CN111380822A - System for measuring oil content in water in petroleum production process - Google Patents

Abstract

The invention discloses a system for measuring oil content in water in the petroleum production process, which comprises a first reference beam, a second reference beam and a detector, and further comprises a tracking module for the oil content in the water, wherein the tracking module monitors the oil content in the water by adopting the following steps: s1, carrying out quantitative analysis by using the oil content scattering absorption in the first reference beam water; s2, recording the suspended matter content IR and the oil content UV in the water by using a second reference beam to track the background; s3, acquiring the absorption coefficient K of the oil layer through the Lambert beer law according to the content value IR of the suspended matters and the content value UV of the oil body, tracking and updating the suspended matters in real time by using a second reference beam, and measuring an absorption scattering system of main suspended matters during calibration, thereby eliminating the influence of the suspended matters and realizing the real-time detection of the relation between the oil content and the light intensity.

Description

System for measuring oil content in water in petroleum production process

Technical Field

The invention relates to the field of oil-water content detection in the petroleum production process, in particular to a system for measuring the oil-water content in water in the petroleum production process.

Background

The detection of the oil content in the water refers to the detection of the liquid oil content in the water body. Because oil has a lower density than water and is insoluble in water, it is not uniformly distributed in the fluid in the two-phase oil-water or three-phase oil, water, and gas state. Therefore, the detection of the oil content in water, especially in complex pipeline fluids, is a considerable technical difficulty. The oil content detection has important application in the fields of petrochemical industry, environmental protection and the like. The oil content in the water body is too high, which not only causes the waste of oil, but also seriously pollutes the environment. Therefore, the accurate detection of the oil content can provide reliable basis for the control of various industrial and domestic drainage, and has extremely important function.

The existing oil content measurement can be divided into three categories: chemical, optical, electrical methods. The first type is a chemical method, which is to measure the oil content by using the product of the chemical reaction of the oil. The main method is to use the oil and fat and alkaline solution to have saponification reaction, and the content of the generated fatty acid metal salt (soap) is used for measuring the oil content; the optical method is to collect the size of the absorption peak of the infrared absorption spectrum to measure the oil content by utilizing the difference of the absorption degree of the oil to the infrared light; the electrical method adopts a capacitance type double-electrode probe, and utilizes the difference between the dielectric constant of grease and the water body to measure the change of capacitance in the water body, thereby obtaining the change of oil content.

The prior art has the following disadvantages:

1. chemical measurement method: the time is long, the operation is inconvenient, and the method is only suitable for laboratories;

2. an electrical method comprises the following steps: in the acquisition process of the capacitance double-electrode probe, the application occasions are also limited due to the fact that the capacitance of the probe is extremely small and the probe is easily interfered, and the cost of the probe is low.

3. The optical method comprises the following steps: an infrared absorption or ultraviolet fluorescence method is generally adopted in a laboratory, and is a convenient measurement method which is simple to operate and does not need special chemical treatment, but because the molecular structure in the grease is quite complex, and the infrared absorption/ultraviolet fluorescence spectrum intensity is closely related to the type of an oil product, the oil product is generally required to be calibrated independently aiming at specific calibration oil products.

Disclosure of Invention

The technical problem to be solved by the invention is to overcome the defects of the prior art, and the oil content under the complex fluid condition can be conveniently measured by utilizing different optical physical properties of oil and water and adopting an optical method.

In order to solve the technical problems in the prior art, the technical scheme adopted by the invention is as follows:

1. a system for measuring oil content in water during oil production; the system comprises a first reference beam, a second reference beam and a detector, and further comprises a module for tracking the oil content in water, wherein the tracking module monitors the oil content in water by adopting the following steps:

s1, carrying out quantitative analysis by using the oil content scattering absorption in the first reference beam water;

s2, recording the suspended matter content IR and the oil content UV in the water by using a second reference beam to track the background;

and S3, acquiring the absorption coefficient K of the oil layer according to the suspended matter content value IR and the oil body content value UV through the Lambert beer law.

The background tracking process is carried out on the suspension content value IR and the oil body content value UV in the S2:

and 2.1, substituting the IR value into a calibration formula to obtain a stable oil content value which changes randomly when the delta UV change is smaller than a threshold value.

2.2, when Δ UV is not substantially changed, i.e. close to 0 or less than 0, the real-time tracking function of IR0, UV0, real-time background is updated again.

