Patent Grant
6853199
1. Field of the Invention
The present invention relates to a device and to a method for determining the position of the interfaces between different fluids contained in a drum, as well as the nature and the composition of the fluids. In particular, the present invention applies to a petroleum effluent contained in a separating drum for determining the position of the gas/oil and oil/water interfaces, and for characterizing the emulsion located between the oil and the water and the foam located between the oil and the gas.
2. Description of the Prior Art
In petroleum production, the effluent produced consists of several fluids: oil (mixture of hydrocarbons), salt water and gas, and often solid particles, sand for example. Separation of the different fluids is carried out in a separating drum according to the density of each fluid. In the drum, separation is physically carried out by means of a barrier allowing the lightest fluid (oil) to flow and the heaviest fluid (water) to be blocked. The position and above all the geometry (height of the barrier) determine the efficiency of the separating drum. This physical barrier is defined during the design of the separating drum and it cannot be modified during production. It is consequently important to be able to control the incoming volume of water and oil and the respective oil and water levels.
Mixtures of oil and water separate spontaneously by settling linked with the density difference. However, for most systems, formation of an intermediate layer of emulsified nature occurs. Formation of an emulsion is difficult to predict and to control. It depends on the operating conditions such as stirring, the presence of a pump, of valves, and on parameters such as the pressure, the temperature and the physico-chemical composition of the oil and of the water. It is important to locate this emulsion layer and to know its volume during the separation stage so as to adjust the production flow rate to minimize the loss of water in oil and, conversely, the loss of oil in water. Furthermore, knowing the nature of the emulsion allows introduction of suitable demulsifying chemical agents upstream from the drum, or to activate flow stabilization devices in the separating drum.
WO-00/22,387 provides a separating drum equipped with gamma-ray detectors allowing notably to determine the position of the oil/water and gas/oil interfaces, and the thickness of the emulsion.
However, because of their radioactive nature, gamma-ray detectors can be dangerous and are difficult and delicate to handle. Gamma ray detectors do not allow determination of the nature of the emulsion. Besides, the use of radioactive sources poses approval problems.
The present invention provides a separating drum equipped with microwave beam emitters and receivers.
In general terms, the invention relates to a device for determining the position, the composition and the nature of several superposed fluid layers, comprising:
According to the invention, the first rod and the second rod can be vertical and be spaced from 5 mm to 50 mm apart from one another. The distance between two successive emitters on the first rod can range between 10 mm and 30 mm, and the distance between two successive receivers on the second rod can range between 10 mm and 30 mm. The source can emit a microwave beam whose frequency ranges between 2 and 10 GHz. A receiver can be located at an intermediate height between the height of two adjacent emitters.
The invention also relates to a method using the device described above for determining the position, the composition and the nature of several superposed fluid layers, wherein the following stages are carried out:
According to an embodiment, stages a) to e) can be carried out with the source emitting a microwave beam of frequency f1, then stages a) to e) can be carried out with the source emitting a microwave beam of frequency f2, frequency f1 being different from frequency f2.
According to another embodiment, stages a) to a) can be carried out with the source emitting a microwave beam of frequency f1, then stages a) to e) can be carried out with the source emitting a microwave beam of frequency f2, then stages a) to e) can be carried out with the source emitting a microwave beam of frequency f3, then stages a) to e) can be carried out with the source emitting a microwave beam of frequency f4, frequencies f1, f2, f3 and f4 being all different.
According to the invention, in stage f), the processing means can record and analyze the intensity variation and the phase variation between the microwave beam emitted by the source and the microwave beam received by a receiver.
The device and the method according to the invention can be used to:
The use of microwave beams is less dangerous than gamma rays because the radiated energy is about one thousand times lower.
Furthermore, the microwave detectors permit the nature and the composition of the emulsion to be determined. The nature of the emulsion is known by determining the continuous liquid in which the drops of a second liquid are dispersed, for example: the presence of water drops dispersed in oil, or conversely the dispersion of oil drops in water. The composition gives the proportions of oil and water that constitute the emulsion.
