Note: Descriptions are shown in the official language in which they were submitted.
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SYSTEMS AND METHODS FOR DETECTING MICROANNULUS FORMATION
AND REMEDIATION
BACKGROUND
[0001] The present invention relates to optical analysis systems and
methods for analyzing wellbore casings, and in particular, systems and methods
for detecting nnicroannulus formation in a wellbore casing and rennediating a
microannulus.
[0002] In constructing a wellbore, a cement slurry is typically placed in
the annular volume between the exterior of the casing and the wall of the
wellbore that, once hardened, forms a cement sheath. The cement sheath, inter
alia, supports the casing and prevents fluids from migrating between the
various
zones of the wellbore. In some instances, the bond between the cement sheath
and casing can fail. This failure can produce a very thin annular space, known
as
a nnicroannulus, between the exterior surface of the casing and the cement
sheath. The nnicroannulus can permit fluids to migrate between zones of the
subterranean formation, which can reduce the quality and efficiency of
production operations. Further, a nnicroannulus can serve as a starting point
for
more significant failures in the casing, including those that lead to portions
of
the wellbore collapsing.
[0003] A nnicroannulus can form for many reasons including, for
example, fluctuations in temperature and pressure in a wellbore after
formation
of the cement sheath.
[0004] A cement bond log is one of the methods used to determine if a
nnicroannulus has formed. Because a casing that is bonded to a cement sheath
attenuates sound differently than a casing that is not bonded thereto, a
cement
bond log uses sonic-type tools to measure amplitude variations in acoustic
signals. Typically, cement bond logs are run shortly after formation of the
cement sheath. After other wellbore operations have begun, analysis for
nnicroannulus formation often requires shutting down production and performing
another cement bond log, thereby increasing nonproductive time and costs.
Accordingly, systems and methods for detecting nnicroannulus formation with
minimal downtime would be of value.
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SUMMARY OF THE INVENTION
[0005] The present invention relates to optical analysis systems and
methods for analyzing wellbore casings, and in particular, systems and methods
for detecting nnicroannulus formation in a wellbore casing and rennediating a
nnicroannulus.
[0006] One embodiment of the present invention is a system that
comprises a cement sheath disposed about and in contact with at least a
portion
of an exterior surface of a casing; and at least one optical computing device
arranged on the casing, the at least one optical computing device having at
least
one integrated computational element configured to optically interact with a
material of interest and thereby generate optically interacted light, and at
least
one detector arranged to receive the optically interacted light and generate
an
output signal corresponding to a characteristic of the material of interest,
the
material of interest comprising at least one selected from the group
consisting of
the cement sheath, a displacement composition disposed between the cement
sheath and the exterior surface of the casing, and any combination thereof.
[0007] Another embodiment of the present invention is a system that
comprises a cement sheath disposed about and in contact with at least a
portion
of an exterior surface of a casing; and at least one integrated computational
element configured to optically interact with a material of interest and
thereby
generate optically interacted light, and at least one detector arranged to
receive
the optically interacted light and generate an output signal corresponding to
a
characteristic of the material of interest, the material of interest
comprising at
least one selected from the group consisting of the cement sheath, a
displacement composition disposed between the cement sheath and the exterior
surface of the casing, and any combination thereof.
[0008] Yet another embodiment of the present invention is a method
that comprises optically interacting a material of interest and at least one
integrated computational element, thereby generating an output signal
corresponding to a characteristic of the material of interest, the material of
interest comprising at least one selected from the group consisting of a
cement
sheath disposed about and in contact with at least a portion of an exterior
surface of a casing, a displacement composition disposed between the cement
sheath and the exterior surface of the casing, and any combination thereof.
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[0009] The features and advantages of the present invention will be
readily apparent to those skilled in the art upon a reading of the description
of
the preferred embodiments that follows.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The following figures are included to illustrate certain aspects of
the present invention, and should not be viewed as exclusive embodiments. The
subject matter disclosed is capable of considerable modifications,
alterations,
combinations, and equivalents in form and function, as will occur to those
skilled
in the art and having the benefit of this disclosure.
[0011] FIG. 1 illustrates an exemplary integrated computational
element, according to one or more embodiments.
[0012] FIG. 2 illustrates a block diagram non-mechanistically illustrating
how an optical computing device distinguishes electromagnetic radiation
related
to a characteristic of interest from other electromagnetic radiation,
according to
one or more embodiments.
[0013] FIGS. 3A-B illustrate an exemplary system for monitoring a
cement sheath, according to one or more embodiments.
[0014] FIG. 4 illustrates an exemplary system for monitoring a cement
sheath, according to one or more embodiments.
DETAILED DESCRIPTION
[0015] The present invention relates to optical analysis systems and
methods for analyzing wellbore casings, and in particular, systems and methods
for detecting nnicroannulus formation in a wellbore casing and rennediating a
microannulus.
[0016] The exemplary systems and methods described herein employ
various configurations of optical computing devices, also commonly referred to
as "opticoanalytical devices," for detecting indicators of nnicroannulus
formation,
e.g., pulling away of a cement sheath from a casing and/or infiltration of
displacement compositions between a cement sheath and a casing. For example,
the optical computing devices, which are described in more detail below, may
advantageously provide real-time or near real-time monitoring of a cement
sheath and/or the infiltration of a displacement composition, which can be
indicative of nnicroannulus formation. In another example, the optical
computing
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devices may advantageously provide monitoring of a cement sheath and/or
infiltration of a displacement composition over an extended time period (e.g.,
weeks to months to years, depending on the application), where the data is
stored locally with the optical computing devices and retrieved when desired.
In
this example, long-term monitoring for nnicroannulus formation may
advantageously be utilized in a cement sheath health analysis. In either
example, monitoring and analyzing for nnicroannulus formation may be used in
determining the parameters, e.g., location and size, of remedial operations
like
cement squeeze operations.
[0017] The disclosed systems and methods may be suitable for use in
the oil and gas industry since the described optical computing devices provide
a
relatively low cost, rugged, and accurate means for monitoring materials of
interest, e.g., a cement composition and/or fluids. It will be appreciated,
however, that the various disclosed systems and methods are equally applicable
to other technology fields including, but not limited to, industrial
applications,
mining industries, CO2 injection well applications, and any field where it may
be
advantageous to analyze for nnicroannulus formation.
[0018] As used herein, the term "cement" refers to a hardenable
material suitable for use to seal off an annular space in a wellbore. Cement
is
not necessarily hydraulic cement, since other types of materials (e.g.,
epoxies,
latexes, and bentonites) can be used in place of, or in addition to, a
hydraulic
cement. As used herein, the term "hydraulic cement" refers to a cement that
hardens in the presence of water. Exemplary examples of cements may include,
but are not limited to, Portland cement, gypsum cements, calcium phosphate
cements, high alumina content cements, silica cements, high alkalinity
cements,
shale cements, acid/base cements, magnesia cements such as Sorel cements, fly
ash cements, zeolite cement systems, cement kiln dust cement systems, slag
cements, micro-fine cements, and the like, any derivative thereof, and any
combination thereof. Cement compositions described herein may harden by
hydrating, by passage of time, by application of heat, by cross-linking,
and/or by
any other technique, method, or means.
[0019] As used herein, the term "cement sheath" refers to a cement
composition disposed about and in contact with at least a portion of an
exterior
surface of a casing.
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[0020] As used herein, the terms "remedial methods" or "remedial
operations" refer to procedures carried out in subterranean formations or in
wellbores penetrating the formations to correct problems such as cementing a
nnicroannulus (e.g., cement squeeze operations), sealing leaks, cracks or
voids,
placing plugs in the wellbore or in zones or formations containing undesirable
fluids, placing temporary plugs in lieu of packers to isolate zones or
formations,
filling external casing packers, and the like.
