FLUID ANALYSIS SYSTEM WITH INTEGRATED COMPUTATION ELEMENT
FORMED USING ATOMIC LAYER DEPOSITION
BACKGROUND
Integrated Computation Elements (ICEs) have been used to perform optical analysis
of fluids and material composition of complex samples. ICEs can be constructed by
providing a series of layers having thicknesses and reflectivities designed to interfere
constructively or destructively at desired wavelengths to provide an encoded pattern
specifically for the purpose of interacting with light and providing an optical computational
operation which allows for the prediction of a chemical or material property. The
construction method for ICEs is similar to the construction method for an optical interference
filter. For a complex waveform, an ICE constructed by conventional interference filter means
may require a very large number of layers. In addition to being complicated to fabricate, such
constructed ICEs may fail to perform optimally in harsh environments. For example, ICEs
having a very large number of layers, or with individual layers that are thick relative to the
film stack thickness, or with extremely tight tolerances, can have their prediction
performance adversely affected by the temperature, shock, and vibration conditions in the
downhole environment of a drilling setup for hydrocarbon exploration or extraction.
Efforts have been made to design and manufacture simplified ICEs that can provide
complex spectral characteristics with a significantly reduced number of layers or layer
thicknesses. However, many ICE designs (the recipe of layers and thicknesses to achieve a
desired chemical prediction) are discarded due to the limitations and variance of available
deposition techniques such as reactive magnetron sputtering (RMS).
BRIEF DESCRIPTION OF THE DRAWINGS
Accordingly, there are disclosed herein fluid analysis systems with one or more
optical path components formed or modified using atomic layer deposition (ALD). In the
drawings:
FIG. 1 shows an illustrative fluid analysis system.
FIG. 2 shows illustrative layers of an ALD-based integrated computation element
(ICE).
FIG. 3 shows a target transmission spectra and an intermediate model transmission
spectra for an ALD-based ICE.
FIG. 4 shows an illustrative logging while drilling (LWD) environment.
FIG. 5 shows an illustrative wireline logging environment.
FIG. 6 shows an illustrative computer system for managing logging operations.
FIG. 7 shows a flowchart of an illustrative ICE fabrication method.
FIG. 8 shows a flowchart of an illustrative fluid analysis system fabrication method.
FIG. 9 shows a flowchart of an illustrative fluid analysis method.
The drawings show illustrative embodiments that will be described in detail.
However, the description and accompanying drawings are not intended to limit the invention
to the illustrative embodiments, but to the contrary, the intention is to disclose and protect all
modifications, equivalents, and alternatives falling within the scope of the appended claims.
NOMENCLATURE
Certain terms are used throughout the following description and claims to refer to
particular system components. This document does not intend to distinguish between
components that differ in name but not function. The terms "including" and "comprising" are
used in an open-ended fashion, and thus should be interpreted to mean "including, but not
limited to...".
The term "couple" or "couples" is intended to mean either an indirect or direct
electrical, mechanical, or thermal connection. Thus, if a first device couples to a second
device, that connection may be through a direct connection, or through an indirect connection
via other devices and connections. Conversely, the term "connected" when unqualified
should be interpreted to mean a direct connection. For an electrical connection, this term
means that two elements are attached via an electrical path having essentially zero
impedance.
DETAILED DESCRIPTION
Disclosed herein are fluid analysis systems with one or more optical path components
formed or modified using atomic layer deposition (ALD). Such optical path components may
include, but are not limited to, an integrated computational element (ICE) (sometimes
referred to as a multivariate optical element or MOE), a light source, a bandpass filter, a fluid
sample interface, an input-side lens, an output-side lens, and a detector. As described herein,
ALD may be utilized to fabricate or modify certain optical path component parts or layers,
not necessarily entire components. Each layer formed using ALD may correspond to a planar
(flat) or non-planar (curved or sloped) layer of an ICE or other optical path components.
Use of ALD improves fabrication consistency and tolerances for optical path
components of a fluid analysis system compared to other fabrication options. Further, use of
ALD may affect optical path component design criteria such as the number of layers, layer
optical density, and layer thickness. Further, use of ALD may facilitate quality control
operations during manufacture of optical path components. Further, use of ALD-based
components enables improved fluid analysis system performance in harsh environments such
as encountered in oil exploration and extraction drilling. The improved performance in harsh
environments is due to the fabrication consistency and tolerances possible with ALD.
