Patent Publication Number: US-11655687-B2

Title: Modular additive cementing

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims the benefit of priority to U.S. Provisional Application Ser. No. 63/104,962, filed Oct. 23, 2020, the contents of which are hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to downhole cementing. 
     BACKGROUND 
     A cement retainer is a tool that is set in a tubing and allows cement or other fluids to be pumped through the tool but seals against any fluid movement when the tubing is released from the tool. Cement retainers typically include slips, a ported mandrel, and rubber sealing elements, and they are typically used in squeeze cementing work. Cement retainers can be mechanically set, hydraulically set, or set via wireline. In some cases, a cement retainer cannot be unset once it has been set in a tubing but can be drilled out. 
     SUMMARY 
     This disclosure describes technologies relating to downhole cementing. Certain aspects of the subject matter described can be implemented as an apparatus for flowing and mixing cement within a subterranean formation. The apparatus includes a housing, a flow control device, and baffles. The housing is configured to contain a cement additive. The housing includes a first end and a second end opposite the first end. The first end is configured to couple to a cement retainer. The flow control device is selected from the group consisting of a rupture disc and a float valve. The flow control device is disposed at the second end of the housing. The baffles are disposed within the housing. 
     This, and other aspects, can include one or more of the following features. 
     In some implementations, the housing includes a wall connecting the first end to the second end. In some implementations, the apparatus includes a first port disposed at the first end of the housing, and the first port is configured to couple to the cement retainer. In some implementations, the apparatus includes a second port disposed at the second end of the housing. In some implementations, the apparatus includes a pressure injection port disposed at the wall of the housing. 
     In some implementations, the flow control device is configured to prevent fluid flow out of the housing through the flow control device up to a first pressure threshold value. In some implementations, the apparatus includes a rupture disc disposed at the wall of the housing. In some implementations, the rupture disc is configured to prevent fluid flow out of the housing through the rupture disc up to a second pressure threshold value. In some implementations, the rupture disc is configured to rupture in response to being exposed to a pressure equal to or greater than the second pressure threshold value, thereby allowing fluid flow out of the housing through the ruptured rupture disc. 
     In some implementations, the housing is at least partially made of polycrystalline diamond compact, and the wall is a cylindrical wall defining an outer diameter in a range of from 4 inches to 13⅜ inches. 
     In some implementations, each of the baffles are coupled to and protrude from an inner surface of the wall of the housing. 
     In some implementations, each of the baffles are sloped toward the first end of the housing. 
     In some implementations, the housing has a longitudinal axis defined from the first end to the second end, and each of the baffles intersect with the longitudinal axis. 
     Certain aspects of the subject matter described can be implemented as a method. A cement retainer coupled to an apparatus is run downhole into a wellbore formed in a subterranean formation using a tubing string. The apparatus includes a housing, a flow control device, and baffles. The housing is configured to contain a cement additive. The housing includes a first end and a second end opposite the first end. The first end is configured to couple to a cement retainer. The flow control device is selected from the group consisting of a rupture disc and a float valve. The flow control device is disposed at the second end of the housing. The baffles are disposed within the housing. The cement retainer is set within the wellbore. The cement retainer is released from the tubing string. Cement is flowed into the tubing string until the cement reaches an end of the tubing string. After the cement reaches the end of the tubing string, the tubing string is coupled to the cement retainer. The cement is flowed through the cement retainer and through the apparatus. 
     This, and other aspects, can include one or more of the following features. 
     In some implementations, the flow control device is configured to prevent fluid flow out of the housing through the flow control device up to a first pressure threshold value. In some implementations, flowing the cement through the cement retainer and through the apparatus includes flowing the cement from the cement retainer into the housing, resulting in the cement mixing with the cement additive. The mixing of the cement with the cement additive is facilitated by the plurality of baffles. In some implementations, flowing the cement through the cement retainer and through the apparatus includes flowing the cement at a pressure equal to or greater than the first pressure threshold value, such that the cement and the cement additive flow out of the housing through the flow control device. 
     In some implementations, the housing includes a wall connecting the first end to the second end. In some implementations, the apparatus includes a rupture disc disposed at the wall of the housing. In some implementations, the rupture disc is configured to prevent fluid flow out of the housing through the rupture disc up to a second pressure threshold value. In some implementations, the rupture disc is configured to rupture in response to being exposed to a pressure equal to or greater than the second pressure threshold value, thereby allowing fluid flow out of the housing through the ruptured rupture disc. In some implementations, the cement is flowed at a pressure equal to or greater than the second pressure threshold value, such that the cement flows out of the housing through the rupture disc. In some implementations, the second pressure threshold value is greater than the first pressure threshold value. 
