression which is typically imposed on the diffuser stacks.

Therefore, the diffuser(s) in an ESP can be strengthened by providing a filler and omitting the groove in the diffuser side wall, or providing a reinforcement in the groove as disclosed herein.

The ESP 114 can be employed in an exemplary wellbore pumping system 1 shown for example in FIG. 1. The system 1 includes a wellbore 100 having a wellhead 102 at the surface 104. The wellbore 100 extends and penetrates various earth strata including hydrocarbon containing formations. A casing 115 can be cemented along a length of the wellbore 100. A power source 106 can have an electrical cable 108, or multiple electrical cables, extending into the wellbore 100 and coupled with a motor 112. It should be noted that while FIG. 1 generally depicts a land-based operation, those skilled in the art will readily recognize that the principles described herein are equally applicable to subsea operations that employ floating or sea-based platforms and rigs, without departing from the scope of the disclosure.

Disposed within the wellbore 100 can be a tubing string 110 having an ESP 114 forming an electric submersible pump string. The ESP 114 may be driven by a motor 112. The tubing string 110 can also include a pump intake 119 for withdrawing fluid from the wellbore 100. The pump intake 119, or pump admission, can separate the fluid and gas from the withdrawn hydrocarbons and direct the fluid into the ESP 114. A protector 117 can be provided between the motor 112 and the pump intake 119 to prevent entrance of fluids into the motor 112 from the wellbore. The tubing string 110 can be a series of tubing sections, coiled tubing, or other conveyance for providing a passageway for fluids. The motor 112 can be electrically coupled with the power source 106 by the electrical cable 108. The motor 112 can be disposed below the ESP 114 within the wellbore 100. The ESP 114 can provide artificial pressure, or lift, within the wellbore 100 to increase the withdrawal of hydrocarbons, and/or other wellbore fluids. The ESP 114 can provide energy to the fluid flow from the well thereby increasing the flow rate within the wellbore 100 toward the wellhead 102

Illustrated in FIG. 2 is one example of an ESP 114. The ESP 114 can have a housing 116 having a head plate 118 and a base portion 120. The head plate 118 can be disposed at the upper portion of the housing 116 and the base portion 120 can be disposed at the lower portion of the housing 116. The housing 116 can further include at least one inlet 160 and at least one outlet 162. Each inlet 160 has an opening to allow fluids, such as hydrocarbons, to enter the ESP 114 and each outlet 162 also has an opening to allow fluids to exit after passing through the ESP 114. The housing 116 can receive a diffuser stack 122. Multiple diffuser stacks 122 can be provided in the housing 116. The diffuser stack 122 includes one or more stages 124. The inner surface of the housing 116 side wall and the outer surface of the diffuser stack 122 can form an annular gap 158. The annular gap 158 can provide spacing to facilitate the insertion and removal of the diffuser stack 122 from the housing 116.

Multiple stages 124 can be stacked one upon the other to increase the energy added to the flow within the wellbore 100. Any number of stages can be employed, depending on the requirements of the system 1. Longer wellbore holes may require a larger number of stages 124, and therefore longer diffuser stacks, due to the increased lift requirements as a result of the increased volume of the wellbore. For example, a 5,000 foot long hole may require as many as 50 stages 124 to provide sufficient lift. Longer diffuser stacks or ESP's can be provided, for example, a 10,000 foot long wellbore hole may require as many as 75 stages 124. Any number of stages can be employed, however, typically there can be anywhere from 10 to 100 stages, alternatively 25 to 75 stages.

Each stage 124 of the diffuser stack 122 can be made up of an individual diffuser 126 and an individual impeller 128 received within the diffuser 126. Each stage 124 in the diffuser stack 122 can be substantially identical, having substantially identical diffusers 126 and impellers 128 at each stage. The diffuser stack 122 having the one or more stages 124 can be configured to handle various fluids. For example, different types of impellers 128 and diffusers 126 can be employed depending on the fluids to be pumped, desired pressure or other requirements in the system. For example, the fluids to be pumped can be clear liquids, brine, saltwater, hydrocarbons, mud, abrasives or gas, or other wellbore fluids. Accordingly, the impellers and diffusers can be configured to accommodate the particular fluids and conditions of the wellbore. The arrangement of the diffuser stack 122 can depend on the wellbore 100 and the hydrocarbon mixture being withdrawn therefrom.