[0021] As used herein, the term "displacement composition" refers to a
composition that congregates in the nnicroannulus after the nnicroannulus has
been formed. Displacement compositions may include, but are not limited to,
native wellbore fluids, treatment fluids, and any combination thereof.
Displacement compositions can include various liquids, gases, mixtures
thereof,
and compositions having solids suspended therein.
[0022] As used herein, the term "fluid" refers to any substance that is
capable of flowing, including, but not limited to, particulate solids,
liquids, gases,
foams, slurries, emulsions, powders, muds, glasses, and the like, and any
combination thereof. Exemplary examples of displacement compositions may
include, but are not limited to, aqueous-based fluids (e.g., water or brines),
oleaginous-based fluids (e.g., organic compounds, hydrocarbons, oil, a refined
component of oil, or petrochemical products), gases (e.g., air, nitrogen,
carbon
dioxide, hydrogen sulfide (H25), argon, helium, methane, ethane, butane, or
other hydrocarbon gases), and the like, and any combination thereof.
[0023] As used herein, the term "electromagnetic radiation" refers to
radio waves, microwave radiation, infrared and near-infrared radiation,
visible
light, ultraviolet light, X-ray radiation, and gamma ray radiation.
[0024] As used herein, the term "optical computing device" refers to an
optical device that is configured to receive an input of electromagnetic
radiation
from a material of interest or sample of the material of interest, and produce
an
output of electromagnetic radiation from a processing element arranged within
the optical computing device. The processing element may be, for example, an
integrated computational element ("ICE") used in the optical computing device.
As discussed in greater detail below, the electromagnetic radiation that
optically
interacts with the processing element is changed so as to be readable by a
detector, such that an output of the detector can be correlated to at least
one
characteristic of the material of interest being measured or monitored. The
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output of electromagnetic radiation from the processing element can be
reflected
electromagnetic radiation, transmitted electromagnetic radiation, and/or
dispersed electromagnetic radiation. Whether reflected or transmitted,
electromagnetic radiation analyzed by the detector may be dictated by the
structural parameters of the optical computing device as well as other
considerations known to those skilled in the art. In addition, emission and/or
scattering by the material of interest (e.g., via fluorescence, luminescence,
Raman scattering, and/or Raleigh scattering) can also be monitored by the
optical computing devices.
[0025] As used herein, the term "optically interact" or variations thereof
refers to the reflection, transmission, scattering, diffraction, or absorption
of
electromagnetic radiation either on, through, or from one or more processing
elements (i.e., integrated computational elements). Accordingly, optically
interacted light refers to light that has been reflected, transmitted,
scattered,
diffracted, or absorbed by, emitted, or re-radiated, for example, using the
integrated computational elements, but may also apply to interaction with a
material of interest (e.g., a cement sheath and/or a displacement
composition).
[0026] As described above, a nnicroannulus, a small gap between a
casing and the surrounding cement sheath, may form, at least in part, because
of fluctuations in temperature and pressure in a wellbore after formation of
the
cement sheath. It should be noted that the term "casing" encompasses any
tubular structure used to contain a fluid, which may include, but are not
limited
to, liners, pipes, conduits, and the like.
[0027] Formation of a nnicroannulus can lead to, inter alia, changes in
the properties of the cement sheath, infiltration of a displacement
composition
into the nnicroannulus, and the like. Accordingly, the characteristics of a
cement
sheath and/or characteristics of a displacement composition that infiltrates a
nnicroannulus may, in some embodiments, be related to indicators of the
potential formation of a nnicroannulus. Exemplary examples of nnicroannulus
indicators may, in some embodiments, include, but are not limited to, the
presence of a displacement composition, porosity changes of a cement sheath,
temperature changes of a cement sheath, pH level of the material of interest,
decreased output signal relating to the characteristic of interest, changes to
the
chemical composition of the cement sheath, and any combination thereof. For
example, an optical computing device configured to measure a characteristic of
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the cement sheath may yield an output signal (described in more detail herein)
in response to, inter alia, the cement sheath having pulled away from the
casing
as the interacted light (described in more detail herein) has a longer
distance to
travel and/or a displacement composition becomes disposed between the optical
computing device and the cement sheath and also interacts with the
displacement composition.
[0028] The exemplary systems and methods described herein may, in
some embodiments, include at least one optical computing device coupled to or
otherwise arranged adjacent to a casing and configured to measure at least one
characteristic of a cement sheath and/or a displacement composition.
[0029] As used herein, the term "characteristic" refers to a chemical,
mechanical, or physical property (quantitative or qualitative) of a material
of
interest (e.g., a cement sheath, a displacement composition, or analyte
thereof).
As used herein, the term "analyte" refers to a chemical component. The term
analyte encompasses chemical components that are at least one of: present in
the material of interest, may be added to the material of interest, involved
in a
chemical reaction (e.g., reagents and products) transpiring within the
material of
interest, and not involved in a chemical reaction transpiring within the
material
of interest. Illustrative characteristics that can be monitored with the
optical
computing devices disclosed herein can include, for example, chemical
composition (e.g., identity and concentration in total or of individual
analytes),
impurity content, pH, viscosity, density, ionic strength, total dissolved
solids, salt
content, porosity, opacity, bacteria content, particle size distribution,
color,
temperature, hydration level, oxidation state, and the like. Moreover, the
phrase
"characteristic of interest" may be used herein to refer to a characteristic
of a
material of interest or analyte thereof.
[0030] Exemplary analytes may include, but are not limited to, water,
salts, minerals (wollastonite, nnetakaolin, and pumice), cements (Portland
cement, gypsum cements, calcium phosphate cements, high alumina content
cements, silica cements, and high alkalinity cements), fillers (e.g., fly ash,
fume
silica, hydrated lime, pozzolanic materials, sand, barite, calcium carbonate,
ground marble, iron oxide, manganese oxide, glass bead, crushed glass, crushed
drill cutting, ground vehicle tire, crushed rock, ground asphalt, crushed
concrete,
crushed cement, ilnnenite, hematite, silica flour, fume silica, fly ash,
elastomers,
polymers, diatomaceous earth, a highly swellable clay mineral, nitrogen, air,
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fibers, natural rubber, acrylate butadiene rubber, polyacrylate rubber,
isoprene
rubber, chloroprene rubber, butyl rubber, bronninated butyl rubber,
chlorinated
butyl rubber, chlorinated polyethylene, neoprene rubber, styrene butadiene
copolymer rubber, sulphonated polyethylene, ethylene acrylate rubber,
epichlorohydrin ethylene oxide copolymer, ethylene propylene rubber, ethylene
propylene diene terpolynner rubber, ethylene vinyl acetate copolymer,
flourosilicone rubber, silicone rubber,
poly-2,2,1-bicycloheptene
(polynorbonneane), alkylstyrene, crosslinked substituted vinyl acrylate
copolymer, nitrile rubber (butadiene acrylonitrile copolymer), hydrogenated
nitrile rubber, fluoro rubber, perfluoro rubber,
tetraflouroethylene/propylene,
starch polyacrylate acid graft copolymer, polyvinyl alcohol cyclic acid
anhydride
graft copolymer, isobutylene nnaleic anhydride, acrylic acid type polymer,
vinylacetate-acrylate copolymer, polyethylene oxide polymer, carboxynnethyl
cellulose polymer, starch-polyacrylonitrile graft copolymer,
polynnethacrylate,
polyacrylannide, and non-soluble acrylic polymer), hydrocarbons, acids, acid-
generating compounds, bases, base-generating compounds, biocides,
surfactants, scale inhibitors, corrosion inhibitors, gelling agents,
crosslinking
agents, anti-sludging agents, foaming agents, defoanning agents, antifoann
agents, emulsifying agents, de-emulsifying agents, iron control agents,
proppants or other particulates, gravel, particulate diverters, salts, cement
slurry
loss control additives, gas migration control additives, gases, air, nitrogen,
carbon dioxide, hydrogen sulfide (H25), argon, helium, hydrocarbon gases,
methane, ethane, butane, catalysts, clay control agents, chelating agents,
corrosion inhibitors, dispersants, flocculants, scavengers (e.g., H25
scavengers,
CO2 scavengers, or 02 scavengers), lubricants, breakers, delayed release
breakers, friction reducers, bridging agents, viscosifiers, weighting agents,
solubilizers, rheology control agents, viscosity modifiers, pH control agents
(e.g.,
buffers), hydrate inhibitors, relative permeability modifiers, diverting
agents,
consolidating agents, fibrous materials, bactericides, tracers, probes,
nanoparticles, paraffin waxes, asphaltenes, foams, sand or other solid
particles,
and the like. Combinations of these components can be used as well. By way of
nonlinniting example, the characteristic of interest of a displacement
composition
may be methane concentration, and increased methane concentration (e.g.,
from essentially no methane to a detectible concentration of methane) may
indicate the formation of a nnicroannulus.
