English:
[0003] This section is intended to introduce the reader to various aspects of art, which may be associated with exemplary embodiments of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with information to facilitate a better understanding of particular techniques of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not necessarily as admissions of prior art.
[0008] However, the use of compressible objects in the variable density drilling mud can be challenging. For instance, the compressible objects have to be fabricated to provide a certain amount of compression and to be resilient. Further, the compressible objects have to be designed to compress at certain pressures to provide the volume changes in specific intervals within the wellbore. In addition, the drilling fluid, which is combined with the compressible objects, may be selected and include certain additives to interact with the compressible objects to enhance the variable density drilling mud. As such, there is a need for a method for selecting and fabricating compressible objects for use with drilling fluids to form the variable density drilling mud.
[0012] In a second alternative embodiment, a method associated with drilling a well is described. The method includes selecting compressible objects, wherein each of at least a portion of the compressible objects has an internal pressure (i) greater than 200 pounds per square inch at atmospheric pressure and (ii) selected for a predetermined external pressure, wherein external pressures that exceed the internal pressure reduce the volume of the compressible object; selecting a drilling fluid; introducing the compressible objects to the drilling fluid to form a variable density drilling mud, wherein the variable density drilling mud provides a density between a pore pressure gradient and a fracture pressure gradient for at least one interval of a well as the variable density drilling mud circulates toward the surface of the well; and drilling a wellbore with the variable density drilling mud at the location of the well. Further, once the wellbore is formed, hydrocarbons may be produced from the wellbore.
[0015] The foregoing and other advantages of the present technique may become apparent upon reading the following detailed description and upon reference to the drawings in which:
[0017] FIGs. 2A-2D are an exemplary chart and embodiments of a compressible object in accordance with aspects of the present techniques;
[0018] FIGs. 3A-3C are exemplary embodiments of a compressible object in different states in accordance with aspects of the present techniques;
[0023] FIGs. 8A-8B are exemplary embodiments of fabrication processes utilized in the flow chart of FIG. 6 in accordance with certain aspects of the present techniques;
[0024] FIG. 9 is an exemplary flow chart for a fabrication process utilized in the flow chart of FIG. 6 with compressible objects having a foam template in accordance with certain aspects of the present techniques;
[0025] FIG. 10 are exemplary embodiments of compressible objects fabricated from the flow chart in FIG. 9 in accordance with certain aspects of the present techniques;
[0026] FIGs. 11A-11B are exemplary embodiments of fabrication processes utilized in the flow chart of FIG. 6 in accordance with certain aspects of the present techniques;
[0027] FIGs. 12A-12C are embodiments of a compressible object having a flange in accordance with aspects of the present techniques; and
[0029] In the following detailed description and example, the invention will be described in connection with its preferred embodiments. However, to the extent that the following description is specific to a particular embodiment or a particular use of the invention, this is intended to be illustrative only. Accordingly, the invention is not limited to the specific embodiments described below, but rather, the invention includes all alternatives, modifications, and equivalents falling within the true scope of the appended claims.
[0031] Turning now to the drawings, and referring initially to FIG. 1 , an exemplary drilling system 100 in accordance with certain aspects of the present techniques is illustrated. In the exemplary drilling system 100, a drilling rig 102 is utilized to drill a well 104. The well 104 may penetrate the surface 106 of the Earth to reach the subsurface formation 108. As may be appreciated, the subsurface formation 108 may include various layers of rock that may or may not include hydrocarbons, such as oil and gas, and may be referred to as zones or intervals. As such, the well 104 may provide fluid flow paths between the subsurface formation 108 and production facilities (not shown) located at the surface 106. The production facilities may process the hydrocarbons and transport the hydrocarbons to consumers. However, it should be noted that the drilling system 100 is illustrated for exemplary purposes and the present techniques may be useful in circulating fluids in a wellbore for any purpose, such as performing drilling operations or producing fluids from a subsurface location.
[0032] To access the subsurface formation 108, the drilling rig 102 may include drilling components, such as a bottom hole assembly (BHA) 110, drilling strings 112, casing strings 114 and 115, drilling fluid processing unit 116 for processing the variable density drilling mud 118 and other systems to manage wellbore drilling and production operations. Each of these drilling components is utilized to form the wetlbore of the well 104. The BHA 110 may include a drill bit and be used to excavate formation, cement or other materials from the wellbore. The casing strings 114 and 115 may provide support and stability for the access to the subsurface formation 108, which may include a surface casing string 115 and an intermediate or production casing string 114. The production casing string 114 may extend down to a depth near or through the subsurface formation 108. The drilling fluid processing unit 116 may include equipment that may be utilized to manage the variable density drilling fluid. For example, the drilling fluid processing unit 116 may include shakers, separators, hydrocyclones and other suitable devices (e.g., as described in International Patent Application No. PCT/US2007/003691 , filed 13 February 2007.
[0034] While adding compressible objects to drilling mud to control the density of the drilling mud based on depth has been described in Patent Application Publication No. WO 2006/007347 to Polizzotti et al., the design of compressible objects and selection of a drilling fluid to provide this functionality is difficult. In particular, the repeated compression cycles typically experienced by a recirculating variable density drilling mud within the constraints imposed by the mechanical properties of existing materials may be a limitation for the compressible objects. As such, the process of fabricating the compressible objects may have to include various factors that influence the durability and performance of the compressible objects, as discussed further below.
[0035] To begin, it should be noted that large compression ratios are required to achieve the desired change in the drilling fluid density with depth within the limits set by the maximum volume fraction of the compressible objects allowed by the effect of the compressible objects on the fluid rheology, as described in Patent Application No. WO 2006/007347. Accordingly, the compressible objects should have certain properties configured to provide large compression ratios and to begin compression within certain pressure ranges or levels. The compression ratio of a hollow object, which is one embodiment of the compressible objects, may be limited by the ratio of the initial uncompressed volume (i.e. uncompressed or expanded state) divided by the volume occupied by the material comprising the shell wall plus the volume of the compressed gas inside the shell for the delta pressure ΔP of the wellbore interval of interest. Large compression ratios are provided by the wall of the compressible objects being thin and flexible. Accordingly, the compressible objects may preferably be designed such that the compression and re-expansion of the compressible objects may be accomplished without significant permanent deformation of the walls (i.e., permanent deformation leading to early fatigue failure of the walls of the compressible object).
[0037] To compress at a specific depth, the walls of the compressible objects may be designed to maintain a predetermined internal pressure. The initial internal pressure of the compressible objects for a given drilling mud density is determined by the depth at which a transition to gas compression is dominated by volume change of the compressible objects. Typically, an internal pressure greater than about 200 psi (pounds per square inch) at atmospheric pressure, greater than 500 psi at atmospheric pressure, greater than 1500 psi at atmospheric pressure or more preferably greater than 2000 psi at atmospheric pressure, may be utilized. For a given initial internal pressure, the achievable object compression ratio is dependent on the ratio of the wall thickness to the effective diameter of the compressible object. While the wall thickness is preferably as thin as possible, the lower limit of the wall thickness is defined by the minimum thickness capable of containing the desired internal gas pressure at an external pressure of about 1 atmosphere, which is typically encountered at the surface 106. Accordingly, a material with a tensile strength greater than 10,000 psi may typically be utilized, as discussed below, to maintain the internal pressure for the compressible object. As such, the internal pressure may be in a range from 200 psi up to the tensile strength of the shell material at atmospheric pressure, in a range from 2000 psi to the tensile strength of the shell material at atmospheric pressure, and/or in a range from 1500 psi to 3500 psi at atmospheric pressure.
[0038] Further, for a given internal pressure and diameter of a compressible object, the minimum wall thickness that may be used is therefore defined by the elastic limit of the tensile strength of the wall material. Within these strength limitations, it is desirable to minimize the wall thickness because the ratio of the volume of the wall material to the total volume of the compressible object sets an upper limit on the magnitude of the achievable compression ratio, as noted above. Accordingly, while the compressible object may include a variety of shapes, such as cubes, pyramids, oblate or prolate spheroids, cylinders, pillows, for example, spherical and elliptical objects with spherical or near spherical inflated geometries are useful for reasons related to the optimization of the compressible mud rheology. Accordingly, the compressible objects may include elliptical and/or spherical objects, such as pressurized hollow metallic spherical and elliptical objects, with an aspect ratio (i.e., the ratio of the major diameter to the minor diameter) of between about 1 and 5 to provide compression ratios of up to 5:1 or greater.
[0039] The design of the compressible object may be further complicated by structural instabilities. For instance, a spherical object for a given internal pressure and diameter may be restricted by structural instabilities characteristic of the spherical object's architecture. The structural instabilities may include local strains, such as equatorial buckling instability during the inflation phase and the cap buckling instability during the compression phase. As such, the design of the compressible object may also be adjusted to compensate for, or reduce the localized strains and instabilities during expansion and compression of the compressible objects. Accordingly, the Finite Element Analysis (FEA) modeling of a spherical object, which may be one embodiment of a compressible object, is discussed further below, as shown in FIGs. 2A-2D.
[0040] FIG. 2A is an exemplary chart and embodiments of a compressible object. In the chart 200, a compressible object is a nearly spherical object, which has an aspect ratio of about 1.0 and wall thickness of 10 microns. The aspect ratio of an object is defined as the ratio of the major axis over the minor axis, which is discussed further below.
[0041] In FIG. 2A, the chart 200 of maximum strain 202 versus compression ratio 204 of the elastic spherical object is shown. The maximum strain 202 is the largest strain at any point on the compressible object in that state. The chart 200, which is generated from a FEA modeling tool, such as ABAQU S TM FEA, includes a response curve 206 of the spherical object in different states. As indicated by the response curve 206, a linear elastic deformation in excess of about 12% is required to provide a compression ratio of at least 5:1. Along the response curve 206, the maximum elastic deformation does not occur uniformly over the object surface during compression, but is localized due to buckling instabilities during compression.
[0043] Based on the discussion above, the compressible object should have a tensile strength sufficient to handle the internal pressure and a recoverable linear elongation or elastic strain large enough to handle the required deformation. If the spherical or near spherical compressible object shell is assumed to be metallic, then the metal or metal alloy should have sufficient tensile strength within its elastic limit to contain the internal pressure and at least 12% recoverable linear elongation. While the tensile strength may be easily achieved, few metals or metal alloys have an elastic strain limit in excess of 1%. If the recoverable linear elongation of greater than 1% is desired, typical materials may not be sufficient. The exceptions to this limitation are some amorphous metal alloys with a limit of elastic strain approaching about 2% and the shape memory alloys (e.g., the Nitol family of NiTi alloys), which exhibit pseudo-elastic strains of up to 8% with less than about 0.1 % permanent deformation. Accordingly, typical metal or metal alloys cannot provide the at least 12% recoverable linear elongation if a spherical structure is utilized as the initial shape.
[0044] To provide the required recoverable linear elongation, the compressible object may be designed to divide the deformation of the compressible object into different states. For instance, the compressibte objects may have three different states, such as an initial state, an expanded state, and a compressed state. In one embodiment the initial state may be, for example, an oblate spheroid with an aspect ratio less than 1.0. FIG. 2C shows an oblate spherical object 220 having a major axis 222 and a minor axis 224. As noted above, the aspect ratio of the object 220 in the initial state is defined as the ratio of the major axis 222 over the minor axis 224. With these states, the required deformation of the compressible object is divided into two phases. The overall required deformation may be divided between an expanded state and a compressed state. The inflation or first phase involves the expansion of the compressible object from the initial state to the expanded state, which may be limited by the tensile strength of the wall material and/or structural instabilities of the fully expanded compressible object characteristic of the initial state of the compressible object architecture and the initial internal pressure. [0045] In particular, in FIG. 2D1 an oblate spherical object 230 with an initial
[0046] The second phase may involve the compression of the object from the expanded state back to about the initial state during which the deformation due to the initial expansion is nearly fully recovered and a subsequent further compression to the fully compressed state, which may again be limited by the elastic strain of the wall material of the fully compressed object. The compressed state may be, for example, an equilibrium compressed shape based on the hydrostatic compression exerted on the compressible object at a certain downhole depth. Accordingly, the compressible objects may be designed using these states to provide a suitable compression ratio that is beneficial for use within a wellbore.
[0047] FIGs. 3A-3C are exemplary embodiments of a compressible object in different states in accordance with aspects of the present techniques. In the embodiments of FIGs. 3A-3C, FEA modeling is utilized to demonstrate the different states of a compressible object, which is an ellipsoid in this example. Each of these FIGs. 3A-3C is a partial view of the compressible object in different states. As shown in FIG. 3A, a elliptical object may be in the initial state 300 and have a major axis 302 and a minor axis 304 with the aspect ratio being 4:1. In FIG. 3B, the elliptical object may be in the expanded state 306 and have a major axis 308 and minor axis 310 and an aspect ratio less than (i.e. <) 4:1. In FIG. 3C1 the elliptical object may be in compressed state 312 and have a major axis 314 and minor axis of 316 and an aspect ratio greater than (i.e. ») 4:1. Accordingly, the aspect ratio for each of the different states 300, 306 and 312 may differ based on the expansion and/or compression of the elliptical object. Compressible objects having different initial aspect ratios is discussed further in FIG. 4.
