Quantitative analysis method for volume ratio of oil-based pollutants in cable sampling under oil-based drilling fluid condition

Abstract

The invention relates to a quantitative analysis method for the volume ratio of oil-based pollutants in cable sampling under the condition of oil-based drilling fluid. The quantitative analysis method comprises the following steps: establishing a quantitative relation curve between the volume of white oil and the peak height of UCM of specific retention time in the white oil; calculating the volume of the white oil in the cable sampling solution according to the peak height of the UCM of the specific retention time in the white oil contained in the cable sampling solution and the quantitative relation curve; and calculating the volume ratio of the white oil in the cable sample according to the volume of the white oil in the cable sample solution. According to the quantitative analysis method provided by the invention, the problem that the oil-based pollutants are difficult to accurately quantify on a drilling site is effectively avoided, and the accuracy and the reliability of a quantitative result are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of geochemical logging, and particularly relates to a quantitative analysis method for the volume ratio of oil-based contaminants in cable sampling under oil-based drilling fluid conditions. Background Art

[0002] Compared with water-based drilling fluids, oil-based drilling fluids have some significant advantages in drilling engineering, and are particularly suitable for drilling operations in horizontal wells of shale oil and gas and complex geological conditions. At present, they have been widely used in exploration wells and development wells in onshore and offshore oil and gas basins. Nevertheless, due to the particularity of the chemical composition of oil-based drilling fluids, white oil is often mixed in formation test fluid samples, which brings interference to the evaluation of reservoir fluid types during the exploration stage.

[0003] Currently, the quantitative evaluation of the content of oil-based contaminants in cable sampling contaminated by oil-based drilling fluids is mainly based on the internal standard method of gas chromatography, and all are based on certain assumptions. For example, when choosing isoparaffin as the internal standard, it is assumed that the information of the contaminated crude oil is known; when choosing n-paraffin as the internal standard, it is assumed that the n-paraffin in the contaminated crude oil follows a normal distribution. However, during wellsite testing under oil-based drilling fluid conditions, the information of reservoir crude oil is unknown, and its n-paraffin distribution does not all follow a normal distribution. The internal standards selected in the existing two internal standard chromatography methods based on assumptions are mainly alkanes, and the base oils in oil-based drilling fluids all come from refined crude oil, and these compounds exist in both crude oil and base oil. Although the background area of the internal standard peak contributed by crude oil is considered for deduction, due to the unknown original composition and proportion of crude oil during the wellsite testing process, it is difficult to determine the deducted background area of the internal standard. In addition, the wellsite in the offshore oil and gas basin does not have a stable weighing environment, and it is difficult to accurately quantify the mass of the formation fluid mixture contaminated by oil-based drilling fluids. Moreover, there are significant differences in the injection methods between the pyrolysis gas chromatograph used at the wellsite and the conventional gas chromatograph in the laboratory. These factors make it difficult to specifically implement the existing quantitative methods for oil-based contaminants in cable formation test samples at the wellsite.

[0004] Therefore, there is an urgent need to establish a method that does not require prerequisite assumptions and is suitable for quickly evaluating the volume ratio of oil-based contaminants in cable sampling at the wellsite, so as to provide a timely decision-making basis for the evaluation of reservoir fluid types and oil testing. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a quantitative analysis method for the volume ratio of oil-based contaminants in cable sampling under oil-based drilling fluid conditions. Compared with the existing technology, the present invention is mainly applied to quickly quantitatively evaluate the degree of contamination of cable sampling by oil-based drilling fluids at the wellsite, and is also applicable to related research in the laboratory. Combining the pyrolysis analysis values of unit volume cable sampling and oil-based contaminants can further achieve the mass quantification of oil-based contaminants at the wellsite.

[0006] To achieve the object of the present invention, the following technical solutions are adopted in the present invention:

[0007] The present invention provides a quantitative analysis method for the volume ratio of oil-based contaminants in cable sampling under oil-based drilling fluid conditions. The quantitative analysis method includes the following steps:

[0008] S1, preparing an oil-free sandstone powder sample;

[0009] S2, injecting a white oil contaminant standard solution, a first standard substance solution, and a second standard substance solution into the oil-free sandstone powder sample described in step S1, then performing pyrolysis gas chromatography analysis and quantifying the peak height of the unresolved complex mixture (UCM) with a specific retention time in the white oil, and establishing a quantitative relationship curve between the volume of white oil and the peak height of the UCM with a specific retention time in the white oil;

[0010] S3, injecting a cable sampling solution and a first standard substance solution into the oil-free sandstone powder sample described in step S1, then performing pyrolysis gas chromatography analysis and quantifying the peak height of the UCM with a specific retention time in the white oil, and calculating the volume of white oil in the cable sampling solution according to the quantitative relationship curve obtained in step S2;

[0011] S4, calculating the volume ratio of white oil in the cable sampling according to the volume of white oil in the cable sampling solution obtained in step S3.

[0012] In the quantitative analysis method provided by the present invention, the amount of white oil contaminants in the cable sampling is characterized by volume concentration, avoiding the problem that the quality cannot be accurately quantified at the drilling site. At the same time, by using 1-tetradecene and nC 14 The UCM corresponding to the retention time as the internal standard for white oil contaminants can effectively overcome the problem of internal standard superposition caused by the widespread coexistence of separable hydrocarbon compounds in both crude oil and white oil in existing analysis methods.

[0013] In the present invention, the unresolved complex mixture (UCM) in the white oil refers to a hydrocarbon mixture in the white oil that is difficult to be completely separated by conventional gas chromatography methods. It is mainly naphthenic hydrocarbon compounds. In the gas chromatogram, the UCM appears as a continuous "hump" or "bulge". Specifically, the carbon number range of the n-alkanes in the white oil after being circulated into the well in the oil-based drilling fluid is nC9 to nC 22 , where, nC 14 ~nC 16 are the main components of the n-alkanes, and nC 14 is the main peak. The UCM bulge is mainly located between nC 13 ~nC 17 and is mainly based on nC14 and the peak of the bulge in the adjacent area shows an asymmetric, broad and gentle uplift shape.

[0014] It should be noted that the hydrocarbon fluid sample contaminated by oil-based drilling fluid obtained by wellsite cable sampling is a mixture of formation crude oil and white oil filtered into the formation. Its apparent characteristics are no different from those of crude oil. When the proportion of white oil in the mixture is relatively high, the pyrolysis chromatogram characteristics are similar to those of white oil. There is no distinguishable characteristic internal standard in the pyrolysis gas chromatogram of white oil that is significantly different from crude oil, while its unseparated complex mixture (UCM) in the form of a bulge or uplift is significantly different from crude oil. Therefore, according to the UCM peak type characteristics of the present invention and the compound types with retention times in the vicinity of nC published in previous literature 14 nearby, nC 14 and the UCM within the retention time corresponding to 1-tetradecene that elutes earlier than and immediately adjacent to nC 14 are selected as the internal standard for characterizing white oil, and a quantitative relationship curve is established based on the correlation between the volume of white oil and the chromatographic peak height of the UCM internal standard. Then, this quantitative curve is used to calculate the volume proportion of white oil pollutants in the cable sampling contaminated by oil-based drilling fluid.

