阅读说明：本技术 用于扫描电镜分析的含油岩石样品的制备方法 (Preparation method of oil-containing rock sample for scanning electron microscope analysis ) 是由 刘金 王剑 罗正江 邓泳 王睿 张晓刚 王桂君 鲁锋 陈俊 雷海燕 孟颖 张锡 于 2020-04-30 设计创作，主要内容包括：本发明提供了一种用于扫描电镜的含油岩石样品的制备方法。该方法该制备方法包括：对含油岩石样品进行断面上桩；将进行断面上桩之后的含油岩石样品置于80～120℃进行干燥；在干燥后的含油岩石样品上溅射导电膜。该方法通过先在80～120℃干燥将石油馏分中的轻馏分进行挥发分离,这样能够在有效保证矿物的原貌的前提下,减少后期扫描电镜成像时石油馏分的渗出。而且,进一步采用离子溅射仪这种低温型镀膜设备,在接近于室温条件下进行镀膜过程,也能够有效减少石油馏分的渗流和挥发,防止污染扫描电镜,同时也能在一定程度上解决样品导电性能变差,扫描电镜照片荷电现象严重的问题。(The invention provides a preparation method of an oil-containing rock sample for a scanning electron microscope. The preparation method comprises the following steps: piling the section of the oil-bearing rock sample; drying the oil-bearing rock sample after pile feeding on the section at 80-120 ℃; and sputtering a conductive film on the dried oil-bearing rock sample. According to the method, the light fractions in the petroleum fractions are volatilized and separated by drying at 80-120 ℃, so that the seepage of the petroleum fractions during later scanning electron microscope imaging can be reduced on the premise of effectively ensuring the original appearance of minerals. Moreover, the low-temperature type coating equipment such as an ion sputtering instrument is further adopted to carry out the coating process under the condition close to room temperature, so that the seepage and volatilization of petroleum fractions can be effectively reduced, the pollution to a scanning electron microscope is prevented, and the problems of poor conductivity of a sample and serious charge phenomenon of a scanning electron microscope photo can be solved to a certain extent.)

1. A preparation method of an oil-bearing rock sample for scanning electron microscope analysis is characterized by comprising the following steps:

carrying out section piling on the oil-bearing rock sample;

drying the oil-bearing rock sample after pile feeding on the section at 80-120 ℃;

and sputtering a conductive film on the dried oil-bearing rock sample.

2. The method of claim 1, wherein after drying the petroliferous rock sample and before sputtering a conductive film on the dried petroliferous rock sample, the method further comprises: and spraying a carbon conductive film on the dried petroliferous rock sample.

3. The method according to claim 1, wherein the oily type of the oil-bearing rock sample is medium oil or heavy oil, and the thickness of the carbon conductive layer is 18-22 nm.

4. The method according to claim 1, wherein the oily type of the oil-bearing rock sample is light oil, and the carbon conductive layer is sprayed to a thickness of 28 to 35 nm.

5. The method according to claim 3 or 4, wherein the temperature of the thermal spraying is 30 to 50 ℃.

6. The method according to claim 1, wherein the conductive film to be sputtered is a gold conductive film.

7. The method according to claim 5, wherein the sputtering temperature is 20 to 30 ℃.

8. The method according to claim 1, wherein the gold conductive film has a thickness of 18 to 22 nm.

9. The method for preparing the paint of claim 1, wherein the drying is oven drying.

10. The method of claim 1, wherein the drying time is 8-12 hours.

Technical Field

The invention relates to the field of scanning electron microscopes of oil-containing rocks, in particular to a preparation method of an oil-containing rock sample for scanning electron microscope analysis.

Background

The scanning electron microscope has high resolution, and can provide important information in the aspects of micro-nano rock texture, pore structure, diagenesis and the like for oil and gas reservoir samples.

However, part of oil and gas reservoir samples are rich in oil (the oil content is at least equal to oil immersion), and the samples cannot meet the requirement of conventional scanning electron microscope analysis (except for a variable air pressure scanning electron microscope and a scanning electron microscope with a frozen sample stage) on sample conductivity after being sprayed with a conductive film, so that the charging phenomenon of a scanning electron microscope photo is serious. The reason is as follows: firstly, the petroleum composition is complex, when a conductive film is evaporated, partial distillate is caused to permeate to the surface of the conductive film due to high temperature, and the conductivity of the conductive film is damaged (table 1); secondly, when the scanning electron microscope is used for analysis, the heat generated by bombarding the surface of the sample by the high-energy electron beam drives the petroleum components in the sample to permeate the surface of the sample, so that the conductivity of the sample is deteriorated.

At present, in order to solve this problem, there are three conventional approaches: firstly, a sample is not subjected to film coating treatment, and the sample is directly observed by using a variable air pressure scanning electron microscope. However, the method is only limited to an environmental scanning electron microscope and a scanning electron microscope equipped with a VP diaphragm, and is easy to cause the pollution of a sample chamber and an electron optical system; ② before the sample preparation, the oil is washed by organic solvent such as benzene. The method has the disadvantages that an oil-containing sample (the oil-containing grade is oil-immersed grade or above) is easy to loosen after oil washing, and the sample meeting the specification requirements (the length is less than 1cm, the width is less than 1cm, and the height is less than 1cm) cannot be prepared; thirdly, the frozen sample stage is used for observation, and the defect is that the frozen sample stage with high price needs to be equipped.

