ELECTRICAL SUBMERSIBLE PUMP WITH GAS VENTING SYSTEM

Abstract

A system and method for receiving hydrocarbons from a hydrocarbon reservoir into a shroud that encapsulates an electrical submersible pump (ESP) system in a wellbore, wherein the hydrocarbons separate within the shroud into gaseous components and liquid components, and flowing via the ESP the liquid components through production tubing and a jet pump to the surface, and drawing by the jet pump the gaseous components into the production tubing towards the surface.

Claims

1. A well tool system comprising: an electrical submersible pump (ESP) system comprising: an ESP configured to be positioned in a wellbore formed through a surface of Earth into a hydrocarbon reservoir, the ESP configured to receive hydrocarbons that enter the wellbore from the hydrocarbon reservoir and to flow the hydrocarbons through production tubing to the surface from an uphole end of the ESP; and an ESP motor operatively coupled to the ESP to drive the ESP to flow the hydrocarbons through the production tubing to the surface; a shroud configured to encapsulate and fluidically seal the ESP system in the wellbore, wherein an uphole end of the shroud is configured to couple to the production tubing, wherein gaseous components of the hydrocarbons separate from liquid components of the hydrocarbons in the shroud, and wherein the shroud comprises a sealing assembly to form a fluidic seal at the uphole end of the downhole shroud; and a jet pump configured to be positioned uphole of the ESP along the production tubing to draw the gaseous components into the production tubing towards the surface.

2. The system of claim 1, wherein the jet pump is configured to be positioned within the shroud downhole of the uphole end of the shroud, and wherein to draw the gaseous components into the production tubing comprises to draw the gaseous components from within the shroud.

3. The system of claim 1, wherein the jet pump is configured to be positioned uphole of the shroud, wherein a top of the shroud comprises ports to leak the gaseous components that accumulate in the shroud to uphole of the shroud, and wherein to draw the gaseous components into the production tubing comprises to draw the gaseous components from uphole of the shroud.

4. The system of claim 1, wherein the jet pump is configured to be positioned axially in-line with the production tubing, wherein the jet pump comprises a venturi configured to generate a pressure differential in response to the hydrocarbons comprising the liquid components flowing through the venturi, the pressure differential sufficient to draw the gaseous components into the production tubing towards the surface.

5. The system of claim 1, comprising: vent line tubing fluidically coupled to the shroud and the production tubing, the vent line tubing configured to flow the gaseous components from the shroud to the production tubing; and a valve disposed along the vent line tubing between the shroud and the production tubing to control flow of the gaseous components through the vent line tubing from the shroud to the production tubing in response to pressure in the shroud or in response to volume percentage of gas in the hydrocarbons at an inlet of the ESP, or a combination thereof.

6. The system of claim 5, wherein the vent line tubing is fluidicially coupled to the jet pump.

7. The system of claim 1, comprising: vent line tubing fluidically coupled to the shroud and the jet pump, the vent line tubing configured to flow the gaseous components from the shroud to the jet pump for the jet pump to draw the gaseous components into the production tubing towards the surface; and a valve disposed along the vent line tubing between the shroud and the production tubing to control flow of the gaseous components through the vent line tubing from the shroud to the jet pump in response to pressure in the shroud or in response to volume percentage of gas in the hydrocarbons at an inlet of the ESP, or a combination thereof.

8. A method comprising: receiving hydrocarbons from a hydrocarbon reservoir into a shroud that encapsulates and fluidically seals an electrical submersible pump (ESP) system, the ESP system comprising an ESP and an ESP motor, wherein the ESP system is positioned in a wellbore that is formed through a surface of Earth into the hydrocarbon reservoir, and wherein the hydrocarbons separate within the shroud into gaseous components and liquid components; sealing, by a sealing assembly, an uphole end of the shroud; flowing, via the ESP, the liquid components through production tubing to the surface, wherein the liquid components flow through a jet pump disposed along the production tubing uphole of the ESP; and drawing, by the jet pump, the gaseous components into the production tubing towards the surface.

9. The method of claim 8, wherein the jet pump is positioned axially in-line with the production tubing, and wherein the jet pump comprises a venturi.

10. The method of claim 9, comprising generating a pressure differential in response to the liquid components flowing through the venturi, wherein the pressure differential is sufficient to draw the gaseous components into the production tubing towards the surface.

