A method for extracting biomarker compounds from rocks

Abstract

The invention discloses a method for extracting biomarker compounds from rocks, comprising chromatographic separation of rock samples, cooling and concentrating the products of the chromatographic separation in the process of flowing into a receiving container; the method solves the problems that the biomarker compounds extracted by the existing method cannot be used for oil source comparison or judgment of the maturity of organic matter in high-overmature areas, and the problems of large reagent consumption, high toxicity of the reagents used, complicated operation and slow analysis speed.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas exploration and development, and in particular to a method for extracting biomarker compounds from rocks. Background Art

[0002] Biomarker compounds are derived from living organisms and have a certain degree of stability during the evolution of organic matter. They have not changed or have changed very little, and basically preserve the carbon skeleton and special structural information of the original biological matrix. Therefore, they have a special "marking effect" and are the most commonly used methods in the field of oil and gas exploration and development for oil-rock comparison, oil-oil comparison, maturity evaluation, etc.

[0003] At present, the domestic oil and gas industry implements the following industry standards for extracting biomarker compounds from rocks: SY / T 5118-2021 "Determination of Extract Content in Rocks" and SY / T 5119-2016 "Analysis of Soluble Organic Matter in Rocks and Crude Oil Group Components". Among them, SY / T 5118-2021 "Determination of Extract Content in Rocks" is used to separate soluble organic matter from rocks, and SY / T5119-2016 "Analysis of Soluble Organic Matter in Rocks and Crude Oil Group Components" is used to separate the group composition of soluble organic matter.

[0004] SY / T 5118-2021 "Determination of Extract Content in Rocks" requires that the sample be dried in an oven at 40℃~45℃ for more than 4 hours before being crushed; the dichloromethane extract solution is heated and concentrated at a temperature not higher than 50℃, and finally evaporated to dryness at room temperature. SY / T 5119-2016 "Analysis of Soluble Organic Matter in Rocks and Crude Oil Group Components" uses n-hexane to precipitate and filter the asphaltene solution in the soluble organic matter in the rock. After the n-hexane filtrate is concentrated, it is eluted with organic solvents of different polarities to obtain saturated hydrocarbons, aromatic hydrocarbons and colloid solutions in turn; the solvent of each group component solution is evaporated to dryness and constant weight at a temperature not higher than 40℃, and weighed to obtain biomarker compounds. The C 14 The biomarker compounds before the C-terminal have been basically lost, so the methods described in SY / T 5118-2021 "Determination of Extract Content in Rocks" and SY / T 5119-2016 "Analysis of Soluble Organic Matter in Rocks and Crude Oil Group Components" limit the C-terminal 14 In addition, the above methods also have the problems of large reagent consumption, high toxicity of the reagents used, complicated operation and slow analysis speed.

[0005] According to research, light hydrocarbon fractions in soluble organic matter contain a wealth of geochemical information such as origin, thermal maturity, and sedimentary environment. For example, adamantane has good thermal stability. Once formed, it is not easily damaged by thermal degradation and microorganisms. The content and distribution characteristics of adamantane series compounds can be used as indicators for evaluating maturity, biodegradation, and oil-source correlation. In addition, the content and ratio of light hydrocarbon fractions are controlled by source rocks and sedimentary environments, and may become a new parameter for oil-source correlation. Therefore, light hydrocarbon fractions in soluble organic matter have unique advantages in the exploration and development of high-overmature areas. It is of great significance to extract biomarker compounds in light soluble organic matter from rocks and conduct research based on this.

[0006] However, the following problems will occur when applying the current methods in areas with high organic matter maturity: A large number of studies generally believe that the maturity window Ro of Gulong shale oil is 1.1% to 1.6%, which is the most favorable stage for the large-scale conversion of adsorbed oil to free oil in shale oil; and the shale maturity in Sichuan and Chongqing is higher. However, conventional sterane and terpane biomarker compounds in soluble organic matter in high-overmature areas have been severely degraded, and their content is too low. Normal chromatography-mass spectrometry analysis often cannot accurately and qualitatively analyze their composition, nor can it conduct oil source comparison or judge the maturity of organic matter through its composition. Therefore, the currently used biomarker compound extraction and identification methods cannot be applied in exploration in areas with high organic matter maturity. Summary of the invention

[0007] In view of this, the present invention provides a method for extracting biomarker compounds from rocks to solve the problem that the biomarker compounds extracted by the existing methods cannot be used for oil source comparison or judgment of the maturity of organic matter in high-overmature areas.

