Method and system for evaluating uncertainty of quantitative analysis of oil field water ions

Abstract

The invention discloses an evaluation method and system for uncertainty of quantitative analysis of oil field water ions. The evaluation method comprises the following steps: (1) collecting data; (2) data analysis: according to the data collected in the step (1), analyzing the attribute of the oil field water sample, and determining and calculating key parameters, the key parameters including an oil field water matrix factor # imgabs0 #, and interionic cross interference coefficients # imgabs1 #, # imgabs2 # and # imgabs3 #, the units of which are dimensionless; (3) result calculation: calculating the total relative uncertainty # imgabs4 #; (4) improving the confidence: when # imgabs5 # is less than or equal to 10%, finishing analysis and evaluation; and when # imgabs6 # is greater than 10%, the detection scheme is optimized. According to the method provided by the invention, aiming at the characteristics of high concentration difference and complex matrix of oil field water, cross interference between ions and matrix effect are particularly considered, and the accuracy of uncertainty evaluation is improved; by introducing uncertainty evaluation of sample state stability, the traceability of the original state of the sample is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of water analysis and detection, and in particular relates to an uncertainty evaluation method and system for quantitative analysis of ions in oilfield water with complex high-concentration-difference water bodies. Background Art

[0002] Uncertainty assessment is a crucial indicator of the reliability of measurement results. In water analysis and testing, the traditional uncertainty assessment method (GUM) generally assumes uniform sample concentration, simple composition, and stable state. Based on a linear measurement model, uncertainty is considered the sum of the standard deviations of various influencing factors. This method typically only assesses the instrument and its current errors, failing to consider the dynamic changes in the water's inherent characteristics and state. This makes the test results less useful for characterizing and tracing the sample's original state. Oilfield water often contains high concentrations of different ions, such as chloride to sulfate ions with a concentration ratio of up to 50:1 and sodium to potassium ions with a concentration ratio of up to 200:1. These ions can interfere with each other, resulting in competitive reactions, enhanced matrix effects, and signal overlap. Consequently, errors arising from changes in the water sample's state, matrix effects, inter-ion interference, and sample pretreatment are more significant. Furthermore, traditional uncertainty assessment methods suffer from long cycle times, delayed feedback, and low efficiency. Summary of the Invention

[0003] In response to the shortcomings of the existing technology, the present invention proposes a method for evaluating the uncertainty of quantitative analysis of ions in oilfield water. This method takes into account the influence of the matrix characteristics of the oilfield water itself, the changes in oilfield water detection time, and the mutual influence between high-concentration ions on the accuracy of ion concentration detection. Based on this method, an uncertainty evaluation and calculation system is constructed, which greatly shortens the time of manual uncertainty evaluation and calculation process of oilfield water ion analysis. The original state of the water sample can be inverted and evaluated through the uncertainty evaluation of the detection results.

[0004] A method for evaluating the uncertainty of quantitative analysis of ions in oilfield water, characterized by comprising the following steps: (1) Data collection: including: physical and chemical characteristic parameters of oilfield water samples, quality control sample test results and test instrument calibration parameters; among them, the physical and chemical characteristic parameters of oilfield water samples should at least include pH value, total dissolved solids and ion content; (2) Data analysis: Based on the data collected in step (1), the properties of the oilfield water sample are analyzed and the key parameters are determined and calculated. The key parameters include the oilfield water matrix factor , inter-ion cross-interference coefficient , and The units are dimensionless; (3) Result calculation: Calculate the total relative uncertainty , = in, is the relative uncertainty of instrument error, is the relative uncertainty of sample state stability, is the relative uncertainty of the dilution error, is the relative uncertainty of cross-interference between ions, is the relative uncertainty of matrix effect, 、 、 、 、 、 The unit is %; (4) Confidence improvement: When When ≤10%, the analysis and evaluation is completed; when When the rate is greater than 10%, optimize the detection plan.

[0005] Preferably, the oilfield water matrix factor The calculation is as follows: = in, is the slope of the standard curve of the matrix-free solution; is the slope of the standard curve containing matrix solution; The matrix-free solution and the matrix-containing solution are prepared by the following method: two sets of target ion standard sample solutions with the same concentration gradient are prepared using ultrapure water and oilfield water samples, namely the matrix-free solution and the matrix-containing solution; a standard curve is drawn with the concentration of the target ion standard sample as the abscissa and the instrument detector response signal value as the ordinate; the response signal value is the peak area, peak height or absorbance.