11. The method of claim 8, wherein the jet pump is positioned within the shroud downhole of the uphole end of the shroud, and wherein drawing, by the jet pump, the gaseous components into the production tubing comprises drawing, by the jet pump, the gaseous components from within the shroud.

12. The method of claim 8, comprising leaking the gaseous components that accumulate in the shroud through ports in a top of the shroud into uphole of the shroud, wherein the jet pump is positioned uphole of the shroud, and wherein the jet pump drawing the gaseous components into the production tubing comprises the jet pump drawing the gaseous components from uphole of the shroud.

13. The method of claim 8, wherein drawing, by the jet pump, the gaseous components into the production tubing comprises flowing the gaseous components through vent line tubing from the shroud to the production tubing.

14. The method of claim 13, comprising controlling, via a valve disposed along the vent line tubing, flow of the gaseous components through the vent line tubing in response to pressure in the shroud or in response to volume percentage of gas in the hydrocarbons at an inlet of the ESP, or a combination thereof.

15. The method of claim 13, wherein the vent line tubing is fluidically coupled to the jet pump.

16. The method of claim 8, wherein drawing, by the jet pump, the gaseous components into the production tubing comprises flowing the gaseous components through vent line tubing from the shroud to the jet pump.

17. The method of claim 16, comprising controlling, via a valve disposed along the vent line tubing, flow of the gaseous components through the vent line tubing in response to pressure in the shroud or in response to volume percentage of gas in the hydrocarbons at an inlet of the ESP, or a combination thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1A is a schematic of an example of an electrical submersible pump (ESP) system.

[0024] FIG. 1B is a schematic of an example of a shroud to be coupled to the ESP system of FIG. 1A.

[0025] FIG. 1C is a schematic of an example of the ESP system of FIG. 1A coupled to the shroud of FIG. 1B positioned in a schematic of an example of a wellbore.

[0026] FIG. 2 is a schematic of a vent line to carry accumulated gas to a surface.

[0027] FIG. 3 is a schematic of two vent lines to carry accumulated gas to the surface.

[0028] FIG. 4 is a schematic of a jet pump to draw gas through vent lines.

[0029] FIG. 5 is a schematic of valves to control flow of gas through vent lines.

[0030] FIG. 6 is a flowchart of an example of a process of preventing gas lock in an ESP.

[0031] FIG. 7 is a schematic of an example of an implementation of an ESP system.

[0032] FIG. 8 is a schematic of an example of an implementation of an ESP system.

[0033] FIG. 9 is a schematic of an example of an implementation of an ESP system.

[0034] FIG. 10 is a schematic of an example of an implementation of an ESP system.

[0035] FIG. 11A is a schematic of an example of an implementation of an ESP system.

[0036] FIG. 11B is a cross-sectional view of the schematic of FIG. 11A.

[0037] Like reference numbers and designations in the various drawings indicate like elements.

DETAILED DESCRIPTION

[0038] In a wellbore in which an ESP is implemented, a gas lock may occur when liquid and gas separate in the tubing above the ESP or inside the ESP itself. Gas locking occurs when the pump is unable to lift the fluid column in the tubing above. The net result of excessive gas at the pump intake is that the gas can potentially accumulate into a long continuous column in the pump, thereby impeding the pumps ability to generate discharge pressure. In cases in which the pump does not actually gas lock, the pump can suffer head degradation and low efficiency when high vapor-to-liquid ratios are being pumped. Thus, ESP performance is limited by the amount of free gas that could be tolerated before gas locking would occur. Such gas locking can cause a catastrophic failure of the ESP because the pump is no longer moving fluid, resulting in overheating of the ESP during normal operation. Some techniques to minimize the possibility of or avoid gas lock include separating the gas from the fluid prior to entering the pump inlet or creating gas handling pumps which can pump larger gas by volume percentages of up to 70% before pump head degradation and gas locking occurs. Another technique is to ensure that the pump intake pressure remains above the bubble point pressure of fluid being produced.