[0008] To achieve the above-mentioned purpose of the invention, the method for extracting biomarker compounds from rocks comprises:

[0009] Chromatographic separation of rock samples;

[0010] The product separated by chromatography is cooled and concentrated during the process of flowing into the receiving container.

[0011] Furthermore, the cooling and concentrating method comprises:

[0012] Passing nitrogen into the receiving container;

[0013] The nitrogen gas stream is used to carry away the separation reagent in the product to concentrate the product and reduce the temperature of the product.

[0014] Furthermore, the receiving container is subjected to a cooling treatment in advance.

[0015] Furthermore, a minimum amount of the separation reagent is retained in the receiving container to keep the light components in the product in a solution environment.

[0016] Further, the separation reagent is n-hexane and a mixed reagent of dichloromethane and n-hexane;

[0017] The n-hexane is used to elute the saturated hydrocarbon components in the rock sample;

[0018] The dichloromethane and n-hexane mixed reagent is used to elute the aromatic components in the rock sample.

[0019] Furthermore, the chromatographic separation is preceded by chromatographic extraction;

[0020] The chromatographic extraction is to place the rock sample on top of a chromatographic column stationary phase and add a solvent into the chromatographic column to extract the organic matter in the rock sample.

[0021] Furthermore, the solvent is n-hexane, and the sample is soaked in n-hexane for 8 hours before extraction.

[0022] Further, a dispersant is added to the rock sample;

[0023] Furthermore, the dispersant is 80-200 mesh silica gel or diatomaceous earth.

[0024] Furthermore, the amount of the dispersant added is 30%-50% of the weight of the rock sample.

[0025] Furthermore, the rock sample is subjected to freezing or cooling treatment before being loaded into the chromatography column.

[0026] Furthermore, the freezing or cooling treatment method comprises:

[0027] Freezing or cooling the block rock to be extracted so that the block rock is below normal temperature;

[0028] The block rock is crushed in an environment below normal temperature or under the condition that the sample chamber is cooled to obtain the rock sample.

[0029] Furthermore, the particle size of the rock sample is below 0.180 mm.

[0030] The present invention has the following beneficial effects:

[0031] The method of the present invention cools and concentrates the product during the chromatographic separation of the rock sample, thereby shortening the sample processing time, reducing the temperature of the extracted product, and making the light components in the extracted product always in a solution environment that can make them more stable, thereby effectively avoiding the volatilization of the light components, ensuring that the light biomarker compounds in the rock can be extracted, providing a material basis for conducting oil source comparison or judging the maturity of organic matter in high-overmature areas, and having important significance for the exploration and development of high-overmature areas rich in light oil, condensate oil, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0033] Figure 1 is a schematic diagram of a packed chromatography column according to an embodiment of the present invention;

[0034] In the figure: burette 1, rock particle-dispersant mixture 2, alumina 3, silica gel 4, cotton wool 5, polytetrafluoroethylene valve 6;

[0035] Figure 2 is a curve showing the variation of the residual mass of a certain crude oil under natural exposure state over time in an embodiment of the present invention;

[0036] Figure 3 It is the change of the gas chromatogram of the remaining sample of a crude oil in a natural exposure state according to an embodiment of the present invention;

[0037] Figure 4 It is the change of the pyrolysis gas chromatogram of the pressure-maintained frozen core in the open state of the embodiment of the present invention;

[0038] Figure 5A This is the chromatogram of the product extracted from the block sample stored at room temperature with Ro=1.4% using conventional extraction method;

[0039] Figure 5B It is the chromatographic mass spectrum of the product extracted by the method of the present invention using the block sample with Ro=1.4% stored at room temperature;

[0040] Figure 6 It is a single adamantane chromatographic mass spectrum of the product extracted from a block sample with Ro=1.4% stored at room temperature using the method of the present invention. DETAILED DESCRIPTION

[0041] The present invention is described below based on embodiment, but it is worth noting that the present invention is not limited to these embodiments. In the detailed description of the present invention below, some specific details are described in detail. However, for the part not described in detail, those skilled in the art can also fully understand the present invention.

