Organic acid salt methanol extraction method

Abstract

The invention discloses an organic acid salt methanol extraction method. The method comprises the following steps: forming a simulated standard sample to simulate carbonate rock components by matching a matrix and an organic acid salt standard sample; performing a first extraction step of the first substance on the simulated standard sample by using a dichloromethane solvent to obtain a second substance; performing a second extraction step on the acid-soluble organic matter in the second substance by using a methanol solvent; weighing an empty beaker to obtain a first mass, and completely transferring the residual methanol solvent after the second extraction step into the empty beaker; after the methanol solvent in the beaker is completely volatilized, weighing the beaker to obtain a second mass; the recovery rate of the acid-soluble organic matter in the second substance is calculated according to the difference value of the first mass and the second mass; according to the calculation result of the recovery rate, the loss of the acid-soluble organic matters in the carbonate rock can be reduced by using the methanol solvent for extraction, and the problem that the abundance of the organic matters in the carbonate rock sample cannot be truly reflected by a traditional TOC determination method is solved.

Description

Technical Field

[0001] This application relates to the technical field of chemical engineering, and particularly relates to a method for extracting organic acid salts with methanol. Background Art

[0002] Since the most commonly used method for evaluating the organic matter content of source rocks is TOC (total organic carbon content in rocks), which is usually expressed as a percentage. Generally speaking, the higher the organic matter content of the source rock, the greater its hydrocarbon generation potential. Therefore, the TOC method can be used as one of the important indicators for evaluating the hydrocarbon generation potential of source rocks.

[0003] Previous studies have found that a large amount of organic matter is contained in the acidolysis solution lost during the acidolysis pretreatment of TOC, that is, the organic matter dissolved in the aqueous phase of the acidolysis solution, which is called acid-soluble organic matter. Acidolysis refers to the process in which carbonate minerals in the sample react with an acid to remove inorganic carbon and dissolve the organic matter in the aqueous phase. This process can release the organic matter from the sample and exist in the acid solution in the form of organic carbon.

[0004] Therefore, the loss of acid-soluble organic matter results in part of the organic matter not being included in the measurement range of organic carbon, which is one of the important reasons for the low TOC test results. The traditional TOC determination method simply cannot truly reflect the organic matter abundance of carbonate rock samples. Summary of the Invention

[0005] In the embodiments of this application, by providing a method for extracting organic acid salts with methanol, the problem that the loss of acid-soluble organic matter results in part of the organic matter not being included in the measurement range of organic carbon, which is one of the important reasons for the low TOC test results, and the traditional TOC determination method simply cannot truly reflect the organic matter abundance of carbonate rock samples is solved.

[0006] First aspect, an embodiment of the present application provides a method for methanol extraction of organic acid salts, the method comprising: forming a simulated standard sample to simulate the composition of carbonate rocks with a matrix and an organic acid salt standard sample; performing a first extraction step of a first substance on the simulated standard sample using a dichloromethane solvent to obtain a second substance; wherein the first substance is soluble organic matter and the second substance is the remaining substance after the first extraction step of the simulated standard sample; performing a second extraction step on the acid-soluble organic matter in the second substance using a methanol solvent; wherein the acid-soluble organic matter in the second substance is the organic acid salt standard sample; wherein the second extraction step includes: determining the optimal extraction temperature of the methanol solvent according to the dropping rate inspection method; setting parameters during the extraction process for the methanol solvent and performing extraction using the determined optimal extraction temperature of the methanol solvent; processing the second substance in a rapid Soxhlet extractor and extracting the acid-soluble organic matter in the second substance, thereby completing the second extraction step; weighing an empty beaker to obtain a first mass, and transferring all the remaining methanol solvent after the second extraction step to the empty beaker; after the methanol solvent in the beaker has evaporated completely, weighing the beaker to obtain a second mass; calculating the recovery rate of the acid-soluble organic matter in the second substance according to the difference between the first mass and the second mass to obtain a recovery rate calculation result; characterizing that using the methanol solvent for extraction can reduce the loss of acid-soluble organic matter in carbonate rocks according to the recovery rate calculation result.