     Certain aspects of the subject matter described can be implemented as a system. The system includes a cement retainer and an apparatus. The apparatus includes a housing, a first port, a second port, a pressure injection port, a flow control device, a rupture disc, and baffles. The housing includes a first end, a second end, and a wall connecting the first end to the second end. The first port is disposed at the first end of the housing. The first port is coupled to the cement retainer. The second port is disposed at the second end of the housing. The pressure injection port is disposed at the wall of the housing. The flow control device is selected from the group consisting of a rupture disc and a float valve. The flow control device is disposed at the second end of the housing. The flow control device is configured to prevent fluid flow out of the housing through the flow control device up to a first pressure threshold value. The rupture disc is disposed at the wall of the housing. The rupture disc is configured to prevent fluid flow out of the housing through the rupture disc up to a second pressure threshold value. The rupture disc is configured to rupture in response to being exposed to a pressure equal to or greater than the second pressure threshold value, thereby allowing fluid flow out of the housing through the ruptured rupture disc. The baffles are disposed within the housing. 
     This, and other aspects, can include one or more of the following features. 
     In some implementations, the housing is at least partially made of polycrystalline diamond compact, and the wall is a cylindrical wall defining an outer diameter in a range of from 4 inches to 13⅜ inches. 
     In some implementations, each of the baffles are coupled to and protrude from an inner surface of the wall of the housing. 
     In some implementations, each of the baffles are sloped toward the first end of the housing. 
     In some implementations, the housing has a longitudinal axis defined from the first end to the second end, and each of the baffles intersect with the longitudinal axis. 
     In some implementations, the apparatus is a first apparatus. In some implementations, the system includes a second apparatus that is substantially the same as the first apparatus. In some implementations, a first port of the second apparatus is coupled to the second port of the first apparatus. 
     In some implementations, a composition of a cement additive contained within the second apparatus is different from a composition of the cement additive contained within the first apparatus. 
     In some implementations, the second pressure threshold value is greater than the first pressure threshold value. 
     In some implementations, the system includes an emergency rupture disc disposed at the wall of the housing. The emergency rupture disc can be configured to prevent fluid flow out of the housing through the emergency rupture disc up to a third pressure threshold value. The emergency rupture disc can be configured to rupture in response to being exposed to a pressure equal to or greater than the third pressure threshold value, thereby allowing fluid flow out of the housing through the ruptured emergency rupture disc. In some implementations, the third pressure threshold value is greater than the first pressure threshold value. In some implementations, the third pressure threshold value is equal to or greater than the second pressure threshold value. 
     The details of one or more implementations of the subject matter of this disclosure are set forth in the accompanying drawings and the description. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG.  1    is a schematic diagram of an example well. 
         FIG.  2 A  is a schematic diagram of an example apparatus that can be coupled to a cement retainer. 
         FIG.  2 B  is a schematic diagram of the apparatus of  FIG.  2 A  coupled to a cement retainer. 
         FIG.  2 C  is a schematic diagram of an example system including an implementation of the apparatus of  FIG.  2 A  coupled to a cement retainer. 
         FIG.  3    is a flow chart of an example method for using the apparatus of  FIG.  2 A . 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure describes downhole cementing. The modular additive cementing apparatus is configured to couple to a cement retainer and be run downhole along with the cement retainer. The apparatus includes multiple baffles and contains a cement additive. Once the cement retainer has been set within a wellbore, cement is pumped through the cement retainer and through the apparatus. The cement mixes with the cement additive within the apparatus. The baffles facilitate the mixing of the cement and the cement additive. The mixture of the cement and the cement additive flow out of the apparatus and further downhole into the wellbore. The apparatus can be used to mix the cement with the cement additive downhole (that is, within the wellbore at a desired depth) as opposed to pre-mixing the cement and the cement additive at the surface and pumping the mixture downhole. 