As illustrated in FIG. 2, the impeller 128 is provided to rotate within the diffuser 126 about an impeller shaft 130. The impeller shaft 130 can extend at least partially above the main body of the impeller 128 to be received by an adjacent impeller 129 stacked in the next stage above. The diffuser 126 can also have an aperture 146 (shown in FIG. 5) through which the impeller shaft 130 extends. The impeller shaft 130 can extend partially above and/or partially below the main body of the impeller 128 and couple with impeller shafts 130 above and/or below in a stacking fashion. For example, the portion of the impeller shaft 130 extending partially above the impeller 128 couples with the impeller shaft 130 of the stage 124 stacked directly above, whereas the portion of the impeller shaft 130 extending partially below the impeller 128 couples with the impeller shaft 130 of the stage 124 stacked directly below. The impeller shaft 130 of the stage 124 at the top of the diffuser stack 122 can be received by the head plate 118. The impeller shaft 130 of the stage 124 at the bottom of the diffuser stack 122 can be received at the base portion 120 and coupled with the motor 112 (shown in FIG. 1). Accordingly, the impeller shafts 130 together can form a shaft extending throughout the diffuser stack 122.

The diffuser stack 122 can be compressed within the housing 116 to prevent recirculation of fluid between the one or more stages 124. The diffuser stack 122 can be compressed between the head plate 118 and the base portion 120. A compression bearing 132 can be disposed above the head plate 118 and can apply mechanical compression force on the diffuser stack 122. The base portion 120 can have substantial strength to resist the compressive force therefore causing the diffuser stack 122 to compress. For example, the compression bearing 132 can be a spider wheel bearing configured to engage threads on the upper portion of the impeller shaft 130 and compress the head plate 118 into the diffuser 126 of the uppermost stage 124 in the diffuser stack 122. The compression bearing 132 can compress the diffuser stack 122 a predetermined distance, such as from 1/2,500^thof an inch to 1/500^thof an inch, or alternatively from 1/2000^thof an inch to 1/1,000^thof an inch.

Illustrated in FIG. 3 is an example of a two stage 124 diffuser stack 122. One diffuser 126 of one stage 124 can be stacked on top of another diffuser 126 of the adjacent stage 124. The diffuser 126 can have a side wall 134 forming a contained receiving space 136. The impeller 128 can be substantially received within the diffuser 126 receiving space 136. The upper portion of the impeller shaft 130 can extend beyond the upper surface of side wall 134 of the diffuser 126. The upper portion of impeller shaft 130 can have at least one groove 139 formed on the inner surface. The at least one groove 139 can couple with the impeller shaft 130 with the stage 124 directly above in the diffuser stack 122. As can be appreciated in FIG. 3, the diffusers 126 can be stacked and the side wall 134 of each diffuser 126 can form a substantially flush coupling with the adjacent stage 124.

Illustrated in FIG. 4 is an example of a diffuser 126. The diffuser side wall 134 can have a substantially smooth inner surface 138. The upper portion of the inner surface 138 can have a seat 140 formed therein and receive the adjacent diffuser 126. The lower portion of the outer surface of diffuser 126 side wall 134 can have a taper 142 to engage the seat 140 of an adjacent diffuser 126. The diffuser side wall 134 may be substantially cylindrical and the seat 140 may have a ridge formed on the inner portion of the side wall 134. The ridge can receive the tapered 142 lower portion of the adjacent diffuser 126, thereby forming the diffuser stack 122. The lower portion of the diffuser 126 can have a plurality of inlets 144 to allow fluids to enter the diffuser 126 from an adjacent stage 124. The inlets 144 can be angled to assist in directing fluid flow toward the impeller 128 (shown in FIG. 6). The diffuser 126 can be made from various materials, such as metals or alloys, for example Ni-resist alloys, including Ni-resist type −1.

