U.S. patent application number 11/079921 was filed with the patent office on 2006-09-14 for detecting gas in fluids.
Invention is credited to John Wesley DeBliek, Scott Edwin Gunn.
Application Number | 20060202122 11/079921 |
Document ID | / |
Family ID | 35355617 |
Filed Date | 2006-09-14 |
United States Patent
Application |
20060202122 |
Kind Code |
A1 |
Gunn; Scott Edwin ; et
al. |
September 14, 2006 |
Detecting gas in fluids
Abstract
A method for detecting gas in a fluid, the system including
flowing fluid bearing gas through a gas trap apparatus, flowing gas
trapped by the gas trap apparatus to and through an infra-red gas
detection system for detecting the gas, the infrared gas detection
system having apparatus for isolating absorption spectra of the
gas, producing with the infra-red gas detection system analog
signals indicative of levels of the gas, transmitting the analog
signals to a first processor for converting the analog signals to
digital signals, transmitting the digital signals from the first
processor to a second processor, producing with the second
processor digital signals indicative of the level of the gas.
Inventors: |
Gunn; Scott Edwin; (Calgary,
CA) ; DeBliek; John Wesley; (Calgary, CA) |
Correspondence
Address: |
Guy McClung
PMB 347
16690 Champion Forest Drive
Spring
TX
77379-7023
US
|
Family ID: |
35355617 |
Appl. No.: |
11/079921 |
Filed: |
March 14, 2005 |
Current U.S.
Class: |
250/339.13 |
Current CPC
Class: |
E21B 21/01 20130101;
G01N 21/3504 20130101 |
Class at
Publication: |
250/339.13 |
International
Class: |
G01J 5/02 20060101
G01J005/02 |
Claims
1. A method for detecting gas in a fluid, the method comprising
flowing fluid bearing gas through a gas trap apparatus, flowing gas
trapped by the gas trap apparatus to and through an infra-red gas
detection system for detecting the gas, the infrared gas detection
system having a first processor and apparatus for isolating
absorption spectra of the gas, producing with the infra-red gas
detection system analog signals indicative of levels of the gas,
converting the analog signals to digital signals with the first
processor, transmitting the digital signals from the first
processor to a second processor, and producing with the second
processor digital signals indicative of the level of gas.
2. The method of claim 1 wherein the fluid is drilling fluid and
the gas is hydrocarbon gas from a wellbore.
3. The method of claim 1 wherein the analog signals are transmitted
wirelessly.
4. The method of claim 1 further comprising producing with the
second processor a visual display of a level of the gas.
5. The method of claim 1 wherein the production of the analog
signals and the production of the digital signals is done in real
time.
6. The method of claim 1 wherein the first processor includes an
interface board for receiving the analog signals, for converting
the analog signals to the digital signals, and for then
transmitting the digital signals to the second processor, the
second processor including a host computer for receiving the
digital signals and for processing the digital signals to produce
an indication of level of the gas, the method further comprising
the interface board receiving the analog signals and converting the
analog signals to the digital signals, the interface board
transmitting the digital signals to the host computer, and
producing with the host computer an indication of the level of the
gas.
7. The method of claim 6 wherein the host computer produces an
indication of a level of total gas in the fluid.
8. The method of claim 6 wherein the interface board has a
programmable medium programmed to calibrate the infra-red gas
detection system and the method further comprising calibrating the
infra-red gas detection system with the interface board.
9. The method of claim 6 wherein the host computer provides a user
interface for conducting the method.
10. The method of claim 6 further comprising conditioning the
analog signals with the interface board to reduce noise in said
signals.
11. The method of claim 1 wherein the infra-red gas detection
system has gas sensor apparatus and there is no physical reaction
between the gas and the gas sensor apparatus.
12. The method of claim 6 further comprising controlling
temperature of the infra-red gas detection system.
13. The method of claim 12 wherein the infra-red gas detection
system includes the first processor and the infra-red gas detection
system is in an enclosure and heater apparatus and cooling
apparatus are connected to the enclosure for controlling
temperature therein.
14. The method of claim 1 wherein the infra-red gas detection
system is portable.
15. The method of claim 1 wherein the gas is hydrocarbon gas.
16. The method of claim 15 wherein the hydrocarbon gas is methane
and propane.
17. The method of claim 1 wherein the hydrocarbon gas is
methane.
18. The method of claim 1 wherein the hydrocarbon gas is
propane.
19. The method of claim 1 wherein the infra-red gas detection
system includes a gas detector with a detection channel and a
reference channel, the method further comprising detecting with the
detection channel infra-red radiation absorbed by the gas, and
compensating with the reference channel for variations in the
gas.
20. The method of claim 1 further comprising filtering moisture
from the gas prior to flowing the gas to the infra-red gas
detection system to inhibit or prevent the generation of false
readings due to moisture.
21. The method of claim 6 wherein the infra-red gas detection
system includes an infra-red lamp, an infra-red lamp drive, and a
gas sensor and the interface board provides an interface between
the infra-red lamp drive and the gas sensor.