[0039] This disclosure describes an ESP system encapsulated inside a shroud. Any gas will accumulate at the top of the shroud and will then be vented into the production tubing by a vent line. The vent line will enter the production tubing below the wellhead where the minimum pressure in the tubing exists compared to any other points in the tubing because of friction loss. Friction loss (or skin friction) is the loss of pressure or “head” that occurs in a tubing due to the effect of the fluid's viscosity near the surface of the tubing. The components described in this disclosure, for example, the ESP, the ESP motor, the shroud, and other components, are downhole components designed and constructed to operate in a downhole environment. That is, each component is ruggedized and constructed to operate, without failing, under the downhole environment which can include higher pressure or temperature compared to a surface of the Earth. Each component is also constructed to operate, without failing, in the presence of or upon contacting well fluids including hydrocarbons and debris, for example, subterranean zone rock or other debris, carried by the well fluids.

[0040] FIG. 1A is a schematic of an example of an electrical submersible pump (ESP) system 102. The ESP system 102 includes an ESP 103 and an ESP motor 105 that is operatively coupled to the ESP 103 to drive the ESP 103. In some implementations, the ESP 103 can be a middle or upper tandem model pump of any volume. Physical parameters and volumetric capacities of pumps from which the ESP 103 can be selected are shown in the table below:

TABLE-US-00001 Pump Outer Flow Range (cubic meters Diameter per day) @ best (inches) efficiency point (BEP) 5.38  227-1521 5.62 2053-3852 6.74 1267-1921

[0041] The ESP motor 105 can be a lower tandem model motor. Physical parameters and operational ranges of motors from which the ESP motor 105 can be selected are shown in the table below:

TABLE-US-00002 Motor Outer Name Plate Name Plate Diameter Horsepower @ Voltage Range @ Amperage Range @ (inches) 60 Hertz 60 Hertz 60 Hertz 5.43 480 1201-2525 94-43 5.62 210 2490-3720 52-34 5.62 441 2406-3855 111.4-69.6 

[0042] FIG. 1B is a schematic of an example of a shroud 104 to be coupled to the ESP system 100 of FIG. 1A. The shroud 104 has a hollow body 107 having an axial length greater than an actual length of the ESP system 102 and an inner radius greater than an outer radius of the ESP system 102. The dimensions of the body 107 are selected to receive the ESP system 102 within the hollow portion of the body. In some implementations, a minimum clearance between the outer surface of the ESP system 102 and the inner surface of the body 107 can be substantially 0.5 inches, where “substantially” represents a variation of 5% in the clearance. The shroud 104 has a downhole end portion 109 that is attached to the downhole end of the body 107. A sealing assembly 113a forms a fluidic seal between the downhole end portion 109 and tubing through which hydrocarbons 101 (FIG. 1C) are flowed to the ESP system 102. For example, the sealing assembly 113a can be a POD bottom sub of 7⅝″. The shroud 104 has an uphole end portion 111 that is attached to the uphole end of the body 107. A sealing assembly 113b forms a fluidic seal between the uphole end of the body 107 and the downhole end of the uphole end portion 111. For example, the sealing assembly 113b can be a POD hanger sub-assembly.

[0043] FIG. 1C is a schematic of an example of the ESP system 100 of FIG. 1A coupled to the shroud 104 of FIG. 1B positioned in a schematic of an example of a wellbore. The wellbore can be formed from a surface to a depth in a subterranean zone, which can include a formation, a portion of a formation or multiple formations. At the depth, the subterranean zone can include entrapped hydrocarbons 111 (for example, oil, gas, combinations of them or other hydrocarbons) which can be raised to the surface using the ESP system 102. The wellbore can be cased (for example, along an entire length of the wellbore or along a portion or portions of the length of the wellbore) or can be uncased. For example, the wellbore can be cased at least along the portion of the wellbore in which the ESP system 100 is disposed, and can be cased or uncased in other portions of the wellbore. As described earlier, the ESP system 102, which includes the ESP 103 and the ESP motor 105, can be positioned within the shroud 104 and sealed at the downhole end portion 109 and the uphole end of the body 107 using the sealing assemblies 113a and 113b, respectively. The shroud 104, carrying the ESP system 102, can then be positioned within the wellbore, for example, at a depth at which the ESP system 102 is to be operated to lift the hydrocarbons 101 to the surface of the wellbore.

