Patent Grant
8485265
The invention relates to materials for downhole applications that are considered to be smart because they can be degraded with minimal intervention and/or in a controlled manner to actuate or activate a variety of responses through the displacement of a solid element or the flow of a fluid. Particularly, the invention relates to the use of such smart materials to remotely control oilfield operations and/or sense (monitor) downhole environmental changes.
In a variety of subterranean and wellbore environments, tools of all sorts are deployed for a multitude of critical applications. The tools, referred as downhole tools, may comprise subsurface safety valves, flow controllers, packers, gas lift valves, sliding sleeves as well as a great many other tools and accessories. Many of these tools have relatively complex mechanical designs in order to be controlled remotely from the surface; e.g. the rig floor via wirelines, hydraulic lines, or coil tubings.
Signal source 14 sends signals into well 16 for controller 12 to detect. Based on the signal received, controller 12 triggers the downhole tool 20 to perform a prescribed action. Signal source 14 may create signals as pressure sequences or in other forms, such as changes in the flow rates, weights, or stress/strain.
In the most common form, signal source 14 creates pressure signals to control the downhole tool 20 via the controller 12. When such hydraulic control is employed, the pressure pulse may be sent via dedicated hydraulic control lines. However, due to the restricted space of the wellbore, the number of control lines that can be run in a well is greatly limited.
Attempts have been made to increase the number of tools that each hydraulic control line can control by using multiplexers, electric/solenoid controlled valves or custom-designed hydraulic devices and tools that respond to sequences of pressure pulses. For example, U.S. Pat. No. 7,182,139 issued to Rayssiguier et al. discloses a method that uses predetermined pressure levels to independently actuate specific well tools such that the number of well tools independently controlled may be greater than the number of fluid control lines.
U.S. Pat. No. 7,171,309 issued to Goodman improves upon the reliability of such approaches by using autocorrelation of command sequences. In accordance with this method, repeat signals of a priori unknown or undefined shape can be correlated to themselves to reliably distinguish intentional changes from random fluctuations or other operations performed on the well.
While these methods are useful in providing sophisticated controls of downhole tools, it is desirable to have controls that do not rely on the limited number of control lines. Furthermore, in many situations, a downhole tool may only need to be actuated once and be left alone. In such situations, the control or actuation mechanism may be more conveniently imbedded in the tool itself.
In one aspect, the present application relates to methods for controlling and/or sensing (monitoring) a downhole operation. A method in accordance with one embodiment includes providing a device downhole, wherein the device comprises at least one smart degradable material; and degrading the smart degradable material to activate the device. The smart degradable materials may be reactive metals and/or alloys of calcium, magnesium, or aluminum, or composites that include these metals and/or alloys in combination with non-metallic materials such as plastics, elastomers, and ceramics. The degradation of the smart degradable material in fluids (which may be referred to as “active fluids”), such as water, results in at least one response, such as a displacement for a solid object (e.g. a spring) or a flow for a fluid, that may itself be used to trigger other responses, for example the opening or closure of a device that may be electric, magnetic, electronic, acoustic, photonic, or a combination thereof. Therefore, a device and part of devices incorporating smart degradable materials may be considered as an “actuator” and, if used to convey any sort of signal for communication and information purposes, they may be used as “sensor and monitoring devices for downhole operations.” The smart degradable material may also be used as restraining element for a variety of downhole tools.
In another aspect, the present invention relates to the use of these smart materials in downhole devices for applications such as penetrating a formation. A downhole device in accordance with embodiments of the invention comprises a degradable material, which may be degraded to irreversibly change the device from state “A” to state “B.” The degradable materials may be partially metallic, as in cases of composites (e.g. metal-matrix composites, or epoxy-metal composites), or fully metallic as in cases of metals (e.g. calcium metal) and alloys (e.g. calcium alloys). The degradation may occur in part of the device or throughout the entire device. Such device may be any downhole devices, which may be as small as a proppant (gravel), or as large as an entire tool (e.g. perforated tubulars or liners). Thus, part of the well completion may be degradable, which may be useful when abandoning well. In this case, the degradable tubulars and liners may be activated to degrade without requiring a recovery operation.
Other aspects and advantages of the invention will be apparent from the following description and the appended claims.
In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood 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.
Embodiments of the invention relate to materials that may be characterized as smart actuation materials, because they can be degraded or converted from one state to another with minimal intervention or in a controlled manner. Furthermore, because some of these materials may also exhibit the typical, high strength of metals and alloys, their conversion from one “strong and solid” state (or phase) to a degraded state (or phase) may be accompanied by a considerable change in force, pressure, stress/pressure containment, allowing the release of strongly energized mechanism or fluid flows. Therefore, such smart degradable materials may be used in downhole tools to control and/or sense (monitor) oilfield operations. The smart degradable materials of the invention may be used to make devices that are intended for a limited term use, i.e. such devices can be degraded after the intended use without the need to retrieve them from the well through time-consuming and costly “fishing” operations. The materials of this invention may be considered “debris-free” and harmless to the well environment.
