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CN-122016555-A - Method for measuring true density of coal rock

CN122016555ACN 122016555 ACN122016555 ACN 122016555ACN-122016555-A

Abstract

The invention provides a method for measuring true density of coal and rock, which can efficiently and accurately identify different evolution stages of coal and rock in complex geological history. These stages range from initial diagenetic to later metamorphic effects, each of which is accompanied by significant changes in the physical and chemical properties of the coal rock. In addition, the method has excellent distinguishing capability, can clearly and effectively distinguish the carbonaceous mudstone from other types of coal rocks, is used as a special sedimentary rock, has complex components and often contains higher organic matters, and has obvious difference with the conventional coal rocks in various aspects. Therefore, the invention is not only helpful for deepening understanding of the cause and evolution process of coal and rock, but also provides important technical support and scientific basis for the fields of exploration, development of coal resources, environmental protection and the like.

Inventors

  • SHEN HUA
  • LI ZHONGCHENG
  • HAN HAOTIAN
  • LIU GUODONG
  • TANG MIN
  • DONG CHANGCHUN
  • SHEN XIA

Assignees

  • 中国石油天然气股份有限公司

Dates

Publication Date
20260512
Application Date
20241111

Claims (10)

  1. 1. A method for determining true density of coal rock, comprising the steps of: S1, preprocessing a sample to be detected, namely taking a representative sample, crushing and grinding the representative sample into powder, sieving the powder, and drying the powder; S2, boiling distilled water and cooling to room temperature; s3, cleaning the gravity bottle with distilled water, and injecting distilled water; s4, accurately weighing a pulverized coal analysis sample, and completely transferring the pulverized coal analysis sample into a specific gravity bottle through a small necked funnel; s5, injecting sodium dodecyl benzene sulfonate or sodium dodecyl sulfate solution into the specific gravity bottle, standing to saturate the sample, and then adding distilled water along the wall of the bottle; S6, the specific gravity bottle is moved into a water bath or a sand bath to be boiled so as to remove adsorbed gas; s7, taking out the specific gravity bottle, adding pure water cooled to room temperature, and then placing the bottle in a thermostat to keep the temperature for 1-3 hours; s8, adding a certain amount of pure water at room temperature to the bottle mouth, and covering the bottle stopper to ensure that no bubbles exist in the specific gravity bottle and the capillary tube; S9, wiping the specific gravity bottle, and weighing the mass M 1 of the specific gravity bottle after sample addition; S10, correcting a specific gravity bottle, weighing the specific gravity bottle, and obtaining M 2 by hydration weight; S11, calculating the true density of the sample.
  2. 2. The method according to claim 1, wherein in the step S11, the calculation formula is as follows: wherein: d-sample true density, g/cm 3 ; M is the mass of the sample, g; M 1 -g, heavy than the weight of the bottle, the coal sample, the lubricant and the distilled water; M 2 -distilled hydration weight of the specific gravity bottle and the full bottle, g; d s -the density of distilled water at room temperature, g/cm 3 ,d s ≈1g/cm 3 .
  3. 3. The method according to claim 1, wherein in the step S1, the sample is crushed into small pieces by a crusher, then is crushed into powder by a grinder, and passes through a sample separating sieve with a pore diameter of 0.2mm, the iron filings mixed into the coal powder are sucked by a magnet, and the prepared coal sample is dried for 24 hours at 105-110 ℃ and then is taken out and cooled to room temperature by a dryer.
  4. 4. The method according to claim 1, wherein in step S1, a representative sample is 250-350g.
  5. 5. The method according to claim 1, wherein the step S4 is accurate to ±0.001g.
  6. 6. The method according to claim 1, wherein the step S5 is to fill 3-4mL of a sodium dodecyl benzene sulfonate or sodium dodecyl sulfate solution having a concentration of 2% into the pycnometer with a measuring cylinder, to soak the sample by standing for 15min, and then to add 25mL of distilled water along the wall of the bottle.
  7. 7. The method according to claim 1, wherein the step S7 is to take out the pycnometer, add boiled distilled water to a position 1cm below the bottle mouth, cool to room temperature, then place in a thermostat of 20 Shi 0.5 ℃ or slightly below room temperature, keep the temperature for 1h, and record the room temperature.
  8. 8. The method of claim 7, wherein the sample is placed overnight with a sodium dodecyl sulfate solution.
  9. 9. The method of claim 1, wherein step S8 is performed by capping the bottle stopper with a straw to fill the bottle neck with boiled 20 ℃ or room temperature distilled water, and overflowing the excess water from the capillary tube on the bottle stopper.
  10. 10. The method according to claim 1, wherein the calculation formula of step S10 is as follows: wherein: t 1 -correction temperature; T 2 -calculating the temperature; M 2 -the bottle hydration weight, g, at temperature T 2 ; M 2 ' -the bottle hydration weight, g, at temperature T 1 ; M 4 -the pycnometer mass, g, at temperature T 1 ; d s1 -the density of water, g/cm 3 , at temperature T 1 ; d s2 -the density of water, g/cm 3 , at temperature T 2 ; Epsilon γ -glass expansion coefficient, epsilon γ ＝2.4×10 -5 C -1 .