Illustrated in FIG. 5 is an example diffuser 126 of FIG. 4 shown from a different angle. The tapered 142 lower portion and plurality of inlets 144 can allow the diffuser 126 to be stacked sequentially upon additional diffusers 126 within an ESP 114. The plurality of inlets 144 can allow fluid flow to move into diffuser 126. The diffuser 126 can have an aperture 146 formed in the bottom surface to receive the impeller shaft 130.

Illustrated in FIG. 6 is an example embodiment of an impeller 128. The impeller 128 can be received in the diffuser receiving space 136 (shown in FIG. 4). During operation, the impeller 128 can float within the diffuser such that the impeller 128 does not contact the diffuser side wall 134 (shown in FIG. 4). The impeller 128 can have a plurality of veins 148 to impart energy in the fluid as the impeller 128 rotates within the diffuser 126. The plurality of veins 148 can be angled to impart energy in a direction corresponding to the plurality of inlets 144 of the diffuser 126 (shown in FIG. 5). In the illustrated embodiment, the impeller shaft 130 extends beyond the upper surface of the impeller 128. The impeller shaft 130 can extend to various lengths, for example, beyond the lower surface of the impeller 128. The impeller shaft 130 can be made to extend a larger amount above or below, or an equal amount above and below the main body of the impeller 128. The impeller shaft 130 at each impeller can matingly engage with impeller shafts of adjacent impellers to form a shaft within the ESP.

FIG. 7 is a diagrammatic illustration of two stages 124 of an ESP 114. The stages 124 can impart energy into fluid flowing through the ESP 114. The impeller 128 can induce a pressure differential within the diffuser 126 causing fluid to move from the bottom of the diffuser 126 to the receiving space and then into the stage 124 above. As can be appreciated in FIG. 7, as the impeller 128 rotates within the diffuser 126 fluid (or hydrocarbons) moves from one stage 124 to the stage above adding energy to the fluid flow. While the illustrated embodiment has two stages, any number of stages 124 depending on the environment and desired flow can be employed.

Illustrated in FIG. 8 is a cross-section view of an ESP 114 having four diffusers 126 and three impellers 128. The annular gap 158 can be formed between the inner wall of the housing 116 and the outer wall of diffusers 126. The annular gap 158 can allow the diffuser stack 122 to be inserted into the housing 116 during assembly. Conventionally, an O-ring can be provided on the outer wall of each diffuser 126 at each stage. However, as disclosed herein, the annular gap 158 can be provided with a filler 150 to prevent unwanted flow of fluids between stages and which can also serve to assist in preventing rotation of the diffusers 126 relative to the housing 116. While the impeller 128 is intended to rotate within the diffuser 126, the diffuser 126 and housing 116 remain stationary. Rotation of the diffuser 126 within housing 116 can cause recirculation and pump failure. The filler 150 can be provided at individual stages or fill along substantially the entire longitudinal length of the diffuser stack. Moreover, the filler removes the need for O-rings, and thus diffusers 126 without O-rings or grooves can be employed to make up the diffuser stack 122. Diffusers 126 without O-rings can allow easier insertion and removal of the diffuser stack 122 from the housing 116 of the ESP 114 as O-rings can increase friction during assembly. Further, the thinner walls associated with the groove can be avoided, and instead the side walls can have approximately the same thickness throughout the length of the diffuser. As a result, the diffuser 126 has increased strength and can withstand higher compressions and/or have longer life. However, the filler 150 can be beneficially employed in the annular gap 158 along with the use of O-rings and/or associated grooves.

