WO2014165183A2

WO2014165183A2 - Steam generation assembly for foul fluids or fluids having impurities

Info

Publication number: WO2014165183A2
Application number: PCT/US2014/024680
Authority: WO
Inventors: John David Penton
Original assignee: Chevron U.S.A. Inc.
Priority date: 2013-03-13
Filing date: 2014-03-12
Publication date: 2014-10-09
Also published as: US20140261244A1; WO2014165183A3

Abstract

A steam generation assembly is provided for producing steam with foul or unclean fluids for use in operations. The heat is transferred to the foul fluid from a clean steam flowing through a tube bundle and is circulated through a closed loop steam generation system. The tube bundle extends within an outer shell that collects the foul fluid for heat transfer. Outer shell includes a larger volume below the tube bundle than convention heat exchangers so that any particulates and emulsions can gather below the tube bundle rather than attaching or forming on its surface.

Description

STEAM GENERATION ASSEMBLY FOR

FOUL FLUIDS OR FLUIDS HAVING IMPURITIES

RELATED APPLICATION

[0001] This application claims the benefit of, and priority to U.S. Provisional Patent Application No. 61/ 779,493 filed on March 13, 2013, which is herein incorporated in its entirety by reference.

FIELD OF THE INVENTION

[0002] The present invention is generally related to steam generation, and more particularly, to steam generation for use in oil and gas production, transportation, upgrading, and refining operations.

BACKGROUND OF THE INVENTION

[0003] Steam is used in the industry for a variety of purposes. In certain situations, for example in the oil and gas industry, the steam is injected into either a reservoir, a produced fluid from a reservoir or a chemical being processed upon which the steam reacts. For example, the steam can be injected into a reservoir having what is generally described as "heavy oil" in order to help the production of the oil from the reservoir. In other situations, the steam can be mixed with heavy oil that is already produced in order to change the viscosity of the heavy oil such that it is easier to transport. Similarly, steam can also be mixed with the produced oil in upgrading and refining operations. In each of these scenarios, it is less expensive if the water being turned to steam does not have to be treated such that it is substantially free of impurities. However, in the production of steam such "dirty water" can cause the buildup of impurities in the steam production equipment. This build up of impurities is also known as fouling.

[0004] It is most common that the fouling is from scaling. This scaling be large pieces of foulant appearing somewhat like shale. The deposition of such products can plug the free spaces in the equipment, for example the heat exchanger, and thereby prevent the proper circulation of water. This, in turn, leads to even more severe fouling and a reduction in the steam generating capacity. Therefore, it can be advantageous to first to heat up a clean fluid that is substantially free of impurities in a closed-loop system, and then transfer the heat from the clean fluid to the fluid that is to be used in the operations. Separating the fluids in such a fashion helps to mitigate the effects of fouling in the equipment used to generate heat for the production of steam. However, there remains the issue of fouling occurring where the heat is transferred from the clean fluid in the closed loop system to the dirty water.

[0005] Adding chemical to the dirty water or fluid is one way that has been tried to reduce the occurrence of fouling. However, the use of such chemicals has also caused the problem to get worse, and the chemicals may not be appropriate for the desired use of the steam. Additionally, chemical solutions, when they work to reduce fouling, usually do not work for long periods of time. Therefore, the chemical treatment must be repeated and does not provide a long-term solution. Another way to counter the effects of fouling is an accelerated maintenance schedule. However, the downtime associated with such accelerated scheduling is a loss of productivity.

[0006] It would be desirable to have a way to mitigate the formation of fouling in such steam generation systems such that the systems do not need to have chemicals added to the dirty water and do not force maintenance shutdowns ahead of standard shutdowns for the rest of the system.

SUMMARY

[0007] One aspect of the invention is a steam generation assembly that includes an outer shell having an open end portion and a closed end portion positioned opposite from the open end portion. The closed end portion has a larger circumference than the open end portion. The outer shell has an enlarging section near the open end portion that increases in circumference while extending farther from the open end portion. A bundle of tubes extends into the outer shell. The bundle of tubes extends from a connector assembly that is connected to the open end portion of the outer shell. The bundle of tubes receives steam substantially free of impurities from a connector assembly inlet, and delivers cooled fluid to a connector assembly outlet after the steam communicates through the bundle of tubes. An inlet port is formed in an upper surface of the outer shell that is offset from an axis of the bundle of tubes. The inlet port communicates a fluid having impurities, such impurities being greater than the steam provided to the connector assembly inlet, into the outer shell for conversion to steam through heat transfer with the bundle of tubes. An outlet port is formed at an uppermost surface of the outer shell to receive and communicate steam from the outer shell. A drainage port formed in the lowermost surface of the outer shell to communicate liquid from the outer shell.