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[0031] In some embodiments, a material of interest may comprise an
analyte (e.g., a tracer analyte and/or a probe analyte) having the primary
purpose of being analyzed by optical computing devices described herein so as
to indicate nnicroannulus formation. For example, a probe analyte may be
included in a cement composition used to form the cement sheath, and a system
may comprise an optical computing device for measuring, for example, the
fluorescence of the probe. In some embodiments, the probe may be sensitive to
the presence of a gas, e.g., carbon dioxide. Accordingly, in the presence of a
gas
to which it is sensitive, the fluorescence intensity may decrease, which may
be
an indicator of nnicroannulus formation. In another example, a tracer analyte
may be included in a variety of wellbore fluids, and a system detecting the
presence of the tracer analyte may indicate wellbore fluid is displacing the
cement sheath, i.e., nnicroannulus formation.
[0032] In some embodiments, systems and methods described herein
may include at least one optical computing device coupled to a casing and
configured to measure a characteristic of a material of interest (e.g., a
cement
sheath and/or a displacement composition). In some embodiments, the optical
computing device may be disposed on the exterior surface of the casing. In
other embodiments, the optical computing device may be integrated into the
wall of the casing and otherwise arranged flush with the exterior surface of
the
casing. In yet other embodiments, the optical computing device may be
integrated into the wall of the casing and extending outwardly beyond the
exterior surface of the casing. Combinations and/or hybrids of the foregoing
integration arrangements may be suitable in some embodiments. Integration
into the wall of the casing may include, but is not limited to, mechanically
coupling the optical computing device to or into a recessed portion of the
wall
using means such as, but not limited to, mechanical fasteners, press fitting,
snap fitting, adhesives, welding or brazing techniques, and the like, and any
combination thereof. It should be noted that the embodiments described herein
relative to optical computing devices coupled to casings can be extended to
optical computing devices couple to a downhole apparatus that is used in
conjunction with a casing that is similarly capable of having a nnicroannulus
form
at a surface, e.g., a centralizer, a casing shoe, or a collar (e.g., a float
collar, a
casing collar, a or landing collar), without departing from the scope of the
disclosure.
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[0033] Each optical computing device may include an electromagnetic
radiation source, at least one processing element (e.g., integrated
computational
elements), and at least one detector arranged to receive optically interacted
light from the at least one processing element. In some embodiments, the
exemplary optical computing devices may be specifically configured for
detecting, analyzing, and quantitatively measuring a particular characteristic
of
the material of interest. In other embodiments, the optical computing devices
may be general purpose optical devices, with post-acquisition processing
(e.g.,
through computer means) being used to specifically detect the characteristic
of
the material of interest.
[0034] In some embodiments, suitable structural components for the
exemplary optical computing devices are described in commonly owned U.S. Pat.
Nos. 6,198,531 entitled "Optical Computational System;" 6,529,276 entitled
"Optical Computational System;" 7,123,844 entitled "Optical Computational
System;" 7,834,999 entitled "Optical Analysis System and Optical Train;"
7,911,605 entitled "Multivariate Optical Elements for Optical Analysis
System;"
7,920,258 entitled "Optical Analysis System and Elements to Isolate Spectral
Region;" and 8,049,881 entitled "Optical Analysis System and Methods for
Operating Multivariate Optical Elements in a Normal Incidence Orientation;"
each
of which is incorporated herein by reference in its entirety, and U.S. Pat.
App.
Serial Nos. 12/094,460 entitled "Methods of High-Speed Monitoring Based on the
Use of Multivariate Optical Elements;" 12/094,465 entitled "Optical Analysis
System for Dynamic Real-Time Detection and Measurement;" and 13/456,467
entitled "Imaging Systems for Optical Computing Devices;" each of which is
also
incorporated herein by reference in its entirety. As will be appreciated,
variations
of the structural components of the optical computing devices described in the
above-referenced patents and patent applications may be suitable, without
departing from the scope of the disclosure, and therefore, should not be
considered limiting to the various embodiments or uses disclosed herein.
[0035] The optical computing devices described in the foregoing patents
and patent applications combine the advantage of the power, precision, and
accuracy associated with laboratory spectrometers, while being extremely
rugged and suitable for field use. Furthermore, the optical computing devices
can perform calculations (analyses) in real-time or near real-time without the
need for time-consuming sample processing. In this regard, the optical
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computing devices can be specifically configured to detect and analyze
particular
characteristics of the material of interest. As a result, interfering signals
are
discriminated from those of interest of the material of interest by
appropriate
configuration of the optical computing devices, such that the optical
computing
devices provide a rapid response regarding the characteristics of interest as
based on the detected output. In some embodiments, the detected output can
be converted into a voltage that is distinctive of the magnitude of the
characteristic being monitored, e.g., the concentration of methane that may
increase (or go from essentially zero to a positive value) when a displacement
composition that comprises methane is present. The foregoing advantages and
others make the optical computing devices particularly well-suited for field
and
downhole use, but may equally be applied to several other technologies or
industries, without departing from the scope of the disclosure.
[0036] The optical computing devices can be configured to detect not
only the composition and concentrations of the material of interest, but they
also
can be configured to determine physical properties and other characteristics
of
the material of interest as well, based on their analysis of the
electromagnetic
radiation received from the particular material of interest. These physical
properties and other characteristics may be used as determining nnicroannulus
indicators. For example, porosity increases may, in some embodiments, indicate
that a nnicroannulus has formed and been infiltrated by a corrosive
composition
that corrodes the cement sheath.
[0037] As will be appreciated, the optical computing devices may be
configured to detect as many characteristics of the material of interest as
desired. All that is required to accomplish the monitoring of multiple
characteristics is the incorporation of suitable processing and detection
means
within the optical computing device for each characteristic. In some
embodiments, the properties of the material of interest can be a combination
of
the properties thereof (e.g., a linear, non-linear, logarithmic, and/or
exponential
combination). Accordingly, the more characteristics that are detected and
analyzed using the optical computing devices, the more accurately the
properties
of the material of interest will be determined.
