A method for determining the content of organic pollutants in oil-based drilling fluid in cuttings by using an internal standard method

Abstract

The application discloses a method for determining the content of oil-based drilling fluid organic pollutants in cuttings by using an internal standard method, and steps are as follows: adding an internal standard substance with a fixed proportion to oil-based drilling fluid base oil; cleaning and drying the oil-based drilling fluid contaminated cuttings; taking the cleaned and dried cuttings sample, carrying out rock pyrolysis analysis, and calculating S1+S2; taking the cleaned and dried cuttings sample to carry out rock extract content determination; taking the rock extract to carry out extract family component analysis, and quantitatively determining the content of saturated hydrocarbon, aromatic hydrocarbon, non-hydrocarbon and asphaltene components; using gas chromatography to analyze the saturated hydrocarbon component, and calculating the normalized percentage content of the internal standard substance in the saturated hydrocarbon component; according to the content of the internal standard substance in the saturated hydrocarbon and the proportion of the internal standard substance in the base oil, the content of the base oil in unit rock is calculated; the content of the base oil in unit rock is deducted from the rock pyrolysis analysis result S1+S2, and the corrected S1+S2 result in the formation rock is obtained. The application is simple in operation and accurate in quantification.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of geochemical analysis, in particular to a method for determining the content of organic pollutants in oil-based drilling fluid in cuttings by using an internal standard method. BACKGROUND

[0002] In the process of oil exploration drilling, in order to make the drilling fluid achieve the expected performance, the drilling fluid containing base oil is used, which is easy to contaminate the crude oil and rock samples. When the geochemical experiment analysis is carried out on the contaminated cuttings, the geochemical experimental parameters such as the hydrocarbon generation potential (S1+S2) deviate from the true value of the stratum uncontaminated cuttings, and then the organic matter abundance of the source rock cannot be accurately calculated, and the later exploration and development work cannot be accurately guided.

[0003] At present, the pretreatment of the contaminated cuttings generally adopts organic reagent cleaning to remove the surface contaminated part and obtain the uncontaminated sample. However, the base oil (such as white oil, diesel oil and the like) contains the same normal alkanes, isomeric alkanes, aromatic hydrocarbons and the like components in the stratum rock. Since the organic matters are similar and compatible, it is difficult to completely separate the pollutants through the cleaning treatment, and even the organic matter components of the rock itself can be washed away, so that the accurate geochemical experimental parameters such as the hydrocarbon generation potential cannot be obtained.

[0004] Therefore, it is particularly necessary to establish a method for accurately determining the oil-based mud pollution degree of cuttings in the exploration work, so as to accurately correct the geochemical experimental parameters such as the hydrocarbon generation potential and guide the exploration and evaluation work. SUMMARY

[0005] In order to solve the above technical problems, the application provides a method for determining the content of organic pollutants in oil-based drilling fluid in cuttings by using an internal standard method, which can quantitatively judge the organic pollutants such as base oil immersed in the cuttings.

[0006] The application is realized by adopting the following technical scheme.

[0007] A method for determining the content of organic pollutants in oil-based drilling fluid in cuttings by using an internal standard method, comprising the following steps:

[0008] S1. A fixed proportion of an internal standard is added to the base oil of the oil-based drilling fluid, and the base oil is used for preparing the drilling fluid;

[0009] S2. The oil-based drilling fluid contaminated cuttings are taken, if the surface of the cuttings has sticky oil-based mud pollutants, the oil-based drilling fluid pollutants on the surface of the cuttings are removed by using a cleaning liquid, if the surface of the cuttings has no sticky oil-based mud pollutants, the cuttings are not cleaned, and the cleaned or uncleaned cuttings are dried at low temperature;

[0010] S3. Weigh the dried rock sample, and perform rock pyrolysis analysis according to the standard GB / T 18602-2012 “Rock Pyrolysis Analysis” to obtain the S1+S2 parameter value;

[0011] S4. Quantitatively weigh the dried rock sample in step S2 according to the standard SY / T 5118-2021 “Determination of Extractives in Rocks”, and perform determination of rock extractives content to quantitatively calculate the proportion of rock extractives in rock;

[0012] S5. Quantitatively weigh the rock extractives sample obtained in step S4 according to the standard SY / T 5119-2016 “Analysis of Soluble Organic Matter and Crude Oil Group Components in Rocks”, and quantitatively determine the contents of saturated hydrocarbons, aromatic hydrocarbons, non-hydrocarbons and asphaltene; and perform group component analysis using a base oil sample containing a fixed proportion of internal standard;

