An evaluation method and system for uncertainty of oilfield water ion quantitative analysis

Abstract

This invention discloses a method and system for assessing the uncertainty of quantitative analysis of ions in oilfield water. The assessment method includes the following steps: (1) data collection; (2) data analysis: based on the data collected in step (1), analyze the properties of the oilfield water sample and determine the key parameters for calculation. The key parameters include the oilfield water matrix factor, the inter-ion cross-interference coefficient, and the units of both are dimensionless; (3) result calculation: calculate the total relative uncertainty; (4) confidence enhancement: when ≤10%, the analysis and assessment end; when >10%, optimize the detection scheme. The method provided by this invention is specifically designed for the characteristics of high concentration gradient and complex matrix in oilfield water, taking into account the inter-ion cross-interference and matrix effect, thus improving the accuracy of uncertainty assessment; by introducing the sample state stability uncertainty assessment, the traceability of the original state of the sample is improved.

Description

Technical Field

[0001] This invention belongs to the field of water analysis and detection technology, specifically relating to a method and system for evaluating the uncertainty of quantitative analysis of water ions in oilfields with complex high-concentration water bodies. Background Technology

[0002] Uncertainty assessment is a crucial indicator of the reliability of measurement results. In water analysis and testing, the traditional GUM method for uncertainty assessment generally assumes that the sample has uniform concentration, simple composition, and stable state. Based on a linear measurement model, it treats uncertainty as the sum of the standard deviations of various influencing factors. It typically only assesses the error of the testing instrument and at the time of measurement, without considering the dynamic changes in the characteristics and state of the water itself, making the test results largely insignificant for characterizing and tracing the original state of the sample. Oilfield water often contains high concentrations of different ions, such as chloride to sulfate ion ratios reaching 50:1 and sodium to potassium ion ratios reaching 200:1. These ions may also interfere with each other, such as through competitive reactions, enhanced matrix effects, and overlapping detection signals. Therefore, errors caused by changes in the water sample's state, matrix effects, inter-ion interference, and sample pretreatment are more significant. Furthermore, traditional uncertainty assessment methods are time-consuming, have slow feedback, and are inefficient. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention proposes a method for assessing the uncertainty of quantitative analysis of ions in oilfield water. This method incorporates considerations of the matrix characteristics of the oilfield water itself, variations 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 assessment calculation system is constructed, significantly reducing the time required for manual assessment and calculation of uncertainty in oilfield water ion analysis. The uncertainty assessment of the detection results allows for the inversion and evaluation of the original state of the water sample.

[0004] A method for evaluating the uncertainty of quantitative analysis of water ions in oilfields, characterized by the following steps:

[0005] (1) Data collection: including: physicochemical characteristic parameters of oilfield water samples, test results of quality control samples and calibration parameters of testing instruments; among which, the physicochemical characteristic parameters of oilfield water samples should at least include pH value, total dissolved solids and ion content;

[0006] (2) Data analysis: Based on the data collected in step (1), analyze the properties of the oilfield water sample and determine the key parameters for calculation. The key parameters include the oilfield water matrix factor. Inter-ion cross-interference coefficient , and All units are dimensionless;

[0007] (3) Calculation of results: Calculate the total relative uncertainty. ,

[0008] =

[0009] in, The relative uncertainty of instrument error, The relative uncertainty of the sample's state stability. The relative uncertainty of the dilution error, The relative uncertainty of inter-ion cross-interference. The relative uncertainty of the matrix effect, , , , , , All units are %;

[0010] (4) Confidence boost: when The analysis and evaluation are concluded when the percentage is ≤10%; when... If the percentage is greater than 10%, optimize the detection plan.

[0011] Preferably, the oilfield water matrix factor The calculation is as follows:

[0012] =

[0013] in, The slope of the matrix-free solution standard curve; The slope of the standard curve containing the matrix solution;

[0014] The matrix-free and matrix-containing solutions are prepared as follows: two sets of target ion standard sample solutions with the same concentration gradient are prepared using ultrapure water and oilfield water samples, namely matrix-free solution and matrix-containing solution; a standard curve is plotted 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.

[0015] Preferably, the ion cross-interference coefficient K ab The calculation formula is: = ;

[0016] in, and The calibration method is as follows: Prepare solutions containing only the target ions using ultrapure water. The solution, maintain Adding interfering ions while keeping the concentration constant The solutions are respectively denoted as solutions. and solution The response signal values ​​were detected by the instrument and recorded as follows: and .