[0038] The optical computing devices described herein utilize
electromagnetic radiation to perform calculations, as opposed to the hardwired
circuits of conventional electronic processors. When electromagnetic radiation
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interacts with a material of interest, unique physical and chemical
information
about the material of interest may be encoded in the electromagnetic radiation
that is reflected from, transmitted through, or radiated from the material of
interest. This information is often referred to as the spectral "fingerprint"
of the
material of interest. The optical computing devices described herein are
capable
of extracting the information of the spectral fingerprint of multiple
characteristics
of interest, and converting that information into a detectable output
regarding
the overall properties of material of interest. That is, through suitable
configurations of the optical computing devices, electromagnetic radiation
associated with characteristics of interest can be separated from
electromagnetic
radiation associated with all other analytes of the material of interest in
order to
estimate the properties of the material of interest in real-time or near real-
time.
[0039] The processing elements used in the exemplary optical
computing devices described herein may be characterized as integrated
computational elements (ICE). Each ICE is capable of distinguishing
electromagnetic radiation related to the characteristic of interest from
electromagnetic radiation related to other substances. Referring to FIG. 1,
illustrated is an exemplary ICE 100 suitable for use in the optical computing
devices used in the systems and methods described herein. As illustrated, the
ICE 100 may include a plurality of alternating layers 102 and 104, such as
silicon (Si) and 5i02 (quartz), respectively. In general, these layers 102,
104
consist of materials whose index of refraction is high and low, respectively.
Other examples might include niobia and niobium, germanium and gernnania,
MgF, SiOx, and other high and low index materials known in the art. The layers
102, 104 may be strategically deposited on an optical substrate 106. In some
embodiments, the optical substrate 106 is BK-7 optical glass. In other
embodiments, the optical substrate 106 may be another type of optical
substrate, such as quartz, sapphire, silicon, germanium, zinc selenide, zinc
sulfide, or various plastics such as polycarbonate, polynnethylnnethacrylate
(PMMA), polyvinylchloride (PVC), diamond, ceramics, combinations thereof, and
the like.
[0040] At the opposite end (e.g., opposite the optical substrate 106 in
FIG. 1), the ICE 100 may include a layer 108 that is generally exposed to the
environment of the device or installation. The number of layers 102, 104 and
the thickness of each layer 102, 104 are determined from the spectral
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attributes acquired from a spectroscopic analysis of a characteristic of the
material of interest using a conventional spectroscopic instrument. The
spectrum
of interest of a given characteristic of interest typically includes any
number of
different wavelengths. It should be understood that the exemplary ICE 100 in
FIG. 1 does not in fact represent any particular characteristic of a given
material
of interest, but is provided for purposes of illustration only. Consequently,
the
number of layers 102, 104 and their relative thicknesses, as shown in FIG. 1,
bear no correlation to any particular characteristic of a given material of
interest.
Nor are the layers 102, 104 and their relative thicknesses necessarily drawn
to
scale, and therefore should not be considered limiting of the present
disclosure.
Moreover, those skilled in the art will readily recognize that the materials
that
make up each layer 102, 104 (e.g., Si and 5i02) may vary, depending on the
application, cost of materials, and/or applicability of the material to the
given
material of interest.
[0041] In some embodiments, the material of each layer 102, 104 can
be doped or two or more materials can be combined in a manner to achieve the
desired optical characteristic. In addition to solids, the exemplary ICE 100
may
also contain liquids and/or gases, optionally in combination with solids, in
order
to produce a desired optical characteristic. In the case of gases and liquids,
the
ICE 100 can contain a corresponding vessel (not shown), which houses the
gases or liquids. Exemplary variations of the ICE 100 may also include
holographic optical elements, gratings, piezoelectric, light pipe, digital
light pipe
(DLP), variable optical attenuators, and/or acousto-optic elements, for
example,
that can create transmission, reflection, and/or absorptive properties of
interest.
[0042] The multiple layers 102, 104 exhibit different refractive indices.
By properly selecting the materials of the layers 102, 104 and their relative
thickness and spacing, the ICE 100 may be configured to selectively
pass/reflect/refract predetermined fractions of electromagnetic radiation at
different wavelengths. Each wavelength is given a predetermined weighting or
loading factor. The thickness and spacing of the layers 102, 104 may be
determined using a variety of approximation methods from the spectrograph of
the characteristic of interest. These methods may include inverse Fourier
transform (IFT) of the optical transmission spectrum and structuring the ICE
100 as the physical representation of the IFT. The approximations convert the
IFT into a structure based on known materials with constant refractive
indices.
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Further information regarding the structures and design of exemplary
integrated
computational elements (also referred to as multivariate optical elements) is
provided in Applied Optics, Vol. 35, pp. 5484-5492 (1996) and Vol. 129, pp.
2876-2893, which is hereby incorporated by reference.
[0043] The weightings that the layers 102, 104 of the ICE 100 apply
at each wavelength are set to the regression weightings described with respect
to a known equation, or data, or spectral signature. Briefly, the ICE 100 may
be
configured to perform the dot product of the input light beam into the ICE 100
and a desired loaded regression vector represented by each layer 102, 104 for
each wavelength. As a result, the output light intensity of the ICE 100 is
related
to the characteristic of interest. Further details regarding how the exemplary
ICE
100 is able to distinguish and process electromagnetic radiation related to
the
characteristic of interest are described in U.S. Pat. Nos. 6,198,531 entitled
"Optical Computational System;" 6,529,276 entitled "Optical Computational
System;" and 7,920,258 entitled "Optical Analysis System and Elements to
Isolate Spectral Region;" previously incorporated herein by reference.
[0044] Referring now to FIG. 2, illustrated is a block diagram that non-
mechanistically illustrates how an optical computing device 200 is able to
distinguish electromagnetic radiation related to a characteristic of interest
from
other electromagnetic radiation. As shown in FIG. 2, after being illuminated
with
incident electromagnetic radiation, a material of interest 202 (e.g., a cement
sheath, a displacement composition, or an analyte thereof) produces an output
of electromagnetic radiation (e.g., sample-interacted light), some of which is
electromagnetic radiation 204 corresponding to the characteristic of interest
and
some of which is background electromagnetic radiation 206 corresponding to
other characteristics of the material of interest 202.
[0045] Although not specifically shown, one or more spectral elements
may be employed in the device 200 in order to restrict the optical wavelengths
and/or bandwidths of the system and thereby eliminate unwanted
electromagnetic radiation existing in wavelength regions that have no
importance. Such spectral elements can be located anywhere along the optical
train, but are typically employed directly after the light source, which
provides
the initial electromagnetic radiation. Various configurations and applications
of
spectral elements in optical computing devices may be found in commonly
owned U.S. Pat. Nos. 6,198,531 entitled "Optical Computational System;"
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6,529,276 entitled "Optical Computational System;" 7,123,844 entitled "Optical
Computational System;" 7,834,999 "Optical Analysis System and Optical Train;"
7,911,605 entitled "Multivariate Optical Elements for Optical Analysis
System;"
7,920,258 entitled "Optical Analysis System and Elements to Isolate Spectral
Region;" and 8,049,881 entitled "Optical Analysis System and Methods for
Operating Multivariate Optical Elements in a Normal Incidence Orientation;"
and
U.S. Pat. App. Serial Nos. 12/094,460 entitled "Methods of High-Speed
Monitoring Based on the Use of Multivariate Optical Elements;" 12/094,465
entitled "Optical Analysis System for Dynamic Real-Time Detection and
Measurement;" and 13/456,467 entitled "Imaging Systems for Optical
Computing Devices;" incorporated herein by reference, as indicated above.
