Patent Application
20210277761
The present disclosure relates in general to the development of subterranean wells, and more particularly to reducing levels of hydrogen sulfide of a produced fluid within the subterranean well.
When developing hydrocarbons from subterranean wells, hydrogen sulfide (H2S) can be encountered. Some hydrocarbon wells can contain a relatively high concentration of hydrogen sulfide, which is also known as acid gas or sour gas. Hydrogen sulfide can be toxic and corrosive and requires that safety precautions be undertaken if the hydrogen sulfide reaches the surface. An elevated amount of hydrogen sulfide poses a risk to operating personnel and the population in nearby areas. Any release of hydrogen sulfide in the atmosphere can cause environmental damage and injury to other people or animals.
Hydrogen sulfide can also increase the risk of surface equipment failure. Hydrogen sulfide can cause sulfide stress cracking. Hardened steel is more susceptible to sulfide stress cracking at lower temperatures. High strength carbon steel becomes brittle when exposed to sulfide stress cracking and develops cracks, which can lead to failure of the components formed of such steel. Surface equipment on a drilling rig or production facilities can require the use special hydrogen sulfide resistant steel and rubber elements to avoid catastrophic failure or the release of poisonous gas in and around working area.
In exploratory wells the exact concentration of hydrogen sulfide may not be known until surface measurements are carried out. Exploratory wells are drilled in an undeveloped area for discovering new reservoirs and collecting subsurface geological data. After an exploratory well is drilled to the planned target depth, the well is tested. Well testing can be carried out for evaluating the reservoir potential. In some current developments, conclusive measurements for making appropriate reservoir evaluation can be made only if formation fluid is flowed to surface.
The existence of amounts of hydrogen sulfide in the reservoir fluid can restrict the ability of an operator to safely flow a well to the surface and to carry out a proper evaluation of reservoir potentials. It can be risky to perform drill stem tests on wells with elevated amounts of hydrogen sulfide and as a result, some drill stem tests are aborted before being completed if higher concentrations of hydrogen sulfide are detected during the test.
Embodiments of this disclosure can neutralize a part or all of the hydrogen sulfide downhole during flowback. By reducing the concentration of hydrogen sulfide being produced to the surface the flow testing on the well can be completed.
In an embodiment of this disclosure, a hydrogen sulfide neutralizing tool for neutralizing hydrogen sulfide within a subterranean well includes a tubular member with an internal bore. A tool shell circumscribes the tubular member and defines a tool annular space between an outer diameter surface of the tubular member and an inner diameter surface of the tool shell. Sacrificial rods are located within the tool annular space, the sacrificial rod formed of a material that produces metal sulfide when exposed to the hydrogen sulfide. The tubular member includes an uphole perforation. The uphole perforation has an opening extending through a sidewall of the tubular member defining a fluid flow path between the tool annular space and the internal bore of the tubular member. The tubular member includes a downhole perforation. The downhole perforation is located downhole of the uphole perforation and has an opening extending through the sidewall of the tubular member defining a fluid flow path between the tool annular space and the internal bore of the tubular member.
In alternate embodiments, the hydrogen sulfide neutralizing tool can further include a non-return valve. The non-return valve can be operable to allow a fluid flow through the non-return valve in a downhole direction and block the fluid flow through the non-return valve in an uphole direction. A rod structural support can be located within the tool annular space and can extend between the sacrificial rod to at least one of the tubular member and the tool shell. A junk basket can be located within the tool annular space downhole of the sacrificial rod.
In an alternate embodiment of this disclosure, a system for neutralizing hydrogen sulfide within a subterranean well with a hydrogen sulfide neutralizing tool includes a drill stem testing string extending within a wellbore of the subterranean well. The drill stem testing string has a central bore and defines a wellbore annular space between an outer diameter of the drill stem testing string and an inner diameter surface of the wellbore. The drill stem testing string further includes the hydrogen sulfide neutralizing tool secured in-line. The hydrogen sulfide neutralizing tool has a tubular member with an internal bore in fluid communication with the central bore extending through adjacent members of the drill stem testing string. A tool shell circumscribes the tubular member and defines a tool annular space between an outer diameter surface of the tubular member and an inner diameter surface of the tool shell. A sacrificial rod is located within the tool annular space. The sacrificial rod is formed of a material that produces metal sulfide when exposed to the hydrogen sulfide. The tubular member includes an uphole perforation. The uphole perforation has an opening extending through a sidewall of the tubular member defining a fluid flow path between the tool annular space and the internal bore of the tubular member. The tubular member includes a downhole perforation. The downhole perforation is located downhole of the uphole perforation and has an opening extending through the sidewall of the tubular member defining a fluid flow path between the tool annular space and the internal bore of the tubular member.