[0013] S6. Perform saturated hydrocarbon component gas chromatography analysis according to the standard GB / T 18340.5-2010 “Geological Sample Organic Geochemical Analysis Method Part 5: Analysis of Saturated Hydrocarbons in Rock Extractives and Crude Oil”, and calculate the normalized percentage content of the internal standard in the saturated hydrocarbon component; and determine the proportion of the internal standard in the saturated hydrocarbon in the sample according to the standard method GB / T 18340.5-2010;

[0014] S7. According to the content of the internal standard in the saturated hydrocarbon and its proportion in the base oil, calculate the content W of the base oil in unit mass of rock (mg / g), see formula (1): 基础油

[0015]

[0016] In the formula: W 基础油 : the amount of base oil pollution in unit mass of rock;

[0017] R0: the proportion of internal standard in base oil, %;

[0018] R1: the proportion of rock extractives in rock, %;

[0019] R2: the proportion of saturated hydrocarbon in rock extractives, %;

[0020] R3: the normalized percentage content of internal standard in the saturated hydrocarbon component, %;

[0021] R4: the proportion of internal standard in the saturated hydrocarbon, %;

[0022] S8. Subtract the content of base oil in unit rock from the S1+S2 result in step S3 to obtain the corrected S1+S2 result in the formation rock.

[0023] ​Further, the method is characterized in that the amount of the internal standard added in step S1 is 0.5% to 1%.

[0024] Further, the internal standard in step S1 includes but is not limited to methyl palmitate, and can also be other organic compounds with similar properties.

[0025] Further, in step S2, the cleaning method is as follows: the prepared cleaning solution is added to the oil-based contaminated rock debris, and stirred at 1500 to 2500 revolutions per minute for 10 to 15 minutes, then the rock debris is washed with water until no foam is generated, and dried.

[0026] Further, the cleaning solution includes potassium chloride, sodium bis(2-ethyl ethyl) sulfonate, and water, and the mass ratio of the three is (15 to 25):(5 to 15):(300 to 400).

[0027] The present application has the following beneficial effects.

[0028] The method of the present application adds a fixed proportion of internal standard to base oil, and performs quantitative extraction, group component analysis, and gas chromatography analysis on the rock debris, so that the base oil and other pollutants in the rock debris are quantitatively deducted, and the method is simple to operate and has good feasibility and accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 Figure 1 is a gas chromatogram of base oil white oil of an embodiment of the present application;

[0030] Figure 2 Figure 2 is a gas chromatogram of saturated hydrocarbons of normal uncontaminated rock debris;

[0031] Figure 3 Figure 3 is a gas chromatogram of base oil white oil of the present application after adding an internal standard;

[0032] Figure 4 Figure 4 is a cleaning process diagram of oil-based contaminated rock debris of an embodiment of the present application. DETAILED DESCRIPTION

[0033] The present application is further described below in conjunction with the embodiments.

[0034] The experimental methods used in the following embodiments are conventional methods unless otherwise specified; the materials, reagents, etc. used in the following preparation examples and embodiments can be obtained from commercial channels unless otherwise specified.

[0035] A method for determining the content of oil-based drilling fluid organic pollutants in rock debris by using an internal standard method, comprising the following steps:

[0036] First step, add a fixed proportion (0.5%~1%) of internal standard to the oil-based drilling fluid base oil, the base oil has added other organic additives such as wetting agent, emulsifier, etc., the internal standard is selected but not limited to methyl palmitate, mix the base oil after adding the internal standard uniformly, the base oil is used to prepare drilling fluid;

[0037] Second step, weigh 50~100g of oil-based drilling fluid contaminated rock debris, if the surface of the rock debris has obvious sticky oil-based mud pollutants, use cleaning agent to clean the pollutants on the surface of the rock debris, if there is no obvious sticky oil-based mud pollutants, cleaning can be omitted; dry the cleaned (or uncleaned) rock debris at low temperature;

[0038] Cleaning scheme: to avoid cross contamination, prepare cleaning solution for each sample separately, prepare the cleaning solution according to 400ml of water, 20g of potassium chloride and 10ml of sodium bis(2-ethyl ethyl) sulfonate succinate, after preparation, add oil-based contaminated rock debris, set the stirring speed of the stirrer to 1500~2500 revolutions / minute, stir for 10~15 minutes, then rinse the rock debris with water until there is no foam, dry, see Figure 4 .

