A rapid detection method for water chlorinity content of ultra-deep water gas field production

Abstract

The present application relates to the technical field of oil and gas development, more particularly, to a rapid detection method for water chloride content of ultra-deep water gas field production, the method comprises the following steps: obtaining a compound formation water by compounding real formation water of a gas reservoir, taking the compound formation water as a basic sample, mixing the basic sample with pure water of different volumes, testing the chloride content data of the mixed water sample under different proportions of the compound formation water, mixing the compound formation water with pure water of different volumes and ethylene glycol of different volumes, measuring the conductivity data of the mixed solution under different proportions of the compound formation water and different concentrations of ethylene glycol, correlating the chloride content data and the conductivity data to establish a quantitative characterization chart, and subsequently detecting the ethylene glycol concentration and the conductivity of the production water sample, and then combining the quantitative characterization chart to obtain the chloride content of the production water sample, thereby quickly obtaining the chloride content of the production water sample and saving detection time and cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas development, more particularly, to a rapid detection method for the chloride content of production water in an ultra-deep water gas field. BACKGROUND

[0002] It has been proven in the development practice of water-drive gas reservoirs that chloride monitoring is a practical and effective water breakthrough monitoring method, which is crucial for water breakthrough prediction. However, in the context of deep water development, glycol needs to be added to the underwater pipe network to meet the safety requirements of flow assurance, which will result in that the production water entering the slug catcher of the offshore platform from the underwater pipe network is a mixture of glycol and actual produced water from the gas field, and the content of glycol is constantly changing as production proceeds. If the true chloride content of the actual produced water from the gas field is to be obtained, the influence of glycol must be deducted.

[0003] Currently, the silver nitrate titration method is the first choice for detecting the chloride ion content in the petroleum industry. However, the current standard does not take into account the actual situation of dynamic addition of glycol in ultra-deep water gas fields. Therefore, for the detection of chloride content in production water in ultra-deep water gas fields, the glycol concentration needs to be tested first based on the current standard, then the nitrate titration test is carried out, then the volume occupied by glycol is deducted, and finally the true chloride content of the actual produced water from the gas field is calculated. The whole test process is complex, the detection speed is slow, there are human visual and measurement errors in the deduction of glycol, the standard is difficult to unify, and the final detection accuracy is affected, which cannot fully meet the demand for water breakthrough prediction. SUMMARY

[0004] To overcome the defects of slow detection speed and insufficient accuracy of the existing detection method for chloride content in production water in ultra-deep water gas fields, the present application provides a rapid detection method for chloride content in production water in ultra-deep water gas fields, which improves the detection speed and to some extent alleviates the problem of test accuracy caused by the non-uniformity of test standards.

[0005] To solve the above technical problems, the technical solution adopted by the present application is as follows: a rapid detection method for chloride content in production water in ultra-deep water gas fields, comprising the following steps:

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

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

[0008] Step 3: Repeat the same method of preparing multiple mixed water samples as in Step 2. Mix each mixed water sample with different volumes of ethylene glycol to prepare mixed solutions with different proportions of formation water at different ethylene glycol concentrations. Measure the conductivity of the mixed solutions to obtain the functional relationship between the proportion of formation water and the conductivity of the mixed solutions at different ethylene glycol concentrations, thus obtaining the second relationship.

[0009] Step 4: Combine the first and second equations 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, production water samples are obtained from the target ultra-deep water gas field. Data such as the ethylene glycol concentration and conductivity of the production water samples are obtained. The data are compared with quantitative characterization charts to determine the chloride content of the production water samples.

[0011] In existing technologies, obtaining production water samples requires first testing the ethylene glycol concentration and then detecting the chloride content. This process is lengthy, slow, and prone to errors. This method directly utilizes formation water from the gas reservoir where the target gas well is located, mixes it with pure water to obtain multiple mixed water samples, and tests the chloride content of each. Then, identical mixed water samples are prepared, and different volumes of ethylene glycol are added to each to obtain multiple mixed solutions. The conductivity of each mixed solution is then measured. When testing production water samples, only the ethylene glycol concentration and conductivity of the production water sample need to be measured. By comparing the ethylene glycol concentration and conductivity data with the mixed solution data, the corresponding mixed solution data can be obtained. This mixed solution data includes the ratio of mixed formation water to pure water, allowing the identification of mixed water samples with the same ratio. The chloride content data of the mixed water sample is obtained; that is, mixed water samples with different proportions of formation water have different chloride content data. This chloride content data serves as a standard reference value for subsequent production testing. Mixed water samples with different proportions of formation water also correspond to mixed solutions with different ethylene glycol contents. Each mixed solution has corresponding ethylene glycol concentration and conductivity data. During subsequent production, the corresponding mixed solution is found by using the ethylene glycol concentration and conductivity data of the production water sample, and then the corresponding mixed water sample is found, and finally 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 be greatly improved.

