Rapid analysis method for oil field water

Abstract

The invention relates to the technical field of oil reservoir engineering, in particular to an oil field water rapid analysis method which comprises the steps that a sodium ion-chloride ion calculation regression equation is established according to the chloride ion content and the sodium ion content in well logging layer oil field water in a target area; establishing a mineralization degree-chloride ion calculation regression equation according to the chloride ion content and the mineralization degree value in the well logging layer oil field water in the target area; the content of chloride ions in the oil field water of the to-be-measured well layer in the target area is obtained, and the content of sodium ions and the salinity of the oil field water of the to-be-measured well layer are obtained based on the sodium ion-chloride ion calculation regression equation and the salinity-chloride ion calculation regression equation. According to the method, the oil field water total analysis process is simplified, time and labor are saved, analysis data are reliable, an existing oil field water analysis method can be replaced or supplemented, and the method can be applied to oil field development and production practice.

Description

Technical Field

[0001] The invention relates to the technical field of oil reservoir engineering and is a rapid analysis method for oil field water. Background Art

[0002] At present, there are 8 ions in the full analysis of oilfield water, except for the alkali metal Na + and K + ions are calculated by ion balance, and the other four anions (Cl - 、HCO3 - 、CO4 2- 、SO4 2- ) and two cations (Ca 2+ Mg 2+ ) Different methods need to be used to determine the content of each ion separately, and then the mineralization degree (TDS) of water can be calculated and the type of water can be determined according to the Sulin classification index. In other words, to determine the mineralization degree and water type of water, it is necessary to measure 8 ions separately. The results of the full analysis of oilfield water play an important role in exploration (oil and gas migration, accumulation and preservation), development (water flooding, water string, selection of salt-sensitive plugging agents, etc.) and engineering (interlayer channeling and pipe channeling, etc.), so it is an indispensable test and analysis data. The semi-analysis of oilfield water only analyzes the density, pH value and chloride ion concentration of water. Semi-analysis is simple and easy to perform, and can be performed at the oil field site or remote well area, but its scope of application is limited; the full analysis of oilfield water mainly analyzes 6 ions in water and determines the mineralization degree and type of water from them. The full analysis of oilfield water has a long cycle, cumbersome procedures and many types of instruments and equipment. The neutralization point is difficult to determine using the titration method in the analysis, and there are many steps in chromatographic or spectral analysis, which requires high skills of analysts and is time-consuming and laborious.

[0003] Therefore, it is urgent to establish a quick method to make full use of the existing oilfield water analysis data. On the one hand, it can expand the application scope of oilfield water semi-analysis, and on the other hand, it can simplify the oilfield water full analysis process, so as to save time and labor, and achieve reliable and high-precision analysis data, completely or partially replace the existing oilfield water analysis methods or supplement the shortcomings of the existing oilfield water analysis methods. Summary of the invention

[0004] The present invention provides a rapid analysis method for oilfield water, which overcomes the deficiencies of the above-mentioned prior art and can effectively solve the problems of the limitations of the existing semi-analysis of oilfield water, the long full analysis cycle, and the complicated procedures.

[0005] The technical solution of the present invention is achieved by the following measures: A method for rapid analysis of oilfield water, comprising the following steps: According to the chloride ion content and sodium ion content in the oil field water of the logged well layer in the target area, a sodium ion-chloride ion calculation regression equation is established; According to the chloride ion content and salinity value of the oilfield water in the logged well layer in the target area, a salinity-chloride ion calculation regression equation is established; The chloride ion content of the oilfield water in the target area is obtained, and the sodium ion content and the salinity value of the oilfield water in the target area are obtained based on the sodium ion-chloride ion calculation regression equation and the salinity-chloride ion calculation regression equation.

[0006] The following are further optimizations and / or improvements to the above technical solutions: The above-mentioned oilfield water rapid analysis method also includes: According to the sodium chloride ion milligram equivalent concentration ratio of the oil field water in the well layer to be tested , determine the water type of the oilfield water in the well layer to be tested.

[0007] The above sodium ion-chloride ion calculation regression equation is established based on the chloride ion content and sodium ion content in the oil field water of the well layer in the target area, including: Taking sodium ion content as the dependent variable and chloride ion content as the independent variable, a linear regression was performed on the sodium ion content and chloride ion content in the oil field water of the logged well layer to obtain the sodium ion-chloride ion calculation regression equation; The expression of the regression equation for sodium ion-chloride ion calculation is: In the formula, is the sodium ion content in oilfield water, mg / l; Chloride ion content in oilfield water, mg / l; and is the coefficient.