Further, design criteria for optical path components that are avoided for other deposition
techniques, such as reactive magnetron sputtering (RMS), are available with ALD. In some
embodiments, RMS may be employed to fabricate some component layers, while ALD is
employed to modify those layers and/or to fabricate other layers. The choice to employ RMS
or ALD may depend on design tolerances (e.g., ALD may be employed when design
tolerances are achievable using ALD, but not RMS). In an example fluid analysis application,
an ICE formed using ALD may provide a multivariate prediction of a chemical or physical
property of a substance. As disclosed herein, use of an ICE and/or other optical path
components formed using ALD in a fluid analysis system may improve the accuracy, type,
and/or range of predictions made by a fluid analysis system.
FIG. 1 shows an illustrative fluid analysis system 100. In fluid analysis system 100,
various optical path components are shown including an ICE 102, a sample interface 114, a
bandpass filter 106, an input-side lens 108, output-side lenses 110A and HOB, and detectors
112A and 112B. More specifically, ICE 102 is positioned between a light source 116 and
detectors 112A and 112B. Additional or fewer detectors may be used. Further, a fluid sample
104 is positioned between the light source 116 and ICE 102. The position of the fluid sample
104 may be set using fluid sample interface 114, which holds the fluid sample in its place.
Meanwhile, the input-side lens 108 and the output-side lenses 110A and 110B are configured
to focus the direction of light. Further, a bandpass filter (BPF) 106 may be employed on an
input-side of ICE 102 to filter certain wavelengths of light. Although Fig. 1 illustrates a
suitable arrangement for the optical path components of fluid analysis system 100, it should
be understood that other optical path component arrangements are possible. Further,
additional optical path components such as lenses and/or reflectors may be employed.
As disclosed herein, one or more of the optical path components of fluid analysis
system 100 may be fabricated or modified using ALD. For example, at least a portion of ICE
102 may be fabricated or modified using ALD. Further, at least some of light source 116,
BPF 106, lens 108, lenses 110A and HOB, detectors 112A and 112B, and/or sample interface
104 may be fabricated or modified using ALD.
In operation, the fluid analysis system 100 is able to correlate certain characteristics
of the fluid sample 104. The principles of operation of fluid analysis system 100 are
described, in part, in Myrick, Soyemi, Schiza, Parr, Haibach, Greer, Li and Priore,
"Application of multivariate optical computing to simple near-infrared point measurements,"
Proceedings of SPIE vol. 4574 (2002).
In operation, light from light source 116 passes through lens 108, which may be a
collimating lens. Light coming out of lens 108 has a specific wavelength component
distribution, represented by a spectrum. Bandpass filter 106 transmits light from a pre
selected portion of the wavelength component distribution. Light from bandpass filter 106 is
passed through sample 104, and then enters ICE 102. According to some embodiments,
sample 104 may include a liquid having a plurality of chemical components dissolved in a
solvent. For example, sample 104 may be a mixture of hydrocarbons including oil and natural
gas dissolved in water. Sample 104 may also include particulates forming a colloidal
suspension including fragments of solid materials of different sizes.
Sample 104 will generally interact with light that has passed bandpass filter 106 by
absorbing different wavelength components to a varying degree and letting other wavelength
components pass through. Thus, light output from sample 104 has a spectrum S( ) containing
information specific to the chemical components in sample 104. Spectrum S(X) may be
represented as a row vector having multiple numeric entries, Si. Each numeric entry Si is
proportional to the spectral density of light at a specific wavelength l. Thus, entries Si are all
greater than or equal to zero (0). Furthermore, the detailed profile of spectrum S(X) may
provide information regarding the concentration of each chemical component within the
plurality of chemicals in sample 140. Light from sample 104 is partially transmitted by ICE
102 to produce light measured by detector 112A after being focused by lens 110A. Another
portion of light is partially reflected from ICE 102 and is measured by detector 112B after
being focused by lens HOB. In some embodiments, ICE 102 may be an interference filter
with certain spectral characteristic that can be expressed as row vector L( ). Vector L( ) is an
array of numeric entries, Li, such that the spectra of transmitted light and reflected light is:
S (X) = S(X) - (1/2 + X) ) , (1.1)
SLR^) = S(X) (1/2 - L( )) , (1.2)
Note that the entries Li in vector L(X) may be less than zero, zero, or greater than zero.
