Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
DRILLING FLUID GAS TESTING SYSTEM AND METHOD
Background of the Invention
_ _ _ _
This invention is related to the automated testing
of earth Barlow drilling fluid fox the content of combs-
- 5 title gas that is returning to the earth surface during the
drilling operation.
In the prior art such testing for combustible gas
concentrations in returning drilling fluids has been done by
physically removing a sample of the returning drilling mud
in a small container and placing the container in an
instrument that operates to extract gaseous material from
the sample and analyze it for the presence of one or more
combustible gases. In this testing, the sample must be
taken by an individual and inserted into the testing
apparatus then aster the testing is complete the sample
removed and the equipment cleaned and prepared for testing
a subsequent mud sample. Use of this equipment and prove-
dune is cun~ersome in that a technician must physically
remove the sample and perform -the testing procedures.
While this might be quite acceptable for an occasional test
the mud's condition it is tedious, awkward and extremely
expensive for a continuous operation that would follow a
continuous twenty four hour per day drilling operation.
One object of this invention is to provide an
I apparatus and an ass wilted method that overcome the
aforementioned disadvantage of the prior art equipment and
procedures
Still, another object of this invention is to
provide a system for measuring the relative concentration of
combustible gases in the returning drilling mud from an earth
Barlow drilling operation wherein the apparatus can be
operated on a substantially continuous basis and provide a
numerical indication of the relative gas concentration to the
drilling rig operator and also provide the same information for
recording or transmittal to a remote location for reporting.
Specifically, the invention relates to a system for
measuring the relative gas concentration in drilling mud
returning to the earth surface from an earth Barlow while
being drilled, comprising: a means to continuously extract a gas
sample from a return mud flow of a drilling rig; means receiving
the was sample in a gas sample flow stream to measure the
relative concentration of combustible gases in the gas sample
including a catalytic sensor with a differential electrical
signal output; means to sample the electrical signal output and
derive an electrical data signal representative of the relative
combustible gas content of the gas sample; means connected to
the means to sample to display a numerical representation of the
electrical data signal for interpretation by a drilling rig
operator or the like.
In its method aspect the invention relates to a method
of measuring the relative combustible gas concentration of gas
carried in drilling mud returning to the earth surface from an
earth Barlow while it is being drilled, comprising the steps
of: taking a gas sample from a flow of drilling mud at the
earth surface, passing the gas sample through a means to measure
having a catalytic sensor measuring the relative combustible gas
concentration of the gas sample and producing a sensor
electrical output signal representative of the relative
combustible gas concentration in the gas sample; sampling the
sensor electrical output signal to derive an electrical data
signal representative of the relative combustible gas
concentration of the gas sample and processing the electrical
data signal to derive and display a numerical value
representative of the relative combustible gas concentration in
the drilling mud.
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Various other advantages and features of this invention
will become apparent to those skilled in the art from the
following discussion taken in conjunction with the accompanying
drawing, in which:
Description of the Drawing
The sole drawing is a pictorial diagram illustrating in
schematic form the system of this invention and including a
drilling mud flow solid separator with a gas collecting device
connected to the gas sampling and testing apparatus, and
connected to a numerical display, a recorder and a device for
transmission to a remote location
The following is a discussion and description of
preferred specific embodiments of the system, apparatus and
method of this invention, such being made with reference to the
drawing whereupon the same reference numerals are used to
indicate the same or similar parts and/or structure. It is to
be understood that this discussion and description is not to
unduly limit the scope of the invention.
Detailed Description
The gas testing system of this invention is shown in
the pictorial diagram of Fig. 1 and it includes several general
components that function together to form the complete system.