[0048] FIG. 4 is an exemplary chart of different initial shaped compressible objects in accordance with aspects of the present techniques. FEA modeling is utilized to generate the chart 400 of the maximum strain 402 versus compression ratio 404 for different compressible objects having a wall thickness of 15 microns. The chart 400 includes a first response curve 406 for a spherical object, a second response curve 407 of an elliptical object having a 2:1 aspect ratio, a third response curve 408 of an elliptical object having a 3:1 aspect ratio, a fourth response curve 409 of an elliptical object having a 4:1 aspect ratio, which may be the elliptical object in FIGs. 3A-3C, and a fifth response curve 410 of an elliptical object having a 5:1 aspect ratio.
[0049] As indicated by the response curves 406-410, the maximum strain increases and decreases between the various states. For objects with an initial aspect ratio less than 3:1, the maximum linear elastic strain behavior for compression ratios less than 3:1 is dominated by cap buckling instabilities described above. For compressible objects with an initial aspect ratio greater than 3:1, the maximum strain decreases from the expanded state to a minimum value at or close to the initial state, which is a global minimum for the strain on the compressible object. Then, the maximum strain increases from the initial state until the fully compressed state is reached. As such, the maximum strain at the initial state of the compressible objects is near zero as indicated by the response curves 406-410. This aspect is clearly demonstrated by the fourth response curve 409. Along the response curve 409, the expanded state is located at the point 416, the initial state is located at the point 414 and the compressed state is located at the point 412. Clearly, the initial state of the compressible object has the lowest strain in comparison to the expanded and compressed states. In addition, this compressible object has a maximum strain of about 0.085, which is about the value of the maximum recoverable strain for the austenite to martensite phase transformation of the Nitol family of alloys in their pseudo-elastic state. That is, the response curve 409 indicates that the elliptical object having a 4:1 initial aspect ratio is a suitable structure and wall thickness to provide the specified compression ratio of greater than 5:1 with an internal pressure useful for the practice of the invention disclosed in International Patent Application Publication No. WO 2006/007347. Each of the other response curves 406-408 and 410 exceed the maximum recoverable strain of 0.085. Strains above the austenite to martensite phase transformation completion strain of approximately 8% may experience permanent deformation resulting in limited fatigue life in cyclic deformation.
[0050] From this chart 400, the inflation and subsequent compression of the compressible object is bounded by an equatorial buckling instability during the inflation phase and the cap buckling instability described earlier during the compression phase. By modeling the inflation and subsequent compression, the initial architecture of the compressible object may be designed to minimize the recoverable elongation for the specific compression ratio. In particular, for a compressible object of constant wall thickness fabricated from a NiTi shape memory alloy with an austenite to martensite phase transformation temperature below about 0 0C (Celsius) and a target expanded internal pressure of 1500 psig (pounds per square inch gauge), the initial aspect ratio of the compressible object before inflation may preferably be between about 3 and 4 with a wall thickness between about 15 and 20 microns to avoid exceeding about 8% linear elongation anywhere in the wall of the compressible object for a compression ratio of up to 8:1. As noted above, to be useful for the practice of Patent Application No. WO 2006/007347, the alloy should be in a pseudo-elastic condition. Ordinary shape memory alloys with transformation temperatures above about 0 0C are not useful for this application. The requirement of an austenite to martensite phase transformation temperature below about 0 °C recognizes that the alloy should remain pseudo-elastic over the entire temperature range encountered during operation of the compressible objects in the drilling mud.
[0051] Based on the modeling methods discussed above, compressible objects may be designed of a certain material and having a specific architecture to provide specific compression ratios that are within the deformation limitations of existing materials. With these compression ratios, the compressible objects may be useful for certain applications, such as drilling and production operations, which are described above. As an example, the compressible objects may be useful if they provide a recoverable compression ratio greater than or equal to five times the expanded state at a specific depth interval of interest. The compressible objects may be included in the variable density drilling mud in a volume fraction of up to 40% or 50% to provide a change in drilling mud density representative of typical PPGs and/or FGs. By changing the density of the drilling mud by adding up to 50% by volume of small low-density, compressible objects, which may have a diameter of about 1 millimeter (mm), the pressure gradient within the wellbore may be substantially controlled to reduce the number of casing strings utilized within the wellbore. In particular for a deep-water application, the number of casing intervals may be reduced substantially below that achievable with dual gradient or multi- gradient systems without major modification of existing hardware or equipment. As such, the well cost may be reduced by up to 30 to 50% for certain applications. Accordingly, the selection of the compressible objects and fabrication of the compressible objects is discussed further below in FIG. 5.
[0052] FIG. 5 is an exemplary flow chart of the selection and use of the variable density drilling mud for the drilling system 100 of FIG. 1 in accordance with certain aspects of the present techniques. This flow chart, which is referred to by reference numeral 500, may be best understood by concurrently viewing FIGs. 1, 3A-3C and 4. In this flow chart 500, compressible objects and drilling fluid may be selected to formulate a variable density drilling mud for a well. These compressible objects may include objects that each have a shell enclosing an interior region, and wherein the compressible object has (a) an internal pressure (i) greater than about 200 psi at atmospheric pressure, 500 psi at atmospheric pressure, 1500 psi at atmospheric pressure and/or 2000 psi at atmospheric pressure, and (ii) selected for a predetermined external pressure, wherein external pressures that exceed the internal pressure reduce the volume of the compressible object; (b) wherein the shell experiences less strain when the external pressure is about equal to the internal pressure than when the external pressure is above or below a predetermined compression interval of the compressible object or wherein the shell is configured to experience less strain when the external pressure is about equal to the internal pressure than when the external pressure is greater than the internal pressure or less than the internal pressure; and/or (c) compressible objects having a shell that encloses an interior region at least partially filled with a foam. Then, the variable density drilling mud may be utilized to enhance the drilling operations of the well. This process may enhance the drilling operations by providing a variable density drilling mud that extends the drilling operations to further limit or reduce the installation of additional casing strings. Accordingly, drilling operations performed in the described manner may reduce inefficiencies from utilizing additional casing strings from drilling operations.
[0053] The flow chart begins at block 502. At block 504, the FG and PPG for a well may be determined. For example, the FG and PPG may be obtained by receiving information from the drilling location and/or performing calculation to estimate the FG and PPG. Then, compressible objects may be selected to provide specific volumetric changes, as shown in block 506. The selection of compressible objects may include operational considerations, such as removal of the compressible objects from the drilling mud for re-circulation at the surface, limiting potentially detrimental effects of the high volume fraction of compressible objects on the rheology of the drilling mud and facilitating the flow of the compressible objects through the pumps and orifices in the flow path. As such, the compressible objects may be sized to have an equivalent diameter between 0.1 millimeter (mm) and 50 mm, and/or preferably between 0.1 mm and 5.0 mm. The equivalent diameter is defined as the diameter of a sphere of equal volume as the fully expanded compressible object at atmospheric pressure. Further, the selection of compressible objects may include utilizing compressible objects of different sizes or volumes at the surface of the wellbore and/or different shapes to manage the viscosity increases of the drilling mud. The selection of the compressible objects is further described in FIG. 6.
[0054] At block 508, the drilling fluid may be selected. The drilling fluid, which may include various weighting agents, may be selected to provide a specific density that may interact with the compressible objects to maintain the drilling mud density between the FG and PPG, which is discussed further below. The compressible objects and the drilling fluid may be combined in block 510. The combination of the compressible objects and the drilling fluid may involve mixing or blending the compressible objects with the drilling fluid, as described in International Patent Application No. PCT/US2007/003691 , filed 13 February 2007. Further, the compressible objects and the drilling fluid may be combined prior to shipping to the drilling location or shipped individually with the compressible objects and the drilling fluid being combined at the drilling location. It should be noted that the compressible objects may be shipped in refrigerated vehicles, such as trucks and ships, to reduce risks associated with the release of internal pressure within the compressible objects.
[0056] FIG. 6 is an exemplary flow chart of the selection and fabrication of the compressible objects discussed in the flow chart of FIG. 5 in accordance with certain aspects of the present techniques. This flow chart, which is referred to by reference numeral 600, may be best understood by concurrently viewing FIGs. 1, 3A-3C, 4 and 5. In this flow chart 600, a process for selecting compressible objects to maintain the density of a drilling mud within the well between the PPG and FG is described. Beneficially, the use of compressible objects in the variable density drilling mud may enhance drilling operations by reducing the size of the wellbore and casing strings, and may provide access to greater depths.
[0057] The flow chart begins at block 602. At block 604, the FG and PPG for a well are obtained. The FG and PPG may be obtained by receiving information from the drilling location and/or performing calculation to estimate the FG and PPG. Then, a structure for each of the compressible objects is selected, as shown in block 606. The selection of the structure for the compressible objects may include using finite element analysis (FEA) methods to match structures and geometries of compressible objects to properties of the available materials, as described above. At block 608, wall materials for the compressible objects are selected. The selection of wall materials may include metals and/or metal alloy thin films formed mechanically or by depositional methods, polymers with or without micro and/or nanofiber re- enforcement in a polymer matrix to achieve the specific properties of the wall material (e.g., as defined by FEA analysis of the object compression). In addition, wall materials may include ex-foliated inorganic mineral as re-enforcement or as a barrier to gas permeability in a polymer matrix; metal and/or metal alloy thin films formed by depositional methods on polymer surfaces with or without chemical modification of the polymer surface to form a structural wall or a barrier to gas permeation. The metal and/or metal alloy thin films may be deposited on polymer sheet prior to forming of the compressible object or on a pre-formed compressible polymer object. The metal layer may be formed on the inside or outside surface of the compressible objects or incorporated within a polymer wall or polymer laminate of the same or different polymers.
[0058] Surface treatments may be selected for the fabrication of the compressible objects in block 610. The surface treatments may include physical and/or chemical surface treatments to improve the continuity and adhesion of metal and/or metal alloy films on the surface of the polymer objects or to enhance the chemical and/or physical compatibility of the polymer or metallic exterior wall of compressible objects with the drilling fluid.
[0060] At block 614, the compressible objects may be verified or tested. The verification and testing may include cyclic compression tests to verify the internal pressure and to quantify the fatigue life of the compressible objects with or without micro-structural analysis of the structural wall and the joints if any. Then, the compressible objects may be stored, as shown in block 616. The storage of the compressible objects may include placing the compressible objects in a storage vessel. The compressible objects may be stored at ambient pressure or at a pressure equal to or higher than the internal pressure of the compressible objects to facilitate packing of the compressible objects in the storage vessel. Alternatively, the compressible objects may be stored in a cold environment to reduce the internal pressure inside the compressible objects. The cold compressible objects may then be stored in a vessel at ambient pressure or at elevated pressure to facilitate packing of the compressible objects in the storage vessel and shipping the compressible objects to another location, such as the drilling location, for storage or other similar activities. The process ends at block 618.
[0061] Accordingly, based on the discussion above, the selection and use of these compressible objects may involve different aspects that affect the design of the compressible objects. For instance, the nature of the transition to gas compression controlled deformation is dependent on the mechanical properties of the shell or wall material and the evolution of those properties in repeated compression cycles. As such, the compression of hollow objects results in a different gradient of mud density above and below the depth defined by the initial internal pressure of the hollow objects. Because the use of compressible objects having different initial internal pressures may be beneficial to enhance or extend drilling operations, changing the volume fraction and distribution of initial pressures of compressible objects may achieve the desired result of maintaining the effective mud weight between the PPG and FG.
[0064] To determine the architecture of the compressible objects, as noted in block 606 of FIG. 6, a finite element numerical modeling method may be utilized. The finite element numerical modeling method may include implicit methods and/or explicit methods. In these methods, the shell walls or elements may be represented by mesh size and shape tailored with higher resolution in regions of interest, such as regions of high stress and/or strain for compressible object construction. The finite element numerical model may be used to simulate the entire three dimensional object or a segment of the object related to the three dimensional object by symmetry. Further, the architecture of the compressible objects may be influenced by various criteria, such as the materials and use of the compressible objects, which are discussed in this and other portions of the application.