Thus, while (l), SLT (l), and SLR ) are spectral densities, (X) is a spectral characteristic of
ICE 102. From Eqs. (1.1) and (1.2) it follows that:
SLT ) - SLR ) = 2-S^) - L^) , (2)
Vector L(X) may be a regression vector obtained from the solution to a linear
multivariate problem targeting a specific component having concentration k in sample 104. In
such case, it follows that:
= -å (S L (. ) - S LR ) ) + r , (3)
l
where b is a proportionality constant and g is a calibration offset. The values of b and g
depend on design parameters of fluid analysis system 100 and not on sample 104. Thus,
parameters b and g may be measured independently of the field application of fluid analysis
system 100. In at least some embodiments, ICE 102 is designed specifically to provide )
satisfying Eqs. (2) and (3), above. By measuring the difference spectra between transmitted
light and reflected light, the value of the concentration of the selected component in sample
104 may be obtained. Detectors 112A and 112B may be single area photo-detectors that
provide an integrated value of the spectral density. That is, if the signal from detectors 112A
and 112B is di and d 2 respectively, Eq. (3) may be readjusted for a new calibration factor b'
as:
= b · ( i - 2) + g , (4)
In some embodiments, fluid analysis systems such as system 100 may perform partial
spectrum measurements that are combined to obtain the desired measurement. In such case,
multiple ICEs may be used to test for a plurality of components in sample 104 that may be of
interest. Regardless of the number of ICEs in system 100, each ICE may include an
interference filter having a series of parallel layers 1 through K, each having a pre-selected
index of refraction and a thickness. The number K may be any integer greater than zero.
Thus, ICE 102 may have K layers, where at least one of the layers is fabricated or modified
using ALD.
FIG. 2 shows illustrative layers 206A-206K of an ALD-based ICE such as ICE 102.
At least one of the layers 206A-206K is fabricated or modified using ALD. Input medium
204 and output medium 208 are exterior layers on either side of ICE 102, and have respective
indices of refraction. In some embodiments, the indices of refraction for input layer 204 and
output layer 208 are equal to no. In alternative embodiments, the indices of refraction for
input layer 204 and output layer 208 may have different values. Meanwhile, layers 206A-
206K of ICE 102 may have respective indices of refraction and thicknesses.
FIG. 2 depicts incident light 201, reflected light 202, and transmitted light 203. As
shown, incident light 201 enters ICE 102 from input layer 204, and travels from left to right.
Reflected light 202 is reflected from the layers transitions of ICE 102, and travels from right
to left. Transmitted light 203 traverses the entire body of ICE 102, and travels from left to
right into output medium 208. For simplicity of illustration, ICE 102 is shown to have layers
206A-206K corresponding to materials selected for their indices of refraction among other
characteristics. In various embodiments, ICE 102 may include dozens of layers, hundreds of
layers, or thousands of layers.
At each layer transition of ICE 102, incident light travelling from left to right in FIG.
2 goes through a reflection/transmission process in accordance with the change in the index
of refraction. Thus, a portion of the incident light is reflected and a portion is transmitted.
The portion of reflected and transmitted light is governed by the principles of
reflection/refraction and interference. More specifically, the electric field of incident light at
a given layer transition may be denoted E+ (l), the electric field of reflected light at a given
layer transition may be denoted E (l), and the electric field of transmitted light at a given
layer transition may be denoted E+
(i+i)( ).
Reflection/refraction is governed by Fresnel laws, which for a given layer transition
determine a reflectivity coefficient Ri and transmission coefficient T as:
E ( ) =Ti (E )) , (5.1)
E ) =Ri E )) , (5.2)
Reflectivity coefficient Ri and transmission coefficient T are given by:
2n
, = (6.1)
n , + n ,
n -n.