Description

Method for measuring true density of coal rock Technical Field The invention relates to the technical field of testing of the Dan Zhen density of common reservoir rocks such as coal, shale and sandstone, in particular to the measurement of the true density of coal and rock. Background Density is one of the core indexes for evaluating the physical properties of coal and rock, and plays a very important role in coal and rock research. The method can reflect the compactness, the porosity and the compactness of the internal structure of the coal rock, and also can predict the important basis of the performance, the permeability and the gas content of the coal rock reservoir. In the deep region of the south of the Songliao basin with complex geological structure, a plurality of fracture pits and complex stratum structures are formed due to multi-period structural movement, and the geological features provide favorable conditions for the development of the coal bed, so that the region is a multi-layer system developed coal bed and the resource reserve is rich. However, this complex geological background also increases the difficulty and risk of coal and rock exploration, making accurate assessment of coal and rock properties a critical task. By accurately measuring and analyzing the density of the coal and rock, the reservoir property, the fluid migration rule and the mining potential of the coal and rock can be further revealed, scientific basis and technical support are provided for effective exploration and development of deep coal and rock resources in the south of the Songliao basin, and the method has important significance for accurately evaluating the physical properties of the coal and rock. The prior art CN103439238A discloses a method for measuring closed porosity in coal shale, namely, an open pore volume is obtained through testing of true density and apparent density, and then the closed pore volume is obtained through a methane experiment, so that the closed porosity can be accurately measured and calculated, the total porosity test result is more similar to the underground true value of the coal shale, and the true density of a sample is dr through a coal and rock true density measuring method GB/T23561.2-2009, but the method cannot deepen the cause and evolution process of the coal and the rock. The prior art CN 109269938A discloses a method for testing true densities of coal and rock. The invention discloses a method for testing true densities of coal and rock, which comprises the steps of determining stratum temperature and pressure of a sample, testing the mass and volume of a sample barrel under an empty condition, calculating the mass and volume of the sample under the stratum temperature and condition and calculating the true densities of the sample under the stratum temperature and condition, wherein the method can avoid damage to the sample in the sample preparation process as far as possible, and reflect the true densities of the coal and the rock under the stratum temperature and pressure condition, but lack deep research on the cause and evolution process of the coal and the rock. Disclosure of Invention In order to achieve the above purpose, the technical scheme of the invention is as follows: s1, pretreatment of a sample to be tested Taking 250-350g of representative sample, crushing and grinding into powder, sieving and drying; S2, boiling distilled water and cooling to room temperature; s3, taking a specific gravity bottle, cleaning with distilled water, and injecting one third of distilled water; s4, accurately weighing 2-3g (M) of coal dust analysis samples with granularity smaller than 0.2mm, and completely transferring the coal dust analysis samples into a specific gravity bottle through a necked funnel; S5, injecting 3-4mL of 2% sodium dodecyl benzene sulfonate or sodium dodecyl sulfate solution into the specific gravity bottle, standing to saturate the sample, and then adding 25mL of distilled water along the bottle wall; s6, the specific gravity bottle is moved into a water bath or a sand bath to be boiled for 20-30min so as to remove adsorbed gas; s7, taking out the specific gravity bottle, adding pure water cooled to room temperature, and then placing the bottle in a thermostat to keep the temperature for 1-3 hours; s8, adding a certain amount of pure water at room temperature to the bottle mouth, and covering the bottle stopper to ensure that no bubbles exist in the specific gravity bottle and the capillary tube; S9, wiping the specific gravity bottle, and weighing the mass M 1 of the specific gravity bottle after sample addition; S10, correcting a specific gravity bottle, and weighing the bottle to obtain M 2 by hydration; S11, calculating the true density of the sample. Further, in the step S1, the sample is crushed into small pieces by a crusher, and then ground into powder by a grinder, and all of the powder passes through a sample separating sieve with a pore diamete