Rapid detection method for chlorine content of ultra-deepwater gas field production water

Abstract

The invention relates to the technical field of oil and gas development, in particular to a rapid detection method for chlorine content in ultra-deep water gas field production water, which comprises the following steps: compounding actually obtained gas reservoir formation water to obtain compounded formation water, mixing the compounded formation water as a basic sample with pure water with different volumes, and detecting the content of chlorine in the pure water. The method comprises the following steps: testing to obtain chlorine content data of a mixed water sample under different compound formation water proportions, mixing the compound formation water with pure water with different volumes and ethylene glycol with different volumes, and measuring to obtain conductivity data of a mixed solution under different ethylene glycol concentrations and different compound formation water proportions; the quantitative characterization chart is established after the chlorine content data and the conductivity data are associated, and the chlorine content of the produced water sample can be obtained by combining the quantitative characterization chart only by detecting the ethylene glycol concentration and measuring the conductivity of the produced water sample during subsequent production detection, so that the chlorine content of the produced water sample is quickly obtained, and the detection time and cost are saved.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas development, and more specifically, to a rapid detection method for chloride content in production water of ultra-deep water gas fields. Background Art

[0002] The practice of water-driven gas reservoir development has proved that chloride monitoring is a proven and effective means of water breakthrough monitoring, which is crucial for predicting water breakthrough. However, in the context of deepwater development, the underwater pipeline network needs to be filled with ethylene glycol to meet the flow security requirements, which will result in the production water entering the slug flow collector of the offshore platform from the underwater pipeline network being a mixture of ethylene glycol and the actual water produced by the gas field. The content of ethylene glycol changes continuously with the production. If the actual chloride content of the actual water produced by the gas field is to be obtained, the influence of ethylene glycol must be deducted.

[0003] At present, the petroleum industry prefers silver nitrate titration method for the detection of chloride ion content, but the industry standard does not take into account the actual situation of dynamic addition of ethylene glycol in ultra-deepwater gas fields. Therefore, when testing the chloride content of produced water in ultra-deepwater gas fields, it is necessary to first test the ethylene glycol concentration based on the current industry standard, then conduct a nitrate titration test, and then deduct the volume occupied by ethylene glycol, and finally calculate the actual chloride content of the actual produced water of the gas field. The entire testing process is complex and the detection speed is slow. In addition, there are artificial visual and measurement errors in the deduction of ethylene glycol, and it is difficult to unify the standards, which will also affect the final detection accuracy and cannot fully meet the needs of water breakthrough prediction. Summary of the invention

[0004] In order to overcome the defects of slow detection speed and insufficient precision of the above-mentioned prior art detection method for chloride content in ultra-deep water gas field production water, the present invention provides a rapid detection method for chloride content in ultra-deep water gas field production water, improves the detection speed, and alleviates the inspection accuracy problem caused by inconsistent inspection standards to a certain extent.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a rapid detection method for the chloride content of ultra-deep water gas field production water, comprising the following steps:

[0006] Step 1: Take the formation water of the gas reservoir where the target gas well is located for chemical analysis to obtain the chemical ion composition of the formation water, and compound the formation water according to the chemical ion composition to obtain compound formation water;

[0007] Step 2: Mix the compound formation water with pure water to prepare multiple mixed water samples with different proportions of compound formation water, test the chloride content of the multiple mixed water samples respectively, establish a functional relationship between the chloride content of the mixed water sample and the proportion of compound formation water, and obtain a first relationship;

[0008] Step 3: Repeat the same multiple mixed water samples according to the mixed water sample preparation method in step 2, mix the multiple mixed water samples with different volumes of ethylene glycol respectively, prepare mixed solutions with different proportions of compounded formation water at different ethylene glycol concentrations, measure the conductivity of the mixed solution, obtain the functional relationship between the proportion of compounded formation water and the conductivity of the mixed solution at different ethylene glycol concentrations, and obtain the second relationship;

[0009] Step 4: Combine the first relationship and the second relationship to obtain the functional relationship between chloride content and conductivity at different ethylene glycol concentrations, and establish a quantitative characterization chart;

[0010] Step 5: During production testing, obtain production water samples from the target ultra-deepwater gas field, test and obtain data such as ethylene glycol concentration and conductivity of the production water samples, compare the data with the quantitative characterization plate, and then obtain the chloride content of the production water samples.