R , = (6.2)
n , + n
A negative value in Eq. (6.2) means that the reflection causes a 180 degree phase
change in electric field. While more complex models can be adopted for light incident at an
angle to the surface, Eqs. (5.1) and (5.2) assume normal incidence. In some embodiments,
fluid analysis system 100 uses a version of Eqs. (6.1) and (6.2) including an angle of
incidence of approximately 45 degrees. Eqs. (6.1), (6.2) and their generalization for different
values of incidence may be found in J . D . Jackson, Classical Electrodynamics , John- Wiley &
Sons, Inc., Second Edition New York, 1975, Ch. 7 Sec. 3 pp. 269-282. In general, all
variables in Eqs. (5) and (6) may be complex numbers.
Note that a portion of reflected light at a given layer transition (i) travels to the left
towards the previous interface (i-l). At layer transition i-l, a subsequent reflection makes that
portion of reflected light travel back towards layer transition i . Thus, a portion of reflected
light makes a complete cycle through a given layer and is added as a portion of transmitted
light. This results in interference effects. More generally, transmitted radiation travelling
from left to right in FIG. 2 may include portions reflected a number of times, P, back and
forth between layer transitions of ICE 102. The number of reflections may vary. For example,
a value P=0 corresponds to light that has been transmitted through ICE 102 with no
reflections from left to right in FIG. 2. Thus, the transmitted light 203 will present
interference effects according to the different optical paths travelled for different values of P.
Likewise, reflected light 202 travelling from right to left in FIG. 2 may include
portions reflected a number of times, M, at any layer transition. Values of M may include any
positive integer. Reflected light 202 will present interference effects according to the
different optical paths travelled for different values of M.
Reflection and refraction are wavelength-dependent phenomena through refraction
indices corresponding to layer 206A-206K. Furthermore, the optical path for field component
E + (l) through a given layer, i, is (2 ¾l) · . Thus, the total optical paths for different values
of P depend on wavelength, index of refraction, and thickness, for each layer of ICE 102.
Likewise, the total optical paths for different values of M depend on wavelength, index of
refraction, and thickness, for each layer of ICE 102. Therefore, interference effects resulting
in transmitted light 202LT and reflected light 202LR are also wavelength dependent.
For the layer transitions of ICE 102, energy conservation needs to be satisfied for
each wavelength, l. Therefore, spectral density, SLT ) of transmitted light 202LT, and
spectral density SLR ) of reflected light 202LRsatisfy:
While a small portion of light may be absorbed by ICE 102 at certain wavelengths,
the absorption may be negligible. In some embodiments, fluid analysis system 100 operates
with ICE 102 adapted for reflection and transmission at approximately 45 degrees incidence
of the incoming light. Other embodiments of fluid analysis system 100 may operate with ICE
102 adapted for any other incidence angle, such as 0 degrees, as described by Eqs. (6.1) and
(6.2). Regardless of the angle of incidence for ICE 102 used in fluid analysis system 100, Eq.
(7) may still express conservation of energy in any such configuration. A model of the
spectral transmission and reflection characteristics of ICE 102 can be readily developed to
estimate performance based on the index of refraction and thickness, for all layers involved.
FIG. 3 shows target transmission spectrum 312 and intermediate model transmission
spectrum 312-M for an ALD-based ICE. Also shown in FIG. 3 are left wavelength cutoff
320-L (l , and right wavelength cutoff 320-R (l ) . Cutoffs 320-L and 320-R are
wavelength values that bound a wavelength range of interest for the application of fluid
analysis system 100 (cf. FIG. 1). In some embodiments, it may be desired that model
spectrum 312-M be approximately equal to target spectrum 312 for all wavelengths l
satisfying l L£ l < l R .
As shown in FIG. 3, model spectrum 312-M may be somewhat different from target
spectrum 312. For example, some wavelengths inside the range of interest for model
spectrum 312-M may be higher than for target spectrum 312, while other wavelengths inside
the range of interest for model spectrum 312-M may be lower than for target spectrum 312.
In such situations, an optimization algorithm may be employed to vary the parameters for the
index of refraction and thickness sets to find values rendering a model spectrum 312-M
closer to target spectrum 312. These sets define a parameter space having 2K dimensions.
