Microwave water cut monitors

Abstract: A test cell (53) receives a reference petroleum multiphase fluid sample and allows a sample stream of a petroleum stream to pass through it. A source (3) supplies microwave energy to one of a first pair of antennae (63,65) which irradiates the petroleum stream or the reference sample in the test cell with microwave energy. One of a second pair of antennae (67,70) receives the microwave energy that has passed through either the petroleum stream or the reference sample. A detector (22) detects the received microwave energy and provides a signal (E1) representative thereof. An indicator (5,34,40,44) provides an indication of the water cut of the petroleum stream in accordance with the received signal power (E1) and a phase difference (E0) between the transmitted microwave energy and the received microwave energy.

Description: The present invention relates to apparatus for obtaining a measure of the percentage of water in a stream of petroleum, referred to herein for brevity as microwave water cut monitors. US-A-4499418 describes a petroleum stream microwave water cut monitor comprising: a test cell arranged to allow a sample stream of a petroleum stream to flow through it; a source for supplying microwave energy; first antenna means connected to the source to transmit microwave energy into the sample stream; second antenna means for receiving microwave energy that has passed through the sample stream and for providing the received microwave energy as test microwave energy; phase difference means arranged to provide a signal representative of the phase difference between the transmitted microwave energy and the received microwave energy; and computer means arranged to provide an indication of the water cut of the petroleum stream in accordance with the phase difference signal. The present invention is characterized in that: said test cell is also arranged to receive a reference petroleum multiphase fluid sample; said first antenna means is arranged to transmit said microwave energy into a selected one of said sample stream and to the reference sample; said second antenna means is arranged to receive microwave energy that has passed through said sample stream or the reference sample; a detector is connected to the second antenna means to detect the power of the test microwave energy and to provide a power signal representative thereof; and said computer means is connected to said second antenna means to the source and to the detector to provide said indication of the water cut of the petroleum stream in accordance with the phase difference signal and the power signal from the sample stream as referred to base line phase difference and power signals from the reference sample. An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:- Figure 1 is a partial simplified block diagram and a partial schematic of a microwave water cut monitor constructed in accordance with the present invention. Figure 2 is a simplified block diagram of the test apparatus shown in Figure 1. Figure 3 shows the test cell from Figure 2. Figures 4 and 5 are sections on lines 4-4 and 5-5 of the test cell shown in Figure 3. The water cut 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 a directional coupler 4. Directional coupler 4 provides microwave energy to a voltage controlled phase shifter 5 and to test apparatus 8. All conductance or carrying of microwave energy is accomplished by using waveguides and coaxial cables. Test apparatus 8 has a line 10, carrying a sample stream of a multi-phase petroleum stream, entering apparatus 8. The sample stream leaves test apparatus 8 by way of a line 11. Apparatus 8 will be described in more detail hereinafter. Suffice to say at this point that microwave energy leaving test apparatus 8 hereinafter referred to as test microwave energy, is microwave energy that has been passed either through the sample stream or through a reference sample. The test microwave energy is applied to a directional coupler 18. Directional coupler 18 provides the test microwave energy to a detector 22 and to a mixer 28. Detector 22 provides a signal E1 corresponding to the power, i.e. intensity of the test microwave energy from the test apparatus 8. Voltage control phase shifter 5 provides microwave energy, hereinafter called the reference microwave energy, to mixer 28 which mixes the reference microwave energy and the test microwave energy to provide two electrical signals E2, E3, representative of the phases of the reference microwave energy and the test microwave energy, respectively. A differential amplifier 30 provides an output signal E0 in accordance with the difference between signals E2 and E3. Signal E0 is a function of the phase difference between the reference microwave energy and the test microwave energy and is provided to a feedback network 34. Feedback network 34 provides a signal C to voltage control phase shifter 5, controlling the phase of the reference microwave energy, and to a mini-computer means 40. Signal E0, and hence 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 5 indicates the amount of phase shift required to eliminate the phase difference. Signals E1, C and T (the temperature of the test cell as described below) are provided to a mini-computer means 40 which contains within it memory means having data related to phase and power for various percentages of water