[0015] Preferably, the method for preparing the oil-free sandstone powder sample in step S1 includes:

[0016] The sandstone powder sample is successively crushed, screened and heated, and then pyrolysis gas chromatography analysis is carried out. If no compound peak appears in the chromatogram, the obtained sample is an oil-free sandstone powder sample.

[0017] Preferably, the first standard substance solution in step S2 is used to calibrate the UCM and the carbon number of n-alkanes in white oil.

[0018] Preferably, the first standard substance solution includes a carbon disulfide solution of 1-tetradecene.

[0019] Preferably, the second standard substance solution in step S2 is used to calibrate the carbon number of n-alkanes in white oil.

[0020] Preferably, the second standard substance solution includes a carbon disulfide solution of 1-hexadecene.

[0021] In the present invention, the carbon number of n-alkanes in the white oil pollutant is determined according to the elution times of 1-tetradecene and 1-hexadecene, wherein the elution time of nC 14 is immediately adjacent to and later than that of 1-tetradecene, and the elution time of nC 16 is immediately adjacent to and later than that of 1-hexadecene.

[0022] Preferably, the method for preparing the standard solution of white oil pollutants in step S2 includes:

[0023] Extract the white oil after the in-well circulation. Take the oil-based drilling fluid for centrifugation. After centrifugation, take the floating white oil on the surface layer and put it into a headspace vial for gas chromatography-mass spectrometry. In different sealed headspace vials for gas chromatography-mass spectrometry, prepare carbon disulfide standard solutions of white oil pollutants with volume concentrations of 2%, 4%, 6%, 8%, and 10% respectively, that is, the white oil pollutant standard solutions.

[0024] Preferably, the process of pyrolysis gas chromatography analysis described in step S2 includes:

[0025] S21, Take standard solutions of white oil pollutants with different volume concentrations, and inject them into the oil-free sandstone powder samples in the pyrolysis gas chromatography crucible together with the first standard substance solution and the second standard substance solution respectively for pyrolysis gas chromatography analysis;

[0026] S22, After the analysis, use chromatographic data processing software to process the chromatograms corresponding to the standard solutions of white oil pollutants with different volume concentrations, and quantify the peak height of 1-tetradecene, the peak height of nC 14 , the total peak height of 1-tetradecene and UCM within its corresponding retention time, and the total peak height of nC 14 and UCM within its corresponding retention time;

[0027] S23, Use the difference in peak height to calculate the peak height of UCM within the corresponding retention time of 1-tetradecene and the peak height of UCM within the corresponding retention time of nC 14 ;

[0028] S24, Analyze the correlation between the peak height of UCM within the corresponding retention time of 1-tetradecene and the peak height of UCM within the corresponding retention time of nC 14 under the conditions of standard solutions of white oil pollutants with different volume concentrations, and establish a quantitative relationship curve between the volume of white oil and the peak height of UCM at a specific retention time in white oil.

[0029] Preferably, the quantitative relationship curve described in step S2 includes Curve 1 and Curve 2.

[0030] Preferably, Curve 1 is expressed as: V 白油 =a×H 1-十四碳烯 +b;

[0031] wherein, V 白油 represents the volume of white oil; H 1-十四碳烯 represents the peak height of UCM within the corresponding retention time of 1-tetradecene in white oil; a represents the slope of Curve 1; b represents the intercept of Curve 1 on the y-axis.

[0032] Preferably, Curve 2 is expressed as: V 白油 =c×H nC14 +d;

[0033] wherein, V白油 represents the volume of white oil; H nC14 represents nC in white oil 14 the peak height of UCM at the corresponding retention time; c represents the slope of Curve 2; d represents the y-axis intercept of Curve 2.

[0034] Preferably, the correlation coefficient R of Curve 1 and Curve 2 2 > 0.99.

[0035] Preferably, the process of pyrolysis gas chromatography analysis in step S3 includes:

[0036] S31, Inject the cable sampling solution and the first standard substance solution into the oil-free sandstone powder sample in the pyrolysis gas chromatography crucible for pyrolysis gas chromatography analysis;

[0037] In the present invention, since 1-tetradecene and 1-hexadecene have been used multiple times to determine the peak emergence times of nC 14 and nC 16 during the process of pyrolysis gas chromatography analysis in the aforementioned step S2, and the subsequent pyrolysis chromatography analyses all adopt the same analysis conditions, the peak emergence positions of the compounds in the chromatogram obtained in step S3 are similar to those in the chromatogram obtained in step S2. Therefore, there is no need to add a second standard substance solution during the injection in step S3;

[0038] S32, After the analysis, use chromatographic data processing software to process the chromatogram, and quantify the peak height of 1-tetradecene, the peak height of nC 14 the total peak height of 1-tetradecene and UCM at its corresponding retention time, and the total peak height of nC 14 and UCM at its corresponding retention time;

[0039] S33, Use the peak height difference to calculate the peak height of UCM at the corresponding retention time of 1-tetradecene and the peak height of UCM at the corresponding retention time of nC 14 ;

[0040] S34, Substitute the peak height obtained in step S33 into the quantitative relationship curve obtained in step S2 to calculate the volume of white oil in the cable sampling solution.

[0041] Preferably, the calculation method of the volume percentage of white oil in the cable sampling in step S4 includes:

[0042] S41, Substitute the volume of white oil in the cable sampling solution obtained in step S3 into the formula:

[0043] where K represents the percentage of the volume of white oil in the cable sampling, that is, the mixture of white oil and crude oil, with the unit of %; V 白油 represents the peak height of UCM at the corresponding retention time of 1-tetradecene or nC14 The volume of white oil determined by the peak height of UCM within the corresponding retention time, in μL; m is the volume of the cable sampling solution, i.e., the volume of the mixture solution of white oil and crude oil, in μL; n is the concentration of the cable sampling solution, i.e., the volume concentration of the mixture of white oil and crude oil, in %.

[0044] S42, when there is a UCM in the crude oil of the exploration area that overlaps with the UCM of white oil within the corresponding retention time of 1-tetradecene, and based on the peak height of the UCM within the corresponding retention time of 1-tetradecene and nC 14 When the volume percentage of white oil in the cable sampling, i.e., the mixture of white oil and crude oil, calculated based on the peak height of the UCM within the corresponding retention time is < 30%, for the peak height of the UCM within the corresponding retention time of 1-tetradecene in the chromatogram of the cable sampling and nC 14 Deduct the background UCM peak height of the crude oil from the peak height of the UCM within the corresponding retention time, and recalculate the volume percentage of white oil. The final result is based on the volume percentage of white oil calculated based on the peak height of the UCM within the corresponding retention time of nC 14 The volume percentage of white oil calculated based on the peak height of the UCM within the corresponding retention time shall prevail;

[0045] In the present invention, the UCM in the crude oil that overlaps with the UCM of white oil generally refers to the unresolved complex mixtures in the crude oil. This UCM is similar to the UCM in white oil and is a hydrocarbon mixture that is difficult to be completely separated by conventional gas chromatography methods, mainly naphthenic compounds; when the proportion of white oil in the cable sampling is low and there is a background UCM within the corresponding retention time of 1-tetradecene and nC in the crude oil 14 When there is a background UCM within the corresponding retention time, its contribution to the peak height of the UCM within the corresponding retention time of 1-tetradecene in the cable sampling and nC 14 The contribution of the peak height of the UCM within the corresponding retention time will cause the relative error of the quantitative result of the volume percentage of white oil to be relatively large. Therefore, it is necessary to deduct the background UCM peak height of the crude oil from the cable sampling;