[0008] According to the chloride ion content and salinity value of the oilfield water in the target area, the salinity-chloride ion calculation regression equation is established, including: With the salinity value as the dependent variable and the chloride ion content as the independent variable, a linear regression is performed on the salinity value and the chloride ion content of the oil field water in the logged well layer to obtain the salinity-chloride ion calculation regression equation; The expression of the regression equation for mineralization-chloride ion calculation is: In the formula, is the mineralization of oilfield water, mg / l; Chloride ion content in oilfield water, mg / l; and is the coefficient.

[0009] The above sodium chloride ion milligram equivalent concentration is Calculated as follows: In the formula, is the sodium ion content in oilfield water, mg / l; Chloride ion content in oilfield water, mg / l.

[0010] The above is based on the sodium chloride ion milligram equivalent concentration ratio of the oil field water in the well layer to be tested. Confirm the water type of the well layer to be tested, including: Sodium chloride milligram equivalent concentration ratio >1, determine whether the oilfield water type is NaHCO3 water type or Na2SO4 water type; Sodium chloride milligram equivalent concentration ratio 1. Determine whether the oilfield water type is CaCl2 water type or MgCl2 water type.

[0011] The above-mentioned oilfield water rapid analysis method also includes: When the water type of the oilfield water in the target area is CaCl2 water type, a regression equation for calculating the difference between calcium ion content, chloride ion content and sodium ion content is established according to the difference between calcium ion content and chloride ion content and sodium ion content in the oilfield water of the well layer in the target area; The chloride ion content of the oilfield water in the well layer to be measured in the target area is obtained, and the regression equation is calculated based on the difference between the calcium ion-chloride ion and sodium ion content to obtain the calcium ion content of the oilfield water in the well layer to be measured.

[0012] According to the calcium ion content and the difference between the chloride ion and sodium ion content in the oil field water of the well layer in the target area, the regression equation for calculating the difference between the calcium ion, chloride ion and sodium ion content is established, including: With calcium ion content as the dependent variable and the difference between chloride ion and sodium ion content as the independent variable, a linear regression was performed on the calcium ion content and the difference between chloride ion and sodium ion content in the logged well layer oil field water to obtain the regression equation for calculating the difference between calcium ion, chloride ion and sodium ion content; The regression equation for calculating the difference between calcium ion, chloride ion and sodium ion content is as follows: In the formula, is the calcium ion content of oilfield water, mg / l; The difference between the chloride ion content and the sodium ion content in oilfield water, mg / l; and is the coefficient.

[0013] The present invention provides an oilfield water analysis method, which utilizes the chloride ion content in the oilfield water and applies a regression equation to calculate the mineralization degree and the content of major ions in the oilfield water, further determines the type of the oilfield water, simplifies the entire analysis process of the oilfield water, saves time and labor, and the analysis data is reliable. The method can replace or supplement the existing oilfield water analysis method and can be applied to the actual development and production of oilfields. DETAILED DESCRIPTION

[0014] The present invention is not limited by the following embodiments, and specific implementation methods can be determined based on the technical solution of the present invention and actual conditions.

[0015] The present invention will be further described below in conjunction with embodiments: Example 1: The oilfield water rapid analysis method is carried out according to the following steps: One of the technical solutions of the present invention is achieved by the following measures: A method for rapid analysis of oilfield water, comprising the following steps: According to the chloride ion content and sodium ion content in the oil field water of the logged well layer in the target area, a sodium ion-chloride ion calculation regression equation is established; According to the chloride ion content and salinity value of the oilfield water in the logged well layer in the target area, a salinity-chloride ion calculation regression equation is established; The chloride ion content of the oilfield water in the target area is obtained, and the sodium ion content and mineralization of the oilfield water in the target area are obtained based on the sodium ion-chloride ion calculation regression equation and the mineralization-chloride ion calculation regression equation.

[0016] The monovalent cations in oilfield water mainly include sodium ions and potassium ions. Generally, the potassium ion content is much lower than the sodium ion content. In actual production applications, the sodium ion content usually covers the sum of the sodium ion and potassium ion contents. Therefore, in the present invention, the sodium ion content refers to the sum of the sodium ion and potassium ion contents.