The gas sample extractor lo collects a sample of gas from the
drilling mud of an earth Barlow drilling rig and communicates
the sample into a gas handling conduit system, indicated
generally at 12, where it is cooled, heated and tested for
combustible gas content that exhaust -into the atmosphere. An
electronic circuit, indicated generality 14, is connected to
several elements of the gas handling conduit system to control
their operation and receive data therefrom with the output of
the electronic circuit being to a display devices, indicated
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generally at 16. The display devices include an output for
the drilling rig operator to watch, a recording device, and
if required the capability ox presenting the information for
transmission to a remote monitoring and/or recording
5 location.
In extracting the gas sample from the drilling mud
this is done at the earth surface at a location relatively
close to the point at which the drilling mud exits the
annular return flow passage of the Barlow and before the
10 mud is returned to the Barlow. In a typical drilling rig
a mud flow conduit 18 deposits drilling mud into a solids
separator device, indicated generally at 20, which is known
in the trade as a "shale Shaker The solids separator 20
includes a tank 22 that has a vibrating screen 24 mounted
15 therein. Mud flow from conduit 18 is onto the top of screen
24 whereupon it flows across the screen in a relatively thin
layer as indicated at 26. This flow moves from the screen
24 forming a curtain 28 of drilling mud between the end of
screen 24 and the residual quantity of mud 30 residing in
the bottom portion of tank 22. Mud flow curtain 28 forms
substantially an inclined wall of mud flowing between the
end of screen 26 and the residual mud level 30~ Sample
extractor 10 includes a generally conically shaped hood 32
resembling a funnel with the enlarged portion downward and
I the smaller portion extentind upward and joining a support
conduit 34. The upper end portion of support conduit 34 is
connected by a gas sample transfer conduit 36 connecting it
with gas sample handling conduit system 12. The position of
hood 32 is preferably generally positioned as illustrated
with the inlet or most enlarged portion thereof positioned
above shale shaker screen 24 with support conduit 34 extend
in upward therefrom. The inlet of hood 32 is placed with
its inlet below the normal mud flow level over screen 24 so
the mud will contact the exterior of hood 32 and flow around
it while roving over the screen. This somewhat contains yes
as it leaves -the mud and provides a substantially undiluted
gas sample flow for testing and analysis.
The gas handling conduit system 12 receives the
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gas sample flow in transfer conduit 36. The gas sample
flow is moved by a main yes sample pump 38. Movement of
the gas sample flow is detected by a pressure switch 40
connected in fluid communication with a conduit from the
output of pump 38. A flow indicating a light emitting
diode functioning as an indicating lamp is connected with
pressure switch 40 and positive an negative voltage sources
from a power supply (not shown) to signal an operator that
gas flow is present in this system.
When a gas sample is extracted it may contain a
certain quantity of liquid or liquefiable elements that are
preferably removed prior to testing and in order to prevent
damage to the apparatus. For this purpose a condenser
having a cooling coil 44 is connected to the output of pump
38. Cooling coil 44 is exposed to a flow of preferably
cooler than ambient air. The output of cooling coil 44 is
connected to the input of a coalescing filter 46 where
condensation of extraneous liquid material can occur and
this material can be removed from the jilter periodically
as desired. Coalescing filter 46 is provided with a gas
sample exhaust and with a gas sample outlet. A gas sample
exhaust is used to exhaust to the atmosphere a portion of
the extracted gas sample that will not be used in the actual
sampling or testing process. The typical flow of gas
through pump 38 is substantially in excess of that needed
in the measuring or testing portion of this system In
order to insure a flow of recently extracted sample gas for
the measuring and testing procedures the quantity of sample
extracted is in excess of that actually needed for the test
and the unused quantity of gas is discarded through unused
sample exhaust 48.
