Journal of Geotechnology and Energy
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ISSN 2720-3581
Issue Date
2022
Volume
Vol. 39
Number
No. 1
Description
Journal Volume
Journal of Geotechnology and Energy
Vol. 39 (2022)
Projects
Pages
Articles
Drilling mud influence on sandstone poroelastic parameters
(AGH University of Science and Technology Press, 2022) Knez, Dariusz; Rajaoalison, Herimitsinjo; Nkunzi, Donatille
Perhaps the most critical challenge faced during drilling operations is related to the stability of the well. Additionally, drilling mud plays a crucial role in wellbore stability, as one of its main uses is to support the wellbore wall during the drilling operation. However, ignorance of the effects of drilling mud on the mechanical properties of rock formation can also lead to well failure. The stability of the wellbore is also influenced by pore pressure during the drilling process. The analysis of changes in rock poroelastic parameters after drilling mud saturation was found to be useful regarding the abovementioned issues. Therefore, the measurement of the dynamic Young's modulus, Poisson's ratio and Biot's coefficient of sandstone samples was carried out to determine their trends of variations with confining pressure in different conditions such as dry, water and drilling mud filtrate saturation. The findings indicate that both the dynamic Young's modulus and the Poisson's ratio of the sandstone rock increased after saturation with water and drilling mud filtrate, while the Biot's coefficient was reduced. Furthermore, the velocity of the P wave, the dynamic Young's modulus and the dynamic Poisson's ratio of the sandstone rock were proportional to the confining pressure, while the Biot's coefficient were inversely proportional to the confining pressure. The results imply that effective stress calculation can be influenced by changes in poroelastic parameters established from geophysical measurements, and risk management of wellbore stability stability was increased.
Thermoelectric properties of pyrite in the supra-ore level of gold mineralization (Ukrainian Carpathians)
(AGH University of Science and Technology Press, 2022) Kostûk, Oleksandr Volodimirovič
The thermoelectric properties of different-aged generations of pyrite from Lostun (Chyvchyny ore region) Tukalo and Kamin-Kliovka (Лостунь, Тукало, Камінь-Кльовка) (Rakhiv ore region) ore manifestations are investigated. The research included traditional geological observations with the collection of samples of various hosting ores, together with mineralogical analysis measuring their reflective power and the thermo electro-motive force of pyrite. Two pyrite generations (pyrite I and pyrite II) have been revealed by the investigation's results. The crystals belonging to the generations differ morphologically quite vividly (pyrite I has the form of a pentagonal dodecahedron, while pyrite II takes the form of a cube) and have different thermoelectrical properties. Pyrite I testifies to the fact that in the direction from the central parts of crystals with a pentagonal-dodecahedron tendency to its surface, the thermoelectrical properties essentially change. In particular, the central parts of pyrite I crystals have electron conductivity while its faces are mainly hole ones. Such essential changes of the pyrite thermoelectrical properties from the central parts of the crystals to their peripheral ones are probably mostly caused by quantitative changes of element admixtures in the crystalline lattice. However, the pyrite II thermoelectrical properties investigation results testify that this mineral has only hole-conductivity. Thus, in terms of general thermo-e.m.f. (electromagnetic field) as well as selections range, the thermoelectric properties of the pyrite from the Lostun and Tukalo ore manifestations and the Sauliak (Сауляк) auriferous deposit are similar. The comparative character of the pyrite thermoelectric properties from the investigated ore manifestations, the Sauliak deposit and other auriferous deposits testify to the supra-ore level of the gold mineralization in Tukalo and Lostun objects and make it possible to assume that erosion shear of the gold mineralization in Tukalo ore manifestation is similar to the Sauliak deposit erosive shear and is deeper in comparison to the Lostun ore manifestation.