In alternate embodiments, the system can further include a non-return valve operable to allow a fluid flow through the drill stem testing string past the non-return valve in a downhole direction, and to block the fluid flow through the drill stem testing string past the non-return valve in an uphole direction. A plurality of the sacrificial rods can be spaced around a circumference of the tool annular space. A rod structural support can include a ring shaped member extending between each of the plurality of the sacrificial rods. A junk basket can be located within the tool annular space downhole of the sacrificial rod. The junk basket can be positioned to collect the produced metal sulfide within the drill stem testing string.
In another alternate embodiment of this disclosure, a method for neutralizing a hydrogen sulfide within a subterranean well with a hydrogen sulfide neutralizing tool includes providing the hydrogen sulfide neutralizing tool having a tubular member with an internal bore. A tool shell circumscribes the tubular member and defines a tool annular space between an outer diameter surface of the tubular member and an inner diameter surface of the tool shell. A sacrificial rod is located within the tool annular space, the sacrificial rod formed of a material that produces metal sulfide when exposed to the hydrogen sulfide. The tubular member includes an uphole perforation. The uphole perforation has an opening extending through a sidewall of the tubular member, defining a fluid flow path between the tool annular space and the internal bore of the tubular member. The tubular member includes a downhole perforation. The downhole perforation is located downhole of the uphole perforation and has an opening extending through the sidewall of the tubular member defining a fluid flow path between the tool annular space and the internal bore of the tubular member. The method further includes forming a drill stem testing string having the hydrogen sulfide neutralizing tool secured in-line. The drill stem testing string is extended within a wellbore of the subterranean well. The drill stem testing string has a central bore and defines a wellbore annular space between an outer diameter of the drill stem testing string and an inner diameter surface of the wellbore. Upward flow of fluids is directed through the hydrogen sulfide neutralizing tool to contact the sacrificial rod, consuming the hydrogen sulfide from the flow of fluids by producing the metal sulfide from the sacrificial rod.
In alternate embodiments, the hydrogen sulfide neutralizing tool can further include a non-return valve. The non-return valve can allow a fluid flow through the non-return valve in a downhole direction and can block the fluid flow through the non-return valve in an uphole direction. A flow of fluid traveling in an uphole direction can be directed from the internal bore of the tubular member, through the downhole perforation, and into the tool annular space. The flow of fluid can be further directed past the sacrificial rod, and from the tool annular space, through the uphole perforation, and into the internal bore of the tubular member.
In other alternate embodiments, the sacrificial rod can be supported with a rod structural support. The rod structural support can be located within the tool annular space and extend between the sacrificial rod to at least one of the tubular member and the tool shell. The hydrogen sulfide neutralizing tool can further include a plurality of the sacrificial rods. The plurality of the sacrificial rods can be spaced around a circumference of the tool annular space. The sacrificial rod can be supported with a rod structural support. The rod structural support can include a ring shaped member extending between each of the plurality of the sacrificial rods. The metal sulfide can be collected in a junk basket located within the tool annular space downhole of the sacrificial rod.
So that the manner in which the above-recited features, aspects and advantages of the disclosure, as well as others that will become apparent, are attained and can be understood in detail, a more particular description of the embodiments of the disclosure briefly summarized above may be had by reference to the embodiments thereof that are illustrated in the drawings that form a part of this specification. It is to be noted, however, that the appended drawings illustrate only certain embodiments of the disclosure and are, therefore, not to be considered limiting of the disclosure's scope, for the disclosure may admit to other equally effective embodiments.
The Specification, which includes the Summary of Disclosure, Brief Description of the Drawings and the Detailed Description, and the appended Claims refer to particular features (including process or method steps) of the disclosure. Those of skill in the art understand that the disclosure includes all possible combinations and uses of particular features described in the Specification. Those of skill in the art understand that the disclosure is not limited to or by the description of embodiments given in the Specification. The inventive subject matter is not restricted except only in the spirit of the Specification and appended Claims.
Those of skill in the art also understand that the terminology used for describing particular embodiments does not limit the scope or breadth of the disclosure. In interpreting the Specification and appended Claims, all terms should be interpreted in the broadest possible manner consistent with the context of each term. All technical and scientific terms used in the Specification and appended Claims have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure relates unless defined otherwise.
As used in the Specification and appended Claims, the singular forms “a”, “an”, and “the” include plural references unless the context clearly indicates otherwise. As used, the words “comprise,” “has,” “includes”, and all other grammatical variations are each intended to have an open, non-limiting meaning that does not exclude additional elements, components or steps. Embodiments of the present disclosure may suitably “comprise”, “consist” or “consist essentially of” the limiting features disclosed, and may be practiced in the absence of a limiting feature not disclosed. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.