[0011] In the prior art, when obtaining production water samples, it is necessary to first test the ethylene glycol concentration and then test the chloride content. The test process is complex, the test speed is slow, and the error is large. In the present method, the formation water of the gas reservoir where the target gas well is located is directly used for compounding, and then mixed with pure water to obtain multiple mixed water samples. After the chloride content of the mixed water samples is tested respectively, the same mixed water sample is configured and different volumes of ethylene glycol are added to obtain multiple mixed solutions, and then the conductivity of the mixed solutions is tested respectively. When it is necessary to test the production water samples, it is only necessary to test the ethylene glycol concentration and conductivity of the production water samples. The ethylene glycol concentration and conductivity can be compared with the test data of the mixed solution to obtain the corresponding mixed solution data. The mixed solution data contains the ratio data of compound formation water and pure water, and then the data of the mixed water samples with the same ratio data can be found, and then The chloride content data of the mixed water sample data is obtained; that is, mixed water samples with different proportions of compound formation water correspond to different chloride content data, and the chloride content data is used as the standard reference value for subsequent production detection. Mixed water samples with different proportions of compound formation water also correspond to mixed solutions with different ethylene glycol contents, and each mixed solution corresponds to ethylene glycol concentration and conductivity data. In subsequent production, the corresponding mixed solution is found through the ethylene glycol concentration and conductivity data of the production water sample, and then the corresponding mixed water sample is found, and then the chloride content data of the corresponding mixed water sample is found; in this way, the error influence of ethylene glycol concentration on chloride content detection can be eliminated, and the detection speed can also be greatly improved.

[0012] Among them, the mixed water sample is used to reproduce the actual production process of the gas field from producing only condensate water, that is, distilled water, to producing both condensate water and formation water, so as to simulate the ion composition of the real production water of the gas field; the mixed solution with different ethylene glycol concentrations is used to simulate the gas field production water at the slug flow collector of the offshore platform of the ultra-deepwater gas field; in step four, the functional relationship between the chloride content and the conductivity under different ethylene glycol concentrations is obtained, that is, the chloride content of the mixed solution of ethylene glycol, compound formation water, and distilled water after deducting the volume of ethylene glycol is obtained, that is, the simulated chloride content of the production water of the ethylene glycol-rich gas field is obtained, and then the real production data is compared with the quantitative characterization plate to confirm the real chloride content of the production water sample. Specifically, in the mixed solution, each set ethylene glycol concentration is configured with a mixed water sample with a different proportion of compound formation water, and the detection data of the mixed solution can be grouped according to the concentration of ethylene glycol. Furthermore, in step three, the same volume of ethylene glycol is first mixed with mixed water samples with different proportions of compound formation water to obtain a mixed solution, and mixed solutions with different proportions of compound formation water of the same concentration are obtained respectively, and then mixed solutions with different proportions of compound formation water of different concentrations are respectively prepared.

[0013] Preferably, in step 2, the proportion of formation water in the mixed water sample is defined as W, The real chloride content of the mixed water sample is defined as Cl. The chloride content of the mixed water sample is detected to obtain Cl. A relationship curve between different formation water proportions W and chloride content Cl is obtained, and a first relationship Cl=f(W) is established.

[0014] Preferably, in step 3, the proportion of formation water in the mixed water sample is defined as W, Define the concentration of ethylene glycol as Meg, The conductivity of the mixed solution is defined as σ; the conductivity of the mixed solution is measured to obtain a functional relationship curve between the proportion of composite formation water and the conductivity of the mixed solution under different ethylene glycol concentrations, and a second relationship W=g(σ,Meg) is established.