[0007] In combination with the first aspect, in a possible implementation manner, before calculating the recovery rate of the acid-soluble organic matter in the second substance according to the difference between the first mass and the second mass to obtain a recovery rate calculation result, it further includes: extracting the matrix in the simulated standard sample using a methanol solvent under set extraction conditions and obtaining the average mass of the extracted matrix; wherein the obtained average mass of the extracted matrix is 0.02 g.

[0008] In combination with the first aspect, in a possible implementation manner, the set extraction conditions are an extraction temperature of 180 °C and an extraction time of 8 h.

[0009] In combination with the first aspect, in a possible implementation manner, calculating the recovery rate of the acid-soluble organic matter in the second substance according to the difference between the first mass and the second mass to obtain a recovery rate calculation result includes: according to the formula calculating the recovery rate of the acid-soluble organic matter in the second substance, thereby obtaining a recovery rate calculation result; wherein m1 is the first mass obtained by weighing the empty beaker, m2 is the second mass obtained by weighing the beaker, 0.02 is the average mass of the extracted matrix obtained by extracting the matrix in the simulated standard sample using a methanol solvent, and m oas is the mass of the added organic acid salt standard sample.

[0010] In combination with the first aspect, in a possible implementation manner, the first extraction step of the first substance from the simulated standard sample using dichloromethane solvent includes: judging the optimal extraction temperature of dichloromethane solvent according to the drip rate inspection method; wherein, the judged optimal extraction temperature of dichloromethane solvent is 120 °C; setting the parameters during the extraction process for dichloromethane solvent, and performing extraction using the judged optimal extraction temperature of dichloromethane solvent; wherein, the parameters during the extraction process of dichloromethane solvent are designed as: the volume of dichloromethane solvent is 150 ml, the hot extraction time is 5 h, the elution time is 5 h, and the dichloromethane solvent recovery time is 12 - 15 min; performing the treatment of the first substance in a rapid Soxhlet extractor, and extracting the first substance, thereby completing the first extraction step.

[0011] In combination with the first aspect, in a possible implementation manner, the optimal extraction temperature of methanol solvent judged according to the drip rate inspection method is 180 °C; setting the parameters during the extraction process for methanol solvent, and performing extraction using the judged optimal extraction temperature of methanol solvent; wherein, the parameters during the extraction process of methanol solvent are designed as: the volume of methanol solvent is 150 ml, the hot extraction time is 4 h, the elution time is 4 h, and the methanol solvent recovery time is 12 - 15 min.

[0012] In combination with the first aspect, in a possible implementation manner, the matrix is calcite and dolomite, and the organic acid salt standard samples are calcium acetate, magnesium acetate, calcium propionate, calcium benzoate, calcium stearate and magnesium stearate.

[0013] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects:

[0014] The embodiments of the present application provide a method for extracting organic acid salts with methanol. The present application simulates the composition of carbonate rocks to form a simulated standard sample. Since dichloromethane can extract soluble organic matter, first, dichloromethane is used to perform the first extraction step on the simulated standard sample to exclude the interference of soluble organic matter, and then methanol is selected as the solvent to perform the second extraction step to extract acid-soluble organic matter. According to the experimental results, it is concluded that the method used in the present application can reduce the loss of acid-soluble organic matter in carbonate rocks. It solves the problem that the loss of acid-soluble organic matter causes some organic matter not to be included in the measurement range of organic carbon, which is one of the important reasons for the low TOC test results, and the traditional TOC determination method simply cannot truly reflect the organic matter abundance of carbonate rock samples. Description of the Drawings

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments of the present invention or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0016] Figure 1 It is a flowchart of the organic acid salt methanol extraction method provided by the embodiment of the present application;

[0017] Figure 2 It is a specific flowchart of the first extraction step of the first substance from the simulated standard sample using dichloromethane solvent provided by the embodiment of the present application;