[0006] Preferably, the ion cross interference coefficient K ab The calculation formula is: = ; in, and The calibration method is as follows: Use ultrapure water to prepare Solution, keep Add interfering ions at constant concentration The solution is respectively denoted as solution and solution , and the response signal values ​​are detected by instruments and recorded as and .

[0007] Preferably, the relative uncertainty of the instrument error is The calculation is as follows: ; in, The first Secondary detection concentration value; is the number of detections, for The average value of the detections, 、 The unit is mg / L; is the relative expanded uncertainty given in the instrument calibration certificate, in %; , is the inclusion factor, dimensionless.

[0008] Preferably, the relative uncertainty of the sample state stability is The calculation is as follows: = in, The time interval between oilfield water sampling and testing, in hours; is the standard deviation of the relative concentration change rate of the target ion in the oilfield water sample or equivalent stability simulation solution, in h -1 ; is the number of detections in the time series, ≥5; The standard deviation of the relative concentration change rate of the target ion in the actual oilfield water sample or equivalent stability simulation solution Calculated by the following steps: (S1) After the oilfield water sample is collected or the equivalent stability simulation solution is prepared, the same target ion is analyzed according to the time sequence. Detection times to obtain time-concentration data points; (S2) The concentration change rate of two adjacent time points in the time series , unit is h -1 ,in, 、 It is the concentration value obtained by testing at two adjacent time points, in mg / L; for The average value of 、 is the time between two adjacent time points, in h; is the average change rate of concentration at two adjacent time points, The average value of K Values ​​range from 2 to ; (S3) = .

[0009] Preferably, the relative uncertainty of the dilution error is The calculation is as follows: = in, is the volume distribution factor, which characterizes the volume distribution uniformity of the oilfield water sample during dilution and is dimensionless; is the number of dilutions, dimensionless; is the concentration of the target ion in the blank solution, in mg / L; is the concentration of the target ion in the measurement solution, in mg / L; is the relative standard deviation of the target ion concentration in the blank solution, in %; described is the relative standard deviation of the synthetic volume, in %, which is calculated as follows: is the capacity error, is the nominal volume, and The units are consistent, Indicates a capacity device; For capacity instruments The inclusion factor of The volume distribution factor The value of is based on the viscosity of the water sample at 25℃, and the value is as follows: 5 mPa·s, =1.0; when 5 mPa·s Viscosity 8 mPa·s, c =1.2; when the solution has precipitation or the viscosity is greater than 8 mPa·s, =1.7.

[0010] Preferably, the relative uncertainty of the cross-interference between ions is The calculation is as follows: =| K ab | is the inter-ion interference coefficient, dimensionless; Target ions in oilfield water samples The concentration of , in mg / L; Interfering ions in oilfield water samples The concentration is in mg / L.

[0011] Preferably, the relative uncertainty of matrix effect is calculated as follows: .

[0012] Preferably, the optimized detection scheme includes at least one of the following methods: increasing the number of repeated detections; shortening the time interval from sampling to detection to reduce the influence of sample state instability; using high-precision detection equipment; adding ion interference inhibitors to eliminate specific ion interference.

[0013] An evaluation system for the uncertainty of quantitative analysis of oilfield water ions, which is used to execute the method for evaluating the uncertainty of quantitative analysis of oilfield water ions described in the present invention, includes the following modules connected in sequence: (1) Data acquisition module: used to acquire data; (2) Data analysis module: used to analyze the acquired data; (3) Result calculation module: used to calculate the total relative uncertainty , and the calculation model of the total relative uncertainty is = where is the relative uncertainty of instrument error, is the relative uncertainty of sample state stability, is the relative uncertainty of dilution error, is the relative uncertainty of cross interference between ions, is the relative uncertainty of matrix effect, , , , , , are all in units of %; [[ID=​​​​​​​​​​​​​​​​

[0015] Common inter-ion cross-interferences in this field are as follows: Cl - -SO4 2- 、Cl - -HCO3 - 、Na + -Ca 2+ , Ca 2+ -Mg 2+ 、Cl - -Ca 2+ 、SO4 2- -HCO3 - 、Na + -K + 、Fe 3+ -Cl - 、HCO3 - -Ca²⁺ (scaling interference), SO4 2- -Ba 2+ (precipitation interference), organic acid-Cl - 、H2S-Fe 2+ .