[0015] Preferably, in step 4, the functional relationship between the chloride content and the conductivity at different ethylene glycol concentrations is Cl=f(g(σ,Meg)). Establishing the functional relationship facilitates data processing and searching.

[0016] Preferably, in step 2, a Cl-W relationship chart is established based on the relationship curves between different formation water proportions W and chloride ion contents Cl. Establishing a relationship chart facilitates data comparison and can also more intuitively display data relationships.

[0017] Preferably, in step three, a W-Meg-σ relationship chart is established based on a functional relationship curve between the proportion of composite formation water and the conductivity of the mixed solution at different ethylene glycol concentrations.

[0018] Preferably, in step 2, the chloride content of the mixed water sample is detected by silver nitrate titration experiment. The chloride content detection is carried out by the commonly used silver nitrate titration experiment, but the chloride detection of this method belongs to the preparatory work before production detection and will not affect the detection speed during production detection.

[0019] Preferably, in step 2, the multiple mixed water samples are grouped, one group is used for the chloride content detection in step 2, and one group is used for the conductivity measurement in step 3. More mixed water samples are configured at a time and then grouped separately, and different groups of mixed solutions are used in different operations to maintain the consistency of the mixed solution and improve data accuracy.

[0020] Preferably, in step 2 and step 3, the pure water is distilled water, which is easy to prepare and has low preparation cost.

[0021] Preferably, in step five, a production water sample is obtained from a slug flow collector of the target ultra-deep water gas field.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] Compounded formation water is obtained by compounding the actual gas reservoir formation water, which is then used as a basic sample and mixed with different volumes of pure water. The chloride content data of the mixed water samples at different proportions of compounded formation water are obtained by testing. The compounded formation water is then mixed with different volumes of pure water and different volumes of ethylene glycol, and the conductivity data of the mixed solutions at different ethylene glycol concentrations and different proportions of compounded formation water are obtained by measuring. The chloride content data and the conductivity data are correlated to establish a quantitative characterization chart. In subsequent production testing, it is only necessary to test the ethylene glycol concentration and measure the conductivity of the production water sample, and the chloride content of the production water sample can be obtained in combination with the quantitative characterization chart, thereby quickly obtaining the chloride content of the production water sample, saving testing time and cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a flow chart of a method for rapid detection of chloride content in production water of ultra-deep water gas fields of the present invention;

[0025] Figure 2 It is a Cl-W relationship chart of a rapid detection method for the chloride content of production water in ultra-deep water gas fields of the present invention, which reflects the experimental relationship curve between the chloride content of a mixed water sample and the proportion of compound formation water;

[0026] Figure 3 It is a W-Meg-σ relationship chart of a rapid detection method for the chloride content of produced water in ultra-deep water gas fields of the present invention, which reflects the functional relationship between the proportion of composite formation water and the conductivity when the mixed solution has different ethylene glycol concentrations;

[0027] Figure 4 The invention discloses a quantitative characterization chart for a rapid detection method of chloride content in production water of ultra-deep water gas fields, which reflects the relationship between the conductivity and chloride content of production water samples at different ethylene glycol concentrations. DETAILED DESCRIPTION

[0028] The drawings are only used for illustrative purposes and should not be construed as limitations on this patent. In order to better illustrate this embodiment, some data in the drawings may be omitted and do not represent actual test data. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0029] The technical solution of the present invention is further described in detail below through specific embodiments and in conjunction with the accompanying drawings:

[0030] Example 1

[0031] like Figure 1 and Figure 4 As shown, a rapid detection method for the chloride content of produced water in ultra-deep water gas fields comprises the following steps:

[0032] Step 1: Take the formation water of the gas reservoir where the target gas well is located for chemical analysis to obtain the chemical ion composition of the formation water, and compound the formation water according to the chemical ion composition to obtain compound formation water;