[0046] When the volume percentage of white oil calculated based on the peak height of the UCM within the corresponding retention time of 1-tetradecene and nC 14 is 30% - 100%, there is no need to deduct the background UCM peak height;

[0047] In the present invention, due to the 1-tetradecene and nC in the cable sampling and the crude oil 14Superposition of UCM within the corresponding retention time, so it is necessary to deduct the peak height of the background UCM of the crude oil. Specific deduction methods can be, for example: obtaining a reference chromatogram from the same type of uncontaminated crude oil in the exploration area, and the reference chromatogram can be obtained by pyrolysis gas chromatography analysis of the crude oil from production wells or oil-bearing cuttings under early water-based drilling fluid conditions; according to the distribution range of the UCM of white oil in the chromatogram, select the area between nC9 and nC 10 in the reference chromatogram, and select the starting retention time of the isoparaffin peak with a peak height similar to that of the UCM within the corresponding retention time of 1-tetradecene or nC 14 in the crude oil in this area as the marking point; in the chromatogram of cable sampling, find the peak height corresponding to the starting retention time of the above marking point, and then subtract the peak height of the marking point from the peak height of the UCM within the corresponding retention time of 1-tetradecene in the cable sampling chromatogram or the peak height of the UCM within the corresponding retention time of nC 14 to complete the deduction of the peak height of the background UCM of the crude oil;

[0048] When the proportion of white oil volume calculated based on the peak height of the UCM within the corresponding retention time of 1-tetradecene and the peak height of the UCM within the corresponding retention time of nC 14 is 30% - 50%, the average value calculated by the two is used as the proportion of white oil volume;

[0049] When the proportion of white oil volume calculated based on the peak height of the UCM within the corresponding retention time of 1-tetradecene and the peak height of the UCM within the corresponding retention time of nC 14 is > 50%, the proportion of white oil volume calculated based on the peak height of the UCM within the corresponding retention time of 1-tetradecene shall prevail.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] (1) The quantitative analysis method provided by the present invention is applicable to various types of non-biodegradable crude oils, without any prerequisite assumptions about the original hydrocarbon composition of the contaminated crude oil and its changing trend, which conforms to the actual situation that the underground crude oil information is unknown during the drilling process.

[0052] (2) The present invention conducts the liquid preparation operation in a sealed chromatographic headspace vial, which can effectively avoid the volatilization of crude oil and organic solvents, thus ensuring the stability of the standard solution and the cable sampling dilution solution.

[0053] (3) The present invention uses volume concentration to characterize the content of white oil pollutants in cable sampling, avoiding the problem that it is difficult to accurately quantify white oil pollutants in an unstable weighing environment at the drilling site, especially on an offshore drilling platform, and can further realize the conversion of the mass proportion of oil-based pollutants at the well site through the pyrolysis analysis of white oil pollutants per unit volume and cable sampling, ensuring the universality of this method in the laboratory and at the well site.

[0054] (4) The white oil used for establishing the quantitative curve of white oil pollutants in the quantitative analysis method provided by the present invention is the white oil after the actual drilling circulation before the target layer is entered in the well site, ensuring the representativeness of the white oil used for establishing the quantitative curve of white oil pollutants.

[0055] (5) The present invention uses 1-tetradecene and nC 14 UCM within the corresponding retention time is used as the internal standard for characterizing white oil, which maximally overcomes the problem of the superposition of corresponding internal standards caused by the common presence of separable hydrocarbon compounds in both crude oil and white oil, improving the accuracy and reliability of quantitative analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 is the pyrolysis gas chromatogram of a 1 μL carbon disulfide solution of white oil with a volume concentration of 10% in Example 1 of the present invention;

[0057] Figure 2 is the pyrolysis gas chromatogram of a 1 μL carbon disulfide solution of light crude oil with a volume concentration of 20% in Example 1 of the present invention;

[0058] Figure 3 is the pyrolysis gas chromatogram of a 1 μL carbon disulfide solution of the actual cable sample from the well site with a volume concentration of 10% added with 1 μL carbon disulfide solution of 1-tetradecene with a volume concentration of 6‰ in the specific implementation manner of the present invention;

[0059] Figure 4 is the pyrolysis gas chromatogram of a 1 μL carbon disulfide solution of a mixture of white oil and crude oil with a volume concentration of 10% after well entry circulation with different volume ratios and a 1 μL carbon disulfide solution of 1-tetradecene with a volume concentration of 6‰ in Example 1 of the present invention; wherein, (a) the volume ratio of white oil to crude oil after well entry circulation is 1:9, (b) the volume ratio of white oil to crude oil after well entry circulation is 2:8, (c) the volume ratio of white oil to crude oil after well entry circulation is 3:7, (d) the volume ratio of white oil to crude oil after well entry circulation is 4:6, (e) the volume ratio of white oil to crude oil after well entry circulation is 5:5, (f) the volume ratio of white oil to crude oil after well entry circulation is 6:4, (g) the volume ratio of white oil to crude oil after well entry circulation is 7:3, (h) the volume ratio of white oil to crude oil after well entry circulation is 8:2, (i) the volume ratio of white oil to crude oil after well entry circulation is 9:1;

[0060] Figure 5 is the pyrolysis gas chromatogram of a 1 μL carbon disulfide solution of white oil with a volume concentration of 10% in Example 1 of the present invention added with 1 μL carbon disulfide solution of 1-tetradecene with a volume concentration of 6‰ and 1 μL carbon disulfide solution of 1-hexadecene with a volume concentration of 6‰;

[0061] Figure 6 (a) is the quantitative relationship curve established based on the UCM peak height within the corresponding retention time of 1-tetradecene in Example 1 of the present invention; Figure 6 (b) is based on nC in Example 1 of the present invention 14 The quantitative relationship curve established based on the UCM peak height within the corresponding retention time;

[0062] Figure 7 is the relative error graph of the white oil volume ratio determined by the UCM peak height within the corresponding retention time of 1-tetradecene and the UCM peak height within the corresponding retention time of nC in Example 1 of the present invention 14 ;

[0063] Figure 8 is the partially enlarged pyrolysis chromatogram of the uncontaminated crude oil of the same type as the crude oil contained in the cable sample provided in Example 1 of the present invention;

[0064] Figure 9 is the flow chart of the quantitative analysis method in Example 1 of the present invention. Detailed Embodiments

[0065] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0066] In the following embodiments, the experimental methods without special instructions are all conventional methods. The materials and reagents used can be obtained from commercial channels without additional instructions.

[0067] In a specific embodiment, the present invention provides a quantitative analysis method for the volume ratio of oil-based contaminants in cable sampling under oil-based drilling fluid conditions.