The “degradation” as used herein refers to any process that converts a smart material from a first state to a second state that is degraded. The “degradation” may be in the form of dissolution, disintegration or defragmentation, even occasionally swelling, and though not encountered, hypothetically shrinkage. Swelling refers to a volumetric expansion that is caused by a reaction between the smart material and the active fluid when the reaction product is a new material of greater volume that normally adheres to the surface of the smart material. Shrinkage would describe the opposite situation, wherein the interaction between the smart material and the active fluid is a new material of smaller volume (shrinkage is not to be confused with dissolution or mass loss in the fluid). Regardless of the form of degradation (e.g. weight losses, geometric changes), the result is a displacement, in one or several directions, that may be used to activate a variety of responses, including the release of an energized element and/or the release of a pressure thus causing a flow. These responses may be used to control and/or sense (monitor) oilfield operations. In accordance with some embodiments of this invention, the mechanical response produced by degrading the smart degradable material may itself be used to actuate other responses, for example the opening or closure of a device that may be electric, magnetic, electronic, acoustic, photonic, or a combination thereof. The fact that the degradable materials may be at least partially metallic, if not entirely metallic and therefore of relatively high strengths, opens a whole new range of possibilities for downhole oilfield operations without the need for more wireline or hydraulic controls.
Smart as used herein refers to materials that can alter their properties, including mechanical and/or rheological properties (such as shape, stiffness, and viscosity), or thermal, optical, or electromagnetic properties, in a predictable or controllable manner in response to changes in their environment (e.g. temperature, pressure/stress and composition). Common smart materials that perform sensing and actuating functions include piezoelectries, electrostrictors, magnetostrictors, and shape-memory alloys. Shape-memory alloys may be thermoresponsive alloys (i.e. alloys that can hold different shapes at various temperatures), magnetic shape memory alloys (i.e. alloys that change their shape in response to a significant variation in the magnetic field), or, less-commonly found, pH-sensitive materials, such as polymers (i.e. materials that swell/collapse when the pH of the surrounding media changes). Other smart materials are halochromic as they change their color as a result of changing acidity (pH). Others are chromogenic and hence change color in response to electrical, optical or thermal changes. Though many smart materials are reversible, smart materials do not necessarily have to be reversible, i.e., changing state (or phase) from an initial state (or phase) to the next and returning to their initial state (or phase). The materials of this invention are smart and change state (or phase) from a solid, characterized by high strengths like in metals and alloys, to a degraded state (or phase), and this change in state (or phase) may be reversible.
In accordance with embodiments of the invention, such smart (degradable) materials may be metals, alloys, or composites of metals and alloys that may include non-metallic materials, such as polymer, plastics, other organic materials (e.g. pasty fluids), or ceramics. In accordance with some embodiments of the invention, the smart materials, comprising degradable metals or alloys, may possess the strength and pressure containing capabilities needed in oilfield operations, such as when strongly energized mechanisms or significant downhole fluid pressures are needed. Due to superior mechanical properties and strength, the smart metal or alloy materials of the invention may be able to provide very rapid responses, which are not possible with typical plastics and elastomers, particularly at downhole temperatures from 200 to 450° F.
The smart materials in accordance with embodiments of the invention are selected for their ability to degrade under predetermined conditions and may be made of, for example, relatively safe and reactive metals such as calcium, magnesium, and their alloys, as well as some less reactive metals like aluminum that may be made more reactive due to alloying, processing, nanoscale structures or inoculation. The materials, when they are composites, may be partially metallic, plastic, polymeric, or others, but preferably comprise at least one degradable material that is metallic by nature. The smart materials useful to the invention are not limited to these examples, and may incorporate other materials that may have adequate mechanical strength and pressure burst or collapse resistance for the designated oilfield applications, while they can be activated or degraded in a controlled manner.
In addition, the smart materials in accordance with some embodiments of the invention may be covered with “permeable” coatings to retard the degradation, resulting in slow or delayed activation of the degradable material. Such “permeable” materials, which may be employed to retard the degradation of the smart materials, could be non-metallic; e.g. a porous or foamed rubber or plastic.
In accordance with some embodiments of the invention, a totally impermeable layer may be used to coated and protect the smart materials. Such protective coating is removed when degradation of the smart materials is desired. For example, in perforating and similar applications, the presence of perforating jets may be used to activate the degradation by damaging such protective coatings. Once the protective coating is impaired, full degradation of the smart materials may ensue, for example, by contacting with the fluids (activation fluid) in the environments. In this example, it should be noted that the perforating operation would take place whether the material is degradable or not. However, the use of degradable materials avoids the formation of fragments or other debris that might require removal by a supplementary intervention. With smart degradable materials, the removal or “fishing” of debris becomes unnecessary. In this respect, a smart degradable material may provide an additional guarantee of undisturbed well operation. In this example, the new material does not detrimentally impact the well operation; on the contrary, it reacts “smartly” to offer a new advantage.
