TECHNICAL FIELD
[0001] The present invention relates to a method and system of
detecting pipeline exposure in the crossing of bodies of water such as
streams, rivers, lakes, muskeg and ponds.
BACKGROUND
[0002] Pipelines often cross bodies of water such as streams, rivers,
lakes, muskeg and ponds. Through the course of time, a pipeline which was
buried at the time of installation underneath a covering material may
become exposed to the water through flotation, scour, erosion, dredging and
other causes. Exposure may include the thinning of the covering material so
that the pipeline is either partially or completely exposed to the body of
water
[0003] I n many cases there is a need to detect such exposure because
the change in support of the pipeline may generate stresses on the pipeline
material, a condition that can lead to failure of containment of the fluid in
the pipeline.
[0004] I n addition, the process of determining whether the pipeline has
been exposed may not be easily executed during inclement weather, flood
events or other mitigating circumstances. Also, the use of in-line inspection
methods may not provide sufficiently timely information to prevent
operational problems for the pipeline.
[0005] An ideal method would be able to report such exposure in
nearly real time, and would not require installation of equipment along the
portion of pipeline crossing the bodies of water.
SUMMARY OF THE INVENTION:
[0006] According to an embodiment of the invention, there is provided
a method and system of an arrangement of sensors that can be used to
detect changes in burial conditions of a pipeline buried under a body of
water.
[0007] According to an embodiment of the invention, there is provided
a system for identifying pipe exposure in a crossing of a body of water, the
system comprising: a distal upstream sensor at a first location upstream
and distal to the crossing of the body of water for obtaining a first
temperature of the pipe at the first location; a proximal upstream sensor at
a second location upstream and proximal to the crossing of the body of
water for obtaining a second temperature of the pipe at the second location;
a downstream sensor at a third location downstream from the crossing of the
body of water for obtaining a third temperature of the pipe at the third
location; and a temperature estimation means for obtaining a temperature
rate of change by using the first obtained temperature and second obtained
temperature, and estimating the temperature of the pipe at the third
location.
[0008] According to an embodiment of the invention, there is provided
a method for identifying pipe exposure in a crossing of a body of water, the
method comprising: obtaining a first temperature of a fluid carried by a pipe
at a first location upstream and distal to the crossing of the body of water;
obtaining a second temperature of the fluid at a second location upstream
and proximal to the crossing of the body of water; obtaining a third
temperature of the fluid at a third location downstream from the crossing of
the body of water; generating an estimate of the temperature of the fluid at
the third location by establishing a rate of change of temperature of the fluid
using the obtained first temperature and the obtained second temperature
and the distance between the first and second locations; and identifying pipe
exposure when there is a deviation between the estimated temperature and
the obtained third temperature.
[0009] According to an embodiment of the invention, there is provided
a method for identifying pipe exposure in a crossing of a body of water, the
method comprising: obtaining fluid temperature of a fluid carried in a
pipeline from at least two locations along the pipeline and upstream of a
underwater pipeline crossing and separated by a distance sufficient to
measure small difference in temperature changes; determining a rate of
temperature change over the distance between the at least two locations;
estimating a temperature of the fluid carried along a pipeline at the location
downstream of the underwater pipeline crossing from the product of the rate
of temperature change and the distance of the downstream location from a
location upstream of the underwater crossing; and identifying pipe exposure
when there is a deviation between the estimated temperature of the fluid at
the location downstream of the pipeline crossing with an obtained fluid
temperature at the location downstream of the pipeline crossing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Fig. 1 is a schematic representation of the system for detecting
pipeline exposure in the crossing of bodies of water showing a normal
condition where the pipeline is buried under the body of water;
[001 1] Fig 2. is a schematic representation of the system for detecting
pipeline exposure in the crossing of bodies of water showing an abnormal
condition where the pipeline is exposed to the body of water;
[0012] Fig. 3 is a graphical representation showing the effects pipeline
temperature when the depth of covering material above the pipeline is
reduced and the pipeline is exposed to a body of water that has a
temperature colder than that of the fluid contents of the pipeline;
[0013] Fig. 4 is topographical map of two sites (a northern crossing NC
and a southern crossing SC) of a commercial pipeline where showing the
placement of the two systems according to an embodiment of the invention;
[0014] Fig. 5 is a graph showing the change in pipe temperature
compared to the changing ground temperature (°C) over time (minutes) at
site SC of Fig. 4.