[0069] As a specific example, the finite element numerical model of the compressible object of FIGs. 3A-3C is discussed. In these embodiments, the compressible object has the shape of an oblate ellipsoid. The initial aspect ratio may be in the range of 1 to 10, with a more preferred aspect ratio being in the range of 2 to 5. The use of an internally pressurized oblate ellipsoid hollow compressible object with an initial aspect ratio greater than 1 has the advantage that at ambient external surface pressure, the ellipsoid object inflates and approaches an aspect ratio of about 1 depending on the internal pressure and material properties, as shown in FIG. 3B. If the ellipsoid object has an initial aspect ratio of 4:1, a uniform NiTi alloy wall thickness of 10 microns and an internal pressure of 1500 psig, the aspect ratio in the expanded state is about 1.22:1. As the external pressure increases, the ellipsoid object tends to return to an initial state 300. In the initial state 300, the aspect ratio of the ellipsoid object is that of the original design with little elastic strain, as shown in FIGs. 3A and 4. Then, as the pressure continues to increase, the ellipsoid object is compressed further into a compressed state 312, as shown in FIG. 3C. WaII Material for Compressible Objects
[0070] In addition to the architecture, various materials may be utilized for the wall of the compressible objects based on the criteria discussed above, as noted in block 608 of FIG. 6. In particular, the shell or wall materials may be divided into two classes of commercially available materials, which are metal materials and polymer materials. The metal materials may include metals, metal alloys, and alloys with pseudo-elastic behavior (e.g., deformations associated with a reversible stress induced structural phase transformation). Further, the super-plastic behavior of ultra thin (i.e., < 500 Angstroms (A)) metal or metal alloy films may also be used to make a wider variety of metals and metal alloys (e.g., Aluminum (Al), Copper (Cu), Nickel Titanium (NiTi), etc.) suitable for application as a thin permeation barrier in conjunction with a non-metallic load bearing wall that satisfies the mechanical properties of the load bearing wall. Specifically, the metal materials may include, but are not limited to, binary or near binary NiTi, ternary alloys of NiTi with iron and chromium alloying additions, Magnesium-40Copper (Mg-40Cu) alloys, Beta- Titanium-9.8Molybdenum-4Niobium-2Vanadium-3Aluminum (β-Ti-9.8Mo-4Nb-2V- 3Al) alloys, metallic glasses and amorphous metals (e.g. Zirconium (Zr), Iron (Fe) and/or Magnesium (Mg) based alloys) and the like. The polymeric materials may include polymers and polymer blends with or without reinforcement (e.g., micro to nano-fiber, nanotubes, exfoliated inorganic fillers with appropriate orientation within the polymer wall etc.). Examples of polymers with suitable properties include but are not limited to commercially available polyimide, such as Ubilex-R and Ubilex-S.
[0071] Because each of these materials has specific properties, such as tensile strength and recoverable elongation, the material utilized in the walls of the compressible objects is a factor in determining the thickness of the wall. The determination may be based upon finite element numerical modeling, as noted above, to evaluate different thicknesses of the shell or wall with different materials. For instance, if the load bearing wall material is a metal or metal alloy, only metals and metal alloys with sufficiently high elastic or pseudo-elastic behavior should be selected because deformations associated with a reversible stress induced structural phase transformation have to be recoverable for reuse of the compressible objects. As noted above, even these selected materials have to be combined with careful design of the geometry of the exterior shell of the compressible object to avoid strain localization during compression and re-expansion. In particular, the geometry and material may be utilized for optimization of the wall thickness relative to particle size; variation of the bearing wall thickness and/or mechanical properties with location on the compressible objects' surface; and/or variation of the aspect ratio and major diameter of an oblate spheroid hollow compressible objects, etc. Accordingly, these various factors are considered in selecting a material for the compressible objects.
[0072] As an example of the variation of wall thickness, the wall material may be utilized to influence the compression ratios of the compressible object, such as the elliptical object discussed above in FIGs. 3A-3C. In FIG. 7, the FEA calculations provide various shapes that have different compression ratios within the limits defined by existing materials properties. The FEA calculations may provide compressible objects having an aspect ratio between 2 to 5, with an equivalent- diameter-to-wall-thickness ratio between 20 and 200, or more preferably between 50 and 100. As shown in FIG. 7, a chart 700 of the effect of wall thickness is shown for maximum strain 702 of compressible objects against the equivalent diameter to wall thickness ratio 704 for various shapes, which are shown by curves 706-711 , generated from finite element numerical modeling. For sphere-shaped compressible objects, curve 706 has a compression ratio of 3.5, curve 707 has a compression ratio of 3, and curve 708 has a compression ratio of 2. For the ellipse shaped compressible objects, curve 709 has a compression ratio between 3.5 and 2, curve 710 has a compression ratio between 3 and 2, and curve 711 has a compression ratio of about 2. It is clear from the chart 700 that compressible objects having an aspect ratio greater than unity with a thinner wall (i.e., higher equivalent-diameter-to- wall-thickness ratio) are preferable because they provide higher compression ratios with correspondingly lower maximum strain. Also, it may be preferable to maintain the maximum strain below a specific value, of about 0.06 as defined by the maximum allowable strain to achieve adequate fatigue life of the structural wall. Typically, a minimum fatigue life of at least 2000 to 3000 cycles is desirable. Based on this limitation, an ellipsoid object with an aspect ratio at 2 or more and equivalent- diameter-to-wall-thickness ratio greater than 65 provides a compressible object that is below the specific value, as shown on curve 711.
[0074] As discussed in block 610 of FIG. 6, various surface treatments may be utilized for the compressible objects. The surface treatments may be utilized to improve the continuity and adhesion of polymer layers or metal and/or metal alloy films on the surface of the compressible objects, such as polymer objects. Accordingly, the surface treatments may be utilized to enhance specific properties, such as compatibility with the base fluid and the permeability of the shell layers to maintain the internal pressure, which is discussed further below.
[0075] For internally pressurized compressible objects having a load bearing wall of a polymer and/or an elastomer with or without reinforcement, a surface treatment may be utilized to enhance the continuity of a metal and/or non-metal film deposited on the surface of the polymer to reduce the gas permeability of the load bearing wall. In general, elastomers, crystalline polymers and/or polymer blends have gas permeabilities too large to be useful for the fabrication of the compressible objects. Accordingly, in addition to the incorporation of exfoliated inorganic fillers in the polymer wall, the deposition of a continuous, thin (i.e., < 500 Angstrom) low gas permeability coating either on the surface of the wall or incorporated into a layered wall structure may be used. For example, the coating may be a thin metal, metal alloy or inorganic gas permeation barrier, which is applied through a variety of physical and/or chemical treatments to the exterior of the surface wall of the compressible object. In particular, the deposition coating may be less than 500 A in thickness and include Al, NiTi, or any other suitable material. Surface treatments to enhance the uniformity and/or continuity of these permeation reducing layers may include: (1) Anionic functionalization of the surface e.g., sulfonation, carboxylation, i.e., acid formation, as well as other anionic functionalizaton methodologies and chemistries used by those well-versed in the state of the art. (2) Cationic quaternization functionalization chemistries e.g., sulfonium salts, phosphonium salts, ammonium salts, used by those well-versed in the state of the art. (3) Zwitterionic ionic functionality and amphoteric functionality practiced by those well-versed in the state of the art. (4) Maleation functionalization and the associated reactions known by those well-versed in the state of the art. (5) Controlled oxidation e.g., peroxides, high temperature oxygen plasma etching, ozone, and the like. (6) Chemical vapor deposition methodologies and associated chemistries. (7) Corona discharge approaches to surface functionalization used by those well-versed in the state of the art.
[0076] A wide variety of methods are available for deposition of metal and/or inorganic barrier coatings. One of the factors that may influence the selection of deposition method is the internal pressure of the compressible object. For instance, if little or no initial internal gas pressure is contained within the compressible objects, then a low permeability metal, metal alloy or inorganic coating may be utilized through various low pressure physical and chemical deposition methods to uniformly coat the non-planar geometry of the compressible objects. If the compressible object's internal pressure and the wall permeability is such that the low pressure environment (i.e., typically < 1x10'3 mm of Hg) required for low pressure physical and chemical deposition methods is not maintainable, deposition methods compatible with the internal gas pressure and relatively high wall gas permeability may be used. In this example, the compressible objects may be maintained in a high pressure gas or liquid environment to prevent loss of internal pressure through the wall of the compressible object during storage and coating. For a high pressure liquid environment, the coating of the wall surface may be accomplished, for example, by electro or electro-less plating using methods familiar to those skilled in the art. For the high pressure gas environment, the coating of the wall surface may be accomplished by, for example, chemical vapor deposition (CVD) or ultraviolet chemical vapor deposition (UV-CVD) deposition.
[0077] Alternatively, the internal gas pressure inside the compressible objects may be reduced to a level that allows application of a range of commercial low pressure physical and chemical deposition methods available for an un- pressurized object or polymer sheet. In this example, a gas, which may be condensed by lowering the temperature of the compressible object, may be utilized for the internal pressurization of the compressible object. For instance, if the gas internal to the compressible object is oxygen (O) at a pressure of 10 mPa, subsequent cooling the compressible objects to the temperature of liquid nitrogen (LN2) at atmospheric pressure may reduce the internal pressure to less than or equal to 1 x 10'3mm of Hg.
[0078] Similar considerations for a hollow polymer load bearing wall may be applied for internally pressurized compressible objects having a load bearing wall of polymer and/or elastomer foam and gas barrier wall of a metal and/or non-metal permeation barrier, or for a polymer and/or elastomer ultra thin hollow shell or a polymer and/or elastomer foam used as a template for deposition of a load bearing metal and/or metal alloy wall, as noted above. In the latter example, an ultra thin polymer shell or polymer foam may be utilized as a template for the deposition of a relatively thick metal and/or metal alloy load bearing wall. The metal or metal alloy load bearing wall in this example may have a thickness from about 5 microns to 50 microns. The ultra thin polymer shell or polymer foam may include any polymer and/or elastomer with or without reinforcement and surface treatments to enhance the uniformity and continuity of the metal and/or metal alloy load bearing wall. In this example, the thickness of the ultra thin polymer shell and/or the mechanical strength of the foam need only be sufficient to maintain the desired shape of the particle during the deposition process.
[0079] As discussed in block 612 of FIG. 6, once the structure and wall materials are selected for compressible objects, various fabrication techniques may be utilized to create the compressible objects. These fabrication techniques may include various processes, such as patterning, deposition, thermo-mechanical processing and other similar fabrication processes. The patterning processes, which are processes that shape material into another form, such as compressible objects, may include chemical etching, mechanical etching and the like. The etching processes are processes that remove material from a base material. The deposition processes, which are processes that coat or transfer a material onto another material, may include physical vapor deposition, chemical vapor deposition, electrochemical and/or electro-less deposition, metallization, sputtering, evaporation, molecular beam epitaxy and the like. The thermo-mechanical processes, which are processes that form or change a materials shape and microstructure, may include cold rolling, hot rolling, swaging, drawing, cutting, tempering, solution annealing and the like.
[0081] Accordingly, the fabrication processes may be configured to create compressible objects that are gas filled polymer objects including internal structures being either hollow or at least partially filled with foam. For instance, FIGs. 8A-8B are exemplary embodiments of fabrication processes that create compressible objects having hollow interiors. Similarly, FIGs. 9, 10 and 11A-11B are embodiments of fabrication processes that create compressible objects having foam interiors or based upon foam templates. A. Fabrication of Compressible Objects as Hollow Objects
[0082] The fabrication processes described below relate to the fabrication of compressible objects that are formed as hollow objects, which may or may not be gas filled. These fabrication processes may be utilized to form compressible objects that each has a shell enclosing an interior region, each of the compressible object has (a) an internal pressure (i) greater than about 200 psi at atmospheric pressure, 500 psi at atmospheric pressure 1500 psi at atmospheric pressure or 2000 psi at atmospheric pressure and/or having a shell that encloses an interior region and (U) selected for a predetermined external pressure, wherein external pressures that exceed the internal pressure reduce the volume of the compressible object; (b) the shell configured to experience less strain when the external pressure is about equal to the internal pressure than when the external pressure is greater than the internal pressure or less than the internal pressure or the shell that experiences less strain when the external pressure is about equal to the internal pressure than when the external pressure is above or below a predetermined compression interval of the compressible object; and/or (c) the shell is at least partially filled with a foam. While a variety of fabrication processes are described, FIGs. 8A-8B are exemplary embodiments of fabrication processes that create compressible objects having hollow interiors.
[0083] FIGs. 8A-8B are exemplary embodiments of fabrication processes utilized in the flow chart of FIG. 6 in accordance with certain aspects of the present techniques. In FIG. 8A, an exemplary embodiment of an apparatus for creating compressible objects in accordance with the present techniques is shown. In this embodiment 800, compressible objects, such as hollow polymer shells or polymer foam structures, may be fabricated in a pressurized environment formed by a pressurized chamber 802. For exemplary purposes, the compressible objects are shown as hollow polymer shells 804 with a gas interior 806, but may include polymer foam structures and other compressible objects discussed above.
[0085] Further, during or after polymerization and/or separation of the hollow polymer shells 804, the pressure surrounding the hollow polymer shells 804 may be lowered to expand the hollow polymer shells 804 into its final size and shape in the expanded state. This expanded state may be predetermined by wall thickness, material mechanical properties, object architecture and internal pressure before, during or after cooling of the walls. If the polymer wall is the load bearing member, expansion of the diameter following synthesis may be used to alter the mechanical properties of the polymer wall. For example, by strain re-orientation of the polymer chains and/or re-orientation of the reinforcement in the polymer wall of the hollow polymer shells 804.