[0017] Embodiment 2: As an optimization of the above embodiment, the oilfield water rapid analysis method further includes: According to the sodium chloride ion milligram equivalent concentration ratio of the oil field water in the well layer to be tested , determine the water type of the oilfield water in the well layer to be tested.

[0018] Embodiment 3: As an optimization of the above embodiment, according to the chloride ion content and sodium ion content of the oil field water in the well layer in the target area, a sodium ion-chloride ion calculation regression equation is established, including: Taking sodium ion content as the dependent variable and chloride ion content as the independent variable, a linear regression was performed on the sodium ion content and chloride ion content in the oil field water of the logged well layer to obtain the sodium ion-chloride ion calculation regression equation; The expression of the regression equation for sodium ion-chloride ion calculation is: In the formula, is the sodium ion content in oilfield water, mg / l; Chloride ion content in oilfield water, mg / l; and is the coefficient.

[0019] Embodiment 4: As an optimization of the above embodiment, according to the chloride ion content and salinity value of the oil field water in the well layer in the target area, a salinity-chloride ion calculation regression equation is established, including: With the salinity value as the dependent variable and the chloride ion content as the independent variable, a linear regression is performed on the salinity value and the chloride ion content of the oil field water in the logged well layer to obtain the salinity-chloride ion calculation regression equation; The expression of the regression equation for mineralization-chloride ion calculation is: In the formula, is the mineralization of oilfield water, mg / l; Chloride ion content in oilfield water, mg / l; and is the coefficient.

[0020] Example 5: As an optimization of the above example, the sodium chloride ion milligram equivalent concentration is Calculated as follows: In the formula, is the sodium ion content in oilfield water, mg / l; Chloride ion content in oilfield water, mg / l.

[0021] Example 6: As an optimization of the above example, according to the sodium chloride ion milligram equivalent concentration ratio of the oil field water in the well layer to be measured Confirm the water type of the well layer to be tested, including: Sodium chloride milligram equivalent concentration ratio >1, determine whether the oilfield water type is NaHCO3 water type or Na2SO4 water type; Sodium chloride milligram equivalent concentration ratio 1. Determine whether the oilfield water type is CaCl2 water type or MgCl2 water type.

[0022] In specific applications, if the sodium chloride ion milligram equivalent concentration is >1, confirm that the oilfield water type is NaHCO3 water type or Na2SO4 water type; further confirmation of the water type can be determined based on the salinity value. Generally, the NaHCO3 type has a higher salinity than the Na2SO4 type, and the two types of water can be distinguished based on the salinity of the water in the oilfield area. 1, then the water type of the oilfield water is confirmed to be CaCl2 water type or MgCl2 water type. Similarly, the water type can be further confirmed based on the salinity value. Generally, the salinity of CaCl2 water type is lower than that of MgCl2 water type.

[0023] Embodiment 7: As an optimization of the above embodiment, the oilfield water rapid analysis method further includes: When the water type of the oilfield water in the target area is CaCl2 water type, a regression equation for calculating the difference between calcium ion content, chloride ion content and sodium ion content is established according to the difference between calcium ion content and chloride ion content and sodium ion content in the oilfield water of the well layer in the target area; The chloride ion content of the oilfield water in the well layer to be measured in the target area is obtained, and the regression equation is calculated based on the difference between the calcium ion-chloride ion and sodium ion content to obtain the calcium ion content of the oilfield water in the well layer to be measured.

[0024] Embodiment 8: As an optimization of the above embodiment, according to the calcium ion content and the difference between the chloride ion and sodium ion content in the oil field water of the well layer in the target area, a regression equation for calculating the difference between the calcium ion, chloride ion and sodium ion content is established, including: With calcium ion content as the dependent variable and the difference between chloride ion and sodium ion content as the independent variable, a linear regression was performed on the calcium ion content and the difference between chloride ion and sodium ion content in the logged well layer oil field water to obtain the regression equation for calculating the difference between calcium ion, chloride ion and sodium ion content; The regression equation for calculating the difference between calcium ion, chloride ion and sodium ion content is as follows: In the formula, is the calcium ion content of oilfield water, mg / l; The difference between the chloride ion content and the sodium ion content in oilfield water, mg / l; and is the coefficient.

