Method for rapidly detecting metal ions contained in fracturing water

Abstract

The invention relates to the technical field of oil field water detection, in particular to a rapid detection method for metal ions contained in fracturing water, which comprises the following steps: measuring the total conductivity of a fracturing water sample at T1, T2 and T3 temperatures, continuously adding a precipitator NaOH into the fracturing water sample, measuring the turbidity value change of the fracturing water, and when the turbidity value is stable, determining the metal ions contained in the fracturing water. The turbid liquid for fracturing is obtained, the turbidity detection value NTU of the turbid liquid for fracturing and the use amount of a precipitant NaOH are recorded, and the conductivity of the turbid liquid for fracturing at the temperatures T1, T2 and T3 is measured at the same time; and obtaining the concentrations of Na < + >, K < + >, Ca < 2 + >, Mg < 2 + > and Ba < 2 + > in the water sample for fracturing according to the series of correlation equations. According to the invention, a fitting correlation equation set and a step-by-step rapid determination method are adopted, and the method has the advantages of rapid and accurate detection, low cost, environmental protection, no toxicity, simple operation, wide application range and the like.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield water detection, and is a method for quickly detecting metal ions contained in fracturing water. Background Art

[0002] Fracturing fluid is the working fluid used in fracturing oil and gas layers. Its main function is to transfer the high pressure formed by ground equipment to the formation, so that the formation breaks to form cracks and transport proppant along the cracks. It is a chemical system formed by a variety of additives, one of the main components of which is water. With the increase in the scale of oil field volume transformation and the increase in fracturing workload, the amount of water used for fracturing has increased year by year. In order to alleviate the water shortage, oil fields currently use multiple sources of water or recycling water for fracturing to solve the problem. However, the disadvantages of this method are that the water quality composition is complex and changeable, the water quality mineralization performance is poor, and it is easy to cause problems such as low swelling rate of the prepared liquid, large foam in the preparation process, and poor temperature and shear resistance of the gel, which has a great impact on the preparation and performance of the fracturing fluid. Among them, the concentration of metal ions contained in the fracturing water is one of the important factors affecting the performance of the fracturing fluid. Therefore, the rapid determination of the metal ion concentration of fracturing water on site in the oil field can timely understand the properties of the fracturing water and provide data support for technicians to adjust the fracturing fluid preparation process.

[0003] The types of metal ions contained in the water used for oilfield fracturing have the following characteristics: monovalent metal ions are mainly Na + , may contain a small amount of K + ; Divalent metal ions are Ca 2+ and Mg 2+ As the main body, there may be a small amount of Ba 2+ The concentrations of other monovalent metal ions and divalent metal ions are relatively low, and their impact on the actual production of the oil field can be ignored.

[0004] At present, the on-site detection of metal ion concentrations in fracturing water mainly relies on manual sampling and laboratory testing. The disadvantages of manual sampling and testing are slow sampling and monitoring speed, long measurement intervals, low work efficiency, high labor intensity, low data accuracy, and inability to timely grasp the changes in the quality of fracturing water and the performance of fracturing fluids. Laboratory testing can use precision instruments such as spectroscopy, chromatography, and conductivity methods for high-precision analysis, but its disadvantages are low timeliness and high testing costs. The on-site monitoring of fracturing water quality in oil fields has the following two characteristics: one is the requirement for real-time, rapid, and timely feedback on changes in metal ion concentrations, and the other is relatively low accuracy requirements. Therefore, in view of these two characteristics, it is necessary to develop a process method that can be used to quickly detect metal ions in fracturing water at oil fields. Summary of the invention

[0005] The present invention provides a method for quickly detecting metal ions contained in fracturing water, which overcomes the shortcomings of the above-mentioned prior art and can effectively solve the problems of slow detection speed of metal ion concentration contained in fracturing water, long measurement interval time, and inability to timely grasp the changes in water quality of fracturing water and fracturing fluid performance.

[0006] The technical solution of the present invention is achieved by the following measures: A method for rapid detection of metal ions contained in fracturing water is carried out according to the following steps: S1, respectively establish conductivity and Na + and K + Concentration correlation equations, turbidity values ​​and Ca 2+ Mg 2+ and Ba 2+ Concentration-related equations and conductivity and Ca 2+ Mg 2+ and Ba 2+ Concentration-related equations; S2, the total conductivity of the fracturing water sample at temperatures T1, T2 and T3 is measured and recorded as σ T ,σ' T and σ" T ; S3, continuously adding precipitant NaOH to the fracturing water sample of step S2, and measuring the change of turbidity value of the fracturing water, when the turbidity value is stable, obtaining turbid liquid for fracturing water, and recording the turbidity detection value NTU of the turbid liquid for fracturing water 测 and the dosage of the precipitant NaOH, and the conductivity of the turbid liquid used for fracturing water at temperatures T1, T2, and T3; S4, according to the conductivity and Na + and K + The concentration correlation equation group is used to calculate the Na content in the fracturing water sample. + and K + concentration; S5, based on conductivity and Ca 2+ Mg 2+ and Ba 2+ The concentration correlation equation group is used to calculate the Ca content in the fracturing water sample. 2+ Mg 2+ and Ba 2+ concentration; S6, the Ca in the fracturing water sample obtained in step S5 is 2+ Mg 2+ and Ba 2+ The concentration of Ca is brought into the turbidity value and Ca 2+ Mg 2 + and Ba 2+The concentration correlation equation group is used to obtain the total turbidity calculation value NTU of the turbid fluid used for fracturing water T , and the detection value NTU 测 By comparison, the Ca content of the fracturing water sample calculated in step S5 is determined. 2+ Mg 2+ and Ba 2+ The accuracy of the concentration.