[0033] Step 2: Mix the compound formation water with pure water to prepare multiple mixed water samples with different proportions of compound formation water, test the chloride content of the multiple mixed water samples respectively, establish a functional relationship between the chloride content of the mixed water sample and the proportion of compound formation water, and obtain a first relationship;

[0034] Step 3: Repeat the same multiple mixed water samples according to the mixed water sample preparation method in step 2, mix the multiple mixed water samples with different volumes of ethylene glycol respectively, prepare mixed solutions with different proportions of compounded formation water at different ethylene glycol concentrations, measure the conductivity of the mixed solution, obtain the functional relationship between the proportion of compounded formation water and the conductivity of the mixed solution at different ethylene glycol concentrations, and obtain the second relationship;

[0035] Step 4: Combine the first relationship and the second relationship to obtain the functional relationship between chloride content and conductivity at different ethylene glycol concentrations, and establish a quantitative characterization chart;

[0036] Step 5: During production testing, obtain production water samples from the target ultra-deepwater gas field, test and obtain data such as ethylene glycol concentration and conductivity of the production water samples, compare the data with the quantitative characterization plate, and then obtain the chloride content of the production water samples.

[0037] In the prior art, when obtaining production water samples, it is necessary to first test the ethylene glycol concentration and then test the chloride content. The test process is complex, the test speed is slow, and the error is large. In this method, the formation water of the gas reservoir where the target gas well is located is directly used for compounding, and then mixed with pure water to obtain multiple mixed water samples. After the chloride content of the mixed water samples is tested respectively, the same mixed water sample is configured and different volumes of ethylene glycol are added to obtain multiple mixed solutions, and then the conductivity of the mixed solutions is tested respectively. When it is necessary to test the production water samples, it is only necessary to test the ethylene glycol concentration and conductivity of the production water samples. The ethylene glycol concentration and conductivity can be compared with the test data of the mixed solution to obtain the corresponding mixed solution data. The mixed solution data contains the ratio data of compound formation water and pure water, and then the data of the mixed water samples with the same ratio data can be found, and then the mixed solution data with the same ratio data can be obtained. The chloride content data of the mixed water sample data; that is, mixed water samples with different proportions of compound formation water correspond to different chloride content data, and the chloride content data is used as the standard reference value for subsequent production detection. Mixed water samples with different proportions of compound formation water also correspond to mixed solutions with different ethylene glycol contents, and each mixed solution corresponds to ethylene glycol concentration and conductivity data. In subsequent production, the corresponding mixed solution is found through the ethylene glycol concentration and conductivity data of the production water sample, and then the corresponding mixed water sample is found, and then the chloride content data of the corresponding mixed water sample is found; in this way, the error influence of ethylene glycol concentration on chloride content detection can be eliminated, and the detection speed during production can be greatly improved.

[0038] Among them, the mixed water sample is used to reproduce the actual production process of the gas field from producing only condensate water, i.e., distilled water, to producing both condensate water and formation water, thereby simulating the ion composition of the real production water of the gas field; the mixed solution with different ethylene glycol concentrations is used to simulate the gas field production water at the slug flow collector of the offshore platform of the ultra-deepwater gas field; in step four, the functional relationship between the chloride content and the electrical conductivity under different ethylene glycol concentrations is obtained, that is, the chloride content of the mixed solution of ethylene glycol, compound formation water, and distilled water after deducting the volume of ethylene glycol is obtained, that is, the simulated chloride content of the production water of the ethylene glycol-rich gas field is obtained, such as Figure 4 As shown, the actual production data is then compared with the quantitative characterization plate to confirm the actual chloride content of the production water sample.

