Antipovich Y.V. Methods for determining closed porosity in clastic grains of rocks

Details

Parent Category: Geo-Technical Mechanics, 2018

Category: Geo-Technical Mechanics, 2018, Issue 142

Geoteh. meh. 2018, 142, 67-72

DOI: https://doi.org/10.15407/geotm2018.142.067

METHODS FOR DETERMINING CLOSED POROSITY IN CLASTIC GRAINS OF ROCKS

Antipovich Y.V.

Author:

Antipovich Y.V., Master of Science (M.Sc.), Junior Researcher (IGTM, NAS of Ukraine)

UDC: 552.12.08:539.217.1

Language: Ukrainian

Annotation.

Results of the study of closed porosity in clastic grains of gas-bearing sandstones of the Donbass are presented. Grain closed porosity is created by various types of gas inclusions in clastic grains of rocks. They are mainly represented by isolated inclusions or in the form of Bohm strips, the subsequent transformation of which creates a so-called "spongy" structure. The purpose of this work was to develop a method for determining volume of gas inclusions in clastic grains of rocks by using an optical microscope. During the investigation of thin sections of sandstones by optical microscope at great magnification (from 1000 to 1200 times using an immersion liquid), the most informative area of thin sections with a different number of gas inclusions are determined. With the help of the object-micrometer, size of the investigated area of the thin section and size of gas inclusions in this area are determined. Volume of gas inclusion is determined through the ratio of the square of this inclusion to the square of the investigated area of the thin sections. By investigating a required number of informative areas in each thin section of the rock, and with the help of statistical processing of the data, we receive average value of total volume of gas inclusions in the rock sample in percent. By using the method of determining volume of gas inclusions in clastic grains of rocks, it is established that quartz grains of gas-bearing sandstones of the middle sub-stage of catagenesis (sandstone l₃¹Sl₅, A.G. Stakhanov Mine, Krasnoarmeyskiy district, Donetsk coal basin) contain on average 3,5 % of gas in closed micropores. This volume of gas is significant, considering that total porosity of this sandstone is 7 %. Thus, by using the proposed method, it is possible to determine additional volumes of gas containing in micropores of clastic grains of rocks. This is especially important during predicting the rock outburst hazard, since gas inclusions in clastic grains of rocks are under great pressure. With additional stress of the coal-bearing massif, they can act as an additional impulse of gas-dynamical phenomena.

Keywords:

gas inclusions, closed porosity, catagenesis, micropore, clastic grains.

References:

1. Antipovich, Ya.V. (2018), “Transformation of inclusions in quartz grains of sandstones”, Proceedings of mineralogical seminar “Modern problems of theoretical, experimental, and applied mineralogy”, Syktyvkar, Komi Republic, Russia, 22–24 May 2018, pp. 176-177.

2. Baranov, V.A. (2006), “Method and results of inclusion studying in clastic quartz of sandstones of Donbass”, Naukovyi visnyk Natsionalnohо hirnychoho universytetu,  no.11, pp. 43-47.

3. Tarantola, A., Diamond, L.W., Stünitz, H., Thus, A. and Pec, M. (2012), "Modification of fluid inclusions in quartz by deviatoric stress. Influence of principal stresses on inclusion density and orientation", Contributions to Mineralogy and Petrology, vol.164, no.3, pp. 537-550.

https://doi.org/10.1007/s00410-012-0749-1

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5. Baranov, V.A. (2012), “Laboratory of the study of structural changes in rocks - 7 years”, Geo-Technical Mechanics, no. 100, pp. 231-234.

About the author:

Antipovich Yana Valentinovna, Master of Science (M.Sc.), Junior Researcher, Institute of Geotechnical Mechanics named by N. Poljakov of National Academy of Sciences of Ukraine (IGTM, NASU), Dnepr, Ukraine, This email address is being protected from spambots. You need JavaScript enabled to view it. .

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