Other features and advantages of the present invention will be clear from reading the description hereafter, with reference to the accompanying figures wherein:
Drum 1 is provided with a device for detecting the level of water 4, water/oil emulsion 5, oil 6 and oil foam 30 layers. The detection device can be arranged before barrier 8. The detection device has a first rod 12 provided with microwave beam emitters 13 and of a second rod 14 provided with microwave beam receivers 15. The layout of the rods, emitters and receivers is selected so as to limit reflection of the microwave beams on the walls of separating drum 1 and to limit measurement of such reflected microwave beams. Thus, receivers 15 measure the characteristics of the beams coming directly from emitters 13 without taking account of interferences such as the reflected beams. The rods can be metal bars, of square section for example. Rods 12 and 14 run through the interfaces that separate the various layers formed downstream from barrier 8. The rods can be rectilinear, parallel for example. The rectilinear rods can be inclined at 20°, preferably 10° to the vertical. The rods can also be vertical. Rod 12 is close to rod 14 and the distance between the two rods is known. For example, the distance between rods 12 and 14 measured on a horizontal line can range between 5 mm and 50 mm. Emitters 13 and receivers 15 are arranged in such a way that at least one of the emitters is located in a layer of a fluid and at least one of the receivers is located in a layer of another fluid. It is thus possible to know, by analyzing the information picked up by this emitter, that there is an interface between this emitter and this receiver. In addition, emitters 13 and receivers 15 can be arranged in such a way that at least one emitter and one receiver are located in the same layer. It is thus possible to determine, by analyzing the information picked up by this emitter, the composition and possibly the nature of this layer. The layout of emitters 13 and receivers 15 takes into account the possible position variation of the various layers. Emitters 13 can be arranged over the total height of drum 1, at regular intervals for example (thirty emitters 30 mm apart). Receivers 15 can also be arranged over the total height of drum 13 at regular intervals for example (thirty receivers 30 mm apart). A receiver 15 can be arranged at a height located between the heights of two emitters 13 which are adjacent on rod 12, for example in the middle of these two emitters. This layout increases the amount of information measured by the detection device, and therefore to increase the accuracy in relation to a layout where each receiver 15 is arranged at the same height as one of emitters 13. A receiver 15 can correspond to each emitter 13. Emitters 13 and receivers 15 can also be positioned in such a way that at least one emitter is arranged in each layer and/or a receiver is arranged in each layer and/or at least one emitter and one receiver are arranged in each layer.
A source 16 generates a microwave beam that is transmitted to emitters 13. The microwave beam can be a beam of electromagnetic energy or electromagnetic field of frequency ranging between 1 and 100 GHz, preferably between 2 and 10 GHz this beam generated by the source is characterized by an intensity value and a phase. Electronic control means 18 allow connection of source 16 to one or more emitters 13. The microwave beam is emitted by emitters 13 to radiate the petroleum effluent. After travelling the distance between the two rods, the beam is picked up by receivers 15. As it runs through one of the fluids that constitute the petroleum effluent, the intensity and the phase of the beam are modified. The beam received by receivers 15 is sent to data processing means 17. Electronic control means 19 allow connection of one or more receivers 15 to data processing means 17. The data processing means 17 records and compares the characteristics (intensity and phase) of the beam emitted by one of emitters 13 and the characteristics (intensity and phase) of the beam received by a receiver 15. It is thus possible to know, on the one hand, the attenuation of the microwave beam, that is the ratio of the intensity of the beam emitted by an emitter 13 to the intensity of the beam received by a receiver 15, and on the other hand the phase shift of the microwave beam, that is the difference between the phase of the beam emitted by an emitter 13 and the phase of the beam received by a receiver 15. Analysis of these comparisons allows determination of the nature and the composition of the fluid that separates the emitter from the receiver.