In some embodiments, materials for layers 206A-206K enable the choice of 6
different indices of refraction and 1000 different thicknesses. This results in the 2K parameter
space having a volume of (6*1000) possible design configurations. Therefore, optimization
algorithms simplifying the optimization process may be used to scan this type of parameter
space to find an optimal configuration for ICE 102.
Examples of optimization algorithms that may be used are nonlinear optimization
algorithms, such as Levenberg-Marquardt algorithms. Some embodiments may use genetic
algorithms to scan the parameter space and identify configurations for ICE 102 that best
match target spectrum 312. Some embodiments may search a library of ICE designs to find a
design for ICE 102 that most closely matches target spectrum 312. Once the design for ICE
102 is found closely matching target 412, the parameters in the 2K space may be slightly
varied to find an even better model spectrum 412-M.
In some embodiments, the number of layers, K, may be included when evaluating an
optimal design for ICE 102. Thus, the dimension of the parameter space may be an
optimization variable according to some embodiments. Furthermore, some embodiments may
include constraints for variable K. For example, some applications of system 100 may benefit
from having less than a predetermined number of layers for ICE 102. In such embodiments,
the fewer the number of layers the better the predictability, precision, reliability and
longevity of ICE 102 and system 100. Meanwhile, other applications may benefit from
having more than a predetermined number of layers for ICE 102. Regardless of the number of
layers, use of ALD enables ICE design selections based on ALD tolerances as well as other
fabrication features mentioned previously.
The fluid analysis system 100, where ALD is used to fabricate or modify ICE 102,
BPF 106, lens 108, lens 110A, HOB, detectors 112A, 112B, and/or light source 116, may be
employed in a logging while drilling (LWD) environment or a wireline logging environment
to perform downhole fluid analysis operations. Fig. 4 shows an illustrative logging while
drilling (LWD) environment. A drilling platform 2 supports a derrick 4 having a traveling
block 6 for raising and lowering a drill string 8. A drill string kelly 10 supports the rest of the
drill string 8 as it is lowered through a rotary table 12. The rotary table 12 rotates the drill
string 8, thereby turning a drill bit 14. As bit 14 rotates, it creates a borehole 16 that passes
through various formations 18. A pump 20 circulates drilling fluid through a feed pipe 22 to
kelly 10, downhole through the interior of drill string 8, through orifices in drill bit 14, back
to the surface via the annulus 9 around drill string 8, and into a retention pit 24. The drilling
fluid transports cuttings from the borehole 16 into the pit 24 and aids in maintaining the
integrity of the borehole 16.
The drill bit 14 is just one piece of an open-hole LWD assembly that includes one or
more drill collars (thick-walled steel pipe) to provide weight and rigidity to aid the drilling
process. Some of these drill collars include built-in logging instruments to gather
measurements of various drilling parameters such as position, orientation, weight-on-bit,
borehole diameter, etc. As an example, a logging tool 26 (such as downhole fluid analysis
tool) may be integrated into the bottom-hole assembly near the bit 14. The drill string 8 may
also include multiple other sections 32 that are coupled together or to other sections of the
drill string 8 by adaptors 33. The logging tool 26 and/or one of sections 32 may include at
least one fluid analysis system 100 as described herein.
Measurements from the tool 26 and/or sections 32 can be stored in internal memory
and/or communicated to the surface. As an example, a telemetry sub 28 may be included in
the bottom-hole assembly to maintain a communications link with the surface. Mud pulse
telemetry is one common telemetry technique for transferring tool measurements to surface
receivers 30 and receiving commands from the surface, but other telemetry techniques can
also be used.
At various times during the drilling process, the drill string 8 may be removed from
the borehole 16 as shown in Fig. 5. Once the drill string has been removed, logging
operations can be conducted using a wireline logging tool 34, i.e., a sensing instrument sonde
suspended by a cable 42 having conductors for transporting power to the tool and telemetry
from the tool to the surface. It should be noted that various types of formation property
sensors can be included with the wireline logging tool 34. For example, without limitation,
the wireline logging tool 34 can include one or more sections 32 joined by adaptors 33. The
logging tool 34 and/or one or more sections 32 may include at least one fluid analysis system
100.