[0068] Since the normal alkane carbon number range of white oil in the oil-based drilling fluid after in-well circulation is nC9 to nC 22 , where, nC 14 ~nC 16 is the main component of normal alkanes, and nC 14 is the main peak, and the UCM bulge is mainly located between nC 13 ~nC 17 and shows an asymmetrically broad and gentle bulge with the peak of the bulge at nC 14 and adjacent regions (as shown in Figure 1 ); the hydrocarbon fluid sample contaminated by the oil-based drilling fluid obtained by cable sampling at the well site is a mixture of formation crude oil and white oil filtered into the formation, and its apparent characteristics are indistinguishable from those of crude oil. When the proportion of white oil in the mixture is relatively high, its pyrolysis chromatogram characteristics are similar to those of white oil (as shown in Figure 1 and Figure 3) Since the true value of the volume or mass ratio of the white oil contaminated object is unknown and cannot be accurately measured by existing methods, in this specific embodiment, an uncontaminated light crude oil produced from the main target layer in the study area and the white oil separated from the drilling fluid after in-well circulation are used to prepare a mixed sample with a known volume ratio (such as Figure 4 shown) to simulate the sampling of contaminated cables under oil-based drilling fluid conditions. The highest carbon number of n-alkanes in the light crude oil used can reach nC 33 , which basically covers the carbon number distribution of n-alkanes in white oil (such as Figure 2 shown). The simulation shows that the pyrolysis chromatogram of the mixed sample with a higher volume ratio of white oil is similar to the actual sample of cable sampling under oil-based drilling fluid conditions (such as Figure 3 and Figure 4 (i)), that is, the mixed sample prepared from the light crude oil and the separated white oil used in this specific embodiment is representative.

[0069] The quantitative analysis method includes the following steps, as Figure 9 shown:

[0070] S1. Prepare an oil-free sandstone powder sample;

[0071] S2. Inject the white oil pollutant standard solution, the first standard substance solution, and the second standard substance solution into the oil-free sandstone powder sample described in step S1, then perform pyrolysis gas chromatography analysis and quantify the peak height of the unseparated complex mixture, i.e., UCM, at a specific retention time in the white oil, and establish a quantitative relationship curve between the volume of white oil and the peak height of UCM at a specific retention time in the white oil;

[0072] S3. Inject the cable sampling solution and the first standard substance solution into the oil-free sandstone powder sample described in step S1, then perform pyrolysis gas chromatography analysis and quantify the peak height of UCM at a specific retention time in the white oil, and calculate the volume of white oil in the cable sampling solution according to the quantitative relationship curve obtained in step S2;

[0073] S4. Calculate the volume ratio of white oil in the cable sampling according to the volume of white oil in the cable sampling solution obtained in step S3.

[0074] In the quantitative analysis method provided by the present invention, the amount of white oil pollutants in the cable sampling is characterized by volume concentration, avoiding the problem that the quality cannot be accurately quantified at the drilling site. At the same time, by using UCM at the corresponding retention times of 1-tetradecene and nC 14 as the internal standard for white oil pollutants, the problem of internal standard superposition caused by the common coexistence of separable hydrocarbon compounds in both crude oil and white oil in existing analysis methods can be effectively overcome.

[0075] It should be noted that the hydrocarbon fluid sample contaminated by oil-based drilling fluid obtained by wellsite cable sampling is a mixture of formation crude oil and white oil percolated into the formation. Its apparent characteristics are indistinguishable from those of crude oil. When the proportion of white oil in the mixture is relatively high, the pyrolysis chromatogram characteristics are similar to those of white oil. There are no distinguishable characteristic internal standards in the pyrolysis gas chromatogram of white oil that are significantly different from crude oil (such as Figure 1 and Figure 2 shown), while its unseparated complex mixture (UCM) in the form of bulges or uplifts is significantly different from crude oil (such as Figure 1 and Figure 2 shown). Therefore, according to the peak shape characteristics of UCM and the types of compounds with retention times near nC 14 in the literature published by predecessors, this invention selects the UCM within the retention time corresponding to nC 14 and 1-tetradecene that elutes earlier than and immediately adjacent to nC 14 as the internal standard for characterizing white oil, and establishes a quantitative relationship curve based on the correlation between the volume of white oil and the chromatographic peak height of the UCM internal standard. Then, this quantitative curve is used to calculate the volume proportion of white oil pollutants in the cable sampling contaminated by oil-based drilling fluid.

[0076] In some of these embodiments, the method for preparing the oil-free sandstone powder sample described in step S1 includes:

[0077] The sandstone powder sample is successively crushed, screened, and heated, and then pyrolysis gas chromatography analysis is performed. If no compound peaks appear in the chromatogram, the resulting sample is an oil-free sandstone powder sample.

[0078] In some of these embodiments, the first standard substance solution described in step S2 is used to calibrate the UCM and the carbon number of n-alkanes in white oil.

[0079] In some of these embodiments, the first standard substance solution includes a carbon disulfide solution of 1-tetradecene.

[0080] In some of these embodiments, the second standard substance solution described in step S2 is used to calibrate the carbon number of n-alkanes in white oil.

[0081] In some of these embodiments, the second standard substance solution includes a carbon disulfide solution of 1-hexadecene.

[0082] In some of these embodiments, the method for preparing the white oil pollutant standard solution described in step S2 includes:

[0083] Extract the white oil after the in - well circulation. Take the oil - based drilling fluid for centrifugation. After centrifugation, take the floating white oil on the surface layer and put it into a headspace vial for gas chromatography - mass spectrometry. In different sealed headspace vials for gas chromatography - mass spectrometry, prepare carbon disulfide standard solutions of white oil pollutants with volume concentrations of 2%, 4%, 6%, 8% and 10% respectively, that is, the white oil pollutant standard solutions.

[0084] In some of these embodiments, the process of pyrolysis gas chromatography analysis in step S2 includes:

[0085] S21, Take standard solutions of white oil pollutants with different volume concentrations, and inject them into the oil - free sandstone powder samples in the pyrolysis gas chromatography crucible together with the first standard substance solution and the second standard substance solution respectively for pyrolysis gas chromatography analysis;

[0086] S22, After the analysis, use chromatographic data processing software to process the chromatograms corresponding to the standard solutions of white oil pollutants with different volume concentrations, and quantify the peak height of 1 - tetradecene, the peak height of nC 14 the total peak height of 1 - tetradecene and UCM within its corresponding retention time, and the total peak height of nC 14 and UCM within its corresponding retention time;

[0087] S23, Use the difference in peak height to calculate the peak height of UCM within the corresponding retention time of 1 - tetradecene and the peak height of UCM within the corresponding retention time of nC 14 ;

[0088] S24, Analyze the correlation between the peak height of UCM within the corresponding retention time of 1 - tetradecene and the peak height of UCM within the corresponding retention time of nC under the conditions of standard solutions of white oil pollutants with different volume concentrations, and establish a quantitative relationship curve between the volume of white oil and the peak height of UCM at a specific retention time in white oil. 14 ;

[0089] In some of these embodiments, the quantitative relationship curve in step S2 includes Curve 1 and Curve 2.

[0090] In some of these embodiments, Curve 1 is expressed as: V 白油 =a×H 1-十四碳烯 +b;

[0091] wherein, V 白油 represents the volume of white oil; H 1-十四碳烯 represents the peak height of UCM within the corresponding retention time of 1 - tetradecene in white oil; a represents the slope of Curve 1; b represents the intercept of Curve 1 on the y - axis.