[0015] Fig. 6 is a graph showing the temperatures at sensors SC-1 and
SC-2 and the temperature difference between these two sensors;
[0016] Fig. 7 is a graph showing temperature readings from the three
sensors (SC-1 US, SC-2 US, and SC-3 DS); and
[0017] Fig. 8 is a graph showing data obtained from an acoustic sensor
according to an embodiment of the present invention.
DETAILED DESCRIPTION
[0018] A schematic representation of a method and system for
detecting pipeline exposure in the crossing of bodies of water is shown in
Figs. 1 and 2. As shown in Fig 1, the system 2 comprises a plurality of
sensors 10, 12, and 14 for measuring the temperature of an underground
pipeline 20 for carrying a fluid 22 from an upstream source (not shown) to a
downstream destination (not shown) whilst passing under a body of water
24. As shown in Fig. 1, pipeline 20 is buried under a depth of covering
material (or sediment) 26. I n this condition, the covering material 26
separates the pipeline 20 from the water body 24.
[0019] The first sensor 10 is placed at a first location on the pipeline 20
that is upstream and distal to the crossing of the body of water 24 such as
streams, rivers, lakes, muskeg and ponds and obtains a first temperature of
the pipeline 20 at the first location. The second sensor 12 is placed at a
second location on the pipeline 20 that is upstream and proximal to the
crossing of the body of water 24 and obtains a second temperature of the
pipe at the second location. The distance between the first sensor 10 and
the second sensor 12 is a distance sufficient to allow the sensors 10 and 12
to normally detect a temperature difference of at least 0.01°C between them
during normal operation. It will be appreciated that in cases where the rate
of temperature change along the pipeline is very small, the distance between
sensors 10 and 12 may be increased.
[0020] The third sensor 14 is placed at a third location on the pipeline
20 downstream and is separated from the second sensor 12 by a sufficient
distance to place it on the pipeline 20 at a position beyond where the
pipeline 20 has traversed under the body of water 24. The third sensor 14
obtains a third temperature of the pipeline 20 at the third location.
[0021] A water temperature sensor 16 may be placed in close thermal
contact with the water body 24 to assist in the interpretation of the
information derived from the sensors 10, 12, and 14 by revealing the
temperature difference between the water body 24 and the pipeline fluid 22.
I n an embodiment, the water temperature sensor 16 can be used to
generate an estimate of the amount of pipeline 20 exposed to the water
body 24.
[0022] Each of the sensors 10, 12, 14, and 16, can each include a
signal transmission means 30, 32, 34, and 36 respectively for relaying the
obtained temperature information or processed information to a site remote
from the crossing. Suitable signal receiving means 40 at the remote site for
receiving and/or processing the obtained temperature information. Such an
arrangement would usefully be able to relay the temperature information, or
processed information, to the remote site where alarms could be raised and
perhaps action taken. Signal transmission means 30, 32, 34, and 36 could
comprise wired or wireless transfer. The system 2 could be powered with
mains power, battery power, solar or wind energy as best suits the situation.
A computer system 42 is provided for collecting the temperature data,
carrying out the instructions (i.e. a computer program) stored on computer
readable medium for estimating the temperature of the wall of the pipeline
20 at the third location and determining the degree of deviation the
estimated temperature is from the actual temperature at the third location,
and for communicating this information to a user, for instance.
[0023] Additionally and optionally, video or photographic equipment 44
may be included to provide supporting information about the status of the
pipeline 20. Furthermore, acoustic sensors 46 located at any one or all of
the first, second and third locations may be provided to reveal debris or
rocks impinging the pipeline 20. Each of sensors 10, 12, 14, and 16, can
each include a GPS (not shown) to precisely determine location.
Additionally, ground temperature sensors (not shown) may also be included
for measuring the temperature of the ground in the vicinity of the pipeline
20.
[0024] It will be appreciated that the measured temperature of the wall
of the pipeline 20 can be considered an approximate reflection of the
temperature of the fluid 22 in the pipeline 20. A number of factors will
determine the temperature of the fluid 22 in the pipeline 20. For example, a
pipeline 20 buried in soil will gradually change the temperature of the soil in
which it is buried, and by extension, the temperature of the fluid 22 within
the pipeline 20 will also be affected by the ambient temperature of the soil
surrounding the pipeline 20. The rate of temperature change of both the soil
and of the fluid 22 in the pipeline 20 will be affected by the difference in
temperature between the fluid 22 and the soil or surrounding environment,
and the thermal conductivity of the wall of the pipeline 20. Other factors
that affect the temperature of the fluid 22 in the pipeline include the nature
of the fluid 22, such as the specific heat, and the velocity of the fluid 22
through the pipeline 20.