[0042] In addition, those skilled in the art should understand that the drawings are only provided to illustrate the purpose, features and advantages of the present invention, and the drawings are not actually drawn to scale.

[0043] At the same time, unless the context clearly requires otherwise, the words "include", "comprises" and similar words throughout the specification and claims should be interpreted as inclusive rather than exclusive or exhaustive; that is, the meaning is "including but not limited to".

[0044] In response to the problem of serious loss of light components in the products prepared by the background technology solution, the applicant tracked and analyzed the loss characteristics of light components in rocks and crude oil at room temperature. Figure 2 The figure shows the curve of the residual mass of a certain crude oil (about 3g) changing with time under natural exposure. It can be seen from the figure that the mass loss of the sample is 4.15% in 3h, 5.61% in 6h, 10.98% in 24h, 15.45% in 48h, and the final mass loss is more than 29.57%; the increase in volatilization rate is directly related to the increase in room temperature. The higher the temperature, the more obvious the increase in local volatilization rate. ② Figure 3 The figure shows the changes in the gas chromatogram of the remaining sample of a crude oil in a natural exposure state. It can be seen from the figure that with the extension of the storage time, the natural gas component is lost the fastest, and almost all of it is lost within 3 hours, followed by light hydrocarbons (C 6-14 ), heavy hydrocarbons (C 15+ )There is basically no loss. ③ Figure 4 The figure shows the changes in the pyrolysis gas chromatogram of a pressure-maintained frozen core under natural exposure. As can be seen from the figure, with the extension of storage time, the natural gas component is lost first and fastest, and is basically completely lost within 1-2 hours, followed by light hydrocarbons (C 6-14 ), heavy hydrocarbons (C 15+ ) There is basically no loss.

[0045] Through the above analysis of the loss characteristics of light components in rocks and crude oil at room temperature, it can be seen that: ① the loss amount of light components in soluble organic matter increases with time, and its loss rate is the largest in the initial stage (about 1.38% / h for crude oil); ② the loss rate of soluble organic matter is significantly affected by temperature. The higher the temperature, the greater the loss rate; ③ the loss rate of light hydrocarbons in crude oil is smaller than the loss rate of soluble organic matter in the core. It is speculated that this is because the amount of crude oil measured is large and the light components are dissolved in the crude oil, which reduces the volatilization rate of the light components to a certain extent.

[0046] According to the above analysis results, the method disclosed in the present invention controls the loss of light components in soluble organic matter by shortening the separation and extraction time, lowering the sample environment temperature, and maintaining the dissolved state of the product.

[0047] The embodiments of the present disclosure combine the extraction characteristics and formulate basic principles of lowering the temperature during sample crushing and reagent volatilization, reducing the number of reagent volatilizations, avoiding reagent volatilization to dryness, and shortening the analysis time to inhibit the loss of light biomarker compounds during the extraction process.

[0048] According to the above extraction principles, the extraction method of the embodiment of the present disclosure ensures that the loss of light components in soluble organic matter is effectively controlled during the extraction of biomarker compounds in rocks through the following specific measures:

[0049] ① Since the light components in the powdered cores or cuttings have basically evaporated, the rock samples used in the separation process must be block rocks (preferably pressure-maintained cores frozen with liquid nitrogen); the block rocks and the equipment surfaces that are in direct contact with the rocks need to be fully frozen and cooled before crushing to reduce the loss of light biomarker compounds when crushing the samples.

[0050] ② In order to improve the permeability of rock samples, the block rock needs to be quickly mixed with the dispersant after being crushed. The permeability of the rock sample is improved by adding the dispersant to prevent the rock sample from reducing the extraction and separation effect of the extraction solvent due to its low permeability. Then the rock sample-dispersant mixture is placed above the stationary phase of the chromatography column, and the extraction of organic matter and component separation are completed simultaneously in the chromatography column, thereby shortening the analysis time and removing the volatile reagent link.

