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CN-122016898-A - Iodized imitation-epoxy resin embedding preparation method for SEM-EDS analysis of coalbed methane reservoir samples

CN122016898ACN 122016898 ACN122016898 ACN 122016898ACN-122016898-A

Abstract

The invention discloses an iodoform-epoxy resin embedding preparation method for SEM-EDS analysis of a coalbed methane reservoir sample, and relates to the technical field of reservoir sample detection. The method comprises the steps of firstly cutting, cleaning and low-temperature vacuum drying a coalbed methane reservoir sample, then adding iodoform into epoxy resin, fully stirring until the iodoform is completely dissolved to form uniform and clear mixed liquid, then adding a curing agent, stirring at a low speed, carrying out natural and vacuum combined defoaming, then embedding and curing the sample, finally obtaining a flat observation surface through step-by-step mechanical polishing and argon ion polishing, and carrying out conductive treatment to obtain the finished product. The invention effectively avoids the aggregation of the iodized crystal and the introduction of bubbles by the process of firstly dissolving the iodized and then adding the curing agent, remarkably improves the contrast of back scattering electronic images, protects the primary pore and cutting structure of coal and rock, improves the EDS quantitative analysis precision, has controllable process parameters and good repeatability, is suitable for various samples such as coal and rock, coal-containing clastic rock, coal seam gangue and the like, and can provide high-quality sample preparation guarantee for microcosmic characterization of a coal seam gas reservoir.

Inventors

  • PING XIAOLIN
  • BAI LIQIANG
  • Bai Zhenqiang

Assignees

  • 北京长垣石油科技有限公司

Dates

Publication Date
20260512
Application Date
20260404

Claims (10)

  1. 1. The iodized imitation-epoxy resin embedding preparation method for SEM-EDS analysis of the coalbed methane reservoir samples is characterized by comprising the following steps: (1) Sample pretreatment, namely selecting a coalbed methane reservoir sample, cutting the coalbed methane reservoir sample to a preset size, and carrying out ultrasonic cleaning by absolute ethyl alcohol and low-temperature vacuum drying for later use; (2) Pre-treating epoxy resin, namely weighing low-viscosity epoxy resin and placing the epoxy resin in a clean drying container for standby; (3) Adding the iodoform into the epoxy resin, stirring until the iodoform is completely dissolved to form a uniformly clear yellow mixed solution, and adding no curing agent at the stage; (4) Mixing, solidifying and defoaming, namely adding a curing agent into the mixed solution, uniformly stirring at a low speed, and removing bubbles through natural standing and vacuum defoaming; (5) Sample embedding and curing, namely placing the pretreated sample into a mould, injecting a mixed solution, selecting room temperature curing or constant temperature curing according to the type of the sample, and demoulding after curing to obtain an embedding body; (6) Polishing and conducting treatment, namely performing step-by-step mechanical polishing and argon ion polishing on the embedded body, cleaning and drying, and then performing carbon spraying or metal spraying treatment to finish sample preparation.
  2. 2. The method according to claim 1, wherein the sample size in the step (1) is 5mm×5mm×2mm to 8mm×8mm×3mm, the ultrasonic cleaning time is 3 to 5 minutes, the low-temperature vacuum drying temperature is 35 to 50 ℃, and the drying time is 2 to 4 hours.
  3. 3. The method of claim 1, wherein the mass of the iodoform in the step (3) is 20% -40% of the mass of the epoxy resin, magnetic stirring or manual stirring is adopted, the stirring speed is 150-250 r/min, the stirring time is 15-30 minutes, and the stirring process is carried out under a shading condition.
  4. 4. The method of claim 1, wherein the curing agent in the step (4) is an amine curing agent, the mass of the curing agent is 30% -50% of the mass of the epoxy resin, the stirring speed after the curing agent is added is 100-200 r/min, the stirring time is 5-10 minutes, the vacuum degree of vacuum defoaming is 0.08-0.1 MPa, and the defoaming time is 3-5 minutes.
  5. 5. The method according to claim 1, wherein in the embedding process in the step (5), the liquid level of the mixed solution is 1-2 mm higher than the surface of the sample, the room temperature curing condition is 25+ -2 ℃, the curing time is 24-48 hours, the constant temperature curing condition is 60+ -5 ℃, and the curing time is 2-4 hours.
  6. 6. The method according to claim 1, wherein in the step (6), step-by-step mechanical polishing is sequentially performed by adopting 800# sand paper, 1200# sand paper, 2000# sand paper and 5000# sand paper, wherein the argon ion polishing acceleration voltage is 5-8 kV, the time is 10-15 minutes, the carbon spraying thickness is 10-20 nm, and the metal spraying thickness is 5-10 nm.
  7. 7. The method of claim 1, wherein for the soft and fragile coal rock sample, the cutting size is 5mm x 2mm, the drying temperature is 35-40 ℃, the iodoform addition ratio is 25-30%, and the curing is performed at room temperature for 36-48 hours.
  8. 8. The method of claim 1, wherein for high clay content coal rock samples, the ultrasonic cleaning time is prolonged to 5 minutes, the curing agent ratio is 35% -40%, and the argon ion polishing time is prolonged to 15 minutes.
  9. 9. The method of claim 1, wherein the iodized addition ratio is 30% -35% for the carbonate-containing cemented coal rock or coal seam gangue sample, and the curing is performed at a constant temperature of 60 ℃.
  10. 10. The method according to any one of claims 1 to 9, wherein the method is suitable for SEM-EDS and BSE imaging analysis of coal rock, coal-bearing clastic rock, coal seam gangue, and is scalable for the embedded preparation of shale, tight sandstone reservoir samples.