[0018] Figure 3 It is a graph showing the relationship between the recovery rate of dichloromethane for the matrix and the extraction time provided by the embodiment of the present application;

[0019] Figure 4 It is a schematic diagram of the recovery rate of extracting organic acid salt standard sample with methanol solvent provided by the embodiment of the present application;

[0020] Figure 5 It is an infrared spectrogram of the methanol solvent extract provided by the embodiment of the present application. Detailed implementation manners

[0021] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0022] The following explains some of the technologies related to the embodiments of the present application to facilitate understanding. It should be considered that they are only exemplary. Therefore, those of ordinary skill in the art should recognize that various changes and modifications can be made to the embodiments described here without departing from the scope and spirit of the present application. Similarly, for the sake of clarity and conciseness, some descriptions of well-known functions and structures are omitted in the following description.

[0023] The embodiment of the present application provides an organic acid salt methanol extraction method. As Figure 1 shown, this method includes steps S101 to S110. Among them, Figure 1 This is only one execution order shown in the embodiment of the present application and does not represent the only execution order of an organic acid salt methanol extraction method. Under the condition that the final result can be achieved, Figure 1 the steps shown can be executed in parallel or reversed.

[0024] Since the most commonly used method for evaluating the organic matter content of source rocks is TOC (Total Organic Carbon content in rocks), which is usually expressed as a percentage. Generally speaking, the higher the organic matter content of the source rock, the greater its hydrocarbon generation potential. Therefore, the TOC method can be used as one of the important indicators for evaluating the hydrocarbon generation potential of source rocks. In addition to TOC, there are also some other methods for evaluating source rocks, such as Rock Pyrolysis Analysis, Infrared Spectroscopy, Gas Chromatography-Mass Spectrometry, etc. These methods can provide more detailed information, such as the type, maturity and abundance of organic matter, so as to more comprehensively evaluate the hydrocarbon generation potential of source rocks.

[0025] Previous studies have found that a large amount of organic matter is contained in the acidolysis solution lost during the acidolysis pretreatment of TOC, that is, the organic matter dissolved in the aqueous phase of the acidolysis solution, which is called acid-soluble organic matter. Acidolysis refers to the process in which carbonate minerals in the sample react with acid to remove inorganic carbon and dissolve the organic matter in the aqueous phase. This process can release the organic matter from the sample and exist in the acid solution in the form of organic carbon. Therefore, the loss of acid-soluble organic matter results in part of the organic matter not being included in the measurement range of organic carbon, which is one of the important reasons for the low TOC test results. The traditional TOC determination method simply cannot truly reflect the organic matter abundance of carbonate rock samples.

[0026] The main component of acid-soluble organic matter is organic acid salts, and it has been confirmed by previous studies that organic acid salts, as a type of potential hydrocarbon generation parent material different from kerogen. In addition to organic acid salts, there are a large number of fatty acid salts and a small amount of compounds such as hydrocarbons, alcohols, aldehydes, and ketones in acid-soluble organic matter. Most acids are combined or co-precipitated with calcium carbonate minerals in the form of acids or salts, and some are trapped inside the minerals and released only after the minerals dissolve. These organic matters have a wide variety and significant differences in chemical properties, and it is difficult to use a single method to extract all the acid-soluble organic matter in geological samples for quantitative and qualitative analysis.