Spatial terms describe the relative position of an object or a group of objects relative to another object or group of objects. The spatial relationships apply along vertical and horizontal axes. Orientation and relational words including “uphole” and “downhole”; “above” and “below” and other like terms are for descriptive convenience and are not limiting unless otherwise indicated.
Where the Specification or the appended Claims provide a range of values, it is understood that the interval encompasses each intervening value between the upper limit and the lower limit as well as the upper limit and the lower limit. The disclosure encompasses and bounds smaller ranges of the interval subject to any specific exclusion provided.
Where reference is made in the Specification and appended Claims to a method comprising two or more defined steps, the defined steps can be carried out in any order or simultaneously except where the context excludes that possibility.
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During a drill stem test, drill stem testing string 16 can extend into wellbore 12. Drill stem testing string 16 can be a temporary completion of subterranean well 10 that is used to perform the drill stem test and then is removed from wellbore 12. During a drill stem test a selected reservoir can be isolated from the other portions of the wellbore. Drill stem testing string 16 can include a circulating sub, cross over sub, bypass, seal, packer, perforated sub, sensors, gauges, and multiple combinations of each such tools and equipment.
Drill stem testing string 16 has a central bore and defines a wellbore annular space between an outer diameter of drill stem testing string 16 and an inner diameter surface of wellbore 12. During a drill stem test, fluids are circulated in a direction downhole within drill stem testing string 16 and in a direction uphole within wellbore annular space 17. During a drill stem test, the direction of the flow of fluids is alternated one or more times and the fluids are alternately circulated in a direction uphole within drill stem testing string 16 and in a direction downhole within wellbore annular space 17. Characteristics of a particular reservoir, such as productive capacity, pressure, and permeability, can be calculated based on the data gathered during a drill stem test.
Hydrogen sulfide neutralizing tool 18 can be part of drill stem testing string 16, secured in-line with adjacent components of drill stem testing string 16. Hydrogen sulfide neutralizing tool 18 can be used for neutralizing hydrogen sulfide within subterranean well 10.
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Hydrogen sulfide neutralizing tool 18 further includes tool shell 26. Tool shell 26 circumscribes tubular member 20 and defines tool annular space 28 between an outer diameter surface of tubular member 20 and an inner diameter surface of tool shell 26. Tool shell 26 can have a circular cross section (
Tubular member 20 includes uphole perforation 30. Uphole perforation 30 has at least one opening 32 extending through a sidewall of tubular member 20. Uphole perforation 30 defines a fluid flow path between tool annular space 28 and internal bore 22 of tubular member 20. Tubular member 20 further includes downhole perforation 34. Downhole perforation 34 is located downhole of uphole perforation 30. Downhole perforation 34 has at least one opening 36 extending through a sidewall of tubular member 20. Downhole perforation 34 defines a fluid flow path between tool annular space 28 and internal bore 22 of tubular member 20.
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As the hydrogen sulfide comes in contact with sacrificial rod 38, sacrificial rod 38 becomes brittle and corrodes, producing metal sulfide. During such process, hydrogen sulfide is consumed, which reduces the concentration of hydrogen sulfide in the formation fluid that is traveling to the surface. When the hydrogen sulfide reacts with the metal outer surface of sacrificial rod 38, the outer surface will crack and portions of the outer surface will peel and fall from sacrificial rod 38 as debris 40. Debris 40 can include the metal sulfides that are formed as a result of the reaction of the hydrogen sulfide with the metal of sacrificial rod 38. This cracking and peeling process will expose a fresh outer surface of sacrificial rod 38 that can be reacted with hydrogen sulfide, until all of the metal material of sacrificial rod 38 has been consumed and turned into debris 40.
Debris 40 can fall in a downhole direction and be trapped within junk basket 42. Junk basket 42 is located within tool annular space 28 downhole of sacrificial rod 38. Junk basket 42 can be defined between the outer diameter surface of tubular member 20 and the inner diameter surface of tool shell 26 and can be positioned to collect debris 40, which can include the produced metal sulfide, within drill stem testing string 16. Debris 40 can be removed from junk basket 42 when drill stem testing string 16 is returned to the surface after the well flow tests and other drill stem tests have been completed.
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Each of the tubular member 20, tool shell 26 and structural support 44 can be formed of a material that is resistant to hydrogen sulfide. Hydrogen embrittlement does not affect all metallic materials equally. High-strength steels, titanium alloys and aluminum alloys are more vulnerable to hydrogen sulfide than lower-strength steels. As an example, commonly used steel of grades J-55, K-55, L-80 have higher level of hydrogen sulfide resistance compared to higher strength grades, such as P-110 and Q-125
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As the flow of fluids travels in the uphole direction, with non-return valve 50 in the closed position the flow of fluids will be blocked from traveling uphole through internal bore 22 of tubular member 20. The flow of fluids will instead be directed into tool annular space 28 by way of downhole perforation 34. The flow of fluids will travel in an uphole direction though tool annular space 28, contacting sacrificial rod 38. After flowing over sacrificial rod 38, the flow of fluids can exit tool annular space 28 and return to internal bore 22 of tubular member 20 by way of uphole perforation 30.