[0016] Beneficial effects of the present invention: 1. In view of the high concentration difference and complex matrix characteristics of oilfield water, special consideration is given to the cross-interference between ions and matrix effects, which improves the accuracy of uncertainty assessment; 2. By introducing the uncertainty assessment of sample state stability, the traceability of the original state of the sample is improved; 3. The system realizes automated assessment, greatly shortening the assessment time and improving efficiency; 4. When the uncertainty is large, the system can automatically provide optimization solutions to improve the confidence of the test results. DETAILED DESCRIPTION

[0017] Example 1 Take the uncertainty assessment of quantitative analysis of water ions produced by a carbon dioxide storage flooding well in a certain oil field as an example: Step 1: Collect the following data based on the uncertainty components: Quality control sample test results: a. Instrument error related data: Take Cl - Quality control samples, i.e. Cl - The standard solution (concentration of 12000 mg / L) was tested for repeatability 10 times (i.e. =10), and obtain 10 measured values to (Unit: mg / L) are: 12010, 11980, 12050, 12020, 11990, 12030, 12000, 12040, 11970, 12060, average value of 10 measurements The relative expanded uncertainty of the ion chromatograph was obtained from the instrument calibration certificate. =1%, ; b. Sample state stability error related data: the above Cl - The standard solution was used as an equivalent stability simulation solution to simulate the stability conditions of oilfield water samples. After the equivalent stability simulation solution was prepared, the same concentration of 12000 mg / L Cl was tested in a time series (0h, 4h, 8h, 24h, 48h). - The standard solution was measured 5 times (i.e. =5), the concentration measurements (in mg / L) are: 12000, 11985, 11960, 11940, 11920; c. Dilution process related data: The oilfield water sample was diluted 1000 times before testing (using 1000 Use a L pipette to transfer 1 mL of sample to a 1000 mL volumetric flask and adjust the volume. The volume error of the pipette is obtained from the calibration certificate. =-10 μL (satisfies normal distribution, the inclusion factor of the pipette is = ); capacity error of volumetric flask +0.4mL (satisfying triangular distribution, the coverage factor of the volumetric flask = ); Ultrapure water was used as blank solution, and Cl - Concentration =0.1 mg / L, tested 10 times, relative standard deviation of blank solution test =10%; d. Data related to cross-interference between ions: Through experimental calibration, Cl - Interference coefficients with other ions , dimensionless: Cl - with Fe 3+ For example, The calculation process is as follows: Step 1: Prepare two solutions using ultrapure water: solution :Contains only Cl - ions 11273.65 mg / L; solution :Contains Cl - ions 11273.65 mg / L and Fe 3+ ions 1601.15 mg / L; Step 2: Solution and solution After diluting 1000 times, Cl - The conductivity response signal value of: solution : Peak area = 2.523 solution : Peak area =2.503 Step 3: Calculate the interference coefficient: = ( - ) / = (2.503-2.523) / 2.523 = -0.0080; Using the same method, the calculation results of other interference coefficients are as follows: Cl - With SO4 2- : =0.001; Cl - With HCO3 - : =0.002; Cl - With Ca 2+ : =0.005; e. Matrix effect related data: Using the standard addition method, two sets of target ion Cl with the same concentration gradient were prepared using ultrapure water and the oil field water sample. - The solutions of standard samples are matrix-free and matrix-containing solutions, Cl - The concentration gradient of the standard sample (in mg / L): 0, 2500, 5000, 7500, 10000, 12500, 15000; the concentration of the target ion standard sample is used as the horizontal axis, and the peak area (in mg / L) is used as the horizontal axis. ) is the ordinate, and two standard curves of matrix-free solution and matrix-containing solution are obtained by linear fitting, and the slopes of the two standard curves are: Matrix-free solution: Slope = 0.95; With matrix solution: Slope =0.98; Matrix effect factors: = = 0.95 / 0.98 = 0.9694; Step 2: Data analysis: Matrix type identification: TDS = 17945.86 mg / L, the oilfield water sample belongs to medium-salinity formation water, matrix factor =0.9694; Identification of the main interference source: Determine Cl - Detection is affected by the following interferences: SO4 2- ( =1359.78 mg / L, interference coefficient =0.001), HCO3 - ( =445.15 mg / L, interference coefficient =0.002), Ca 2+ ( =3478.58 mg / L, interference coefficient =0.005), Fe 3+ ( =1601.15 mg / L, interference coefficient = -0.008).