[0007] The following are further optimizations and / or improvements to the above technical solutions: The sampling volume of the above-mentioned fracturing water samples is 1L to 20L. + The concentration range is 100.0mg / L to 50000.0mg / L, K + The concentration range is 100.0mg / L to 5000.0mg / L, Ca 2+ and Mg 2+ The concentration range of Ba 2+ The concentration range of Na in fracturing water samples is 10mg / L to 500.0mg / L. + , K + , Ca 2+ Mg 2+ and Ba 2+ The content of each other metal cation is not higher than 50 mg / L, and the total content of other metal cations is not higher than 300 mg / L.

[0008] In the above step S1, the conductivity and Na + and K + The concentration correlation equation group is carried out in the following steps: prepare a series of standard aqueous solutions of NaCl and KCl, use a conductivity meter to measure the conductivity of the series of standard aqueous solutions of NaCl and KCl at temperatures T1, T2 and T3, draw the concentration-conductivity curve of the standard aqueous solutions of NaCl and KCl at temperatures T1, T2 and T3, and fit to obtain a linear equation group 1. The expression of equation group 1 is as follows: σ (N+) =k 1(N+) ×C (N+) Formula 1-1 σ' (N+) =k1' (N+) ×C (N+) Formula 1-2 σ" (N+) =k1" (N+) ×C (N+) Formula 1-3 In the formula, N+ represents Na + or K + , C (N+) Indicates Na+ or K + The concentration of the aqueous solution, in mg / L; σ (N+) ,σ' (N+) and σ" (N+) Na + or K + The conductivity of the aqueous solution at T1, T2 and T3, in μs / cm; k 1(N+) 、k1' (N+) and k1" (N+) Na + or K + Conductivity coefficient at temperatures T1, T2 and T3, unitless.

[0009] In the above step S1, the turbidity value and Ca 2+ Mg 2+ and Ba 2+ The concentration correlation equation group is carried out according to the following steps: prepare a series of standard aqueous solutions of CaCl2, MgCl2 and BaCl2, add sufficient amount of precipitant NaOH to them respectively, measure the turbidity of the standard aqueous solutions of CaCl2, MgCl2 and BaCl2 after reacting with sufficient amount of precipitant at temperature T1, draw the curve of the change of CaCl2, MgCl2 and BaCl2 concentration with turbidity respectively, and fit to obtain linear equation group 2. The expression of equation group 2 is as follows: NTU (M2+) =A 1(M2+) ×C (M2+) Formula 2 Among them, M2+ is Ca 2+ Mg 2+ Or Ba 2+ ; C (M2+) Ca 2+ Mg 2+ Or Ba 2+ Concentration of aqueous solution, in mg / L; NTU (M2+) Ca 2+ Mg 2+ Or Ba 2+ The turbidity of the aqueous solution after reacting with the precipitant NaOH, the unit is NTU; A 1(M2+) is the turbidity coefficient and has no unit.

[0010] In the above step S1, the conductivity and Ca 2+ Mg 2+ and Ba 2+The concentration correlation equation group is carried out in the following steps: the conductivity of the aqueous solution of the CaCl2, MgCl2 and BaCl2 series standard samples at temperatures T1, T2 and T3 is measured, the curve of the conductivity changing with the ion concentration at temperatures T1, T2 and T3 is plotted, and the linear equation group 3 is obtained by fitting. The expression of equation group 3 is as follows: σ (M2+) =k 2(M2+) ×C (M2+) Formula 3-1 σ' (M2+) =k2' (M2+) ×C (M2+) Formula 3-2 σ" (M2+) =k2" (M2+) ×C (M2+) Formula 3-3 In the formula, M2+ is Ca 2+ Mg 2+ Or Ba 2+ ; C (M2+) Ca 2+ Mg 2+ Or Ba 2+ The concentration of the aqueous solution, in mg / L; σ (M2+) ,σ' (M2+) and σ" (M2+) Ca 2+ Mg 2+ Or Ba 2+ The conductivity of the aqueous solution at T1, T2 and T3, in μs / cm; k 2(M2+) 、k2' (M2+) and k2" (M2+) Ca 2+ Mg 2+ Or Ba 2+ Conductivity coefficient at temperatures T1, T2 and T3, unitless.

[0011] The specific operation of the above step S4 is: according to the conductivity and Na + and K + The concentration correlation equation group converts the amount of precipitant NaOH into the Na added to the turbid liquid for fracturing water. + The concentration of Na in the fracturing water sample was calculated by establishing the following equation group 4: + and K + The concentration of , the expression of equation group 4 is as follows: σ1=k 1(Na+) C 1(Na+) + k 1 (K+) C (K+) Formula 4-1 σ'1=k' 1(Na+)C 1(Na+) + k' 1(K+) C (K+) Formula 4-2 σ"1=k" 1(Na+) C 1(Na+) + k" 1(K+) C (K+) Formula 4-3 C (Na+)= C 1(Na+) - C 2(Na+) Formula 4-4 In the formula, C 1(Na+) , C 1(K+) are respectively Na in the turbid liquid used for fracturing + and K + The concentration, C 2(Na+) The Na added to the turbid liquid for fracturing due to the addition of precipitant NaOH + Concentration, C (Na+) is the Na in the fracturing water sample + concentration, σ1, σ'1 and σ"1 are the conductivity of the turbid fluid for fracturing water at temperatures T1, T2 and T3, respectively, 1(Na+) 、k1' (Na+) and k1" (Na+) are Na in equation 1 at temperatures T1, T2 and T3 respectively. + The conductivity coefficient, k 1(K+) 、k1' (K+) and k1" (K+) are K in equation 1 at temperatures T1, T2 and T3 respectively. + The conductivity coefficient.