[0092] In some of these embodiments, Curve 2 is expressed as: V 白油 =c×H nC14 +d;

[0093] Among them, V 白油 Indicates the volume of white oil; H nC14 Indicates nC in white oil 14 The peak height of UCM within the corresponding retention time; c represents the slope of curve 2; d represents the intercept of curve 2 on the y-axis.

[0094] In some embodiments, the correlation coefficient R between the first curve and the second curve is 2 >0.99.

[0095] In some embodiments, the process of pyrolysis gas chromatography analysis in step S3 includes:

[0096] S31, injecting the cable sampling solution and the first standard substance solution into the oil-free sandstone powder sample in the pyrolysis gas chromatography crucible, and performing pyrolysis gas chromatography analysis;

[0097] S32, after the analysis, the chromatogram is processed using chromatography data processing software to quantify the peak height, nC 14 The peak height of 1-tetradecene and the total peak height of UCM at the corresponding retention time, and nC 14 and the total peak height of UCM within its corresponding retention time;

[0098] S33, using the peak height difference, calculate the peak height and nC of UCM at the corresponding retention time of 1-tetradecene 14 The peak height of UCM within the corresponding retention time;

[0099] S34, substituting the peak height obtained in step S33 into the quantitative relationship curve obtained in step S2 to calculate the volume of white oil in the cable sampling solution.

[0100] In some embodiments, the method for calculating the volume percentage of white oil in the cable sampling in step S4 includes:

[0101] S41, substituting the volume of white oil in the cable sampling solution obtained in step S3 into the formula:

[0102] Where K represents the percentage of white oil volume in the cable sample, i.e. the mixture of white oil and crude oil, in %; V 白油 It is indicated by the UCM peak height or nC corresponding to the retention time of 1-tetradecene 14 The volume of white oil determined by the UCM peak height during the corresponding retention time is in μL; m is the volume of the cable sampling solution, i.e., the volume of the mixture of white oil and crude oil, in μL; n is the concentration of the cable sampling solution, i.e., the volume concentration of the mixture of white oil and crude oil, in %;

[0103] S42. When there is a UCM in the corresponding retention time of 1-tetradecene in the crude oil of the exploration formation that overlaps with the UCM of white oil, and based on the peak height of the UCM in the corresponding retention time of 1-tetradecene and the peak height of the UCM in the corresponding retention time of nC 14 When the volume percentage of white oil in the cable sampling, that is, the mixture of white oil and crude oil, calculated based on the peak height of the UCM in the corresponding retention time of 1-tetradecene and the peak height of the UCM in the corresponding retention time of nC 14 is less than 30%, the peak height of the UCM in the corresponding retention time of 1-tetradecene in the chromatogram of the cable sampling is deducted from the background UCM peak height of the crude oil, and the volume percentage of white oil is recalculated. The final result is based on the volume percentage of white oil calculated according to the peak height of the UCM in the corresponding retention time of nC 14 ;

[0104] In the present invention, due to the superposition of the UCM of the cable sampling with the 1-tetradecene and nC of the crude oil 14 in the corresponding retention time, it is necessary to deduct the background UCM peak height of the crude oil. Specifically, the deduction method can be, for example: obtaining a reference chromatogram from the same type of uncontaminated crude oil in the exploration area, and the reference chromatogram can be obtained by pyrolysis gas chromatography analysis of the crude oil from production wells or oil-bearing cuttings under early water-based drilling fluid conditions; according to the distribution range of the UCM of white oil in the chromatogram, selecting the area between nC9 and nC 10 in the reference chromatogram, and selecting the starting retention time of the isoparaffin peak with a peak height similar to that of the UCM in the corresponding retention time of 1-tetradecene or nC in the crude oil in this area as the marking point; in the chromatogram of the cable sampling, finding the peak height corresponding to the starting retention time of the above marking point, and then subtracting the peak height of the UCM in the corresponding retention time of 1-tetradecene in the cable sampling chromatogram or the peak height of the UCM in the corresponding retention time of nC 14 from the peak height of this marking point, so as to complete the deduction of the background UCM peak height of the crude oil; 14 ;

[0105] When the volume percentage of white oil calculated based on the peak height of the UCM in the corresponding retention time of 1-tetradecene and the peak height of the UCM in the corresponding retention time of nC 14 is 30% - 100%, there is no need to deduct the background UCM peak height;

[0106] When the volume percentage of white oil calculated based on the peak height of the UCM in the corresponding retention time of 1-tetradecene and the peak height of the UCM in the corresponding retention time of nC 14 is 30% - 50%, the average value calculated by the two is used as the volume percentage of white oil;

[0107] When the volume percentage of white oil calculated based on the peak height of the UCM in the corresponding retention time of 1-tetradecene and the peak height of the UCM in the corresponding retention time of nC 14When the proportion of white oil volume calculated from the peak height of UCM within the corresponding retention time > 50%, the proportion of white oil volume calculated from the peak height of UCM within the retention time of 1-tetradecene shall prevail.

[0108] The following further illustrates the composition of the technical solution of the present invention through Example 1.

[0109] Example 1

[0110] This example provides a quantitative analysis method for the volume proportion of oil-based contaminants in cable sampling under oil-based drilling fluid conditions, as Figure 9 shown, the quantitative analysis method includes the following steps:

[0111] S1. Prepare a sandstone powder sample without oil, specifically including: passing the crushed sandstone powder sample through a combined sample sieve of 110 mesh and 250 mesh, collecting the remaining fine sandstone powder sample in the 250-mesh sieve, then dispersing these powders on a high-temperature resistance heating furnace for heating at a temperature of 850 °C, and then weighing about 30 mg of the heated and well-mixed fine sandstone sample powder for pyrolysis gas chromatography analysis; if chromatographic peaks appear on the pyrolysis chromatogram, the sample needs to be heated again until no compound peaks appear on the pyrolysis chromatogram.

[0112] It should be noted that before performing the pyrolysis gas chromatography analysis in steps S2 and S3, it is necessary to select appropriate injection volumes of crude oil, white oil, and reference substances (1-tetradecene, 1-hexadecene), and determine the carbon numbers of each compound in the pyrolysis chromatograms of white oil and cable sampling:

[0113] ① Considering the volatile characteristics of carbon disulfide and light crude oil, 100 μL and 10 μL pointed gas chromatography micro-injection needles are used. Without opening the lid, the pointed gas chromatography micro-injection needle is used to pierce into the headspace vial of the chromatograph to prepare carbon disulfide solutions of light crude oil with volume concentrations of 10% and 20% and carbon disulfide solutions of white oil with volume concentrations of 10% and 20% respectively, and shake well; after shaking well, use a 10 μL pointed gas chromatography micro-injection needle to pierce into the capped headspace injection vial to extract 1 μL of the prepared solution and quickly inject it into about 30 mg of oil-free fine sandstone powder placed in a crucible for pyrolysis gas chromatography analysis; after the analysis is completed, according to the resolution of nC 17 and pristane in light crude oil with different concentrations, and the symmetry of the single peaks of n-alkanes with higher abundances in light crude oil and white oil to determine the appropriate injection volume. In this example, after analysis, under the conditions that the flow rate of the pyrolysis gas chromatography split port is 50 mL / min and the injection volume is 1 μL, when the volume concentrations of white oil and light crude oil are 10%, 20% and below respectively, the chromatographic peaks of each compound generally maintain good symmetry, and their nC 17It has a high resolution with pristane (Pr) (such as Figure 1 and Figure 2 shown).