[0018] Step 3. Total relative uncertainty calculate: (31) Calculation of relative uncertainty of instrument error: According to Cl - 10 measurement data of standard solution, = 0.56%; (32) Calculation of relative uncertainty of sample state stability: = = =11961mg / L, =8 h, = =-3.13 h -1 , = =-5.22 h -1 , = =-1.04 h -1 , = =-0.696 h -1 , = =-2.52 h -1 , = =2.105 h -1 , = = 8 =0.0075%; (33) Calculation of relative uncertainty component of dilution process: This example adopts one-step dilution, i.e. =1; =0.1mg / L, =10%; the oil field water sample has sediment, so Take 1.7; = 0.71%; The Cl content in the oilfield water sample was obtained from the collected data. - The ion concentration is 11273.65 mg / L. After dilution 1000 times, the target ion Cl in the solution is measured. - The concentration is =11.2736mg / L, calculate = =1.21%; (34) Calculation of relative uncertainty of cross-interference between ions: Targeting Cl - , considering SO4 2- 、HCO3 - , Ca 2+ 、Fe 3+ Four interfering ions, the concentration and interference coefficient of the interfering ions given by the data analysis in step 2 above, and the target ion Cl in the oilfield water sample - The concentration ( = 11273.65 mg / L), calculate each pair of interfering ions Cl -The cross-interference uncertainty component of: =| =0.001 =0.29%, =| = 0.00 =1.01%, =| = 0.005 =0.90%, =| = 0.008 =2.12%, Then synthesize, so, ; (35) Calculation of matrix effect uncertainty: = =3.06 ; (36) Calculation : = =4.19%; ≤10%, the analysis and evaluation is completed.

[0019] Example 2 A system for evaluating the uncertainty of quantitative analysis of ions in oilfield water, which is used to implement the uncertainty evaluation method of quantitative analysis of ions in oilfield water described in the present invention, specifically includes the following modules connected in sequence: (1) Data acquisition module: used to collect data; (2) Data analysis module: used to analyze the collected data; (3) Result calculation module: used to calculate the total relative uncertainty , total relative uncertainty The calculation model is = in, is the relative uncertainty of instrument error, is the relative uncertainty of sample state stability, is the relative uncertainty of the dilution error, is the relative uncertainty of cross-interference between ions, is the relative uncertainty of matrix effect, 、 、 、 、 、 The unit is %; (4) Confidence Enhancement Module: When When ≤10%, the analysis and evaluation is completed; when When the rate is greater than 10%, optimize the detection plan.

[0020] The optimized detection scheme includes at least one of the following methods: increasing the number of repeated detections; shortening the time interval from sampling to detection to reduce the impact of sample state instability; using high-precision detection equipment; adding ion interference inhibitors to eliminate specific ion interference.

Claims

1. A method for evaluating the uncertainty of quantitative analysis of ions in oilfield water, characterized by: The following steps are involved: (1) Data collection: including: physical and chemical characteristic parameters of oilfield water samples, quality control sample test results and test instrument calibration parameters; among them, the physical and chemical characteristic parameters of oilfield water samples should at least include pH value, total dissolved solids and ion content; (2) Data analysis: Based on the data collected in step (1), the properties of the oilfield water sample are analyzed and the key parameters are determined and calculated. The key parameters include the oilfield water matrix factor , inter-ion cross-interference coefficient , and The units are dimensionless; (3) Result calculation: Calculate the total relative uncertainty , = in, is the relative uncertainty of instrument error, is the relative uncertainty of sample state stability, is the relative uncertainty of the dilution error, is the relative uncertainty of cross-interference between ions, is the relative uncertainty of matrix effect, 、 、 、 、 、 The unit is %; (4) Confidence improvement: When When ≤10%, the analysis and evaluation is completed; when When the rate is greater than 10%, optimize the detection plan.

2. The method for evaluating the uncertainty of quantitative analysis of ions in oilfield water according to claim 1, characterized in that: The oilfield water matrix factor The calculation of is as follows: = in, is the slope of the standard curve of the matrix-free solution; is the slope of the standard curve containing matrix solution; The matrix-free solution and the matrix-containing solution are prepared by the following method: two sets of target ion standard sample solutions with the same concentration gradient are prepared using ultrapure water and oilfield water samples, namely the matrix-free solution and the matrix-containing solution; a standard curve is drawn with the concentration of the target ion standard sample as the abscissa and the instrument detector response signal value as the ordinate; the response signal value is the peak area, peak height or absorbance.