[0025] It should be noted that the well layer to be measured and the well layer to be measured in the present invention should belong to the same oil reservoir or the same layer or the same regional oil reservoir oil layer water, and the oil field water polluted by various operations of the oil well or the outlier analysis data points should be excluded from the data regression processing. The chloride ion content of the oil field water sample of the well layer to be measured should be within the range of the independent variable value of the regressed equation, that is, the interpolation method is used for evaluation. The interpolation prediction result is often reliable and has high accuracy, but if the independent variable chloride ion content is outside the range of the independent variable value, the prediction result may be unreliable when the regression equation is extrapolated. The mineralization value of oil field water has a certain range for specific oil fields and reservoirs; the pH value of oil field water is different from that of surface water, and there are many influencing factors, among which the main influencing factor is the organic acid contained in the oil field water, so the range of mineralization and pH value should be determined according to regional experience.

[0026] Su Lin compared the composition of terrestrial water and seawater and their formation mechanism. Based on the milligram equivalent ratio of sodium ions and chloride ions, and in accordance with the chemical reaction law that the anions and cations with greater affinity combine first, he divided water into four types: CaCl2 type, NaHCO3 type, NaSO4 type and MaCl2 type. CaCl2 water type accounts for the vast majority of the entire oilfield water type and is widely distributed in the oilfield water of various oil and gas basins in the world and China. The second is NaHCO3 water type, and NaSO4 water type and MgCl2 water type are rare. Regardless of the water type, it mainly contains the following ions: Cations are: Na + , Ca 2+ Mg 2+ ; Anions: Cl - 、HCO3 - 、CO3 2- and SO4 2- , where Na + It has an absolute advantage in the cation content, reaching more than 90%, followed by Ca + , the content is less than 10%; among the anions, Cl - It also accounts for an absolute amount, which can reach more than 90%. Secondly, for different water types, HCO3 2- or SO4 2- Ions account for less than 10%. There are certain internal rules among the ion content, mineralization and Sulin water type in oilfield water: Na + With Cl - They have an absolute advantage in the content of cations and anions, reaching more than 90% respectively, and the content of other ions is less than 10% or even less. At the same time, the mineralization of water can almost be applied to Cl - Therefore, the main ion that determines the mineralization of water is Na + and Cl - ; The primary factor that determines the water type is Na + With Cl - The ratio of milligram equivalent concentration is the main factor affecting the water mineralization (TDS), followed by the amount of calcium ions and sulfate ions. - and Na - The proportion of other ions in the mineralization is very small. + and Cl - There is a close relationship between the mineralization and chloride ion content, showing a strong positive correlation. Therefore, no matter what type of water, the Cl -Ion content, the mineralization of water and the type of water are calculated based on the established correlation equation. It is particularly noted that for some calcium chloride water types, there is a strong correlation between the calcium ion content and the difference between the chloride ion content and the sodium ion content. In practical applications, when the correlation goodness of fit between the calcium ion content and the difference between the chloride ion content and the sodium ion content reaches 0.9 or above, a regression equation of the two is established to calculate the calcium ion content. Therefore, there is no need to measure other ions with low content in the water, so as to simplify the water analysis process and complete the conversion of semi-analysis results into full analysis results. The present invention provides a rapid analysis method for oilfield water based on the above rules, which only analyzes Cl in water. - The mineralization degree, sodium ion content or calcium ion content of oilfield water can be obtained by applying the regression equation, and then combined with the sodium chloride ion milligram equivalent concentration ratio The method simplifies the full analysis process, or can convert the semi-analysis results into full water analysis results, and at the same time, it can also complete the full water analysis on-site or in remote areas.