     The subject matter described in this disclosure can be implemented in particular implementations, so as to realize one or more of the following advantages. The apparatus and method described can be implemented to mitigate and/or eliminate the risk of flash setting cement during downhole cementing operations. The apparatus and method described can be implemented to increase overall efficiency in remedial cementing operations by allowing aggressive cement slurry designs to be pumped and mixed downhole in contrast to conventional apparatuses and methods that require mixing to occur before pumping the mixed slurry downhole from the surface. The apparatus and method described can allow for pump-through capability across a cement retainer positioned downhole. In some cases, the apparatus includes a rupture disc, such that in the event of plugging, rupturing the rupture disc provides an avenue of circulation. After the rupture disc has ruptured, flow is directed through the apparatus, which can cause desired additives stored within the apparatus to flow further downhole. The apparatus is configured as a modular apparatus, such that multiple implementations of the apparatus can be run in series as modular units, which can allow for increased total volume of additives and/or multiple fluid systems to be mixed and pumped, separately, downhole. In some cases, the apparatus is configured to be compatible with a retrievable cement retainer. The apparatus and method described can be implemented to pump un-accelerated cement through a cement retainer and mix, in a downhole environment, the un-accelerated cement with a cement additive including an accelerant. 
       FIG.  1    depicts an example well  100  constructed in accordance with the concepts herein. The well  100  extends from the surface  106  through the Earth  108  to one more subterranean zones of interest  110  (one shown). The well  100  enables access to the subterranean zones of interest  110  to allow recovery (that is, production) of fluids to the surface  106  (represented by flow arrows in  FIG.  1   ) and, in some implementations, additionally or alternatively allows fluids to be placed in the Earth  108 . In some implementations, the subterranean zone  110  is a formation within the Earth  108  defining a reservoir, but in other instances, the zone  110  can be multiple formations or a portion of a formation. The subterranean zone can include, for example, a formation, a portion of a formation, or multiple formations in a hydrocarbon-bearing reservoir from which recovery operations can be practiced to recover trapped hydrocarbons. In some implementations, the subterranean zone includes an underground formation of naturally fractured or porous rock containing hydrocarbons (for example, oil, gas, or both). In some implementations, the well can intersect other types of formations, including reservoirs that are not naturally fractured. For simplicity&#39;s sake, the well  100  is shown as a vertical well, but in other instances, the well  100  can be a deviated well with a wellbore deviated from vertical (for example, horizontal or slanted), the well  100  can include multiple bores forming a multilateral well (that is, a well having multiple lateral wells branching off another well or wells), or both. 
     In some implementations, the well  100  is a gas well that is used in producing hydrocarbon gas (such as natural gas) from the subterranean zones of interest  110  to the surface  106 . While termed a “gas well,” the well need not produce only dry gas, and may incidentally or in much smaller quantities, produce liquid including oil, water, or both. In some implementations, the well  100  is an oil well that is used in producing hydrocarbon liquid (such as crude oil) from the subterranean zones of interest  110  to the surface  106 . While termed an “oil well,” the well not need produce only hydrocarbon liquid, and may incidentally or in much smaller quantities, produce gas, water, or both. In some implementations, the production from the well  100  can be multiphase in any ratio. In some implementations, the production from the well  100  can produce mostly or entirely liquid at certain times and mostly or entirely gas at other times. For example, in certain types of wells it is common to produce water for a period of time to gain access to the gas in the subterranean zone. The concepts herein, though, are not limited in applicability to gas wells, oil wells, or even production wells, and could be used in wells for producing other gas or liquid resources or could be used in injection wells, disposal wells, or other types of wells used in placing fluids into the Earth. 
     The wellbore of the well  100  is typically, although not necessarily, cylindrical. All or a portion of the wellbore is lined with a tubing, such as casing  112 . The casing  112  connects with a wellhead at the surface  106  and extends downhole into the wellbore. The casing  112  operates to isolate the bore of the well  100 , defined in the cased portion of the well  100  by the inner bore  116  of the casing  112 , from the surrounding Earth  108 . The casing  112  can be formed of a single continuous tubing or multiple lengths of tubing joined (for example, threadedly) end-to-end. In some implementations, the casing  112  is omitted or ceases in the region of the subterranean zone of interest  110 . This portion of the well  100  without casing is often referred to as “open hole.” 
     In particular, casing  112  is commercially produced in a number of common sizes specified by the American Petroleum Institute (the “API”), including 4½, 5, 5½, 6, 6⅝, 7, 7⅝, 7¾, 8⅝, 8¾, 9⅝, 9¾, 9⅞, 10¾, 11¾, 11⅞, 13⅜, 13½, 13⅝, 16, 18⅝, and 20 inches, and the API specifies internal diameters for each casing size. 