22. A method for detecting gas in drilling fluid, the method
comprising flowing drilling fluid bearing hydrocarbon gas from a
wellbore through a gas trap apparatus, flowing gas trapped by the
gas trap apparatus to and through an infra-red gas detection system
for detecting the hydrocarbon gas, the infrared gas detection
system having narrow band infrared filter apparatus for isolating
absorption spectra of the hydrocarbon gas, producing with the
infra-red gas detection system analog signals indicative of levels
of the hydrocarbon gas, transmitting the analog signals to a first
processor for converting the analog signals to digital signals,
transmitting the digital signals from the first processor to a
second processor, producing with the second processor digital
signals indicative of the level of hydrocarbon gas, the first
processor including an interface board for receiving the analog
signals, for converting the analog signals to the digital signals,
and for then transmitting the digital signals to the second
processor, the second processor including a host computer for
receiving the digital signals and for processing the digital
signals to produce an indication of level of the gas, the method
further comprising the interface board receiving the analog signals
and converting the analog signals to the digital signals, the
interface board transmitting the digital signals to the host
computer, producing with the host computer an indication of the
level of the gas, wherein the infra-red gas detection system has
gas sensor apparatus and there is no physical reaction between the
gas and the gas sensor apparatus, controlling temperature of the
infra-red gas detection system, wherein the infra-red gas detection
system includes the first processor and the infra-red gas detection
system is in an enclosure and heater apparatus and cooling
apparatus are connected to the enclosure for controlling
temperature therein.
23. A system for detecting gas in a fluid, the system comprising an
enclosure, an infra-red gas sensor apparatus within the enclosure,
an interface board apparatus within the enclosure and in
communication with the infra-red gas sensor apparatus, analog
signal apparatus in the infra-red gas sensor apparatus for
producing analog signals indicative of a level of gas in a fluid,
conversion apparatus on the interface board apparatus for
converting the analog signals to digital signals, and transmission
apparatus on the interface board apparatus for transmitting the
digital signals to a host system.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field Of The Invention
[0002] The present invention is directed to detecting gas in
fluids, e.g. drilling fluid that has been circulated through a
wellbore and, in one particular aspect, to systems and methods for
detecting individual hydrocarbons, e.g., but not limited to,
methane and propane, with infrared sensing apparatus.
[0003] 2. Description of Related Art
[0004] The prior art discloses a wide variety of systems and
methods for detecting gas in drilling fluid or "mud" that is
circulated down a drillstring, through a bit, and then back out of
a wellbore during drilling. During a drilling operation, the mud is
continuously pumped down through the drill string and into the
region around the drill bit and then back up a borehole annulus to
the surface. Often the mud is made up of clays, chemical additives
and an oil or water base and performs several important functions.
The mud cools and lubricates the drill bit, carries drill cuttings
back up out of the well, and serves to maintain a hydrostatic
pressure which prevents pressurized fluids in the earth formation
from blowing out through the drilled well.
[0005] Various measurements may be taken while drilling a well both
of the drilling mud entering the drill string and returning to the
surface and of other parameters as determined by tools at or near
the drill bit. The measurements at or near the drill bit are
typically called measurements while drilling ("MWD") and provide a
log of the drilling operations from which one may attempt to
analyze the earth formations which the drill bit is penetrating.
These logs are important as they enable the drilling operator to
ascertain the presence of oil or gas in the formation being
drilled. Mud logging measurements, including temperature,
electrical conductivity, pH, sulfide ion content and
oxidation-reduction potential of the drilling mud returning from
the well may also be made. In addition, measurements may be made on
the returning mud to ascertain total hydrocarbon content and to
ascertain the presence of certain specific gases such as carbon
dioxide and hydrogen sulfide in the mud. The gas content of the mud
may serve as an indicator of the pore pressure of the drilled
section, and if properly determined can be used to identify "oil
shows" and "pay zones". The gas content of the mud is proportional
to the pore pressure of the section being drilled, and if properly
determined can be used to identify producible zones.
[0006] Several prior art systems and techniques have been used to
detect and analyze gas in drilling mud. Gas is typically extracted
from the mud by mechanical agitation in a gas trap which is located
in a possum belly tank (also called "header tank") or in a box of a
shale shaker. The extracted gas is analyzed for hydrocarbons and/or
"total gas"; e.g. by one or more of several different detectors
such as a catalytic combustion detector (CCD) apparatus, thermal
conductivity detectors (TCD), and flame ionization detectors (FID).
Separation and quantification of the different light hydrocarbon
(e.g. methane through pentanes) gases are then typically carried
out via gas chromatography techniques with similar or different
detectors. In certain prior art systems, chromatography techniques
require several minutes for analysis and the gas content of the mud
is determined for batch samples taken at discrete intervals of
several minutes apart.
[0007] U.S. Pat. No. 4,635,735 discloses that spectrographic
analysis of separated gases permits a continuous analysis of the
gas content of the mud. In U.S. Pat. No. 4,635,735, at least a
portion of the drilling mud returning from the well is subjected to
gas separation in a mud/gas separator. The separated gas is then
subjected to analysis in a gas spectral analyzer apparatus
(spectrophotometers) to produce a gaseous component concentration
signal whose value at any instant represents the concentration at
that instant of the given gaseous component in the separated gas.
By also monitoring the low rate of the returning mud through the
separation device, and the flow rate of the separated gas, a
continuous determination is made of the concentration of the given
gaseous components in the drilling mud. The drilling mud is passed
through an agitating type mud/gas separation device while a carrier
gas is simultaneously flowed through the mud/gas separation device.
The carrier gas is thoroughly mixed in the mud/gas separation
device. The resulting mixture of carrier gas and mud gas is
separated from the mud in the separation device and is subjected to
analysis in a gas analyzer to produce a component gas signal whose
value corresponds to the concentration of the component in the gas
mixture. By measuring the carrier gas volume flowing into the
mud/gas separation device, the flow rate of the mud into the
separation device, and the component gas signal, a continuous
concentration signal representing the concentration of the
component gas in the drilling mud may be obtained.
