Method for detecting sulfide in produced liquid

Abstract

The invention belongs to the technical field of petroleum detection, and relates to a method for detecting sulfide in produced liquid, an X-ray absorption method and a methylene blue spectrophotometric method are adopted for fitting, the method for detecting the content of sulfide in the produced liquid is established, and the calculation formula is C = C0 * omega0 + CW * omegaW, in the formula, C represents the content of sulfide in the produced liquid, and is mu g / L; c < 0 > is the content of sulfide in oil, and mu g / L; omega < 0 > is the mass fraction of oil in the produced liquid; cW represents the content of sulfide in water, and is mu g / L; and omega W is the mass fraction of water in the produced liquid. According to the method, the content of the sulfide in the produced liquid can be conveniently detected, complex collection, pretreatment and storage processes do not need to be carried out on a sample to be detected, large instruments are not needed, rapid, accurate and real-time detection of the sulfide can be achieved, the detection limit is lower, the sensitivity is higher, and the steps are more convenient.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil detection, and relates to a method for detecting sulfide in produced fluid. Background Art

[0002] Sulfur content is an important index in crude oil and its products. During the production and refining process of crude oil, the sulfur content directly affects the service life of production process equipment. Moreover, crude oil with too high sulfur content is prone to cause poisoning accidents, and releasing it into the atmosphere will also cause air pollution.

[0003] With the large-scale implementation of the development mode conversion in Liaohe Oilfield, the physical properties of crude oil in the entire Liaohe Oilfield have become increasingly complex, and the sulfide content in the produced fluid shows an increasing trend. The sulfide content is a key concern for the safety and environmental protection of oilfield production and is also basic data urgently needed for relevant engineering designs of the company.

[0004] Comparing with existing sulfide detection methods, the basic methods for detecting refined oil are: lamp burning method, X-ray absorption method, and ultraviolet fluorescence method, which are not applicable to oilfield produced fluid. Among them, the lamp burning method has complex operations and a long detection cycle.

[0005] The detection methods for industrial wastewater and domestic sewage are: methylene blue spectrophotometry and iodometric method, which are only applicable to surface water, groundwater, domestic sewage, and industrial wastewater. Methylene blue spectrophotometry has simple operations and little external interference, while the iodometric method is greatly interfered by suspended solids, chromaticity, and some heavy metal ions.

[0006] However, at present, there is a lack of a reasonable and effective method for detecting the sulfide content in oilfield produced fluid. Summary of the Invention

[0007] In order to overcome the deficiencies of the prior art, the present invention provides a method for detecting sulfide in produced fluid.

[0008] The technical solution of the present invention is as follows:

[0009] A method for detecting sulfide in produced fluid, which uses two methods of X-ray absorption method + methylene blue spectrophotometry for fitting to establish a detection method for the sulfide content in produced fluid;

[0010] Calculation formula: C = C 0 × ω 0 + C W × ω W ;

[0011] Wherein: C—the sulfide content in the produced fluid, μg / L;

[0012] C 0 —the sulfide content in oil, μg / L;

[0013] ω0 — Mass fraction of oil in the produced fluid;

[0014] C W — Content of sulfide in water, μg / L;

[0015] ω W — Mass fraction of water in the produced fluid.

[0016] Furthermore, the initial and final X-ray intensities are measured by the X-ray absorption method, and the sulfide content C in the oil can be determined. 0 .

[0017] Furthermore, the methylene blue spectrophotometry includes the following steps:

[0018] a. Establish a sampling method for liquid sulfide;

[0019] b. Establish a standard curve;

[0020] c. Determine the sample;

[0021] d. Calculate the sulfide content.

[0022] Furthermore, the specific steps for establishing a sampling method for liquid sulfide are as follows: During sampling, prevent aeration, and add an appropriate amount of sodium hydroxide solution and zinc acetate-sodium acetate solution to make the produced fluid alkaline and form zinc sulfide precipitate.

[0023] Furthermore, the specific steps for establishing a standard curve are as follows: Take eight stoppered colorimetric tubes, each add 20 mL of zinc acetate-sodium acetate solution. Respectively take 0 mL, 0.5 mL, 1 mL, 2 mL, 3 mL, 4 mL, 5 mL and 6 mL of sulfide standard stock solution and transfer them into each colorimetric tube. Add water to about 60 mL. Slowly add 10 mL of N,N-dimethyl-p-phenylenediamine solution along the wall of the colorimetric tube. Immediately stopper tightly and invert slowly once. Add 1 mL of ammonium ferric sulfate solution. Immediately stopper tightly and shake well. After standing for 10 min, dilute to the mark with water and shake well. Use a 1 cm colorimetric cell, use water as the reference, measure the absorbance at a wavelength of 665 nm, and conduct a blank test simultaneously.