[0044] In some implementations, a packer 112a is positioned uphole of the ESP system 102 and is coupled to the uphole end portion 111 of the shroud 104. The packer 112a fluidically isolates the portion of the wellbore (or, if the wellbore is cased, the portion of the casing 114) uphole of the packer 112a from the portion downhole of the packer 112a. The packer 112a can include an opening through which the uphole end portion 111 can pass. In some implementations, the packer 112a can be a deep set packer that can protect the casing annulus from contact with the hydrocarbons 111 and also serve as a barrier for well control. The packer 112a can include a packer penetrator system through which cables (for example, power cables or cable carrying other information) can be passed to the ESP motor 105. For example, the packer 112a can be a production packer with feedthrough ports for receive and pass through extension leads to the ESP motor 105.

[0045] In some implementations, a packer 112b is positioned downhole of the ESP system 102. Similar to the packer 112a, the packer 112b creates a fluidic isolation between portions uphole and downhole of the packer 112b. The packer 112b can include an opening through which tubing 115 through which the hydrocarbons 111 flow, can be passed to fluidically and sealingly couple to the bottom end portion 109 of the shroud 104. In some implementations, the packer 112b can be a permanent packer, that is, a mechanical packer with large packing surfaces that enables isolation of several zones. The packer 112b offers necessary anchoring to the ESP system 100. The packer 112b can connect, in sequence, with other well tools, for example, a hydraulic disconnect tool, a telescope joint, handling sub, cross overs and the sealing assembly 113a. In this manner, the packer 112b directs the hydrocarbons 111 released from the subterranean zone into the tubing 115, which then carries the hydrocarbons 111 into the shroud 104 to be received by the ESP system 102. The intake 102 of the ESP 103 draws the hydrocarbons 111 to be lifted to the surface and flows the hydrocarbons 111 into a production tubing 208 (FIG. 2) that is uphole of the shroud 104. The shroud 104 fills with the hydrocarbons 111, which can include multi-phase fluids, that is, fluids with gas and liquid components. Over time, the gaseous components 108 can rise to the uphole portion of the body 107 while the liquid components 110 settle to the downhole portion of the body 107. Because the shroud 104 is fluidically sealed at the uphole and downhole ends, the pressure on the gaseous components 108 can increase as the volume of the liquid components 110 in the shroud 104 increases. If not vented, then the gaseous components 108 can enter the ESP 103 causing gas lock.

[0046] FIG. 2 is a schematic of a vent line to carry accumulated gas to a surface. In some implementations, a vent line 202 can be operatively connected to the shroud to carry the gaseous components 108 from within the body 107 of the shroud 104 to the surface of the wellbore. The vent line 202 can include tubing designed and constructed to fluidically couple, on one end 200, to an inner volume of the body 107 of the shroud 104. For example, the vent line can be manufactured using a material that can resist corrosion, for example, due to hydrogen sulfide, carbon dioxide or other gases that can flow through the vent line. The vent line 202 can pass through the packer 112A and the sealing assembly 113b to fluidically couple to the body 107 at the end 200. Swage locks (for example, about ¾ inches in size) can be used to maintain a seal at the opening 200 so that the gas does not leak out of the shroud. The other end 206 of the vent line 202 is connected to the production tubing 208 that carries the hydrocarbons 111 to the surface. In some implementations, a vent valve is used to couple the other end 206 of the vent line 202 with the production tubing 208. The vent valve maintains a seal at the other end 206. In some implementations, the vent line 202 can extend as close to the surface (for example, to the base of the wellhead 204) as possible before reconnecting with the production tubing 208. At this location, the fluidic pressure within the vent line 202 at this location will be less than that in other, comparatively downhole locations due to friction loss. Alternatively, the other end 206 can be reconnected to the production tubing 208 at any location uphole of the packer 112a.

[0047] The vent line 202 can also include a venting mechanism 201, for example, a vent valve. As described earlier, the gaseous components 108 can accumulate in an uphole end of the body 107. The venting mechanism 201 can vent the gaseous components 108 into the vent line 202 through the opening 200. In this manner, the gaseous components 108 can exit the body 107, thereby decreasing a pressure and quantity of the gaseous components 108 in the shroud 107. Subsequently, the venting mechanism 201 can close the opening 200 allowing the gaseous component 108 to once again fill the body 107. This cycle of filling and venting can continue thereby preventing the gaseous component 108 from entering the pump intake 106 (FIG. 1) and causing gas lock. The venting mechanism 201 can be positioned within the shroud 107, outside the shroud 107 immediately uphole of the shroud 107, nearer to a surface of the wellbore, or at any position in between.