The filler 150 can be a sleeve, sealant, curable material, or other sealing mechanism provided to fill the annular gap 158 and prevent recirculation and/or rotation. During assembly, the diffuser stack 122 can be placed within the housing 116 and the filler 150 disposed within the annular gap 158 before or after the diffuser stack 122 is compressed. The filler 150 can be a curable silicone, epoxy, rubber or elastomer, polyurethane, acrylics, phenolic compounds, or any other suitable filler. The filler 150 can have a viscosity sufficiently high so as to distribute throughout the annular gap 158 without entering the diffuser 126. The filler 150 can be configured to fill the full radial width of the annular gap 158. Additionally, the filler 150 can be configured to fill the annular gap 158 substantially along the full length of the side wall 134 of diffuser stack 122.

The filler 150 can be curable and can made up of material which cures by the simple passage of time, or in the presence of increased heat or the addition of chemical agents. Curable materials can be cross-linkable materials or have increased cohesion. Prior to curing, the curable filler can flow easily, and then solidify upon curing to maintain itself within the annular gap. For example, the curable filler 150 can be flowingly provided in the annular gap 158 and then cured at operating temperatures, or subject to heat prior to insertion in the wellbore, to form a solid within the annular gap 158. During maintenance, the filler can be broken down to remove the diffuser stack 122 from the housing 116. In such cases, the ability of the filler 150 to flow prior to cure permits the filler 150 to be added easily within the annular gap 158, and then cured to provide a sealing function.

In other examples, the filler 150 can be a thermally expanding sleeve which expands to fill the annular gap at operating temperatures. Operating temperatures (e.g., 50° C. or more) are generally above atmospheric temperatures (typically from −10° C. to less than 50° C. depending on the climate where the wellbore is located) and usually high enough to expand the particular filler. Suitable thermally expandable materials can be employed as the thermally expandable sleeve, including silicone based material, for example. The thermally expanding sleeve can facilitate easy assembly of the diffuser stack 122 within the housing 116. For example, the thermally expanding sleeve can be thinner than the radial thickness of the annular gap 158 at atmospheric temperature. Therefore, at assembly, typically conducted at normal atmospheric temperatures, the sleeve can be more easily inserted into the annular gap 158. However, after insertion, the thermally expanding sleeve can be heated either by an operator or via normal operating conditions to expand to partially or completely fill the annular gap 158. The thermally expanding sleeve can be substantially rigid or alternatively can be elastomeric.

FIG. 9 illustrates a second example embodiment of a diffuser 126. Conventionally, with the employment of an O-ring, a groove is provided in the side wall of a diffuser to receive the O-ring. The groove is a circumferential channel formed in the outer surface of side wall 134. Due to the compression of the diffuser stacks excessive pressure can be imposed on the O-rings within such grooves, therefore leading to weakness or failure in the O-rings or diffuser stacks. As shown in FIG. 9, the diffuser 126 can have a groove 152 formed in the outer portion of the side wall 134. The groove 152 can be formed by removing a portion of the side wall 134 below the seat 140 and above the taper portion 142. The groove 152 can be configured to receive a high strength insert 154 having a groove 156 formed in its outer wall. The groove 156 can receive an O-ring and/or filler 150. The high strength insert 154 can allow an O-ring and/or filler 150 to be employed in the side wall 134 without decreasing the strength of the side wall 134.

In the particular example shown, the groove 156 of the high strength insert 154 can be configured to receive an O-ring 159. The O-ring 159 can be provided in the groove 152 and extend outward through the annular gap 158 between the diffuser side wall 134 and the housing 116. The O-ring 159 can be made from various suitable materials, for example nitrile rubbers including Buna-N. The O-ring 159 can be selected and sized according to the specific application of the ESP 114 and the conditions of the wellbore 100.

The high strength insert 154 can be made of iron, hardened steel (e.g. 174-H1025) or any material having a minimum yield strength of, for example, at least 150,000 pounds per square inch (PSI). The high strength insert 154 can further allow a diffuser having an O-ring 159 to withstand sufficient compression to be used as a sealing mechanism 150 in a diffuser stack including smooth outer surface diffusers 126 (shown in FIGS. 1-8). The high strength insert 154 can increase the strength of the diffuser 126 allowing a higher compressive force to be placed on the diffuser stack within the ESP. Accordingly, the reduced pressure on the O-ring can provide longer life, and/or reduce the degradation and/or failure of the O-ring.