[0008] U.S. Pat. No. 4,887,464 discloses a system which samples
substantially all of the volatile constituents evolving from a well
and captures substantially all of the gases evolving from a well by
suction and extraction techniques. This system analyzes and
provides quantitative determinations of at least the various
hydrocarbon gases evolving from a well. The system has apparatus
for capturing liberated gases in a bell nipple and return line,
extraction means for extracting gases entrained and dissolved in
drilling mud, and means for analyzing and quantifying the captured
and extracted gases.
[0009] In certain prior art systems a gas trap is used which is a
metal box immersed in a shale-shaker ditch. Ports in the lower part
of the trap allow mud to enter and leave the trap. An agitator
motor provides pumping and degassing of mud passing through the
trap. In certain prior art systems, the extraction of gas samples
from the mud includes bubbling an extractant gas directly through
the mud slurry, then separating the gas from the slurry and
cleaning the gas for inputting to analytical instruments used for
hydrocarbon detection, identification, and quantitative
determination. In one prior art system (see U.S. Pat. No.
5,469,917) a supported capillary-membrane sampling device is used
which has a grooved support member having a tubular membrane,
capillary column, or the like supported within the groove of the
support member. This apparatus is used for analytical and/or
fluid-separation purposes and allows the elimination of the sample
extraction--cleanup train. One particular prior art method includes
providing a device with a support member, a capillary membrane
permeable to hydrocarbons, and flights on the surface of the
support member within which the capillary member is supported;
disposing the device in a stream returning mud from a drill hole to
the surface of an oil well; passing a stream of inert gas through
the capillary membrane, thereby entraining hydrocarbon vapors in
the gas stream; and inputting the gas stream containing the
entrained hydrocarbon vapors to an analytical instrument capable of
identifying and quantitatively determining the concentration of the
hydrocarbons.
[0010] In several prior art systems liberated gas is directed past
a gas sensor, e.g. a gas chromatography sensor, which produces a
record of the constituents of the gas. In other prior art systems
producing a continuous gas trace, a catalytic, rare earth or a hot
wire gas sensor is used. The sensor detects the presence of
combustible gases. These devices are also called explosimeters and
indicate the relative fraction of volatile hydrocarbons in a gas
stream. Often these apparatuses are used to determine if a gas
mixture may be explosive. In a typical gas sensor using a rare
earth (hot-wire) sensor, an electrical current is passed though the
sensor. The sensor heats up and dissipates energy dependent upon
its ability to exchange energy with the surrounding environment. In
these applications it is the gas flow and gas composition which
affect the heat dissipation. Heat or power dissipation results in a
change in the resistance of the sensor. The sensor is either epoxy
coated for limiting the sensor from thermal effects and for
excluding chemical interaction with the sensor's rare-earth
portion, or the sensor is stripped of its epoxy coating (see U.S.
Pat. No. 6,276,190). Stripped of their coatings, individual sensors
have individual responses. Certain sensors which respond
differently and predictably to known ranges of hydrocarbons can be
used for analyses of the relative concentrations within gases.
[0011] In one prior art system of U.S. Pat. No. 6,276,190, two rare
earth sensors are provided. Each sensor is sensitive to different
ranges of hydrocarbons in sampled gases. Changes in relative
concentration of the selected hydrocarbon in the sampled gas result
in a change in the output of the corresponding sensor. Thus, where
the sampled gas is a mixture of light and heavy hydrocarbon gases,
the two sensors generally respond differently as the relative
concentrations in the mixture change. The different response can be
accentuated by obtaining the difference of the two signals. So, as
drilling progresses through subterranean zones having different
qualities of gases, the gas sensors provide distinctive outputs
dependent upon whether they detect light or heavy hydrocarbons.
Different gas qualities are distinguishable using such a
system.
[0012] In several prior art systems, the total gas from a mud pit
is analyzed by a separate instrument, a total gas analyzer, to
determine the total amount of gases produced. Also the amount of
each individual gas is determined by a second instrument, a
chromatograph. The quantity of methane, ethane, propane, isabutane,
butane and pentane are each measured by the chromatograph as to the
amount each is present. In certain prior art systems the two
instruments are combined into one small unit. With a single unit
the total gas produced and the amount of each gas is determined.
The only lines to the gas analyzer are a single gas line from the
mud pit and a single electric power line. The results of analysis
are automatically continually available. The results may be
recorded every 5 minutes. In one particular prior art method (U.S.
Pat. No. 6,374,668) using such a system for analyzing methane
series of gas produced from a drilling rig, the method includes: a)
pumping a small gas specimen from a mud pit, b) flowing the small
gas specimen to a sample valve, c) splitting the flow in the sample
valve into a TGA (total gas analyzer) stream and a CG
(chromatograph) stream, d) creating a closed time period and normal
time period with the normal time period much longer than the closed
time period, e) continually flowing, during normal time period and
closed time period, the TGA stream to a total gas analyzer, and f)
intermittently flowing the CG stream during the closed time period
to a chromatograph.
[0013] Prior art catalytic and thermo conductive (TCD) sensor
technology has been widely used in detecting gas while drilling.
