RU2037787C1 - Method of determination of level of lower boundary of emulsion layer of stratal water in oil in dehydrator - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: signals at three different depths are picked off by identical converters. Level is found by comparison of root-mean-square values of frequencies produced at different depths. EFFECT: enhanced authenticity of level determination. 2 dwg

Description

 The invention relates to the preparation of oil and is intended for use in the dehydration process.

 The closest set of features to the claimed method is a method for determining the interface between two liquids with different electrical properties (electrical impedances) [1] The method consists in immersing two identical probes (measuring transducers) in the test medium so that these probes are at different depths obtaining the difference of the signals coming from the probes and carrying measurement information from the local areas of the medium under study. If both probes are in contact with the same liquid, then the difference signal will be zero, if with different liquids having different electrical properties (electrical impedances), then the difference signal will not be zero.

 The prototype method, like an analogue, can only be implemented provided that the measured physical quantity in each of the fluids forming the interface is constant in its entire volume.

 The inventive method allows to obtain a higher technical result to determine the interface between two types of the same oil emulsion: the emulsion of produced water in oil and the emulsion of oil in produced water, and also between the emulsion of produced water in oil and produced water. In each of the emulsions, there is a vertical gradient of concentrations and, therefore, a vertical gradient of dielectric constant, electrical conductivity and electrical impedance.

 The achieved result allows us to determine the level of the lower boundary of the layer of formation water emulsion in oil in a dehydrator.

 A higher technical result is achieved by the fact that in the prototype, using identical measuring transducers, they receive signals at two depths in the medium under study and compare them, but, unlike the prototype, identical measuring transducers are made in the form of a cylindrical insulated electrode connected into the oscillatory circuit of the oscillator, the frequency of which is the output signal of the measuring transducer, at the same time additionally receive a signal at a third depth in a metal tank oil dehydrator and comparing the RMS values of frequencies obtained in the lower and middle and upper and middle depths.

 According to the static characteristic of the measuring transducer (Fig. 1), the frequency of the oscillator depends on the type of emulsion, on the volumetric concentration of water in the emulsion of formation water in oil and changes so little with a change in the volume concentration in the emulsion of oil in formation water, including 100% (formation water ) that these changes can be neglected in practice.

 To disclose the essence of the proposed method, we give a brief description of the physical processes taking place in the dehydrator tank.

 In the dehydrator tank, where waterlogged oil is supplied, under the influence of natural forces (gravitational and pushing) and artificial influence (electric field, chemical reagents), the process of destruction of the emulsion and the separation of its components. But complete stratification does not occur; there is a concentration gradient. In oil emulsions, when a certain concentration of the dispersed phase is reached, a change in the type of emulsion occurs (phase reversal). Typically, in an oil emulsion in formation water, the separation process proceeds quickly, and formation water is already at a shallow depth from the unstable transition zone. The nature of the change in the concentration ratio over time is an ergodic stationary random process, therefore, it is necessary to compare the rms frequencies.

 If the rms values of the frequencies obtained at the lower and middle depths are almost equal, and at the middle and upper are different, then the lower boundary of the formation water emulsion in oil is between the upper and middle depths. The equality of signals from three depths indicates that this boundary is higher than the upper depth. The inequality of all three signals indicates that this boundary is somewhere below the average depth.

 In FIG. 1 is a graph of the RMS frequency of the measuring transducer versus the volumetric concentration of water in both types of emulsions (static characteristic of the measuring transducer); in FIG. 2 shows a functional block diagram of the level switch of the lower boundary of the layer of emulsion of formation water in oil in a dehydrator.

 The possibility of implementing the inventive method is confirmed by its implementation in the device of the level switch of the lower boundary of the layer of formation water emulsion in oil in a horizontal metal reservoir of a dehydrator of 3 m in diameter.

 The middle control point (hole) is located at a height of 1/3 of the diameter of the tank from its bottom. The depth interval between the control points is 200 mm.

 Three identical cylindrical electrodes, insulated by a dielectric, 200-300 mm long, 10-15 mm in diameter, are installed horizontally inside the tank through openings. Tightness is ensured by the execution of the housing in which the cylindrical electrode is mounted.

 Cylindrical electrodes insulated by a dielectric 1-3 are connected to the oscillating circuit of the corresponding oscillator 4-6, each of which is connected to a rms frequency unit (RMS block) 7-9. Block output c. short 7 is connected to one of the inputs of the comparison unit 10, the second input of which is connected to the output of the SCZ block 8. The output block SCZ 8 is also connected to one of the inputs of the comparison unit 11, the second input of which is connected to the output of the SCZ block 9. The comparison blocks have an indication of the results of the comparison.

 The metal wall of the tank serves as an electrode and forms, with each cylindrical electrode, insulated by an insulator 1-3, an electric capacitance, which is included in the oscillating circuit of the corresponding oscillator. A change in the dielectric constant of the medium in the interelectrode space changes the electric capacitance and, therefore, the frequency of the oscillator, which is the output value of the measuring transducer. Transmitters are identical. Their static characteristic is shown in FIG. 1. The negligible sensitivity to the volumetric water content in the oil emulsion in the formation water makes it possible to exclude the influence of the concentration gradient in it and to identify formation water with it. A significant difference in frequency values for different types of emulsions reveals the interface between the formation water emulsion in oil and the oil emulsion in produced water or produced water.

 The operations of obtaining the rms values of frequencies and comparing them in a given order are implemented on the basis of computer technology and stationary programs. The comparison operation can be performed by both subtraction and division.

Claims (1)

 A METHOD FOR DETERMINING THE LEVEL OF THE LOWER BOUNDARY OF A PLASTIC WATER EMULSION OIL IN AN OIL IN A DEHYDRATOR, consisting in the fact that signals are taken from identical measuring transducers located at two depths in the medium under study, they are compared and the desired value is determined by comparing them, which differs by measuring transducers are made in the form of a cylindrical electrode insulated by a dielectric connected to an oscillator circuit of a self-oscillator, the frequency of which is the output signal and Tonnage converter simultaneously remove further signal transmitter located at the third depth, and comparing the RMS values of the frequencies received at different depths.

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