1. Field of the Invention
The present invention relates generally to the downhole well operations, and more particularly to downhole chemical injection for intelligent completions.
2. Background Art
Hydrocarbon fluids such as oil and gas are produced from subterranean formations by drilling a well to penetrate the hydrocarbon-bearing formation. After drilling, the wells are typically completed with various devices downhole to facilitate the production of the hydrocarbons. In an intelligent completion system, various sensors, pumps, and flow control valves are included. In addition, an intelligent completion system may include fully automated measurement and control systems that optimizes reservoir economics without human intervention.
When a broad pay zone or multiple pay zones is completed, the intelligent completion system may include multiple production zones.
When formation fluids from formations come into contact with a pipe, valve or other production equipment in a wellbore, or when there is a decrease in temperature, pressure, or change of other conditions, waxes and/or asphaltines in the formation fluids may precipitate or separate out. Over time, deposits such as scale, wax, or asphaltine, etc., may build-up on surfaces of downhole components and impede their function and/or efficiency. To address the issue of deposit build-up, chemicals may be injected into production tubing to remove, reduce or inhibit the deposit material inside the tubing or on downhole devices. For example, a control line may be run from the surface to an injection point located in the completion to convey the injected chemical downhole into a production stream. One common practice is to have one or more injection points provided upstream a production packer.
In intelligent completion well systems, multiple flow control valves are run to control the production from multiple zones. However, these various valves may not function in the event of scale build up around moving surfaces. Running control lines from the surface to remedy these situations may not be practical when multiple zones are included in a completion. Therefore, chemical injection systems suitable for preventing and/or reducing deposit build-up in intelligent completion are needed.
One aspect of the invention relates to intelligent completion systems. An intelligent completion system in accordance with one embodiment of the invention includes a production tubing configured for production from multiple zones in a wellbore; at least one flow control valve disposed on the production tubing for each of the multiple zones, wherein the at least one flow control valve regulates flow of a wellbore fluid into the production tubing; a chemical injection mandrel disposed on the production tubing adjacent the at least one flow control valve in the each of the multiple zones, wherein the chemical injection mandrel is connected to at least one chemical injection line for injecting one or more chemicals into the wellbore; and a control mechanism connected to the at least one flow control valve and the chemical injection mandrel such that the injection mandrel and the at least one flow control valve are operated in a coordinated manner.
Another aspect of the invention relates to methods for removing or reducing a deposit or buildup on a downhole device in an intelligent completion having multiple production zones. A method in accordance with one embodiment of the invention includes: opening a flow control valve disposed on a production tubing, wherein the opening simultaneously activates a chemical injection mandrel disposed the production tubing adjacent the flow control valve in the same zone; injecting at least one chemical using the chemical injection mandrel; and allowing the at least one chemical to flow pass the flow control valve.
Other aspects and advantages of the invention will be apparent from the following description and the appended claims.
Embodiments of the invention relate to systems and methods for removing or preventing buildups on downhole devices in intelligent completion systems in multi-zone wellbores. Embodiments of the invention may be used for multi-point chemical injections in multi-zone intelligent completions on land or offshore. One of ordinary skill in the art would appreciate that embodiments of the invention may also be used with other types of completions with proper modifications and variations.
Some embodiments of the invention relate to multi-point chemical injection systems for use with multi-zone intelligent completions. These chemical injection systems may be used to prevent deposits or buildups of wax, scale, etc. Such buildups may interfere with the proper operations or efficiencies of various downhole devices, such as pumps or flow control valves. By injecting chemicals into the production streams upstream of such devices (e.g., flow control valves), these chemical additives will be carried by the production streams to flow through (or flow by) the particular devices, thereby dissolving the undesirable buildups or preventing the formation of such buildups.
The type of chemicals used with embodiments of the invention may vary with the conditions to be remedied or prevented (paraffins, scales, etc.). For example, for asphaltene buildups, the injected chemical may be aromatic compounds, such as toluene, kerosene, or naphtha. For paraffin buildups, the injected chemical may be xylene or toluene. For hydrate buildups, the injected chemical may be surfactants (e.g., polyvinylcaprolactum) or methanol. For scale buildups, the injected chemical may be EDTA (ethylene tetraacetic acid) or HCl (hydrochloric acid). The above-described are examples used for illustration only and are not meant to be exhaustive.