These sensors can have several disadvantages. The most inherent
disadvantage is that the physical sensor itself reacts with the
gas/air mixture flowing by it. This allows several problems to
occur. The reaction of the sensor to gas can deteriorate the sensor
over time and eventually the sensor's sensitivity and repeatability
cannot be duplicated. Consistency can be lost on long wells or when
units are in the field for long periods of time. Moisture in the
gas/air sample can corrode or react with the physical sensor
reducing the sensors sensitivity and lifespan. Several diesel-based
and polymer-type mud systems used on drilling rigs will release
small particles into the gas/air sample. These particles will react
with the compound forming the physical sensor and corrode it or
give a false output signal not representing hydrocarbon shows. The
mud system particle can have a negative affect on the sensor giving
a negative gas value output, this can overshadow the gas being
liberated from the well. H.sub.2S, N.sub.2 and CO.sub.2 can cause
sensors to react giving false gas indications, going negative and
poisoning the sensor until sensitivity is lost. Any coatings
applied on top of the physical surface of the sensor can reduce the
sensor's sensitivity. Many prior art sensors which are
sensitive-specific to methane (C.sub.1) alone do not work as a
total gas detector. Some of these sensors never show any indication
when zones rich in heavy hydrocarbons are drilled.
[0014] There is a need, recognized by the present inventors, for
efficient and effective gas detector systems and methods for using
them which provide consistency, repeatability, sensitivity, and
have a long lifespan.
[0015] There is a need, recognized by the present inventors, for
such systems and methods in which there is no physical reaction
with the gas being detected or with the fluid bearing the gas.
[0016] There is a need, recognized by the present inventors, for
such a gas detector which is hydrocarbon-specific and which can
detect light hydrocarbons and/or heavier hydrocarbons.
SUMMARY OF THE PRESENT INVENTION
[0017] The present invention, in at least certain embodiments,
discloses a gas detection system which includes infra-red gas
detector apparatus that is specific to hydrocarbon components
through which a sample gas flows, a computer system for receiving
data from the infra-red gas detector apparatus and for processing
such data, a display (e.g. screen and/or strip chart) to display
results (in one aspect, in real time) and, optionally, connections
and interfaces for providing test results at sites remote from the
test site. In certain aspects, the present invention discloses a
method for detecting gas in a fluid, the method including flowing
fluid bearing gas through a gas trap apparatus; flowing gas trapped
by the gas trap apparatus to and through an infra-red gas detection
system for detecting the gas, the infrared gas detection system
having a first processor and apparatus for isolating absorption
spectra of the gas; producing with the infra-red gas detection
system analog signals indicative of levels of the gas; converting
the analog signals to digital signals with the first processor;
transmitting the digital signals from the first processor to a
second processor; and producing with the second processor digital
signals indicative of the level of gas. In certain aspects, the
present invention discloses a system for detecting gas in a fluid,
the system including an enclosure; an infra-red gas sensor
apparatus within the enclosure; an interface board apparatus within
the enclosure and in communication with the infra-red gas sensor
apparatus; analog signal apparatus in the infra-red gas sensor
apparatus for producing analog signals indicative of a level of gas
in a fluid; conversion apparatus on the interface board apparatus
for converting the analog signals to digital signals; and
transmission apparatus on the interface board apparatus for
transmitting the digital signals to a host system.
[0018] In one particular aspect, a gas detection system according
to the present invention has a methane sensor and a propane sensor,
each of which is connected to a corresponding gas chamber interface
board (GCIB). The GCIB's provide an interface between the sensors
and a drive for an infra-red lamp (one lamp in each sensor); and
each GCIB performs amplification and signal conditioning on the
sensor output signals and does an analog-to-digital (A/D)
conversion of data from the sensors. By doing this on the GCIB's,
susceptibility to noise is reduced. The sensors are calibrated on
the basis of the digitized signals (digitized signals produced by
the GCIB's), thus the calibration can be handled completely in
software.
[0019] A WSGD main board contains a primary processor for the
system which handles communications and control within the system.
The main board reads the digitized data from the GCIB's via a
serial interface. In certain aspects, the main board communicates
with a host computer (e.g. a desk top or a laptop, on site or
remote), in one aspect via a wireless modem. The host computer
provides the user interface to the system and performs and displays
the calibration of the sensor data and generates results for gas
content, e:g. but not limited to, methane and propane content.
[0020] Systems according to the present invention can measure
levels of hydrocarbons (e.g. methane, ethane, propane, butane, and
iso-butane). In one aspect, the sensors are calibrated for 0 to
100% volume of gas in air of methane and propane, however both
sensors are sensitive at some level to other hydrocarbons. The
sensors in such an embodiment do not completely isolate methane and
propane from other hydrocarbons, but rather, the methane sensor
provides a stronger response to methane and ethane (see, e.g. curve
C1+C2, FIG. 6) and the propane sensor provides a stronger response
to propane, butane, and iso-butane (see, e.g. curve C3+C4+C5, FIG.
6). Systems according to the present invention can be portable with
an easily emplaceable lightweight-polyurethane-encased gas trap, in
one aspect with a gas dryer; a component-specific infra-red gas
detector system, a laptop computer, and a wireless modem. In one
particular aspect, using a wireless modem or similar device, a
wireless portable gas monitor is provided.
[0021] In one particular aspect, an infra-red gas detector system
used with systems according to the present invention has a light
source and a dual channel infrared detector with a narrow band
infrared filter on each channel. In one aspect, the filters are on
a sapphire substrate, and an overall quartz window covers the
sensor to protect the filter surfaces and provide additional
thermal isolation for the sensor. One channel of the detector is
used to detect the infrared absorbed by the target gas; the other
channel is used as a reference channel to provide compensation of
the sensor for temperature and luminance variations. There is never
any physical reaction with the gas/air mixture and thus sensor
consistency and repeatability does not deteriorate. In certain
aspects, routine calibrations of such system can be good for over 6
months. The sensor is sealed in a capsule and quartz window and
contaminants in gases have little effect on its sensitivity and
repeatability. High levels of humidity can generate false readings
on a sensor, so it is preferable, in certain aspects, to filter out
moisture from the input gas stream. The sensors use
frequency-specific molecular absorption to indicate hydrocarbons.