A logging facility 44 collects measurements from the logging tool 34, and includes
computing facilities 45 for managing logging operations and storing/processing the
measurements gathered by the logging tool 34. For the logging environments of Figs. 4 and
5, measured parameters can be recorded and displayed in the form of a log, i.e., a twodimensional
graph showing the measured parameter as a function of tool position or depth. In
addition to making parameter measurements as a function of depth, some logging tools also
provide parameter measurements as a function of rotational angle.
Fig. 6 shows an illustrative computer system 43 for managing logging operations. The
computer system 43 may correspond to the computing facilities 45 of logging facility 44 or a
remote computing system. The computer system 43 may include wired or wireless
communication interfaces for managing logging operations during a logging process. As
shown, the computer system 43 comprises user workstation 51, which includes a general
processing system 46. The general processing system 46 is preferably configured by
software, shown in Fig. 6 in the form of removable, non-transitory (i.e., non-volatile)
information storage media 52, to manage logging operations including fluid analysis
operations involving at least one fluid analysis system 100. The software may also be
downloadable software accessed through a network (e.g., via the Internet). As shown, general
processing system 46 may couple to a display device 48 and a user-input device 50 to enable
a human operator to interact with system software stored by computer-readable media 52.
The general processing system 46 may include surface processors and/or downhole
processors. The decision to perform different processing operations at the surface or
downhole may be based on preference or limitations with regard to the amount of downhole
processing available, the bandwidth and data rate for data transmissions between logging
tools and a surface computer, the complexity of data analysis to be performed, the durability
of downhole components, or other criteria. In some embodiments, software executing on the
user workstation 51 may present a logging management interface with fluid analysis options
to the user. Stated in another fashion, various logging management methods described herein
can be implemented in the form of software that can be communicated to a computer or
another processing system on an information storage medium such as an optical disk, a
magnetic disk, a flash memory, or other persistent storage device. Alternatively, such
software may be communicated to the computer or processing system via a network or other
information transport medium. The software may be provided in various forms, including
interpretable "source code" form and executable "compiled" form. The various operations
carried out by the software as described herein may be written as individual functional
modules (e.g., "objects", functions, or subroutines) within the source code.
FIG. 7 shows a flowchart illustrating an ICE fabrication method 500. As shown,
method 500 comprises selecting a lamp spectrum and bandpass filter at block 510. At block
520, a spectral characteristics vector is obtained. For example, the spectral characteristics
vector may be approximately equal to a regression vector solving a linear multivariate
problem. At block 530, a target spectrum is obtained. The target spectrum is obtained from
the lamp spectrum, the bandpass filter spectrum, and the spectral characteristics vector. At
block 540, ICE design layers are selected based on ALD tolerances. The layers selected may
be based on an optimization routine that varies the index of refraction, the thickness, and the
number of layers in a parameter space until an error between a model spectrum and a target
spectrum is less than a tolerance value. In some embodiments, the optimization routine may
be a nonlinear routine such as a Levenberg-Marquardt routine or generic algorithm. Use of
ALD to fabricate or modify ICE layers enables ICE design options to be selected that are
within ALD tolerance levels, but not reactive magnetic sputtering tolerance (RMS) levels. In
some embodiments, a combination of ALD and RMS may be employed (e.g., some layers are
fabricated using RMS while others are fabricated using ALD).
FIG. 8 shows a flowchart illustrating a fluid analysis system fabrication method 600.
In method 600, various optical path components of a fluid analysis system are formed using
ALD. At block 610, an ICE design having a plurality of optical layers is selected. At block
620, at least one of the plurality of optical layers is formed or modified using ALD. At block
630, at least part of a detector is formed or modified using ALD. At block 640, at least part of
a fluid sample interface is formed or modified using ALD. At block 650, at least part of a
bandpass filter is formed or modified using ALD. At block 660, at least part of a lens is
formed or modified used ALD. The various ALD-based components mentioned in method
600 may be arranged, for example, as described for system 100 of FIG. 1. At block 670, at
least part of a light source is formed or modified used ALD. The various ALD-based
components mentioned in method 600 may be arranged, for example, as described for system
100 of FIG. 1. Different fluid analysis systems may have fewer or additional ALD-based
components, and method 600 would vary accordingly. Further, different components of a
fluid analysis system may have layers formed using only ALD, only RMS, or both.
