Petroleum stream microwave watercut monitor

Abstract: A microwave watercut monitor includes a test cell having a petroleum stream flowing through it while permitting the microwave energy to enter the test cell. A microwave source provides microwave energy to a circulator which in turn provides the microwave energy to an antenna. The antenna provides the petroleum stream in the test cell with the microwave energy and receives reflected microwave energy back from the stream. The reflected microwave energy is provided by the antenna to the circulator which in turn provides the reflected microwave energy as test microwave energy. Indicator apparatus provides an indication of the watercut of the petroleum stream in accordance with the phase difference between the source provided microwave energy and the test microwave energy. In one embodiment a detector assembly is connected to the circulator and detects the intensity of the test microwave energy to provide a corresponding intensity signal. The indicator apparatus is connected to the circulator to the microwave source and to the detector assembly to provide an indication of the watercut in accordance with the intensity signal and the phase difference between the source provided microwave energy and the test microwave energy.

Description: The present invention relates to petroleum stream monitors in general and, more particularly, to petroleum stream water cut monitors. US-A-4499418 describes a petroleum stream microwave water cut monitor comprising: a test cell for having a petroleum stream flow through it while permitting microwave energy to enter the test cell; a source for providing microwave energy; an antenna for irradiating the stream flowing through the test cell with microwave energy and for receiving reflected microwave energy back from the stream in the test cell; a circulator connected to the source and to the antenna for providing the microwave energy from the source to the antenna and for providing reflected microwave energy from the antenna as test microwave energy; and phase indicator means connected to the source and to the circulator for providing a phase difference signal representative of the phase difference between the microwave energy provided by the source and the test microwave energy. The present invention is characterized by: a detector connected to the circulator for detecting the intensity of the test microwave energy and providing an intensity signal representative thereof; and an indicator connected to the detector and the phase means for providing an indication of the water cut of the petroleum stream in accordance with said intensity signal and said phase difference signal. Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which:- Figure 1 is a combination simplified block diagram and a schematic of a watercut monitor. Figure 2 is a side elevation of an isolator of the apparatus of Figure 1; Figure 3A is a side elevation of one of the wave guides forming the isolator of Figure 2; Figure 3B is a front elevation of the wave guide of Figure 3A; and Figure 4 is a partial simplified block diagram of a microwave water cut monitor according to the present invention. The water cut monitor shown in Figure 1 includes a microwave source 3 providing electromagnetic energy, hereinafter referred to as microwave energy, at a microwave frequency. Source 3 is low powered and may use a microwave Gunn source. Source 3 provides microwave energy to directional coupler 4. Directional coupler 4 provides microwave energy to a conventional type voltage controlled phase shifter 5 and to a circulator 8. All conductance or carrying of microwave energy is accomplished by using conventional type waveguides and coaxial cable. Circulator 8 provides microwave energy to an antenna 9 which has, in this embodiment, an isolator 12 interconnecting antenna 9 to circulator 8. Antenna 9 transmits or radiates the microwave energy through a sample stream of a fluid mixture passing through a test cell 10. Test cell 10 may be a portion of a pipeline with "windows" made of material which permits passage of the microwave energy or it may be a portion of the pipeline made of the "window" material. The transmitted microwave energy passes through the fluid mixture and is received by an antenna 14 which provides the received microwave energy to a switch means 20. The fluid mixture also reflects some of the microwave energy back to antenna 9 which passes back through antenna 9 to circulator 8. Circulator 8 blocks the reflected microwave energy from feeding back to source 3 and provides the reflected microwave energy to switch means 20. Reflected microwave energy becomes more important as the distance between antennas 9 and 14 increases. This is especially true where a large pipeline carrying the fluid mixture is being monitored. A positive direct current voltage +V is provided to a switch means 24 which is connected to switch means 20. With switch means 24 open, switch means 20 provides microwave energy from antenna 14 as test microwave energy. When switch 24 is closed, the reflected microwave energy from circulator 8 is provided by switch means 20 as the test microwave energy. The microwave energy from voltage control phase shifter 5, hereinafter called the reference microwave energy, and the test microwave energy from switch 20, are provided to a mixer 28 which mixes them to provide two electrical signals E1, E2, representative of the phases of the reference microwave energy and the test microwave energy. A differential amplifier 30 provides an output signal E0 in accordance with the difference between signals E1 and E2. Signal E0 is a function of the phase difference between the reference microwave energy and the test microwave energy. Signal E0 may be applied to an indicator in which the amplitude of E0 will be representative of the phase difference or as shown in the present example may be provided to a feedback network 34. Feedback network 34 provides a control voltage C to voltage control phase shifter 5 controlling the phase of the reference microwave energy. Signal E0, and hence the control voltage 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. With reference to Figure 2, there is shown isolator 12. Isolator 12 is used to protect an area adjacent test cell 10 from potential explosions. This unsafe area, which may be of any size, is shown in Figure 1 by dashed line 40. The possibility of an explosion arises since many of the energy controlling components of the watercut monitor are made of metal for optimal microwave transmission. As such, all energy generated in the watercut circuits could be conducted to antennas 9 and 14. Under normal operating conditions, energy is limited to safe levels not capable of causing an explosion. In the event of accident or misuse of the watercut monitor much higher energy and energy of non-microwave frequencies could be applied to antennas 9 and 14. Isolators 12 and 18 isolate antennas 9 and 14 from the buildup voltages that may occur on any of the other elements and thus protect them from arcing and causing an explosion. Isolator 12 is made up of two identical wave guides 44 which is shown in Figures 3A and 3B. Wave guides 44 include mounting flanges 48, a guide element 52, insulators 57 and a metal jack 60. Metal jack 60 is isolated from the wave guide 52 so that any voltage buildup on jack 60 does not appear on guide element 52. As can be seen in Figure 3B, the RF energy aperture is identified by the numeral 65. It should be noted that although isolator 12 is shown with both jacks 60 facing downward it is obvious to one skilled in the art that one of the wave guides 44 may be reorientated 180° without loss of cross-sectional area of aperture 65, if it is so desired to do so. The present embodiment has been described as being used with a water cut monitor of the type described and disclosed in U.S.P. 4,499,418, but it may also be used in either situation where a water cut monitor uses microwave energy singularly either as a direct passthrough type of measurement or in another configuration as a reflected microwave energy configuration. The embodiment of the invention shown in Figure 4 is a modification of the apparatus shown in Figure 1. The same parts have been given the same reference numerals in Figures 1 and 4. The description of this embodiment will be restricted to the modified portions of the apparatus of the Figure 4 embodiment. In the Figure 4 embodiment the switch means 20 provides test microwave energy to a directional coupler 19. Directional coupler 19 provides the test microwave energy to a detector 22 as well as to mixer 28. Detector 22 provides a signal E3 corresponding to the intensity of the microwave energy received by antenna 14. Feedback network 34 provides signal C to voltage control phase shifter 5, controlling the phase of the reference microwave energy, and also to a mini-computer means 40. Signals E3 and C are provided to mini-computer means 40 which contains within it memory means having data related to phase and amplitude for various percentages of water cuts that could be encountered in the production stream. Phase Shifter 5 also provides an enabling signal to computer means 40 allowing computer means 40 to utilize signals C and E3 to select the proper water cut value computer means 40 provides signals, corresponding to the selected water cut value, to readout means 41 which may be either digital display means or record means or a combination of the two.