Particles of mud systems do not react with the sensors and the
sensors use filters on the lenses so only the specific frequency
for hydrocarbons gases are detected by the sensor. H.sub.2S,
N.sub.2 and CO.sub.2 are at different frequencies and are not
detected. The sensors, in certain embodiments, indicate methane and
propane in their pure form, but can also indicate gases of
multi-component composition. In certain aspects, the methane sensor
is calibrated for 0 to 100% volume ethane, or the propane sensor is
calibrated specifically for 0 to 100% volume butane, isobutane, or
pentane. This does not change the response of the sensors to other
gases. This gives a geologist a full evaluation of each
hydrocarbon-bearing zone and can indicate secondary zones that were
not previously considered.
[0022] What follows are some of, but not all, the objects of this
invention. In addition to the specific objects stated below for at
least certain preferred embodiments of the invention, other objects
and purposes will be readily apparent to one of skill in this art
who has the benefit of this invention's teachings and disclosures.
It is, therefore, an object of at least certain preferred
embodiments of the present invention to provide new, unique,
useful, and nonobvious systems and methods of their use--all of
which are not anticipated by, rendered obvious by, suggested by, or
even implied by any of the prior art, either alone or in any
possible legal combination.
[0023] Certain embodiments of this invention are not limited to any
particular individual feature disclosed here, but include
combinations of them distinguished from the prior art in their
structures and functions. Additional aspects of the invention
described below and which may be included in the subject matter of
the claims to this invention. Those skilled in the art who have the
benefit of this invention, its teachings, and suggestions will
appreciate that the conceptions of this disclosure may be used as a
creative basis for designing other structures, methods and systems
for carrying out and practicing the present invention. The claims
of this invention are to be read to include any legally equivalent
devices or methods.
[0024] The present invention recognizes and addresses the
previously-mentioned problems and long-felt needs and provides a
solution to those problems and a satisfactory meeting of those
needs. To one skilled in this art who has the benefits of this
invention's realizations, teachings, disclosures, and suggestions,
other purposes and advantages will be appreciated from the
following description of preferred embodiments, given for the
purpose of disclosure, when taken in conjunction with the
accompanying drawings. The detail in these descriptions is not
intended to thwart this patent's object to claim this invention no
matter how others may later disguise it by variations in form or
additions of further improvements.
[0025] The Abstract that is part hereof is to enable the United
States Patent and Trademark Office and the public generally, and
scientists, engineers, researchers, and practitioners in the art
who are not familiar with patent terms or legal terms of
phraseology to determine quickly from a cursory inspection or
review the nature and general area of the disclosure of this
invention. The Abstract is neither intended to define the
invention, which is done by the claims, nor is it intended to be
limited of the scope of the invention in any way.
DESCRIPTION OF THE DRAWINGS
[0026] A more particular description of embodiments of the
invention briefly summarized above may be had by references to the
embodiments that are shown in the drawings which form a part of
this specification. These drawings illustrate certain embodiments
and are not to be used to improperly limit the scope of the
invention that may have other equally effective or legally
equivalent embodiments.
[0027] FIG. 1 is a schematic view of a system according to the
present invention.
[0028] FIG. 2 is a schematic view of a prior art infra-red sensor
system.
[0029] FIG. 3 is a schematic view of a system according to the
present invention.
[0030] FIGS. 4A and 4B are schematic views of parts of a system
according to the present invention.
[0031] FIG. 5 is a schematic of a system according to the present
invention.
[0032] FIG. 6 shows a typical display of results using a system
according to the present invention with, inter alia, specific
curves for methane and propane and a calculated total hydrocarbon
curve.
DESCRIPTION OF EMBODIMENTS PREFERRED AT THE TIME OF FILING FOR THIS
PATENT
[0033] As shown in FIG. 1 a gas detector 50 according to the
present invention receives gas samples in a polyflow line 37 from a
gas trap 12. A drilling rig 11 drills a well 13 into a formation
25. A mud pump 33 pumps mud M in a line 36 into the well 13 down a
drillstring 22, to and through a bit apparatus 23, and then up in
an annulus 26 to an exit line 27 which feeds into the gas trap 12.
The mud M exits the gas trap 12 and flows into a mud tank 17 from
which the mud pump 33 pumps the mud in a line 35 back to the line
36. A transmitter or modem 15 (e.g. wireless or hardwired)
transmits signals from the gas detector 50 to apparatus or systems
such as a computer, computer system, network, or a data acquisition
system or apparatus.
[0034] FIG. 2 shows a typical prior art infra-red sensor system in
which infra-red light from an infra-red source passes through
material to be analyzed in a chamber C, then through a narrow band
filter, to an infra-red detector. The material flows into the
chamber C through a "Sample In" port and out through a "Sample Out"
port.
[0035] FIG. 3 shows a wireless portable system 70 according to the
present invention useful as one embodiment of the system 50, FIG.
1, which has a gas trap system 71, a gas dryer 71a, a wireless
portable gas monitor system 72, a laptop computer 73 (to serve as a
host with host software), and a wireless radio modem 74.