[0039] Specifically, in the mixed solution, each set ethylene glycol concentration is configured with mixed water samples with different compound formation water ratios, and the detection data of the mixed solution can be grouped according to the concentration of ethylene glycol. Further, in step three, the same volume of ethylene glycol is first used to mix with mixed water samples with different compound formation water ratios to obtain a mixed solution, and mixed solutions with different compound formation water ratios of the same concentration are obtained, and then mixed solutions with different concentrations and different compound formation water ratios are respectively configured.

[0040] The beneficial effects of this embodiment are as follows: compounded formation water is obtained by compounding the actually obtained gas reservoir formation water, and then the compounded formation water is used as a basic sample. After being mixed with different volumes of pure water, the chloride content data of the mixed water samples at different proportions of compounded formation water are obtained by testing, and then the compounded formation water is mixed with different volumes of pure water and different volumes of ethylene glycol, and then the conductivity data of the mixed solution at different ethylene glycol concentrations and different proportions of compounded formation water are obtained by measuring, and a quantitative characterization plate is established after correlating the chloride content data with the conductivity data. In subsequent production detection, it is only necessary to detect the ethylene glycol concentration of the production water sample and measure the conductivity, and the chloride content of the production water sample can be obtained in combination with the quantitative characterization plate, thereby quickly obtaining the chloride content of the production water sample, saving detection time and cost.

[0041] Example 2

[0042] Based on Example 1, the difference from Example 1 is that:

[0043] In step 2, the proportion of formation water in the mixed water sample is defined as W. The real chloride content of the mixed water sample is defined as Cl. The chloride content of the mixed water sample is detected to obtain Cl. A relationship curve between different formation water proportions W and chloride content Cl is obtained, and a first relationship Cl=f(W) is established.

[0044] Furthermore, in step 3, the proportion of formation water in the mixed water sample is defined as W. Define the concentration of ethylene glycol as Meg, The conductivity of the mixed solution is defined as σ; the conductivity of the mixed solution is measured to obtain a functional relationship curve between the proportion of composite formation water and the conductivity of the mixed solution under different ethylene glycol concentrations, and a second relationship W=g(σ,Meg) is established.

[0045] Furthermore, in step 4, the functional relationship between the chloride content and the conductivity under different ethylene glycol concentrations is Cl=f(g(σ,Meg)). Establishing the functional relationship facilitates data processing and searching.

[0046] Further, such as Figure 2 As shown, in step 2, according to the relationship curve between different formation water proportions W and chloride ion contents Cl, a Cl-W relationship chart is established. Establishing a relationship chart facilitates data comparison and can also more intuitively display data relationships.

[0047] Further, such as Figure 3 As shown, in step three, a W-Meg-σ relationship chart is established based on the functional relationship curve between the proportion of composite formation water and the conductivity of the mixed solution at different ethylene glycol concentrations.

[0048] The remaining features and working principles of this embodiment are consistent with those of Embodiment 1.

[0049] Example 3

[0050] Based on Example 1 or Example 2, Example 1 or Example 2 is further limited, and the difference is that:

[0051] In step 2, the chloride content of the mixed water sample is tested by silver nitrate titration experiment. The chloride content is tested by the commonly used silver nitrate titration experiment, but the chloride detection of this method belongs to the preparatory work before production and will not affect the detection speed during production.

[0052] Furthermore, in step 2, the multiple mixed water samples are grouped, one group is used for the chloride content detection in step 2, and the other group is used for the conductivity measurement in step 3. More mixed water samples are configured at a time and then grouped separately. Different groups of mixed solutions are used in different operations to maintain the consistency of the mixed solutions and improve data accuracy.

[0053] Furthermore, in step 2 and step 3, the pure water is distilled water, which is easy to prepare and has low preparation cost.

[0054] Furthermore, in step five, a production water sample is obtained from a slug flow collector of the target ultra-deepwater gas field.

[0055] The rest of the working principle and working process of this embodiment are consistent with those of Embodiment 1 or Embodiment 2.