[0027] Table 1

[0028] solvent calcium stearate magnesium stearate sodium stearate stearic acid water insoluble insoluble soluble insoluble dichloromethane insoluble insoluble insoluble soluble benzene soluble soluble insoluble soluble methanol slightly soluble slightly soluble soluble slightly soluble

[0029] Table 1 shows the solubility of carboxylates and carboxylic acids in a series of solvents. Among them, calcium stearate, magnesium stearate, and sodium stearate are all carboxylates, and stearic acid is a carboxylic acid. It can be known from Table 1 that methanol has good solubility for carboxylates and carboxylic acids. The relative content of salts changes with the change of the polarity of the extraction solvent, and methanol is a solvent with relatively strong polarity and is often used as an extractant for organic substances. Previous studies have found that by comparing the salt contents extracted by different solvents, when the relative content of methanol in the benzene extraction system increases, the percentage of salts obtained will increase, and methanol is used as a solvent to extract a series of carboxylates from Green River oil shale, including monocarboxylates, dicarboxylates, alicyclic and unsaturated acid salts, branched-chain fatty acid salts, and aromatic acid salts, etc. The maximum concentration accounts for 3.62% of the total organic matter. These salts are the combination or coprecipitation of organic acids and carbonate minerals.

[0030] Therefore, in this application, the composition of carbonate rocks is simulated to form a simulated standard sample. Since dichloromethane can extract soluble organic matter, first, a first extraction step is performed on the simulated standard sample with dichloromethane to exclude the interference of soluble organic matter, and then methanol is selected as the solvent for the second extraction step to extract acid-soluble organic matter. According to the experimental results, it is concluded that the method used in this application can reduce the loss of acid-soluble organic matter in carbonate rocks.

[0031] S101: Form a simulated standard sample by mixing a matrix and an organic acid salt standard sample to simulate the composition of carbonate rocks.

[0032] Specifically, the matrix is calcite and dolomite, and the organic acid salt standard samples are calcium acetate, magnesium acetate, calcium propionate, calcium benzoate, calcium stearate, and magnesium stearate. The theoretical TOC of these simulated standard samples is 3% for all.

[0033] S102: Perform a first extraction step of the first substance on the simulated standard sample with a dichloromethane solvent to obtain a second substance. Among them, the first substance is soluble organic matter, and the second substance is the remaining substance after the first extraction step of the simulated standard sample.

[0034] Figure 2 The following is a specific flowchart of the first extraction step of the first substance on the simulated standard sample with a dichloromethane solvent provided by the embodiment of this application, as Figure 2 shown, including steps S201 to S203.

[0035] S201: Determine the optimal extraction temperature of the dichloromethane solvent according to the drip rate inspection method. Among them, the determined optimal extraction temperature of the dichloromethane solvent is 120 °C.

[0036] Specifically, the optimal extraction temperature of the fully automatic Soxhlet extractor is determined based on the boiling point of the solvent through the drip rate inspection method. When the set temperature is reached, observe the drip rate of the solvent dripping from the sample rod to the leaching cup during the elution process. The set temperature is appropriate when the solvent drip rate is about 2 to 3 drops per second. If the temperature is too low, the drip rate requirement for elution cannot be met, and the extraction efficiency is low; if the temperature is too high, the solvent will not have time to condense, and the risk of escape will increase. Through the drip rate inspection experiment, it was determined that the optimal extraction temperature of dichloromethane solvent is 120°C, and the optimal extraction temperature of methanol is 180°C.

[0037] S202: Setting parameters for the dichloromethane solvent during the extraction process, and using the determined optimal extraction temperature of the dichloromethane solvent for extraction. The parameters for the dichloromethane solvent extraction process are designed as follows: dichloromethane solvent volume 150 ml, hot leaching time 5 hours, elution time 5 hours, dichloromethane solvent recovery time 12-15 minutes.

[0038] S203: treating the first substance in a rapid Soxhlet extractor and extracting the first substance, thereby completing the first extraction step.

[0039] Specifically, the conventional Soxhlet extractor is one of the earliest extraction instruments used and is also a commonly used instrument in petroleum geology laboratories. The cycle process of Soxhlet extraction is mainly divided into four stages: solvent heating and vaporization, steam rising to the serpentine tube and then condensing, condensed solvent dripping into the extraction tube and solvent in the extraction tube siphoning back to the extraction bottle. Through continuous circulation, the sample is always immersed in pure solvent, thereby achieving efficient extraction. However, the actual operation of this method is relatively complicated, the amount of solvent used is large, and the extraction efficiency is relatively low. Therefore, the present application adopts a rapid Soxhlet extractor to perform the first extraction step and the second extraction step.