[0036] FIGS. 4A and 4B show schematically one arrangement for
components of a system 80 (like the systems 50 and 70) according to
the present invention. The gas detector system 80 has two GCIB's 81
(Gas Chamber Interface Boards). The system 80 has two gas detectors
82 (e.g. two commercially available detectors) paired with the
GCIB's 81 with sensors to provide gas data, e.g., in one aspect,
methane and propane level data. In one aspect, the detectors 82
provide analog data which, in one aspect, is an alternating
sinusoidal waveform whose amplitude is reduced by the infrared
absorption in the band of interest. A main board 83 receives
digitized data from the GCIB's 81 and, via a wireless modem 84 (or
land line) communicates with a host 85 (e.g. a computer system).
With host application software 86, the host 85 provides a graphic
presentation of gas levels, e.g. methane and propane levels. The
detectors 82 are each connected to a GCIB 81 which provides an
interface for each detector 82 and a drive for the lamp (infra-red
source, e.g. like the infra-red source, FIG. 2) in each detector
82. The GCIB's 81 perform amplification and signal conditioning on
the sensor output signals (analog signals indicative of gas level)
which, following digitization and calibration indicate actual gas
levels (as a % by volume of gas in air) before doing an A/D
conversion on board (or off board). In one aspect, by doing the AID
conversions on the GCIB's, system susceptibility to noise is
reduced. Optionally, analog conditioning is done. In one aspect,
the analog conditioning performed takes the alternating waveform
from the sensor and rectifies and filters it to give a DC voltage
output that can be digitized. The waveform is also inverted before
digitization so that the signal will actually increase as the gas
concentration increases. The calibration of the sensor is performed
on the digitized signals, so calibration can be handled completely
in software in the host computer (e.g. a laptop).
[0037] Each GCIB 81 has a small microprocessor that controls the
A/D conversion on its board and also handles a serial interface to
the main board 83. The main board 83 has a primary microprocessor
89 which requests sensor and temperature data from the GCIB's,
handles temperature control of the system, does some digital
processing, (e.g. exponential averaging) on the sensor data,
handles timing and control of the system, and provides a serial
interface to the wireless modem 84, through which the host
application software 86 can remotely issue commands and receive
sensor data from the system. The main board 83 also has
non-volatile memory 83a to store the calibration data for the
system.
[0038] To read sensor data from the GCIB's 81 the main board 83
sends a command to put the GCIB's 81 into a gas sample mode. When
the GCIB's 81 receive this command, they do an A/D conversion, e.g.
they do 4096 A/D conversions of the sensor signals over a 1.2
second period (five lamp drive pulse periods), and average these to
produce an output value for each sensor channel. The main board 83
reads these values after the 1.2 second period. The main board 83
then issues a command to put the GCIB's into a temperature sample
mode, and reads the temperature data for each detector 82. The
temperature data is not averaged on the GCIB, although analog
filtering (to remove higher frequency noise from the signal in
order to improve the signal-to-ratio) is performed prior to the A/D
conversion. In one aspect, the main board 83 reads the data from
both detectors 82 every two seconds. Some additional exponential
averaging may, optionally, be performed on the sensor and
temperature data by the main board processor before it is sent to
the host 85 via the wireless modem 84. Temperature control can also
be performed at regular, e.g. two second, intervals. Case heaters
87 (see FIG. 5) are controlled by a temperature sensor (e.g., part
of a temperature control system, e.g. like the "Temperature
Controls" 120, FIG. 4B) on the main board 83. If the temperature
reading is lower than the case temperature set point, heater
resistors 105 are turned on for the two second period. The
detectors 82 have a heater 87 and a cooler 88 (e.g. a heater and
thermal electric cooler, "TEC") to control the sensor temperature.
A second order temperature control loop is used to modulate the
sensor's heater and cooler to provide greater stability of the
sensor temperature. In one aspect, the heater or TEC power is
modulated so that the power input is related to the temperature
error (differential component) to create a
proportional-differential (PD) type of controller.
[0039] In one particular aspect, data packets containing all the
sensor and system data are sent to the host 85 every two seconds.
The host application software 86 takes the sensor data and applies
calibration information for the unit to generate proper gas
readings. The host application software 86 can issue commands to
read or write the non-volatile memory 83a on the main board 83,
allowing the calibration information to be stored in the gas
detector on the main board 83 rather than, e.g., with the host 85.
In another aspect this information is stored with the host. When
the host application software 86 is started, it requests the
calibration information from the main board 83 in the gas
detector.
[0040] Each GCIB 81 has two sensor input channels, two temperature
sensor input channels, and two infra-red source drive outputs. In
one aspect the drive outputs are pulsed at a 4.17 Hz rate and the
detectors 82 detect the variation in temperature as the lamps are
pulsed, creating a small alternating output voltage. A selected
narrow band filter (see the Filter, FIG. 2) filters the infra-red
radiation so that the detector is sensitive only to infra-red
radiation at a wavelength of interest (e.g. 3190 to 3330 nm for
methane, 3330 to 3540 nm for propane). If a gas with an infrared
absorption at that wavelength passes through the sensor, less light
will reach the sensor, and it will not see as large a temperature
variation, resulting in the amplitude of the output signal
decreasing. In one aspect, on the GCIB, this signal first goes
through a fixed 10 times gain low noise amplifier 81a (see FIG.