Emitter 13 shown in
Owing to the plane geometry of emitter 13, the microwave beams are emitted through side 22. The microwave beams radiate in the total volume surrounding emitter 13 with no preferred direction. There is no polarization of the microwave beam, due for example to a crossed position of two emitters. Polarization provides no pertinent information for data analysis. Thus, the emission of microwave beams according to the invention affords the advantage of being simple.
Receivers 15 are physically identical to emitters 13. Emitters 13 and receivers 15 are identical electromagnetic antennas and their roles can be reversed.
The measuring method can comprise the following stages:
Without departing from the scope of the invention, stages 1 to 7 can be carried out in a different order.
Exploitation of the attenuation and phase shift values measured by data processing means 17 in stage 4) allows determination of the position of the interfaces. In general: gas/oil or oil/water, and in particular detection of the intermediate layers between the gas and the oil, that is a foam layer, and between the oil and the water, that is the emulsion layer.
The attenuation of a wave, as well as its phase shift, depends on parameters intrinsic to the fluids crossed, such as the salinity of the water and the permittivity of the fluids (the permittivity of a fluid varying as a function of the frequency of the wave passing through the fluid). For example, at a frequency of 20 GHz, the permittivity is approximately 2 when the wave runs through the fluid containing oil. The permittivity increases when the wave runs through oil containing more and more water, until it reaches a value of the order of 80 when the wave runs through water only.
The nature of the fluid contained between an emitter 13 and a receiver 15 whose positions are known is determined from the transmission of a wave of known frequency f1 between the emitter and the receiver and from the attenuation and phase shift measurements. This analysis being repeated for each emitter 13 and receiver 15, it is possible to determine with precision the position of the interfaces between the various fluid layers present in the separating drum.
Selection of the frequency of the microwave beam emitted by the source can also be optimized. In fact, the permittivity being a function of the frequency of the wave running through the fluid, it is possible to carry out a series of measurements at a frequency for which the attenuation and the phase shift through the water are high in relation to the oil, then another series of measurements at a frequency for which the attenuation and the phase shift through the oil are high in relation to the gas.
The measurements performed by data processing means 17 also allows determination of the nature and the composition of the emulsion layer and the composition of the foam layer.
The permittivity value of the emulsion depends on the nature of the emulsion. The permittivity of the emulsion can therefore be calculated to know the nature of the emulsion, from measurements of the attenuation and of the phase shift of a wave of frequency f1 running through an emulsion layer.
From a multifrequency calibration, the oil and water composition of the emulsion and the gas composition of the foam are determined by means of a specific processing of all of the data resulting from the attenuation and phase shift measurements. This specific processing is based on a “signal processing” type data exploitation and on a statistical analysis.
The present invention allows determination of the level of the various fluids present in a separating drum used for production of a petroleum effluent. This information allows controlling the effluent inflow rate so as to maintain the interface between the emulsion and the oil below the barrier of the separating drum. The loss of oil in water or the loss of water in oil can thus be minimized.
The device according to the present invention can also be installed at the outlet of a separating drum in the vicinity of the oil discharge line. In
The present invention also allows knowing the nature and the composition of the emulsified oil/water layer separating the oil layer from the water layer and of the oil form/gas layer separating the oil layer from the gas layer. This information allows optimizing the operating conditions of the separating drum (stirring, presence of a pump, valves, and parameters such as the pressure, the temperature and the physico-chemical composition of the oil and of the water), to control the introduction of stabilizing and demulsifying chemical agents in the petroleum effluent downstream from the separating drum and/or to actuate flow stabilization devices in the separating drum.
| Number | Date | Country | Kind |
|---|---|---|---|
| 01 16096 | Dec 2001 | FR | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4947127 | Helms et al. | Aug 1990 | A |
| 5101163 | Agar | Mar 1992 | A |
| 5150061 | Castel et al. | Sep 1992 | A |
| 5793216 | Constant | Aug 1998 | A |
| 6332087 | Svenson et al. | Dec 2001 | B1 |
| 6480141 | Toth et al. | Nov 2002 | B1 |
| Number | Date | Country | |
|---|---|---|---|
| 20030117150 A1 | Jun 2003 | US |