The gas outlet from coalescing filter 46 is
connected to a heating coil 50 where the gas sample flow is
heated so any remaining moisture or liquid materials therein
will remain in gaseous suspension until the measuring and
testing procedure is completed end the analyzed gas sample
is exhausted to the atmosphere. The output of heating coil
50 is connected to a gas sample flow dilution circuit used
for dilution of the gas sample with air when the gas sample
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contains high concentrations of combustible materials The
gas sample flow dilution circuit has an air dilution inlet
valve 52 in a loop with a metering valve to admit air and
mix it with the gas sample in a predetermined ratio This
dilution valve 52 is a two position valve with its inlet
connected to the outlet of heating coil 50 and the valve's
outlet connected to dilution valve outlet conduit 54. A
valve bypass look includes a valve bypass loop conduit 56
connected in fluid communication with both the inlet and the
outlet conduits to dilution valve 52 with a metering or
control valve 58 mounted therein. A dilution air inlet Z0
is provided to admit air into the gas sample handling
conduit system. Dilution air inlet 60 is connected to a
flow indicator 62 that it in turn connected to a second
inlet ox dilution valve 52.
With dilution valve 52 positioned as shown gas
sample flow is through conduit 54 with a very small portion
of the gas sample flow through conduit 56. With dilution
valve 52 shifted to the other position gas sample flow
through conduit 54 is blocked and the gas sample flow is
directed through conduit 56 and metering valve 58. Air is
admitted through dilution air inlet 60 and dilution valve
52 into conduit 54 so the concentration of the gas sample
downstream of the junction of conduit 54 and conduit loop
56 is diluted with air. Metering valve 58 is used to adjust
the dilution mixture of the gas sample The outlet from the
dilution circuit is through conduit 54 joining one inlet of
a purge valve 64.
Purge valve 64 is a two position valve used for a
purging cycle in conjunction with initializing the combs-
title gas concentration measuring device. The second inlet
of purge valve 64 is connected to an air inlet 66. With
purge valve 64 positioned us shown gas sample flow is
through the valve prom one inlet to the outlet and into the
housing of the was simple testing device 70. When purge
valve 64 is actuated to be displaced to its second position
the previous gas sample flow through the valve is blocked
and air inlet 66 is introduced into the gas sample flow
stream exclusively. Purge value 64 is use for an
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initializing procedure to be described in the following.
The gas sample tester or combustible gas concern-
traction measuring device includes a chamber containing two
sets of beads made of a catalytic material and mounted with
heating elements 72 and 74. The heating elements are
resistive type heating elements that are closely associated
with the catalytic beads and joined in a series or end to
end fashion. The heating elements warm the catalytic beads
so their temperature is elevated sufficiently that a gala-
lyric reaction will be formed with combustible gases contained within the gas sample flow. When the gas sample
has a quantity of combustible material a catalytic reaction
will be formed and the beads will generate additional heat
whereupon the resistive heating elements will measurably
change in resistance. This measurable change is used in
an electrical bridge type circuit to derive a relative
indication of combustible gas content in the gas sample
flow. Electrical conductor 76 joins one end of bead hefting
element 74, and electrical conductor 80 joins the junction
of the bead heating elements 72 and 74.
Sample pump 82 is connected to the outlet of the
sample tester housing and used to pull the gas sample
through the preceding conduit portions of the system from
coalescing filter 46. The outlet of sample pump 82 is
connected to the inlet of a flow indicator 84 with the
output of flow indicator 84 bring exhausted to the atoms
phone. Flow indicator 84 is an operational indicator to
provide a technician an indication of the flow of gaseous
material through sample pump 82. The exhaust from flow
indicator 84 can be simply discharged to the atmosphere or
to any suitable apparatus for discarding such samples.