[0024] Furthermore, the concentration of the sulfide standard stock solution is 0.1 mg / mL.

[0025] Furthermore, the specific steps for sample determination are as follows: The sample is acidified, the sulfide is converted into hydrogen sulfide, the hydrogen sulfide is blown out with nitrogen, transferred to an absorption and color development tube containing zinc acetate-sodium acetate solution, and reacts with N,N-dimethyl-p-phenylenediamine and ammonium ferric sulfate to form a blue complex, methylene blue, and is determined at a wavelength of 665 nm.

[0026] Further, the specific steps for calculating the sulfide content are as follows: The absorbance value measured at a wavelength of 665 nm for the sample in step c is substituted into the standard curve in step b to calculate the sulfide content C in the water. W .

[0027] The beneficial effects of the present invention compared with the prior art are as follows:

[0028] The sulfur content range of petroleum products in China is relatively wide. The analysis results formed by different analysis methods have relatively large errors in determining the product grade. Therefore, it is necessary to clarify the basic properties of the products, and through the research of detection methods, clarify the applicable ranges of various methods, improve the accuracy of analysis results, and operably guide the production plan and technical implementation of enterprises.

[0029] The method described in the present invention can conveniently detect the sulfide content in the produced fluid, without the need for complex collection, pretreatment, and preservation processes for the sample to be tested, without large-scale instruments, and can achieve rapid, accurate, and real-time detection of sulfide. Its detection limit is lower, the sensitivity is higher, and the steps are more convenient. Description of the Drawings

[0030] Figure 1 is a schematic diagram of an acidification-blowing-absorption device;

[0031] Among them, A is an acid addition reaction tube, B is a reaction flask, C is a straight condenser, and D is an absorption and color development tube. Detailed Embodiments

[0032] The present invention will be described in detail below through specific embodiments, but the protection scope of the present invention is not limited. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can all be obtained from commercial channels.

[0033] According to the characteristics of large water content in the produced fluid of Liaohe Oilfield, it is studied and determined to adopt two methods of X-ray absorption method + methylene blue spectrophotometry (acidification-blowing-absorption) for fitting to establish a detection method for the sulfide content in the produced fluid of Liaohe Oilfield.

[0034] The detection method uses the formula: C = C 0 × ω 0 + C W × ω W

[0035] In the formula: C is the sulfide content in the produced fluid;

[0036] C 0 —The sulfide content in the oil;

[0037] ω 0 —The mass fraction of oil in the produced fluid;

[0038] CW — Sulfide content in water;

[0039] ω W — Mass fraction of water in the produced fluid.

[0040] (1) X-ray absorption method

[0041] Principle: The γ-ray emitted by the X-ray absorption sulfur analyzer hits the Ag target, generating characteristic X-rays. The change in the sulfur content in the oil sample to be measured causes the attenuation of the X-ray intensity, and the attenuation follows the Lambert-Beer law. Only by accurately measuring the initial and final X-ray intensities can the sulfur content in the oil be accurately determined.

[0042] (2) Methylene blue spectrophotometry (acidification - blowing - absorption):

[0043] a. Establish a sampling method for liquid sulfide

[0044] Since sulfide ions are easily oxidized and hydrogen sulfide easily overflows from the produced fluid, aeration should be prevented during sampling, and an appropriate amount of sodium hydroxide solution and zinc acetate - sodium acetate solution should be added to make the produced fluid alkaline and form zinc sulfide precipitation.

[0045] b. Establishment of the standard curve

[0046] Take eight 100 mL stoppered colorimetric tubes, each add 20 mL of zinc acetate - sodium acetate solution. Respectively take 0 mL, 0.5 mL, 1 mL, 2 mL, 3 mL, 4 mL, 5 mL and 6 mL of sulfide standard working solution (common concentration is 0.1 mg / mL) and transfer them into each colorimetric tube. Add water to about 60 mL, slowly add 10 mL of N,N-dimethyl-p-phenylenediamine solution along the wall of the colorimetric tube, immediately stopper tightly and invert slowly once. Add 1 mL of ammonium ferric sulfate solution, immediately stopper tightly and shake well. After standing for 10 min, dilute to the mark with water and shake well. Use a 1 cm colorimetric cell, with water as the reference, measure the absorbance at a wavelength of 665 nm, and conduct a blank test simultaneously.

[0047] c. Sample determination:

[0048] The sample is acidified, the sulfide is converted into hydrogen sulfide, and the hydrogen sulfide is blown out with nitrogen and transferred to the absorption colorimetric tube containing zinc acetate - sodium acetate solution, reacting with N,N-dimethyl-p-phenylenediamine and ammonium ferric sulfate to form a blue complex, methylene blue, and measured at a wavelength of 665 nm.