There are various known ALD techniques, which may be employed to form optical
path components of a fluid analysis system as in method 600. Generally, ALD is a film
growth technique that uses pairs of self limiting chemical reactions carried out in near
vacuum conditions. The surfaces of the substrates are covered in a monolayer with the first
reactant, the vacuum is used to purge the system and the second reactant is introduced into
the system. The second reactant contacts the substrate with the monolayer and reacts forming
a completed layer for an ICE or other optical path component. There are many commercial
pairs of reactants available. The cycle can be repeated until the desired layer thickness has
been achieved. For example, the layer control mechanism may count the number of reagent
additions. Reaction times are quick and growth rates as high as 100 angstroms in 40 minutes
are possible. ALD has been used to grow films, e.g., AI2O 3, with desirable optical properties
and with hardness properties suitable for extreme applications. For ICE fabrication, films of
alternating high and low optical refractive indices may be grown. High index materials such
as silicon and germanium, and low index materials such as S1O2 and MgC have been used to
grow ALD films.
With ALD, the quality assurance, quality control, and yield may be higher and more
easily controlled. As an example, the quality control for ALD may involve a straightforward
process of counting reactant additions, and then checking for performance. The monitoring of
the ALD process may be performed in real-time via with optical instruments to confirm
layering depth and other fabrication criteria. Further, ALD is a chemical reaction process that
results in a chemical bond to the base surface. Thus, the bond formed by ALD is stronger
(less delicate) than the bond formed by other deposition processes such as magnetron
sputtering or plasma coating processes.
As disclosed herein, ALD may be employed to fabricate more complex ICE designs
with thinner overall thickness (which results in faster fabrication times and better
performance than existing deposition techniques). Further, ALD may be used to fabricate
functionalized ICEs. For example, a terminating layer may be designed to have one or more
chemically reactive layers, bonded directed to the ICE. This would enable ICEs to be more
selective for an analyte or group of analytes than before. As another example, a terminating
layer may be designed to be a protective coating of different material than used to design the
spectral profile of the ICE. As another example, the surface can be patterned to enable use as
a size-exclusion layer in an environment where the medium is highly light scattering (e.g.,
reservoir fluids). Such patterning can be performed with strippable resist techniques. In a
well mixed environment, all surfaces may be coated and substrates may be bonded face to
face. Use of ALD also may enable performance or functionality improvements to other
optical path components of a fluid analysis system.
Besides ICE 102, other optical components of system 100 can be fabricated or
modified by ALD. For example, semiconductor detectors may be fabricated by ALD or
modified by ALD to include the ICE 102 directly on the surface. Further, semiconductor
detectors may be modified to include an anti-reflection or spectral bandpass layer structure.
As another example, lenses 110A and HOB can be modified to include an anti-reflection or
spectral bandpass layer structure.
FIG. 9 shows a flowchart of an illustrative fluid analysis method 700. As shown, the
method 700 includes emitting light (e.g., with light source 116) with a predetermined
spectrum at block 710. At block 720, the emitted light is directed through a fluid sample (e.g.,
fluid sample 104). At block 730, light that passed through the fluid sample is filtered using an
ALD-based ICE (e.g., ICE 102). As described herein, an ALD-based ICE includes a plurality
of optical layers, where at least one of the layers is formed or modified using ALD. The use
of ALD for one or more optical layers of an ICE can increase the accuracy, types, and/or
range of predictions made by a fluid analysis system At block 740, filtered light is detected
(e.g., by detectors 112A or 112B). At block 750, spectrum features of the detected filtered
light are correlated with a chemical or physical property of the fluid sample. The step of
block 750 may be performed, for example, by a processor coupled to detectors of a fluid
analysis system.
In some embodiments, the method 700 may include additional steps. For example, the
method 700 may also include, before and/or after the filtering step, directing light through at
least one optical path component formed or modified using ALD. Such optical path
components may include input-side lenses, output-side lenses, bandpass filters, sample
interfaces, light sources, or detectors as described herein.