[0027] Example 9: The specific process of the oilfield water rapid analysis method is as follows: Collect and study the full analysis data of formation water in the wells in the oil field area, pay special attention to the sampling location, layer, and sampling time, combine the existing geological reservoir data, and preliminarily screen the regression data according to the pH value, mineralization, and water type of water analysis, and exclude non-reservoir, non-layer, and contaminated sample analysis data from the regression data. Water sampling in exploration wells and evaluation wells is often contaminated by drilling fluids, so it is best to measure its pH value or chloride ion content in time during on-site sampling, or roughly determine the mud contaminated formation fluid after the fluid is drained; for wells put into production by fracturing and acidizing, take water samples after estimating the complete return of fracturing fluid acid. Secondly, the correlation of the regression equation is improved by excluding outliers and abnormal points through scatter plots and eliminating abnormal residuals, so that its goodness of fit reaches above 0.9. Finally, the chloride ion content of the water sample is determined, and the established regression equation is used to predict the mineralization, sodium ion, or calcium ion of the water sample. If the relative error of the predicted value is within 10%, the prediction is considered feasible. If it is not within this range, redefine the regression sample, or increase the sample size, or use the method of eliminating abnormal residuals to clean the sample data and eliminate unrepresentative water sample data.

[0028] In this embodiment, the regression equations of sodium ion-chloride ion, mineralization-chloride ion and calcium ion-chloride ion and sodium ion content difference were calculated for different formation water in different oil fields (layers) in the study area, and the goodness of fit (R 2 ) and mean absolute percentage error (MAPE) are used as effective indicators to measure the goodness of fit of the regression equation and the prediction accuracy.

[0029] (1) Study area A: Based on the existing data, it was preliminarily determined that the water type was CaCl2 water type, and the TDS in the area was 107121 mg / l to 391744 mg / l.

[0030] The regression equations for calculating sodium ion-chloride ion, mineralization-chloride ion, and calcium ion-chloride ion and sodium ion content difference are established as follows: , R 2 =0.9828, MAPE=9.10%.

[0031] , R 2 =0.9990, MAPE=0.96%.

[0032] , R 2 =0.9186, MAPE=6.09%.

[0033] (2) Study area B: Based on the existing data, the water type was preliminarily determined to be NaHCO3 water type, and the TDS in the area was 2854mg / l to 6156mg / l.

[0034] The regression equations for calculating sodium ion-chloride ion and mineralization-chloride ion were established as follows: , R 2 =0.9047, MAPE=5.72%.

[0035] , R 2 =0.9683, MAPE=3.35%.

[0036] (3) Study area C: Based on the existing data, the water type was preliminarily determined to be Na2SO4 water type, and the TDS in the area was 6300mg / l to 9726mg / l.

[0037] The regression equations for calculating sodium ion-chloride ion and mineralization-chloride ion were established as follows: , R 2 =0.9936, MAPE=1.92%.

[0038] , R 2 =0.9273, MAPE=3.2%.

[0039] The Cl content of formation water in the wells to be tested in the study area - The Cl content of the water sample was determined.- The content is put into the regression equation to obtain the mineralization and sodium ion content of the formation water in the well to be tested. Taking the formation water in the wells to be tested in the study area A, B, and C as an example, the Cl content in the formation water in the well to be tested is tested. - The content is substituted into the above regression equation to obtain the mineralization and sodium ion content of the oil layer water in the well to be tested, and compared with the measured mineralization and sodium ion content values. From the comparison results (see Table 1), it can be seen that the mineralization and sodium ion content calculated by the method of the present invention are close to the measured mineralization and sodium ion content values, with an error of less than 10%, which can fully meet the application of oil field. At the same time, the ratio of sodium ion content to the detected chloride ion content of the oil field water in the well to be tested is converted into a milligram equivalent concentration ratio. , and then according to The size of the oilfield water is further confirmed by combining the mineralization value of the oilfield area. The water type judgment results are shown in Table 1.

[0040] The regression equation was calculated based on the difference between the calcium ion, chloride ion and sodium ion contents in the study area A, and the calcium ion content of the well layer 1 to be measured in the study area A was calculated and compared with the measured value. The results are shown in Table 2.

[0041] It can be seen from the application results in Table 1 and Table 2 that the results obtained by the rapid analysis method for oilfield water of the present invention are close to the measured values, with an error of less than 10%, which can fully meet the application requirements of oilfield sites.

[0042] In summary, the present invention provides a rapid analysis method for oilfield water, which utilizes the chloride ion content in the oilfield water and applies a regression equation to calculate the mineralization degree and the content of major ions in the oilfield water, further determines the type of the oilfield water, simplifies the full analysis process of the oilfield water, converts the semi-analysis results into the full analysis results of the oilfield water, and simultaneously realizes the rapid analysis of the oilfield water on-site or in remote areas, and simplifies the full water analysis process.

[0043] The above technical features respectively constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different actual situations.