[0114] ② Determine the injection volumes of 1 - tetradecene and 1 - hexadecene. First, prepare carbon disulfide solutions of 1 - tetradecene with a volume concentration of 10% and 1 - hexadecene with a volume concentration of 10%. The liquid - preparation method is the same as in ①. Dilute them into carbon disulfide solutions with volume concentrations of 2‰, 4‰, 6‰, and 8‰ respectively. Use a pointed gas - chromatographic micro - injection needle to separately extract 1 μL of the above standard - substance solutions for pyrolysis chromatographic analysis. The injection method is the same as in ①. Then, compare the peak heights of 1 - tetradecene and 1 - hexadecene at different concentrations with the peak heights of nC 14 and nC 16 in white oil with a volume concentration of 10% and light crude oil with a volume concentration of 20%. And select the standard - substance solutions with appropriate peak - height corresponding concentrations and the carbon disulfide solution of white oil with a volume concentration of 10% to conduct pyrolysis chromatographic analysis again by co - injection. Finally, comprehensively consider the relative peak - height magnitudes and resolutions between 1 - tetradecene and nC 14 as well as between 1 - hexadecene and nC 16 to finally determine the appropriate injection concentration. Under the instrument conditions of this embodiment, select an injection volume of 1 μL of a solution with a volume concentration of 6‰ as the injection volume of the standard substance. Under this injection - volume condition, the peak heights of 1 - tetradecene and 1 - hexadecene are close to the peak heights of nC 14 and nC 16 respectively and maintain a good resolution (such as Figure 5 shown).

[0115] S2. Inject the white - oil pollutant standard solution, the first standard - substance solution, and the second standard - substance solution into the oil - free sandstone powder sample described in step S1, then conduct pyrolysis gas - chromatographic analysis and quantify the peak height of the unseparated complex mixture, i.e., UCM, at a specific retention time in the white oil, and establish a quantitative relationship curve between the volume of the white oil and the peak height of the UCM at a specific retention time in the white oil;

[0116] Among them, the preparation method of the white - oil pollutant standard solution specifically includes: Extract the white oil after in - well circulation. Use a pipette to transfer 10 mL of the oil - based drilling fluid near the target layer into a plastic centrifuge tube for centrifugation. Then, use a pipette to transfer 1 mL of the white oil floating on the surface after centrifugation into a 1.5 - mL headspace injection vial for gas chromatography - mass spectrometry. Use pointed gas - chromatographic micro - injection needles of 100 μL and 10 μL to prepare carbon disulfide standard solutions of white - oil pollutants with volume concentrations of 2%, 4%, 6%, 8%, and 10%.

[0117] The process of the pyrolysis gas - chromatographic analysis described in step S2 includes:

[0118] S21. Take standard solutions of white oil pollutants with different volume concentrations, and inject them into the oil-free sandstone powder samples in the pyrolysis gas chromatography crucible together with the first standard substance solution and the second standard substance solution respectively for pyrolysis gas chromatography analysis.

[0119] That is, use a 10 μL pointed gas chromatography microsyringe to extract 1 μL of the standard solution of white oil pollutants with a volume concentration of 2%, the carbon disulfide solution of 1-tetradecene with a volume concentration of 6‰, and the carbon disulfide solution of 1-hexadecene with a volume concentration of 6‰ respectively, and quickly inject them into about 30 mg of oil-free sandstone powder samples placed in the crucible. Immediately conduct pyrolysis gas chromatography analysis on the oil-free sandstone powder samples injected with these solutions; the analysis method for the standard solutions of white oil pollutants with other volume concentrations is the same as above.

[0120] S22. After the analysis is completed, calibrate the carbon number of n-alkanes in the chromatogram based on the peak positions of 1-tetradecene and 1-hexadecene, and use chromatographic data processing software to process the chromatograms corresponding to the standard solutions of white oil pollutants with different volume concentrations, and quantify the peak height of 1-tetradecene, the peak height of nC 14 , the total peak height of 1-tetradecene and UCM within its corresponding retention time, and the total peak height of nC 14 and UCM within its corresponding retention time. The pyrolysis gas chromatogram co-injected with 1 μL of the standard solution of white oil pollutants with a volume concentration of 10%, 1 μL of the carbon disulfide solution of 1-tetradecene with a volume concentration of 6‰, and 1 μL of the carbon disulfide solution of 1-hexadecene with a volume concentration of 6‰ is as Figure 5 shown.

[0121] S23. Use the difference in peak height to calculate the peak height of UCM within the corresponding retention time of 1-tetradecene and the peak height of UCM within the corresponding retention time of nC 14 .

[0122] S24. Analyze the correlation between the peak height of UCM within the corresponding retention time of 1-tetradecene and the peak height of UCM within the corresponding retention time of nC 14 under the conditions of standard solutions of white oil pollutants with different volume concentrations and the volume of white oil, and establish a quantitative relationship curve between the volume of white oil and the peak height of UCM at a specific retention time in white oil (as Figure 6 shown).

[0123] S3. Inject the cable sampling solution and the first standard substance solution into the oil-free sandstone powder sample described in step S1, then conduct pyrolysis gas chromatography analysis and quantify the peak height of UCM at a specific retention time in white oil, and calculate the volume of white oil in the cable sampling solution according to the quantitative relationship curve obtained in step S2.

[0124] In this embodiment, a mixture of light crude oil and white oil is used to simulate cable sampling. The same liquid preparation method as in ① is adopted. Using a 100 μL pointed gas chromatography micro-injection needle, mixed liquids of white oil and crude oil with volume ratios of 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, and 9:1 are prepared. After shaking well, the above-mentioned mixed liquids with different volume ratios are diluted into corresponding carbon disulfide solutions with a volume concentration of 10% using a 100 μL pointed gas chromatography micro-injection needle, and a simulated cable sampling solution is obtained.

[0125] The process of the pyrolysis gas chromatography analysis described in step S3 includes:

[0126] S31, Inject the cable sampling solution and the first standard substance solution into the oil-free sandstone powder sample in the pyrolysis gas chromatography crucible for pyrolysis gas chromatography analysis.

[0127] Using a 10 μL pointed gas chromatography micro-injection needle, 1 μL of the cable sampling solution with a volume concentration of 10% (the volume ratio of light crude oil to white oil is 1:9) and 1 μL of the carbon disulfide solution of 1-tetradecene with a volume concentration of 6‰ are respectively extracted and quickly injected into about 30 mg of oil-free fine sandstone powder placed in the crucible, and pyrolysis gas chromatography analysis is carried out in a timely manner; the analysis methods for cable sampling solutions with other volume ratios are the same as above. The pyrolysis gas chromatography diagrams of mixed liquids with different volume ratios are as Figure 4 shown.