The step S3 is a process of obtaining an absorption coefficient K of the oil layer through lambert beer' S law:

3.1, after the second reference beam passes through a section of liquid medium with the length of L, the light intensity of emergent light I will be attenuated:

I＝I0e-KCL (1)

wherein K is the absorption coefficient and C is the liquid concentration or turbidity;

3.2, calculating the light intensity of emergent light by the following formula:

I＝I0e-(K1*C1*L)-(k2*C2*L)-K3*L (2)

wherein K1 and C1 are absorption coefficient and concentration of oil, and K2 and C2 are absorption coefficient, concentration/turbidity of suspended matter; k3 is the absorption coefficient of water;

let I0 ═ I0 e-K2 ═ C2 ═ L-K3 ═ L

Then (2) becomes: i ═ I0' e-K1 ═ C1 ═ L (3)

3.3, to find the calculation methods for K1, K2 and K3,

firstly, measuring the emergent light intensity of 100% water and the emergent light intensity of 100% oil to obtain K3 and K1 respectively;

then, in the case of water alone and suspended matter, K2 can be determined by measuring the transmittance of a known amount of suspended matter, such as a fixed amount of silica sand/suspended microspheres.

Advantageous effects

Compared with the prior art, the invention has the beneficial effects that:

(1) the method does not need to calibrate specific oil products independently, and has universal applicability after calibration is completed.

(2) And the influence caused by larger background change in the fluid is eliminated by adopting a real-time background technology.

(3) The real-time background technology is adopted, and the influence of attenuation caused by the influence of temperature on the light source is eliminated.

(4) The invention relates to the field of oil-water content detection in the petroleum production process, in particular to a method for measuring the oil content in water in the petroleum production process, which aims to overcome the technical defects in the prior art, and adopts an optical method by utilizing different optical physical properties of oil and water to conveniently realize the specific method for measuring the oil content under the condition of complex fluid, wherein the specific method comprises the following steps: according to the Lambert-beer law, incident light is attenuated after passing through a medium, the attenuation in the fluid is mainly caused by absorption scattering of oil drops and absorption scattering of suspended matters, the suspended matters are tracked and updated in real time by using a second reference beam, and an absorption scattering system of the main suspended matters is measured during calibration, so that the influence of the suspended matters is eliminated, and the real-time detection of the relation between the oil content and the light intensity is realized.

Drawings

FIG. 1 is a diagram of a system for measuring oil content in water during oil production according to the present invention. Wherein:

1. infrared light source

2. Three-band (infrared, visible fluorescence, ultraviolet) detector

3. Ultraviolet light source

The infrared light source 1 and the ultraviolet light source 3 are synchronized in real time through the detector 2 to obtain real-time infrared scattering absorption intensity S1 and ultraviolet fluorescence intensity F1 in the fluid, and the oil/water content of the current fluid can be obtained in real time by comparing the stored scattering absorption backgrounds S0 and F0 and introducing a calibration coefficient.

Detailed Description

An infrared light source with constant 880nm current is adopted to emit incident light, the incident light is converted into approximately parallel light through a lens, then the approximately parallel light enters the fluid to be measured through an oil-proof coating, a background BKIR is stored after the fluid is stable, a reference beam adopts 380nm UV light, a background value BKUV in the pure water fluid is recorded, and at the moment, an IR value reflects the condition of particles in the fluid (when the particles are 0) and reflects the condition of oil content in the fluid; adding appropriate amount of suspended substance, stirring thoroughly to make suspended substance uniformly distributed in fluid, and recording IR0 and UV 0; then the fluid in the optical cell is changed, the optical cell is filled with 100% oil, the IRf and the UVf at the moment are obtained, and the basic parameters are obtained through the steps, so that the values of K1, K2 and K3 can be obtained. When the absolute value change of the delta UV (UV-UV0) is larger than a certain threshold value, the IR value is input into a calibration formula to obtain the oil content value at the moment, and when the absolute value change of the delta UV is smaller than the threshold value, the IR value is not changed greatly and is substituted into the calibration formula to obtain a more stable oil content value which changes randomly. When Δ UV is substantially unchanged, i.e., close to 0 or less than 0, then the real-time tracking functionality of IR0, UV0, real-time background is re-updated.

Wherein, the calculation process of K1, K2 and K3 values is as follows:

(1) and (3) deducing a detection principle: according to the lambert-beer law, after incident light I0 passes through a liquid medium with a length L, the light intensity of emergent light I is attenuated:

I＝I0e-KCL (1)

wherein K is the absorption coefficient and C is the liquid concentration or turbidity;

when the liquid contains two or more than 2 media, as shown in fig. 1, C1 represents the oil content, C2 represents the suspended matter content, and these 2 media float in the water sample of L, the light intensity of the emergent light is:

I＝I0e-(K1*C1*L)-(k2*C2*L)-K3*L (2)

wherein K1 and C1 are absorption coefficient and concentration of oil, and K2 and C2 are absorption coefficient, concentration/turbidity of suspended matter; k3 is the absorption coefficient of water

Let I0 ═ I0 e-K2 ═ C2 ═ L-K3 ═ L

Then (2) becomes: i ═ I0' e-K1 ═ C1 ═ L (3)

In order to find out the calculation methods of K1, K2 and K3, the light intensity of 100% water and the light intensity of 100% oil are firstly measured to obtain K3 and K1 respectively;

k2 can then be determined by measuring the transmission of a known amount of suspended matter, such as a fixed amount of silica sand/suspended microspheres, in the presence of water alone and suspended matter.