[0049] d. Calculation of sulfide content: Substitute the absorbance value measured for the sample in step c at a wavelength of 665 nm into the standard curve in step b to calculate the sulfide content C in the water W .

[0050] Compare the two sets of test data according to the formula C = C0 ×ω 0 +C W ×ω W Fit out the sulfide content in the produced fluid.

[0051] According to the investigation of the production methods of each joint station, the production methods of the old stations of Shuwulian and Huanlian No. 3 are diverse, basically covering the production methods of each joint station. The produced fluids of the old stations of Shuwulian and Huanlian No. 3 are tested for the sulfide content. The test data are shown in the following table.

[0052] Table 1 Sulfide content of the produced fluid of Shuwulian

[0053] Serial Number Shuwulian Production Method Sulfide Content, μg / L 1 Zone 3 Fire Flooding 2.94～3.02 2 Zone 5 Conventional Heavy Oil 1.56～1.66 3 Zone 7 SAGD + Conventional Heavy Oil 1.92～2.1

[0054] Table 2 Sulfide content of the produced fluid of the old station of Huanlian No. 3

[0055] Serial Number Huanlian 3 Production Method Sulfide Content, μg / L 1 Zone 2 Steam + Huff and Puff 1.32～1.42 2 Zone 3 Huff and Puff 1.02～1.08 3 Zone 4 Huff and Puff + Steam + Fire Flooding 1.02～1.18

[0056] The above-described embodiments are only the preferred embodiments of the present invention, rather than all the feasible embodiments of the present invention. For those of ordinary skill in the art, any obvious changes made without departing from the principles and spirit of the present invention should be considered to be included within the scope of the claims of the present invention.

Claims

1. A method for detecting sulfide in produced fluid, characterized in that, the X-ray absorption method and the methylene blue spectrophotometry are used for fitting to establish a detection method for the sulfide content in the produced fluid; Calculation formula: C = C 0 × ω 0 + C W × ω W ; where: C—the sulfide content in the produced fluid, μg / L; C 0 — Sulfide content in oil, μg / L; ω 0 — mass fraction of oil in the produced fluid; C W — Content of sulfide in water, μg / L; ω W — mass fraction of water in the produced fluid.

2. The method for detecting sulfide in produced fluid according to claim 1, characterized in that, The initial and final X-ray intensities are measured by X-ray absorption method, and the sulfide content C in the oil can be determined. 0 。 3. The method for detecting sulfide in produced fluid according to claim 1, characterized in that, the methylene blue spectrophotometry includes the following steps: a. Establish a sampling method for liquid sulfide; b. Establish a standard curve; c. Determine the sample; d. Calculate the sulfide content.

4. The method for detecting sulfide in produced fluid according to claim 3, characterized in that, the specific steps for establishing the sampling method for liquid sulfide are: prevent aeration during sampling, and add an appropriate amount of sodium hydroxide solution and zinc acetate-sodium acetate solution to make the produced fluid alkaline and form zinc sulfide precipitation.

5. The method for detecting sulfide in produced fluid according to claim 3, characterized in that, the specific steps for establishing the standard curve are: take eight stoppered colorimetric tubes, add 20 mL of zinc acetate-sodium acetate solution to each, respectively take 0 mL, 0.5 mL, 1 mL, 2 mL, 3 mL, 4 mL, 5 mL and 6 mL of sulfide standard stock solution and transfer them into each colorimetric tube, add water to about 60 mL, slowly add 10 mL of N,N-dimethyl-p-phenylenediamine solution along the wall of the colorimetric tube, immediately stopper tightly and invert slowly once, add 1 mL of ammonium ferric sulfate solution, immediately stopper tightly and shake well, let stand for 10 min, then dilute to the mark with water, shake well, use a 1 cm colorimetric cell, use water as the reference, measure the absorbance at a wavelength of 665 nm, and conduct a blank test at the same time.

6. The method for detecting sulfide in produced fluid according to claim 5, characterized in that, the concentration of the sulfide standard stock solution is 0.1 mg / mL.

7. The method for detecting sulfide in produced fluid according to claim 3, characterized in that, the specific steps for sample determination are: the sample is acidified, the sulfide is converted into hydrogen sulfide, the hydrogen sulfide is blown out with nitrogen, transferred to an absorption and color development tube containing zinc acetate-sodium acetate solution, and reacts with N,N-dimethyl-p-phenylenediamine and ammonium ferric sulfate to form a blue complex methylene blue, and the measurement is carried out at a wavelength of 665 nm.

8. The method for detecting sulfide in produced fluid according to claim 3, characterized in that, The specific steps for calculating the sulfide content are as follows: The absorbance value measured for the sample at a wavelength of 665 nm is substituted into the standard curve in step b to calculate the sulfide content C in the water W .

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