Claims: A petroleum stream microwave water cut monitor comprising: a test cell (10) for having a petroleum stream flow through it while permitting microwave energy to enter the test cell; a source (3) for providing microwave energy; an antenna (9) for irradiating the stream flowing through the test cell with microwave energy and for receiving reflected microwave energy back from the stream in the test cell; a circulator (8) connected to the source and to the antenna for providing the microwave energy from the source to the antenna and for providing reflected microwave energy from the antenna as test microwave energy; and phase indicator means (5,28,30,34) connected to the source and to the circulator for providing a phase difference signal (C) representative of the phase difference between the microwave energy provided by the source and the test microwave energy; characterized by: a detector (22) connected to the circulator for detecting the intensity of the test microwave energy and providing an intensity signal (E3) representative thereof; and an indicator (40,41) connected to the detector and the phase means for providing an indication of the water cut of the petroleum stream in accordance with said intensity signal (E3) and said phase difference signal (C). A monitor according to claim 1 characterized in that the phase means (5,28,30,34) comprises: a voltage controlled phase shifter (5) connected to the source (3) to receive microwave energy provided by said source, to shift the phase of the provided microwave energy in accordance with a phase shift signal to provide reference microwave energy, and to provide an enabling signal when the phase shifting is completed; and phase shift signal means (28,30,34) connected to receive said reference microwave energy and said test microwave energy for providing said phase shift signal to the phase shifter (5) until there is substantially a 90° phase difference between the reference microwave energy and the test microwave energy at which time the phase shifting is completed and said enabling signal is provided to said indicator (40,41) to enable said indicator to provide said indication. A monitor according to claim 2 characterized in that the phase shift signal means (28,30,34) includes: a mixer (28) connected to the phase shifter (5) and to the circulator (8) for mixing the reference microwave energy from the phase shifter with the test microwave energy from the circulator to provide two signals (E1,E2) representative respectively of the phases of the reference microwave energy and the test microwave energy; a differential amplifier (30) connected to the mixer for providing an output signal (EO) in accordance with the difference between the two signals from the mixer; and a feedback network (34) connected to the phase shifter and to the differential amplifier to provide said phase shift signal in accordance with the output signal. A monitor according to any one of claims 1 to 3 characterized by an isolator (12) connected between the circulator (8) and the antenna (9) for passing microwave energy to and from the antenna while isolating the antenna from extraneous energies that may arise in the water cut monitor so as to prevent an accidental explosion due to those extraneous energies. A monitor according to any one of claims 1 to 3 characterized by: a second antenna (14) for receiving microwave energy that has passed through the stream flowing in the test cell to provide received microwave energy; and a switch (20) operable to provide said received microwave energy as said test microwave energy in place of the microwave energy from the circulator. A monitor according to claim 5 characterized by: a first isolator (12) connected between the circulator (8) and the first-mentioned antenna (9) for passing microwave energy to and from the first-mentioned antenna while isolating the first-mentioned antenna from extraneous energies that may arise in the water cut monitor so as to prevent an accidental explosion due to those extraneous energies; and a second isolator (18) connected between the second antenna (14) and the switch (20) for passing received microwave energy from the second antenna to the switch while isolating the second antenna from extraneous energies that may arise in the water cut monitor so as to prevent an accidental explosion due to those extraneous energies.

Inventors: DURRETT MICHAEL GREGORY, HATTON GREGORY JOHN, HELMS DAVID ALBERT, MARRELLI JOHN DAVID, DURRETT, MICHAEL GREGORY, HATTON, GREGORY JOHN, HELMS, DAVID ALBERT, MARRELLI, JOHN DAVID
Applicants: TEXACO DEVELOPMENT CORP, TEXACO DEVELOPMENT CORPORATION
Application year: 1989
Main classification: G01N22
IPC codes: G01N22, G01N33