[0086] Specific adjustments may be incorporated for the fabrication process based on the materials utilized. For instance, if the polymer material 814 is a polymer melt with or without reinforcement, the orifice 808 may be heated to reduce the melt viscosity to achieve the desired flow properties of the polymer melt. Also, if the polymer material 814 is a polymer monomer or a mixture of monomers with or without reinforcement and with or without an initiator, the polymerization of the walls of the polymer bubble 820 after separation from the orifice 808 may be accomplished by a variety of processes, such as ultra violet polymerization, free radical polymerization, therm o-chemical polymerization, etc., which are familiar to those skilled in the area of polymer synthesis.
[0087] In FIG. 8B, another exemplary embodiment 830 of an apparatus for creating compressible objects in accordance with the present techniques is shown. In this embodiment 830, compressible objects, such as hollow polymer shells or polymer foam structures, may be fabricated in a pressurized environment formed in a pressurized chamber 832. The pressurized chamber 832 is divided into a lower chamber 838 having a gas inlet 840 and an upper chamber 842 having a fluid inlet 844 and a fluid outlet 846. For exemplary purposes, the compressible objects are shown as hollow polymer shells 834 with a gas interior 836, but may include polymer foam structures and other compressible objects discussed above.
[0088] In this fabrication process example, a thin film 848 of a suitable polymer melt or polymer precursor may be formed on a plate 850 perforated by a large number of orifices or holes 852. The size and spacing of the holes 852 may be arranged to cause the continuous formation of gas filled bubbles 854, which have a hollow polymer shell 834 with a gas interior 836, that separate and float off the plate 850 and into a pressurized fluid filling the upper chamber 842 when the plate 850 is pressurized from below at a desired differential pressure between the upper and lower chambers 838 and 842. It should be noted that a variety of alternative geometries of holes may be utilized to form internally pressurized hollow compressible objects from a thin film of polymer precursor and/or polymer melt. The gas filled bubbles may exit the upper chamber 842 through the fluid outlet 846 and may be separated from the fluid by density difference and subsequently transferred to a container for storage.
[0089] As an alternative exemplary method for creating compressible objects, metal, metal alloy and/or polymer tubes may be utilized to form the compressible objects. In this fabrication process, compressible objects are formed from a tube material by cutting the tube material into desired lengths and closing the ends of the tube material using mechanical, chemical or thermal methods. The internal pressure of the resulting compressible objects, which may be formed in the shape of a pillow, sphere, oblate spheroid, ellipsoid of revolution or any other desirable shape may be controlled by closing the cut ends of the tube and forming the desired shape in a controlled pressure environment. The pressurized environment may be a pressurized chamber, which is similar to the pressurized chambers discussed above. In addition, the compressible objects may be formed either before or after metallization of the polymer wall of the tube material from a polymer and/or elastomer tube with or without reinforcement.
[0090] As another alternative example method for creating compressible objects, preformed sheets may be utilized to form the compressible objects. In this method, mechanical, thermal or chemical joining of preformed sheets may be utilized to fabricate compressible objects. The preformed sheets may include a layered composite structure, which may include two embodiments. One embodiment may be a relatively thick structural load bearing polymer wall combined with a relatively thin continuous metal, metal alloy and/or non-metal permeation barrier layer. In particular, the structural load bearing polymer wall may have a wall thickness between about 5 micron and 50 microns, while the continuous metal or metal alloy permeation barrier layer may have a wall thickness that is less than about 500 Angstrom. The second embodiment being a thin polymer sheet as a template for the deposition of a relatively thick metal or metal alloy layer that serves as both a structural wall and a barrier to gas permeation. For instance, the thin polymer sheet may be less than about 5 micron, while the metal or metal alloy layer may have a wall thickness between about 5 micron and 50 microns. Any combination of layered or multiply layered embodiments with polymer thickness and metal or metal alloy thickness within these limits may be utilized for other embodiments.
[0093] As an additional fabrication technique, the method of composite sheet fabrication outlined above may also be used to fabricate free standing relatively thick metal and metal alloy sheet suitable for mechanical forming into the components of compressible or collapsible objects or particles. This approach to the fabrication of free standing metal or metal alloy sheet is particularly useful when thin metallic sheet is difficult to fabricate by conventional thermo-mechanical methods used in the fabrication of metal sheet. In particular, the metal and metal alloy sheet may have a thickness between about 5 micron and 50 micron. To form a free standing metallic sheet, the polymer template may be removed from the thin metallic sheet following deposition of the metal or metal alloy before or after any additional thermo- mechanical treatment required to consolidate the deposited thin sheet. Removal of the polymer template may be accomplished by a variety of mechanical, chemical and/or thermal methods known to those of ordinary skill in the art. Alternatively, the polymer template sheet may be pre-formed in the components of the compressible objects prior to deposition of the metal or metal alloy thin film to form a free standing metal or metal alloy pre-form.
[0094] As another fabrication technique, hollow compressible objects may be formed by physical and/or chemical vapor deposition (as described above) of the chemical constituents of a thermoset polymer onto thermally depolymerizable hollow poiymer template or polymer foam. Subsequent to deposition, the themoset polymer constituents may be partially reacted together by raising the temperature to form a self supporting themoset polymer preform layer on the surface of the depolymerizable hollow polymer shell or polymer foam template. Subsequent to the formation of the self supporting thermoset polymer preform layer, the temperature may be further increased to depolymerize the hollow and/or foam template and the depolymerization products removed from the resulting hollow self supporting object by diffusion through the thermoset preform wall. Finally, the partially cured self supporting hollow preform thermost objects may be placed into a high pressure vessel and the pressure inside the hollow objects equilibrated by diffusion through the thermoset preform wall with a high gas pressure established inside the vessel. Subsequently, the temperature may be raised further in the high pressure gas environment to fully cure the thermoset polymer in order to lower the gas permeability of the wall and to achieve the optimum mechanical properties of the wall material. As before, metallization of the exterior surface of the fully cured and pressurized hollow thermoset polymer shell may be accomplished by the methods described above for the coaxially blown pressurized hollow polymer shells.
[0095] Further, as another embodiment, the compressible objects may be mechanically conditioned during fabrication to strengthen the structural wall of the compressible objects by reorientation of the micro and/or nano-fiber reinforcement and/or the polymer chains including the wall material by mechanical stresses. This mechanical conditioning may include, but is not limited to, expansion of the compressible object to its final size and shape.
[0098] As a first embodiment, blowing agents may be utilized to form the foam template for the compressible objects. Typically, the use of physical blowing agents results in closed-cell foam template, which may be formed from various materials. For instance, polyurethane (PU), polystyrene (PS) and polyvinyl chloride (PVC) are materials utilized in manufacturing polymer foams. Typically, PU foams are prepared by in situ generation of carbon dioxide (CO2), while PS and PVC foams are prepared using physical blowing agents like nitrogen (N2) and CO2. The use of physical blowing agents reduces any contaminating solvents from hindering the process. The use of CO2 and N2 has a number of benefits, such as chemical inertness, non-combustibility, natural occurrence, low cost, ready availability, environmental acceptability (no ozone depletion) and low human toxicity.
[0099] Each of the polymer foaming techniques that use physical blowing agents rely on the similar principles. These principles are (1) saturation of the polymer with a gaseous penetrant (blowing agent) at high pressure; (2) quenching of the polymer/gas mixture into a super-saturated stage either by reduced pressure or increased temperature; and (3) nucleation and growth of gas cells dispersed throughout the polymer matrix. Upon quenching of the polymer/gas mixture, the solubility of the gas in the polymer template decreases, which results in clustering of gas molecules in the form of nuclei. As gas diffuses into the forming cells, the free energy of polymer template is lowered. The cell nucleation process governs the cell morphology of the polymer material and properties of the polymer material. Also, this process may occur homogeneously throughout the material or heterogeneously at high-energy regions, such as phase boundaries. In the high energy regions, the free energy to nucleate a stable void is less compared to homogeneous nucleation. As a result, preferential nucleation of voids occurs at the interface.
[00100] In semicrystalline polymers, the crystalline domains may serve as heterogeneous nucleation points to generate gas bubbles. In general, cell growth is controlled by the time that the gas has to diffuse into the cells before the quenching, the temperature of the fabrication process, the degree of supersaturation, the rate of gas diffusion into the cells, the hydrostatic pressure or stress applied to the polymer matrix, the interfacial energy and the visco-elastic properties of the polymer/gas mixture. The stiffness of the polymer template is typically controlled by the foaming temperature. It should be noted that a reduction in average cell size generally increases stiffness. The work necessary to expand the gas cell has to overcome the additional stress resulting from the increased stiffness. By increasing the saturation pressure, the free energy barrier for the formation of stable nuclei is decreased and additional nucleation sites are formed due to matrix swelling, free volume changes, and/or the formation of crystalline interfaces. This results in an increased cell density and consequently a decreased average cell diameter. Semicrystalline . polymers exhibit considerably higher cell densities than amorphous polymers, which are attributed to the contribution of heterogeneous nucleation at the amorphous/crystalline interfacial regions. Because the gas does not dissolve in crystallites, the nucleation is nonhomogeneous, which makes it difficult to control the cellular structure of semi-crystalline foams. As a result, polymers with a low crystallinity afford foams with an almost uniform structure. As the crystallinity of the polymer is increased, less desirable non-uniform foams with irregular cell sizes are obtained.
[00106] Further, it should be noted that the surface treatments may be adjusted for different foam templates. For instance, if polystyrene is the foam template, it is highly non-polar and chemically reactive polymer. The degree of functionalization, i.e., sulfonation, may be controlled via a number of parameters such as: solvent, sulfuric acid concentration, reaction temperature, reaction time, catalyst, and catalyst concentration. As such, it should be noted that the surface functionalization chemistry and subsequent procedures may be modified to accommodate the surface chemistry and structure of the material, such as nylon, polyesters, polyurethanes among many other polymeric materials. The surface functionalization and etching may include acid treatment, base treatment, oxidation, nitration, sulfonation, phosphonation among many other chemistries. See J. March, "Advanced Organic Chemistry: Reactions, Mechanisms, and Structure", Third Ed., John Wiley & Sons, New York (1985), sections relating to sulfonation, mild oxidation, esterification, carboxylation, free radical addition reactions, free radical graphing reactions, and quatemization, and the like.
[00107] As a first specific example, foam templates may be coated uniformly by a process, such as electroless copper plating, to form the rod-like foamed object. The foam template may be an air-filled foam microcapsule having cells of about 1000 μm (micro-meter) to 1500 μm in diameter. If this foam template is polystyrene, the fabrication process may include fuctionalization of the polystyrene rod by exposure to a 30% solution of H2SO4 for a period of 21 hours. The surface of the functionalized polymer can be activated using a tin-palladium (Sn-Pd) activation process, otherwise known as seeding. This seeding process is familiar to those skilled in the art. The process involves successive immersions of the polystyrene rod in acidic tin-chloride (SnCI2) (0.01M) followed by acidic palladium-chloride (PdCI2) (0.01M) solution with rinsing in distilled water between the baths. A 0.01 M Hydrogen- Chloride (HCI) is used after the PdCI2 to remove the remaining Sn compounds from the surface. Each of the baths are performed at room temperature. See B. Ceylan Akis, "Preparation of Pd-Ag/PSS Composite Membranes for Hydrogen Separations", A Thesis, Worcester Polytechnic Institute, (May 2004). The functionalized, Pd seeded polystyrene rod can be placed in a bath flowing at the rate of 73 cc/min (cubic centimeters/minute) containing a copper (Cu) plating solution of CuSO4-5H2O, ethylenediaminetetraacetic acid disodium salt dihydrate, NaOH1 ethylenediamine, and triethanolamine activated with formic acid. See Y. Lin and S. Yen, Applied Surface Science, 178, 116 (2001); W. Lin, H. Chang, Surface and Coatings Technology, 107, 48 (1998); Shu et. al., Ind. Eng. Chem. Res. 36, 1632 (1997); Hanna et al. Materials Letters, 58, 104 (2003). Cu can be plated onto the functionalized, Pd seeded polystyrene rod at 40°C over a period of 90 minutes followed by a distilled water wash. The majority of the surface can be coated with Cu having a thickness that ranges from 0.3 - 0.6 μm.
[00108] Alternatively, if the foam template is an air-filled foam microcapsule having cells of about 250 μm to 500 μm in diameter and a spherical shape, the fabrication process may include fuctionalization and Pd seeding of the polystyrene sphere, as described above. Using the same Cu plating solution and flow rate, the functionalized Pd seeded polystyrene sphere can be plated at 400C for a period of 10 minutes followed by a distilled water wash. As a result, the surface can be coated with a 0.1-0.2 μm thick Cu film that follows the contours of the foam surface.