[0025] According to an embodiment, the temperature of the wall of
pipeline 20 is measured at least at three locations. The first two locations
would normally be spaced some distance apart on the "upstream" side of the
crossing, and would, to the extent practical, be buried in similar conditions of
cover. The purpose of sensors 10 and 12 at the first and second locations is
to establish the rate of temperature change over a fixed distance where the
pipeline 20 is buried in a known condition of cover. The third sensor 14
measures the temperature of the pipeline 20 at a position located on the
downstream side of the body of water 24, and that this third sensor 14 be
installed in a manner similar to the first two sensors, with similar burial,
contact with the wall of the pipeline 20, and installation attachment.
[0026] The first two sensors 10, 12 establish a temperature of the wall
of the pipeline 20, and a rate of change of that temperature over a fixed
distance is calculated by the computer system 42. This allows the
cancellation or recognition of the effects of fluid velocity, specific heat,
pipeline wall thermal properties, and the temperature of the fluid 22 within
the pipeline 20. As shown in Fig. 1, were the pipeline 20 to be buried is
effectively in a non-aqueous environment such as under cover material 26,
one would expect the temperature measured at the location of the third
sensor 14 to be accurately predicted by applying the rate of change of
temperature with distance and calculating the temperature expected at the
distance on the downstream side of the crossing.
[0027] As shown in Fig. 2, if the environment surrounding the pipeline
20 were to become aqueous (such as seen in a washout condition whereby
at least a portion of the cover material 26 is washed out or missing), the
temperature at the third sensor 14 will be different than if the environment
were to be non-aqueous, simply because the specific heat of dry soil is
different than the specific heat of wet soil, and also because the movement
of water body 24 past the pipeline 20 would not allow the pipeline 20 to
stabilize the temperature of the moving body of water 24 in the same
manner as it might were the water to be static around the pipeline 20.
[0028] Shown in Fig. 3 is a graphical representation showing the
effects pipeline temperature when the surface (i.e. cover material 26) above
the pipeline 20 is reduced and the pipeline 20 is exposed to the body of
water 24 that has a temperature colder than that of the fluid contents 22 of
the pipeline 20. Under normal conditions where the pipeline 20 is buried
under sufficient cover material 26, it is expected that the temperatures
obtained by sensor 14 would not deviate significantly from the estimated
temperature. I f the depth of cover of the soil or cover material 26
overlaying the pipeline 20 were to change, then it is expected that the
typical rate that water would move over the pipeline 20 would also change,
resulting in a different rate of heat transfer between the wall of pipeline 20
and the surrounding wet soil.
[0029] In an extreme case, all of the soil or cover material 26 covering
the pipeline 20 may be removed in some locations and the temperature of
the surrounding water 24 would have a marked effect on the temperature of
the fluid 22 passing through the pipeline 20. For example, as shown in Fig.
3, in a situation where the depth of sediment (or cover material 26) over the
pipeline 20 is zero, the temperature as measured by sensor 14 is about 13°C
or 7 °C cooler than the temperatures measured by sensors 10 and 12. Thus,
by using the three sensors 10, 12, and 14 placed as described, changes in
the depth of cover of the soil/sediment or cover material 26 over the pipeline
20 can be detected, even though the product 22 in the pipeline 20 changes
in character and the rate of flow of the product 22 in the pipeline 20 may
change.
[0030] According to an embodiment, the computer 42 develops, and
maintains, and accesses a database of historical temperature measurements
for all sensors 10, 12, 14, and 16. It will be appreciated that the amount of
temperature deviation constituting an anomalous condition could be refined
as the behavior of the temperature of the fluid 22 in the pipeline 20 over the
seasons becomes better characterized. Additionally, the computer 42 has
access topographical, geographical, and geological information across the
entire network of pipelines as well as access to local weather conditions. The
computer 42 utilizes this additional information to determine whether a
particular anomaly or deviation at certain places along the pipeline 20 are
more likely than not to be an exposure of the pipeline 20.
[0031] According to another embodiment, there is also provided a
method to analyze information from at least two sensors to determine the
rate of temperature change with distance in the operating pipeline, and to
compare the rate of temperature change with distance in the portion of the
pipeline preceding the crossing, with the rate of temperature change on
either side of the crossing, and further seeking anomalous changes in that
rate of change of temperature. This method compensates for the effect of
changes in flow within the pipeline, changes of product flowing within the
pipeline, changes in the temperature of the product flowing in the pipeline,
and the seasonality of the surrounding environment of the pipeline. The
method also includes the use of information from optional additional sensor
or sensors placed in thermal contact with the water being crossed, and the
use of video or other photographic information to assist in the interpretation
of the data gathered by the system.