[0051] ③ First, add an appropriate amount of n-hexane reagent to the receiving container before receiving the chromatographic separation product, use nitrogen to quickly volatilize the n-hexane, reduce the temperature of the receiving container, and form a low-temperature cold environment required for collecting samples. Then, during the chromatographic column separation process, the extracted product is low-temperature concentrated to further shorten the sample processing time and reduce the temperature of the concentrated product. The operation method is: during the column chromatography process, the separated product is concentrated with a nitrogen gas flow. The reagent absorbs a lot of heat during volatilization, which can significantly reduce the temperature of the separated product (the condensed water on the wall of the collection bottle can even freeze), forming a low-temperature cold environment.

[0052] ④ Since light components are more stable in a solution environment (because they are in a dissolved state and are not easy to dissipate), a certain amount of reagent should always be retained during the volatilization process to avoid evaporation of the reagent.

[0053] Referring to the above specific measures, the present disclosure describes in detail the method for extracting biomarker compounds from rocks, which is specifically performed in the following steps:

[0054] Step (1): Estimate the amount of core used (crushed to rock particles below 0.180 mm) according to the organic matter abundance of the rock. The minimum amount of rock used when chloroform "A" > 0.050% to 0.100% is 5 g, the minimum amount of rock used when chloroform "A" > 0.100% to 0.200% is 3 to 4 g, and the minimum amount of rock used when chloroform "A" > 0.200% is 2 to 3 g.

[0055] Step (2): prepare three glass bottles with good sealing performance and a capacity of 10 ml to 15 ml, and mark them as rock bottle, saturated hydrocarbon bottle, and aromatic hydrocarbon bottle respectively; use 30% to 50% of the amount of core used in step (1) as the dispersant, and the dispersant can be 80-200 mesh silica gel or diatomaceous earth; weigh the activated dispersant into the rock bottle, and quickly cover and seal it;

[0056] Step (3): Use a crusher after the sample chamber has been cooled to quickly crush the block rock that has been fully frozen and cooled, sieve out particles below 0.180 mm, put the rock particles into the rock bottle described in step (2) according to the estimated core usage in step (1), and quickly cover and seal it;

[0057] Step (4): Take Figure 1 The burette 1 with a capacity of 30ml-50ml and a diameter of 1cm and a polytetrafluoroethylene valve is shown. A proper amount of absorbent cotton 5 which has been extracted until the extract has no fluorescence is inserted into the bottom of the burette 1 as a support; after adjusting the polytetrafluoroethylene valve 6 to the open state, 3g of silica gel 4 (100-200 mesh, activated) and 2g of alumina 3 (100-200 mesh, activated) are added to the burette 1 in sequence, and the outer wall of the burette 1 is knocked; take the rock bottle described in step 3, shake it thoroughly, and then quickly add the rock-dispersant mixture into the burette 1, and knock the outer wall of the burette 1;

[0058] Step (5): adding n-hexane reagent to the burette 1 described in step (4), and quickly closing the polytetrafluoroethylene valve 6 when the n-hexane reagent is about to flow out from the polytetrafluoroethylene valve 6 below the burette; continuing to add n-hexane reagent, and stopping when the liquid level of the n-hexane reagent is about 5 ml above the interface of the rock particle-dispersant mixture 2; inserting a trapezoidal polytetrafluoroethylene plug at the top of the burette 1; and letting it soak for 8 hours;

[0059] Step (6): remove the polytetrafluoroethylene stopper on the top of the burette 1 in step (5), and adjust the polytetrafluoroethylene valve 6 of the burette 1 to an open state; add 40 ml of n-hexane into the burette 1 (add in small amounts and multiple times, 4 ml each time), and use the saturated hydrocarbon bottle (pre-cooled by nitrogen volatilization of n-hexane) described in step (2) to receive the solution. During the receiving process, use nitrogen gas flow to accelerate the volatilization of the reagent in the bottle, so that the solution in the bottle is always about 2 ml (the solution in the bottle must not be evaporated to dryness);