[0012] The specific operation of the above step S5 is: according to the conductivity and Na + and K + The concentration correlation equations, combined with the Na added by the precipitant NaOH + concentration, the following equation group 5 was established, and the Ca content in the fracturing water sample was calculated. 2+ Mg 2+ and Ba 2+ The concentration of , the expression of equation group 5 is: σ2= Formula 5-1 σ'2= Formula 5-2 σ"2= Formula 5-3 σ2=σ T -σ1+k 1(Na+) C 2(Na+) Formula 5-4 σ'2=σ' T -σ'1+k'1(Na+) C 2(Na+) Formula 5-5 σ"2=σ" T -σ"1+k" 1(Na+) C 2(Na+) Formula 5-6 Where σ2, σ'2 and σ"2 are the changes in conductivity of the turbid fluid used for fracturing at temperatures T1, T2 and T3 respectively; C 2(Na+) is the increase in Na due to the addition of precipitant NaOH + Concentration; C (M2+) is the Ca in the fracturing water sample 2+ Mg 2+ Or Ba 2+ concentration; σ1, σ'1 and σ"1 are the conductivity of the turbid fluid for fracturing water at temperatures T1, T2 and T3 respectively; k 1(Na+) 、k1' (Na+) and k1" (Na+) are respectively Na in equation 1 + The corresponding conductivity coefficient, k 2(M2+) 、k2' (M2+) and k2" (M2+) are Ca in equation 3 2+ Mg 2+ Or Ba 2+ The conductivity coefficient.

[0013] In the above step S6, if |NTU T -NTU 测 |≤10.0, then the Ca content of the fracturing water sample calculated in step S5 is 2+ Mg 2+ and Ba 2+ The concentration is accurate, among which the total turbidity calculation value of the turbid fluid used for fracturing water is NTU T According to formula 6, NTU T = Formula 6 In the formula, C (M2+) is the Ca content in the fracturing water sample 2+ Mg 2+ Or Ba 2+ The concentration is in mg / L, A 1(M2+) Ca 2+ Mg 2+ Or Ba 2+ The corresponding turbidity coefficient in equation 2.

[0014] In the above step S3, while adding the precipitant NaOH to the fracturing water sample, the fracturing water sample is stirred at a stirring speed of 100 rpm to 1000 rpm and a stirring time of 1 min to 5 min.

[0015] The above temperatures T1, T2 and T3 are all between 0 and 90°C, T1<T 2＜ T3 and the intervals between T1 and T2, T2 and T3 are 10°C to 20°C.

[0016] The present invention adopts a method of fitting correlation equations and rapid step-by-step determination to accurately obtain the Na content in fracturing water. + , K + , Ca 2+ Mg 2+ and Ba 2+ Compared with traditional methods, this method has the advantages of fast and accurate detection, low cost, environmental protection and non-toxicity, simple operation and wide application range. DETAILED DESCRIPTION

[0017] The present invention is not limited by the following embodiments, and the specific implementation method can be determined according to the technical scheme of the present invention and the actual situation. Unless otherwise specified, the various chemical reagents and chemicals mentioned in the present invention are all chemical reagents and chemicals known and used in the prior art; unless otherwise specified, the percentages in the present invention are all mass percentages; unless otherwise specified, the solutions in the present invention are all aqueous solutions with water as the solvent, for example, hydrochloric acid solution is a hydrochloric acid aqueous solution; the normal temperature and room temperature in the present invention generally refer to a temperature of 15°C to 25°C, and are generally defined as 25°C.

[0018] The present invention will be further described below in conjunction with embodiments: Example 1: The method for rapid detection of metal ions contained in fracturing water is carried out according to the following steps: S1, respectively establish conductivity and Na + and K + Concentration correlation equations, turbidity values ​​and Ca 2+ Mg 2+ and Ba 2+ Concentration-related equations and conductivity and Ca 2+ Mg 2+ and Ba 2+ Concentration-related equations; S2, the total conductivity of the fracturing water sample at temperatures T1, T2 and T3 is measured and recorded as σ T ,σ' T and σ" T ; S3, continuously adding precipitant NaOH to the fracturing water sample of step S2, and measuring the change of turbidity value of the fracturing water, when the turbidity value is stable, obtaining turbid liquid for fracturing water, and recording the turbidity detection value NTU of the turbid liquid for fracturing water 测 and the dosage of the precipitant NaOH, and the conductivity of the turbid liquid used for fracturing water at temperatures T1, T2, and T3; S4, according to the conductivity and Na + and K + The concentration correlation equation group is used to calculate the Na content in the fracturing water sample. + and K + concentration; S5, based on conductivity and Ca 2+ Mg 2+ and Ba 2+ The concentration correlation equation group is used to calculate the Ca content in the fracturing water sample. 2+ Mg 2+ and Ba 2+ concentration; S6, the Ca in the fracturing water sample obtained in step S5 is 2+ Mg 2+ and Ba 2+ The concentration of Ca is brought into the turbidity value and Ca 2+ Mg 2 + and Ba 2+ The concentration correlation equation group is used to obtain the total turbidity calculation value NTU of the turbid fluid used for fracturing water T , and the detection value NTU 测 By comparison, the Ca content of the fracturing water sample calculated in step S5 is determined. 2+ Mg 2+ and Ba 2+ The accuracy of the concentration.

[0019] Example 2: As an optimization of the above example, the sampling volume of the fracturing water sample is 1L to 20L, and the Na + The concentration range is 100.0mg / L to 50000.0mg / L, K + The concentration range is 100.0mg / L to 5000.0mg / L, Ca 2+ and Mg 2+ The concentration range of Ba 2+ The concentration range of Na in fracturing water samples is 10mg / L to 500.0mg / L. + , K + , Ca 2+ Mg 2+ and Ba 2+The content of each other metal cation is not higher than 50 mg / L, and the total content of other metal cations is not higher than 300 mg / L.