[00110] As another exemplary fabrication technique, a hollow gas-filled metallic shell may be fabricated by utilizing the Fraunhofer method for producing hollow metallic objects, as shown in FIG. 11 A. See, for example, O. Andersen, U. Waag, L. Schneider, G. Stephani, B. Kieback, "Novel Metallic Hollow Sphere Structures", Advanced Engineering Materials 2000, vol 2, (Apr 2000), pp. 192-195. In this embodiment 1100, foam templates 1102, which may be Styrofoam templates or any of the polymer foam templates described above, may be coated with a metallic material 1104, which may comprise a metal or metal alloy powder and binder. The coating of the foam templates 1102 by metallic material and binder 1104 may be accomplished by fluidized bed coating methods in a vessel 1106. The resulting polymer foam templates coated with a metal or metal alloy powder and binder layer 1108 may then be subjected to a furnace 1110 for annealing. In the furnace, the polymer foam template may be thermally decomposed or reacted to volatile reaction products which are removed by diffusion through the partially sintered metal or metal alloy wall. Subsequently, the temperature may be raised to drive off the remaining binder and the metal material is sintered to obtain a dense metal or metal alloy shell. The resulting compressible objects 1112 may be utilized as part of the variable density drilling mud once it has cooled.
[00124] While the present techniques of the invention may be susceptible to various modifications and alternative forms, the exemplary embodiments discussed above have been shown by way of example. However, it should again be understood that the invention is not intended to be limited to the particular embodiments disclosed herein. Indeed, the present techniques of the invention are to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.

中文:
[0003]本部分意图向读者介绍本领域的各个方面,它们可能与下面所描述和/或要求保护的本发明的示例性实施方式相关。该讨论被认为是有助于向读者提供便于更好理解本发明具体技术的信息。因此,应当理解,这些论述应当以此角度来阅读,而不必认为是对现有技术的承认。
[0008]然而,在可变密度钻井泥浆中使用可压缩物体可能具有挑战性。例如,可压缩物体必须被制造成提供一定的压缩量并且是有弹性的。此外,可压缩物体必须被设计为在一定压力下压缩,以便在井筒内的特定层段中提供体积变化。另外,与可压缩物体结合的钻井液可以被选择,并且可以包括一些与该可压缩物体相互作用的添加剂,以增强可变密度钻井泥浆。照此而言,对选择和制造与钻井液一起使用以形成可变密度钻井泥浆的可压缩物体的方法存在需求。
[0012]在第二可选实施方式中,描述了与钻井相关的方法。该方法包括:选择可压缩物体,其中至少一部分可压缩物体的每一种具有(i)在大气压下为200磅/平方英寸(psi)以上并且(ii)针对预定外压而选择的内压,其中超过内压的外压减小可压缩物体的体积;选择钻井液;向钻井液引入可压缩物体以形成可变密度钻井泥浆,其中当所述可变密度钻井泥浆朝向井的表面循环时,该可变密度钻井泥浆提供位于至少一个井层段的孔隙压力梯度与破裂压力梯度之间的密度;和在井的位置处钻含有可变密度钻井泥浆的井筒。此外,一旦井筒被形成,烃可以从井筒中被生产。
[0015]本技术的上述和其它优势在阅读下面的详细描述以及参考附图后可以变得显而易见,在附图中:
[0017]图2A-2D是按照本技术的方面,可压缩物体的示例性图表和实施方式;
[0018]图3A-3C是按照本技术的方面,处于不同状态的可压缩物体的示例性实施方式;
[0023]图8A-8B是按照本技术一些方面,在图6流程图中所用的制造工艺的示例性实施方式;
[0024]图9是按照本技术的一些方面,在具有泡沫样板的可压缩物体的情况下,在图6流程图中所用的制造工艺的示例性流程图;
[0025]图10是按照本技术的一些方面,从图9流程图中制造的可压缩物体的示例性实施方式;
[0026]图11A-11B是按照本技术的一些方面,在图6流程图中所用的制造工艺的示例性实施方式;
[0027]图12A-12C是按照本技术的一些方面,具有凸缘的可压缩物体的实施方式;和
[0029]在下面详细描述和实施例中,本发明将结合其优选实施方式进行描述。然而,就下面的描述特定于具体实施方式或本发明的具体应用来说,其意图仅仅是示例性的。因此,本发明不限于下面所述的具体实施方式,相反,本发明包括落在所附权利要求书的真实范围中的所有可选物、修改和等价物。
[0031]现转向附图,开始参考图1,图解了按照本技术一些方面的示例性钻井系统100。在示例性钻井系统100中,钻机102被用于钻井104。井104可以穿入地球的地面106到达地下地层108。正如所认识到的,地下地层108可以包括各种岩石层,它们可能包括或不包括烃如油和气,并且可以被称为地带或层段。照此而言,井104可以提供地下地层108与位于地面106处的生产设施(未显示)之间的流体流动路径。生产设施可以加工烃并将烃输送至消费者。然而,应当注意,钻井系统100用于示例性的目的而被图解,并且为了任意目的,本技术可以用于井筒中的任何循环流体,如进行钻井作业或者从地下位置生产流体。
[0032]为进入地下地层108,钻机102可包括钻井组件,诸如底部钻具组合(BHA)110、钻柱112、套管柱114和115、用于处理可变密度钻井泥浆118的钻井液处理单元116以及管理井筒钻井和生产作业的其他系统。这些钻井组件的每一种被用于形成井104的井筒。BHA 110可包括钻头并且可被用于挖掘地层、水泥或来自井筒的其他物质。套管柱114和115可以为到达地下地层108提供支撑和稳定性,其可以包括地面套管柱115和中间或生产套管柱114。生产套管柱114可以向下延伸至地下地层108附近的深度或者向下延伸穿过地下地层108。钻井液处理单元116可以包括可被用于管理可变密度钻井液的器材。例如,钻井液处理单元116可以包括振动筛、分离器、水力旋流器和其他合适的设备(例如,如在2007年2月13日提交的国际专利申请号PCT/US2007/003691中所述)。
[0034]尽管将可压缩物体加至钻井泥浆中以便基于深度控制钻井泥浆的密度已经在Polizzotti等的专利申请公开号WO 2006/007347中予以描述,但是为提供此种功能性而进行的可压缩物体的设计以及钻井液的选择是困难的。具体而言,通过在由现有材料的机械性能所赋予的约束内再循环可变密度钻井泥浆典型经历的反复压缩循环可能是可压缩物体的限制因素。照此而言,制造可压缩物体的过程可能必须包括影响可压缩物体的耐久性和性能的各种因素,如在下面进一步讨论。
[0035]在开始之前,应当注意,大的压缩比是必需的,以在极限内实现钻井液密度随深度的期望变化,该极限是由可压缩物体对流体流变学的影响所允许的可压缩物体的最大体积分数设定的,如在专利申请号WO 2006/007347中所述。因此,可压缩物体应当具有一些性能,该性能适于提供大的压缩比以及在一些压力范围或水平内开始压缩。空心物体的压缩比——其为可压缩物体的一个实施方式——可受到初始未压缩体积(即未压缩或膨胀状态)除以由包括壳壁加上用于实现感兴趣井筒层段中ΔP的壳内压缩气体的体积的物质所占据的体积之比的限制。大的压缩比通过薄且柔韧的可压缩物体的壁来提供。因此,可压缩物体可以优选被设计为使得可压缩物体的压缩和再膨胀可以在没有显著的永久的壁变形(即,导致可压缩物体的壁早期疲劳破坏的永久变形)的情况下完成。
[0037]为了在特定深度压缩,可压缩物体的壁可被设计为保持预定的内压。针对给定钻井泥浆密度的可压缩物体的起始内压由深度决定,在该深度转变为气体压缩由可压缩物体的体积变化控制。通常,可以使用在大气压下为大约200psi(磅/平方英寸)以上、大气压下500psi以上、大气压下1500psi以上或更优选大气压下2000psi以上的内压。对于给定的起始内压,可获得物体的压缩比取决于可压缩物体的壁厚与有效直径之比。尽管壁厚优选尽可能薄,但是壁厚的下限由能够在大约1个大气压的外压——其通常在地面106处遇到的——可含有期望内部气体压力的最小厚度定义。因此,通常可以使用拉伸强度在10,000psi以上的材料,如下面所讨论,以维持可压缩物体的内压。因此,内压可以在大气压下为200psi至壳材料拉伸强度的范围内、在大气压下为2000psi至壳材料拉伸强度的范围内和/或在大气压下为1500psi至3500psi的范围内。
[0038]此外,对于可压缩物体的给定内压和直径,可以使用的最小壁厚因此通过壁材料的拉伸强度的弹性极限来定义。在这些强度极限内,期望最小化壁厚,原因在于壁材料的体积与可压缩物体的总体积之比设定了可获得的可压缩比的大小的上限,如上文所述。因此,尽管可压缩物体可以包括多种形状,例如,诸如立方形、锥形、椭圆形或扁长椭圆体、圆柱形、枕形,但是基于与可压缩泥浆流变学的最优化相关的原因,具有球形或近似球形膨胀几何结构的球形和椭圆物体是有用的。因此,可压缩物体可以包括椭圆形和/或球形物体,诸如纵横比(即大直径与小直径之比)在大约1至5之间的加压空心金属球形和椭圆形物体,以提供可高达5:1或更大的压缩比。
[0039]可压缩物体的设计可以由于结构不稳定性而被进一步复杂化。例如,对于给定内压和直径,球形物体可受到该球形物体构造的结构不稳定特性的限制。结构不稳定性可以包括局部应变,诸如在膨胀阶段的赤道弯曲不稳定性(equatorial buckling instability)以及在压缩阶段的覆盖层弯曲不稳定性(cap buckling instability)。照此,可压缩物体的设计也可以被调整为补偿或减小在可压缩物体的膨胀和压缩过程中的局部应力和不稳定性。因此,球形物体的有限元分析(FEA)模拟——其可以是可压缩物体的一个实施方式——在下面进一步被讨论,如在图2A-2D中所示。
[0040]图2A是可压缩物体的示例性图表和实施方式。在图表200中,可压缩物体是近似球形物体,其具有大约1.0的纵横比和10微米的壁厚。物体的纵横比被定义为长轴与短轴之比,其在下面进一步讨论。