[0039] Third step, weigh about 5g of the cleaned and dried rock debris sample, according to the standard rock pyrolysis analysis of GB / T 18602-2012 "Rock Pyrolysis Analysis", obtain the S1+S2 parameter value;

[0040] Fourth step, quantitatively weigh about 20g of the dried rock debris sample in the second step, according to the standard of SY / T 5118-2021 "Determination of Extractives in Rocks", carry out determination of rock extractives content, and quantitatively calculate the proportion of rock extractives in rock;

[0041] Fifth step, quantitatively weigh the rock extractives obtained in the fourth step, according to the standard of SY / T 5119-2016 "Analysis of Soluble Organic Matter and Crude Oil Group Components in Rocks", carry out group component analysis, quantitatively determine the content of four components of saturated hydrocarbon, aromatic hydrocarbon, non-hydrocarbon and asphaltene; use the base oil sample containing a fixed proportion of internal standard to carry out group component analysis;

[0042] Sixth step, according to the standard of GB / T 18340.5-2010 "Geological Sample Organic Geochemical Analysis Method Part 5: Analysis of Saturated Hydrocarbons in Rock Extractives and Crude Oil", carry out saturated hydrocarbon component gas chromatography analysis, calculate the normalized percentage content of the internal standard in the saturated hydrocarbon component, see Figure 3 . At the same time, according to the standard method of the sixth step, determine the proportion of the internal standard in the saturated hydrocarbon in the sample;

[0043] Seventh step, according to the content of the internal standard in the saturated hydrocarbon and its proportion in the base oil, calculate the content W of the base oil in unit mass of rock 基础油(mg / g), see equation (1):

[0044]

[0045] wherein:

[0046] W 基础油 : the amount of base oil pollution in unit mass of rock;

[0047] R0: the proportion of the internal standard in base oil, %;

[0048] R1: the proportion of rock extractives in rock, %;

[0049] R2: the proportion of saturated hydrocarbons in rock extractives, %;

[0050] R3: the normalized percentage content of the internal standard in the saturated hydrocarbon component, %;

[0051] R4: the proportion of the internal standard in saturated hydrocarbons, %;

[0052] In the eighth step, the content of base oil in unit rock is subtracted from the results of the third step S1+S2, and the corrected S1+S2 results of the formation rock are obtained.

[0053] Example 1

[0054] To verify the accuracy of the method of the present application, two control groups A and B were set up. The same depth of oil-free base drilling fluid contaminated cuttings were selected for groups A and B, and the S1+S2 analysis results were obtained for group A after analysis. The MOM oil-based drilling fluid was simulated for the cuttings of group B. The internal standard methyl palmitate with a mass fraction of 0.9% was added to the base oil of the drilling fluid, about 100 mg was reserved for quantitative separation of the group component, the chromatographic content of the internal standard was measured, the cuttings were mixed with the oil-based drilling fluid, and the temperature was simulated at 120°C in the XGRL-3 type roller heating furnace during drilling for more than 16 hours.

[0055] The oil B group base drilling fluid contaminated cuttings were taken and cleaned using the above method and dried.

[0056] 5g of the cleaned and dried cuttings sample was weighed and subjected to rock pyrolysis analysis to obtain the S1+S2 parameter value;

[0057] 20g of the cleaned and dried cuttings sample was quantitatively weighed, and the rock extractives content was determined according to the standard SY / T 5118-2021 "Determination of Extractives Content in Rock", and the proportion of rock extractives in rock was quantitatively calculated;

[0058] According to the SY / T 5119-2016 “Rock Soluble Organic Matter and Crude Oil Group Component Analysis” standard, the rock extract sample obtained in the previous step is quantitatively weighed, and group component analysis is carried out to quantitatively determine the contents of saturated hydrocarbon, aromatic hydrocarbon, non-hydrocarbon and asphaltene four components; the base oil sample containing a fixed proportion of internal standard is used to carry out group component analysis;

[0059] According to the GB / T 18340.5-2010 “Geological Sample Organic Geochemical Analysis Method Part 5: Saturated Hydrocarbon Analysis in Rock Extract and Crude Oil” standard, the saturated hydrocarbon component gas chromatography analysis is carried out, and the normalized percentage content of the internal standard in the saturated hydrocarbon component is calculated; the 100mg sample reserved is used for group component quantitative separation, and the proportion of the internal standard methyl palmitate in the saturated hydrocarbon is measured;

[0060] According to the content of the internal standard in the saturated hydrocarbon and its proportion in the base oil, the content W of the base oil in unit mass of rock is calculated 基础油 (mg / g), see Table 1;

[0061] Table 1 Content W of Base Oil in Rock 基础油 Result data table

[0062]

[0063] Subtract the content of the base oil in unit rock from the S1+S2 result, that is, obtain the corrected S1+S2 result of the formation rock, see Table 2.