       FIG.  2 A  is a schematic diagram of the apparatus  200 , which can be coupled to a cement retainer. The apparatus  200  includes a housing  201 , a flow control device  203 , and baffles  205 . The housing  201  is configured to contain a cement additive. The cement additive can be liquid or dry. The housing  201  includes a first end  201   a  and a second end  201   b  opposite the first end  201   a . The housing  201  includes a wall  201   c  connecting the first end  201   a  to the second end  201   b . The housing  201  has a longitudinal axis/that is defined from the first end  201   a  to the second end  201   b . The first end  201   a  is configured to couple to a cement retainer. The flow control device  203  is disposed at the second end  201   b  of the housing  201 . The baffles  205  are disposed within the housing  201 . The housing  201  can be at least partially made of polycrystalline diamond compact. In some implementations, the housing  201  is at least partially made of brass, aluminum, cast iron, or an epoxy-reinforced fiber glass. In some implementations, the wall  201   c  is a cylindrical wall that defines an outer diameter in a range of from 4 inches to 13⅜ inches. 
     The flow control device  203  is configured to prevent fluid flow out of the housing  201  through the flow control device  203  up to a first pressure threshold value. In response to being exposed to a pressure equal to or greater than the first pressure threshold value, the flow control device  203  is configured to allow fluid flow out of the housing  201  through the flow control device  203 . In some implementations, the flow control device  203  is a float valve. In some implementations, the flow control device  203  is a rupture disc, in which case, the flow control device  203  is configured to rupture in response to being exposed to a pressure equal to or greater than the first pressure threshold value, thereby allowing fluid flow out of the housing  201  through the ruptured flow control device  203 . 
     Each of the baffles  205  are coupled to and protrude from an inner surface of the wall  201   c  of the housing  201 . In some implementations, one or more of the baffles  205  are sloped toward the first end  201   a  of the housing  201 . In some implementations, one or more of the baffles  205  intersect with the longitudinal axis  1 . 
     In some implementations, the apparatus  200  includes a first port  207   a  that is disposed at the first end  201   a  of the housing  201 . The first port  207   a  can be configured to couple to the cement retainer. In some implementations, the apparatus  200  includes a second port  207   b  that is disposed at the second end  201   a  of the housing  201 . In some implementations, the first port  207   a  is configured to couple to the second port  207   b  of another implementation of the apparatus  200 . An example of a system including multiple implementations of the apparatus  200  coupled together is shown in  FIG.  2 C  and described in more detail later. 
     In some implementations, the apparatus  200  includes a pressure injection port  207   c  that is disposed at the wall  201   c  of the housing  201 . In some implementations, the pressure injection port  207   c  includes a check valve that allows fluid flow in one direction (for example, into the housing  201 ) and prevents fluid flow in an opposite direction (for example, out of the housing  201 ) through the check valve. The pressure injection port  207   c  can be used to pressurize the internal volume of the housing  201 , which can help to mitigate and/or prevent collapse of the housing  201 , for example, while being run downhole and/or being exposed to a downhole environment. 
     In some implementations, the apparatus  200  includes a secondary rupture disc  209   a  that is disposed at the wall  201   c  of the housing  201 . The secondary rupture disc  209   a  is configured to prevent fluid flow out of the housing  201  through the secondary rupture disc  209   a  up to a second pressure threshold value. The second pressure threshold value can be greater than the first pressure threshold value. In response to being exposed to a pressure equal to or greater than the second pressure threshold value, the secondary rupture disc  209   a  is configured to rupture, thereby allowing fluid flow out of the housing  201  through the ruptured secondary rupture disc  209   a.    
     In some implementations, the apparatus  200  includes an emergency rupture disc  209   b  that is disposed at the wall  201   c  of the housing  201 . The emergency rupture disc  209   b  is configured to prevent fluid flow out of the housing  201  through the emergency rupture disc  209   b  up to a third pressure threshold value. The third pressure threshold value can be greater than the first pressure threshold value. The third pressure threshold value can be equal to or greater than the second pressure threshold value. In response to being exposed to a pressure equal to or greater than the third pressure threshold value, the emergency rupture disc  209   b  is configured to rupture, thereby allowing fluid flow out of the housing  201  through the ruptured emergency rupture disc  209   b.    