[0020] Example 3: As an optimization of the above example, in step S1, the conductivity and Na + and K + The concentration correlation equation group is carried out in the following steps: prepare a series of standard aqueous solutions of NaCl and KCl, use a conductivity meter to measure the conductivity of the series of standard aqueous solutions of NaCl and KCl at temperatures T1, T2 and T3, draw the concentration-conductivity curve of the standard aqueous solutions of NaCl and KCl at temperatures T1, T2 and T3, and fit to obtain a linear equation group 1. The expression of equation group 1 is as follows: σ (N+) =k 1(N+) ×C (N+) Formula 1-1 σ' (N+) =k1' (N+) ×C (N+) Formula 1-2 σ" (N+) =k1" (N+) ×C (N+) Formula 1-3 In the formula, N+ represents Na + or K + , C (N+) Indicates Na + or K + The concentration of the aqueous solution is in mg / L; σ (N+) ,σ' (N+) and σ" (N+) Na + or K + The conductivity of the aqueous solution at T1, T2 and T3, in μs / cm; k 1(N+) 、k1' (N+) and k1" (N+) Na + or K + Conductivity coefficient at temperatures T1, T2 and T3, unitless.

[0021] Example 4: As an optimization of the above example, in step S1, establish the relationship between turbidity value and Ca 2+ Mg 2+ and Ba 2+The concentration correlation equation group is carried out according to the following steps: prepare a series of standard aqueous solutions of CaCl2, MgCl2 and BaCl2, add sufficient amount of precipitant NaOH to them respectively, measure the turbidity of the standard aqueous solutions of CaCl2, MgCl2 and BaCl2 after reacting with sufficient amount of precipitant at temperature T1, draw the curve of the change of CaCl2, MgCl2 and BaCl2 concentration with turbidity respectively, and fit to obtain linear equation group 2. The expression of equation group 2 is as follows: NTU (M2+) =A 1(M2+) ×C (M2+) Formula 2 Among them, M2+ is Ca 2+ Mg 2+ Or Ba 2+ ; C (M2+) Ca 2+ Mg 2+ Or Ba 2+ Concentration of aqueous solution, in mg / L; NTU (M2+) Ca 2+ Mg 2+ Or Ba 2+ The turbidity of the aqueous solution after reacting with the precipitant NaOH, the unit is NTU; A 1(M2+) is the turbidity coefficient and has no unit.

[0022] Example 5: As an optimization of the above example, in step S1, establish the conductivity and Ca 2+ Mg 2+ and Ba 2+ The concentration correlation equation group is carried out in the following steps: the conductivity of the aqueous solution of the CaCl2, MgCl2 and BaCl2 series standard samples at temperatures T1, T2 and T3 is measured, the curve of the conductivity changing with the ion concentration at temperatures T1, T2 and T3 is plotted, and the linear equation group 3 is obtained by fitting. The expression of equation group 3 is as follows: σ (M2+) =k 2(M2+) ×C (M2+) Formula 3-1 σ' (M2+) =k2' (M2+) ×C (M2+) Formula 3-2 σ" (M2+) =k2" (M2+) ×C (M2+) Formula 3-3 In the formula, M2+ is Ca 2+ Mg 2+ Or Ba 2+ ; C (M2+) Ca 2+ Mg 2+ Or Ba2+ The concentration of the aqueous solution is in mg / L; σ (M2+) ,σ' (M2+) and σ" (M2+) Ca 2+ Mg 2+ Or Ba 2+ The conductivity of the aqueous solution at T1, T2 and T3, in μs / cm; k 2(M2+) 、k2' (M2+) and k2" (M2+) Ca 2+ Mg 2+ Or Ba 2+ Conductivity coefficient at temperatures T1, T2 and T3, unitless.

[0023] Example 6: As an optimization of the above example, the specific operation of step S4 is: according to the conductivity and Na + and K + The concentration correlation equation group converts the amount of precipitant NaOH into the Na added to the turbid liquid for fracturing water. + The concentration of Na in the fracturing water sample was calculated by establishing the following equation group 4: + and K + The concentration of , the expression of equation group 4 is as follows: σ1=k 1(Na+) C 1(Na+) + k 1 (K+) C (K+) Formula 4-1 σ'1=k' 1(Na+) C 1(Na+) + k' 1(K+) C (K+) Formula 4-2 σ"1=k" 1(Na+) C 1(Na+) + k" 1(K+) C (K+) Formula 4-3 C (Na+)= C 1(Na+) - C 2(Na+) Formula 4-4 In the formula, C 1(Na+) , C 1(K+) are respectively Na in the turbid liquid used for fracturing + and K + The concentration, C 2(Na+) The Na added to the turbid liquid for fracturing due to the addition of precipitant NaOH + Concentration, C (Na+) is the Na in the fracturing water sample +concentration, σ1, σ'1 and σ"1 are the conductivity of the turbid fluid for fracturing water at temperatures T1, T2 and T3, respectively, 1(Na+) 、k1' (Na+) and k1" (Na+) are Na in equation 1 at temperatures T1, T2 and T3 respectively. + The conductivity coefficient, k 1(K+) 、k1' (K+) and k1" (K+) are K in equation 1 at temperatures T1, T2 and T3 respectively. + The conductivity coefficient.

[0024] According to the physical and chemical properties of the precipitate, Ca in the turbid liquid of fracturing water 2+ Mg 2+ and Ba 2+ The precipitate formed has extremely low conductivity and can be ignored. In the actual production of fracturing water in oil fields, the monovalent metal ions are mainly Na + Mainly, may contain a small amount of K + , and the content of other monovalent metal ions can be ignored, so the Na in the fracturing water sample can be calculated by equation group 5 + and K + The concentration, C (Na+) and C (K+) (C 1(K+) Equivalent to K in fracturing water samples + The concentration of C (K+) ). The Na added by the precipitant NaOH + The concentration can be calculated from the volume of the fracturing water sample and the amount of the precipitant NaOH, wherein the precipitant NaOH can be an aqueous sodium hydroxide solution with a concentration of 20 g / L to 40 g / L.