[0017] Preferably, the relative uncertainty of the instrument error The calculation is as follows:

[0018] ;

[0019] in, The first standard solution of the target ion The concentration value was measured once; Number of tests for The average value of the tests. , The unit is mg / L; The relative expanded uncertainty is given in the instrument calibration certificate, in percentages (%). , is the inclusion factor, which is dimensionless.

[0020] Preferably, the relative uncertainty of the sample state stability The calculation is as follows:

[0021] =

[0022] in, The time interval between oilfield water sample collection and testing is expressed in hours (h). The standard deviation of the relative concentration change rate of the target ion in an oilfield water sample or equivalent stability simulation solution, expressed in hours. -1 ; The number of detections in the time series. ≥5;

[0023] The standard deviation of the relative concentration change rate of the target ion in actual oilfield water samples or equivalent stability simulation solutions The following steps are used to calculate:

[0024] (S1) After the oilfield water sample collection is completed or the equivalent stability simulation solution is prepared, the same target ion is subjected to the time series described above. The second test yielded time-concentration data points;

[0025] (S2) The rate of concentration change between two adjacent time points in the time series The unit is h -1 ,in, , The values ​​are the concentrations obtained at two adjacent time points, in mg / L. for The average value; , The time is between two adjacent time points, in hours (h). The average rate of change of concentration at two adjacent time points is taken as... The average value; K Values ​​from 2 to ;

[0026] (S3) = .

[0027] Preferably, the relative uncertainty of the dilution error The calculation is as follows:

[0028] =

[0029] in, The volume distribution factor characterizes the uniformity of volume distribution during the dilution process of oilfield water samples and is dimensionless. The number of dilutions is dimensionless. The concentration of the target ion in the blank solution is expressed in mg / L. The concentration of the target ion in the measurement solution is expressed in mg / L. The relative standard deviation of the target ion detection concentration in the blank solution is expressed in % (%).

[0030] The The relative standard deviation of the synthesis volume, expressed as a percentage, is calculated as follows:

[0031]

[0032] For capacity error, Nominal volume and The units are consistent. Instruments indicating capacity; For capacity instruments The inclusion factor;

[0033] The volume distribution factor The value is determined based on the viscosity of the water sample at 25℃, and is as follows: when viscosity At 5 mPa·s, =1.0; when 5 mPa·s Viscosity At 8 mPa·s, c=1.2; when the solution has precipitation or viscosity >8 mPa·s, =1.7.

[0034] Preferably, the relative uncertainty of the inter-ion cross-interference The calculation is as follows:

[0035] =| K ab |

[0036] The inter-ion interference coefficient is dimensionless. Target ions in oilfield water samples The concentration is expressed in mg / L. Interfering ions in oilfield water samples The concentration is expressed in mg / L.

[0037] Preferably, the relative uncertainty of the matrix effect The calculation is as follows:

[0038] .

[0039] Preferably, the optimized detection scheme includes at least one of the following methods: increasing the number of repeated detections; shortening the time interval between sampling and detection to reduce the influence of sample state instability; using high-precision detection equipment; and adding ion interference inhibitors to eliminate specific ion interferences.

[0040] A system for evaluating the uncertainty of quantitative analysis of water ions in oilfields, the system being used to execute the method for evaluating the uncertainty of quantitative analysis of water ions in oilfields as described in this invention, comprising the following modules connected in sequence:

[0041] (1) Data acquisition module: used to acquire data;

[0042] (2) Data parsing module: used to parse the collected data;

[0043] (3) Results calculation module: used to calculate the total relative uncertainty. Total relative uncertainty The calculation model is

[0044] =

[0045] in, The relative uncertainty of instrument error, The relative uncertainty of the sample's state stability. The relative uncertainty of the dilution error, is the relative uncertainty of interionic cross-interference, is the relative uncertainty of matrix effect, 、 、 、 、 、 The units of are all %;

[0046] (4)Confidence level improvement module: When ≤10%, the analysis and evaluation end; When >10%, optimize the detection scheme.

[0047] Preferably, in the present invention, the properties of oilfield water samples are analyzed according to the following criteria:

[0048] TDS≤5000mg / L, the oilfield water sample is fresh water with low salinity;

[0049] 5000 mg / L<TDS≤50000 mg / L, the oilfield water sample is formation water with medium salinity;

[0050] 50000mg / L<TDS≤150000 mg / L, the oilfield water sample is produced water with high salinity;

[0051] TDS>150000 mg / L, the oilfield water sample is high-salt and hydrogen sulfide and organic acid water.