[0012] The mixed water samples are used to reproduce the actual production process of the gas field, from producing only condensate water (distilled water) to producing both condensate water and formation water, thereby simulating the ionic composition of the actual production water in the gas field. Mixed solutions with different ethylene glycol concentrations are used to simulate the gas field production water at the plug flow trap on the offshore platform of the ultra-deepwater gas field. In step four, the functional relationship between chloride content and conductivity at different ethylene glycol concentrations is obtained, i.e., the chloride content of the mixed solution of ethylene glycol, mixed formation water, and distilled water after deducting the volume of ethylene glycol is obtained, thus obtaining the simulated chloride content of the ethylene glycol-rich gas field production water. Subsequently, the actual chloride content of the production water sample is confirmed by comparing it with real production data and quantitative characterization charts. Specifically, for each set ethylene glycol concentration, mixed water samples with different proportions of mixed formation water are prepared, and the detection data of the mixed solutions can be grouped according to the ethylene glycol concentration. Furthermore, in step three, the same volume of ethylene glycol is first mixed with mixed water samples of different formation water ratios to obtain mixed solutions, and then mixed solutions of different formation water ratios with the same concentration are obtained. Then, mixed solutions of different concentrations with different formation water ratios are prepared.

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

[0014] Preferably, in step three, the proportion of formation water in the mixed water sample is defined as W. Define the ethylene glycol concentration as Meg. The conductivity of the mixture is defined as σ. The conductivity of the mixture is measured to obtain the functional relationship curves between the proportion of formation water and the conductivity of the mixture at different ethylene glycol concentrations. The second relationship W = g(σ,Meg) is then established.

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

[0016] Preferably, in step two, a Cl-W relationship chart is established based on the relationship curves between the proportion of formation water (W) and the chloride content (Cl) at different formations. Establishing a relationship chart facilitates data comparison and also provides a more intuitive display of the data relationships.

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

[0018] Preferably, in step two, the chloride content of the mixed water sample is detected by silver nitrate titration. While the chloride content is detected using the commonly used silver nitrate titration method, this chloride detection is a preparatory step before production testing and will not affect the testing speed during production.

[0019] Preferably, in step two, the prepared mixed water samples are grouped, with one group used for chloride content detection in step two and the other for conductivity measurement in step three. Preparing more mixed water samples at once and then grouping them further, with different groups of mixed solutions used for different operations, maintains the consistency of the mixed solutions and improves data accuracy.

[0020] Preferably, in steps two and three, distilled water is used. Distilled water is easy to prepare and has low preparation cost.

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

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] By compounding real gas reservoir formation water, a composite formation water was obtained. This composite formation water was then used as a base sample and mixed with different volumes of pure water. The chloride content of the mixed water samples with different composite formation water ratios was analyzed. Next, the composite formation water was mixed with different volumes of pure water and different volumes of ethylene glycol, and the conductivity of the mixed solutions with different ethylene glycol concentrations and composite formation water ratios was measured. The chloride content data and conductivity data were correlated to establish a quantitative characterization chart. During subsequent production testing, only the ethylene glycol concentration and conductivity of the production water sample need to be measured, and the chloride content of the production water sample can be determined by combining the quantitative characterization chart, thus quickly obtaining the chloride content of the production water sample and saving testing time and costs. Attached Figure Description

[0024] Figure 1 This is a flowchart of a rapid detection method for chloride content in production water of ultra-deepwater gas fields according to the present invention;

[0025] Figure 2 This invention provides a Cl-W relationship chart for a rapid detection method of chloride content in production water of ultra-deep water gas fields. The chart reflects the experimental relationship curve between chloride content in mixed water samples and the proportion of compound formation water.

[0026] Figure 3 This is a W-Meg-σ relationship chart of a rapid detection method for chloride content in production water of ultra-deep water gas fields according to the present invention. The chart reflects the functional relationship between the proportion of formation water and conductivity when the mixed solution has different ethylene glycol concentrations.