[0046] The beams of electromagnetic radiation 204,206 impinge upon
the optical computing device 200, which contains an exemplary ICE 208
therein. In the illustrated embodiment, the ICE 208 may be configured to
produce optically interacted light, for example, transmitted optically
interacted
light 210 and reflected optically interacted light 214. In operation, the ICE
208
may be configured to distinguish the electromagnetic radiation 204 from the
background electromagnetic radiation 206.
[0047] The transmitted optically interacted light 210, which may be
related to the characteristic of interest of the material of interest 202, may
be
conveyed to a detector 212 for analysis and quantification. In some
embodiments, the detector 212 is configured to produce an output signal in the
form of a voltage that corresponds to the particular characteristic of the
material
of interest 202. In at least one embodiment, the signal produced by the
detector
212 and the characteristic of a material of interest 202 (e.g., the
concentration
of an analyte, pH, porosity, or the like) may be directly proportional. In
other
embodiments, the relationship may be a polynomial function, an exponential
function, and/or a logarithmic function. The reflected optically interacted
light
214, which may be related to other characteristics of the material of interest
202, can be directed away from detector 212. In alternative configurations,
the
ICE 208 may be configured such that the reflected optically interacted light
214
can be related to the characteristic of interest, and the transmitted
optically
interacted light 210 can be related to other characteristics in the material
of
interest 202.
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[0048] In some embodiments, a second detector 216 can be present
and arranged to detect the reflected optically interacted light 214. In other
embodiments, the second detector 216 may be arranged to detect the
electromagnetic radiation 204,206 derived from the material of interest 202 or
electromagnetic radiation directed toward or before the material of interest
202.
Without limitation, the second detector 216 may be used to detect radiating
deviations stemming from an electromagnetic radiation source (not shown),
which provides the electromagnetic radiation (i.e., light) to the device 200.
For
example, radiating deviations can include, but are not limited to, intensity
fluctuations in the electromagnetic radiation, interferent fluctuations (e.g.,
dust
or other interferents passing in front of the electromagnetic radiation
source),
coatings on windows included with the optical computing device 200,
combinations thereof, or the like. In some embodiments, a beam splitter (not
shown) can be employed to split the electromagnetic radiation 204,206, and
the transmitted or reflected electromagnetic radiation can then be directed to
one or more ICE 208. That is, in such embodiments, the ICE 208 does not
function as a type of beam splitter, as depicted in FIG. 2, and the
transmitted or
reflected electromagnetic radiation simply passes through the ICE 208, being
computationally processed therein, before travelling to the detector 212.
[0049] The characteristic(s) of the material of interest 202 being
analyzed using the optical computing device 200 can be further processed
and/or analyzed computationally to provide additional information regarding
the
properties of the material of interest 202. In some embodiments, the
characteristic of the material of interest 202 can be used to analyze for
nnicroannulus indicators.
[0050] In some embodiments, the characteristics of the material of
interest determined using the optical computing devices 200 can be associated
with a tinnestannp. A tinnestannp may be useful in reviewing and analyzing the
history of the characteristic of interest, which may be of added value in
determining if a nnicroannulus has formed. In some embodiments, the
characteristics, optionally tinnestannped, of the material of interest
determined
using the optical computing devices 200 can be fed into an algorithm operating
under computer control. The algorithm may be configured to make predictions
on the presence, formation timeline, and/or extent of a nnicroannulus. In some
embodiments, the algorithm can produce an output that is readable by an
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operator who can manually take appropriate action, like initiation of a
remedial
operation, if needed, based upon the output.
[0051] The algorithm can be part of an artificial neural network
configured to use each detected characteristic of interest in order to
evaluate the
overall property(s) of the material of interest 202 and determine if a
nnicroannulus has formed, and in some embodiments, the extent of
nnicroannulus formation. Illustrative but non-limiting artificial neural
networks
are described in commonly owned U.S. Pat. App. No. 11/986,763 entitled
"Determining Stimulation Design Parameters Using Artificial Neural Networks
Optimized with a Genetic Algorithm," which is incorporated herein by
reference.
It is to be recognized that an artificial neural network can be trained using
samples of substances having known characteristics, and thereby generating a
virtual library. As the virtual library available to the artificial neural
network
becomes larger, the neural network can become more capable of accurately
determining nnicroannulus formation, and optionally the extent of
nnicroannulus
formation.
[0052] It is recognized that the various embodiments herein directed to
computer control and artificial neural networks, including various blocks,
modules, elements, components, methods, and algorithms, can be implemented
using computer hardware, software, combinations thereof, and the like. To
illustrate this interchangeability of hardware and software, various
illustrative
blocks, modules, elements, components, methods, and algorithms have been
described generally in terms of their functionality. Whether such
functionality is
implemented as hardware or software will depend upon the particular
application
and any imposed design constraints. For at least this reason, it is to be
recognized that one of ordinary skill in the art can implement the described
functionality in a variety of ways for a particular application. Further,
various
components and blocks can be arranged in a different order or partitioned
differently, for example, without departing from the scope of the embodiments
expressly described.
[0053] Computer hardware used to implement the various illustrative
blocks, modules, elements, components, methods, and algorithms described
herein can include a processor configured to execute one or more sequences of
instructions, programming stances, or code stored on a non-transitory,
computer-readable medium. The processor can be, for example, a general
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purpose microprocessor, a nnicrocontroller, a digital signal processor, an
application specific integrated circuit, a field programmable gate array, a
programmable logic device, a controller, a state machine, a gated logic,
discrete
hardware components, an artificial neural network, or any like suitable entity
that can perform calculations or other manipulations of data. In some
embodiments, computer hardware can further include elements, for example, a
memory (e.g., random access memory (RAM), flash memory, read only memory
(ROM), programmable read only memory (PROM), erasable read only memory
(EPROM)), registers, hard disks, removable disks, CD-ROMS, DVDs, or any other
like suitable storage device or medium.
[0054] Executable sequences described herein can be implemented with
one or more sequences of code contained in a memory. In some embodiments,
such code can be read into the memory from another machine-readable
medium. Execution of the sequences of instructions contained in the memory
can cause a processor to perform the process steps described herein. One or
more processors in a multi-processing arrangement can also be employed to
execute instruction sequences in the memory. In addition, hard-wired circuitry
can be used in place of or in combination with software instructions to
implement various embodiments described herein. Thus, the present
embodiments are not limited to any specific combination of hardware and/or
software.
[0055] As used herein, a machine-readable medium will refer to any
medium that directly or indirectly provides instructions to a processor for
execution. A machine-readable medium can take on many forms including, for
example, non-volatile media, volatile media, and transmission media. Non-
volatile media can include, for example, optical and magnetic disks. Volatile
media can include, for example, dynamic memory. Transmission media can
include, for example, coaxial cables, wire, fiber optics, and wires that form
a
bus. Common forms of machine-readable media can include, for example, floppy
disks, flexible disks, hard disks, magnetic tapes, other like magnetic media,
CD-
ROMs, DVDs, other like optical media, punch cards, paper tapes and like
physical
media with patterned holes, RAM, ROM, PROM, EPROM, and flash EPROM.
[0056] In some embodiments, the data collected, and optionally
analyzed, using the optical computing devices described herein can be
transmitted from the analysis point within the wellbore to the surface in real-
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time or near real-time. Transmitting data real-time or near real-time may be
undertaken using wired means (e.g., fiber optics) or wireless means (e.g.,
telemetry).
[0057] In some embodiments, the data collected, and optionally
analyzed, using the optical computing devices described herein can be stored
in,
for example, an on-board memory or the like, and then subsequently
downloaded to an external processing device for consideration. Downloading
data may be transmitted by wired means (e.g., fiber optics) or wireless means
(e.g., telemetry). In some embodiments, downloading may be achieved by
running a tool through at least a portion of the wellbore such that the tool
wirelessly downloads the data to an external processing device.