Numerous variations and modifications will become apparent to those skilled in the
art once the above disclosure is fully appreciated. For example, though the methods disclosed
herein have been shown and described in a sequential fashion, at least some of the various
illustrated operations may occur concurrently or in a different sequence, with possible
repetition. It is intended that the following claims be interpreted to embrace all such
variations, equivalents, and modifications.
CLAIMS

WHAT IS CLAIMED IS:
1. A fluid analysis system, comprising:
a light source;
an integrated computation element (ICE); and
a detector that converts optical signals to electrical signals,
wherein the ICE comprises a plurality of optical layers, and wherein at least one of
the plurality of optical layers is formed using atomic layer deposition (ALD) to enable
prediction of a chemical or physical property of a substance.
2. The fluid analysis system of claim 1, wherein the ICE comprises a plurality of different
types of optical layers based on ALD, and wherein the plurality of different types of optical
layers have different indices of refraction.
3. The fluid analysis system of claim 1, wherein the ICE comprises at least one optical layer
formed using reactive magnetic sputtering (RMS).
4. The fluid analysis system of claims 1, wherein the ICE comprises at least one non-planar
optical layer formed or modified using ALD.
5. The fluid analysis system according to any of claims 1, further comprising a fluid sample
interface, wherein the fluid sample interface comprises at least one layer formed or modified
using ALD.
6. The fluid analysis system of claim 5, wherein the fluid sample interface comprises a
diamond layer formed using ALD.
7. The fluid analysis system according to any one of claims 1to 6, wherein the detector or the
light source comprises at least one layer formed or modified using ALD.
8. The fluid analysis system according to any one of claims 1 to 6, further comprising a
bandpass filter element, wherein the bandpass filter element comprises at least one layer
formed or modified using ALD.
9. The fluid analysis system according to any one of claims 1 to 6, further comprising an
input-side lens with respect to the ICE, wherein the input-side lens comprises at least one
layer formed or modified using ALD.
10. The fluid analysis system according to any one of claims 1 to 6, further comprising an
output-side lens with respect to the ICE, wherein the output-side lens comprises at least one
layer formed or modified using ALD.
11. A method for fabricating a fluid analysis system, comprising:
selecting an integrated computation element (ICE) design having a plurality of optical
layers; and
forming at least one of the plurality of optical layers of the ICE using atomic layer
deposition (ALD) to enable prediction of a chemical or physical property of a substance.
12. The method of claim 11, further comprising forming or modifying at least part of a light
source or detector using ALD.
13. The method of claim 11, further comprising forming or modifying at least part of a fluid
sample interface using ALD and arranging the fluid sample interface at an input-side of the
ICE.
14. The method of claim 11, further comprising forming or modifying at least part of a
bandpass filter element using ALD and arranging the bandpass filter element at an input-side
of the ICE.
15. The method according to any of claims 11-14, further comprising forming or modifying
at least part of a lens using ALD and arranging the lens at an input-side or output-side of the
ICE.
16. The method according to any of claims 11-14, further comprising forming or modifying
at least one non-planar optical layer of the ICE using ALD.
17. The method according to any of claims 11-14, further comprising forming a plurality of
different types of optical layers of the ICE using ALD.
18. A logging string, comprising:
a logging tool section; and
a fluid analysis tool associated with the logging tool section, wherein the fluid
analysis tool comprises an integrated computation element (ICE) with at least one optical
layer formed using atomic layer deposition (ALD) to enable prediction of a chemical or
physical property of a substance.
19. The logging string of claim 18, wherein the fluid analysis unit comprises at least one of a
detector a bandpass filter formed or modified using ALD.
20. A method for fluid analysis, comprising:
directing light having a predetermined spectrum through a fluid sample;
filtering light output from the fluid sample though a plurality of optical layers,
wherein at least one of the plurality of optical layers is formed using atomic layer deposition
(ALD) to filter the light in dependence on a chemical or physical property in the fluid
sample;
detecting filtered light output from the plurality of optical layers; and
correlating spectrum features of the filtered light to said chemical or physical property
of the fluid sample.
21. The method of claim 20, further comprising, before said filtering, directing light through
at least one optical path component formed or modified using ALD.
22. The method of claim 20, further comprising, after said filtering and before said detecting,
directing light through at least one optical path component formed or modified using ALD.