In accordance with embodiments of the invention, the smart materials may be used alone or in combinations. Examples of combinational use of these materials may include a composite, in which a reactive metal, alloy or a reinforced metal or alloy is used with a temporary coating to create one or multiple layers, as illustrated in
In accordance with embodiments of the invention, the smart materials may not only be used to actuate once but to provide multiple actuations, and for instance enable a gradual change in response. For instance, the composite components of the degradable device illustrated in
In accordance with embodiments of the invention, smart materials may be induced (activated) to degrade (i.e., dissolve, disintegrate, or both) by various mechanisms, including contact with an activation or active fluid (i.e. by nature corrosive to the material) and/or due to a change in temperature and/or pressure. The change in temperature and pressure may be provided by a source of thermal energy (i.e. the trigger of a temperature change) or mechanical energy (the results of an explosion or brief pressure spike for instance, as found in jet perforating).
It should be noted that the word “activate” or “activation” is used herein with reference to what is known as “activation energy” in chemical thermodynamics. A chemical reaction or phase transformation may occur over a range of conditions. Using temperature activation as an example, only when a threshold temperature is exceeded would the reaction or transformation proceed at a substantial rate or to a substantial extent, and therefore become noticeable and useful.
For examples, certain materials (e.g. calcium) of the invention degrade at extremely slow rates in neutral (pH=7) water at ambient temperature, i.e. their rates of degradation are nearly zero. As the temperature is raised (e.g., in a downhole wellbore, the temperature may be allowed to increase by equilibrating with its surrounding, as found in the absence of a cold pumped fluid from the surface), the same materials may dissolve with a rate several orders of magnitude greater than at ambient (surface) temperature. In this case, the reaction or transformation exists at both low and high temperatures. However, the reaction or transformation only becomes valuable (or usable) at a relatively high temperature (e.g., downhole temperature) where the reaction or transformation rate is significant. The materials undergoing a fast transformation (i.e. degradation) is then said to be activated. Such materials may be referred to as smart materials because they react in response to changes in its surrounding environment and with minimal intervention or no additional intervention.
As noted above, the degradation of smart materials may be activated by contacts with selected active fluids, temperatures, and/or pressures. The active fluids that can be used to degrade the smart degradable materials may be solvent to the particular materials such that these materials will dissolve in the fluids. The “active fluids” may be liquid, gas, or both. The liquid-type active fluids will typically contain water, but is not so limited and may contain other liquids such as acids. The gas-type active fluids may contain any suitable gases, including as non-Limiting examples water vapor and acid vapors. Furthermore, some active fluids may be multi-phase fluids, which, for example, may have water as one constituent. Some water-based active fluids may also be comprised of an acid or a brine (e.g. some chlorides) dissolved in water, and may contain dissolved gases, such as carbon dioxide (CO2) or hydrogen sulfide (H2S), that contribute to enhancing acidity of the active fluid and, therefore, raise degradation rates.
In addition to active fluids, degradation of the smart materials may also be triggered by the temperature or pressure, which may be transient (e.g., short) or sustained (e.g., prolonged). An example of a transient pressure is the pressure momentarily caused by a perforating jet of an explosion, a high-velocity abrasive fluid jet, or the impact of one object onto another.
As noted above, in accordance with some embodiments of the invention, the smart materials include metals or alloys. Typical examples of smart metals and alloys in accordance with embodiments of the invention include relatively safe alkaline & alkaline-earth metals such as calcium (Ca safely dissolves in water regardless of pH), magnesium (Mg dissolves at low pH), aluminum (Al dissolves at low pH), and alloys and composites of those metals that degrade in water at rates that depend upon temperature, pressure, and fluid composition. For example, acids may accelerate the degradation of these metals or alloys.
The following Table lists some examples of metal and alloy smart materials in accordance with embodiments of the invention. The Table lists metal and alloy compositions, degradation rates at normal pressure (1 atm) in water of specific pH and temperature, as well as their approximate ambient-temperature strength. As shown in this Table, an alloy of calcium containing 20 percent by weight magnesium degrades much slower than pure calcium metal (i.e., 99.99% Ca) and is also about 10 times stronger (i.e., its strength is comparable that of quenched and tempered steels). In addition, note that aluminum can be made degradable in neutral water with suitable alloying elements.