[0058] In some embodiments, the data collected, and optionally
analyzed, can be communicated (wired or wirelessly) to a remote location by a
communication system (e.g., satellite communication or wide area network
communication) for further analysis. The communication system can also allow
remote monitoring and operation of a process to take place. Automated control
with a long-range communication system can further facilitate the performance
of remote job operations. In particular, an artificial neural network can be
used
in some embodiments to facilitate the performance of remote job operations
(e.g., remedial operations to repair a nnicroannulus). That is, remote job
operations can be conducted automatically in some embodiments. In other
embodiments, however, remote job operations can occur under direct operator
control, where the operator is not at the job site.
[0059] In some embodiments, the data collected using the optical
computing devices can be archived along with data associated with operational
parameters being logged at a job site. Evaluation of job performance can then
be assessed and improved for future operations or such information can be used
to design subsequent operations.
[0060] Referring now to FIG. 3A, illustrated is an exemplary system
300 for monitoring a material of interest (e.g., a cement sheath 302 and/or a
displacement composition 350) for an indicator of a nnicroannulus 352 having
formed, according to one or more embodiments. In the illustrated embodiment,
the cement sheath 302 may be disposed about and in contact with an exterior
surface 340 of a casing 304. While FIG. 3A is depicted as a vertical wellbore,
it
should be appreciated that the wellbore may be arranged substantially
vertical,
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substantially horizontal, or any directional configuration therebetween,
without
departing from the scope of the disclosure. The system 300 may include at
least
one optical computing device 306, which may be similar in some respects to the
optical computing device 200 of FIG. 2, and therefore may be best understood
with reference thereto.
[0061] Referring now to FIG. 3B, with continued reference to FIG. 3A,
the optical computing device 306 may be housed within a housing 342
configured to substantially protect the internal components of the optical
computing device 306 from damage or contamination from the external
environment. In some embodiments, the housing may operate to mechanically
couple the device 306 to the casing 304 with, for example, mechanical
fasteners, brazing or welding techniques, adhesives, magnets, combinations
thereof or the like. In operation, the housing 342 may be designed to
withstand
the pressures that may be experienced within or outside the casing 304 and
thereby provide a fluid tight seal against external contamination. As
described in
greater detail below, the optical computing device 306 may be useful in
determining a characteristic of the material of interest (e.g., the cement
sheath
302 and/or a displacement composition 350).
[0062] By way of nonlinniting example, because some chemicals may
deteriorate a cement composition, monitoring the cement sheath 302 for the
characteristic of porosity may help determine if a nnicroannulus 352 has
formed
and provide an opportunity to repair the cement sheath 302 with a remedial
operation.
[0063] By way of another nonlinniting example, the optical computing
device 306 may be configured to measure a characteristic of an oleaginous
fluid,
an example of the displacement composition 350. As such, after formation and
setting of the casing 304, the optical computing device 306 may collect data
indicating that the oleaginous fluid is not present. Then, after some time has
passed, the optical computing device 306 may return a positive measurement
for the characteristic of the oleaginous fluid, thereby indicating the
possible
formation of the nnicroannulus 352. The optical computing device 306 may be
configured to inform the user (either wired or wirelessly) of the positive
measurement. After the user has been alerted to the positive measurement,
appropriate corrective action (e.g., a remedial operation) may be taken, if
appropriate. Further, in some embodiments, the optical computing device 306
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may be used after the appropriate corrective action so as to determine the
efficacy of such action. For example, the optical computing device 306 may
again be configured to collect data indicating that the oleaginous fluid is
not
present.
[0064] In some embodiments, the device 306 may include an
electromagnetic radiation source 308 configured to emit or otherwise generate
electromagnetic radiation 310. The electromagnetic radiation source 308 may
be any device capable of emitting or generating electromagnetic radiation, as
defined herein. For example, the electromagnetic radiation source 308 may be a
light bulb, a light emitting device (LED), a laser, a blackbody, a photonic
crystal,
an X-Ray source, combinations thereof, or the like. In some embodiments, a
lens 312 may be configured to collect or otherwise receive the electromagnetic
radiation 310 and direct a beam 314 of electromagnetic radiation 310 toward
the material of interest (e.g., the cement sheath 302 and/or the displacement
composition 350). The lens 312 may be any type of optical device configured to
transmit or otherwise convey the electromagnetic radiation 310 as desired. For
example, the lens 312 may be a normal lens, a Fresnel lens, a diffractive
optical
element, a holographic graphical element, a mirror (e.g., a focusing mirror),
a
type of collimator, or any other electromagnetic radiation transmitting device
known to those skilled in art. In other embodiments, the lens 312 may be
omitted from the device 306 and the electromagnetic radiation 310 may instead
be directed toward the material of interest (e.g., the cement sheath 302
and/or
the displacement composition 350) directly from the electromagnetic radiation
source 308.
[0065] In one or more embodiments, the device 306 may also include a
sampling window 316 arranged adjacent to or otherwise in contact with the
material of interest (e.g., the cement sheath 302 and/or the displacement
composition 350) for detection purposes. The sampling window 316 may be
made from a variety of transparent, rigid or semi-rigid materials that are
configured to allow transmission of the electromagnetic radiation 310
therethrough. For example, the sampling window 316 may be made of, but is
not limited to, glasses, plastics, semi-conductors, crystalline materials,
polycrystalline materials, hot or cold-pressed powders, combinations thereof,
or
the like. In order to remove ghosting or other imaging issues resulting from
reflectance on the sampling window 316, the system 300 may employ one or
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more internal reflectance elements ("IRE"), such as those described in co-
owned
U.S. Pat. No. 7,697,141 entitled "In Situ Optical Computational Fluid Analysis
System and Method," and/or one or more imaging systems, such as those
described in co-owned U.S. Pat. App. Ser. No. 13/456,467 entitled "Imaging
Systems for Optical Computing Devices," the contents of each hereby being
incorporated by reference.
[0066] After passing through the sampling window 316, the
electromagnetic radiation 310 impinges upon and optically interacts with the
material of interest (e.g., the cement sheath 302 and/or the displacement
composition 350). As a result, optically interacted radiation 318 is generated
by
and reflected from the material of interest (e.g., the cement sheath 302
and/or
the displacement composition 350). Those skilled in the art, however, will
readily recognize that alternative variations of the device 306 may allow the
optically interacted radiation 318 to be generated by being transmitted,
scattered, diffracted, absorbed, emitted, or re-radiated by and/or from the
material of interest (e.g., the cement sheath 302 and/or the displacement
composition 350), without departing from the scope of the disclosure.
[0067] The optically interacted radiation 318 generated by the
interaction with the material of interest (e.g., the cement sheath 302 and/or
the
displacement composition 350) may be directed to or otherwise be received by
an ICE 320 arranged within the device 306. The ICE 320 may be a spectral
component substantially similar to the ICE 100 described above with reference
to FIG. 1. Accordingly, in operation the ICE 320 may be configured to receive
the optically interacted radiation 318 and produce modified electromagnetic
radiation 322 corresponding to a particular characteristic of the material of
interest (e.g., the cement sheath 302 and/or the displacement composition
350). In particular, the modified electromagnetic radiation 322 is
electromagnetic radiation that has optically interacted with the ICE 320,
whereby an approximate mimicking of the regression vector corresponding to
the characteristic of the material of interest (e.g., the cement sheath 302
and/or
the displacement composition 350) is obtained.