[0025] Example 7: As an optimization of the above example, the specific operation of step S5 is: according to the conductivity and Na + and K + The concentration correlation equations, combined with the Na added by the precipitant NaOH + concentration, the following equation group 5 was established, and the Ca content in the fracturing water sample was calculated. 2+ Mg 2+ and Ba 2+ The concentration of , the expression of equation group 5 is: σ2= Formula 5-1 σ'2= Formula 5-2 σ"2= Formula 5-3 σ2=σ T -σ1+k 1(Na+)C 2(Na+) Formula 5-4 σ'2=σ' T -σ'1+k' 1(Na+) C 2(Na+) Formula 5-5 σ"2=σ" T -σ"1+k" 1(Na+) C 2(Na+) Formula 5-6 Where σ2, σ'2 and σ"2 are the changes in conductivity of the turbid fluid used for fracturing at temperatures T1, T2 and T3 respectively; C 2(Na+) is the increase in Na due to the addition of precipitant NaOH + Concentration; C (M2+) is the Ca in the fracturing water sample 2+ Mg 2+ Or Ba 2+ concentration; σ1, σ'1 and σ"1 are the conductivity of the turbid fluid for fracturing water at temperatures T1, T2 and T3 respectively; k 1(Na+) 、k1' (Na+) and k1" (Na+) are respectively Na in equation 1 + The corresponding conductivity coefficient, k 2(M2+) 、k2' (M2+) and k2" (M2+) are Ca in equation 3 2+ Mg 2+ Or Ba 2+ The conductivity coefficient.

[0026] The main divalent metal ions in oilfield fracturing water are Ca 2+ Mg 2+ Mainly, may contain a small amount of Ba 2+ , the content of other divalent metal ions is low, and the influence of other divalent metal ions can be ignored in actual production.

[0027] Example 8: As an optimization of the above example, in step S6, if |NTU T -NTU 测 |≤10.0, then the Ca content of the fracturing water sample calculated in step S5 is 2+ Mg 2+ and Ba 2+ The concentration is accurate, among which the total turbidity calculation value of the turbid fluid used for fracturing water is NTU T According to formula 6, NTU T = Formula 6 In the formula, C (M2+) is the Ca content in the fracturing water sample 2+ Mg2+ Or Ba 2+ The concentration is in mg / L, A 1(M2+) Ca 2+ Mg 2+ Or Ba 2+ The corresponding turbidity coefficient in equation 2.

[0028] Example 9: As an optimization of the above example, in step S3, while adding the precipitant NaOH to the fracturing water sample, the fracturing water sample is stirred at a stirring speed of 100 rpm to 1000 rpm and a stirring time of 1 min to 5 min.

[0029] Embodiment 10: As an optimization of the above embodiment, the temperatures T1, T2 and T3 are all between 0 and 90°C, T1<T 2＜ T3 and the intervals between T1 and T2, T2 and T3 are 10°C to 20°C.

[0030] The present invention provides a process for rapid detection of metal ions contained in oil field on-site fracturing water, which is suitable for Na + , K + , Ca 2+ Mg 2+ and Ba 2+ The determination of ion content in the fracturing water sample is mainly based on the relationship between metal ion concentration and conductivity. + , K + and divalent metal ions Ca 2+ Mg 2+ and Ba 2+ The contribution to the conductivity of fracturing water at different temperatures is determined by measuring the turbidity based on the principle that divalent metal ions can react chemically with precipitants to form precipitates that make fracturing water turbid. The contribution of divalent metal ions to the conductivity of fracturing water is shielded by the principle that divalent metal ion precipitates are non-conductive. The conductivity of monovalent and divalent metal ions in fracturing water is determined by establishing the change in the conductivity of fracturing water before and after the formation of divalent metal ions. The conductivity of monovalent and divalent metal ions in fracturing water is determined by establishing the correlation equation between the conductivity and concentration of monovalent and divalent metal ions in fracturing water. + , K + , and divalent metal ions Ca 2+ Mg 2+ and Ba 2+ The specific content of Ca 2+ Mg 2+ and Ba 2+The content is verified by turbidity method to verify the accuracy of the method. In the process of establishing the correlation equation group of the present invention, a wider range of ion concentration variation of fracturing water is selected to be associated with turbidity and conductivity. The advantage is that the established correlation simulation equation group can be applied to complex situations such as large fluctuation range of fracturing water component concentration, and the operation steps and accuracy are not affected by changes in conditions. The rapid detection method provided by the present invention can be used for on-site rapid detection of oilfield fracturing water, and can also be extended to other Na + , K + , Ca 2+ Mg 2+ and Ba 2+ Rapid detection of water bodies with the main focus on detection may include water bodies around oil fields, industrial wastewater, etc.

[0031] Example 11: Na in the fracturing water sample + , K + , Ca 2+ Mg 2+ , Ba 2+ The content determination was carried out according to the following steps: Preparation of Na + , K + , Ca 2+ Mg 2+ , Ba 2+ A series of standard aqueous solutions with contents of 10000 mg / L, 600 mg / L, 500 mg / L, 500 mg / L, and 100 mg / L are prepared. At the experimental temperatures T1, T2, and T3, which are 25°C, 35°C, and 45°C, respectively, the coefficients in equation group 1 and equation group 3 are determined according to the steps in Example 1, respectively: k 1 (Na+) 、k1' (Na+) and k1" (Na+) They are 2.01, 2.11 and 2.22 respectively; k 1 (K+) 、k1' (K+) and k1" (K+) They are 1.90, 2.01 and 2.10 respectively; k 2 (Ca2+) 、k2' (Ca2+) and k2" (Ca2+) They are 2.83, 3.00 and 3.16 respectively; k 2 (Mg2+) 、k2' (Mg2+) and k2" (Mg2+) They are 3.16, 3.31 and 3.49 respectively; k 2 (Ba2+) 、k2' (Ba2+) and k2" (Ba2+)They are 2.21, 2.32 and 2.39 respectively.

[0032] In equation 2: A 1(Ca2+) , A 1(Mg2+) and A 1( Ba2+) They are 0.76, 0.72 and 0.39 respectively; The σ1, σ'1 and σ"1 of the fracturing water sample were measured at 25℃, 35℃ and 45℃ to be 24576μs / cm, 25703μs / cm and 26983μs / cm respectively.