4A), followed by a gain stage with selectable 6, 12, 24, or 48
times gain. The signal is then rectified, inverted and filtered (on
the GCIB) to generate a DC voltage output that increases as the
sensor signal decreases due to absorption of the light. There is an
offset adjustment to set the base output voltage (similar to the
zero adjustment), and there is an output gain adjustment similar to
the span adjustment. The adjustments on the GCIB do not do the
actual sensor calibration, but rather set up a nominal offset and
gain for the sensor such that the output is within a valid
operating window. In one aspect, these adjustments on the GCIB are
done when a sensor is first connected to the board, after which
point calibration is handled through software parameters that are
stored in the non-volatile memory 83a on the main board 83 in the
gas detection unit.
[0041] As shown in FIG. 5, in the system 80 the wireless modem 84
is connected to an antenna 93. A power supply 90 provides power for
the GCIB's 81, the main board 83, the wireless modem 84, the
detectors 82, a power supply fan 94, a cooler 88, a pump 97 and an
air vacuum transducer (flow sensor) 98. The case heater resistors
105 are controlled by a case heater relay 104 powered from 120 VAC.
The case heater relay is used to open and close the circuit to
maintain the system within an operational temperature range, e.g.
above 25 degrees Celsius. The AC power plug 103, circuit breaker
101, and power switch 102 are for power control protection for the
entire unit. Power for a gas trap 96 flows through a switch 106 and
a 120 VAC plug 107. Optionally a filter FR filters moisture from
the gas. A fan regulator 100 provides 9 VDC current to power the
fans.
[0042] FIG. 4B shows a block diagram schematic for a main board
83.
[0043] In one aspect the main board 83 is a PIC micro based data
gathering and communications board or card, for receiving analog
and digital transducer information and converting it to digital
data to be sent to a computer or data acquisition system for
examination and/or archiving. A power supply ("External Power
Supply") supplies power. In one aspect the data is sent via RS 232
or, alternatively, over a wireless connection that is based on a
wireless modem 84. The data transmission circuitry is set up as a
population option where either the modem 84 or a daughter board
(not shown) containing the RS 232 is populated. Used in conjunction
with the GCIB's 81, the GCIB's interface via an interface 130
directly to the gas detectors 82 and do the digitization of the
sensor signals. Four connections to each sensor include power,
ground, gas channel output, and reference channel output
connections. A serial interface between the GCIB's 81 and the main
board 83 is used to read the digital sensor data.
[0044] In one embodiment, the main board 83 handles temperature
control of the unit and of the gas detectors 82. The case heater
105 is used to maintain a minimum unit temperature to prevent the
flame arrestors 87c from freezing. The flame arrestors have an
intake 87A and an outtake 87B. The heaters dissipate heat directly
to the required area when necessary. Whenever the temperature
reported by the onboard temperature sensor 110 is below the
specified threshold, the case heaters are enabled. The heater 87
and thermal electric cooler 88 control the temperature of the gas
detectors 82 using the fan 95. Proportional-differential control
(e.g. "Temperature Controls" 120) is used for the sensor
temperature: to enhance, and in one aspect to provide maximum
stability, of the temperature. The temperature set point is
specified, as well as a controller gain for both the heater and
cooler (multiplier for the proportional term), and a single damping
factor is applied to both the heater and cooler (multiplier for the
differential term). Control values for temperature control of the
unit are programmable via a microcontroller EEPROM 83c. The
temperature control values can be set in the host laptop software
and stored on the WSGD PCB microchip on the main board 83.
[0045] The main board 83 has three analog to digital channels 131
that accept either a 4-20 mA or 2-5V analog signal from external
sources. There are outputs to drive the case and sensor heaters as
well as the thermal electric cooler. The on-board temperature
sensor in the Temperature Controls module 120 is interfaced through
the analog-to-digital converter on the main board 83.
[0046] An on-board PIC microcontroller 140 reads the data from the
detectors 82, handles control of the unit and sensor temperatures,
and performs some processing of the data, such as averaging it to
improve the signal-to-noise ratio. It then transmits the
information to the host 85 via the wireless modem 84 (or via direct
RS 232 link, not shown). The main board 83 can drive LEDs 133 to
indicate the status of the card, main board processor and modem.
Non-volatile memory 83a in the microcontroller 140 is used to store
temperature control parameters, as well as the unit's gas
calibration data required by the host application software 86 to
convert the raw sensor readings into calibrated values. The cooler
88 cools the sensors and the power supply. In one aspect, the
cooler fan 95 is on top of the cooler 88.
[0047] FIG. 6 shows one typical display produced by a system
according to the present invention. One curve indicates methane
("C1"); one curve indicates propane ("C3") and one curve indicates
total gas content ("TOTAL GAS"). A numerical read out NR indicates
total gas ("tg"); methane content ("mc"); and propane content
("pc"). The date is indicated in the DATE column and the time
(actual real time) is indicated in minute increments in the TIME
column. The curves and the numerical read outs correspond to real
times in the TIME column and to actual depths in the DEPTH column.
Rate of penetration of the drill bit for increasing depths is
indicated by the ROP curve.
