Systems and methods for detecting leaks in subsea cement and wellbore equipment
Methods and systems for detecting subsea cement returns, leaks in subsea cement, leaks in blowout preventer operating systems or other equipment or conduits, or the presence of sweep or spacer media subsea or at the surface, include mixing an indicator, such as sodium fluorescein, with a quantity of cement or other medium, the indicator being insulated from contact with the subsea environment. The medium and indicator can be provided into a subsea wellbore, and upon contact of a portion of the medium with the subsea environment, the indicator can become detectable. Exposing the subsea environment proximate to the wellbore to a detector, such as an ultraviolet light source, enables detection of the indicator, and thereby, detection of the medium, which can indicate a cement return or leak of operating fluids in a subsea blowout preventer system.
Embodiments usable within the scope of the present disclosure relate, generally, to methods and systems for detecting leaks and/or substances used in association with a subsea wellbore, and more specifically, to methods and systems for detecting cement returns, sweeps, spacers, leaks in cement and/or equipment, and/or other similar substances or features through detection of indicator chemicals in a subsea environment or at the surface of a subsea well.
BACKGROUNDAfter drilling and casing a subsea well, it is necessary to cement the well to secure the casing string in place. Typically, cementing a well includes pumping quantities of cement into the well to displace the drilling fluid within, interspersed with quantities of a spacing medium, the cement and spacing medium being separated by plugs or similar members. The objective of a cementing operation is to provide a sufficient quantity of cement into a well such that the annulus surrounding the casing is filled with liquid cement, while the interior of the casing is swept substantially free of cement by the plugs and/or spacing medium. The cement is then allowed to cure, securing the casing in place, to allow for subsequent completion and production operations to be performed.
Errors in the cementing process, especially in a subsea environment, can be catastrophic, allowing hydrocarbons and/or wellbore fluids to escape into the environment, and/or causing extensive damage to equipment, as well as the possibility of death or injury to personnel. Often, the presence of a leak in cured cement, or the presence of a liquid cement return on the subsea floor, must be determined visually, such as through use of a remotely operated vehicle equipped with a light source and/or camera. Due to the fact that the subsea environment is entirely dark beyond a certain depth, additionally or alternatively, the presence of sweeping and/or spacing media can be visually verified at the surface of a well. Similarly, leaks in operating equipment, such as operating systems of blowout preventers and/or other portions of a subsea wellbore or conduit, must be detected visually, in the subsea environment, such as through detection of visible fluid and/or moving water.
To facilitate detection of cement, sweeping/spacing media, and/or leaks in cement, equipment, and/or conduits, various dyes can be used to provide color to cement, or other wellbore fluids. However, such dyes often become rapidly diluted and difficult to visualize, especially in a subsea environment, where attempts to visualize the dye are subject to moving water and limited light. Further such dyes also become diluted and/or ineffective after prolonged exposure to and/or movement of wellbore fluid and/or seawater that contacts the dye and/or the medium within which the dye has been added.
A need exists for systems and methods usable to detect cement returns and/or leaks in a subsea environment, and/or a sweeping or spacing medium associated with a subsea well, that enables efficient, reliable detection.
A further need exists for systems and methods usable within a subsea environment to detect cement returns and/or leaks associated with a subsea wellbore, blow out preventer operation systems, and/or other similar wellbore equipment and/or conduits.
A need also exists for systems and methods for detecting cement returns, leaks, and/or wellbore media that remain inactive and/or unexpended until a detectable anomaly and/or event occurs.
Embodiments usable within the scope of the present disclosure meet these needs.
SUMMARYEmbodiments usable within the scope of the present disclosure relate to methods for detecting leaks in subsea cement and/or cement returns in a subsea environment in which an indicator is mixed with a quantity of lead cement, the indicator being in an inactive state and insulated from contact with water, providing the quantity of cement and the indicator into a subsea wellbore. When a portion of the lead cement contacts the subsea environment proximate to the subsea wellbore, the indicator is activated to an active state. The subsea environment proximate to the subsea wellbore can be exposed to a detector adapted to detect the indicator, thereby detecting the lead cement. Cement provided into the wellbore subsequent to the lead cement can thereby be allowed to cure.