[0008] The steam generation assembly can have fluid within the outer shell that is maintained below a highest liquid level, the highest liquid level being lower than the inlet port. The steam generation assembly can have fluid within the outer shell that is maintained at a normal liquid level that is below a highest liquid level, the highest liquid level being lower than the inlet port. The normal liquid level can be above a highest portion of the bundle of tubes such that the bundle of tubes is submerged. The fluid within the outer shell can be maintained at a normal liquid level that is below a highest liquid level through selectively communicating the fluid having impurities through the inlet port and liquid through the drainage port.

[0009] The steam generation assembly can also include an access port formed in the outer end portion of the outer shell. The access port being large enough for an operator to enter the outer shell during workover operations.

[0010] The connector assembly can be connected to the open end portion of the outer shell with a flange connection. The steam generation assembly can also include a bridle formed in the outer shell for positioning a sensor to monitor steam generation within the outer shell. The bridle can be used for measuring such values as pressure and temperature within the outer shell.

[0011] The outer shell can also include an axis extending from the open end portion to the closed end portion. The bundle of tubes can extend coaxially through the outer shell with an axis of the outer shell. The axis of the bundle of tubes can be offset from an axis of the outer shell. The axis of the bundle of tubes can be above the axis of the outer shell such that a volume of fluid carried within the outer shell below the bundle of tubes is increased.

[0012] Another aspect of the invention includes a steam generation assembly having an outer shell with an open end portion and a closed end portion positioned opposite from the open end portion. The closed end portion has a larger circumference than the open end portion.

The outer shell having an enlarging section near the open end portion that increases in circumference while extending farther from the open end portion. A bundle of tubes extends into the outer shell from a connector assembly that is connected to the open end portion of the outer shell. The bundle of tubes receives steam substantially free of impurities from a connector assembly inlet, and delivers cooled fluid to a connector assembly outlet after the steam communicates through the bundle of tubes. A liquid is carried within the outer shell.

The liquid has more impurities than the steam provided to the connector assembly inlet. The liquid has a highest liquid level and a normal liquid level. The highest and normal liquid levels are both above the bundle of tubes such that the bundle of tubes is fully submerged in the liquid during operation. An inlet port formed in an upper surface of the outer shell that is offset from an axis of the bundle of tubes. The inlet port communicates a fluid into the outer shell into the outer shell for conversion to steam through heat transfer with the bundle of tubes. Any liquid in the fluid combines with the liquid carried within the outer shell. An outlet port is formed at an uppermost surface of the outer shell to receive and communicate steam from the outer shell. A drainage port is formed in the lowermost surface of the outer shell to communicate liquid from the outer shell.

[0013] The fluid within the outer shell can be maintained at the normal liquid level that is below the highest liquid level through selectively communicating the fluid having impurities through the inlet port and liquid through the drainage port. An access port can be formed in the outer end portion of the outer shell. The access port is preferably large enough for an operator to enter the outer shell during workover operations. The connector assembly can be connected to the open end portion of the outer shell with a flange connection.

[0014] The outer shell can also include an axis extending from the open end portion to the closed end portion. The bundle of tubes can extend coaxially through the outer shell with the axis of the outer shell.

[0015] Another aspect of the invention is a method for generating steam including providing an outer shell having an open end portion and a closed end portion positioned opposite from the open end portion. The closed end portion having a larger circumference than the open end portion with the outer shell having an enlarging section near the open end portion that increases in circumference while extending farther from the open end portion. Communicating a fluid into the outer shell through an inlet port formed in an upper surface of the outer shell. Extending a bundle of tubes into the outer shell from a connector assembly that is connected to the open end portion of the outer shell. Collecting the fluid in the outer shell with any liquid in the fluid covering the bundle of tubes. Communicating steam that is substantially free of impurities to the bundle of tubes from a connector assembly inlet. Transforming the liquid in the outer shell to vapor or steam by transferring the heat from the steam in the bundle of tubes to the liquid in the outer shell by communicating the steam from the connector assembly inlet through the bundle of tubes. Delivering cooled fluid from the bundle of tubes to a connector assembly outlet after the steam communicates through the bundle of tubes. Communicating the vapor from the outer shell though an outlet port formed at an uppermost surface of the outer shell. Maintaining the liquid at a level below the highest liquid level with a drainage port formed in the lowermost surface of the outer shell by communicating liquid from the outer shell. The liquid in the outer shell is separated at all times from the steam and cooled fluid carried within the bundle of tubes. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a perspective side view of a steam generation assembly in accordance with an embodiment of the present invention, with internal components being shown with dashed lines.

