No 4 (2025)

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.

The study of the halogen (F and Cl) and sulfur contents in apatite from granodiorites and leucogranites of the Tigertysh complex (Є-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 and 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.

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».

April 1 marked the 95th anniversary of the birth of the outstanding geologist, specialist in the field of mineralogy of piezo-optical and gemstone raw material deposits, honorary member of the Russian Society of Gemologists, Candidate of geological and mineralogical sciences, Vladimir Valentinovich Bukanov. V. V. Bukanov worked at the Institute of Geology of the Komi branch of the USSR Academy of Sciences from 1963 to 1973, heading the Laboratory of Minera­logy and Panning. He was one of the first to organize large-scale mineralogical research at the institute on a modern, advanced theoretical basis (ontogeny of minerals) using modern techniques and research methods. He was awarded the badges «Excellent Exploration» and «Honorary Subsoil Prospector». Author of more than 100 scientific and popular works.