For example, one usable indicator can include sodium fluorescein, and/or another similar fluorescein (C20H12O5) salt. In an inactive state, sodium fluorescein is a red powder, generally detectable only through visual observation, which can be readily mixed with liquid cement, an oil-based or synthetic mud-based spacer or sweeping solution, or the like, without becoming activated (e.g., by disassociating into constituent ions). Upon contact with free water, sodium fluorescein becomes activated (e.g., the compound disassociates into sodium and fluorescein ions). The free fluorescein ions will fluoresce a bright green color when exposed to ultraviolet light, enabling a very small quantity of sodium fluorescein to be easily detected once activated.
As such, sodium fluorescein, another fluorescein salt, or a similar indicator compound, chemical, and/or substance can be mixed with a quantity of cement and provided into a subsea wellbore. When the cement cures, the inactive sodium fluorescein remains embedded in the cement, insulated from contact with the subsea environment. However, in the event that the cement develops a crack or leak, exposure to water will activate the sodium fluorescein, enabling the crack or leak to be easily detected. Similarly, if a cement return occurs at the subsea floor, the sodium fluorescein will be exposed to the water in the subsea environment, enabling the cement return to be easily detected.
Specifically, an ultraviolet light source can be transported to the subsea floor. For example, in an embodiment, a remotely operated vehicle can be equipped with an ultraviolet light source, and maneuvered proximate to the subsea wellbore to expose the environment proximate to the wellbore to ultraviolet light. Responsive to the presence of ultraviolet light, the activated/dissolved sodium fluorescein will fluoresce (e.g., a bright green), such that even a trace quantity can be readily visualized in a subsea environment, allowing leaks and/or cement returns, independent of sizes, to be quickly and efficiently detected.
As such, embodiments usable within the scope of the present disclosure also relate to systems for detecting leaks in subsea cement and/or cement returns that include a quantity of cement disposed in association with a subsea wellbore, and an indicator (e.g., sodium fluorescein) within the quantity of cement in an inactive state that is insulated from contact with water. If/when a leak in the cement and/or a cement return in the subsea environment exposes the indicator to water, the indicator is activated (e.g., releasing fluorescein ions), such that a detector adapted for detecting the activated indicator (e.g., an ultraviolet light source) can be used to detect the presence of the indicator, and thereby the leak and/or cement return, as described above.
Other embodiments usable within the scope of the present disclosure can include methods for detecting a non-aqueous substance associated with a subsea wellbore, such as a liquid cement return on the subsea floor, fluid from within a blowout preventer operating system that contacts water due to a leak, a sweep and/or spacer medium (e.g., a water-based mud and/or oil/synthetic-based medium), and/or other similar non-aqueous substances used in association with a subsea wellbore.
Specifically, the non-aqueous substance is mixed with an indicator (e.g., sodium fluorescein) in such a manner that the indicator is insulated from contact with water (e.g., from the subsea environment), such that a leak in any component, conduit, and/or piece of equipment used in association with the subsea wellbore, a cement return, or the presence of the spacer or sweep medium at the surface, will cause the indicator to contact water and become activated. A detector (e.g., an ultraviolet light source) can then be used to detect the indicator, and thereby detect the non-aqueous medium. To detect quantities of the non-aqueous medium in the subsea environment proximate to the wellbore, a remotely operated vehicle can be provided with an ultraviolet light source or similar detector, while to detect quantities of the non-aqueous medium at the surface (e.g., a spacer or sweep medium), a small amount of water can be added to the non-aqueous medium as it appears on the surface to ensure activation of the indicator, then a handheld or similar portable ultraviolet light source or other type of detector can be used to detect the activated indicator.
Embodiments usable within the scope of the present disclosure thereby enable cement returns, sweeping and/or spacing/displacement media, and/or leaks in cement, blowout preventer operating systems, and/or other subsea well equipment or conduits, to be efficiently and reliably detected, in a subsea environment or at the surface, through use of indicators that remain inactive and/or unexpended until a detectable anomaly and/or event occurs.
In the detailed description of various embodiments usable within the scope of the present disclosure, presented below, reference is made to the accompanying drawings, in which:
One or more embodiments are described below with reference to the listed Figures.
DETAILED DESCRIPTION OF THE EMBODIMENTSBefore describing selected embodiments of the present disclosure in detail, it is to be understood that the present invention is not limited to the particular embodiments described herein. The disclosure and description herein is illustrative and explanatory of one or more presently preferred embodiments and variations thereof, and it will be appreciated by those skilled in the art that various changes in the design, organization, means of operation, structures and location, methodology, and use of mechanical equivalents may be made without departing from the spirit of the invention.