FIG. 10 illustrates an example high strength insert 154 of a second example embodiment of a diffuser 126. The high strength insert 154 can be formed in more than one piece and configured to be inserted into the diffuser. In some examples, the high strength insert 154 can be formed in two pieces as a split ring. Each piece of the high strength insert 154 can be approximately half the radial circumference of the groove formed side wall of the diffuser. The high strength insert 154 can be made of more than two pieces, for example 2-5 pieces, or any number to assist assembly. The two or more pieces can be interchangeable, reducing part numbers and manufacturing costs. An end of each piece of the split high strength insert 154 can abut against an end of an adjacent piece of the high strength insert 154. The end of each piece can be angled and each end of the high strength insert 154 can be shaped to mate with an angled end of an adjacent piece of the high strength insert 154. A split high strength insert 154 can have two pieces, each have end pieces angled at approximately 45 degrees, each end piece shaped to mate with the adjacent end piece.

The diffuser shown in FIG. 9 can be implemented in a diffuser stack with diffusers shown in FIGS. 3-5, reducing the total number of O-rings and allowing increased compression, thereby reducing recirculation. Reducing the total number of O-rings in a diffuser stack can reduce assembly time without impeding performance of the pump.

STATEMENTS OF THE DISCLOSURE INCLUDE

Statement 1: An electric submersible pump comprising a housing having housing side walls, at least one stackable diffuser residing in the housing, each stackable diffuser having a diffuser side wall, and a filler substantially residing in an annular gap between an interior of the housing side walls and an exterior of the diffuser side wall of the at least one stackable diffuser, wherein the filler comprises at least one of a curable filler or a temperature expandable sleeve.

Statement 2: The electric submersible pump according to Statement 1, wherein the filler comprises the curable filler and the curable filler comprises at least one of silicon or epoxy.

Statement 3: The electric submersible pump according to Statement 1 or 2, wherein the filler expands or cures to fill the full radial width of the annular gap.

Statement 4: The electric submersible pump according to any one of the preceding Statements 1-3, wherein the filler expands or cures to fill the annular gap along the full longitudinal length of the stackable diffuser side wall.

Statement 5: The electric submersible pump according to any one of the preceding Statements 1-4, wherein the stackable diffuser does not have an external O-ring groove in the diffuser side wall.

Statement 6: The electric submersible pump according to any one of the preceding Statements 1-5, wherein the exterior wall of at least one stackable diffuser wall is substantially flat.

Statement 7: The electric submersible pump according to any one of the preceding Statements 1-6, wherein the side wall comprises an O-ring, and wherein the O-ring and filler are of different materials.

Statement 8: The electric submersible pump according to any one of the preceding Statements 1-7, comprising a plurality of stackable diffusers which are compressed from 1/2500th of an inch to 1/500th of an inch.

Statement 9: A electric submersible pump string comprising a tubing string, and an electric submersible pump (ESP) coupled with the tubing string, wherein the ESP comprises a housing having housing side walls, at least one stackable diffuser residing in the housing, each stackable diffuser having a diffuser side wall and, and a filler substantially residing in an annular gap between an interior of the housing side walls and an exterior of the diffuser side wall of at least one stackable diffuser, wherein the filler is at least one of a cured filler or a temperature expandable sleeve.

Statement 10: The electric submersible pump string according Statement 9, wherein the filler comprises the curable filler and wherein the curable filler comprises at least one of silicon or epoxy.

Statement 11: The electric submersible pump string according to Statement 9 or 10, wherein the filler expands or cures to fill the full radial width of the annular gap.

Statement 12: The electric submersible pump string according to any one of the preceding Statements 9-11, wherein the stackable diffuser does not have an external O-ring groove in the diffuser side wall.