[0033] Continuously add the precipitant NaOH to the fracturing water sample in step S2, stir evenly and measure the turbidity value change of the fracturing water. When the turbidity value is stable, obtain the turbidity liquid of the fracturing water and record the turbidity detection value NTU of the turbid liquid of the fracturing water 测 =733.6 and the amount of precipitant NaOH, and the σ of the turbid liquid for fracturing water at 25℃, 35℃ and 45℃ were determined. T ,σ' T and σ" T They are 24555.1μs / cm, 25687.5μs / cm and 26887μs / cm respectively.

[0034] Substituting the above data into equations 4 and 5, we can obtain: Na + , K + , Ca 2+ Mg 2+ , Ba 2+ The contents were 9972.6 mg / L, 617.5 mg / L, 506.1 mg / L, 502.7 mg / L and 132.5 mg / L respectively.

[0035] Ca 2+ Mg 2+ , Ba 2+ Substitute the content into formula 6 to calculate NTU T =729.0,|NTU T -NTU 测 |=4.6, indicating that the measurement results are accurate.

[0036] Example 12: Na in the fracturing water sample + , K + , Ca 2+ Mg 2+ , Ba 2+ The content determination was carried out according to the following steps: Preparation of Na + , K + , Ca 2+ Mg 2+ , Ba2+ A series of standard aqueous solutions with contents of 20000 mg / L, 1200 mg / L, 1000 mg / L, 1000 mg / L, and 200 mg / L are prepared. At the experimental temperatures T1, T2, and T3, which are 25°C, 35°C, and 55°C, respectively, the coefficients in equation group 1 and equation group 3 are determined according to the steps in Example 1, respectively: k 1 (Na+) 、k1' (Na+) and k1" (Na+) They are 2.02, 2.10 and 2.32 respectively; k 1 (K+) 、k1' (K+) and k1" (K+) They are 1.91, 2.01 and 2.20 respectively; k 2 (Ca2+) 、k2' (Ca2+) and k2" (Ca2+) They are 2.83, 3.00 and 3.31 respectively; k 2 (Mg2+) 、k2' (Mg2+) and k2" (Mg2+) They are 3.16, 3.31 and 3.63 respectively; k 2 (Ba2+) 、k2' (Ba2+) and k2" (Ba2+) They are 2.21, 2.32 and 2.51 respectively.

[0037] In equation 2: A 1 (Ca 2+) , A 1 (Mg2+) and A 1 (Ba2+) They are 0.76, 0.72 and 0.39 respectively.

[0038] The σ1, σ'1 and σ"1 of the fracturing water sample were measured at 25℃, 35℃ and 55℃ to be 49167μs / cm, 51511μs / cm and 56706μs / cm respectively.

[0039] Continuously add the precipitant NaOH to the fracturing water sample in step S2, stir evenly and measure the turbidity value change of the fracturing water. When the turbidity value is stable, obtain the turbidity liquid of the fracturing water and record the turbidity detection value NTU of the turbid liquid of the fracturing water 测 =1449.3 and the amount of precipitant NaOH, and the σ of the turbid liquid for fracturing water at 25℃, 35℃ and 55℃ were determined. T ,σ' T and σ" T They are 49063.5μs / cm, 51388.2μs / cm and 56516.6μs / cm respectively.

[0040] Substituting the above data into equations 4 and 5, we can obtain: Na + , K + , Ca 2+ Mg 2+ , Ba 2+ The contents were 19872.1 mg / L, 1225.7 mg / L, 1018.6 mg / L, 1025.2 mg / L and 216.8 mg / L respectively.

[0041] Ca 2+ Mg 2+ , Ba 2+ Substitute the content into formula 6 to calculate NTU T =1458.0,|NTU T -NTU 测 |=8.7, indicating that the measurement results are accurate.

[0042] Example 13: Na in the fracturing water sample + , K + , Ca 2+ Mg 2+ , Ba 2+ The content determination was carried out according to the following steps: Preparation of Na + , K + , Ca 2+ Mg 2+ , Ba 2+ The contents of the series of standard aqueous solutions are 5000 mg / L, 300 mg / L, 250 mg / L, 250 mg / L, and 50 mg / L, respectively. At the experimental temperatures T1, T2, and T3 of 25°C, 45°C, and 55°C, respectively, according to the steps in Example 1, the coefficients in Equation Group 1 and Equation Group 3 are determined to be: k 1 (Na+) 、k1' (Na+) and k1" (Na+) They are 2.03, 2.23 and 2.34 respectively; k 1 (K+) 、k1' (K+) and k1" (K+) They are 1.90, 2.10 and 2.21 respectively; k 2 (Ca2+) 、k2' (Ca2+) and k2" (Ca2+) They are 2.83, 3.16 and 3.31 respectively; k 2 (Mg2+) 、k2' (Mg2+) and k2" (Mg2+) They are 3.16, 3.49 and 3.63 respectively; k 2 (Ba2+) 、k2'(Ba2+) and k2" (Ba2+) They are 2.21, 2.39 and 2.51 respectively.

[0043] In equation 2: A 1(Ca2+) , A 1(Mg2+) and A 1(Ba2+) They are 0.76, 0.72 and 0.39 respectively.

[0044] The σ1, σ'1 and σ"1 of the fracturing water sample were measured at 25℃, 45℃ and 55℃ to be 12283μs / cm, 13465μs / cm and 14138μs / cm respectively.

[0045] Continuously add the precipitant NaOH to the fracturing water sample in step S2, stir evenly and measure the turbidity value change of the fracturing water. When the turbidity value is stable, obtain the turbidity liquid of the fracturing water and record the turbidity detection value NTU of the turbid liquid of the fracturing water 测 =367.3 and the amount of precipitant NaOH, and the σ of the turbid liquid for fracturing water at 225℃, 45℃ and 55℃ were determined. T ,σ' T and σ" T They are 12216μs / cm, 13295μs / cm and 14056μs / cm respectively.