Aiming at the problem of serious charging phenomenon caused by preparing a scanning electron microscope sample by spraying a conductive film in the prior art, a reasonable solution is not provided at present.

Disclosure of Invention

The invention provides a preparation method of an oil-containing rock sample suitable for analysis of a scanning electron microscope, which aims to solve the problem that the sample prepared by spraying a conductive film for the scanning electron microscope in the prior art has serious charge phenomenon.

According to the invention, the preparation method of the oil-containing rock sample for the analysis of the scanning electron microscope is provided, and comprises the following steps: piling the section of the oil-bearing rock sample; drying the oil-bearing rock sample after pile feeding on the section at 80-120 ℃; and sputtering a conductive film on the dried oil-bearing rock sample.

Further, after drying the petroliferous rock sample and before sputtering the conductive film on the dried petroliferous rock sample, the method further comprises: a carbon conductive film was sprayed on the dried petroliferous rock sample.

Furthermore, the oil type of the oil-bearing rock sample is medium oil or heavy oil, and the thickness of the sprayed carbon conducting layer is 15-22 nm.

Furthermore, the oil type of the oil-bearing rock sample is light oil, and the thickness of the sprayed carbon conducting layer is 15-35 nm.

Further, the spraying temperature is 30-50 ℃.

Further, the sputtered conductive film is a gold conductive film.

Further, the sputtering temperature is 20-30 ℃.

Further, the thickness of the gold conductive film is 15 to 25 nm.

Further, drying is carried out by using an oven.

Further, the drying time is 8-12 h.

In the invention, an oil-bearing rock sample is selected according to the requirements of a scanning electron microscope; piling the section of the oil-bearing rock sample; drying the oil-bearing rock sample after the pile is placed on the section; a conductive film is sputtered on the dried rock sample. According to the method, the light fractions in the petroleum fractions are volatilized and separated by drying at 80-120 ℃, so that the seepage of the petroleum fractions during later scanning electron microscope imaging can be reduced on the premise of effectively ensuring the original appearance of minerals. Moreover, the low-temperature type coating equipment such as an ion sputtering instrument is further adopted to carry out the coating process under the condition close to room temperature, so that the seepage and volatilization of petroleum fractions can be effectively reduced, the pollution to a scanning electron microscope is prevented, and the problems of poor conductivity of a sample and serious charge phenomenon of a scanning electron microscope photo can be solved to a certain extent.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 is a flow chart of a method for preparing an oil-bearing rock sample suitable for scanning electron microscopy analysis according to a preferred embodiment of the present invention;

FIG. 2 is a schematic structural view of a sample of oil-bearing rock after preparation is complete, according to a preferred embodiment of the invention;

FIG. 3 is a scanning electron micrograph of a light oil rock-containing sample according to a preferred embodiment of the present invention;

FIG. 4 is a scanning electron micrograph of a heavy oil bearing rock sample according to a preferred embodiment of the present invention;

FIG. 5 is a scanning electron micrograph of a heavy oilstone-containing sample according to example 2 of the present invention;

FIG. 6 is a scanning electron micrograph of a heavy oil-bearing rock sample according to one example 3 of the present invention;

FIG. 7 is a scanning electron micrograph of a heavy oilstone-containing sample from comparative example 1 according to the prior art;

FIG. 8 is a scanning electron micrograph of an oil free rock sample according to the prior art;

FIG. 9 is a scanning electron micrograph of an oil bearing rock sample at extreme magnification according to a preferred embodiment of the present application.

Detailed Description

The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In order to solve the problem of conventional scanning electron microscope observation of rock samples with oil content grades of oil immersion and above, the key is to process the problems of seepage and volatilization of oil at higher temperature. The solving strategy is as follows: firstly, low-temperature coating equipment is used for preparing a sample, and high-temperature coating equipment is not used; and secondly, removing seepage and volatile petroleum fractions caused by high temperature of electron beams of a scanning electron microscope during sample preparation.

The common devices for plating the conductive film on the rock sample are two types, namely a high-temperature evaporation plating instrument and an ion sputtering instrument. The high-temperature evaporation instrument utilizes high temperature to melt a coating material in vacuum and spray the coating material on a sample, the coating method can generate high temperature (the melting point of gold is 1063 ℃), and the phenomena of most petroleum fraction seepage and volatilization can be generated during coating, so that the high-temperature evaporation instrument is not suitable for coating of an oil-bearing rock sample. The ion sputtering instrument is low-temperature type coating equipment, the temperature is close to room temperature in the coating process, the seepage and volatilization of petroleum fractions can be effectively reduced, and the ion sputtering instrument is suitable for coating of oil-bearing rock samples.