[0040] Specifically, the rapid Soxhlet extraction apparatus is a fully automatic and efficient extraction system with an extraction efficiency more than 5 times that of traditional Soxhlet extraction. Each extraction process includes four steps:

[0041] (1) Boiling: The sample is immersed in a boiling solvent to extract most of the soluble substances.

[0042] (2) Elution: The sample is lifted above the solvent level and condensed and refluxed into the filter cartridge to effectively dissolve the remaining soluble matter.

[0043] (3) Recovery: Automatically collect the distilled solvent into a recovery bottle for reuse.

[0044] (4) The program is automatically terminated, the extraction cup leaves the heating plate, and after cooling, it is removed for the next step of analysis.

[0045] Specifically, the entire analysis process requires no manual operation. One only needs to load the sample and start the program to complete it automatically. The rapid Soxhlet extractor uses a closed recovery system, avoiding manual handling of chemical reagents, reducing solvent volatilization, and ensuring that each sample is analyzed with an equal amount of reagent.

[0046] Furthermore, the sample used to complete the first extraction step with the rapid Soxhlet extractor refers to the simulated standard sample, and the solvent refers to dichloromethane solvent. The sample used to complete the second extraction step with the rapid Soxhlet extractor refers to the remaining substance after the first extraction step of the simulated standard sample, and the solvent refers to methanol solvent.

[0047] S103: Perform a second extraction step on the acid-soluble organic matter in the second substance using methanol solvent. Among them, the acid-soluble organic matter in the second substance is the organic acid salt standard sample.

[0048] S104: Determine the optimal extraction temperature of methanol solvent according to the drip rate inspection method. The optimal extraction temperature of methanol solvent determined according to the drip rate inspection method is 180 °C.

[0049] S105: Set the parameters during the extraction process for methanol solvent and perform extraction using the determined optimal extraction temperature of methanol solvent. Among them, the parameters during the extraction process of methanol solvent are designed as follows: the volume of methanol solvent is 150 ml, the hot extraction time is 4 h, the rinsing time is 4 h, and the methanol solvent recovery time is 12 - 15 min.

[0050] S106: Perform the treatment of the second substance in the rapid Soxhlet extractor and extract the acid-soluble organic matter in the second substance, thereby completing the second extraction step.

[0051] The experimental procedure of the specific second extraction step is as follows:

[0052] (1) Turn on the rapid Soxhlet extractor and perform self-check, set the instrument parameters, turn on the circulating cooling water, and check the ultra-high temperature protection setting.

[0053] (2) Weigh a certain mass of the sample and add it to the filter paper cylinder. Put in absorbent cotton to increase the contact area between the solvent and the sample and improve the extraction efficiency. Install the adapter to the filter paper cylinder and then put it into the extraction unit. Specifically, the sample here refers to the remaining substance after the first extraction step of the simulated standard sample.

[0054] (3) Measure 150 ml of the solvent and add it to the extraction cup. Put the extraction cup into the extraction cup holder. After the extraction cup holder is put into the extraction unit, press it down so that the condenser and the extraction cup are closely attached together and pressed onto the heating plate.

[0055] (3) Click the start button to start the program, thereby completing the second extraction step.

[0056] S107: Weigh an empty beaker to obtain a first mass, and transfer all the remaining methanol solvent after the second extraction step to the empty beaker.

[0057] Specifically, the capacity of the empty beaker can be 50 ml. Transfer the remaining methanol solvent after the second extraction step to the empty beaker, then rinse the extraction cup with methanol until clean, and combine the rinsing liquid into the beaker.

[0058] After all the methanol solvent is transferred to the empty beaker, the filter paper cylinder needs to be taken out and discarded. The extraction cup is washed, dried and reserved. The recovery reagent bottle is emptied, and after closing the circulating cooling water, the rapid Soxhlet extractor is turned off.