[0017] Figure 2 is a perspective view of the steam generation assembly of Figure 1 when view from line A-A.

DETAILED DESCRIPTION

[0018] Referring to Figure 1, a steam generating assembly 11 for use in foul or dirty water services is illustrated. Steam generating assembly 1 1 includes an outer shell 13 having a closed end portion 15 and an open end portion 17. In a preferred embodiment, closed and open end portions 15, 17 are formed opposite from each other. In the embodiment shown in Figure 1, closed and open end portions 15, 17 are formed around a common axis A of outer shell 13. However, it is envisioned in the scope of the present invention that closed and open end portions 15,17 can be offset from each other such that they are not centered around a common axis A.

[0019] Outer shell 15 increases in circumference in an enlarging section 21 when travelling from open end portion 17 toward closed end portion 15. In the embodiment shown in Figure

I, the circumference maintains its circumference in a middle portion 23 of outer shell 13. The combination of open end portion 17, the increasing circumference in enlarging section 21, the substantially uniform circumference throughout middle portion 23, and closed end portion 15 provides outer shell with a shape similar to an elongated kettle. A plurality of supports 25 a formed in a lower portion of outer shell 13 to provide support of outer shell 13 and any fluid contained therewithin.

[0020] An inlet port 27 is formed in middle portion 23 at an upper portion of outer shell 13. Inlet port 27 provides an inlet for the fluid F to be heated to enter steam generating assembly

I I . The fluid F can be liquid or a mixture of liquid and vapor in the event that some of the fluid had been preheated or re-circulated. The fluid F is typically water, but it can also be a combination of water and other fluids. The fluid F entering outer shell 13 will form a fluid line therewithin, which will preferably have a normal liquid level NLL that is maintained at or below a predetermined highest level of liquid HLL. Inlet port 27 is positioned above the highest liquid level HLL. As best shown in Figure 2, inlet port 27 is preferably positioned at an angle such that fluid entering outer shell 13 is offset from the vertical center of outer shell 13.

[0021] An outlet port 29 is formed in middle portion 23 at an upper portion of outer shell 13. Outlet port 29 receives and communicates the vapor or steam from steam generating assembly 1 1 for use in operations. Preferably, outlet port 29 is formed at the uppermost surface of middle portion 23 so that vapor or steam does not collect within outer shell 13. A plurality of instrument bridles 31 are also formed at various positions around outer shell 13 so that measurements such as pressure and temperature within outer shell 13 can be obtained.

[0022] A bundle of tubes, or tube bundle 33, is positioned inside of outer shell 13. Tube bundle 33 extends from open end portion 17 toward closed end portion 15 of outer shell 13. Tube bundle 33 preferably comprises conventional tubes utilized in heat exchangers. The inside of tube bundle 33 is not in fluid communication with the fluid F carried within outer shell 13. Tube bundle 33 receives and carries steam from the closed-loop steam generation operations, and transfers the heat to the fluid F within outer shell 13. Tube bundle 33 is preferably positioned such that all of tube bundle is below the normal liquid line NLL and is therefore submerged within fluid F during normal operations. Tube bundle 33 also conveys fluid out of outer shell 33 for recirculation in the closed-loop steam generation operations. Under typical operations, steam will enter tube bundle 33 and liquid will exit tube bundle 33 after passing within outer shell 13.

[0023] Outer shell 13 also comprises a drainage port 35 extending through a lower surface of outer shell 13. Drainage port 35 allows the operator to remove liquid fluid F from within outer shell 13 such that fluid F is below the highest liquid level HLL. Drainage port 35 also allows the operator to drain liquid completely from outer shell 13 for maintenance. An access port 38 is formed through a surface of outer shell 13 at closed end portion 15. Access port 38 is preferably large enough for an operator to enter outer shell 13 to perform maintenance operations after fluid F is drained through drainage port 35. Outer shell 13 preferably includes a flange positioned at open end portion 17 for connecting with the closed loop steam generation system.