After these 3 parameters are obtained, the actual oil content can be measured.

(3) Logarithm is taken at both ends of the formula:

C1＝k1*L*ln(I0’/I0)； (4)

in the actual fluid test, the suspended matters are continuously changed along with the fluid, so that the suspended matters need to be measured in real time;

the method uses a second reference beam to track the suspension in real time, and when no oil drop exists in the fluid, the second reference beam gives a feedback signal, and the I0' is updated in real time.

The infrared light source 1 of the present invention uses a 880nm light source to avoid absorption bands of other organic matters in oil or water, thereby avoiding absorption scattering associated with specific oil products.

The ultraviolet light source 3 adopts a 380nm light source to generate ultraviolet fluorescence in a visible light wave band, so that the ultraviolet fluorescence is detected by the three-wave-band detector 2.

Practical calculation example:

in the calibrated oil-water measuring system, K1, K2, K3;

at this time, after the machine is started, the water background is preserved after the fluid is stabilized: BKIR 3000BKUV 10

The IR value then reflects the condition of the particulate matter in the fluid; the UV value reflects the content of the fluid or the condition of the oil product; in the system operation process, calculating an absolute value of (UV-BKUV) in real time, wherein when the change of the delta UV is larger than 1, an IR value IR is 5, and inputting the IR value IR into a calibration formula to obtain an oil content value at the time of 50 ppm; when the variation of the delta UV is smaller than 1, if the variation of the IR value is not large, R is substituted into a calibration formula, and a more stable oil content value with random variation is obtained and is less than 50 ppm. When Δ UV <0.1, the system re-records IR0 and UV0 re-preserves the background.

Although the preferred embodiments of the present invention have been described with reference to the accompanying drawings, the present invention is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and those skilled in the art can make various modifications without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims (3)

1. A system for measuring oil content in water in an oil production process comprises a first reference beam, a second reference beam and a detector, and is characterized by further comprising a tracking module for tracking the oil content in the water, wherein the tracking module monitors the oil content in the water by adopting the following steps:

s1, carrying out quantitative analysis by using the oil content scattering absorption in the first reference beam water;

s2, recording the suspended matter content IR and the oil content UV in the water by using a second reference beam to track the background;

and S3, acquiring the absorption coefficient K of the oil layer according to the suspended matter content value IR and the oil body content value UV through the Lambert beer law.

2. The system for measuring oil content in water in oil production process according to claim 1, wherein the suspension content value IR and the oil content value UV in S2 are followed by background tracking process:

and 2.1, substituting the IR value into a calibration formula to obtain a stable oil content value which changes randomly when the delta UV change is smaller than a threshold value.

2.2, when Δ UV is not substantially changed, i.e. close to 0 or less than 0, the real-time tracking function of IR0, UV0, real-time background is updated again.

3. The system for measuring the oil content in water in the oil production process according to claim 1, wherein the step S3 is performed by obtaining the absorption coefficient K of the oil layer according to lambert beer' S law:

3.1, after the second reference beam passes through a section of liquid medium with the length of L, the light intensity of emergent light I will be attenuated:

I＝I0e-KCL (1)

wherein K is the absorption coefficient and C is the liquid concentration or turbidity;

3.2, calculating the light intensity of emergent light by the following formula:

I＝I0e-(K1*C1*L)-(k2*C2*L)-K3*L (2)

wherein K1 and C1 are absorption coefficient and concentration of oil, and K2 and C2 are absorption coefficient, concentration/turbidity of suspended matter; k3 is the absorption coefficient of water;

let I0 ═ I0 e-K2 ═ C2 ═ L-K3 ═ L

Then (2) becomes: i ═ I0' e-K1 ═ C1 ═ L (3)

3.3, to find the calculation methods for K1, K2 and K3,

firstly, measuring the emergent light intensity of 100% water and the emergent light intensity of 100% oil to obtain K3 and K1 respectively;

then, in the case of water alone and suspended matter, K2 can be determined by measuring the transmittance of a known amount of suspended matter, such as a fixed amount of silica sand/suspended microspheres.

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