The present invention is a watercut means and method in general,
and more particular, a microwave watercut means and method.
A petroleum stream microwave watercut monitor of the present invention
includes a test cell having a petroleum flowing through it. A source, connected
to a first antenna located within the test cell, provides microwave energy to
the first antenna so as to irradiate the petroleum stream in the test cell with
microwave energy. A second antenna located in the test cell and connected to a
detector outside of the test cell receives the microwave energy that has passed
through the petroleum stream and provides it to the detector. The detector provides
an intensity signal corresponding to the received microwave energy. An indicator
provides an indication of the watercut of the petroleum stream in accordance with
the intensity and the phases difference between the microwave energy provided by
the source and the received microwave energy. The test cell means also includes
means for reducing an amount of debris in a portion of the petroleum stream flowing
between both antenna.
The objects and advantages of the invention will appear more fully
hereinafter, from a consideration of the detailed description which follows, taken
together with the accompanying drawings wherein one embodiment is illustrated
by way of example. It is to be expressly understood, however, that the drawings
are for illustrative purposes only and are not to be construed as defining the
limits of the invention.
Figure 1 is a simplified block diagram of a microwave watercut monitor
constructed in accordance with the present invention.
Figure 2 is a representation of the test cell shown in Figure 1.
Figure 3 is a detailed representation of the test cell shown in Figure
Figure 4 is a cross sectional view along the lines 4- 4 of the test
cage shown in Figure 3
The watercut monitor shown in Figure 1 includes a microwave transmitter
3 providing electromagnetic energy, hereinafter referred to as microwave energy,
at a microwave frequency. Transmitter 3 is low powered and may use a microwave
gun source. Transmitter 3 provides microwave energy to directional coupler 7. Directional
coupler 7 provides microwave energy to a conventional type voltage controlled
phase shifter 9 and to a circulator 8. All conductance or carrying of microwave
energy is accomplished by using conventional type waveguides.
Circulator 8 provides microwave energy via a waveguide 10, to a petroleum
stream passing through a test cell 17. Test cell 17 will be described in greater
detail hereinafter. The microwave energy that passes through the petroleum stream
is provided by way of a waveguide 19 to a switch means 24 which when in one state
provides received microwave energy as test microwave energy to a directional coupler
28. Directional coupler 28 provides the test microwave energy to a detector 32
and to a mixer 34. Detector 32 provides a signal E2 corresponding to the intensity
of the test microwave energy.
The petroleum stream may also reflect some of the microwave energy
back which passes back to circulator 8 by way of waveguide 10. Circulator 8 blocks
the reflected microwave energy from feeding back to transmitter 3 and provides
the reflected microwave energy which becomes more important as the distance across
test cell 17 increases. This is especially true where test cell 17 is used with
a large pipeline carrying the petroleum stream.
A positive direct current voltage +V is provided to switch means
24. With switch means 24 in another state, switch means 24 provides the reflected
microwave energy from circulator 8 as the test microwave energy.
The microwave energy from voltage control phase shifter 9, hereinafter
called the reference microwave energy, and the test microwave energy from directional
coupler 28, are provided to mixer 34 which mixes them to provide two electrical
signals E3, E4, representative of the phases of the reference microwave energy
and the test microwave energy, respectively.
A differential amplifier 36 provides an output signal EO in accordance
with the difference between the signals E3, E4 and hence the phase difference between
the test microwave energy and the reference microwave energy. Signal EO, and hence
the signal C, decreases in amplitude until there is substantially 90° phase difference
between the reference microwave energy and the test microwave energy. Voltage
control phase shifter 9 indicates the amount of phase shift required to eliminate
the phase difference and provides an "enable" signal to computer means 50.
Signals E2 and C are provided to computer means 50 which contains
within its memory means data related to phase and amplitude for various percentages
of watercuts that could be encountered in the production stream. The "enable"
signal, provided by phase shifter 9 to computer means 50, allows computer means
50 to utilize signals C and E1 to select the proper watercut value. Computer means
50 provides signals, corresponding to the selected watercut value, to readout
means 54 which may be either digital display means or recording means or a combination
With reference to Figures 2, 3, and 4, waveguide 10 enters test call
17 and a test cage 70 and is connected to an antenna 74. A seal 76 prevents any
of the petroleum stream in test cell 17 from leaking out. Similarly waveguide
19 enters test cell 17 and test cage 70 is connected to an antenna 80. A seal 84
prevents the petroleum stream from leaking from test cell 17.
As shown in Figures 1 and 2, microwave energy from circulator 8 will
pass through line 10 and is radiated by antenna 74 to antenna 80. Antenna 80 receives
microwave energy and provides the received microwave through waveguide 19. Cage
70 is a self cleaning device that allows a fluid mixture to flow between antennas
74 and 80 while removing particles and debris that might be in the petroleum stream.
Test cage 70 has two end pieces 87 and 90 designed to support a coarse
wire mesh 93 as an outside screen and a fine wire mesh 98 as an inner screen. The
passage of waveguides 10 and 19 through end plates 87 and 90, respectively, is
supported by a ball bearing system 102. Test cage 70 will rotate around waveguides
10 and 19 in response to the flow of the petroleum stream.
In operation, as debris in the petroleum stream comes in contact
with cage 70, the larger elements of the debris makes contact with the coarse wire
mesh 93 and fall to the bottom of the test cell 17 and is carried away by the
flow of the petroleum stream. Smaller elements of the debris may enter cage 70
but they will come in contact with fine wire mesh 98 and be stopped from entering
that portion of test cage 70 that lies between antennas 74 and 80. The debris
stop by fine wire mesh 98 may be carried by fine wire mesh 98 and fall away under
the influences of gravity and due to the rotation of cage 70. The fallen smaller
elements will pass out of cage 70 due to the flow of the petroleum stream so that
there is not a build up of debris in the vicinity of the microwave energy path
between antennas 74 and 80.
The present invention as hereinbefore described is a microwave watercut
monitor with apparatus for reducing the amount of debris in a petroleum stream
passing between microwave antennas so as to enhance the accuracy of the watercut