[0056] In the specific contents of the above-mentioned specific implementation methods, the various technical features can be combined in any non-contradictory manner. In order to make the description concise, not all possible combinations of the above-mentioned technical features are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0057] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A rapid detection method for the chloride content of ultra-deep water gas field production water, characterized in that: The following steps are involved: Step 1: Take the formation water of the gas reservoir where the target gas well is located for chemical analysis to obtain the chemical ion composition of the formation water, and compound the formation water according to the chemical ion composition to obtain compound formation water; Step 2: Mix the compound formation water with pure water to prepare multiple mixed water samples with different proportions of compound formation water, test the chloride content of the multiple mixed water samples respectively, establish a functional relationship between the chloride content of the mixed water sample and the proportion of compound formation water, and obtain a first relationship; Step 3: Repeat the same multiple mixed water samples according to the mixed water sample preparation method in step 2, mix the multiple mixed water samples with different volumes of ethylene glycol respectively, prepare mixed solutions with different proportions of compounded formation water at different ethylene glycol concentrations, measure the conductivity of the mixed solution, obtain the functional relationship between the proportion of compounded formation water and the conductivity of the mixed solution at different ethylene glycol concentrations, and obtain the second relationship; Step 4: Combine the first relationship and the second relationship to obtain the functional relationship between chloride content and conductivity at different ethylene glycol concentrations, and establish a quantitative characterization chart; Step 5: During production testing, obtain production water samples from the target ultra-deepwater gas field, test and obtain data such as ethylene glycol concentration and conductivity of the production water samples, compare the data with the quantitative characterization plate, and then obtain the chloride content of the production water samples.

2. A rapid detection method for chloride content in ultra-deep water gas field production water according to claim 1, characterized in that: In step 2, the proportion of formation water in the mixed water sample is defined as W. The real chloride content of the mixed water sample is defined as Cl. The chloride content of the mixed water sample is detected to obtain Cl. A relationship curve between different formation water proportions W and chloride content Cl is obtained, and a first relationship Cl=f(W) is established.

3. A rapid detection method for chloride content in ultra-deep water gas field production water according to claim 2, characterized in that: In step 3, the proportion of formation water in the mixed water sample is defined as W. Define the concentration of ethylene glycol as Meg, The conductivity of the mixed solution is defined as σ; the conductivity of the mixed solution is measured to obtain a functional relationship curve between the proportion of composite formation water and the conductivity of the mixed solution under different ethylene glycol concentrations, and a second relationship W=g(σ,Meg) is established.

4. A rapid detection method for chloride content in ultra-deep water gas field production water according to claim 3, characterized in that: In step 4, the functional relationship between the chloride content and the conductivity at different ethylene glycol concentrations is Cl=f(g(σ,Meg)).

5. The method for rapid detection of chloride content in ultra-deep water gas field production water according to claim 2, characterized in that: In step 2, a Cl-W relationship chart is established based on the relationship curves between different formation water proportions W and chloride ion contents Cl.

6. A rapid detection method for chloride content in ultra-deep water gas field production water according to claim 3, characterized in that: In step three, a W-Meg-σ relationship chart is established based on the functional relationship curve between the proportion of composite formation water and the conductivity of the mixed solution at different ethylene glycol concentrations.

7. A rapid detection method for chloride content in ultra-deep water gas field production water according to claim 1, characterized in that: In step 2, the chloride content of the mixed water sample is tested by silver nitrate titration experiment.

8. The method for rapid detection of chloride content in produced water of ultra-deep water gas fields according to claim 1, characterized in that: In step 2, the multiple mixed water samples are grouped, one group is used for the chloride content detection in step 2, and the other group is used for the conductivity measurement in step 3.

9. The method for rapid detection of chloride content in ultra-deep water gas field production water according to claim 1, characterized in that: In step 2 and step 3, distilled water is used as pure water.

10. A rapid detection method for chloride content in ultra-deep water gas field production water according to claim 1, characterized in that: In step five, production water samples are obtained from the slug flow catcher of the target ultra-deepwater gas field.

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