[0052] The common interionic cross-interferences in the art are as follows:

[0053] 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+ 。

[0054] The beneficial effects of the present invention:

[0055] 1. In view of the characteristics of high concentration gradient and complex matrix of oilfield water, special consideration was given to the cross-interference between ions and matrix effect, which improved the accuracy of uncertainty assessment;

[0056] 2. By introducing an assessment of the uncertainty of sample state stability, the traceability of the original state of the sample is improved;

[0057] 3. The system has achieved automated assessment, which greatly shortens the assessment time and improves efficiency;

[0058] 4. When the uncertainty is large, the system can automatically provide optimization solutions to improve the confidence of the detection results. Detailed Implementation

[0059] Example 1

[0060] Taking the uncertainty assessment of quantitative analysis of water ions produced from a carbon dioxide sequestration oil well in an oilfield as an example:

[0061] Step 1: Collect the following data according to the requirements of the uncertainty components:

[0062]

[0063] Quality control sample test results:

[0064] a. Instrument error related data: Take Cl - Quality control sample, i.e. Cl - The standard solution (concentration of 12000 mg / L) was subjected to repeatability testing 10 times (i.e., =10), resulting in 10 measurements. to (Unit: mg / L) The values ​​were: 12010, 11980, 12050, 12020, 11990, 12030, 12000, 12040, 11970, 12060, representing the average of 10 measurements. The concentration was 12015 mg / L; the relative expanded uncertainty of the ion chromatograph calibration was also obtained from the instrument calibration certificate. =1%, ;

[0065] b. Sample 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 according to the time series (0h, 4h, 8h, 24h, 48h). - The standard solution was measured 5 times (i.e. =5), the concentration measurements (in mg / L) were: 12000, 11985, 11960, 11940, 11920;

[0066] c. Data related to the dilution process: The oilfield water sample was diluted 1000 times before testing (using 1000... Using an L-type pipette, transfer 1 mL of sample to a 1000 mL volumetric flask and dilute to volume. The volumetric error of the pipette is obtained from the calibration certificate. -10 μL (following a normal distribution, the pipette's coverage factor) = ); Capacity error of volumetric flasks The coverage factor of the volumetric flask is +0.4 mL (satisfying the triangular distribution). = ); Ultrapure water was used as the blank solution, and the Cl in the ultrapure water - concentration =0.1 mg / L, 10 tests, relative standard deviation of blank solution. =10%;

[0067] d. Data related to inter-ion cross-interference: Through experimental calibration, Cl... - Interference coefficient with other ions Dimensionless:

[0068] With Cl - with Fe 3+ For example, The calculation process is as follows:

[0069] Step 1: Prepare two solutions using ultrapure water:

[0070] solution Contains only Cl - Ion concentration: 11273.65 mg / L;

[0071] solution Contains Cl - Ions 11273.65 mg / L and Fe 3+ Ion concentration: 1601.15 mg / L;

[0072] Step 2: Solution and solution After dilution 1000 times, Cl was detected under the same chromatographic conditions. - The conductivity response signal value:

[0073] solution Peak area = 2.523

[0074] solution Peak area =2.503

[0075] Step 3: Calculate the interference coefficient:

[0076] = ( - ) / = (2.503-2.523) / 2.523 = -0.0080;

[0077] Using the same method, the calculation results for other interference coefficients are as follows:

[0078] Cl - With SO4 2- : =0.001;

[0079] Cl - With HCO3 - : =0.002;

[0080] Cl - With Ca 2+ : =0.005;

[0081] e. Matrix effect related data: Using the standard addition method, two sets of target ion Cl- concentration gradients were prepared using ultrapure water and the oilfield water sample, respectively. - The standard sample solutions were prepared as matrix-free and matrix-containing solutions, respectively, with Cl... - Concentration gradient of standard samples (in mg / L): 0, 2500, 5000, 7500, 10000, 12500, 15000; peak area (in mg / L) is plotted on the x-axis as the concentration of the target ion standard sample. Using the ordinate as the vertical axis, two standard curves were obtained through linear fitting for the matrix-free solution and the matrix-containing solution, respectively. The slopes of the two standard curves are as follows:

[0082] Matrix-free solution: slope = 0.95;

[0083] With matrix solution: slope =0.98;

[0084] Matrix effect factor: = = 0.95 / 0.98 = 0.9694;

[0085] Step 2, Data Analysis:

[0086] Matrix type identification: TDS = 17945.86 mg / L, therefore the oilfield water sample belongs to medium-salinity formation water, matrix factor... =0.9694;

[0087] Identification of main interference sources: Determining Cl - The detection is affected by the following interferences:

[0088] SO4 2- ( =1359.78 mg / L, interference coefficient =0.001),

[0089] HCO3 - ( =445.15 mg / L, interference coefficient =0.002),

[0090] Ca 2+ ( =3478.58 mg / L, interference coefficient =0.005),

[0091] Fe 3+ ( =1601.15 mg / L, interference coefficient = -0.008).