A convenient method to activate (degrade) these smart materials is to make use of the temperature change that, are typically encountered in a wellbore. As shown in the Table above, the slow, and perhaps unnoticeable, degradation rates may be enhanced by increasing temperatures. This is exemplified by the calcium alloy, the degradation rate of which is increased over 20 times by raising the temperatures from 25 to 90° C. Thus, the same reaction at a temperature of 200° C. or higher (which is likely encountered in a deep wells) may become sufficiently fast to degrade these materials (and components made at least partially of those materials) within predictable durations.
In accordance with embodiments of the invention, these smart materials may be used to make smart devices for various controls, such as downhole tool controls. These devices are designed to change from state A to state B upon degradation of the smart materials from one state or phase to the following degraded state or phase. An example of changing a device from state A to state B may be found in a valve that is turned “on” from an “off” state.
The use of smart materials to make smart devices would allow an operator to control the devices with limited or no external direct intervention and without control lines. All the operator needs to do is to initiate the smart material degradation process, for example, by increasing pressure (e.g., by increasing a set-down weight), and/or by addition of a degradation reagent (e.g., an acid or a brine that would accelerate the rates of degradation). Upon degradation of the smart materials, a change in the force, displacement, or the like (pressure and stress, or strain) would occur within the smart device. This in turn will result in the actuation of the device.
The smart materials in accordance with embodiments of the invention may be used in various oilfield applications. The following describe several examples pertinent to downhole oil and gas recovery operations. However, one of ordinary skill in the art would appreciate that these examples are for illustration only and various variations and modifications are possible without departing from the scope of the invention.
For example, embodiments of the present invention may be used in the control of flow and displacement in downhole environments. The smart materials may be used in actuators, for example, to activate other mechanisms, which may be as simple as compression springs (as used in, for example, energized packer elements or production packer slips, anchoring release devices, etc) or more complex systems (such as a variety of electronic gauges and sensors). In accordance with some embodiments of the invention, the material may itself be used as a sensor. The disappearance or compromise of integrity (e.g., due to degradation) of the smart materials could indicate the presence of a particular condition, for example, water (liquid and/or vapor) in situations where water (liquid and/or vapor) would not be expected in the well environment or in situations where the production of water would indicate the oil reservoir has been depleted, and it may be time to abandon the well.
In accordance with some embodiments of the invention, smart materials may be used in sensors, which may be used to detect the presence of a corrosive fluid (water liquid, water vapor, etc). For example,
In accordance with some embodiments of the invention, the smart materials may be used with hollow components (such as liners or casing), in which the smart materials are used as degradable plugs/caps/sealing elements.
In accordance with some embodiments of the invention, the smart materials may be used in disposable and degradable tools, such as shaped charges and perforating guns, including tools used in tubing-conveyed applications. These devices will eventually degrade in the well or formation, saving the need to retrieve these devices after use. These devices may be considered zero-debris devices and may include perforating shaped charge casings, guns, and related devices. Such degradable devices would simplify oilfield operations by eliminating the need for recovery or fishing operations.
In accordance with some embodiments of the invention, the smart materials may be selected to be crush resistant for use in a fracturing fluid. These types of materials, for example, may include metals or alloy (e.g., calcium alloy, aluminum alloy), and composites of those. Such materials may be used as additives or proppants in a hydraulic fracturing fluid. Such materials may be in the shape of flakes, shots, granules and the like. Such materials can be placed in the formation fractures to momentarily increase flows. When production from that particular zone is no longer needed, these materials may be degraded to close the fractures, for instance by pumping an active fluid (e.g. an acid), and/or stopping pumping a cold fluid, and/or enabling the naturally hot reservoir temperature to return to equilibrium.
As noted above, degradation of the smart materials may be by contacting selected fluids, temperatures, and/or pressures. In addition, the pH of the fluids may also be changed to degrade the smart materials in cases such material degradation rate is affected by pH, which had been seen in laboratory experiments with aluminum and magnesium alloys. With temperature and/or pressure, the materials may be so selected that the changes in temperatures and/or pressure (i.e., in typical downhole applications) would raise their degradation rates.
The degradable materials are best suited for one-time use; however, they are not so limited. In accordance with some embodiments of the invention, certain degradable materials may function as smart actuators on a repeatable (multiple use) basis. For such multiple uses, more complex materials such as laminated or layered composites may be designed. In a laminated or layered composite, the number of layer may indicate the number of times the component can be used. Such composites may be designed to release elastic energy, or residual stresses as part of the composite degrades.
In the simple mechanism of
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. Accordingly, the scope of the invention should be limited only by the attached claims.
This application claims, under 35 U.S.C. §119(e), the benefits of U.S. Provisional Patent Application No. 60/870,859 filed on Dec. 20, 2006. This Provisional Application is incorporated by reference in its entirety. This application is related to a co-pending application Ser. No. 11/769,230, entitled “Temporary Containments For Swellable Packer Elements,” by Marya et al., filed on the same date as the present application.
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