cuts that could be encountered in the production stream. Phase Shifter 5 also provides an enable signal to computer means 40 allowing computer means 40 to utilize signals T, C and E1 to select the proper water cut value. Computer means 40 provides signals, corresponding to the selected water cut value, to readout means 44 which may be either display means or record means or a combination of the two. With reference to Figures 1 and 2, test apparatus 8 includes a test cell 53. Test cell 53 will be described more fully hereinafter. Microwave energy from directional coupler 4 enters switch means 58 which provides microwave to test cell 53 through either a line 62 or a line 64. Line 62 provides the microwave to an antenna 63 which radiates the microwave energy into the sample stream. Similarly, when microwave energy is provided by line 64, it is provided to an antenna 65. Antenna 65 radiates the microwave energy into the reference sample. Line 66 carries test microwave energy received by an antenna 67 after it has passed through the sample stream. Similarly, line 69 carries microwave energy received by an antenna 70 after it has passed through the reference sample. Switch means 72 receives the test microwave energy from either line 66 or line 69 and provides it to directional coupler 18. A reference sample source 77 provides the reference sample fluid to test cell 53 by way of a line 80 having a valve 84. A channel in test cell 53 connects line 80 to another line 88 having a valve 90. In operation, source 77 provides the reference fluid through test cell 53. A measurement could be made while it is flowing, or sample fluid could be contained in a static condition in test cell 53 by closing valve 90 until the channel within test cell 53 is completely filled. To drain the reference sample fluid from test cell 53 valve, 84 is closed while valve 90 is opened. With reference to Figure 3, there is shown test cell 53 having microwave entrance ports 95 and 98. On the other side of test cell 53 as represented by dash lines are microwave exit ports 105 and 108. Connecting microwave entrance port 95 and microwave exit port 105 is a microwave channel 110. Similarly a microwave channel 112 connects microwave entrance port 98 with microwave exit port 108. Also shown in Figure 3 are fluid channels 116 and 120. Since fluid channels 116 and 120 are in line in this view of test cell 53 only one set of dash lines represents them. This can be seen better in Figure 4 which has a cut away view of test cell 53 in the direction of the arrows 4-4. There is shown a body 125 which may be made of metal having fluid channels 116 and 120 passing through it longitudinally and microwave channels 110 and 112 for the microwave energy cut transversely through it. It should be noted that channels 110 and 112 are shown as being offset from each other. However this offset is not necessary to the practice of the present invention. It should also be noted that fluid channels 116, 120 have a rectangular cross-section so that the microwave energy that passes through the fluids, always has the same distance of passage. Referring to Figure 5, there is a view of test cell 53 along the line in the direction of 5-5, shown in Figure 3. Channel 110 is filled with a solid material 130, such as high density polytetrafluoroethylene, that is conductive to microwave energy, except for that portion of channel 110 that forms a cross-section of fluid channel 116. Cut into body 125 is microwave entrance port 95. Further there is another chamber 134 which connects microwave entrance port 95 and enters into material 130 in channel 110. This is for the insertion of microwave antenna 63, which may be of the commercial type made by Omni Spectra, Part No. 2057-5134-02, slightly modified for the present application. Similarly, microwave exit port 105, for antenna 67, is shown with an additional chamber 135 which enters into material 130. Again this is for the purpose of monitoring the sample stream. Basically it is the same type of antenna as is entered with entrance port 95, but again modified for the present application. The microwave energy when applied to the antenna 63 enters material 130 and is directed to cross channel 116 until it reaches the antenna 67 inserted in exit port 105. Referring also to Figure 2, lines 10 and 11 are connected in the conventional manner to channel 116 so that the sample stream in line 10 will flow through test cell 53 to line 11. Similarly, lines 80 and 88 are connected to fluid channel 120 in such a manner that the sample fluid in line 80 will enter fluid channel 120 and exit test cell 53 through line 88. Similarly antenna 65 in entrance port 98 is connected to line 64 and antenna 70 in exit port 108 is connected to line 69. As can be seen in Figure 3, temperature sensor 140 which is a thermocouple, is inserted into a chamber cut into block 125 and thus reads the temperature of block 125 as the temperature of the reference or of the production stream sample. Basically, the reference sample's power and phase shift is used as base line data in mini-computer means 40. The base line data and the test data derived from the petroleum sample stream are temperature corrected by mini-computer means 40. Mini-computer means 40 determines the water-cut in accordance with the corrected base line data, the corrected test data and look-up table stored in its memory.