Statement 13: The electric submersible pump string according to any one of the preceding Statements 9-12, wherein the side wall comprises an O-ring, and wherein the O-ring and filler are of different materials.

Statement 14: The electric submersible pump string according to any one of the preceding Statements 9-13, comprising a plurality of stackable diffusers which are compressed from 1/2500th of an inch to 1/500th of an inch.

Statement 15: An electric submersible pump comprising a housing having housing side walls, and at least one stackable diffuser residing in the housing, each stackable diffuser having a diffuser side wall, wherein the diffuser side wall has a circumferential channel comprising a material of greater strength than the remainder of the diffuser side wall.

Statement 16: The electric submersible pump according to Statement 15, wherein the circumferential channel comprises a hardened steel ring having a minimum pressure value of 150,000 pounds per square inch (PSI) and shaped to receive an O-ring.

Statement 17: The electric submersible pump Statement 15 or 16, wherein the exterior wall of at least one stackable diffuser wall forms the circumferential channel to receive the hardened steel ring.

Statement 18: The electric submersible pump any one of the preceding Statements 16-17, wherein the hardened steel ring is a split ring.

Statement 19: The electric submersible pump any one of the preceding Statements 16-18, wherein the hardened steel split ring comprises at least two pieces.

Statement 20: The electric submersible pump any one of the preceding Statements 16-19, wherein each piece of the hardened steel split ring has substantially equal dimensions.

Statement 21: The electric submersible pump any one of the preceding Statements 16-20, wherein ends of each piece of the hardened steel split ring abut against an end of an adjacent piece of the hardened steel split ring.

Statement 22: The electric submersible pump any one of the preceding Statements 16-21, where ends of each piece of the hardened steel split ring are angled and each end of the hardened steel split ring is shaped to mate with an angled end of an adjacent piece of the hardened steel split ring.

Statement 23: The electric submersible pump any one of the preceding Statements 16-22, wherein the hardened steel split ring further forms an O-ring channel on an exterior surface of the hardened steel split ring with the O-ring channel configured to receive an O-ring.

Statement 24: The electric submersible pump any one of the preceding Statements 16-23, further comprising an O-ring residing in the O-ring channel of the hardened steel split ring.

Statement 25: A electric submersible pump string comprising a tubing string, and an electric submersible pump (ESP) coupled with the tubing string, wherein the ESP comprises a housing having housing side walls, at least one stackable diffuser residing in the housing, each stackable diffuser having a diffuser side wall, and wherein the diffuser side wall has a circumferential channel comprising a material of greater strength than the remainder of the diffuser side wall.

Statement 26: The electric submersible pump string according to Statement 25, wherein the circumferential channel comprises a hardened steel ring having a minimum pressure value of 150,000 pounds per square inch (PSI) and shaped to receive an O-ring.

Statement 27: The electric submersible pump string according to Statement 26, wherein the hardened steel ring is a split ring comprising at least two pieces.

Statement 28: The electric submersible pump string according to Statement 27, wherein each piece of the hardened steel split ring has substantially equal dimensions.

Statement 29: The electric submersible pump string any one of the preceding Statements 27-28, wherein ends of each piece of the hardened steel split ring abut against an end of an adjacent piece of the hardened steel split ring.

Statement 30: The electric submersible pump string according to any one of the preceding Statements 27-29, where ends of each piece of the hardened steel split ring are angled and each end of the hardened steel split ring is configured to mate with an angled end of an adjacent piece of the hardened steel split ring.

The embodiments shown and described above are only examples. Even though numerous characteristics and advantages of the present technology have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, the disclosure is illustrative only, and changes may be made in the detail, especially in matters of shape, size and arrangement of the parts within the principles of the present disclosure to the full extent indicated by the broad general meaning of the terms used in the attached claims. It will therefore be appreciated that the embodiments described above may be modified within the scope of the appended claims.

ELECTRIC SUBMERSIBLE PUMP

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