[0128] S32, After the analysis is completed, use chromatographic data processing software to process the chromatogram, and quantify the peak height of 1-tetradecene, the peak height of nC 14 , the total peak height of 1-tetradecene and UCM within its corresponding retention time, and the total peak height of nC 14 and UCM within its corresponding retention time.

[0129] S33, Use the peak height difference to calculate the peak height of UCM within the corresponding retention time of 1-tetradecene and the peak height of UCM within the corresponding retention time of nC 14 .

[0130] S34, Substitute the peak height obtained in step S33 into the quantitative relationship curve obtained in step S2 to calculate the volume of white oil in the cable sampling solution.

[0131] S4, Calculate the volume percentage of white oil in the cable sampling according to the volume of white oil in the cable sampling solution obtained in step S3.

[0132] S41, Substitute the volume of white oil in the cable sampling solution obtained in step S3 into the formula:

[0133] Wherein, K represents the percentage of the volume of white oil in the cable sample, i.e., the mixture of white oil and crude oil, with the unit of %; V 白油 represents the volume of white oil determined by the peak height of UCM within the retention time corresponding to 1-tetradecene or the peak height of UCM within the retention time corresponding to nC 14 The unit is μL; m is the volume of the cable sampling solution, i.e., the volume of the carbon disulfide solution of the mixture of white oil and light crude oil extracted by a chromatographic microsyringe, with the unit of μL; n is the volume concentration of the cable sampling solution, i.e., the volume concentration of the mixture of white oil and light crude oil in the cable sampling solution, with the unit of %;

[0134] Taking the example of using a 10 μL pointed gas chromatographic microsyringe to extract 1 μL of the cable sampling solution with a volume concentration of 10% in step S3, wherein, m = 1, n = 10%, the simplified formula is:

[0135] In this embodiment, the proportion of white oil calculated from the peak height of UCM within the retention time corresponding to 1-tetradecene is shown in Table 1; the proportion of white oil calculated from the peak height of UCM within the retention time corresponding to nC 14 The proportion of white oil calculated from the peak height of UCM within the corresponding retention time is shown in Table 2, and the relative errors are shown in Table 1-2 and Figure 7 as shown.

[0136] Table 1

[0137]

[0138] Table 2

[0139]

[0140] S42. Analysis of Table 1 and Table 2:

[0141] (i) In the formation crude oil of this embodiment, there is an unresolved complex mixture with a low peak height background within the retention time corresponding to 1-tetradecene. When the calculated volume proportion of white oil in the cable sample, i.e., the mixture of white oil and crude oil, < 30%, the contribution of this background UCM peak height to the peak height of UCM within the retention time corresponding to 1-tetradecene in the cable sample and the peak height of UCM within the retention time corresponding to nC 14 The peak height of UCM within the corresponding retention time will cause the relative error of the quantitative result of the volume proportion of the white oil contaminated object to be too large.

[0142] Due to the overlap of the UCM peaks within the retention times corresponding to 1-tetradecene and nC 14 in the cable sampling chromatogram with the background UCM peak of crude oil (as shown in Figure 4 ), it is impossible to directly determine the background UCM peak height to be deducted in this figure. Therefore, it is necessary to rely on other easily identifiable compounds in the crude oil that are not affected by UCM in the white oil to determine the background peak height to be deducted. The pyrolysis chromatogram of the same type of crude oil not contaminated by white oil in the exploration area is as shown inFigure 8 As shown in Figure 8 , in Figure 8 , a parallel line to the baseline is drawn through the highest peak of the UCM at the corresponding retention time of 1-tetradecene, and other UCM compound peaks with the same height as this parallel line are found (such as the compound peak marked as X in 14 ), and its starting retention time is used as the marking point. Since the UCM compounds within the corresponding retention time of 1-tetradecene and nC 14 in the exploration area are adjacent and usually have the same highest peak height, the peak height of the crude oil background UCM to be deducted in cable sampling is also the same. In the chromatogram of cable sampling, the peak height corresponding to the starting retention time of this marking point is found, and the peak height of the UCM within the corresponding retention time of 1-tetradecene or nC

[0143] in the cable sampling chromatogram is subtracted by the peak height of this marking point, thus completing the deduction of the peak height of the crude oil background UCM. 14 However, even after deducting the background peak height, the relative error of the white oil proportion calculated based on the UCM peak height within the corresponding retention time of 1-tetradecene is still > 5%, while the compounds within the corresponding retention time of nC 14 are relatively single, and the relative error of the white oil proportion calculated from the UCM peak height within the corresponding retention time of nC 14 after deducting the background is within 5%. Therefore, when the volume proportion of white oil < 30%, the white oil proportion calculated from the UCM peak height within the corresponding retention time of nC

[0144] (ii) When the volume proportion of white oil ≥ 30%, the influence range of the UCM bulge of white oil in the chromatogram has gradually spread to nC9, that is, within this range of white oil volume proportion, it is no longer possible to deduct the UCM background peak height of crude oil from the UCM peak heights of 1-tetradecene and nC 14 within the corresponding retention time.

[0145] (iii) When the volume proportion of white oil is between 30% and 50%, the average value of the white oil volume proportion calculated from the UCM peak height within the corresponding retention time of 1-tetradecene and the white oil volume proportion calculated from the UCM peak height within the corresponding retention time of nC 14 can be taken as the result.

[0146] (iv) When the white oil volume proportion calculated from the UCM peak height within the corresponding retention time of 1-tetradecene and the UCM peak height within the corresponding retention time of nC 14 > 50%, the white oil volume proportion calculated from the UCM peak height within the corresponding retention time of 1-tetradecene shall prevail.

[0147] In summary, the quantitative analysis method provided by the present invention uses volume concentration to characterize the amount of white oil pollutants in cable sampling, and uses 1-tetradecene and nC14 The UCM within the corresponding retention time is used as the internal standard for white oil pollutants, effectively avoiding the problem of difficult to accurately quantify oil-based pollutants at the drilling site and improving the accuracy and reliability of the quantification results.

[0148] The applicant declares that the above description is only a specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A quantitative analysis method for the volume proportion of oil-based contaminants in cable sampling under oil-based drilling fluid conditions, characterized in that The quantitative analysis method comprises the following steps: S1. Prepare an oil-free sandstone powder sample; S2. Inject a white oil pollutant standard solution, a first standard substance solution and a second standard substance solution into the oil-free sandstone powder sample described in step S1, then perform pyrolysis gas chromatography analysis and quantify the peak height of the unseparated complex mixture, i.e., UCM, at a specific retention time in the white oil, and establish a quantitative relationship curve between the volume of white oil and the peak height of UCM at a specific retention time in the white oil; S3. Inject a cable sampling solution and a first standard substance solution into the oil-free sandstone powder sample described in step S1, then perform pyrolysis gas chromatography analysis and quantify the peak height of UCM at a specific retention time in the white oil, and calculate the volume of white oil in the cable sampling solution according to the quantitative relationship curve obtained in step S2; S4. Calculate the volume percentage of white oil in the cable sampling according to the volume of white oil in the cable sampling solution obtained in step S3.