Claims

1. A rapid analysis method for oilfield water, characterized in that The following steps are involved: According to the chloride ion content and sodium ion content in the oil field water of the logged well layer in the target area, a sodium ion-chloride ion calculation regression equation is established; According to the chloride ion content and salinity value of the oil field water in the logged layer in the target area, a salinity-chloride ion calculation regression equation is established; The chloride ion content of the oilfield water in the target area is obtained, and the sodium ion content and mineralization of the oilfield water in the target area are obtained based on the sodium ion-chloride ion calculation regression equation and the mineralization-chloride ion calculation regression equation.

2. The method for rapid analysis of oilfield water according to claim 1, characterized in that Also includes: According to the sodium chloride ion milligram equivalent concentration ratio of the oil field water in the well layer to be tested , determine the water type of the oilfield water in the well layer to be tested.

3. The oilfield water rapid analysis method according to claim 1 or 2, characterized in that According to the chloride ion content and sodium ion content in the oilfield water of the logged well layer in the target area, a sodium ion-chloride ion calculation regression equation is established, including: Taking sodium ion content as the dependent variable and chloride ion content as the independent variable, a linear regression was performed on the sodium ion content and chloride ion content in the oil field water of the logged well layer to obtain the sodium ion-chloride ion calculation regression equation; The expression of the regression equation for sodium ion-chloride ion calculation is: In the formula, is the sodium ion content in oilfield water, mg / l; Chloride ion content in oilfield water, mg / l; and is the coefficient.

4. The method for rapid analysis of oilfield water according to any one of claims 1 to 3, characterized in that According to the chloride ion content and salinity value of the oilfield water in the well layer in the target area, the salinity-chloride ion calculation regression equation is established, including: With the salinity value as the dependent variable and the chloride ion content as the independent variable, a linear regression is performed on the salinity value and the chloride ion content of the oil field water in the logged well layer to obtain the salinity-chloride ion calculation regression equation; The expression of the regression equation for mineralization-chloride ion calculation is: In the formula, is the mineralization of oilfield water, mg / l; Chloride ion content in oilfield water, mg / l; and is the coefficient.

5. The method for rapid analysis of oilfield water according to claim 2, characterized in that Sodium chloride milligram equivalent concentration ratio Calculated as follows: In the formula, is the sodium ion content in oilfield water, mg / l; Chloride ion content in oilfield water, mg / l.

6. The method for rapid analysis of oilfield water according to claim 5, characterized in that According to the sodium chloride ion milligram equivalent concentration ratio of the oil field water in the well layer to be tested Confirm the water type of the well layer to be tested, including: Sodium chloride milligram equivalent concentration ratio >1, determine whether the oilfield water type is NaHCO3 water type or Na2SO4 water type; Sodium chloride milligram equivalent concentration ratio 1. Determine whether the oilfield water type is CaCl2 water type or MgCl2 water type.

7. The method for rapid analysis of oilfield water according to any one of claims 1 to 6, characterized in that Also includes: When the water type of the oilfield water in the target area is CaCl2 water type, a regression equation for calculating the difference between calcium ion content, chloride ion content and sodium ion content is established based on the difference between the calcium ion content and the chloride ion content and the sodium ion content in the oilfield water of the well layer in the target area; The chloride ion content of the oilfield water in the well layer to be measured in the target area is obtained, and the regression equation is calculated based on the difference between the calcium ion-chloride ion and sodium ion content to obtain the calcium ion content of the oilfield water in the well layer to be measured.

8. The method for rapid analysis of oilfield water according to claim 7, characterized in that According to the calcium ion content and the difference between the chloride ion and sodium ion content in the oil field water of the logged well layer in the target area, a regression equation for calculating the difference between the calcium ion, chloride ion and sodium ion content is established, including: With calcium ion content as the dependent variable and the difference between chloride ion and sodium ion content as the independent variable, a linear regression was performed on the calcium ion content and the difference between chloride ion and sodium ion content in the logged well layer oil field water to obtain the regression equation for calculating the difference between calcium ion, chloride ion and sodium ion content; The regression equation for calculating the difference between calcium ion, chloride ion and sodium ion content is as follows: In the formula, is the calcium ion content of oilfield water, mg / l; The difference between the chloride ion content and the sodium ion content in oilfield water, mg / l; and is the coefficient.

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