[0024] A connector assembly 39 includes a flange 41 for connecting with flange 37 of outer shell 13. Connector assembly 39 receives steam that is made from clean fluid, or fluid that is substantially free of particulates, in the closed loop steam generation system. The fluid can be turned to steam in several convention ways, such as with a natural gas powered steam generator. Alternatively, the steam in the closed loop steam generation system can be produced with non-traditional or waste sources such as solar, geothermal, and process waste heat.

[0025] Connector assembly 39 includes a steam inlet 43 that receives the steam from the closed loop steam generation system, and connector assembly 39 communicates the steam from steam inlet to tube bundle 33. Connector assembly 39 also includes an outlet 45 that receives liquid or a mixture of liquid and vapor from tube bundle 33 after the fluid has traveled therethrough. Outlet 45 re-circulates the fluid exiting tube bundle 33 within the closed loop for steam generation.

[0026] As will be appreciated by those skilled in the art, there is necessarily a loss of efficiency when producing the steam within outer shell 13 from the heat carried by the steam provided from the closed loop steam generation system via connector assembly 39. Therefore, one skilled in the art would conventionally attempt to reduce any additional inefficiency by reducing the volume of fluid F surrounding tube bundle 33 during operations at any given time. In the present disclosure however, outer shell 13 is expanded through enlarging section 21 and maintained through middle portion 23. This increase in volume inherently reduces the efficiency of steam production within outer shell 13.

[0027] However, said increase in volume also provides an increased distance D between the lower surface of tube bundle 33 and the bottom surface within outer shell 13, as well as an increased volume V of the space below tube bundle 33 over that of a more efficient heat exchanger. Increased distance D and increased volume V advantageously provides a larger area for any fouling or particulates to collect within outer shell 13 without coming in contact with the surface of tube bundle 33. The collection area defined by the increased volume V, advantageously allows for longer operation between shutdowns for maintenance.

[0028] In operation, fluid F enters outer shell 13 through inlet port 27. Fluid F can be either a liquid or a mixture of liquid and vapor if fluid F was preheated. Fluid F enters outer shell 13 via inlet port 27 offset from the centerline of outer shell 13 such that fluid does not engage as much of tube bundle 33 when initially dropping into outer shell 13. Any particulates and emulsions are therefore allowed to settle within the collection area defined by increased volume V after minimal contact with the outer surface of tube bundle 33. The rest of fluid F collects and forms a liquid level line below the highest liquid level HLL but such that the normal liquid level NLL is above the upper surface of tube bundle 33. Any vapor in fluid F separates and collects above the liquid.

[0029] Steam produced within the closed loop steam generation system enters connector assembly 39 through steam inlet 43. The steam flows through connector assembly 39 and into tube bundle 33. While travelling through tube bundle 33, heat from the steam is communicated from the steam through the tube bundle 33 to the fluid F within outer shell 13. As the heat is transferred to fluid F, the liquid is vaporized and steam collects in the upper portion of outer shell 13 above the liquid line of fluid F. Outlet 29 receives the vapor or steam from outer shell 13 and communicates the produced vapor or steam for operations.

[0030] As the steam from the closed loop steam generation system flows through tube bundle 33 and transfers its heat to the fluid F within outer shell 13, the steam can condense and into a liquid or a mixture of liquid and vapor. This condensed fluid is carried back to connector assembly 39 by tube bundle 33 and re-circulated in the closed loop to be converted back to steam through outlet 45.

[0031] Steam generation assembly 11 advantageously separates the fluid being used for operations from the main steam generation equipment by using the clean steam to produce steam with the fluid used for operations. This allows the operator to reduce the amount of water or fluid treatment that must be performed on the fluids for operations. Additionally, steam generation assembly 11 also allows for longer operations because outer shell 13 includes a larger collection area defined by volume V than is provided in conventional heat exchangers. This additional operation time allows the operator to align maintenance operations of steam generation assembly 1 1 with that of other equipment rather than having to shut down operations early to remove any fouling and particulates.

[0032] Steam generation assembly 11 as described herein uniquely provides for a more reliable device with lower fouling potential and extended service times. As will be readily appreciated by those skilled in the art, steam generation assembly 11 has potentially broad application.