In accordance with embodiments of the present invention, chemical injection systems may be configured to be operated with existing controls that are already present in an intelligent completion. Such controls may be hydraulic controls or electrical controls. For example, hydraulic control (open and close) lines are typically included in intelligent completions to control flow control valves in various zones. By sharing the existing control mechanisms in intelligent completions, embodiments of the invention may be easily incorporated into any intelligent completion systems. Furthermore, using such systems, chemical injections may be synchronized with the operation of the flow control valves—i.e., chemical injection will be shut off when the flow control valves in a given zone are closed, and chemical injection will be performed only when the flow control valves are opened.
In the following description, numerous details are set forth to provide an understanding of the present invention. However, it would be appreciated by those skilled in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible without departing from the scope of the invention.
In a typical intelligent completion, one or more flow control valves may be included in each production zone. For example, as shown in
These flow control valves are typically controlled by hydraulic control lines, though some are controlled by electrical means. For example, as shown in
In accordance with embodiments of the invention, multi-point chemical injection systems may be designed to take advantage of these existing flow control mechanisms in an intelligent completion, thereby minimizing the engineering challenge and costs. In some intelligent completion, the flow control valves may be regulated by electrical means. In that situation, embodiments of the invention can also take advantage of the existing electrical controls to minimize the engineering challenge and costs. For clarity, the following description will use hydraulic controls to illustrate embodiments of the invention. However, one skilled in the art would appreciate that embodiments of the invention may also be used with electrical controls.
As shown in
In accordance with embodiments of the invention, if more than one chemical injection line is connected to an injection mandrel, these multiple chemical injection lines may be separately injected by the injection mandrel or they may be comingled in the injection mandrel before these chemicals are injected into a wellbore. A proper metering device may be attached to each chemical injection line and/or an outlet of the chemical injection mandrel. In addition, one or more check valves may be used with each chemical injection line to prevent backflow of fluids. For example, each chemical injection lines 29 and 29a is provided with double check valves 21a in the example shown in
In accordance with some embodiment of the invention, chemical injections are preferably performed in a manner coordinated with the operation of the flow control valves in the in the respective zones, e.g., chemical injection is only performed in the zone where the flow control valve is open. This coordinated manner of operation can avoid wasting chemicals into the wellbore when the flow control valve in that zone is not open.
This configuration allows for regulation of the injection mandrels 27 and 27a to be in sync with regulation of the adjacent flow control valves 23 and 23a, respectively. That is, the injection mandrel 27 operates only when the flow control valve 23 is open, and the injection mandrel 27a operates only when the flow control valve 23a is open. The term “in sync” or “synchronization” refers to the state of coordinated operation of the flow control valves and chemical injections in a particular zone; it does not require the opening or closing of the valves to occur at exactly the same time. Due to different configurations of various valves and the nature of hydraulic operations, a small lag time may occur for one valve or injection mandrel relative to the other.
As noted above, one or more chemical injection lines may be connected to one injection mandrel. In addition, if more than one chemical injection line is attached to a mandrel, these chemical injection lines may be separated injected by the mandrel. Alternatively, these chemical injection lines may be comingled in the mandrel before they are injected into a wellbore. The following description will use some examples to illustrate embodiments of the invention. One of ordinary skill in the art would appreciate that these examples are for illustration only and are not intended to limit the scope of the invention.
The first example illustrates a chemical injection system according to one embodiment of the invention, wherein two or more chemical injection lines (e.g., chemical A and chemical B) are comingled prior to being injected into a wellbore by an injection mandrel.
The chemical injection system shown in
The chemicals from the two chemical injection lines may be mixed inside a chamber in each of the injection mandrels. The injection mandrels include outlets for injecting these chemicals into wellbores. The inlets (from the chemical injection lines) and/or outlets on the injection mandrel may include metering valves. Specific operation states of this chemical injection system are illustrated as follows.