[0027] Figure 4 This is a quantitative characterization chart of a rapid detection method for chloride content in production water of ultra-deep water gas fields according to the present invention. The chart reflects the relationship between conductivity and chloride content of production water samples under different ethylene glycol concentrations. Detailed Implementation

[0028] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this patent. Some data in the drawings may be omitted to better illustrate this embodiment and do not represent actual test data. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0029] The technical solution of the present invention will be 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 chloride content in production water for ultra-deepwater gas fields includes the following steps:

[0032] Step 1: Take formation water from the gas reservoir where the target gas well is located for chemical analysis to obtain the chemical ionic composition of the formation water. Based on the chemical ionic composition, the formation water is compounded to obtain compound formation water.

[0033] Step 2: Mix the compounded formation water with pure water to prepare multiple mixed water samples with different proportions of compounded formation water. Detect the chloride content of each mixed water sample and establish a functional relationship between the chloride content of the mixed water sample and the proportion of compounded formation water to obtain the first relationship.

[0034] Step 3: Repeat the same method of preparing multiple mixed water samples as in Step 2. Mix each mixed water sample with different volumes of ethylene glycol to prepare mixed solutions with different proportions of formation water at different ethylene glycol concentrations. Measure the conductivity of the mixed solutions to obtain the functional relationship between the proportion of formation water and the conductivity of the mixed solutions at different ethylene glycol concentrations, thus obtaining the second relationship.

[0035] Step 4: Combine the first and second equations 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, production water samples are obtained from the target ultra-deep water gas field. Data such as the ethylene glycol concentration and conductivity of the production water samples are obtained. The data are compared with quantitative characterization charts to determine the chloride content of the production water samples.

[0037] In existing technologies, obtaining production water samples requires first testing the ethylene glycol concentration and then detecting the chloride content. This process is lengthy, slow, and prone to errors. This method directly utilizes formation water from the gas reservoir where the target gas well is located, mixes it with pure water to obtain multiple mixed water samples, and tests the chloride content of each sample. Then, identical mixed water samples are prepared, and different volumes of ethylene glycol are added to each to obtain multiple mixed solutions. The conductivity of each mixed solution is then measured. When testing production water samples, only the ethylene glycol concentration and conductivity of the production water sample need to be measured. By comparing the ethylene glycol concentration and conductivity data with the mixed solution data, the corresponding mixed solution data can be obtained. This mixed solution data includes the ratio of mixed formation water to pure water, allowing the identification of mixed water samples with the same ratio and thus obtaining the required data. The chloride content data of the mixed water sample is obtained; that is, mixed water samples with different proportions of formation water have different chloride content data. This chloride content data serves as a standard reference value for subsequent production testing. Mixed water samples with different proportions of formation water also correspond to mixed solutions with different ethylene glycol contents. Each mixed solution has corresponding ethylene glycol concentration and conductivity data. During subsequent production, the corresponding mixed solution is found by using the ethylene glycol concentration and conductivity data of the production water sample, and then the corresponding mixed water sample is found, and finally 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] In this process, mixed water samples are used to reproduce the actual production process of the gas field, from producing only condensate water (distilled water) to producing both condensate water and formation water, thereby simulating the ionic composition of the actual production water in the gas field. Mixed solutions with different ethylene glycol concentrations are used to simulate the gas field production water at the plug flow trap on the offshore platform of the ultra-deepwater gas field. In step four, the functional relationship between chloride content and conductivity at different ethylene glycol concentrations is obtained, that is, the chloride content of the mixed solution of ethylene glycol, mixed formation water, and distilled water after deducting the volume of ethylene glycol is obtained, which yields the simulated chloride content of the ethylene glycol-rich gas field production water, such as... Figure 4 As shown, the actual chloride content of the production water sample is then confirmed by comparing the actual production data with the quantitative characterization chart.

[0039] Specifically, for each set ethylene glycol concentration, mixed water samples with different proportions of formation water were prepared. The detection data of the mixed solutions could be grouped according to the ethylene glycol concentration. Further, in step three, the same volume of ethylene glycol was first mixed with mixed water samples with different proportions of formation water to obtain mixed solutions, resulting in mixed solutions of the same concentration but different proportions of formation water. Then, mixed solutions of different concentrations but different proportions of formation water were prepared separately.