[0033] While the invention has been shown in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but susceptible to various changes without departing from the scope of the invention. For example, while outer shell 13 is shown as having a round cross section in Figure 2, outer shell 13 could also have an oblong cross section with tube bundle 33 being offset higher than the centerline of outer shell 13 to achieve the increased collection area below tube bundle 33.

Claims

CLAIMS That claimed is:

1. A steam generation assembly, comprising:

an outer shell having an open end portion and a closed end portion positioned opposite from the open end portion, the closed end portion having a larger circumference than the open end portion with the outer shell having an enlarging section near the open end portion that increases in circumference while extending farther from the open end portion; a bundle of tubes that extends into the outer shell, the bundle of tubes extending from a connector assembly that is connected to the open end portion of the outer shell, the bundle of tubes receiving steam substantially free of impurities from a connector assembly inlet and delivering cooled fluid to a connector assembly outlet after the steam communicates through the bundle of tubes;

an inlet port formed in an upper surface of the outer shell that is offset from an axis of the bundle of tubes, the inlet port communicates a fluid having impurities, such impurities being greater than the steam provided to the connector assembly inlet, into the outer shell for conversion to steam through heat transfer with the bundle of tubes;

an outlet port formed at an uppermost surface of the outer shell to receive and communicate steam from the outer shell; and

a drainage port formed in the lowermost surface of the outer shell to communicate liquid from the outer shell.

2. The steam generation assembly of claim 1, wherein fluid within the outer shell is maintained below a highest liquid level, the highest liquid level being lower than the inlet port.

3. The steam generation assembly of claim 1 , wherein fluid within the outer shell is maintained at a normal liquid level that is below a highest liquid level, the highest liquid level being lower than the inlet port.

4. The steam generation assembly of claim 3, wherein normal liquid level is above a highest portion of the bundle of tubes such that the bundle of tubes is submerged.

5. The steam generation assembly of claim 1, wherein fluid within the outer shell is maintained at a normal liquid level that is below a highest liquid level through selectively communicating the fluid having impurities through the inlet port and liquid through the drainage port.

6. The steam generation assembly of claim 1, further comprising an access port formed in the outer end portion of the outer shell, the access port being large enough for an operator to enter the outer shell during workover operations.

7. The steam generation assembly of claim 1, wherein the connector assembly is connected to the open end portion of the outer shell with a flange connection.

8. The steam generation assembly of claim 1, wherein the outer shell further comprises an axis extending from the open end portion to the closed end portion.

9. The steam generation assembly of claim 1, wherein the bundle of tubes extends coaxially through the outer shell with an axis of the outer shell.

10. The steam generation assembly of claim 1, wherein an axis of the bundle of tubes is offset from an axis of the outer shell.

1 1. The steam generation assembly of claim 10, wherein the axis of the bundle of tubes is above the axis of the outer shell such that a volume of fluid carried within the outer shell below the bundle of tubes is increased.

12. The steam generation assembly of claim 1, further comprising a bridle formed in the outer shell for positioning a sensor to monitor steam generation within the outer shell.

13. A method for generating steam, comprising:

(a) providing an outer shell having an open end portion and a closed end portion positioned opposite from the open end portion, the closed end portion having a larger circumference than the open end portion with the outer shell having an enlarging section near the open end portion that increases in circumference while extending farther from the open end portion;

(b) communicating a fluid into the outer shell through an inlet port formed in an upper surface of the outer shell; (c) extending a bundle of tubes into the outer shell from a connector assembly that is connected to the open end portion of the outer shell;

(d) collecting the fluid in the outer shell with any liquid in the fluid covering the bundle of tubes;

(e) communicating steam that is substantially free of impurities to the bundle of tubes from a connector assembly inlet;

(f) transforming the liquid in the outer shell to vapor by transferring the heat from the steam to the liquid in the outer shell by communicating the steam from the connector assembly inlet through the bundle of tubes;

(g) delivering cooled fluid from the bundle of tubes a connector assembly outlet after the steam communicates through the bundle of tubes;

(h) communicating the vapor from the outer shell though an outlet port formed at an uppermost surface of the outer shell; and

(i) maintaining the liquid at a level below the highest liquid level with a drainage port formed in the lowermost surface of the outer shell by communicating liquid from the outer shell.

14. The method of claim 13, wherein the liquid in the outer shell is separated at all times from the steam and cooled fluid carried within the bundle of tubes.