3. The method for evaluating the uncertainty of quantitative analysis of oilfield water ions according to claim 2, wherein: The ion cross interference coefficient The calculation formula is: = ; in, and The calibration method is as follows: Use ultrapure water to prepare Solution, keep Add interfering ions at constant concentration The solution is respectively referred to as solution and solution , and the response signal values ​​are detected by instruments and recorded as and .

4. The method for evaluating the uncertainty of quantitative analysis of ions in oilfield water according to claim 3, wherein: The relative uncertainty of the instrument error The calculation of is as follows: ； in, The first The concentration value of the test, is the number of detections, for The average value of the detections, 、 The unit is mg / L; is the relative expanded uncertainty given in the instrument calibration certificate, in %; , is the inclusion factor, dimensionless.

5. The method for evaluating the uncertainty of quantitative analysis of ions in oilfield water according to claim 3, characterized in that: The relative uncertainty of the sample state stability The calculation of is as follows: = in, The time interval between oilfield water sampling and testing, in hours; is the standard deviation of the relative concentration change rate of the target ion in the oilfield water sample or equivalent stability simulation solution, in h -1 ; is the number of detections in the time series, ≥5; described Calculated by the following steps: (S1) After the oilfield water sample is collected or the equivalent stability simulation solution is prepared, the same target ion is analyzed according to the time sequence. Detection times to obtain time-concentration data points; (S2) The concentration change rate of two adjacent time points in the time series , unit is h -1 ,in, 、 It is the concentration value obtained by testing at two adjacent time points, in mg / L; for The average value of 、 is the time between two adjacent time points, in h; is the average change rate of concentration at two adjacent time points, The average value of K Values ​​range from 2 to ; (S3) = 。 6. The method for evaluating the uncertainty of quantitative analysis of ions in oilfield water according to claim 3, characterized in that: The relative uncertainty of the dilution error is The calculation of is as follows: = in, is the volume distribution factor, which characterizes the volume distribution uniformity of the oilfield water sample during dilution and is dimensionless; is the number of dilutions, dimensionless; is the concentration of the target ion in the blank solution, in mg / L; is the concentration of the target ion in the measurement solution, in mg / L; is the relative standard deviation of the target ion concentration in the blank solution, in %; described is the relative standard deviation of the synthetic volume, in %, which is calculated as follows: is the capacity error, is the nominal volume, and The units are consistent, Indicates a capacity device; For capacity instruments The inclusion factor of The volume distribution factor The value of is based on the viscosity of the water sample at 25℃, and the value is as follows: 5 mPa·s, =1.0; when 5 mPa·s Viscosity 8 mPa·s, γ =1.2; when the solution has precipitation or the viscosity is greater than 8 mPa·s, =1.

7.

7. The method for evaluating the uncertainty of quantitative analysis of ions in oilfield water according to claim 3, characterized in that: The relative uncertainty of the cross-interference between ions The calculation of is as follows: =| K ab | is the inter-ion interference coefficient, dimensionless; Target ions in oilfield water samples The concentration is in mg / L; Interfering ions in oilfield water samples The concentration is in mg / L.

8. The method for evaluating the uncertainty of quantitative analysis of ions in oilfield water according to claim 3, characterized in that: The relative uncertainty of the matrix effect The calculation of is as follows: 。 9. The method for evaluating the uncertainty of quantitative analysis of ions in oilfield water according to claim 1, characterized in that: The optimized detection scheme includes at least one of the following methods: increasing the number of repeated detections; shortening the time interval from sampling to detection; using high-precision detection equipment; and adding ion interference inhibitors.

10. A system for evaluating the uncertainty of quantitative analysis of ions in oilfield water, characterized by: The system is used to implement the uncertainty assessment method for quantitative analysis of oilfield water ions according to any one of claims 1 to 9, and includes the following modules connected in sequence: (1) Data acquisition module: used to collect data; (2) Data analysis module: used to analyze the collected data; (3) Result calculation module: used to calculate the total relative uncertainty , total relative uncertainty The calculation model is = in, is the relative uncertainty of instrument error, is the relative uncertainty of sample state stability, is the relative uncertainty of the dilution error, is the relative uncertainty of cross-interference between ions, is the relative uncertainty of matrix effect, 、 、 、 、 、 The unit is %; (4) Confidence Enhancement Module: When When ≤10%, the analysis and evaluation is completed; when When the rate is greater than 10%, optimize the detection plan.

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