Electronic circuits 14 are shown contained within
a dashed line box. Generally, the electronic circuit
includes a whetstone bridge to operate with the heating
elements in sample tester 70, associated instrumentation
amplifiers, an zeroing or initializing and referencing
circuit, and a scaling and output circuit with the outputs
to devices or visual display, recording and transmission to
I a remote location
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Sample tester 70 has both of its heating element-
resistor elements I and 74 connected to the electronic
circuit by wires 76, 78 and 80 as illustrated. Wires 76
and 78 are connected in series with a balance bridge
resistor 90. Positive voltage is applied to one side of
the bridge as illustrated from a power supply. Balance
bridge resistor 90 is a variable resistor with the wiper
92 connect-d as one input to an instrumentation amplifier
94. Two elements of the bridge circuit are formed by the
lo catalytic bead heating elements 72 and 74 and these are
connected to bridge balance resistor 90 so that portions
of the resistor on either side of wiper 92 form the other
pair of bridge resistive elements. The center connection
of the catalytic bead heating elements is joined by wire
80 with a second input of instrumentation amplifier 94.
Instrumentation amplifier 94 is a differential amplifier
with two inputs and a Nolan voltage input. Initially
balance resistor 90 is adjusted for a zero output from
amplifier 94 for a condition with sample tester 70 exposed
to air that does not contain combustible gasps. When
combustible gases pass through sample tester 70 the
resistance of catalytic bead heaving elements 72 and 74
changes due to the catalytic heating effect. This change
in resistance will result in a different -total resistance
across both of the heating elements and at its center
junction. This change results in a different voltage
across bridge balance resistor 90 and at its wiper. The
bridle resistor wiper voltage and the heating element
center voltage are supplied as voltage signals are supplied
as inputs to instrumentation amplifier 94. I've output of
this amplifier 94 is the voltage signal indicative of the
change in resistance in the heating elements due to the
catalytic reaction and that is in turn indicative of the
relative portion of combustible gases in the gas sample
passing through sample tester 70.
The electrical output from instrumentation amply-
lien 94 is connected to the input of a track and hold
amplifier 96. The output from track and hold amplifier 96
is supplied to the input of a range switching divider
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circuit 98 that supplies output data signals to a panel
display ~etex 100 and to a recorder 102 for use by drilling
rip operating personnel. The output from track and hold
amplifier 96 is also supplied to a remote recorder and
transmitter 104 used for relaying this data to a remote
location.
In the initialization or zeroing of this apparatus
a zeroing logic circuit 106 is used to control the system's
functions temporarily. Zeroing logic circuit 106 contains
a timer that periodically causes the system to go through
the initialization procedure. Typically this time period
is selected to be between one and two hours. First, when
the initializing procedure begins track and hold amplifier
96 is enabled into its hold position by a pulse or other
signal supplied through line 108. A storage capacitor lug
connected to track and hold amplifier 96 is used to store
the present output signal of the amplifier and to maintain
this output signal through the duration of the initialize-
lion procedure. Typically time for the initializing pro-
seedier will be in the range of about two to three minutes Next solenoid driver 112 is enabled through line 114 and
it in turn actuates the solenoid of purge valve 64 through
line 116. When the solenoid is actuated the purge valve
64 shifts to the position other than that shown whereupon
the gas sample flow is blocked and air is admitted to the
fluid circuit through purge valve air inlet 66. This air
flows through the chamber of sample tester 70 and exposes
the catalytic elements to air that does not contain a
significant quantity of combustible gases.
This purging air flow continues through gas sample
tester 70 for a short period of time to purge the chamber of
con~ustihle gases. Aster this time has elapsed zeroing
logic 106 will examine the output ox instrwnentation of
amplifier 94 as compared with a zero voltage. This was done
by a zero voltage Capote amplifier ~18 that has one
input connected to the output ox instrumentation difference
amplifier 94 and the other input connected to ground.
Zeroing logic 106 operates in a digital mode and has a
counter that counts upward from zero. us the counting
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proceeds the digital count output signal is directed to a
digital to analog converter 120 and from there via a
connecting line 122 as an analog voltage to a nutting or
offset input of instrumentation amplifier 94. As the
nutting voltage arriving at instrumentation amplifier 94
increases the output voltage of this amplifier will decrease
accordingly. us the output of amplifier 94 decreases it is
compared with a zero voltage by zero voltage comparator
amplifier 11~. As the counting progresses a point will be
reached when the output of zero voltage comparator amplifier
118 is substantially zero or slightly there above. At this
point the counting will stop and the nutting voltage will be
held at that determined level.