[0041]在图2A中,显示了弹性球形物体的最大应变202对压缩比204的图表200。最大应变202是在该状态下在可压缩物体上的任意点处的最大应变。图表200——产生自FEA模拟工具,诸如ABAQUSTM FEA——包括球形物体在不同状态中的响应曲线206。如通过响应曲线206所示,超过大约12%的线性弹性变形是必需的,以提供至少5:1的压缩比。沿着响应曲线206,最大弹性变形在压缩过程中不会在物体表面上均匀出现,但是由于在压缩过程中的弯曲不稳定性其被局部化。
[0043]基于上述讨论,可压缩物体应当具有足以处理内压的拉伸强度以及足够大以便处理必需变形的可恢复线性伸长或弹性应变。如果球形或近似球形的可压缩物体的壳假定是金属的,则金属或金属合金在其弹性极限内应当具有足够的拉伸强度,以含有内压以及至少12%的可恢复线性伸长。尽管拉伸强度可以被容易地实现,然而很少有金属或金属合金具有超过1%的弹性应变极限。如果期望大于1%的可恢复线性伸长,通常的材料可能是不足够的。对该限制的例外是弹性应变极限接近大约2%的一些无定形金属合金以及形状记忆合金(例如,NiTi合金的Nitol家族),其表现出可高达8%的假弹性应变和小于大约0.1%的永久变形。因此,如果球形结构被用作初始形状时,那么通常的金属或金属合金不能提供至少12%的可恢复线性伸长。
[0044]为提供必需的可恢复线性伸长,可压缩物体可以被设计为将可压缩物体的变形划分为不同的状态。例如,可压缩物体可以具有三个不同的状态,诸如初始状态、膨胀状态和压缩状态。在一个实施方式中,初始状态例如可以是纵横比小于1.0的椭圆形球状体。图2C显示了具有长轴222和短轴224的椭圆形球状物体220。如上所述,物体220的纵横比在初始状态被定义为长轴222与短轴224的比值。在这些状态下,可压缩物体的必需变形被分成两阶段。总的必需变形可以在膨胀状态与压缩状态之间划分。膨胀阶段或第一阶段包括可压缩物体从初始状态膨胀为膨胀状态,其可受限于壁材料的拉伸强度和/或可压缩物体结构初始状态的完全膨胀的可压缩物体特征的结构不稳定性和初始内部压力。
[0046]第二阶段可包括物体从膨胀状态返回至初始状态的压缩,在此过程中,由于初始膨胀引起的变形几乎完全恢复并且随后进一步压缩至完全压缩的状态,其再次受限于完全压缩物体的壁材料的弹性应变。压缩状态例如可以是基于一定的井下深度处施加在可压缩物体上的静水压缩的平衡压缩形状。因此,可以利用这些状态来设计可压缩物体,以提供有益于在井筒内使用的合适的压缩比。
[0047]图3A-3C是根据本技术的方面,处于不同状态的可压缩物体的示例性实施方式。在图3A-3C的实施方式中,FEA模拟被用于展示可压缩物体的不同状态,其在该示例中为椭圆体。这些图3A-3C中的每一个是不同状态的可压缩物体的局部视图。如在图3A中所示,椭圆形物体可以处于初始状态300,并且具有纵横比为4:1的长轴302和短轴304。在图3B中,椭圆形物体可以处于膨胀状态306,并且具有纵横比小于(即图3C中,椭圆形物体可以处于压缩状态312,并且具有长轴314和短轴316以及大于(即》)4:1的纵横比。因此,每一个不同状态300、306和312的纵横比基于椭圆形物体的膨胀和/或压缩可以是不同的。具有不同初始纵横比的可压缩物体在图4中进一步讨论。
[0048]图4是根据本技术的方面,不同初始形状的可压缩物体的示例性图表。FEA模拟被用于产生壁厚为15微米的不同可压缩物体的最大应变402对压缩比404的图表400。图表400包括球形物体的第一响应曲线406、纵横比为2:1的椭圆形物体的第二响应曲线407、纵横比为3:1的椭圆形物体的第三响应曲线408、纵横比为4:1的椭圆形物体的第四响应曲线409,它们可以是图3A-3C中的椭圆形物体,以及纵横比为5:1的椭圆形物体的第五响应曲线410。
[0049]如通过响应曲线406-410所示,最大应变在不同状态之间增加和减小。对于初始纵横比小于3:1的物体,压缩比小于3:1的最大线性弹性应变行为受上述覆盖层弯曲不稳定性的控制。对于初始纵横比大于3:1的可压缩物体,最大应变从膨胀状态降低至在初始状态或初始状态附近的最小值,其是可压缩物体上的应变的全局最小值。然后,最大应变从初始状态增加,直至达到完全压缩的状态。照此,可压缩物体初始状态的最大应变接近零,如通过响应曲线406-410所示。该方面清楚地由第四响应曲线409显示。沿着响应曲线409,膨胀状态位于点416处,初始状态位于点414处,以及压缩状态位于点412处。明显地,可压缩物体的初始状态相比膨胀和压缩状态具有最小应变。另外,该可压缩物体具有大约0.085的最大应变,其约为合金的Nitol家族在其假弹性状态从奥氏体到马氏体相变的最大可恢复应变的值。也就是说,响应曲线409显示,具有4:1的初始纵横比的椭圆形物体是提供大于5:1的规定压缩比的合适的结构和壁厚,且其内压用于在国际专利申请公布号WO 2006/007347中所公开的发明实践。其他响应曲线406-408和410中的每一种均超过0.085的最大可恢复应变。高于奥氏体向马氏体相变完成应变大约8%的应变可经历导致在循环变形中有限的疲劳寿命的永久变形。
[0050]根据该图表400,可压缩物体的膨胀以及随后的压缩受限于膨胀阶段中的赤道弯曲不稳定性和先前所述的压缩阶段的覆盖物弯曲不稳定性。通过模拟膨胀以及随后的压缩,可压缩物体的初始结构可以被设计成最小化针对特定压缩比的可恢复伸长。具体而言,对于用自奥氏体对马氏体相变温度在大约0°C(摄氏度)以下的NiTi形状记忆合金制造的具恒定壁厚的可压缩物体并且目标膨胀内压为1500psig(磅/英寸2规格)而言,该可压缩物体的初始纵横比在膨胀之前可以优选在大约3与4之间且壁厚在大约15与20微米之间,以避免对于可高达8:1的压缩比而言在可压缩物体壁内的任何位置超过大约8%的线性伸长。如上所述,为用于专利申请号WO 2006/007347的实践,合金应当处于假弹性状态。相变温度在大约0°C以上的常规形状记忆合金不被用于此应用。对奥氏体向马氏体相变温度在大约0°C之下的要求承认了,可压缩物体在钻井泥浆中作业过程中所遇到的整个温度范围内合金应当保持假弹性。
[0051]基于上面所讨论的模拟方法,可压缩物体可以通过一定的材料而设计并且具有特定的结构,以提供在现有材料的变形极限内的特定压缩比。伴随这些压缩比,可压缩物体可以用于某些应用中,诸如在上面描述的钻井作业和生产作业。作为示例,如果可压缩物体在感兴趣的特定井深间隔下提供大于或等于5倍于膨胀状态的可恢复压缩比,则该可压缩物体是有用的。在可变密度钻井泥浆中可包括高达40%或50%的体积分数的可压缩物体,以提供代表典型的PPG和/或FG的钻井泥浆密度的改变。通过添加高达50%按体积计的小的低密度可压缩物体——其可具有大约1毫米(mm)的直径——来改变钻井泥浆的密度,井筒内的压力梯度可以基本被控制,以减少在井筒中所利用的套管柱的数目。具体而言,对于深水应用,在没有对现有硬件或设备进行主要修改的情况下,套管层段的数目可以被基本减少到利用双梯度或多梯度系统可获得的数目之下。照此,对于某些应用,井成本可以被降低达30%至50%。因此,可压缩物体的选择以及可压缩物体的制造在下面图5中进一步讨论。
[0052]图5是按照本技术一些方面,选择和应用用于图1钻井系统100的可变密度钻井泥浆的示例性流程图。该流程图,被称为参考数字500,可以通过同时参考图1、3A-3C和4而得到最好的理解。在流程图500中,可以选择可压缩物体和钻井液,以配制井的可变密度钻井泥浆。这些可压缩物体可以包括每个均具有封闭内部区域的壳的物体,其中所述可压缩物体具有:(a)内压,所述内压:(i)在大气压下为大约200磅/平方英寸(psi)以上、大气压下为500psi以上、大气压下为1500psi以上和/或大气压下为2000psi以上,并且(ii)针对预定外压而选择,其中超过内压的外压减小可压缩物体的体积;(b)其中,当外压大约等于内压时,所述壳经受的应变小于当所述外压高于或低于可压缩物体的预定压缩层段时的应变,或者其中所述壳被设置为当外压大约等于内压时所经受的应变小于外压大于内压或小于内压时的应变;和/或(c)可压缩物体具有壳,该壳封闭至少部分填充有泡沫的内部区域。然后,可变密度钻井泥浆可被用于提高井的钻井作业。该过程可以通过提供可变密度钻井泥浆来提高钻井作业,所述可变密度钻井泥浆可以延伸钻井作业而进一步限制或减少附加套管柱的安装。因此,以期望方式进行的钻井作业可降低钻井作业中利用附加套管柱的无效率。
[0053]流程图始于块502。在块504,可以确定井的FG和PPG。例如,可以通过从钻井位置接受信息和/或进行计算以估计FG和PPG来获得FG和PPG。然后,可以选择可压缩物体,以提供特定的体积变化,如在块506所示。可压缩物体的选择可以包括作业考虑因素,诸如从钻井泥浆中移除可压缩物体以用于在地面再循环、限制高体积分数的可压缩物体对钻井泥浆流变学的潜在有害影响以及促进可压缩物体经过流动路径中的泵和孔的流动。照此,可压缩物体可以被定制大小,以具有介于0.1毫米(mm)与50mm之间且/或优选介于0.1mm与5.0mm之间的当量直径。当量直径被定义为与大气压下完全膨胀的可压缩物体体积相同的球的直径。此外,可压缩物体的选择可以包括在井筒的表面利用不同大小或体积和/或不同形状的可压缩物体,以管理钻井泥浆的粘度增加。可压缩物体的选择在图6被进一步描述。
[0054]在块508,可以选择钻井液。可以选择可以包括各种加重剂的钻井液,以提供可以与可压缩物体相互作用以维持钻井泥浆密度在FG与PPG之间的特定密度,其在下面被进一步讨论。在块510中可压缩物体和钻井液可以结合。可压缩物体和钻井液的结合可以包括混合或掺和可压缩物体和钻井液,如在2007年2月13日提交的国际专利申请号PCT/US2007/003691中所述。此外,可压缩物体和钻井液可以在运输至钻井位置之前被结合,或者可压缩物体和钻井液可以被单独运输且可压缩物体和钻井液在钻井位置处被结合。应当注意,可压缩物体可以在冷冻交通工具诸如卡车和船中被输送,以降低与可压缩物体内的内部压力释放相关的危险。
[0056]图6是按照本技术的一些方面,在图5的流程图中讨论的可压缩物体的选择和制造的示例性流程图。该流程图,其被称为参考数字600,可以通过同时查看图1、3A-3C、4和5而被最佳理解。在该流程图600中,描述了选择可压缩物体以维持井内的钻井泥浆密度处于PPG与FG之间的过程。有益地,可压缩物体在可变密度钻井泥浆中的应用可以通过减少井筒和套管柱的大小来提高钻井作业,并且可以提供到达更大深度的通道。
[0057]流程图始于块602。在块604,获得井的FG和PPG。可以通过从钻井位置接受信息和/或进行计算以估计FG和PPG来获得FG和PPG。然后,选择每一种可压缩物体的结构,如在块606中所示。对可压缩物体结构的选择可以包括利用有限元分析(FEA)方法,以使可压缩物体的结构和几何形状与可获得材料的性质匹配,如上所述。在块608,选择可压缩物体的壁材料。壁材料的选择可以包括通过机械或通过沉积方法形成的金属和/或金属合金薄膜、在聚合物基体中具有或不具有微观和/或纳米纤维增强的聚合物以实现特定的壁材料性质(例如,如通过物体压缩的FEA分析所定义的)。另外,壁材料可以包括页状剥落无机矿物质以作为在聚合物基体中的增强或者防透气的屏障;通过沉积方法在聚合物表面上形成的金属和/或金属合金薄膜,其具有或不具有聚合物表面的化学改性以形成结构性壁或防透气的屏障。金属和/或金属合金薄膜可以在形成可压缩物体之前被沉积在聚合物片上或者可以被沉积在预成型的可压缩聚合物物体上。金属层可以被形成在可压缩物体的内部或外部表面上,或者被引入聚合物壁内或者相同或不同聚合物的聚合物层压制品内。
[0058]在块610,可以选择表面处理,用于制造可压缩物体。表面处理可以包括物理和/或化学表面处理,以改善聚合物物体表面上的金属和/或金属合金膜的连续性和粘合性,或者增强可压缩物体的聚合物的或金属外壁与钻井液的化学和/或物理相容性。
[0060]在块614,可以验证或测试可压缩物体。验证和测试可以包括循环压缩测试,以验证内压以及量化可压缩物体的疲劳寿命,且如果存在任何结构壁和连接的话,可伴随或者不存在对结构壁和连接的微结构分析。然后,可以贮存可压缩物体,如在块616所示。可压缩物体的贮存可以包括将可压缩物体放置在贮存容器中。可压缩物体可以被贮存在环境压力下或者等于或高于可压缩物体的内压的压力下,以便于可压缩物体在贮容器中填塞。可选地,可压缩物体可以被贮存在冷环境中以降低可压缩物体内的内压。冷的可压缩物体然后可以在环境压力下或者在升高的压力下被贮存在容器中,以便于可压缩物体在贮存容器中填塞以及将可压缩物体运输至另一位置,诸如钻井位置,以便贮存或其他类似活动。该过程结束于块618。