Claims: A petroleum stream microwave water cut monitor comprising: a test cell (53) arranged to allow a sample stream of a petroleum stream to flow through it; a source (3) for supplying microwave energy; first antenna means (63) connected to the source (3) to transmit microwave energy into the sample stream; second antenna means (67) for receiving microwave energy that has passed through the sample stream and for providing the received microwave energy as test microwave energy; phase difference means (30) arranged to provide a signal (E0) representative of the phase difference between the transmitted microwave energy and the received microwave energy; and computer means (5,34,40,44) arranged to provide an indication of the water cut of the petroleum stream in accordance with the phase difference signal (E0); characterized in that: said test cell (53) is also arranged to receive a reference petroleum multiphase fluid sample; said first antenna means (63,65) is arranged to transmit said microwave energy into a selected one of said sample stream and to the reference sample; said second antenna means (67,70) is arranged to receive microwave energy that has passed through said sample stream or the reference sample; a detector (22) is connected to the second antenna means (67,70) to detect the power of the test microwave energy and to provide a power signal (E1) representative thereof; and said computer means (5,34,40,44) is connected to said second antenna means (67,70), to the source (3) and to the detector (22) to provide said indication of the water cut of the petroleum stream in accordance with the phase difference signal (E0) and the power signal (E1) from the sample stream as referred to base line phase difference and power signals (E0,E1) from the reference sample. A monitor according to claim 1 characterized by: means (140) for sensing the temperature of the reference sample and of the sample stream and providing respective temperature signals (T) representative thereof; and wherein said computer means (5,34,40,44) is arranged to provide the indication of the water cut also in accordance with said temperature signals (T). A monitor according to claim 1 or claim 2 characterized in that the test cell (53) includes: a body (125) having two channels (116,120) therein for fluid passage and two channels (110,112) for microwave energy passage; a fluid source (77) for providing the reference sample to one of the fluid channels (120); means (10) for receiving the sample stream and providing it to the other fluid channel (116); means (11) for allowing the sample stream to exit from the body; and wherein one fluid channel (116) and one microwave channel (110) intersect each other at right angles, and the other fluid channel (120) and the other microwave channel (112) intersect each other at right angles. A monitor according to claim 3 characterized in that each microwave channel (110,112) contains a material (130), except for that portion of the microwave channel that crosses a fluid channel, that is impervious to fluids but permits passage of the microwave energy. A monitor according to claim 4 characterized in that the solid material in the microwave channel is polytetrafluoroethylene. A monitor according to any one of claims 1 to 5 characterized in that the first antenna means (63,65) includes: a first transmitter antenna (63) spatially arranged with one of the microwave channels (110) for transmitting microwave energy into the one microwave channel; a second transmitter antenna (65) spatially arranged with the other microwave channel (112) for transmitting microwave energy into the other microwave channel; and first switch means (58) connected to the source (3) and to the first and second transmitter antennas (63,65) for providing the microwave energy supplied by the source to either the first transmitter antenna or to the second transmitter antenna; and the second antenna means (67,70) includes: a first receiving antenna (67) spatially arranged with the one microwave channel (110); a second receiving antenna (70) spatially arranged with the other microwave channel (112); and second switch means (72) connected to the first and second receiving antennas (67,70) and cooperating with the first switch means (58) for passing microwave energy that has passed through a fluid and has been received by a receiving antenna to the detector (22) and to the computer means (5,34,40,44).

Inventors: DOWTY EARL LEONARD, DURRETT MICHAEL GREGORY, HATTON GREGORY JOHN, HELMS DAVID ALBERT, MARRELLI JOHN DAVID, DOWTY, EARL LEONARD, DURRETT, MICHAEL GREGORY, HATTON, GREGORY JOHN, HELMS, DAVID ALBERT, MARRELLI, JOHN DAVID
Applicants: TEXACO DEVELOPMENT CORP, TEXACO DEVELOPMENT CORPORATION
Application year: 1990
Main classification: G01N22
IPC codes: G01N22