When counting steps the electrical output of same
pie tester 70 has been initialized or zeroed. Next, sole
nod ill will be again actuated to cause the solenoid of
purge valve 64 to actuate the valve and again position it as
illustrated thereby again returning the gas sample flow
through sample tester 70~ after this occurs track and hold
amplifier 96 will be switched from the holding mode to a
tracking mode and the output of instrumentation amplifier 94
again passes through amplifier 96 and be supplied to output
portions of the circuit.
The gas testing system of this invention provides
an indication of the relative quantity of combustible gas in
the gas sample over a very broad range of concentrations.
Because the system provides a relative indication of
concentrations the output data from the instrument is in
terms of units ranging prom zero to ten thousand By way
ox reference a reading of 200 units is approximately
equivalent to a test gas sample containing one percent
methane. This results in a correlation of unit readings
that is approximately equivalent to unit readings that would
be requited if the tests were done using the prior art
manual procedure of taking a Bud simple and extracting the
gay to arrive at the gas concentration information.
Because of the extremely wide range of gas concentrations
that can be detected by this apparatus and the relative
accuracy of the sampling device it is necessary to dilute
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the gas sample for higher concentrations of combustibles.
Along with dilution of the gas sample, it is necessary to
adjust the output range of the display devices in order to
accurately report the relative combustible gas concentra-
lions. In order to accomplish Tess task a range and dilution logic circuit 130 is provided. Generally, range
and dilution logic circuit 130 senses the output of track
and hold amplifier 96 and depending upon its value and
preceding sequence it functions to appropriately adjust the
range of outputs to the display devices 16.
The output of track and hold amplifier 94 is
connected to the input of a low threshold comparator
amplifier 134 and the input of a high threshold comparator
amplifier 136. The other inputs to these threshold
comparator amplifiers are provided from a voltage diviner
network where a referenced voltage V rev is divided above
ground by a first resistor 140, a second resistor 142 and a
third resistor 144 providing a low threshold reference
voltage and a high threshold reference voltage on opposite
sides of resistor 142. The outputs of comparator amplifiers
134 and 136 are connected to separate inputs of range and
dilution logic circuit 130. One output from logic circuit
130 is to range switching dividing 98. Another output of
logic circuit 130 is to a solenoid driver 146 that is in
turn connected to actuate the solenoid of air dilution
valve 52 through a connecting line 148.
Dilution logic circuit 130 has a low range mode
of operation and a high range mode of operation. In the low
range mode of operation the output signal from low threshold
comparator amplifier 134 is used in range and dilution logic
circuit 130. This circuit junctions (by simple logic
operations or steps, not shown) to activate range switching
divider 98 to pass the output signal from track and hold
amplifier 96 directly to panel meter 100 end recorder 102
in a low range scale rode. While this is occurring a
feedback signal from the low threshold comparator 134 is
presented through line 150 to zeroing logic circuit 106 so
the logic circuit will be provided with data indicating the
point of operation in the low range mode. For operation in
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the low range initializing as described above will occur at
the predetermined intervals However, preferably for
operation in the low range mode above a predetermined value
of units the initializing will not occur repetitively.
When the relative concentrations of combustible
gases rises sufficiently to cross over from the low range
mode Jo the high range mode dilution of the air sample
begins. The transition for changing between the low range
mode of operation and the high range mode can be selected
at approximately 900 units. When this condition occurs
range and dilution logic 130 is activated by a changed
output voltage of high threshold comparator amplifier 136.