[0046] Substituting the above data into equations 4 and 5, we can obtain: Na + , K + , Ca 2+ Mg 2+ , Ba 2+ The contents were 4982.7 mg / L, 300.6 mg / L, 258.1 mg / L, 253.8.2 mg / L and 39.6 mg / L respectively.

[0047] Ca 2+ Mg 2+ , Ba 2+ Substitute the content into formula 6 to calculate NTU T =364.5,|NTU T -NTU 测 |=2.8, indicating that the measurement results are accurate.

[0048] In summary, the present invention provides a process for rapid detection of metal ions contained in oil field on-site fracturing water, which is suitable for Na + , K + , Ca 2+ Mg 2+ and Ba 2+The method is to determine the ion content in the main fracturing water sample. The method has the characteristics of fast, accurate and low cost detection, and the detection process does not use any environmentally harmful chemicals. The amount of precipitant used in the turbidity measurement process is small, and the generated precipitate is a solid substance existing in nature, which is non-toxic and easy to handle; the conductivity meter detection process only consumes electrical energy and the power consumption is extremely low. The process method described in the present invention has fast detection and accurate data, and can provide data support for on-site configuration of fracturing fluid.

[0049] The above technical features 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 situations.

Claims

1. A method for rapid detection of metal ions contained in fracturing water, characterized in that Follow these steps: S1, respectively establish conductivity and Na + and K + Concentration correlation equations, turbidity values ​​and Ca 2+ Mg 2+ and Ba 2+ Concentration-related equations and conductivity and Ca 2+ Mg 2+ and Ba 2+ Concentration-related equations; S2, measuring the total conductivity of the fracturing water sample at temperatures T1, T2 and T3; S3, continuously adding precipitant NaOH to the fracturing water sample of step S2, and measuring the change of turbidity value of the fracturing water, when the turbidity value is stable, obtaining turbid liquid for fracturing water, and recording the turbidity detection value NTU of the turbid liquid for fracturing water 测 and the dosage of the precipitant NaOH, and the conductivity of the turbid liquid used for fracturing water at temperatures T1, T2, and T3; S4, according to the conductivity and Na + and K + The concentration correlation equation group is used to calculate the Na content in the fracturing water sample. + and K + concentration; S5, based on conductivity and Ca 2+ Mg 2+ and Ba 2+ The concentration correlation equation group is used to calculate the Ca content in the fracturing water sample. 2+ Mg 2+ and Ba 2+ concentration; S6, the Ca in the fracturing water sample obtained in step S5 is 2+ Mg 2+ and Ba 2+ The concentration of Ca is brought into the turbidity value and Ca 2+ Mg 2+ and Ba 2+ The concentration correlation equation group is used to obtain the total turbidity calculation value NTU of the turbid fluid used for fracturing water T , and the detection value NTU 测 By comparison, the Ca content of the fracturing water sample calculated in step S5 is determined. 2+ Mg 2+ and Ba 2+ The accuracy of the concentration.

2. The method for rapid detection of metal ions contained in fracturing water according to claim 1, characterized in that The sampling volume of fracturing water samples is 1L to 20L. + The concentration range is 100.0mg / L to 50000.0mg / L, K + The concentration range is 100.0mg / L to 5000.0mg / L, Ca 2+ and Mg 2+ The concentration range of Ba 2+ The concentration range of Na in fracturing water samples is 10mg / L to 500.0mg / L. + , K + , Ca 2+ Mg 2+ and Ba 2+ The content of each other metal cation is not higher than 50 mg / L, and the total content of other metal cations is not higher than 300 mg / L.

3. The method for rapid detection of metal ions contained in fracturing water according to claim 1 or 2, characterized in that In step S1, establish the conductivity and Na + and K + The concentration correlation equation group is carried out in the following steps: prepare a series of standard aqueous solutions of NaCl and KCl, use a conductivity meter to measure the conductivity of the series of standard aqueous solutions of NaCl and KCl at temperatures T1, T2 and T3, draw the concentration-conductivity curve of the standard aqueous solutions of NaCl and KCl at temperatures T1, T2 and T3, and fit to obtain a linear equation group 1. The expression of equation group 1 is as follows: σ (N+) =k 1(N+) ×C (N+) Formula 1-1 in (N+) =k1' (N+) ×C (N+) formula 1-2 in (N+) =k1" (N+) ×C (N+) formula 1-3 In the formula, N+ represents Na + or K + , C (N+) Indicates Na + or K + The concentration of the aqueous solution is in mg / L; σ (N+) ,σ' (N+) and σ" (N+) Na + or K + The conductivity of the aqueous solution at T1, T2 and T3, in μs / cm; k 1(N+) 、k1' (N+) and k1" (N+) Na + or K + Conductivity coefficient at temperatures T1, T2 and T3, unitless.

4. The method for rapid detection of metal ions contained in fracturing water according to any one of claims 1 to 3, characterized in that In step S1, establish the turbidity value and Ca 2+ Mg 2+ and Ba 2+ The concentration correlation equation group is carried out according to the following steps: prepare a series of standard aqueous solutions of CaCl2, MgCl2 and BaCl2, add sufficient amount of precipitant NaOH to them respectively, measure the turbidity of the standard aqueous solutions of CaCl2, MgCl2 and BaCl2 after reacting with sufficient amount of precipitant at temperature T1, draw the curve of the change of CaCl2, MgCl2 and BaCl2 concentration with turbidity respectively, and fit to obtain linear equation group 2. The expression of equation group 2 is as follows: NTU (M2+) =A 1(M2+) ×C (M2+) Equation 2 Among them, M2+ is Ca 2+ Mg 2+ Or Ba 2+ ; C (M2+) Ca 2+ Mg 2+ Or Ba 2+ Concentration of aqueous solution, in mg / L; NTU (M2+) Ca 2+ Mg 2+ Or Ba 2+ The turbidity of the aqueous solution after reacting with the precipitant NaOH, the unit is NTU; A 1(M2+) is the turbidity coefficient and has no unit.