Contact with sacrificial rod 38 will reduce the amount of hydrogen sulfide within the flow of fluids as the hydrogen sulfide reacts with the material of sacrificial rod 38. The reaction of hydrogen sulfide with the material of sacrificial rod 38 results in the consumption of hydrogen sulfide through the production of metal sulfide. Therefore, the amount of hydrogen sulfide in the flow of fluids exiting tool annular space 28 will be less than the amount of hydrogen sulfide in the flow of fluids entering tool annular space 28. The flow of fluid exiting tool annular space 28 can travel in an uphole direction through central bore 24 of drill stem testing string 16 and be produced to the surface.
In an example of operation, in order to neutralize a hydrogen sulfide within subterranean well 10 during drill stem testing operations, hydrogen sulfide neutralizing tool 18 can be made up in-line as part of drill stem testing string 16. Drill stem testing string 16 can be extended into wellbore 12 of subterranean well 10. Drill stem testing operations can be performed.
During drill stem testing operations, fluids can be pumped into drill stem testing string to travel in a downhole direction from the surface through central bore 24 of drill stem testing string 16. A portion of the fluid flow that is pumped downhole through central bore 24 of drill stem testing string 16 from the surface will remain within internal bore 22 of tubular member 20 and will travel through non-return valve 50. Another portion of the fluid flowing through internal bore 22 of tubular member may enter tool annular space 28 by way of uphole perforation 30. The portion of the fluid that enters tool annular space 28 will return to internal bore 22 of tubular member 20 by way of downhole perforation 34. As an example, during a drill string test, drilling mud or brine can be pumped downhole through drill stem testing string 16 to prepare the well for testing. Such fluid can return to the surface through wellbore annular space 17.
During drill stem testing operations, the direction of the flow of fluids is reversed one or more times. As an example, another step of the drill stem testing operations can include producing reservoir fluids to the surface through central bore 24 of drill stem testing string 16. When fluids are flowing in an uphole direction through central bore 24 of drill stem testing string 16, non-return valve 50 will be in a closed position
As the flow of fluids travels in the uphole direction, with non-return valve 50 in the closed position, the flow of fluids will be directed into tool annular space 28 by way of downhole perforation 34. The flow of fluids will travel in an uphole direction though tool annular space 28, contacting sacrificial rod 38. After flowing over sacrificial rod 38, the flow of fluids can exit tool annular space 28 and return to internal bore 22 of tubular member 20 by way of uphole perforation 30.
The reaction of hydrogen sulfide with the material of sacrificial rod 38 results in the consumption of hydrogen sulfide through the production of metal sulfide so that the amount of hydrogen sulfide in the flow of fluids is reduced. The flow of fluid exiting tool annular space 28 can travel in an uphole direction through central bore 24 of drill stem testing string 16 and be produced to the surface.
When the hydrogen sulfide reacts with the metal outer surfaces of sacrificial rod 38, the outer surface will crack and portions of the outer surface will peel and fall from sacrificial rod 38 as debris 40. Debris 40 can include the metal sulfides that are formed as a result of the reaction of the hydrogen sulfide with the metal of sacrificial rod 38. Debris 40 can fall in a downhole direction and be trapped within junk basket 42. Debris 40 can be removed from junk basket 42 when drill stem testing string 16 is returned to the surface after the well flow tests and other drill stem tests have been completed.
Therefore embodiments of this disclosure provide systems and methods for utilizing the corrosive nature of hydrogen sulfide to reduce the amount of hydrogen sulfide in a flow of fluids in a subterranean well. One or a combination of multiple sets of hydrogen sulfide neutralizing tools can be used in the downhole string where a higher concentration of hydrogen sulfide is expected. The number of hydrogen sulfide neutralizing tools to be used will depend on the expected concentration of hydrogen sulfide, the neutralization efficiency of the downhole system, and the target concentration of hydrogen sulfide being produced at the surface.
Embodiments of this disclosure reduce the amount of hydrogen sulfide in a wellbore fluid before the wellbore fluid reaches the surface. This will improve the safety of personnel and extend the working life of surface equipment compared to producing fluids that contain higher levels of hydrogen sulfide.
Embodiments described herein, therefore, are well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While certain embodiments have been described for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the scope of the present disclosure disclosed herein and the scope of the appended claims.