Description

Iodized imitation-epoxy resin embedding preparation method for SEM-EDS analysis of coalbed methane reservoir samples Technical Field The invention relates to the technical field of detection and preparation of samples of a coal bed gas reservoir, in particular to an iodized-epoxy resin embedding preparation method suitable for imaging analysis of various samples (coal rock, coal-bearing clastic rock, coal bed gangue inclusion and the like) of the coal bed gas reservoir, an energy spectrum analyzer (EDS) and a Back Scattering Electron (BSE), which can be widely applied to relevant experimental detection scenes such as microstructure characterization, mineral component analysis, pore seepage characteristic evaluation and the like of the coal bed gas reservoir. Background The coalbed methane reservoir samples (mainly comprising coal rock, coal-bearing clastic rock, coal bed gangue and the like) are core carriers for researching coalbed methane storage, seepage and development potential, and the microcosmic pore structures (micropores, mesopores and macropores), mineral occurrence states, mineral distribution characteristics and cutting crack development conditions of the coalbed methane reservoir samples directly determine the adsorption capacity, seepage efficiency and development effect of the coalbed methane. The SEM-EDS detection technology has become the main stream means for representing micro characteristics of the coalbed methane reservoir sample by virtue of the advantages of high resolution and high sensitivity, and the quality of sample preparation directly influences the authenticity, accuracy and reliability of detection results, thus being an important premise for subsequent reservoir evaluation and development scheme optimization. At present, the conventional preparation process for SEM-EDS analysis of a coalbed methane reservoir sample mainly comprises direct embedding and mechanical polishing of epoxy resin, and part of the process can add iodoform to improve BSE imaging contrast, but the prior art has the following prominent technical defects generally, and the accurate detection requirement is difficult to meet: 1. In the conventional process, the iodized crystal is difficult to dissolve completely, and local crystallization and agglomeration are easy to occur, so that the boundary of reservoir sample matrixes, pores, resin and minerals in BSE imaging is fuzzy, the contrast difference is not obvious, components cannot be distinguished clearly, and the microstructure observation and EDS quantitative analysis are interfered; 2. The original structure of the sample is easy to be damaged, the stirring speed and time are not controlled in the stirring process, a large amount of bubbles are easy to be introduced in the vigorous stirring process, the bubbles are filled in pores of the sample or are attached to the surface of the sample, the original pore, cutting and fracture structures of a coalbed methane reservoir sample are damaged, the detection data are distorted, and the actual microscopic characteristics of the reservoir cannot be truly reflected; 3. the sample type of the coalbed methane reservoir is various, including soft and fragile soft coal rock, high clay content coal rock, carbonate-containing cemented coal rock, coal seam gangue and the like, the existing preparation process is not specific to the optimized parameters of different types of samples, the problems of loose combination of an embedding layer and the samples, sample falling, pore collapse, serious surface scratch and the like are easy to occur, and the adaptability is poor; 4. The process controllability is poor, the repeatability is poor, key parameters such as the addition proportion of the iodoform, the stirring time, the curing condition and the like are not clarified in the prior art, the quality difference of samples prepared by different operators is large, the repeatability of the detection result is poor, and the laboratory standardized detection requirement is difficult to meet; 5. The sample is easy to oxidize, so that the detection stability is influenced, namely the surface activity of the coalbed methane reservoir sample (especially coal rock) is higher, the sample is easy to generate oxidation reaction when being exposed to air in the conventional preparation process, the surface composition and the microscopic morphology of the sample are changed, and the EDS mineral analysis and SEM imaging quality are further interfered. At present, a special preparation method which has the advantages of uniformly dispersing iodoform, fidelity of a primary structure of a sample, crystallization prevention, bubble prevention, adaptation to various types of coalbed methane reservoir samples, controllable process and good repeatability is lacked in the prior art, the high-precision detection requirement of microcosmic characterization of the coalbed methane reservoir cannot be met, and a preparation scheme with perfect pr