5. The method for rapid detection of metal ions contained in fracturing water according to claim 3 or 4, characterized in that In step S1, establish the conductivity and Ca 2+ Mg 2+ and Ba 2+ The concentration correlation equation group is carried out in the following steps: the conductivity of the aqueous solution of the CaCl2, MgCl2 and BaCl2 series standard samples at temperatures T1, T2 and T3 is measured, the curve of the conductivity changing with the ion concentration at temperatures T1, T2 and T3 is plotted, and the linear equation group 3 is obtained by fitting. The expression of equation group 3 is as follows: σ (M2+) =k 2(M2+) ×C (M2+) Formula 3-1 σ' (M2+) =k2' (M2+) ×C (M2+) Formula 3-2 σ" (M2+) =k2" (M2+) ×C (M2+) Formula 3-3 In the formula, M2+ is Ca 2+ Mg 2+ Or Ba 2+ ; C (M2+) Ca 2+ Mg 2+ Or Ba 2+ The concentration of the aqueous solution is in mg / L; σ (M2+) ,σ' (M2+) and σ" (M2+) Ca 2+ Mg 2+ Or Ba 2+ The conductivity of the aqueous solution at T1, T2 and T3, in μs / cm; k 2(M2+) 、k2' (M2+) and k2" (M2+) Ca 2+ Mg 2+ Or Ba 2+ Conductivity coefficient at temperatures T1, T2 and T3, unitless.

6. The method for rapid detection of metal ions contained in fracturing water according to claim 3, 4 or 5, characterized in that The specific operation of step S4 is: according to the conductivity and Na + and K + The concentration correlation equation group converts the amount of precipitant NaOH into the Na added to the turbid liquid for fracturing water. + The concentration of Na in the fracturing water sample was calculated by establishing the following equation group 4: + and K + The concentration of , the expression of equation group 4 is as follows: σ1=k 1(Na+) C 1(Na+) + k 1 (K+) C (K+) Formula 4-1 σ'1=k' 1(Na+) C 1(Na+) + k' 1(K+) C (K+) Formula 4-2 σ"1=k" 1(Na+) C 1(Na+) + k" 1(K+) C (K+) Formula 4-3 C (Na+)= C 1(Na+) - C 2(Na+) Formula 4-4 In the formula, C 1(Na+) , C 1(K+) are respectively Na in the turbid liquid used for fracturing + and K + The concentration, C 2(Na+) The Na added to the turbid liquid for fracturing due to the addition of precipitant NaOH + Concentration, C (Na+) is the Na in the fracturing water sample + concentration, σ1, σ'1 and σ"1 are the conductivity of the turbid fluid for fracturing water at temperatures T1, T2 and T3, respectively, 1(Na+) 、k1' (Na+) and k1" (Na+) are Na in equation 1 at temperatures T1, T2 and T3 respectively. + The conductivity coefficient, k 1(K+) 、k1' (K+) and k1" (K+) are K in equation 1 at temperatures T1, T2 and T3 respectively. + The conductivity coefficient.

7. The method for rapid detection of metal ions contained in fracturing water according to claim 5, characterized in that The specific operation of step S5 is: according to the conductivity and Na + and K + The concentration correlation equations, combined with the Na added by the precipitant NaOH + concentration, the following equation group 5 was established, and the Ca content in the fracturing water sample was calculated. 2+ Mg 2+ and Ba 2+ The concentration of , the expression of equation group 5 is: σ2= Formula 5-1 σ'2= formula 5-2 σ"2= formula 5-3 σ2=σ T -σ1+k 1(Na+) C 2(Na+) formula 5-4 σ'2=σ' T -σ'1+k' 1(Na+) C 2(Na+) formula 5-5 σ"2=σ" T -σ"1+k" 1(Na+) C 2(Na+) formula 5-6 Where σ2, σ'2 and σ"2 are the changes in conductivity of the turbid fluid used for fracturing at temperatures T1, T2 and T3 respectively; C 2(Na+) is the increase in Na due to the addition of precipitant NaOH + Concentration; C (M2+) is the Ca in the fracturing water sample 2+ Mg 2+ Or Ba 2+ concentration; σ1, σ'1 and σ"1 are the conductivity of the turbid fluid for fracturing water at temperatures T1, T2 and T3 respectively; k 1(Na+) 、k1' (Na+) and k1" (Na+) are respectively Na in equation 1 + The corresponding conductivity coefficient, k 2(M2+) 、k2' (M2+) and k2" (M2+) are Ca in Eq. 3 2+ Mg 2+ Or Ba 2+ The conductivity coefficient.

8. The method for rapid detection of metal ions contained in fracturing water according to claim 7, characterized in that In step S6, if |NTU T -NTU 测 |≤10.0, then the Ca content of the fracturing water sample calculated in step S5 is 2+ Mg 2+ and Ba 2+ The concentration is accurate, among which the total turbidity calculation value of the turbid fluid used for fracturing water is NTU T According to formula 6, NTU T = Formula 6 In the formula, C (M2+) is the Ca content in the fracturing water sample 2+ Mg 2+ Or Ba 2+ The concentration is in mg / L, A 1(M2+) Ca 2+ Mg 2+ Or Ba 2+ The corresponding turbidity coefficient in equation 2.

9. The method for rapid detection of metal ions contained in fracturing water according to any one of claims 1 to 8, characterized in that In step S3, while adding the precipitant NaOH to the fracturing water sample, the fracturing water sample is stirred at a stirring speed of 100 rpm to 1000 rpm and a stirring time of 1 min to 5 min.

10. The method for rapid detection of metal ions contained in fracturing water according to any one of claims 1 to 9, characterized in that The temperatures T1, T2 and T3 are all between 0 and 90°C, T1<T 2＜ T3 and the intervals between T1 and T2, T2 and T3 are 10°C to 20°C.