Geology, Geophysics & Environment
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ISSN 2299-8004
e-ISSN: 2353-0790
Issue Date
2019
Volume
Vol. 45
Number
No 1
Description
Journal Volume
Geology, Geophysics & Environment
Vol. 45 (2019)
Projects
Pages
Articles
Attempts to calculate the pseudo-anisotropy of elastic parameters of shales gas formations based on well logging data and their geostatistical analysis
(Wydawnictwa AGH, 2019) Bała, Maria; Cichy, Adam; Wasilewska-Błaszczyk, Monika
This paper presents the attempts to calculate the pseudo-anisotropy of elastic parameters for the Silurian and Ordovician shale formations of several wells located in the Baltic basin. For this purpose, well-logging data were used, in particular data recorded with acoustic dipole tools. With the P and S waves velocities available, measured at the dipole setting in two orthogonal directions XX or YY (S$_{Fast}$ and S$_{Slow}$), the elastic $\varepsilon$ and $\gamma$ parameters were calculated. In this paper we evaluate the effect of different factors e.g., porosity, clay and kerogen content on the velocity of anisotropy shale gas formations. A geostatistical analysis of elastic and reservoir properties was carried out in order to determine the character of the variability of Silurian and Ordovician shale formations in all of the studied wells. Semivariograms for each well characterizing the variation of elastic parameters in the vertical direction were calculated.
The provenance of erratic pebbles from a till in the vicinity of the city of Radom, central Poland
(Wydawnictwa AGH, 2019) Strzelecki, Piotr Jan
Petrographic analysis, including the indicator erratics count method of coarse pebbles (20–60 mm), was performed for the first subsurface layer of the glacial till in the vicinity of the city of Radom. Crystalline rocks comprise 60% of the sample, whereas carbonate and clastic sedimentary rocks total 18% and 15%, respectively. Among the crystalline rocks, 14% clasts were identified as indicator erratics. The majority of the indictor erratics originated from the Åland region (63%). Significant contributions were also derived from the central Baltic Basin (12%), Ångermanland (9%) and Uppland (9%) regions. Trace amounts are recorded from the northern Baltic, Dalarna and Småland regions. The spatial distribution of crystalline erratic source areas suggests material incorporation into an ice sheet mainly from central-eastern Fennoscandia. The indicator assemblage composition indicates the Odranian (MIS 6) origin of the till. The majority of the erratic sedimentary rocks were derived from the central and southern Baltic Basin while local rocks comprise a minor proportion. The relatively low carbonate clasts content indicates that the till was affected by partial decalcification resulting from post-depositional chemical weathering. This study supplements the results on erratic pebble provenance in the glacial tills of Middle Polish Glaciation Complex in Poland.
Engineering geological evaluation of some rocks from Akure, Southwestern Nigeria as aggregates for concrete and pavement construction
(Wydawnictwa AGH, 2019) Ademila, Omowumi
The importance of rocks and rock aggregates cannot be overemphasized in construction and concrete design globally. This study evaluated the physical and mechanical characteristics of fine grained granite, porphyritic granite, quartzite, granite gneiss, migmatite gneiss and charnockite from ten different locations in Akure for their suitability as construction materials. Field observation, water absorption, specific gravity, shape indices, aggregate impact value (AIV), aggregate crushing value (ACV), Los Angeles abrasion value (LAAV), compressive strength, tensile strength and petrography of the selected rocks were evaluated. The field studies indicate fresh outcrops with little signs of weathering. Porphyritic granite shows a higher water absorption value >1%, suggestive of its unsuitability as foundation materials in water logged areas. The higher flakiness and elongation indices of porphyritic granite, quartzite and migmatite gneiss are detrimental to the higher workability and stability of mixes. AIV (14.79–23.52%), ACV (18.32–28.93%) and LAAV (25.22–34.55%) showed that granite, granite gneiss and charnockite have good soundness and hardness with greater resistance to wear. Higher strength values of all the rocks were found to be satisfactory for use in the production of aggregates for civil constructions. Petrographic analysis revealed similarities in the compositions of the rocks, with quartz being the dominant mineral. The results show that all the rock types possess the required quality standards for use as construction aggregates in highway pavements and foundations. Some of the aggregates (GG1, GG2, GF, GC, MG1, CK1 and CK2) are also suitable for bituminous mixes. Quartzite should be avoided in load bearing masonry units due to its lower strength values. The most suitable rocks proven as road and building stones are fine grained granite, granite gneiss and charnockite because of their low water absorption, low flakiness and elongation indices, low abrasion values, higher strength values (tensile strength and unconfined compressive strength) and sound petrographic characters. Thus, adequate knowledge of rocks and rock aggregates is crucial in order to prevent continuous structural failure around the globe and make the environment friendlier.
The contribution of geophysics to archaeology: a case study of an ancient canal of the Oc Eo culture in the Mekong Delta, Vietnam
(Wydawnictwa AGH, 2019) Lê, Ngọc Thành; Nguyễn, Quang Dũng; Nguyễn, Quang Bắc; Nguyễn, Quang Mien; Nguyễn, Dan Vu; Duong, Ba Man; Nguyễn, Dinh Chau
Generally, underground ancient canals are infilled with alluvial materials, with the canal bed and substrate often having different resistivity values. This study aimed to determine the location and morphology of Malleret’s ancient canal 16 located to the southeast of the Ba The mountain, Mekong Delta, Vietnam by means of geophysical techniques. Two geophysical methods were used: electromagnetic profile and electric resisitivity tomography. A geoelectric structure 70 m long with 70–95 mS/m of apparent conductivity was found. On the electrical resistivity tomography section, a resistivity zone of 10–20 $\Omega \cdot$ m, 1-4 m deep, 70 m wide corresponds to the mentioned above geoelectric structure, which is in an asymmetric U-shape extending toward the southeastern bank of canal 16. Hand-augering confirmed that the canal bed is fully incised into Holocene sediments as a substrate which stretches down to the Pleistocene. The sediments are composed of loams mixed with plant remains with a resistivity ρ ~ 10–15 $\Omega \cdot$ m. Both of the canal banks at a depth of 5 m are made up of Holocene sedi-ments ($\rho$ ~ 4–10 $\Omega \cdot$ m). The $^{14}$C measurements determined the age of the organic matter in the canal as being equal to 1210 $\pm$ 85 BP, suggesting canal 16 ceased being operational at that time. The precise positioning of canal 16 on the ground surface, as well as identifying the morphology of the canal bed, were corroborated by geophysical techniques. The obtained results are of considerable value to archaeologists.
Relations between present relief on the border of lowlands and highlands and geological structures of the Paleozoic Platform - a case study from central Poland
(Wydawnictwa AGH, 2019) Szmidt, Aleksander; Wachecka-Kotkowska, Lucyna
The article is an attempt to find relations between geology and the dynamics of the Mesozoic surface of the Łódź Synclinorium, the Radomsko Elevation and the Bełchatów Graben and the present relief on the border of the Polish Lowlands and Uplands in its central part. Fossil relief has been compared with the present one as related to the extent of the recession phases of the Saalian (Wartanian) ice-sheet. A significant convergence has been found between the Mesozoic surface plain and the main morphologic elements. The role of elevations and fossil valleys has been stressed as stable forms in the pre-Pleistocene and contemporary landscape. Also stressed has been the meaning of grabens and elevations enforcing longer stoppages of the Wartanian stadial of the Middle Polish Glaciations.