[0061]因此,基于上述讨论,这些可压缩物体的选择和应用可以涉及影响可压缩物体设计的不同方面。例如,转变为气体压缩控制的变形的本质取决于壳或壁材料的机械性能以及在反复压缩循环中这些性能的发展。照此,空心物体的压缩导致在由空心物体的初始内压所定义的深度之上和之下产生泥浆密度梯度差。因为使用具有不同初始内压的可压缩物体可以有益于增强或延伸钻井作业,因此改变可压缩物体的体积分数和初始压力分布可以实现将有效的泥浆重量维持在PPG与FG之间的理想结果。
[0064]为确定可压缩物体的构造,如在图6的块606中所述,可以利用有限元数值模拟方法。有限元数值模拟法可以包括隐式方法和/或显式方法。在这些方法中,壳壁或元件可以被表示成在感兴趣区域内适合较高分辨率的网格尺寸和形状,诸如在可压缩物体结构的高应力和/或应变区域内。有限元数值模拟可以被用于模拟整个三维物体或与对称的三维物体相关的物体片段。此外,可压缩物体的构造可以受多种标准的影响,诸如材料和可压缩物体的使用,它们将在本申请的该部分和其他部分被讨论。
[0069]作为具体示例,讨论图3A-3C的可压缩物体的有限元数值模型。在这些实施方式中,可压缩物体具有扁平椭圆体的形状。初始纵横比可以在1至10的范围内,更优选的纵横比在2至5的范围内。使用初始纵横比大于1的内部加压的扁平椭圆体空心可压缩物体具有如下优势:在外界外部地面压力下,该椭圆体物体取决于内压和材料性质而膨胀并达到大约1的纵横比,如图3B所示。如果该椭圆体物体具有4:1的初始纵横比、10微米的均匀的NiTi合金壁厚以及1500psig的内压,那么膨胀状态的纵横比大约为1.22:1。随着外压力增加,椭圆体物体倾向于恢复至初始状态300。在初始状态300,该椭圆体物体的纵横比是具有很小弹性应变的最初设计的纵横比,如在图3A和4所示。然后,随着压力继续增加,该椭圆体物体被进一步压缩成压缩状态312,如在图3C中所示。
[0070]除构造之外,基于上面讨论的标准,可压缩物体的壁可以使用各种材料,如在图6的块608中所述。具体而言,壳或壁材料可以被分为两类商业可得的材料,其为金属材料和聚合物材料。金属材料可以包括金属、金属合金和具有假弹性行为的合金(例如与可逆应力诱导的结构相变有关的变形)。此外,超薄(即,<500埃(A))金属或金属合金膜的超弹性行为也可以被用于使金属和金属合金(例如,铝(Al)、铜(Cu)、镍钛(NiTi)等)的范围更广,它们与满足承载壁的机械性能的非金属承载壁结合以适合作为薄渗透屏障应用。具体而言,金属材料可以包括但不限于:二元或近二元NiTi、具有铁和铬合金添加物的NiTi的三元合金、镁-40铜(Mg-40Cu)合金、β-钛-9.8钼-4铌-2钒-3铝(β-Ti-9.8Mo-4Nb-2V-3Al)合金、金属玻璃和非晶态金属(例如锆(Zr)、铁(Fe)和/或镁(Mg)基合金)等。聚合材料可以包括聚合物以及具有或不具有增强物(例如,微纤维至纳米纤维,纳米管,在聚合物壁内具有适当定向的页状剥落型无机填料等)的共混聚合物。具有适当性质的聚合物的示例包括但不限于商业可得的聚酰亚胺,诸如Ubilex-R和Ubilex-S。
[0071]因为这些材料中的每一种均具有特定的性质,诸如拉伸强度和可恢复伸长,因此在可压缩物体壁中所用的材料是决定壁厚的因素。该决定可以基于如上所述的有限元数值模拟,以评价具有不同材料的壳或壁的不同厚度。例如,如果承载壁材料是金属或金属合金,则应该仅仅选择具有足够高的弹性或假弹性行为的金属和金属合金,原因在于与可逆应力诱导的结构相变有关的变形必须是可恢复的,以便可压缩物体的再使用。如上所述,甚至这些选择的材料必须与可压缩物体外壳的几何形状的谨慎设计相结合,以避免在压缩和再膨胀过程中的应变局部化。具体而言,几何形状和材料可以被用于相对于颗粒尺寸来最优化壁厚;随可压缩物体表面上的位置承载壁厚和/或机械性能的变化;和/或扁平球状体空心可压缩物体的纵横比和大直径的变化等。因此,在选择可压缩物体的材料时应考虑这些不同的因素。
[0072]作为改变壁厚的示例,壁材料可以被用于影响可压缩物体的压缩比,诸如上面讨论的在图3A-3C中的椭圆体物体。在图7中,FEA计算提供了在由现有材料性质定义的极限内具有不同压缩比的不同形状。FEA计算可以提供纵横比在2与5之间、当量直径与壁厚比在20与200之间或更优选在50与100之间的可压缩物体。如在图7中所示,显示了壁厚影响的图表700,其是关于不同形状——其通过曲线706-711显示,产生自有限元数值模拟——的可压缩物体的最大应变702对当量直径与壁厚比704。对于球形可压缩物体,曲线706的压缩比为3.5,曲线707的压缩比为3,以及曲线708的压缩比为2。对于椭圆形可压缩物体,曲线709的压缩比在3.5与2之间,曲线710的压缩比在3与2之间,以及曲线711的压缩比大约为2。从图表700,清楚的是,具有大于与在较薄的壁(即,较高的当量直径与壁厚比)的情况下的纵横比一致的纵横比的可压缩物体是优选的,原因在于它们提供较高压缩比和相应地较低最大应变。此外,优选的是,维持最大应变在大约0.06的特定值之下,该值是由实现适当的结构壁疲劳寿命的最大允许应变定义的。通常,至少2000至3000周期的最小疲劳寿命是期望的。基于该限定,纵横比为2或以上以及当量直径与壁厚比大于65的椭圆体物体提供了在特定值之下的可压缩物体,如在曲线711上所示。
[0074]如在图6的块610中所讨论,各种表面处理可以被用于可压缩物体。表面处理可以被用于改进聚合物层或金属和/或金属合金膜在可压缩物体(诸如聚合物物体)上的连续性和粘合性。因此,表面处理可被用于增强特定性能,诸如与基液的相容性以及维持内压的壳层渗透性,这在下面进一步讨论。
[0075]对于内部加压的可压缩物体,其具有带有或没有增强物的聚合物和/或弹性体的承载壁,表面处理可被用于增强金属和/或非金属膜在聚合物表面上的连续性以降低承载壁的气体渗透性。一般而言,弹性体、结晶聚合物和/或共混聚合物具有的气体渗透性太大以至不能用于可压缩物体的制造。因此,除在聚合物壁中引入页状剥落型无机填料之外,可以采用将连续的薄的(即,<500埃)低气体渗透涂层沉积在壁表面上或者将其引入层状壁结构中。例如,该涂层可以是薄金属、金属合金或无机气体渗透屏障,其可以通过多种物理和/或化学处理被应用于可压缩物体的表面壁的外部。具体而言,沉积涂层的厚度可以小于500A并包括Al、NiTi或任何其他合适的材料。增强这些渗透降低层的均匀性和/或连续性的表面处理可以包括:(1)表面的阴离子官能化,例如,磺化、羧化(即酸形成)以及由本领域技术人员使用的其他阴离子官能化方法和化学。(2)阳离子季铵化官能化化学,例如本领域技术人员所使用的锍盐、磷盐、铵盐。(3)本领域技术人员实践的两性离子官能度和两性官能度。(4)本领域技术人员已知的马来化官能化和相关反应。(5)控制的氧化,例如过氧化物、高温氧等离子体蚀刻、臭氧等。(6)化学气相沉积方法和相关的化学。(7)本领域技术人员所使用的进行表面官能化的电晕放电方法。
[0076]很多种方法可用于沉积金属和/或无机屏障涂层。可影响沉积方法选择的一个因素是可压缩物体的内压。例如,如果在可压缩物体内含有少量初始内部气体压力或无初始内部气体压力,则低渗透性金属、金属合金或无机涂层可以通过各种低压物理和化学沉积方法被用于均匀地涂敷可压缩物体的非平面几何结构。如果可压缩物体的内压和壁渗透性使得低压物理或化学沉积所需的低压环境(即,典型地-3mmHg)是不可维持的,则可以使用与内部气体压力和相对高的壁气体渗透性相容的沉积方法。在该示例中,可压缩物体可以被维持在高压气体或液体环境中,以防止在贮存和涂敷期间内压通过可压缩物体的壁损失。对于高压液体环境,壁表面的涂层可以通过例如利用本领域技术人员熟悉的方法进行的电镀或无电喷镀来实施。对于高压气体环境,壁表面的涂层可以通过例如化学气相沉积(CVD)或紫外线化学气相沉积(UV-CVD)来实施。
[0077]可选地,可压缩物体内的内部气体压力可以被降低至允许在未加压物体或聚合物片中应用一系列可用的商业低压物理和化学沉积方法的水平。在该示例中,通过降低可压缩物体的温度可以被冷凝的气体可以被用于可压缩物体的内部增压。例如,如果可压缩物体内部的气体是在10mpa压力下的氧(O),随后在大气压下冷却该可压缩物体至液氮(LN2)的温度,可将内压降低至小于或等于1 x 10-3mm Hg。
[0078]关于空心聚合物承载壁的类似的考虑因素可以被应用于内部加压的可压缩物体,该可压缩物体具有聚合物和/或弹性体泡沫的承载壁以及金属和/或非金属渗透屏障的气体屏障壁,或者上述考虑因素可以被应用于聚合物和/或弹性体超薄空心壳或者被用作承载金属和/或金属合金壁沉积模板的聚合物和/或弹性体泡沫,如上所述。在后面的示例中,超薄聚合物壳或聚合物泡沫可被用作沉积相对厚的金属和/或金属合金承载壁的模板。在该示例中的金属或金属合金承载壁可具有大约5微米至50微米的厚度。超薄聚合物壳或聚合物泡沫可包括任何聚合物和/或弹性体,其具有或者无增强物以及表面处理以提高金属和/或金属合金承载壁的均匀性和连续性。在该示例中,超薄聚合物壳的厚度和/或泡沫的机械强度仅需要在沉积过程中足以维持颗粒的期望形状。
[0079]如在图6块612中所讨论,一旦选择了可压缩物体的结构和壁材料,各种制造技术可被用于产生可压缩物体。这些制造技术可以包括各种方法,诸如图形形成、沉积、热-机械加工和其他类似的制造工艺。图形形成工艺是将材料成形为诸如可压缩物体的另一形态的工艺,其可以包括化学蚀刻、机械蚀刻等。蚀刻工艺是从基底材料上去除材料的工艺。沉积工艺是将材料涂敷或转移到另一种材料上的工艺,其可以包括物理气相沉积、化学气相沉积、电化学和/或无电沉积、合金化、溅射、蒸发、分子束外延等。热-机械工艺是形成或改变材料形状和微观结构的工艺,其包括冷轧、热轧、型锻、拉拔、切割、回火、溶液退火等。
[0081]因此,制造工艺可以被设置为产生这样的可压缩物体,其是气体填充的聚合物物体,包括是空心或者至少部分填充泡沫的内部结构。例如,图8A-8B是产生具有空心内部的可压缩物体的制造工艺的示例性实施方式。类似地,图9、10和11A-11B是产生具有泡沫内部或基于泡沫模板的可压缩物体的制造工艺的实施方式。
[0082]下面所述的制造方法涉及作为空心物体被形成的可压缩物体的制造,该空心物体可以填充气体或可以不填充气体。这些制造方法可以被用于形成可压缩物体,其均具有封闭内部区域的壳,每一个可压缩物体均具有(a)内压,该内压(i)在大气压下为大约200psi以上、大气压下为大约500psi以上、大气压下为大约1500psi以上或大气压下为大约2000psi以上,和/或具有封闭内部区域的壳,和该内压(ii)针对预定外压而被选择,其中超过内压的外压减小可压缩物体的体积;(b)所述壳被设置为当外压大约等于内压时所经受的应变小于外压大于内压或小于内压时的应变,或者当外压大约等于内压时所述壳经受的应变小于当所述外压高于或低于可压缩物体的预定压缩层段时的应变;和/或(c)所述壳至少部分填充有泡沫。尽管描述了很多制造方法,图8A-8B是产生具有空心内部的可压缩物体的示例性实施方式。
[0083]图8A-8B是按照本技术的某些方面,在图6的流程图中所用制造过程的示例性实施方式。在图8A中,显示了按照本技术产生可压缩物体的装置的示例性实施方式。在该实施方式800中,诸如空心聚合物壳或聚合物泡沫结构的可压缩物体,可以在由加压室802形成的加压环境中制造。为了示例性的目的,可压缩物体显示为具有气体内部806的空心聚合物壳804,但是可以包括聚合物泡沫结构和上述其他可压缩物体。
[0085]此外,在空心聚合物壳804聚合和/或分离过程中或之后,围绕该空心聚合物壳804的压力可以被降低以使空心聚合物壳804膨胀成其在膨胀状态的最终大小和形状。在壁冷却之前、期间或之后,该膨胀状态可以由壁厚、材料的机械性能、物体构造和内压预先确定。如果聚合物壁是承载部件,合成之后直径的膨胀可被用于改变聚合物壁的机械性能。例如,通过聚合物链的应变再定位和/或空心聚合物壳804聚合物壁中增强物的再定位。
[0086]基于所用的材料可以针对制造过程引入特定的调节。例如,如果聚合物材料814是具有或不具有增强物的聚合物熔体,则孔808可以被加热以降低熔体粘度而获得期望的聚合物熔体流动性能。此外,如果聚合物材料814是具有或不具有增强物以及具有或不具有引发剂的聚合物单体或单体混合物,则聚合物泡820的壁在与孔808分离之后的聚合可以通过多种方法进行,诸如紫外线聚合、自由基聚合、热化学聚合等,这些是聚合物合成领域技术人员熟悉的。