[0048] The venting mechanism 201 can be implemented as a pressure valve. For example, the venting mechanism 201 can be a mechanically operated vent valve. When the pressure near an uphole end of the body 107 due to the gaseous component 108 increases beyond a threshold pressure, the venting valve can open to release the gaseous component 108 into the vent line 202. Release of the gaseous component 108 decreases the pressure in the body 107 causing the venting valve to close. Alternatively or in addition, the venting mechanism 201 can be a valve controllable using programmable logic control (PLC). Such a valve can include a spring and an electric magnet that is actuated by a programmable logic controller that sends a signal to the valve to open or close through a wire cable 205 connected to the valve, the wire cable fed through ports in the packer 112a. In such implementations, the programmable logic can include one or more of several factors including, for example, the pressure inside the body 107, volume percentage of gas in the fluid at the inlet of the ESP 103, combinations of them or other factors. Also, in some implementations, the programmable logic controller can be included in the surface of the drive of the ESP 103.

[0049] FIG. 3 is a schematic of two vent lines to carry accumulated gas to the surface. The first vent line can be identical to the vent line 202 described earlier with reference to FIG. 2. The second vent line 302 can be substantially identical to the vent line 202. The second vent line 202 can include an opening 300, substantially identical to the opening 200, to fluidically couple the second vent line 302 to the body 107 and another opening 306, substantially identical to the opening 206, to fluidically couple the second vent line 302 to the production tubing 306. The second vent line can include a second venting mechanism 301 substantially identical to the first venting mechanism 201.

[0050] FIG. 4 is a schematic of a jet pump 402 to draw gas through vent lines. The jet pump 402 can be positioned uphole of the shroud 104, for example, immediately below the base of the wellhead 204, and in-line with the production tubing 114. The hydrocarbons 111 lifted by the ESP system 102 can be flowed through the production tubing 114 and through the jet pump 402 before exiting the wellbore through the wellhead 204. In some implementations, the jet pump 402 can have an eductor design, that is, a venturi-like construction whereby a cross-sectional flow area of the jet pump 402 decreases, then increases in the flow direction of the hydrocarbons 111. The openings 206 and 306 of the vent lines 202 and 302, respectively, can be fluidically coupled to the uphole end of the jet pump 402 before the decrease in the cross-sectional flow area. As the hydrocarbons 111 flow through the jet pump 402, the change in the cross-sectional area causes a change in the differential pressure in the vent lines 202 and 302 causing the gaseous components 108 in the body 107 to be sucked in the uphole direction through the openings 200 and 300, respectively.

[0051] Similar to the implementation of FIG. 3, the implementation of FIG. 4 shows two vent lines 202 and 302, including corresponding openings 200 and 300, respectively, connected to the body 107 of the shroud 104, and openings 206 and 306, respectively, connected to the production tubing 114. Alternatively, the jet pump 402 can be implemented using one vent line or with more than two vent lines.

[0052] FIG. 5 is a schematic of a valve system including valves to control flow of gas through vent lines. In some implementations, a valve can be operatively connected to each vent line (for example, valve 502a in vent line 202, valve 502b in vent line 302) to control the flow of gaseous components 108 to the production tubing 114. The valve can be an on/off nozzle-type venting valve fluidically coupled to the vent line immediately above the shroud 104. The valve system includes a valve controller to control the valve. In some implementations, the valve controller can be implemented as computer instructions stored on a computer-readable medium and executable by one or more processors. For example, the valve controller can determine free gas at the pump intake 106 using one or more sensors, for example, a pressure sensor, a volume sensor, temperature sensor, any combination of them or other sensors. In some implementations, any one or more or all of the venting mechanism 201, the venting mechanism 302, the valve 502a or the valve 502b can include the one or more sensors. The venting mechanisms (or valves) can be non-return valves that are normally in a closed state. The sensors can sense parameters of the fluids at the inlet of the ESP 103 or parameters inside the body 107 or parameters of the fluid inside the body 107 (or other parameters), and transmit the sensed parameters (for example, pressure, volume, temperature) to the valve controller (for example, the programmable logic controller) at the surface. The valve controller receives the sensed parameters and compares the same with stored threshold parameters. Based on a result of the comparison, the valve controller can transmit a signal to the venting mechanism (or the valves) to open if closed, to close is open, to remain open or to remain closed. For example, when the valve controller determines that the volume percentage of free gas is at or exceeds a certain threshold (for example, 25% or more volume percentage), then the valve controller can transmit an instruction to the valve to open. When the valve controller determines that the volume percentage of free gas it at or less than a certain threshold (for example, 10% or less volume percentage), then the valve controller can transmit an instruction to the valve to close.