[0068] It should be noted that, while FIG. 38 depicts the ICE 320 as
receiving reflected electromagnetic radiation from the material of interest
(e.g.,
the cement sheath 302 and/or the displacement composition 350), the ICE 320
may be arranged at any point along the optical train of the device 306,
without
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departing from the scope of the disclosure. For example, in one or more
embodiments, the ICE 320 (as shown in dashed) may be arranged within the
optical train prior to the sampling window 316 and equally obtain
substantially
the same results. In other embodiments, the sampling window 316 may serve a
dual purpose as both a transmission window and the ICE 320 (i.e., a spectral
components). In yet other embodiments, the ICE 320 may generate the
modified electromagnetic radiation 322 through reflection, instead of
transmission therethrough.
[0069] Moreover, while only one ICE 320 is shown in the device 306,
embodiments are contemplated herein which include the use of at least two ICE
components in the device 306 configured to cooperatively determine the
characteristic of the material of interest (e.g., the cement sheath 302 and/or
the
displacement composition 350). For example, two or more ICE components may
be arranged in series or parallel within the device 306 and configured to
receive
the optically interacted radiation 318 and thereby enhance sensitivities and
detector limits of the device 306. In other embodiments, two or more ICE may
be arranged on a movable assembly, such as a rotating disc or an oscillating
linear array, which moves such that the individual ICE components are able to
be exposed to or otherwise optically interact with electromagnetic radiation
for a
distinct brief period of time. The two or more ICE components in any of these
embodiments may be configured to be either associated or disassociated with
the characteristic of the material of interest (e.g., the cement sheath 302
and/or
the displacement composition 350). In other embodiments, the two or more ICE
may be configured to be positively or negatively correlated with the
characteristic of the material of interest (e.g., the cement sheath 302 and/or
the
displacement composition 350). These optional embodiments employing two or
more ICE components are further described in co-pending U.S. Pat. App. Ser.
Nos. 13/456,264 entitled "Methods and Devices for Optically Determining a
Characteristic of a Substance," 13/456,405 entitled "Methods and Devices for
Optically Determining A Characteristic of a Substance," 13/456,302 entitled
"Methods and Devices for Optically Determining A Characteristic of a
Substance,"
and 13/456,327 entitled "Methods and Devices for Optically Determining A
Characteristic of a Substance," the contents of which are hereby incorporated
by
reference in their entireties.
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[0070] In some embodiments, it may be desirable to monitor more than
one characteristic of interest at a time using the device 306. In such
embodiments, various configurations for multiple ICE components can be used,
where each ICE component is configured to detect a particular and/or distinct
characteristic of interest. In some embodiments, the characteristic can be
analyzed sequentially using multiple ICE components that are provided a single
beam of electromagnetic radiation being reflected from or transmitted through
the material of interest (e.g., the cement sheath 302 and/or the displacement
composition 350). In some embodiments, as briefly mentioned above, multiple
ICE components can be arranged on a rotating disc, where the individual ICE
components are only exposed to the beam of electromagnetic radiation for a
short time. Advantages of this approach can include the ability to analyze
multiple characteristics of the material of interest (e.g., the cement sheath
302
and/or the displacement composition 350) using a single optical computing
device and the opportunity to assay additional characteristics of interest
simply
by adding additional ICE components to the rotating disc. In various
embodiments, the rotating disc can be turned at a frequency of about 10 RPM to
about 30,000 RPM such that each characteristic of the material of interest
(e.g.,
the cement sheath 302 and/or the displacement composition 350) is measured
rapidly. In some embodiments, these values can be averaged over an
appropriate time domain (e.g., about 1 millisecond to about 1 hour) to more
accurately determine the characteristic of the material of interest (e.g., the
cement sheath 302 and/or the displacement composition 350).
[0071] In other embodiments, multiple optical computing devices can
be placed in at least one location along the casing 304, where each optical
computing device contains a unique ICE component that is configured to detect
a particular characteristic of the material of interest (e.g., the cement
sheath
302 and/or the displacement composition 350). In such embodiments, a beam
splitter can divert a portion of the electromagnetic radiation being reflected
by or
emitted from the material of interest (e.g., the cement sheath 302 and/or the
displacement composition 350) and into each optical computing device. Each
optical computing device, in turn, can be coupled to a corresponding detector
or
detector array that is configured to detect and analyze an output of
electromagnetic radiation from the respective optical computing device.
Parallel
configurations of optical computing devices can be particularly beneficial for
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applications that require low power inputs and/or no moving parts, e.g., long-
term monitoring of the health of the cement sheath.
[0072] Those skilled in the art will appreciate that any of the foregoing
configurations can further be used in combination with a series configuration
in
any of the present embodiments. For example, two optical computing devices
having a rotating disc with a plurality of ICE components arranged thereon can
be placed in series for performing an analysis at a single location along the
length of the casing 304. Likewise, multiple detection stations, each
containing
optical computing devices in parallel, can be placed in series for performing
a
similar analysis.
[0073] With continued reference to FIG. 3B, the modified
electromagnetic radiation 322 generated by the ICE 320 may subsequently be
conveyed to a detector 324 for quantification of the signal. The detector 324
may be any device capable of detecting electromagnetic radiation, and may be
generally characterized as an optical transducer. In some embodiments, the
detector 324 may be, but is not limited to, a thermal detector such as a
thermopile or photoacoustic detector, a semiconductor detector, a piezo-
electric
detector, a charge coupled device (CCD) detector, a video or array detector, a
split detector, a photon detector (e.g., a photonnultiplier tube),
photodiodes,
combinations thereof, or the like, or other detectors known to those skilled
in
the art.
[0074] In some embodiments, the detector 324 may be configured to
produce an output signal 326 in real-time or near real-time in the form of a
voltage (or current) that corresponds to the particular characteristic of the
material of interest (e.g., the cement sheath 302 and/or the displacement
composition 350). The voltage returned by the detector 324 is essentially the
dot product of the optical interaction of the optically interacted radiation
318
with the respective ICE 320 as a function of a characteristic the material of
interest (e.g., the cement sheath 302 and/or the displacement composition
350). As such, the output signal 326 produced by the detector 324 and the
characteristic of the material of interest (e.g., the cement sheath 302 and/or
the
displacement composition 350) may be related, for example, directly
proportional. In other embodiments, however, the relationship may correspond
to a polynomial function, an exponential function, a logarithmic function,
and/or
a combination thereof.
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[0075] In some embodiments, the device 306 may include a second
detector 328, which may be similar to the first detector 324 in that it may be
any device capable of detecting electromagnetic radiation. Similar to the
second
detector 216 of FIG. 2, the second detector 328 of FIG. 38 may be used to
detect radiating deviations stemming from the electromagnetic radiation source
308. Undesirable radiating deviations can occur in the intensity of the
electromagnetic radiation 310 due to a wide variety of reasons and potentially
causing various negative effects on the device 306. These negative effects can
be particularly detrimental for measurements taken over a period of time. In
some embodiments, radiating deviations can occur as a result of a build-up of
film or material on the sampling window 316 which has the effect of reducing
the amount and quality of light ultimately reaching the first detector 324.
Without proper compensation, such radiating deviations could result in false
readings and the output signal 326 would no longer be primarily or accurately
related to the characteristic of interest.
[0076] To compensate for these types of undesirable effects, the
second detector 328 may be configured to generate a compensating signal 330
generally indicative of the radiating deviations of the electromagnetic
radiation
source 308, and thereby normalize the output signal 326 generated by the first
detector 324. As illustrated, the second detector 328 may be configured to
receive a portion of the optically interacted radiation 318 via a
beannsplitter 332
in order to detect the radiating deviations. In other embodiments, however,
the
second detector 328 may be arranged to receive electromagnetic radiation from
any portion of the optical train in the device 306 in order to detect the
radiating
deviations, without departing from the scope of the disclosure.
