pdf № 364, April

DOI: 10.19110/geov.2025.4.1

The article observes publications devoted to postsedimentation carbonatization in terrigenous reservoir rocks. The widespread occurrence of this phenomenon in many hydrocarbon deposits and a significant decrease in porosity caused by filling the void space with carbonate cement constitute the relevance of the issue under study. The problems of formation of fluid-resistant rocks in the reservoir, which can influence the redistribution of fluid flows during the development of the deposit, are considered. It is noted that there is no generally accepted methodology for identifying and predicting the distribution of these intervals based on the interpretation of geophysical methods of well survey, as well as the impossibility of differentiation based on seismic data.

The problems of predicting the distribution of carbonatization are considered using the example of the studied field X in the Pur-Taz oil and gas region of Western Siberia, where the presence of carbonatization in the form of thin interlayers, solid intervals with varying degrees of cementation, and also in the form of nodules is noted. The facies association of carbonatization with the most sandy reservoirs of coastal-continental environments has been established. The effect of carbonation on filtration-capacitance properties is calculated. The absence of a relationship between the intensity of carbonatization and the proximity of discontinuous faults based on the materials of the deposit under consideration has been revealed. It is established that the carbonatized interlayers extend no more than the first tens of meters.

Using the example of other deposits, we focus on the need to consider for carbonatized intervals in petrophysical, geological, and hydrodynamic models. It is shown that the presence of carbonatization is a risk for fluid breakthrough both due to natural fracturing and after hydraulic fracturing. From this point of view, the study of carbonatized intervals and their distribution in the reservoir volume allow increasing the predictive capabilities of hydrodynamic models, taking into account filtration processes in a lithologically heterogeneous reservoir.

Keywords: carbonatization, diagenesis, diagenetic transformations, concretions, fracturing, cenomanian sediments, lithological and facies analysis

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DOI: 10.19110/geov.2025.4.2

The article presents the results of micropaleontological studies (palynological and diatom analyses), which are traditional in a comprehensive study of geosystems. A coastal outcrop in the estuary area of the Chernaya River was studied. The boulder loam exposed at the base of the section with a visible thickness of about 10 m is correlated with the Polar (Ostashkov) horizon, which is confirmed by the results of OSL dating. The overlying sediments have diagnostic features of flow-till. The results of palynological study of clay sediments in the roof of the section indicate the existence of a small proglacial lake formed during the degradation of Polar glaciation. Later, the reservoir underwent swamping and transformation into a permafrost hummocky peat massif. Peat formation began in the Early Holocene. The process of peat accumulation is dated at 7180±150 14C BP (IGAN 10839) and 5720±100 14C BP (IGAN 10838), respectively. The studied glacial and lake-bog sediments were part of a supraglacial sedimentary complex, the fabric of which included both freshwater proglacial reservoirs and brackish-water basins formed during ingression. At the same time, some different types of lakes were probably isolated from each other by dead ice or ridges of loose rocks, subsequently preserved or destroyed by erosional alluvial processes.

Keywords: southeast of the Barents Sea region, Late Glacial and Holocene, palynology, diatoms

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DOI: 10.19110/geov.2025.4.3

The study of the halogen (F and Cl) and sulfur contents in apatite from granodiorites and leucogranites of the Tigertysh complex (gЄ-O₁t) was carried out, which may indicate the potential ore content of granitoids. Apatites of granodiorites are confined mainly to amphibole grains, less often located in quartz and feldspars, and correspond in composition to fluorapatite (F = 2.45—2.76 wt. %, Cl = 0.02—0.03 wt. %). In leucogranites, apatite is confined to feldspars and biotite, and corresponds in composition to hydroxyl- and fluorapatite (F = 1.50—1.80 wt. %, Cl = 0.33—0.52 wt. %). In apatite from granodiorites, the sulfur content is maximum in grains confined to amphibole and is 0.05–0.11 wt. %, while in apatite from quartz and feldspars it is no more than 0.04 wt. %. The sulfur content in apatite from leucogranites does not depend on its confinement to different minerals and is 0.04—0.07 wt. %. Based on the F, Cl и S contents in apatites of granitoids of the Tigertysh complex, it can be assumed that gold-sulfide-quartz mineralization may be associated with granodiorites, and Cu-porphyry mineralization with leucogranites.

Keywords: apatite, halogens, sulfur, granitoids, metallogeny, Kuznetsk Alatau

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DOI: 10.19110/geov.202.4.4

The archaeomineralogical studies of items made of non-ferrous and precious metals in burials No. 59 and 115 of the Kokpomyag burial ground allowed us to identify, along with imported jewelry made of high-grade silver, repaired items based on a tin-silver alloy. In burial No. 86 of the Kokpomyag burial ground, considered in this artice, not only high-gade siver items, but also silver balls were found that could have been used as raw material for the manufacture of silver items, which is confirmed by the finds of fragments of silver jewelry made with simple technology. The burial inventory allows assuming that the burial belonged to a master craftsman, who mastered simple silversmithing skills and occupied a high social status in society.

Keywords: archeology, mineralogy, Kokpomyag burial ground, burial No. 86, silver, coppe, bronze iron objects

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DOI: 10.19110/geov.2025.4.5

When closing a finite linear ornament into a ring, translation along a straight line turns into rotation around a finite-order symmetry axis. A natural analogy between the symmetry groups of crystallographic borders and Curie’s limit symmetry groups with one ∞ axis arises on an endless ring. But the former are seven and the latter are five. Another two are isolated in the paper from the limit groups ∞/m of rotating and ∞/mm of common cylinders. Thereby a mutually unambiguous correspondence has been achieved. The example is recommended for consideration in the university course of crystallography on the topics «Symmetry groups of borders» and «Curie’s limit groups».

Keywords: symmetry groups of borders, Curie’s limit groups

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