[0059] S108: After the methanol solvent in the beaker has evaporated completely, weigh the beaker to obtain a second mass.

[0060] Specifically, when the solvent in the extraction cup is less than 10 ml, the second extraction step is completed. After cooling, transfer the solvent in the extraction cup to a 50 mL empty beaker. After the reagent has evaporated at room temperature, weigh the beaker to obtain a second mass for quantification.

[0061] S109: Calculate the recovery rate of the acid-soluble organic matter in the second substance according to the difference between the first mass and the second mass, and obtain the calculation result of the recovery rate.

[0062] This application uses methanol solvent to extract calcium acetate (C4H6O4Ca), magnesium acetate (C4H6O4Mg), calcium propionate (C6H 10 O4Ca), calcium benzoate (C 14 H 10 O4Ca), calcium stearate (C 36 H 70 O4Ca) and magnesium stearate (C 36 H 70 O4Mg). Among them, calcium acetate, magnesium acetate, calcium propionate and calcium benzoate are small molecule organic acid salts, calcium stearate is a long-chain organic acid salt, and magnesium stearate is a magnesium salt.

[0063] Therefore, before calculating the recovery rate of the acid-soluble organic matter in the second substance according to the difference between the first mass and the second mass and obtaining the calculation result of the recovery rate, it also includes: using methanol solvent to extract the matrix in the simulated standard sample under the set extraction conditions, and obtaining the average mass of the extracted matrix. Among them, the average mass of the extracted matrix obtained is 0.02 g. The set extraction conditions are an extraction temperature of 180 °C and an extraction time of 8 h.

[0064] Specifically, the purpose of the above steps is to deduct the extractable mass of the matrix before obtaining the recovery rate calculation result, extract the organic acid salt standard sample, and compare it with the corrected result. Table 2 shows the results of the mass of the matrix extracted by methanol. From Table 2, it can be obtained that the average mass of the extracted matrix is approximately 0.02 g.

[0065] Table 2

[0066]

[0067] According to the formula Calculate the recovery rate of the acid-soluble organic matter in the second substance to obtain the recovery rate calculation result. Among them, m1 is the first mass obtained by weighing the empty beaker, m2 is the second mass obtained by weighing the beaker, 0.02 is the average mass of the extracted matrix obtained by extracting the matrix in the simulated standard sample with methanol solvent, and m oas is the mass of the added organic acid salt standard sample.

[0068] Table 3

[0069]

[0070] Table 3 shows the results of the recovery rate of the matrix extracted by dichloromethane. Figure 3 This is the relationship diagram between the recovery rate of dichloromethane for the matrix and the extraction time provided by the embodiment of the present application. From Table 3 and Figure 3 it can be obtained that when the extraction time is set to 8 h, the recovery rate of dichloromethane for the matrix is relatively low. As the extraction time extends, the recovery rate increases significantly. When the extraction time is set to 10 h, the recovery rate increases to about 28%. At this time, even if the extraction time is increased to 12 h, the recovery rate is stable at about 28% and tends to be stable. Continuing to extend the extraction time, the recovery rate has no significant change. Therefore, it is proved that the dichloromethane extraction time of 10 h is more appropriate, and both the boiling time and the elution time are 5 h.

[0071] This application selects the Permian Lucaogou Formation shale in the Junggar Basin, the Eagle Ford and Green River shales in the United States to extract geological samples to explore the rationality of the experiments of this application.

[0072] Table 4

[0073]

[0074]

[0075] Table 4 shows the results of extracting geological samples with dichloromethane solvent. From Table 4, it can be obtained that the mass of the soluble organic matter, i.e., chloroform bitumen "A", extracted from the geological samples with dichloromethane tends to be stable after 10 h, which verifies the rationality of the above steps. Therefore, in order to maximize the extraction efficiency, the extraction time of dichloromethane is set to 10 h.