[0032] According to another embodiment, where there are multiple
crossings of the bodies of water 24, information from various sensors can be
reused. For example, sensor 10 can also function as sensor 14. I n another
embodiment, the system 2 comprises as few as one of each sensor 10 and
sensor 12 for calculating the rate of change of the temperature over a fixed
distance.
[0033] According to another embodiment, there is also provided a
method and system comprising two sensors 12 and 14 and a flow meter 48
or plurality of flow meters 48 for determining the rate of flow of the fluid 22
carried in the pipeline 20. I n this embodiment, an indication that there may
be an exposure of the pipeline 20 can be obtained by examining the readings
of the sensors 12 and 14 and flow meter 48. I n cases where the readings at
sensor 14 are shown to vary despite a constant flow, this would be a
considered an anomalous condition requiring further investigation.
[0034] While in the embodiments described above, the temperature of
the fluid 22 is obtained by taking the measurement of the temperature of
the wall of the pipeline 20, it will be appreciated that other methods of
measuring the temperature of the fluid 22 in the pipeline are contemplated.
These methods include various invasive or non-invasive temperature
sampling methods.
Example 1
[0035] Two systems according to an embodiment of the invention were
installed along two sites of a commercial pipeline in the province of British
Columbia. As shown in Fig. 4, the systems surround two water crossings (a
northern crossing C and a southern crossing SC). The southern crossing
site has sensors labeled as SC-1 US (Upstream), SC-2 US, and SC-3 DS
(Downstream) relative to the flow within the pipeline. The approximate
distance between SC-1 US and SC-2 US is about 10 meters. The
approximate distance between SC-2 US and SC-3 DS is about 12 meters.
[0036] Each site had the sensor units placed directly on the pipe with
adhesive and the covered with protective coatings.
[0037] Each sensor comprises a temperature sensor capable of sensing
temperature changes of about 0.002°C and an acoustic sensor.
[0038] The sensors were wired directly to a monitoring unit that
contains analog/digital electronics, cellular links, satellite links, batteries, a
solar panel, and a controller. The controller was programmed to check in
from time to time to relay information about what it has detected.
[0039] Shown in Fig. 5 is a graph showing the change in temperature
of one section of the pipeline compared to the changing ground temperature
(°C) over time (minutes).
[0040] Shown in Fig. 6 is a graph showing the temperatures at sensors
SC-1 US and SC-2 US and the temperature difference between these two
sensors over time. The actual temperature at SC-2 US is about 14 °C and
the temperature difference between SC-1 US and SC-2 is about 0.2°C. Since
the distance between the two sensors is about 10 meters, the calculated the
thermal gradient is 0.02°C per meter (i.e. about 0.2/10).
[0041] Based on this, the estimated temperature at SC-3 DS (i.e.
13.76°C) would be about 0.24°C (i.e. 0.02°C per meter x 12 meters) less
than the actual temperature at SC-2 US (i.e. about 14°C).
[0042] Fig. 7 additionally shows the actual readings from SC-3 DS in
addition to the readings at SC-1 US and SC-2 US. As shown, the actual
temperature reading at SC-3 DS is slightly less than 12°C which is much
lower than the estimated temperature for SC-3 DS (i.e. 13.76°C). This
indicates that the pipeline or a portion of the pipeline is exposed to water at
the water crossing.
[0043] Fig. 8 is a graph showing data from an acoustic sensor placed
proximal to the water crossing. The upwards deflection observed in the low
frequency band ( < 4 kHz) at around 19 minutes confirms that debris or a
rock carried in the water did contact the exposed portion of the pipeline at
the water crossing. Had the pipeline not been exposed at the water
crossing, there would no upwards deflection in the low frequency band
detected by the acoustic sensor,
[0044] The embodiments of the present application described above
are intended to be examples only. Those of skill in the art may effect
alterations, modifications and variations to the particular embodiments
without departing from the intended scope of the present application. In
particular, features from one or more of the above-described embodiments
may be selected to create alternate embodiments comprised of a sub
combination of features which may not be explicitly described above. I n
addition, features from one or more of the above-described embodiments
may be selected and combined to create alternate embodiments comprised
of a combination of features which may not be explicitly described above.