[0048] The present invention, therefore, in at least some, but not
necessarily all embodiments, provides a method for detecting gas in
a fluid, the method including flowing fluid bearing gas through a
gas trap apparatus, flowing gas trapped by the gas trap apparatus
to and through an infra-red gas detection system for detecting the
gas, the infrared gas detection system having a first processor and
apparatus for isolating absorption spectra of the gas, producing
with the infra-red gas detection system analog signals indicative
of levels of the gas, converting the analog signals to digital
signals with the first processor, transmitting the digital signals
from the first processor to a second processor, and producing with
the second processor digital signals indicative of the level of
gas. Such a method may have one or some (in any possible
combination) of the following: wherein the fluid is drilling fluid
and the gas is hydrocarbon gas from a wellbore; wherein the analog
signals are transmitted wirelessly; producing with the second
processor a visual display (screen, strip chart) of a level of the
gas; wherein the production of the analog signals and the
production of the digital signals is done in real time; wherein the
first processor includes an interface board for receiving the
analog signals, for converting the analog signals to the digital
signals, and for then transmitting the digital signals to the
second processor, the second processor including a host computer
for receiving the digital signals and for processing the digital
signals to produce an indication of level of the gas, the method
further including the interface board receiving the analog signals
and converting the analog signals to the digital signals, the
interface board transmitting the digital signals to the host
computer, and producing with the host computer an indication of the
level of the gas; wherein the host computer produces an indication
of a level of total gas in the fluid and/or displays said
indication; wherein the interface board has a programmable medium
programmed to calibrate the infra-red gas detection system and the
method further including calibrating the infra-red gas detection
system with the interface board; wherein the host computer provides
a user interface for conducting the method; conditioning the analog
signals with the interface board to reduce noise in said signals;
wherein the infra-red gas detection system has gas sensor apparatus
and there is no physical reaction between the gas and the gas
sensor apparatus; controlling temperature of the infra-red gas
detection system; wherein the infra-red gas detection system
includes the first processor and the infra-red gas detection system
is in an enclosure and heater apparatus and cooling apparatus are
connected to the enclosure for controlling temperature therein;
wherein the infra-red gas detection system is portable; wherein the
gas is hydrocarbon gas; wherein the hydrocarbon gas is methane
and/or propane; wherein the infra-red gas detection system includes
a gas detector with a detection channel and a reference channel,
the method further including detecting with the detection channel
infra-red radiation absorbed by the gas, and compensating with the
reference channel for variations in the gas; filtering moisture
from the gas prior to flowing the gas to the infra-red gas
detection system to inhibit or prevent the generation of false
readings due to moisture; and/or wherein the infra-red gas
detection system includes an infra-red lamp, an infra-red lamp
drive, and a gas sensor and the interface board provides an
interface between the infra-red lamp drive and the gas sensor.
[0049] The present invention, therefore, in at least some, but not
necessarily all embodiments, provides a method for detecting gas in
drilling fluid, the method including flowing drilling fluid bearing
hydrocarbon gas from a wellbore through a gas trap apparatus;
flowing gas trapped by the gas trap apparatus to and through an
infra-red gas detection system for detecting the hydrocarbon gas,
the infrared gas detection system having narrow band infrared
filter apparatus for isolating absorption spectra of the
hydrocarbon gas; producing with the infra-red gas detection system
analog signals indicative of levels of the hydrocarbon gas;
transmitting the analog signals to a first processor for converting
the analog signals to digital signals; transmitting the digital
signals from the first processor to a second processor, producing
with the second processor digital signals indicative of the level
of hydrocarbon gas; the first processor including an interface
board for receiving the analog signals, for converting the analog
signals to the digital signals, and for then transmitting the
digital signals to the second processor; the second processor
including a host computer for receiving the digital signals and for
processing the digital signals to produce an indication of level of
the gas; the method further including the interface board receiving
the analog signals and converting the analog signals to the digital
signals; the interface board transmitting the digital signals to
the host computer; producing with the host computer an indication
of the level of the gas; wherein the infra-red gas detection system
has gas sensor apparatus and there is no physical reaction between
the gas and the gas sensor apparatus; controlling temperature of
the infra-red gas detection system; wherein the infra-red gas
detection system includes the first processor and the infra-red gas
detection system is in an enclosure and heater apparatus and
cooling apparatus are connected to the enclosure for controlling
temperature therein.
[0050] The present invention, therefore, in at least some, but not
necessarily all embodiments, provides a system for detecting gas in
a fluid, the system including an enclosure; an infra-red gas sensor
apparatus within the enclosure; an interface board apparatus within
the enclosure and in communication with the infra-red gas sensor
apparatus; analog signal apparatus in the infra-red gas sensor
apparatus for producing analog signals indicative of a level of gas
in a fluid; conversion apparatus on the interface board apparatus
for converting the analog signals to digital signals; and
transmission apparatus on the interface board apparatus for
transmitting the digital signals to a host system.
[0051] In conclusion, therefore, it is seen that the present
invention and the embodiments disclosed herein and those covered by
the appended claims are well adapted to carry out the objectives
and obtain the ends set forth. Certain changes can be made in the
subject matter without departing from the spirit and the scope of
this invention. It is realized that changes are possible within the
scope of this invention and it is further intended that each
element or step recited in any of the following claims is to be
understood as referring to all equivalent elements or steps. The
following claims are intended to cover the invention as broadly as
legally possible in whatever form it may be utilized. The invention
claimed herein is new and novel in accordance with 35 U.S.C. .sctn.
102 and satisfies the conditions for patentability in .sctn. 102.
The invention claimed herein is not obvious in accordance with 35
U.S.C. .sctn. 103 and satisfies the conditions for patentability in
.sctn. 103. This specification and the claims that follow are in
accordance with all of the requirements of 35 U.S.C. .sctn. 112.
The inventors may rely on the Doctrine of Equivalents to determine
and assess the scope of their invention and of the claims that
follow as they may pertain to apparatus not materially departing
from, but outside of, the literal scope of the invention as set
forth in the following claims. All patents referred to herein by
number are incorporated fully herein for all purposes.
* * * * *