[0076] Table 5

[0077]

[0078] Table 5 shows the results of extracting organic acid salt standards with methanol solvent. Figure 4 This is the schematic diagram of the recovery rate of extracting organic acid salt standards with methanol solvent provided in the embodiment of the present application. From Figure 4 and Table 5, it can be obtained that methanol has a good dissolution ability for organic acid salts, the extraction efficiency for small-molecule organic acid salts can reach more than 80%, the extraction efficiency for long-chain calcium salts is relatively low, and the extraction efficiency for easily soluble magnesium salts is also relatively high. Among them, calcium acetate, magnesium acetate, calcium propionate, and calcium benzoate are small-molecule organic acid salts, calcium stearate is a long-chain organic acid salt, and magnesium stearate is a magnesium salt.

[0079] S110: Characterize that using methanol solvent for extraction can reduce the loss of acid-soluble organic matter in carbonate rocks according to the calculation results of the recovery rate.

[0080] Figure 5 This is the infrared spectrogram of the methanol solvent extract provided in the embodiment of the present application. In order to verify the solubility of methanol in organic acid salts in geological samples, the American Eagle Ford shale and the Permian Maokou limestone in the Sichuan Basin were selected for extraction, and the composition of the extract was determined by infrared spectroscopy. The results show that there is a large amount of organic matter in the extract. As Figure 5 shown, the upper figure is the infrared spectrogram of the methanol solvent extract of the American Eagle Ford shale, and the lower figure is the infrared spectrogram of the methanol solvent extract of the Permian Maokou limestone in the Sichuan Basin. As Figure 5 shown, the two peaks near 2850 cm -1 in the upper figure and 2920 cm -1 in the lower figure are C-H, that is, the stretching vibration of methylene, and the absorption of unsaturated C-H stretching vibration is higher than 3000 cm -1 , which may be alkenes, alkynes or aromatic compounds, while the stretching vibration of saturated C-H is generally lower than 3000 cm -1 , indicating that there are some saturated hydrocarbons in the extract. The hydroxyl peak at 3500 - 3100 cm -1 may still be caused by the water absorption of KBr, and the hydroxyl group is easy to associate with alcohols and phenols, showing a strong peak near 3300 cm -1 . The peaks at 1725 - 1750 cm -1and 1050 - 1300 cm -1 The weak absorption peaks that appear may also indicate the presence of esters, with two absorption bands for C=O and C-O. 1500 - 1690 cm -1 The strong peak that appears may be the stretching vibration of the C=C skeleton. The carboxylate carboxyl group COO- is a system with a multi-electron π bond. The two C=O vibrations are strongly coupled, so separated asymmetric and symmetric stretching frequencies appear, and their intensity is very high. The asymmetric stretching frequency is at 1610 - 1560 cm -1 , which is the characteristic absorption of carboxylates. At 1440 - 1360 cm -1 The symmetric stretching frequency appears, with a slightly weaker intensity, generally as a broad absorption of two or three peaks. It is confirmed that methanol can dissolve more organic matter and some organic acid salts.

[0081] Existing studies have not been able to clearly determine the approximate ratio and content of carboxylates and carboxylic acids. Approximately 20% of the kerogen structure contains carboxyl groups, and these groups are mainly carboxylic acids and carboxylates. The carboxylates extracted by methanol account for 3.6% of the total organic matter. Taking a sample with a total organic carbon content of 0.5% as an example, if it is assumed that all of this part of the carboxylates generate hydrocarbons, the content of organic matter lost in the TOC pretreatment process is at least about 0.02%. Methanol, as a single solvent, can only dissolve part of the acid-soluble organic matter, namely organic acid salts. The pyrolysis of organic acid salts / carboxylates can form hydrocarbon compounds, and its potential cannot be ignored.

