Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
[0001] Foam level sensor
FIELD
[0002] This relates to a foam level sensor for a production tank.
BACKGROUND
[0003] As downhole fluids are pumped into a production tank, the fluid may
separate into
different layers, such as sand, water, emulsion, oil, foam, and gas. The
composition of the
produced fluids will vary depending on the particular producing well.
SUMMARY
[0004] There is provided a foam level sensor for a production tank containing
foam,
comprising a sensor element that is supported by the surface tension of the
foam, and a sensor
switch that is triggered upon the sensor element being raised to a
predetermined height.
[0005] According to another aspect, the sensor element may have a specific
gravity of
less than 0.45.
[0006] According to another aspect, the sensor element may be mounted on a
sensor line,
and the sensor element may be supported on the sensor line by a stopper until
the foam level
reaches the height of the stopper.
[0007] According to another aspect, the sensor element may mounted to an arm.
[0008] According to another aspect, the sensor element may comprise a flat
bottom
surface.
[0009] According to another aspect, there is provided a production tank
containing fluid
having a layer of foam in combination with a foam level sensor as described
above.
[0010] According to another aspect, there is provided a method of operating a
wellhead,
comprising the steps of providing the combination described above; raising the
level of foam
in the production tank by pumping production fluids into the production tank
such that the
sensor element is raised; and triggering the sensor switch to trigger an
event.
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[0011] According to another aspect, the triggered event is one of a defoaming
action and
an alarm.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] These and other features will become more apparent from the following
description in which reference is made to the appended drawings, the drawings
are for the
purpose of illustration only and are not intended to be in any way limiting,
wherein:
FIG. 1 is a side elevation view in section of a foam level sensor installed in
a
production tank.
FIG. 2 is a side elevation view in section of an alternative foam level sensor
in
stalled in a production tank.
DETAILED DESCRIPTION
[0013] A foam level sensor generally identified by reference numeral 10, will
now be
described with reference to FIG. 1 and 2.
[0014] Referring to FIG. 1, there is provided a production tank 12 that has
layers of sand
14, water 16, oil 18 and foam 20. As production fluid is pumped into
production tank 12
through inlet 22, it will separate into the various layers, based on their
specific gravity, with
foam on the top.
[0015] In order to efficiently empty the production tank of the various layers
of material,
it is necessary to know the levels. One type of sensor arrangement that
measures the level of
water 16 and oil 18 in tank 12 is depicted in FIG. 1 and 2, although it will
be understood that
other arrangements may be used. As depicted, a sensor line 24 has floats 26
and 28 that move
along sensor line 24. Float 26 is designed to float on water but sink in oil,
while float 28 is
designed to float in oil. Sensor line 24 may determine the position of floats
26 and 28 by reed
switches, or by other means.
[0016] Sensor line 24 is preferred, as it can be adapted to include foam level
sensor 10,
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such that the same system can be used to measure each levels in tank 12.
Sensor 10 includes
a sensor element 30 that is designed to be supported by the surface tension of
the foam. This
includes a proper design of the bottom surface that minimizes breaking the
foam, and is also
sufficiently light. For example, sensor element 30 may have a smooth, flat
bottom surface
and be made from a plastic foam that has a specific gravity of 0.45 or less.
Other materials
known in the art may also be used. Sensor element 30 is connected to a sensor
switch 32 that
is triggered upon sensor element 30 being raised to a predetermined height. In
the depicted
embodiment, sensor switch 32 is contained within sensor line 24. Sensor switch
32 then
triggers an event, such as by sending a signal to a controller 33. The event
may be an alarm
that is triggered, such as an audio or visual alarm on site, or a signal that
is transmitted to a
remote location using, for example, a SCADA system. Alternatively, sensor
switch 32 may
generate a signal that activates or deactivates equipment, for example, the
well pump may be
shut down, or a defoaming device, such as a sprayer that sprays a defoaming
agent in tank 12,
may be activated.
[0017] Sensor element 30 may be suspended at a specific height, such as by a
stopper 34,
such that it is not carried upward by foam layer 20 until it gets close to the
predetermined
height. Thus, instead of acting as a continuous level sensor in the sense of
floats 26 and 28,
sensor 10 acts more like a discrete level sensor, where the output relates
only to whether that
level has been reached or not. It will be understood that sensor element 30
may be designed
to be carried continuously by foam layer 20, however to reduce the possibility
of the surface
tension breaking, which would prevent sensor element 30 from indicating when
the level has
been reached, it is preferred that sensor element 30 be suspended as depicted.
Sensor element
may also act as a high level sensor that is triggered once the fluid level
reaches that height,
25 even if no foam is present in the tank.
[0018] It will be understood that there are different ways in which sensor 10
may be
deployed. As described above, sensor element 30 is mounted on a sensor line 24
with floats
24 and 26. However, sensor element 30 may be deployed on a separate line 24,
or may not be
30 deployed on a line. Referring to FIG. 2, an alternative embodiment is
shown, where sensor
element 30 is mounted to the end of an arm 36.
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[0019] In this patent document, the word "comprising" is used in its non-
limiting sense to
mean that items following the word are included, but items not specifically
mentioned are not
excluded. A reference to an element by the indefinite article "a" does not
exclude the
possibility that more than one of the element is present, unless the context
clearly requires that
there be one and only one of the elements.
[0020] The following claims are to be understood to include what is
specifically
illustrated and described above, what is conceptually equivalent, and what can
be obviously
substituted. Those skilled in the art will appreciate that various adaptations
and modifications
of the described embodiments can be configured without departing from the
scope of the
claims. The illustrated embodiments have been set forth only as examples and
should not be
taken as limiting the invention. It is to be understood that, within the scope
of the following
claims, the invention may be practiced other than as specifically illustrated
and described.