       FIG.  2 B  is a schematic diagram of the apparatus  200  coupled to a cement retainer  250 . As depicted in  FIG.  2 B , the first port  207   a  is coupled to the cement retainer  250 . The cement retainer  250  coupled to the apparatus  200  can be run downhole into a wellbore formed in a subterranean formation (for example, the well  100 ). Once the cement retainer  250  is set in the wellbore, cement can be flowed through the cement retainer  250  and the apparatus  200 . As the cement flows through the apparatus  200 , the cement mixes with the cement additive contained within the apparatus  200 . The mixing of the cement and the cement additive is facilitated by the baffles  205 . The mixture of the cement and the cement additive can flow out of the apparatus  200  (for example, through the flow control device  203 ) and further downhole into the wellbore. Although  FIG.  2 B  shows an uphole end (first end  201   a ) of the apparatus  200  being coupled to a downhole end of the cement retainer  250 , the apparatus  200  can be coupled to an uphole end of the cement retainer  250 . For example, a downhole end (second end  201   b ) of the apparatus  200  can be coupled to the uphole end of the cement retainer  250 . In such implementations where the apparatus  200  is coupled to the uphole end of the cement retainer  250 , a mechanical setting procedure can be implemented, which can allow for cement and/or additives to be pumped and for the apparatus  200  to be milled prior to the slips of the cement retainer  250 . The mechanical setting procedure can decrease and/or eliminate the possibility of debris from falling downhole into the wellbore. 
       FIG.  2 C  is a schematic diagram of a system  290  including multiple implementations of the apparatus  200  coupled to the cement retainer  250 . As depicted in  FIG.  2 C , the system  290  includes a first apparatus  200   a  and a second apparatus  200   b . Each of the first apparatus  200   a  and the second apparatus  200   b  can include the same components as the apparatus  200  shown in  FIG.  2 A . In some implementations, the first apparatus  200   a  and the second apparatus  200   b  contain the same cement additive (for example, to meet a desired total volume of the cement additive). For example, the cement additive contained in the first apparatus  200   a  has the same composition as the cement additive contained in the second apparatus  200   b . In some implementations, the first apparatus  200   a  and the second apparatus  200   b  contain different cement additives (for example, to prevent mixing of the different cement additives before introducing the cement at a desired depth within the wellbore). For example, the cement additive contained in the first apparatus  200   b  has a different composition from the cement additive contained in the second apparatus  200   b . Although shown as including two apparatuses  200   a ,  200   b , the system  290  can include additional implementations of the apparatus  200  (for example, three, four, or more than four). 
     As depicted in  FIG.  2 C , the first port  207   a  of the first apparatus  200   a  is coupled to the cement retainer  250 , and the first port  207   a  of the second apparatus  200   b  is coupled to the second port  207   b  of the first apparatus  200   a . The cement retainer  250  coupled to the apparatuses  200   a ,  200   b  can be run downhole into a wellbore formed in a subterranean formation (for example, the well  100 ). Once the cement retainer  250  is set in the wellbore, cement can be flowed through the cement retainer  250  and the apparatuses  200   a ,  200   b . As the cement flows through the first apparatus  200   a , the cement mixes with the cement additive contained within the first apparatus  200   a  to form a first mixture. The mixing of the cement and the cement additive to form the first mixture is facilitated by the baffles  205  of the first apparatus  200   a . The first mixture can flow out of the first apparatus  200   a  (for example, through the flow control device  203  of the first apparatus  200   a ) and into the second apparatus  200   b . As the first mixture flows through the second apparatus  200   b , the first mixture mixes with the cement additive contained within the second apparatus  200   b  to form a second mixture. The mixing of the first mixture and the cement additive to form the second mixture is facilitated by the baffles  205  of the second apparatus  200   b . The second mixture can flow out of the second apparatus  200   b  (for example, through the flow control device  203  of the second apparatus  200   b ) and further downhole into the wellbore. Although  FIG.  2 C  shows an uphole end (first end  201   a ) of the apparatus  200   a  being coupled to a downhole end of the cement retainer  250 , the apparatuses  200   a  and  200   b  can be coupled to an uphole end of the cement retainer  250 . For example, a downhole end (second end  201   b ) of apparatus  200   a  can be coupled to an uphole end (first end  201   a ) of the apparatus  200   b , and a downhole end ( 201   b ) of the apparatus  200   b  can be coupled to the uphole end of the cement retainer  250 . 
       FIG.  3    is a flow chart of a method  300  which can be implemented using the apparatus  200 . At step  302 , a cement retainer (such as the cement retainer  250 ) is run downhole into a wellbore formed in a subterranean formation (such as the well  100 ) using a tubing string. The cement retainer  250  is coupled to the apparatus  200 . The cement retainer  250  and the apparatus  200  are run downhole together into the wellbore at step  302 . As described previously, the apparatus  200  includes the housing  201 , the flow control device  203 , and the baffles  205 . The housing  201  contains a cement additive. 