As well, it should be understood that the drawings are intended to illustrate and plainly disclose presently preferred embodiments to one of skill in the art, but are not intended to be manufacturing level drawings or renditions of final products and may include simplified conceptual views to facilitate understanding or explanation. As well, the relative size and arrangement of the components may differ from that shown and still operate within the spirit of the invention.
Moreover, it will be understood that various directions such as “upper”, “lower”, “bottom”, “top”, “left”, “right”, and so forth are made only with respect to explanation in conjunction with the drawings, and that components may be oriented differently, for instance, during transportation and manufacturing as well as operation. Because many varying and different embodiments may be made within the scope of the concept(s) herein taught, and because many modifications may be made in the embodiments described herein, it is to be understood that the details herein are to be interpreted as illustrative and non-limiting.
Referring now to
A tubular string (14) (e.g., a landing string) is shown positioned in the wellbore (10). The depicted tubular string (14) includes one or more segments of a tubular conduit (e.g., casing), terminating at a float collar and a guide shoe, and one or more centralizers for positioning and/or stabilizing the string (14) in the wellbore (10). The specific components of a landing string are well known in the art, and it should be understood that embodiments usable within the scope of the present disclosure can be used in connection with any type of tubular string or other wellbore conduit or equipment, as well as in uncased and/or open-hole regions, independent of the type and/or arrangement of tubular elements or equipment within the wellbore.
The tubular string (14) includes an axial bore (16) extending therethrough for communicating cement and/or other fluids/substances. Positioning the tubular string (14) within the wellbore (10) defines an annulus (18) between the exterior of the tubular string (14) and the formation (12). As described above, the typical objective of a cementing operation is to provide liquid cement into the wellbore (10) through the axial bore (16) of the string (14), then displace the cement into the annulus (18), e.g., using one or more plugs and a spacing medium, where the cement is allowed to cure to secure the tubular string (14) in a desired position.
For example,
As the cement slurry (22) is pumped through the tubular string (14), the bottom plug (24) displaces the drilling fluid (20) until the bottom plug (24) is seated in the tubular string (14) (e.g., on a float collar). The cement slurry (22) is then pumped through a bore in the bottom plug (24), where it exits the lower end of the tubular string (14), then travels upward in the annulus (18).
To remove undesired cement from the operative portions of the tubular string (14), the displacement fluid (26) can be pumped into the bore (16), such that the top plug (28) displaces the cement slurry (22) through the bore in the bottom plug (24), out from the upper portions of the tubular string (14). Continued pumping of the displacement fluid (26) further displaces the cement slurry (22) into the annulus (18). Once the cement within the annulus (18) cures, the tubular string (14) is secured, and subsequent operations (e.g., perforating, stimulation, production, etc.) can be performed.
For illustrative purposes,
When a liquid cement return, diagrammatically illustrated by the arrow (32), contacts the subsea floor, the indicator compound (30) is exposed to the subsea environment and becomes activated, such that use of an ultraviolet light source or similar detector can determine the presence of the cement return by detecting the indicator compound. Similarly, leaks in cured cement containing the indicator compound (30), and/or the presence of displacing fluid at the surface that contains the indicator compound, can also be detected through use of a detector.
Referring now to
For illustrative purposes,
While various embodiments usable within the scope of the present disclosure have been described with emphasis, it should be understood that within the scope of the appended claims, the present invention can be practiced other than as specifically described herein.
Claims
1. A method for detecting leaks in subsea cement or cement returns in a subsea environment, the method comprising the steps of:
- mixing an indicator with a quantity of cement, wherein the indicator is in an inactive state and wherein the indicator is insulated from contact with water;
- providing the quantity of cement and the indicator into a subsea wellbore;
- permitting the quantity of cement to contact the subsea environment proximate to the subsea wellbore thereby activating the indicator to an active state; and
- exposing the subsea environment proximate to the subsea wellbore to a detector adapted for detecting the indicator in the active state to detect the indicator and thereby detect the second portion of the cement.
2. The method of claim 1, wherein the indicator comprises sodium fluorescein, another fluorescein salt, or combinations thereof.
3. The method of claim 1, wherein the quantity of cement comprises a cement return and wherein the subsea environment proximate to the subsea wellbore comprises a subsea floor.
4. The method of claim 1, wherein the step of exposing the subsea environment proximate to the subsea wellbore to the detector comprises exposing the subsea environment to an ultraviolet light source.