And removing seepage and volatile petroleum fractions caused by high temperature of the electron beam of the scanning electron microscope, and drying the sample by using an oven. But too high sample baking temperature for the rock sample can cause part of minerals to be changed, and the original rock mineral type is damaged, which is against the original purpose of the rock sample observed by a scanning electron microscope. Especially for hydrous minerals, the temperature is greatly affected. The mineral water types include adsorption water (destruction temperature 110 ℃), interlayer water (destruction temperature 110 ℃), zeolite water (destruction temperature 300 ℃ -400 ℃), crystal water (destruction temperature 100 ℃ -600 ℃) and structural water (destruction temperature 600 ℃ -1000 ℃). Experience accumulation shows that the original appearance of the minerals can be effectively ensured at 80-100 ℃ and light fractions in petroleum fractions can be volatilized and separated (Table 1).

Table 1: composition of petroleum fractions

The sample preparation is carried out by adopting a method combining sample drying at 80-100 ℃ and spraying of an ion sputtering instrument, under a conventional scanning electron microscope, an accelerating voltage of 15-20KV is adopted for observation, and the temperature generated by an electron beam of the scanning electron microscope can still enable a part of light-medium fraction to seep to the surface of the sample, so that a charge phenomenon is generated, and the image quality is influenced.

The inventor further researches and finds that through multiple times of trials and experience accumulation, the problem that light-medium fractions seep to the surface of a sample caused by the temperature of an electron beam can be effectively solved by additionally spraying a carbon conducting film between two steps of sample baking at the temperature of 80-100 ℃ and spraying of an ion sputtering instrument.

Therefore, the rock sample with oil content level of oil immersion level or above can be observed and analyzed by a conventional scanning electron microscope through sample baking (80-100 ℃), sputtering of the carbon conductive film and sputtering of the gold conductive film.

On the basis of the above research results, the applicant proposed the technical solution of the present application. In an exemplary embodiment of the present application, a method for preparing an oil-bearing rock sample for a scanning electron microscope is provided, and fig. 1 is a flowchart of a method for preparing an oil-bearing rock sample for a scanning electron microscope according to an embodiment of the present invention. As shown in fig. 1, the process includes the following steps: piling the section of the oil-bearing rock sample; drying the oil-bearing rock sample after pile feeding on the section at 80-120 ℃; and sputtering a conductive film on the dried rock sample to obtain the oil-containing rock sample for the scanning electron microscope.

According to the preparation method of the oil-bearing rock sample for scanning electron microscope analysis, the light fraction in the petroleum fraction is volatilized and separated by drying at 80-120 ℃, so that the seepage of the petroleum fraction during later scanning electron microscope imaging can be reduced on the premise of effectively ensuring the original appearance of minerals. Moreover, the low-temperature type coating equipment such as an ion sputtering instrument is further adopted to carry out the coating process under the condition close to room temperature, so that the seepage and volatilization of petroleum fractions can be effectively reduced, the pollution to a scanning electron microscope is prevented, and the problems of poor conductivity of a sample and serious charge phenomenon of a scanning electron microscope photo can be solved.

As mentioned above, the sample preparation is carried out by adopting a method combining sample drying at 80-100 ℃ and spraying of an ion sputtering instrument, under a conventional scanning electron microscope, an accelerating voltage of 15-20KV is adopted for observation, and the temperature generated by an electron beam of the scanning electron microscope can still enable a part of light-medium fraction to seep to the surface of the sample, so that a charging phenomenon is generated, and the image quality is influenced.

In order to further reduce the heat generated by the bombardment of the high-energy electron beam on the surface of the sample when the petroleum fraction is analyzed by the scanning electron microscope, the method drives the petroleum component in the sample to penetrate the surface of the sample, and in a preferred embodiment of the application, the method further comprises the step of spraying a carbon conductive film on the dried rock sample before the conductive film is sprayed on the dried rock sample. The carbon conductive film can enhance the viscosity of petroleum on the surface of the sample, prevent the temperature generated by the electron beam from causing partial light-medium fraction to seep to the surface of the sample, and simultaneously enhance the adhesion capability of the subsequent gold conductive film on the surface of the sample.

The thickness of the particular sputtered carbon-conducting film may be adjusted as appropriate to the oil content and/or oil type of the rock sample. Preferably, the heavy oil containing rock sample is sputtered with about a 20nm carbon conducting film and the light oil containing rock sample is sputtered with about a 30nm carbon conducting film.

The drying time at the above temperature is not particularly limited, so as not to change the rock morphology. Preferably, the temperature can be 80-100 ℃ and the time can be 8-12 h.

The sputtering conductive film is preferably a gold conductive film having excellent sputtering conductivity. The thickness of the sputtered gold conductive film is comprehensively determined according to the surface flatness of the sample, the weight degree of the contained oil and the oil-containing grade. The whole requirement of SY/T5162-.

The following is further illustrated in connection with the preparation of conventional scanning electron microscope samples of rocks containing oil grades at and above oil immersion.

Two types of petroliferous rock samples were selected for the experiments below.

Sample type 1: j well, oil grade is rich oil-oil immersion, oil type is light oil, the number is 11.

Sample type 2: oil sands, oil grade rich oil, oil type heavy oil, quantity 10.