     Once the cement retainer  250  is at a desired depth within the wellbore, the cement retainer  250  is set within the wellbore at step  304 . For example, the cement retainer  250  is coupled to the casing  112 . The cement retainer  250  can be set within the wellbore at step  304  mechanically with a mechanical setting tool, hydraulically by applying hydraulic force from the surface  106 , or using a wireline pressure setting tool, in which the cement retainer  250  is run on an electrical conductor wireline. 
     At step  306 , the cement retainer  250  is released from the tubing string. 
     At step  308 , cement is flowed into the tubing string until the cement reaches an end (for example, the downhole end) of the tubing string. 
     After the cement reaches the end of the tubing string at step  308 , the tubing string is re-coupled to the cement retainer  250  at step  310 . 
     At step  312 , the cement is flowed from the tubing string through the cement retainer  250  and through the apparatus  200 . In some implementations, flowing the cement through the cement retainer  250  and through the apparatus  200  at step  312  includes flowing the cement from the cement retainer  250  into the housing  201 , resulting in the cement mixing with the cement additive contained within the housing  201 . The mixing of the cement and the cement additive is facilitated by the baffles  205 . In some implementations, flowing the cement through the cement retainer  250  and through the apparatus  200  at step  312  includes flowing the cement at a pressure that is equal to or greater than the first pressure threshold value, such that the mixture of the cement and the cement additive flow out of the housing  201  through the flow control device  203 . 
     Flowing the cement into the tubing string until the cement reaches the end of the tubing string at step  308  before flowing the cement through the apparatus  200  at step  312  mitigates and/or eliminates the risk of prematurely flowing the cement additive out of the housing  201  before the cement additive has mixed with the cement. 
     In some implementations, the method  300  includes flowing the cement at a pressure equal to or greater than the second pressure threshold value, such that secondary rupture disc  209   a  ruptures, and the cement flows out of the housing  201  through the ruptured secondary rupture disc  209   a . In some implementations, the method  300  includes flowing the cement at a pressure equal to or greater than the third pressure threshold value, such that emergency rupture disc  209   b  ruptures, and the cement flows out of the housing  201  through the ruptured emergency rupture disc  209   b.    
     While this specification contains many specific implementation details, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features that may be specific to particular implementations. Certain features that are described in this specification in the context of separate implementations can also be implemented, in combination, in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations, separately, or in any sub-combination. Moreover, although previously described features may be described as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can, in some cases, be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination. 
     As used in this disclosure, the terms “a,” “an,” or “the” are used to include one or more than one unless the context clearly dictates otherwise. The term “or” is used to refer to a nonexclusive “or” unless otherwise indicated. The statement “at least one of A and B” has the same meaning as “A, B, or A and B.” In addition, it is to be understood that the phraseology or terminology employed in this disclosure, and not otherwise defined, is for the purpose of description only and not of limitation. Any use of section headings is intended to aid reading of the document and is not to be interpreted as limiting; information that is relevant to a section heading may occur within or outside of that particular section. 
     As used in this disclosure, the term “about” or “approximately” can allow for a degree of variability in a value or range, for example, within 10%, within 5%, or within 1% of a stated value or of a stated limit of a range. 
     As used in this disclosure, the term “substantially” refers to a majority of, or mostly, as in at least about 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or at least about 99.999% or more. 
     Values expressed in a range format should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a range of “0.1% to about 5%” or “0.1% to 5%” should be interpreted to include about 0.1% to about 5%, as well as the individual values (for example, 1%, 2%, 3%, and 4%) and the sub-ranges (for example, 0.1% to 0.5%, 1.1% to 2.2%, 3.3% to 4.4%) within the indicated range. The statement “X to Y” has the same meaning as “about X to about Y,” unless indicated otherwise. Likewise, the statement “X, Y, or Z” has the same meaning as “about X, about Y, or about Z,” unless indicated otherwise. 
     Particular implementations of the subject matter have been described. Other implementations, alterations, and permutations of the described implementations are within the scope of the following claims as will be apparent to those skilled in the art. While operations are depicted in the drawings or claims in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed (some operations may be considered optional), to achieve desirable results. In certain circumstances, multitasking or parallel processing (or a combination of multitasking and parallel processing) may be advantageous and performed as deemed appropriate. 
     Moreover, the separation or integration of various system modules and components in the previously described implementations should not be understood as requiring such separation or integration in all implementations, and it should be understood that the described components and systems can generally be integrated together or packaged into multiple products. 
     Accordingly, the previously described example implementations do not define or constrain the present disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of the present disclosure.