[0040] The beneficial effects of this embodiment are as follows: By compounding real gas reservoir formation water, compounded formation water is obtained. This compounded formation water is then used as a base sample, mixed with different volumes of pure water, and analyzed to obtain chloride content data for the mixed water samples with different proportions of compounded formation water. Furthermore, the compounded formation water is mixed with different volumes of pure water and different volumes of ethylene glycol, and the conductivity data of the mixed solutions with different ethylene glycol concentrations and different proportions of compounded formation water are measured. By correlating the chloride content data and conductivity data, a quantitative characterization chart is established. During subsequent production testing, only the ethylene glycol concentration and conductivity of the production water sample need to be measured, and the chloride content of the production water sample can be determined by combining the quantitative characterization chart, thus quickly obtaining the chloride content of the production water sample and saving testing time and costs.

[0041] Example 2

[0042] The difference between Example 1 and Example 2 is as follows:

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

[0044] Furthermore, in step three, the proportion of formation water in the mixed water sample is defined as W. Define the ethylene glycol concentration as Meg. The conductivity of the mixture is defined as σ. The conductivity of the mixture is measured to obtain the functional relationship curves between the proportion of formation water and the conductivity of the mixture at different ethylene glycol concentrations. The second relationship W = g(σ,Meg) is then established.

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

[0046] Furthermore, such as Figure 2 As shown, in step two, a Cl-W relationship chart is established based on the relationship curves between the proportion of formation water (W) and the chloride content (Cl) at different formations. Establishing this chart facilitates data comparison and provides a more intuitive representation of the data relationships.

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

[0048] The remaining features and working principles of this embodiment are the same as those of Embodiment 1.

[0049] Example 3

[0050] Based on Example 1 or Example 2, Example 1 or Example 2 are further defined, with the following differences:

[0051] In step two, the chloride content of the mixed water sample is determined by silver nitrate titration. While the chloride content is detected using the commonly used silver nitrate titration method, this chloride detection step is part of the pre-production preparation and will not affect the detection speed during production.

[0052] Furthermore, in step two, the prepared mixed water samples are grouped. One group is used for chloride content detection in step two, and the other group is used for conductivity measurement in step three. Preparing more mixed water samples at a time and then grouping them further, with different groups of mixed solutions used for different operations, maintains the consistency of the mixed solutions and improves data accuracy.

[0053] Furthermore, in steps two and three, distilled water is used. Distilled water is easy to prepare and has low preparation costs.

[0054] Furthermore, in step five, production water samples are obtained from the plug flow trap in the target ultra-deep water gas field section.

[0055] The remaining working principles and processes of this embodiment are the same as those of Embodiment 1 or Embodiment 2.

[0056] In the specific implementation of the above embodiments, the technical features can be combined in any non-contradictory way. For the sake of brevity, not all possible combinations of the above technical features are described. However, as long as the combination of these technical features is not contradictory, it 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 implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A rapid detection method for chloride content in production water of ultra-deep water gas fields, characterized in that, Includes the following steps: Step 1: Take formation water from the gas reservoir where the target gas well is located for chemical analysis to obtain the chemical ionic composition of the formation water. Based on the chemical ionic composition, the formation water is compounded to obtain compound formation water. Step 2: Mix the compounded formation water with pure water to prepare multiple mixed water samples with different proportions of compounded formation water. Detect the chloride content of each mixed water sample and establish a functional relationship between the chloride content of the mixed water sample and the proportion of compounded formation water to obtain the first relationship. Step 3: Repeat the same method of preparing multiple mixed water samples as in Step 2. Mix each mixed water sample with different volumes of ethylene glycol to prepare mixed solutions with different proportions of formation water at different ethylene glycol concentrations. Measure the conductivity of the mixed solutions to obtain the functional relationship between the proportion of formation water and the conductivity of the mixed solutions at different ethylene glycol concentrations, thus obtaining the second relationship. Step 4: Combine the first and second equations 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, production water samples are obtained from the target ultra-deep water gas field. The ethylene glycol concentration and conductivity data of the production water samples are detected and compared with quantitative characterization charts to determine the chloride content of the production water samples.

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

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

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

5. A rapid detection method for chloride content in production water of ultra-deep water gas fields according to claim 2, characterized in that: In step two, a Cl-W relationship chart is established based on the relationship curves between the proportion of formation water (W) and the chloride content (Cl) at different formations.

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

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

8. A rapid detection method for chloride content in production water of ultra-deep water gas fields according to claim 1, characterized in that: In step two, the prepared mixed water samples are divided into groups: one group is used for chloride content detection in step two, and the other group is used for conductivity measurement in step three.

9. A rapid detection method for chloride content in production water of ultra-deep water gas fields according to claim 1, characterized in that: In steps two and three, distilled water is used.

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

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