[0092] Step 3: Total relative uncertainty calculate:

[0093] (31) Calculation of relative uncertainty of instrument error: based on Cl - Data from 10 measurements of the standard solution = 0.56%;

[0094] (32) Calculation of the relative uncertainty of sample stability:

[0095] = = =11961 mg / L,

[0096] =8 h,

[0097] = =-3.13 h -1 ,

[0098] = =-5.22 h -1 ,

[0099] = =-1.04 h -1 ,

[0100] = =-0.696 h -1 ,

[0101] = =-2.52 h -1 ,

[0102] = =2.105 h -1 ,

[0103] = = 8 =0.0075%;

[0104] (33) Calculation of the relative uncertainty component of the dilution process: This embodiment uses a one-step dilution, i.e. =1; =0.1mg / L, =10%; the oilfield water sample contained sediment, therefore Take 1.7; = 0.71%;

[0105] The Cl content in the oilfield water sample was obtained from the collected data. - The ion concentration was 11273.65 mg / L. After dilution 1000 times, the concentration of the target ion Cl in the solution was measured. - concentration =11.2736 mg / L,

[0106] calculate =

[0107] =1.21%;

[0108] (34) Calculation of the relative uncertainty of cross-interference between ions:

[0109] Regarding Cl - Consider SO4 2- HCO3 - Ca 2+ Fe 3+ Four interfering ions, based on the concentrations and interference coefficients of the interfering ions given in step 2 above, and the target ion Cl in the oilfield water sample. - concentration ( = 11273.65 mg / L), calculate each pair of interfering ion pairs Cl - Cross-interference uncertainty components:

[0110] =| =0.001 =0.29%,

[0111] =| = 0.00 =1.01%,

[0112] =| = 0.005 =0.90%,

[0113] =| = 0.008 =2.12%,

[0114] Then synthesize, so, ;

[0115] (35) Calculation of matrix effect uncertainty:

[0116] = =3.06 ;

[0117] (36) Calculate :

[0118] = =4.19%;

[0119] ≤10%, analysis and evaluation complete.

[0120] Example 2

[0121] A system for evaluating the uncertainty of quantitative analysis of water ions in oilfields, the system being used to execute the method for evaluating the uncertainty of quantitative analysis of water ions in oilfields as described in this invention, specifically comprising the following modules connected in sequence:

[0122] (1) Data acquisition module: used to acquire data;

[0123] (2) Data parsing module: used to parse the collected data;

[0124] (3) Results calculation module: used to calculate the total relative uncertainty. Total relative uncertainty The calculation model is

[0125] =

[0126] in, The relative uncertainty of instrument error, The relative uncertainty of the sample's state stability. The relative uncertainty of the dilution error, The relative uncertainty of inter-ion cross-interference. The relative uncertainty of the matrix effect, , , , , , All units are %;

[0127] (4) Confidence Enhancement Module: When The analysis and evaluation are concluded when the percentage is ≤10%; when... If the percentage is greater than 10%, optimize the detection plan.

[0128] The optimized detection scheme includes at least one of the following methods: increasing the number of repeated detections; shortening the time interval between sampling and detection to reduce the impact of sample state instability; using high-precision detection equipment; and adding ion interference inhibitors to eliminate specific ion interferences.

Claims

1. A method for evaluating the uncertainty of quantitative analysis of water ions in oilfields, characterized in that: Includes the following steps: (1) Data collection: including: physicochemical characteristic parameters of oilfield water samples, test results of quality control samples and calibration parameters of testing instruments; among which, the physicochemical characteristic parameters of oilfield water samples include at least pH value, total dissolved solids and ion content; (2) Data analysis: Based on the data collected in step (1), analyze the properties of the oilfield water sample and determine the key parameters for calculation. The key parameters include the oilfield water matrix factor. and inter-ion cross-interference coefficient , and All units are dimensionless; (3) Calculation of results: Calculate the total relative uncertainty. , = ； in, The relative uncertainty of instrument error, The relative uncertainty of the sample's state stability. The relative uncertainty of the dilution error, The relative uncertainty of inter-ion cross-interference. The relative uncertainty of the matrix effect, , , , , , All units are %; (4) Confidence boost: when The analysis and evaluation are concluded when the percentage is ≤10%; when... When the percentage is greater than 10%, optimize the detection plan; The inter-ion cross-interference coefficient The calculation formula is: = ; in, and The calibration method is as follows: Prepare solutions containing only the target ions using ultrapure water. The solution, maintain Adding interfering ions while keeping the concentration constant The solutions are respectively denoted as solutions. and solution The response signal values ​​were detected by the instrument and recorded as follows: and ; The relative uncertainty of inter-ion cross-interference The calculation is as follows: =| K ab | ； is the cross-interference coefficient between ions, which is dimensionless; Target ions in oilfield water samples The concentration is expressed in mg / L. Interfering ions in oilfield water samples The concentration is expressed in mg / L.