The “resting” state may be achieved when all hydraulic control lines are not pressurized, i.e., all hydraulic control lines are bled off. Therefore, the pressure differential between the “open” and “close” lines connecting to each flow control valve or injection mandrel is negligible (or zero) and, therefore, all valves are closed.
This state may be accomplished by applying pressure on both the open control line 304 and the second close control line 302, while allowing the first close line 300 to remain bled off (i.e., low or no pressure). Under these conditions, the pressure differential between the control lines 304 and 302 is small or non-existent, while the pressure differential between control lines 304 ad 300 is substantial (or over a threshold). Therefore, only devices (FCV1 and second injection mandrel 35) connected to control line 300 are operational.
This state may be accomplished by applying pressure on both the open control line 304 and the first close control line 300, while allowing the second close line 302 to remain bled off (i.e., low or no pressure). Under these conditions, the pressure differential between the control lines 304 and 300 is small or non-existent, while the pressure differential between control lines 304 ad 302 is substantial. Therefore, only devices (FCV2 and second injection mandrel 35a) connected to control line 302 are operational.
This state may be accomplished by applying pressure on the open control line 304, while keeping the first and the second close control lines 300, 302 in the bled-off state.
The above example uses a chemical injection system that comingles different chemicals in the injection mandrel. In accordance with some embodiments of the invention, injection mandrels can also be designed to allow for independent injection of different chemicals without comingling.
For example,
As noted above, each of the chemical injection lines 31,33 may contain one or more check valves. In addition, each of the chemical injection lines 31,33 may be independently connected to separate chambers 70,72 in the first injection mandrels 35 and to separate chambers 70a,72a in the second injection mandrel 35a, respectively. Thus, chemicals from the chemical injection lines 31,33 may be kept separate inside the injection mandrels, which may then inject these chemicals via independent outlets into wellbores.
In addition, hydraulic controls lines 300, 302, and 304 are connected to the two flow control valves (FCV1, FCV2) and two mandrels 35,35a, as in the embodiment shown in
This state may be accomplished by applying pressure to the open control line 304 and the second hydraulic close line 302, while allowing the first hydraulic close line 300 to remain bled off.
This state may be accomplished by applying pressure to the open control line 304 and the first hydraulic close line 300, while allowing the second hydraulic close line 302 to remain bled off.
This state may be accomplished by applying pressure to the open control line 304, while allowing the first and the second hydraulic close lines 300, 302 to remain bled off.
Injection mandrels for use with embodiments of the invention may be any suitable injection mandrel known in the art, such as those using piston control valves. For example,
The injection mandrels may be configured to inject chemicals in any desired configurations. For example, an injection mandrel may output the fluids into a conduit that is disposed around the circumference of the tool body and a number of orifices may be provided on this conduit, as illustrated in
Any suitable metering valves may be used with embodiments of the invention. For example,
While embodiments illustrated above are capable of distributing the injected chemicals around the wellbore in a relative even fashion, sometimes thorough mixing of the injected chemicals with the wellbore fluids is desired. In this case, embodiments of the invention, as illustrated above, may be further equipped with one or more flow mixing devices.
For example,
Some embodiments of the invention relate to methods for reducing or removing deposits or buildups on downhole tools or devices.
Advantages of embodiments of the invention may include one or more of the following. Systems and methods of the invention may be used to prevent deposits and chemicals build-up in intelligent completion wells, where multiple flow control valves are run to control the production from multiple zones. The chemical injection systems may be designed to use the existing control mechanism, thereby reducing the engineering challenges and costs. In accordance with some embodiments of the invention, chemical injections are performed only when the flow control valves in the same zones are open. This helps to prevent waste of chemicals when they are not needed. Thus, embodiments of the invention may provide cost- and time-saving ways to ensure clean and functional valves used in intelligent completion well systems.
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. For example, the hydraulic control described above may be replaced with an electrical control mechanism. In that case, the hydraulic lines illustrate in the drawings may be replaced with electrical control lines (wires). Accordingly, the scope of the invention should be limited only by the attached claims.
This claims the priority of provisional application Ser. No. 61/248,903, filed on Oct. 6, 2009. The disclosure of this provisional application is incorporated by reference in its entirety.
Number | Date | Country | |
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61248903 | Oct 2009 | US |