[0064] Table 2 A, B Control Group S1+S2 Result Comparison Table

[0065]

[0066]

[0067] From the comparison results of A, B control group S1+S2, the method for determining the content of oil-based drilling fluid organic pollutants in cuttings provided by the present application has the following characteristics:

[0068] (1) Simple operation: the internal standard can be used as a component in the drilling fluid, which does not affect the performance of the drilling fluid, and the added proportion is relatively easy to measure;

[0069] (2) Accurate quantification: the entire quantitative process of the present application belongs to conventional geochemical experiments, and each step of quantification can be traced, and the principle is more clear and accurate than the traditional solvent washing method;

[0070] (3) Wide application range: the addition of internal standard in base oil can not only quantitatively determine the amount of base oil pollution in cuttings, but also quantitatively determine the amount of base oil pollution in oil samples.

[0071] The embodiments of the present application are preferred embodiments of the present application, and are not intended to limit the protection scope of the present application, and thus: any equivalent changes made according to the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A method for determining the content of oil-based drilling fluid organic contaminants in drill cuttings by internal standard method, characterized in that: It comprises the following steps: S1. Add a fixed proportion of an internal standard to the oil-based drilling fluid base oil, mix well, and the base oil is used to prepare the drilling fluid; S2. Take the oil-based drilling fluid contaminated cuttings, if the cuttings surface has sticky oil-based mud pollutants, use the cleaning liquid to remove the oil-based drilling fluid pollutants on the surface of the cuttings; if the cuttings surface has no sticky oil-based mud pollutants, no cleaning is required; dry the cleaned or uncleaned cuttings at low temperature; S3. Take the dried cuttings sample, perform rock pyrolysis analysis according to the GB / T 18602-2012 “Rock Pyrolysis Analysis” standard, and obtain the S1+S2 parameter value; S4. According to the SY / T 5118-2021 “Determination of Extractives in Rocks” standard, quantitatively weigh the dried cuttings sample in step S2, determine the content of rock extractives, and quantitatively calculate the proportion of rock extractives in rock; S5. According to the SY / T 5119-2016 “Analysis of Soluble Organic Matter and Crude Oil Group Components in Rocks” standard, quantitatively weigh the rock extractive sample obtained in step S4, quantitatively determine the contents of saturated hydrocarbons, aromatic hydrocarbons, non-hydrocarbons and asphaltene; use the base oil sample containing a fixed proportion of internal standard to carry out group component analysis; S6. According to the GB / T 18340.5-2010 “Geological Sample Organic Geochemical Analysis Method Part 5: Analysis of Saturated Hydrocarbons in Rock Extractives and Crude Oil” standard, carry out saturated hydrocarbon component gas chromatography analysis, calculate the normalized percentage content of the internal standard in the saturated hydrocarbon component; and determine the proportion of the internal standard in the saturated hydrocarbon according to the GB / T 18340.5-2010 standard method; S7. Calculate the content of base oil in unit mass of rock W according to the content of internal standard in saturated hydrocarbon and its proportion in base oil 基础油 , in mg / g, see formula (1): (1) In the formula, W 基础油 : Amount of base oil contamination per unit mass of rock R0: Proportion of internal standard in base oil, %; R1: Proportion of rock extractives in rock, %; R2: Proportion of saturated hydrocarbons in rock extractives, %; R3: Normalized percentage content of internal standard in saturated hydrocarbon component, %; R4: Proportion of internal standard in saturated hydrocarbon, %; S8. Subtract the content of base oil in unit rock from the S1+S2 result in step S3 to obtain the corrected S1+S2 result in the formation rock; The internal standard is methyl palmitate; The cleaning liquid comprises potassium chloride, sodium di(2-ethyl ethyl) sulfonate and water, and the mass ratio of the three is (15-25):(5-15):(300-400).

2. The method for determining the content of oil-based drilling fluid organic pollutants in cuttings by internal standard method according to claim 1, characterized in that: In step S1, the amount of internal standard added is 0.5%-1%.

3. The method for determining the content of oil-based drilling fluid organic pollutants in cuttings by internal standard method according to claim 1, characterized in that: In step S2, the cleaning method is: add the prepared cleaning liquid to the oil-based contaminated cuttings, stir at 1500-2500 rpm for 10-15 min, rinse the cuttings with water until there is no foam, and dry.

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