[0060] Step (7): When the level of the n-hexane reagent in step (6) is about 1 cm away from the interface of the rock particle-dispersant mixture 2, add 40 ml of a mixture of dichloromethane and n-hexane into the burette 1 (4 ml is added each time; dichloromethane:n-hexane=2:1). When about 4 ml of the mixture of dichloromethane and n-hexane flows into the interface of the rock particle-dispersant mixture 2, remove the saturated hydrocarbon bottle and seal it with a lid. Replace it with the aromatic hydrocarbon bottle described in step 2 (which has been pre-cooled by the nitrogen volatilization method of n-hexane) to receive the reagent. During the receiving process, a nitrogen gas flow is used to accelerate the volatilization of the reagent in the receiving bottle so that the solution in the bottle is always about 2 ml (the solution in the bottle must not be evaporated to dryness). After the solution in the burette 1 has flowed out, remove the aromatic hydrocarbon bottle and seal it with a lid.

[0061] The applicant extracted biomarker compounds from a block rock sample with Ro=1.4% stored at room temperature using conventional methods and the method of the embodiment of the present disclosure, and compared the chromatographic mass spectrometry of the extracted products. Figure 5A This is the chromatographic mass spectrum of the product extracted by the conventional extraction method. 15 The previous components have basically evaporated, and due to the high maturity of the sample, the conventional biomarker compounds in it have been seriously interfered, making it impossible to carry out biomarker compound analysis; Figure 5B is the chromatogram of the product extracted by the method of the embodiment of the present disclosure, C 10 The biomarker compounds after it can be detected, so the extraction product obtained by the extraction method of the embodiment of the present disclosure can be carried out as follows Figure 6 The monoadamantane (C 11~13 ) and other biomarker compound analysis.

[0062] In addition, it can be seen from the above description that the method of this embodiment also has the advantages of less consumption of rocks and reagents, less toxicity of the reagents used, simple operation and fast analysis speed.

[0063] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

Claims

1. A method for extracting biomarker compounds from rocks, characterized in that: include: Chromatographic separation of rock samples; The product separated by chromatography is cooled and concentrated during the process of flowing into the receiving container; The chromatographic extraction is performed before the chromatographic separation; The chromatographic extraction is to place the rock sample on top of a chromatographic column stationary phase, and add n-hexane into the chromatographic column to extract the organic matter in the rock sample; The cooling and concentrating method comprises: Passing nitrogen into the receiving container; Using the nitrogen gas flow to carry away the separation reagent in the product to concentrate the product and reduce the temperature of the product; Pre-cooling the receiving container; The rock sample is subjected to freezing or cooling treatment before being loaded into the chromatography column, and the freezing or cooling treatment method includes: Freezing or cooling the block rock to be extracted so that the block rock is below normal temperature; The block rock is crushed in an environment below normal temperature or under the condition that the sample chamber is cooled to obtain the rock sample.

2. The method for extracting biomarker compounds from rocks according to claim 1, characterized in that: The receiving container retains a minimum amount of the separation reagent to keep the light components in the product in a solution environment.

3. The method for extracting biomarker compounds from rocks according to claim 2, characterized in that: The separation reagent is n-hexane and a mixed reagent of dichloromethane and n-hexane; The n-hexane is used to elute the saturated hydrocarbon components in the rock sample; The dichloromethane and n-hexane mixed reagent is used to elute the aromatic components in the rock sample.

4. The method for extracting biomarker compounds from rocks according to claim 3, characterized in that: Soak in n-hexane for 8 hours before extraction.

5. The method for extracting biomarker compounds from rocks according to claim 4, characterized in that: A dispersant is added to the rock sample.

6. The method for extracting biomarker compounds from rocks according to claim 5, characterized in that: The dispersant is 80-200 mesh silica gel or diatomaceous earth.

7. The method for extracting biomarker compounds from rocks according to claim 6, characterized in that: The amount of the dispersant added is 30%-50% of the weight of the rock sample.

8. The method for extracting biomarker compounds from rocks according to claim 7, characterized in that: The particle size of the rock sample is below 0.180 mm.

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