Claims

1. A method for extracting an organic acid salt with methanol, characterized in that, Comprising: Forming a simulated standard sample by mixing a matrix and an organic acid salt standard sample to simulate the composition of carbonate rocks; Performing a first extraction step of a first substance on the simulated standard sample using a dichloromethane solvent to obtain a second substance; wherein, the first substance is soluble organic matter, and the second substance is the remaining substance after the first extraction step of the simulated standard sample; Performing a second extraction step on the acid-soluble organic matter in the second substance using a methanol solvent; wherein, the acid-soluble organic matter in the second substance is an organic acid salt standard sample; Wherein, the second extraction step includes: Judging the optimal extraction temperature of the methanol solvent according to the drop rate inspection method; Setting parameters during the extraction process for the methanol solvent and performing extraction using the judged optimal extraction temperature of the methanol solvent; Performing the treatment of the second substance in a rapid Soxhlet extractor and extracting the acid-soluble organic matter in the second substance to complete the second extraction step; Weighing an empty beaker to obtain a first mass, and transferring all the remaining methanol solvent after the second extraction step to the empty beaker; After the methanol solvent in the beaker has evaporated completely, weighing the beaker to obtain a second mass; Calculating the recovery rate of the acid-soluble organic matter in the second substance according to the difference between the first mass and the second mass to obtain a recovery rate calculation result; Characterizing that using a methanol solvent for extraction can reduce the loss of acid-soluble organic matter in carbonate rocks according to the recovery rate calculation result.

2. The method according to claim 1, wherein Before calculating the recovery rate of the acid-soluble organic matter in the second substance according to the difference between the first mass and the second mass to obtain a recovery rate calculation result, it further includes: Extracting the matrix in the simulated standard sample using a methanol solvent under set extraction conditions and obtaining the average mass of the extracted matrix; wherein, the obtained average mass of the extracted matrix is 0.02 g.

3. The method according to claim 2, characterized in that, The set extraction conditions are an extraction temperature of 180 °C and an extraction time of 8 h.

4. The method according to claim 2, wherein Calculating the recovery rate of the acid-soluble organic matter in the second substance according to the difference between the first mass and the second mass to obtain a recovery rate calculation result, including: According to the formula calculate the recovery rate of the acid-soluble organic matter in the second substance to obtain the calculation result of the recovery rate; where m1 is the first mass obtained by weighing an empty beaker, m2 is the second mass obtained by weighing the beaker, 0.02 is the average mass of the extracted matrix obtained by extracting the matrix in the simulated standard sample with a methanol solvent, and m oas is the mass of the organic acid salt standard sample added.

5. The method according to claim 1, wherein The first extraction step of the first substance on the simulated standard sample using a dichloromethane solvent includes: Judging the optimal extraction temperature of the dichloromethane solvent according to the drop rate inspection method; wherein, the judged optimal extraction temperature of the dichloromethane solvent is 120 °C; Setting parameters during the extraction process for the dichloromethane solvent and performing extraction using the judged optimal extraction temperature of the dichloromethane solvent; wherein, the parameters designed during the extraction process of the dichloromethane solvent are: the volume of the dichloromethane solvent is 150 ml, the hot extraction time is 5 h, the rinsing time is 5 h, and the dichloromethane solvent recovery time is 12 - 15 min; Performing the treatment of the first substance in a rapid Soxhlet extractor and extracting the first substance to complete the first extraction step.

6. The method according to claim 1, characterized in that, The optimal extraction temperature of the methanol solvent judged according to the drop rate inspection method is 180 °C; Set the parameters during the extraction process for the methanol solvent, and perform extraction using the determined optimal extraction temperature of the methanol solvent; among them, the parameters in the extraction process of the methanol solvent are designed as follows: the volume of the methanol solvent is 150 ml, the hot extraction time is 4 h, the elution time is 4 h, and the methanol solvent recovery time is 12 - 15 min.

7. The method according to claim 1, characterized in that The matrix is calcite and dolomite, and the organic acid salt standard samples are calcium acetate, magnesium acetate, calcium propionate, calcium benzoate, calcium stearate, and magnesium stearate.

Images