2. The quantitative analysis method according to claim 1, characterized in that The preparation method of the oil-free sandstone powder sample described in step S1 includes: Crush, screen and heat the sandstone powder sample in sequence, then perform pyrolysis gas chromatography analysis. If no compound peak appears in the chromatogram, the obtained sample is the oil-free sandstone powder sample.

3. The quantitative analysis method according to claim 1 or 2, characterized in that The first standard substance solution described in step S2 is used to calibrate the UCM and the carbon number of n-alkanes in the white oil; Preferably, the first standard substance solution includes a carbon disulfide solution of 1-tetradecene.

4. The quantitative analysis method according to any one of claims 1-3, characterized in that, The second standard substance solution described in step S2 is used to calibrate the carbon number of n-alkanes in the white oil; Preferably, the second standard substance solution includes a carbon disulfide solution of 1-hexadecene.

5. The quantitative analysis method according to any one of claims 1-4, characterized in that, The preparation method of the white oil pollutant standard solution described in step S2 includes: Extract the white oil after in-well circulation, take the oil-based drilling fluid for centrifugation, and take the floating white oil on the surface layer after centrifugation into a headspace injection vial for chromatograph-mass spectrometer. Respectively prepare carbon disulfide standard solutions of white oil pollutants with volume concentrations of 2%, 4%, 6%, 8% and 10% in different sealed headspace vials for chromatograph-mass spectrometer, i.e., the white oil pollutant standard solution.

6. The quantitative analysis method according to any one of claims 1-5, characterized in that, The process of the pyrolysis gas chromatography analysis described in step S2 includes: S21. Take white oil pollutant standard solutions with different volume concentrations, and respectively inject them together with the first standard substance solution and the second standard substance solution into the oil-free sandstone powder sample in a pyrolysis gas chromatography crucible for pyrolysis gas chromatography analysis; S22, after the analysis, use chromatographic data processing software to process the chromatograms corresponding to white oil pollutant standard solutions with different volume concentrations, and quantify the peak height of 1-tetradecene, the peak height of nC 14 , the total peak height of 1-tetradecene and UCM within its corresponding retention time, and the total peak height of nC 14 and UCM within its corresponding retention time; S23, taking the difference in peak heights, calculate the peak height of UCM and nC within the retention time corresponding to 1-tetradecene 14 at the retention time corresponding to the peak height of UCM; S24. Analyze the peak height of UCM and nC within the corresponding retention time of 1-tetradecene under the conditions of white oil pollutant standard solutions with different volume concentrations, 14 establish the correlation between the peak height of UCM within the corresponding retention time and the volume of white oil, and establish a quantitative relationship curve between the volume of white oil and the peak height of UCM at a specific retention time in white oil.

7. The quantitative analysis method according to claim 6, wherein The quantitative relationship curve described in step S2 includes Curve 1 and Curve 2; Preferably, the first curve is expressed as: V 白油 = a × H 1-十四碳烯 + b; Among them, V 白油 represents the volume of white oil; H 1-十四碳烯 represents the peak height of UCM within the retention time corresponding to 1-tetradecene in white oil; a represents the slope of Curve 1; b represents the intercept of Curve 1 on the y-axis; Preferably, the second curve is expressed as: V 白油 = c × H nC14 + d; Among them, V 白油 Indicates the volume of white oil; H nC14 Indicates nC in white oil 14 The peak height of UCM within the corresponding retention time; c represents the slope of curve 2; d represents the intercept of curve 2 on the y-axis.

8. The quantitative analysis method according to claim 7, wherein The correlation coefficient R of the first curve and the second curve 2 > 0.

99.

9. The quantitative analysis method according to any one of claims 1-8, characterized in that, The process of the pyrolysis gas chromatography analysis described in step S3 includes: S31. Inject the cable sampling solution and the first standard substance solution into the oil-free sandstone powder sample in a pyrolysis gas chromatography crucible for pyrolysis gas chromatography analysis; S32, after the analysis, use chromatographic data processing software to process the chromatogram, and quantify the peak height of 1-tetradecene, the peak height of nC 14 , the total peak height of 1-tetradecene and UCM within its corresponding retention time, and the total peak height of nC 14 and UCM within its corresponding retention time; In S33, the peak height difference is used to calculate the peak height of UCM and nC within the retention time corresponding to 1-tetradecene 14 at the retention time corresponding to it; S34. Substitute the peak height obtained in step S33 into the quantitative relationship curve obtained in step S2 to calculate the volume of white oil in the cable sampling solution.

10. The quantitative analysis method according to any one of claims 1-9, characterized in that, The calculation method of the volume percentage of white oil in the cable sampling described in step S4 includes: S41. Substitute the volume of white oil in the cable sampling solution obtained in step S3 into the formula: Among them, K represents the percentage of the volume of white oil in the cable sample, that is, the mixture of white oil and crude oil, with the unit of %; V 白油 represents the volume of white oil determined by the peak height of the UCM within the retention time corresponding to 1-tetradecene or the peak height of the UCM within the retention time corresponding to nC 14 The unit is μL; m is the volume of the cable sampling solution, that is, the volume of the mixture solution of white oil and crude oil, with the unit of μL; n is the concentration of the cable sampling solution, that is, the volume concentration of the mixture of white oil and crude oil, with the unit of %; S42. When there is a UCM overlapping with that of white oil within the retention time corresponding to 1-tetradecene in the crude oil of the exploration formation, and when the volume percentage of white oil in the cable sampling, i.e., the mixture of white oil and crude oil, calculated based on the peak height of the UCM within the retention time corresponding to 1-tetradecene and the peak height of the UCM within the corresponding retention time of nC 14 is less than 30%, the peak height of the UCM within the retention time corresponding to 1-tetradecene in the chromatogram of the cable sampling and the peak height of the UCM within the corresponding retention time of nC 14 are used to deduct the background UCM peak height of the crude oil, and the volume percentage of white oil is recalculated. The final result is based on the volume percentage of white oil calculated according to the peak height of the UCM within the corresponding retention time of nC 14 corresponding retention time; When the proportion of white oil volume calculated based on the peak height of UCM within the corresponding retention time of 1-tetradecene and the peak height of UCM within the corresponding retention time is 30% to 100%, there is no need to deduct the background UCM peak height; 14 When the proportion of white oil volume calculated based on the peak height of UCM within the corresponding retention time of 1-tetradecene and the peak height of UCM within the corresponding retention time is 30% to 100%, there is no need to deduct the background UCM peak height; When the proportion of white oil volume calculated based on the peak height of UCM within the corresponding retention time of 1-tetradecene and the peak height of UCM within the corresponding retention time is 30% - 50%, the average value calculated from the two is used as the proportion of white oil volume; 14 When the proportion of white oil volume calculated based on the peak height of UCM within the corresponding retention time of 1-tetradecene and the peak height of UCM within the corresponding retention time is 30% - 50%, the average value calculated from the two is used as the proportion of white oil volume; When the proportion of white oil volume calculated based on the peak height of UCM within the retention time corresponding to 1-tetradecene and nC 14 When the proportion of white oil volume calculated based on the peak height of UCM within the corresponding retention time > 50%, the proportion of white oil volume calculated based on the peak height of UCM within the retention time corresponding to 1-tetradecene shall prevail.

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