[0087]在图8B中,显示了按照本技术产生可压缩物体的装置的另一示例性实施方式830。在该实施方式830中,例如空心聚合物壳或聚合物泡沫结构的可压缩物体可以在由加压室832形成的加压环境中被制造。该加压室832被分成具有气体入口840的下部室838以及具有流体入口844和流体出口846的上部室842。为了示例性的目的,可压缩物体显示为具有气体内部836的空心聚合物壳834,但是可以包括聚合物泡沫结构和上述其他可压缩物体。
[0088]在该制造过程示例中,合适的聚合物熔体或聚合物前体的薄膜848在由大量孔或空穴852穿孔的板850上形成。可以安排空穴852的尺寸和间隔以使气体填充的泡854连续形成,该气体填充的泡854具有含气体内部836的空心聚合物壳834,并且当板850在上部室842与下部室838之间的期望压差下从下面被加压时,这些泡854分离并浮在板850上,并进入填充上部室842的加压流体中。应当注意,很多可选的空穴几何性质可以被用于从聚合物前体和/或聚合物熔体形成内部加压的空心可压缩物体。气体填充的泡可以通过流体出口846离开上部室842,并且可以通过密度差与流体分离并随后被转移至贮存容器。
[0089]作为产生可压缩物体的可选示例性方法,金属、金属合金和/或聚合物管可以被用于形成可压缩物体。在该制造方法中,通过将管材料切割成期望的长度并利用机械、化学或热方法将该管材料的端部封闭,可使压缩物体由管材料形成。得到的可压缩物体(其可以以枕形、球形、扁球面、回转的椭圆体或任何其他期望的形状形成)的内部压力可以通过闭合管的切割端部并在控制压力的环境中形成期望的形状来进行控制。加压环境可以是加压室,其类似于上面所讨论的加压室。另外,可压缩物体可以在来自具有或不具有加强物的聚合物和/或弹性体的管材料的聚合物壁合金化之前或之后形成。
[0090]作为产生可压缩物体的另一可选实例方法,预成型片可以被用于形成可压缩物体。在该方法中,预成型片的机械、热或化学连接可以被用于制造可压缩物体。预成型片可以包括层状复合结构,其可以包括两个实施方式。一个实施方式可以是相对厚的结构承载聚合物壁与相对薄的连续金属、金属合金和/或非金属渗透屏障层相结合。具体而言,结构承载聚合物壁可以具有大约5微米与50微米之间的壁厚,尽管连续的金属或金属合金渗透屏障层可以具有小于约500埃的壁厚。第二实施方式是薄聚合物片作为沉积相对厚的金属或金属合金层的模板,该金属或金属合金层用作结构壁和气体渗透的屏障。例如,薄聚合物片可以小于大约5微米,而金属或金属合金层可以具有大约5微米与50微米之间的壁厚。聚合物厚度和金属或金属合金厚度位于这些限制内的层状或多重层状实施方式的任何组合可以用于其他实施方式。
[0093]作为另外的制造技术,上述复合片制造方法也可以被用于制造自支撑的相对厚的金属和金属合金片,其适合机械形成可压缩或可折叠物体或颗粒的组件。当薄金属片难于通过金属片制造中所用的常规热-机械方法制造时,制造自支撑金属或金属合金片的此种方法特别有用。具体而言,金属和金属合金片可以具有大约5微米与50微米之间的厚度。为形成自支撑金属片,在金属或金属合金沉积之后,在固化该沉积薄片所需的任何另外的热-机械处理之前或之后,聚合物模板可以从薄金属片上移除。聚合物模板的移除可以通过本领域技术人员已知的多种机械、化学和/或热方法来完成。可选地,在金属或金属合金薄膜沉积而形成自支撑金属或金属合金预成型物之前,聚合物模板片可以在可压缩物体的组件中预成型。
[0094]作为另一制造技术,空心可压缩物体可以通过热固性聚合物的化学组分的物理和/或化学气相沉积(如上所述)而形成到热解聚空心聚合物模板或聚合物泡沫上。沉积之后,通过升高温度而在解聚空心聚合物壳或聚合物泡沫模板的表面上形成自支撑的热固性聚合物预成型层,从而热固性聚合物组分可以部分反应在一起。在形成自支撑的热固性聚合物预成型层之后,温度可以被进一步增加以解聚空心和/或泡沫模板,并且解聚产物通过经过热固性预成型壁的扩散而从所得到的空心自支撑物上去除。最后,部分固化的自支撑空心预成型热固性物体可以被放置到高压容器中,并且借助在该容器内建立的高气体压力,空心物体内部的压力通过扩散穿过热固性预成型壁得以平衡。随后,温度可以在高压气体环境中被进一步升高,以充分固化热固性聚合物,目的是降低壁的透气性以及获得最佳的壁材料机械性能。如之前,充分固化和加压的空心热固性聚合物壳的外表面的合金化可以通过上面关于同轴吹制的加压空心聚合物壳所述的方法来完成。
[0095]此外,作为另一实施方式,可压缩物体可以在制造过程中进行机械调节,以强化可压缩物体的结构壁,这通过由机械应力引起的微纤维和/或纳米纤维加强物和/或包括壁材料的聚合物链的再定位而实施。这种机械调节可以包括但不限于可压缩物体膨胀成其最终尺寸和形状。
[0098]作为第一实施方式,起泡剂可以被用于形成可压缩物体的泡沫模板。通常,使用物理起泡剂产生闭孔泡沫模板,其可以由各种材料形成。例如,聚氨酯(PU)、聚苯乙烯(PS)和聚氯乙烯(PVC)是制造聚合物泡沫时所用的材料。通常,PU泡沫由二氧化碳(CO2)的原位产生来制备,而PS和PVC泡沫利用物理起泡剂(像氮(N2)和CO2)来制备。利用物理起泡剂减少了任何污染溶剂阻碍该过程。利用CO2和N2具有很多益处,诸如化学惰性、不可燃性、天然发生、低成本、易于得到、环境可接受性(无臭氧消耗)以及低人类毒性。
[0099]使用物理起泡剂的每一种聚合物泡沫状技术依赖于类似的原则。这些原则是(1)在高压下聚合物借助气态渗透剂(起泡剂)饱和;(2)通过降低的压力或增加的温度,聚合物/气体混合物淬熄进入过饱和阶段;和(3)遍及聚合物基体分散的气体泡孔的核化及生长。在聚合物/气体混合物淬熄之后,气体在聚合物模板中的溶解度减小,这导致气体分子以晶核形式聚集。随着气体扩散进入所形成的泡孔中,聚合物模板的自由能降低。泡核作用过程控制着聚合物材料的泡孔形态以及聚合物材料的性质。此外,该过程可以遍及整个材料均匀发生,或者在高能区诸如相界处不均匀发生。在高能区,核化稳定空隙的自由能相比均匀成核较小。结果是,优选的空隙成核在界面处发生。
[00100]在半结晶聚合物中,结晶域可以作为产生气泡的异相成核点。一般而言,泡孔生长(cell growth)受气体在淬熄之前必须扩散进入泡孔的时间、制造过程的温度、过饱和的程度、气体扩散进入孔泡的速率、施加于聚合物基体的静压或应力、界面能以及聚合物/气体混合物的粘弹性。聚合物模板的硬度通常由起泡温度来控制。应当注意平均孔泡大小的减小通常增加硬度。膨胀气体孔泡所需的功必须克服由增加的硬度所产生的额外应力。通过增加饱和压力,用于形成稳定晶核的自由能屏障被减小,并且由于基体溶胀、空隙容积改变和/或结晶界面的形成,形成另外的成核点。这导致泡孔密度增加并因此导致平均泡孔直径减小。半结晶聚合物表现出比非晶态聚合物更高的泡孔(cell)密度,这归因于在非晶态/结晶界面区处的异相成核分布。因为气体不溶解在晶体中,因此成核是不均匀的,这使得难于控制半结晶泡沫的微孔结构。结果是,具有低结晶度的聚合物提供了具有几乎均匀的结构的泡沫。随着聚合物的结晶度增加,得到具有不规则泡孔大小的较不期望的不均匀泡沫。
[00106]此外,应当注意,表面处理可以针对不同的泡沫模板进行调整。例如,如果聚苯乙烯是泡沫模板,其是高度非极性且化学活性的聚合物。功能化即磺化的程度可以通过很多参数来控制,诸如:溶剂、硫酸浓度、反应温度、反应时间、催化剂和催化剂浓度。照此,应当注意,表面功能化化学以及随后的过程可以被修改以适应材料诸如尼龙、聚酯、聚氨酯以及其他聚合物材料的表面化学和结构。表面功能化和蚀刻可以包括酸处理、碱处理、氧化、硝化、磺化、磷酸化以及其他化学处理。参见J.March,"Advanced Organic Chemistry:Reactions,Mechanisms,and Structure",Third Ed.,John Wiley & Sons,New York(1985),涉及磺化、温和氧化、酯化、羧化、自由基加成反应、自由基图案反应(free radical graphing reaction)和季铵化以及类似反应的章节。
[00107]作为第一具体示例,泡沫模板可以通过诸如化学镀铜的方法进行均匀涂敷以形成棒状泡沫物体。泡沫模板可以是填充空气的泡沫微胶囊,其具有直径为大约1000μm(微米)至1500μm的泡孔。如果该泡沫模板是聚苯乙烯,则制造方法可以包括通过暴露于H2SO4的30%溶液21小时期间而进行的聚苯乙烯棒的功能化。功能化聚合物的表面可以利用锡-钯(Sn-Pd)活化工艺——另外被称为加晶种——进行活化。该加晶种方法是本领域那些技术人员熟悉的。该工艺包括将聚苯乙烯棒连续浸入酸性氯化锡(SnCI2)(0.01M)中,之后浸入酸性氯化钯(PdCl2)(0.01M)溶液中,并在两浴之间用蒸馏水漂洗。在PdCl2之后使用0.01M氯化氢(HCl),以从表面去除剩余的Sn化合物。每一种浴都在室温下进行。参见B.Ceylan Akis,"Preparation of Pd-Ag/PSS CompositeMembranes for Hydrogen Separations",A Thesis,Worcester PolytechnicInstitute,(2004年5月)。功能化的、Pd接种的聚苯乙烯棒可以被放置在流速为73cc/min(立方厘米/分钟)、含有CuSO4·5H2O的铜(Cu)电镀溶液、二水乙二胺四乙酸二钠(ethylenediaminetetraacetic acid disodiumsalt dihydrate)、NaOH、乙二胺和三乙醇胺的用甲酸活化的浴中。参见Y.Lin and S.Yen,Applied Surface Science,178,116(2001);W.Lin,H.Chang,Surface and Coatings Technology,107,48(1998);Shu et.al.,Ind.Eng.Chem.Res.36,1632(1997);Hanna et al.Materials Letters,58,104(2003)。Cu可以在40°C下90分钟内被电镀到功能化的、Pd接种的聚苯乙烯棒上,之后用蒸馏水洗涤。大部分表面可以用Cu涂敷,其厚度在0.3-0.6μm的范围内。
[00108]可选地,如果泡沫模板是空气填充的泡沫微胶囊,该泡沫微胶囊具有直径大约250μm至500μm泡孔以及球形形状,那么制造方法可以包括聚苯乙烯球的功能化和Pd加晶种,如上所述。利用同样的Cu电镀溶液以及流速,功能化的Pd接种的聚苯乙烯球可以在40°C被电镀10分钟,之后进行蒸馏水洗涤。结果是,表面可以涂敷有覆盖沿泡沫表面轮廓的0.1-0.2μm厚的Cu膜。
[00110]作为另一示例性制造技术,空心的气体填充的金属壳可以利用用于生产空心金属物体的Fraunhofer方法来制造,如在图11A中所示。参见例如O.Andersen,U.Waag,L.Schneider,G.Stephani,B.Kieback,"Novel Metallic Hollow Sphere Structures",Advanced EngineeringMaterials 2000,vol 2,(2000年4月),pp.192-195。在该实施方式1100中,泡沫模板1102(可以是Styrofoam模板或者上述任意聚合物泡沫模板)可以用金属材料1104涂敷,该金属材料1104可以包括金属或金属合金粉以及粘结剂。泡沫模板1102的金属材料和粘结剂1104的涂层可以在容器1106中通过流化床涂敷方法来完成。涂敷有金属或金属合金粉和粘结剂层1108所得到的聚合物泡沫模板可以经历熔炉1110进行退火。在该熔炉中,聚合物泡沫模板可以进行热分解或者反应成挥发性反应产物,其可以通过扩散经过部分烧结的金属或金属合金壁而被去除。随后,温度可以被升高以除去剩余的粘结剂,并且金属材料被烧结以获得密集的金属或金属合金壳。得到的可压缩物体1112可以在冷却后被用作可变密度钻井泥浆的一部分。
[00124]尽管本发明的技术可以容易地进行修改和可选形式,然而上面讨论的示例性实施方式已经通过实例的方式显示。然而,再次应当理解,本发明部意图限于在此所公开的具体实施方式。的确,本发明的技术意欲覆盖落在如由所附权利要求书定义的本发明精神和范围之内的所有修改、等价物和可选物。