5. The method of claim 4, wherein the step of exposing the subsea environment to the ultraviolet light source comprises associating the ultraviolet light source with a remotely operated vehicle, maneuvering the remotely operated vehicle to the subsea environment proximate to the subsea wellbore, and exposing the subsea environment proximate to the subsea wellbore to the ultraviolet light source.
6. A system for detecting leaks in subsea cement or cement returns in a subsea environment, the system comprising:
- a quantity of cement disposed in association with a subsea wellbore;
- an indicator within the quantity of the cement, wherein the indicator is in an inactive state, wherein the indicator is insulated from contact with water, and wherein a leak in the quantity of cement, a cement return in the subsea environment, or combinations thereof, exposes the indicator to water, thereby activating the indicator to an active state; and
- a detector adapted for detecting the indicator in the active state, thereby detecting the leak, the cement return, or combinations thereof.
7. The system of claim 6, wherein the indicator comprises sodium fluorescein, another fluorescein salt, or combinations thereof.
8. The system of claim 6, wherein the subsea environment comprises a subsea floor proximate to the subsea wellbore.
9. The system of claim 6, wherein the detector comprises an ultraviolet light source.
10. The system of claim 9, further comprising a remotely operated vehicle having the ultraviolet light source associated therewith.
11. A method for detecting a non-aqueous substance associated with a subsea wellbore, the method comprising the steps of:
- mixing an indicator with a medium and providing the medium into a subsea wellbore, wherein the indicator is insulated from contact with a subsea environment proximate to the subsea wellbore, and wherein the indicator is thereby insulated from detection,
- wherein at least a portion of the medium and the indicator contacts the subsea environment, thereby enabling detection of the indicator; and
- exposing said at least a portion of the medium to a detector adapted for detecting the indicator in the active state to detect the indicator and thereby detect the medium.
12. The method of claim 11, wherein the step of mixing the indicator with the medium comprises mixing the indicator with a non-aqueous medium, wherein the indicator is in an inactive state, wherein the indicator is insulated from contact with water, and wherein contact between said at least a portion of the medium and the subsea environment activates the indicator to an active state.
13. The method of claim 11, wherein the step of mixing the indicator with the medium comprises mixing the indicator with liquid cement, wherein at least a portion of the cement contacts the subsea environment as a cement return on a subsea floor, and wherein the step of exposing said at least a portion of the medium to the detector comprises providing the detector proximate to the subsea floor for detecting the cement return by detecting the indicator.
14. The method of claim 11, wherein the step of mixing the indicator with the medium comprises mixing the indicator with fluid within a blowout preventer operating system of a deepwater rig, wherein a leak in the blowout preventer operating system permits at least a portion of the fluid to contact the subsea environment proximate to the blowout preventer operating system, and wherein the step of exposing said at least a portion of the medium to the detector comprises providing the detector proximate to the subsea floor for detecting the leak by detecting the indicator.
15. The method of claim 11, wherein the step of mixing the indicator with the medium comprises mixing the indicator with a sweep, a spacer, or combinations thereof for use during drilling or completion operations, wherein at least a portion of the sweep, the spacer, or combinations thereof contacts the subsea environment, and wherein the step of exposing said at least a portion of the medium to the detector comprises providing the detector at the surface of the subsea wellbore to detect the sweep, the spacer, or combinations thereof by detecting the indicator.
16. The method of claim 11, wherein the indicator comprises sodium fluorescein, another fluorescein salt, or combinations thereof.
17. The method of claim 13, wherein the step of providing the detector proximate to the subsea floor for detecting the cement return comprises associating an ultraviolet light source with a remotely operated vehicle, maneuvering the remotely operated vehicle to the subsea environment proximate to the subsea floor, and exposing the subsea environment proximate to the subsea floor to the ultraviolet light source.
18. The method of claim 14, wherein the step of providing the detector proximate to the subsea floor for detecting the leak comprises associating an ultraviolet light source with a remotely operated vehicle, maneuvering the remotely operated vehicle to the subsea environment proximate to the subsea wellbore, and exposing the subsea environment proximate to the subsea wellbore to the ultraviolet light source.
19. The method of claim 15, wherein the step of providing the detector at the surface of the subsea wellbore to detect the sweep, the spacer, or combinations thereof, comprises providing a portable ultraviolet source proximate to the surface and exposing the sweep, the spacer, or combinations thereof to the ultraviolet light source.
International Classification: E21B 47/001 (20120101); E21B 47/117 (20120101); E21B 47/113 (20120101); E21B 33/13 (20060101); E21B 47/11 (20120101);