[0053] FIG. 6 is a flowchart of an example of a process 600 of preventing gas lock in an ESP. At 602, hydrocarbons from a hydrocarbon reservoir are received in a shroud encapsulating and fluidically sealing an ESP system. The ESP system is positioned in a wellbore. The hydrocarbons are separated into gaseous components and liquid components within the shroud. At 604, the hydrocarbons are flowed through vent line tubing toward a surface of the wellbore before the gaseous components flows into the ESP system. In this manner, gas lock in the ESP system can be prevented.

[0054] FIG. 7 is a schematic of an example of an implementation of an ESP system. The ESP system includes the shroud 104, the sealing assembly (for example, the packer 112a) uphole of the shroud 104, a vent line 202 passing through the sealing assembly to transfer fluids collected in the shroud 104 to portions uphole of the shroud 104 and a jet pump 402 positioned immediately below the wellhead to draw the fluids accumulated in the shroud 104 toward the surface. The ESP system also includes a gas handler 702 that can retain the free gas into the liquid in the shroud 104 before the gas enters the pump. The gas handler 702 is a mechanical device that contains multiple axial screw type impellers and diffusers. The flow volume (oil+gas) is compressed in the axial type impellers that breaks the gas bubbles into smaller gas bubbles in the diffuser. This action results in homogeneous gas-liquid mixture without jeopardizing the ESP operation to gas lock, that is, the stoppage of ESP production due to gas accumulation at the intake of the ESP. Then, the gas-liquid fluid is pushed into the ESP stages with no gas lock. To support the gas handler 702, in some implementations, a gas separator can be added below the gas handler 702 and above the pump intake 106. In some implementations, the jet pump 402 can be positioned within the shroud 104, for example, downhole of the uphole end 111 of the body 107 of the shroud 104.

[0055] FIG. 8 is a schematic of an example of an implementation of an ESP system. The ESP system of FIG. 8 is substantially similar to that of FIG. 7 except that the former does not include a shroud 104. In some implementations, the ESP system includes a power cable 802 that can run from the surface through the sealing assembly, for example, the packer 112a, to the ESP motor 105 to transmit instructions to the ESP motor 105. In some implementations, the ESP system can include a seal 804 that fluidically seals the ESP motor 105 from the fluids that flow into the ESP. The power cable 802 can additionally exchange data instructions with the ESP motor 105. In some implementations, the ESP system can include one or more sensors 806 that can transmit sensed information to the surface through the power cable 802. The ESP motor 105 can be operated based on, that is, in response to, the signals sensed by the sensor 806. FIG. 9 is a schematic of an example of an implementation of an ESP system. The schematic of FIG. 9 is substantially similar to that of FIG. 8 except that the former excludes the gas handler 702. FIG. 10 is a schematic of an example of an implementation of an ESP system. The schematic of FIG. 10 is substantially similar to that of FIG. 9 except that the jet pump 402 is downhole of the sealing assembly, that is, the packer 112a, and is open to the annulus directly and without a venting line. In such an implementation, the jet pump 402 is configured to draw the gases accumulated below the packer 112a into the production tubing and push the gases towards the surface. FIG. 11A is a schematic of an example of an implementation of an ESP system. The schematic of FIG. 11 is substantially similar to that of FIG. 10 except that the schematic includes a shroud similar to the shroud 104. In addition, as shown in the cross-sectional view of FIG. 11B, the top of the shroud includes ports 1102 to leak gas that accumulates in the shroud to an uphole region uphole of the shroud where the gas is drawn into the jet pump 402 to be raised to the surface. In some implementations, the jet pump 402 can be positioned within the shroud 104, for example, downhole of the uphole end 111 of the body 107 of the shroud 104.

[0056] Thus, particular implementations of the subject matter have been described. Other implementations are within the scope of the following claims.