Features suitable for such combinations and sub combinations would be
readily apparent to persons skilled in the art upon review of the present
application as a whole. Any dimensions provided in the drawings are
provided for illustrative purposes only and are not intended to be limiting on
the scope of the invention. The subject matter described herein and in the
recited claims intends to cover and embrace all suitable changes in
technology.

CLAIMS
1. A system for identifying pipe exposure in a crossing of a body of
water, the system comprising:
a distal upstream sensor at a first location upstream and distal to the
crossing of the body of water for obtaining a first temperature of the
pipe at the first location;
a proximal upstream sensor at a second location upstream and
proximal to the crossing of the body of water for obtaining a second
temperature of the pipe at the second location;
a downstream sensor at a third location downstream from the crossing
of the body of water for obtaining a third temperature of the pipe at
the third location;
a temperature estimation means for obtaining a temperature rate of
change by using the first obtained temperature and second obtained
temperature, and estimating the temperature of the pipe at the third
location.
2. The system of claim 1 wherein the temperature estimation means
comprises a computer system.
3. The system of claim 1, further comprising a water temperature
sensor.
4. The system of claim 1, wherein the distal upstream sensor, the
proximal upstream sensor, and the downstream sensor each comprise a
signal transmission means for relaying the obtained temperature
information or processed information to a site remote from the crossing.
5. The system of claim 1, further comprising a flow meter.
6. The system of claim 1, further comprising an acoustic sensor.
7. A method for identifying pipe exposure in a crossing of a body of
water, the method comprising:
obtaining a first temperature of a fluid carried in a pipe at a first
location upstream and distal to the crossing of the body of water;
obtaining a second temperature of the fluid at a second location
upstream and proximal to the crossing of the body of water;
obtaining a third temperature of the fluid at a third location
downstream from the crossing of the body of water;
generating an estimate of the temperature of the fluid at the third
location by establishing a rate of change of temperature of the fluid
using the obtained first temperature and the obtained second
temperature and the distance between the first and second locations;
identifying pipe exposure when there is a deviation between the
estimated temperature and the obtained third temperature.
8. The method of claim 7 further comprising generating a historical
database of the obtained first, second and, third temperatures.
9. The method of claim 7 further comprising accessing a databases
containing topographical, geographical, and/or geological information
along a route of the pipe.
The method of claim 7 further comprising accessing local weather
nformation along a route of the pipe.
11. The method of claim 7 wherein the step of identifying pipe exposure
comprises:
accessing a historical database of the obtained first, second, and third
temperatures and estimated third temperatures;
comparing the obtained third temperature to the historical database of
obtained third temperatures and estimated third temperatures;
determining whether the obtained third temperature deviates
significantly from the historical database of obtained third
temperatures;
wherein it is indicative of pipe exposure when the obtained third
temperature significantly deviates from the historical database of
obtained third temperatures.
12. The method of claim 11 wherein the step of identifying pipe exposure
further comprises:
accessing a database of topographical, geographical, and/or geological
information along the route of the pipe; and
determining whether the deviation at the third location is more likely
than not to be indicative of the exposure of the pipe.
13. The method of claim 7 further comprising obtaining a temperature of
the body of water.
14. The method of claim 7 further comprising obtaining acoustic
information from the pipe.
15. The method of claim 7 further comprising obtaining the rate of flow of
the fluid.
16. The method of claim 7 wherein the obtained first, second, and third
temperatures of the fluid, are obtained by obtaining the temperature of
the wall of the pipeline at the first, second, and third locations.
17. A method for identifying pipe exposure in a crossing of a body of
water, the method comprising :
obtaining fluid temperature of a fluid carried in a pipeline from at least
two locations along the pipeline and upstream of a underwater
pipeline crossing and separated by a distance sufficient to measure a
small difference in temperature changes;
determining a rate of temperature change over the distance between
the at least two locations;
estimating the temperature of the fluid carried along a pipeline at a
location downstream of the underwater pipeline crossing from the
product of the rate of temperature change and the distance of the
downstream location from a location upstream of the underwater
crossing; and
identifying pipe exposure when there is a deviation between the
estimated temperature of the fluid at the location downstream of the
pipeline crossing with an obtained fluid temperature at the location
downstream of the pipeline crossing.
18. The method claim 17 wherein the small difference is about 0.01
degrees Celsius.
19. A computer program comprising a computer readable memory storing
computer executable instructions thereon that when executed by a
computer perform the method steps of any one of claims 7 to 18.