[0077] In some applications, the output signal 326 and the
compensating signal 330 may be conveyed to or otherwise received by a signal
processor 334 communicably coupled to both the detectors 320,328. The signal
processor 334 may be a computer including a non-transitory machine-readable
medium, and may be configured to computationally combine the compensating
signal 330 with the output signal 326 in order to normalize the output signal
326 in view of any radiating deviations detected by the second detector 328.
In
some embodiments, computationally combining the output and compensating
signals 326,330 may entail computing a ratio of the two signals 326,330. For
example, the characteristic of a material of interest or the magnitude of each
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characteristic determined using the optical computing device 306 can be fed
into
an algorithm run by the signal processor 334.
[0078] In real-time or near real-time, the signal processor 334 may be
configured to provide a resulting output signal 336 corresponding to a
characteristic of the material of interest (e.g., the cement sheath 302 and/or
the
displacement composition 350). The resulting output signal 336 may be
readable by an operator who can consider the results and make proper
adjustments or take appropriate action, if needed, based upon the measured
characteristic of the material of interest (e.g., the cement sheath 302 and/or
the
displacement composition 350). In some embodiments, the resulting signal
output 328 may be conveyed, either wired or wirelessly, to the user for
consideration. In other embodiments, the resulting output signal 336 may be
recognized by the signal processor 334 as being within or without a
predetermined or preprogrammed range that indicates the possible formation of
the nnicroannulus 352. If the resulting output signal 336 exceeds the
predetermined or preprogrammed range of operation, the signal processor 334
may be configured to alert the user of a potential formation of the
nnicroannulus
352 so appropriate corrective action (e.g., a remedial operation) may be
taken.
[0079] By way of nonlinniting example, in some embodiments, the
device 306 may be configured to measure water concentration. As water is
present, to some degree, in cement compositions, a threshold water
concentration may be set at a level similar to that of a set cement
compositions.
However, when the nnicroannulus 352 forms and is infiltrated by a displacement
composition 350 that comprises water, the device 306 may detect water above
the threshold concentration and alter a user to the potential formation of the
nnicroannulus 352.
[0080] Referring now to FIG. 4, illustrated is an exemplary system 400
for monitoring a fluid according to one or more embodiments. In the
illustrated
embodiment, the system 400 includes a plurality of optical computing devices
406,406',406" coupled to a casing 404 in series along the length of the casing
404. Each optical computing device 406,406',406" may be similar to the
optical computing device 306 of FIGS. 3A and 3B, and therefore will not be
described again in detail. Such a plurality of optical computing devices
406,406',406" may be advantageous to monitor multiple locations along a
casing for nnicroannulus formation. As with the embodiments discussed above,
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the plurality of optical computing devices 406,406',406" may independently
include multiple ICE components and be configured to measure one or more
characteristics of interest and analyzed for indicators of nnicroannulus
formation.
[0081] In some embodiments, each of the plurality of optical computing
devices 406,406',406" may be designed to analyze the same or different
characteristics of interest. For example, optical computing device 406 can be
configured to measure a concentration of an analyte (or plurality of analytes)
found in formation fluids where an increase in concentration may indicate
formation fluid infiltration and indicate nnicroannulus formation; optical
computing device 406' can be configured to analyze for a characteristic of the
cement sheath 402 where a decrease in signal could indicate nnicroannulus
formation (e.g., because of pull-away from the device and/or infiltration of a
displacement composition between the cement sheath 402 and the optical
computing device 406'); and optical computing device 406" can be configured
to measure a concentration of an analyte (or plurality of analytes) found in a
wellbore fluid (e.g., a concentration of an analyte like a tracer or probe
analyte)
where an increase in concentration may indicate wellbore fluid infiltration
and
indicate nnicroannulus formation.
[0082] Those skilled in the art will readily appreciate the various and
numerous applications that the systems 300 and 400, and alternative
configurations thereof, may be suitably used with. For example, some
embodiments of the present disclosure may involve measuring at least one
characteristic of interest of a cement sheath with the optical computing
devices
generally disclosed herein. In other embodiments, the optical computing
devices
may be configured to measure or otherwise monitor the presence or absence of
a displacement composition (e.g., a formation fluid or a wellbore fluid) which
may interpose the outer circumferential surface of a casing and the cement
sheath. As generally described above, the detection of a displacement
composition may indicate the formation of a nnicroannulus between the outer
circumferential surface of a casing and the cement sheath. To achieve such
detection, the optical computing devices may be disposed in any suitable
location including, but not limited to, relative to an exterior surface of a
casing,
relative to an exterior surface of a collar, relative to a centralizer, or
relative to
an exterior surface of a casing shoe.
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[0083] In some embodiments, when a nnicroannulus indicated by the
methods and/or systems described herein, one or more remedial operations
(e.g., squeeze operations) to reverse the effects of the nnicroannulus may be
initiated. In some embodiments, the optical computing device may be used to
analyze for efficacy of the rennediation operation, e.g., a change in output
signal
that indicates cement has been properly placed in the nnicroannulus. For
example, optical computing devices configured to measure a characteristic of
the
cement sheath may have a signal decrease when the cement sheath pulls away
from the casing. Then, after a remedial operation where cement is placed in
the
nnicroannulus, the output signal may increase. In another example, optical
computing devices configured to measure a characteristic of a displacement
composition may have a signal increase when the displacement composition
infiltrates between the cement sheath and the casing Then, after a remedial
operation where cement is placed in the nnicroannulus, the output signal may
decrease.
[0084] It should also be noted that the various drawings provided
herein are not necessarily drawn to scale nor are they, strictly speaking,
depicted as optically correct as understood by those skilled in optics.
Instead,
the drawings are merely illustrative in nature and used generally herein in
order
to supplement understanding of the systems and methods provided herein.
Indeed, while the drawings may not be optically accurate, the conceptual
interpretations depicted therein accurately reflect the exemplary nature of
the
various embodiments disclosed.
[0085] Therefore, the present invention is well adapted to attain the
ends and advantages mentioned as well as those that are inherent therein. The
particular embodiments disclosed above are illustrative only, as the present
invention may be modified and practiced in different but equivalent manners
apparent to those skilled in the art having the benefit of the teachings
herein.
Furthermore, no limitations are intended to the details of construction or
design
herein shown, other than as described in the claims below. It is therefore
evident that the particular illustrative embodiments disclosed above may be
altered, combined, or modified and all such variations are considered within
the
scope and spirit of the present invention. The invention illustratively
disclosed
herein suitably may be practiced in the absence of any element that is not
specifically disclosed herein and/or any optional element disclosed herein.
While
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compositions and methods are described in terms of "comprising," "containing,"
or "including" various components or steps, the compositions and methods can
also "consist essentially of" or "consist of" the various components and
steps. All
numbers and ranges disclosed above may vary by some amount. Whenever a
numerical range with a lower limit and an upper limit is disclosed, any number
and any included range falling within the range is specifically disclosed. In
particular, every range of values (of the form, "from about a to about b," or,
equivalently, "from approximately a to b," or, equivalently, "from
approximately
a-b") disclosed herein is to be understood to set forth every number and range
encompassed within the broader range of values. Also, the terms in the claims
have their plain, ordinary meaning unless otherwise explicitly and clearly
defined
by the patentee. Moreover, the indefinite articles "a" or "an," as used in the
claims, are defined herein to mean one or more than one of the element that it
introduces. If there is any conflict in the usages of a word or term in this
specification and one or more patent or other documents that may be
incorporated herein by reference, the definitions that are consistent with
this
specification should be adopted.
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