2. The method for evaluating the uncertainty of quantitative analysis of water ions in oilfields according to claim 1, characterized in that: The oilfield water matrix factor The calculation is as follows: = ； in, The slope of the matrix-free solution standard curve; The slope of the standard curve containing the matrix solution; The matrix-free and matrix-containing solutions are prepared as follows: two sets of target ion standard sample solutions with the same concentration gradient are prepared using ultrapure water and oilfield water samples, namely matrix-free solution and matrix-containing solution; a standard curve is plotted 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 water ions in oilfields according to claim 2, characterized in that: The relative uncertainty of the instrument error The calculation is as follows: ； in, The first standard solution of the target ion The concentration value of the second test. Number of tests for The average value of the tests. , The unit is mg / L; The relative expanded uncertainty is given in the instrument calibration certificate, in percentages (%). , is the inclusion factor, which is dimensionless.

4. The method for evaluating the uncertainty of quantitative analysis of water ions in oilfields according to claim 2, characterized in that: The relative uncertainty of the sample state stability The calculation is as follows: = ； in, The time interval between oilfield water sample collection and testing is expressed in hours (h). The standard deviation of the relative concentration change rate of the target ion in an oilfield water sample or equivalent stability simulation solution, expressed in hours. -1 ; The number of detections in the time series. ≥5; The The following steps are used to calculate: (S1) After the oilfield water sample collection is completed or the equivalent stability simulation solution is prepared, the same target ion is subjected to the time series described above. The second test yielded time-concentration data points; (S2) The rate of concentration change between two adjacent time points in the time series The unit is h -1 ,in, , The values ​​are the concentrations obtained at two adjacent time points, in mg / L. for The average value; , The time is between two adjacent time points, in hours (h). The average rate of change of concentration at two adjacent time points is taken as... The average value; K Values ​​from 2 to ; (S3) = 。 5. The method for evaluating the uncertainty of quantitative analysis of water ions in oilfields according to claim 2, characterized in that: The relative uncertainty of the dilution error The calculation is as follows: = ； in, The volume distribution factor characterizes the uniformity of volume distribution during the dilution process of oilfield water samples and is dimensionless. The number of dilutions is dimensionless. The concentration of the target ion in the blank solution is expressed in mg / L. The concentration of the target ion in the measurement solution is expressed in mg / L. The relative standard deviation of the target ion detection concentration in the blank solution is expressed in % (%). The The relative standard deviation of the synthesis volume, expressed as a percentage, is calculated as follows: ； For capacity error, Nominal volume and The units are consistent. Instruments indicating capacity; For capacity instruments The inclusion factor; The volume distribution factor The value is determined based on the viscosity of the water sample at 25℃, and is as follows: when viscosity At 5 mPa·s, =1.0; when 5 mPa·s Viscosity At 8 mPa·s, γ =1.2; when the solution has precipitation or viscosity >8 mPa·s, =1.

7.

6. The method for evaluating the uncertainty of quantitative analysis of water ions in oilfields according to claim 2, characterized in that: The relative uncertainty of the matrix effect The calculation is as follows: 。 7. The method for evaluating the uncertainty of quantitative analysis of water ions in oilfields 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 between sampling and detection; using high-precision detection equipment; and adding ion interference inhibitors.

8. A system for evaluating the uncertainty of quantitative analysis of water ions in oilfields, characterized in that: This system is used to perform the uncertainty assessment method for quantitative analysis of water ions in oilfields as described in any one of claims 1-7, and includes the following modules connected in sequence: (1) Data acquisition module: used to acquire data; (2) Data parsing module: used to parse the collected data; (3) Results calculation module: used to calculate the total relative uncertainty. Total relative uncertainty The calculation model is = ;in, The relative uncertainty of instrument error, The relative uncertainty of the sample's state stability. The relative uncertainty of the dilution error, The relative uncertainty of inter-ion cross-interference. The relative uncertainty of the matrix effect, , , , , , All units are %; (4) Confidence Enhancement Module: When The analysis and evaluation are concluded when the percentage is ≤10%; when... If the percentage is greater than 10%, optimize the detection plan.

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