When this occurs several things happen. First, solenoid
driver 146 is signaled to actuate the solenoid of air
dilution valve 52. This action shifts the valve to the
position other than that shown whereupon air enters the gas
sample circuit through air inlet 60 and dilution air flow
indicator 62. The gas sample then passes through metering
valve 58 and mixes with the air to provide an air diluted
gas sample. my way of example the dilution ratio could be
conveniently selected at ten parts of air to one part of gas
sample thus requiring shifting of the scale range of the
instrument by a ten to one ratio. In accordance with this
choice metering valve 58 must be set to the predetermined
10 to l ratio flow in accordance with the movement of air
through inlet 60. The second occurrence in dilution logic
circuit 130 is that range switching divider circuit 98 is
switched from the low range of operation to a high range of
operation in order that panel meter 100 and recorder 102
will properly display the correct units of measure
corresponding to the appropriate relative gas concentrations
present in the extracted gas sample.
The device for remote recording and transmitting
of the data signal is provide with one input directly from
track and hold amplifier 96 and another input from range and
dilution logic circuit 130 in order to record the signal
data and the range data separately. It is to be noted that
if desired the data supplied to remote recorder and
transmitter 104 could be the same as that supplied to panel
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meter 100 and recorder 102.
As long as the system is operating in the high
concentration range mode zeroing or initializing of the
system will not occur. This is preferable in order to
provide the drilling rig operators with a continuous flow of
data or safety reasons owing to the relative high gas
concentrations involved and thy potential dangerous situp-
lions that might be encountered. When gas concentrations
began to decrease and fall below that normally reported in
the high range mode of operation, approximately 900 units,
the input voltage to the threshold comparator amplifiers
will drop to a point below that which changes the output of
high threshold comparator ~nplifier 136. In this signal
condition range and dilution logic 130 continues operation
in the high concentration mode until the gas concentration
drops significantly to about 800 units. Continued operation
in the high concentration mode is done to prevent unneces-
spry switching between the modes of operation for conditions
when the gas concentration oscillates about the 900 unit
level or progresses to a higher level. Once the combustible
gas concentration drops below 800 units range and dilution
logic 130 will again recognize the input from low threshold
comparator amplifier 134. At this point in the operation
when the output of low threshold comparator amplifier 134
is again recognized range and logic circuit 130 will respond
accordingly signaling range switching divider 98 and remote
recorder and transmitter 104 indicating a change to the low
range scale. Range switching divider 98 will accordingly
adjust its output to panel meter 100 and recorder 102 to
the 1:1 scale used in the low range mode
In the above described gas sampling system the
devise can be incorporated with a drilling recording data
handling and transmission system to provide a complimentary
element of information for the drilling rig operators. In
the use and operation of the gas tester system of this
invention it is seen that it provides a substantially
continuous display of critical data concerning the presence
of combustible gases in the drilling mud for reference and
use by the drilling rig operators. The apparatus can
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operate substantially unattended and provide data on a
continuous basis which is a significant improvement over
prior art devices requiring technicians to sample the
drilling mud and provide tune data. Awls is apparent from the
applicant described method and apparatus a quite effective
improvement has been provided for monitoring the relative
combustible gas concentration in returning drilling mud.
As will become apparent from the foregoing
description of the applicant's Drilling Fluid Gas Tester
System and Method, a relatively complete system is provided
to continuously monitor combustible gases in drilling mud
returning to the earth surface during well drilling. The
system is operable in a substantially continuous manner to
provide relative combustible as content data to drilling
rig operators without requiring a technician to physically
sample the drilling mud and test it for combustible gas
concentrations.
Although specific preferred embodiments of this
invention have been described in detail in the preceding
description, this description is not intended to limit the
invention to the particular form or embodiments disclosed
herein since they are to be recognized as illustrative
rather than restrictive and it would be obvious to those
skilled in the art that the invention is not so limited.
Thus, the invention is declared to Cover all changes and
modifications of the specific example of the invention
herein disclosed for purposes of illustration which does not
constitute departures from the spirit and scope of the
invention.
