Criteria for local forecast of reservoir formations in carbonate Vendian-Cambrian deposits of the Ust-Kutskian horizon

The article presents a lithogenetic typification of the rocks of the Ust-Kutskian horizon of the Teterian formation in the central part of the Nepa-Botuobin anteclise. A generalized scheme-model of their formation is drawn up. Granular dolomites have been identified as the most promising lithogenetic type to allocate zones with improved reservoir properties. The structure of the void space of the Ust-Kutskian horizon is characterized. Based on the quantitative assessment of pores and caverns, the presence of salts in them, a correlation was established between these parameters and the reservoir properties of the rocks. The connection with post-sedimentation processes is shown. The conditions for the formation of the Ust-Kutskian depositsare reconstructed with the use of geochemical indicators for element-impurities. As a result of the studies, a set of criteria for local forecasting of reservoirs for setting up the first stage of exploration and development has been developed

Ancient Aeolian Reservoirs of the East Siberia Craton

Fine-grained strata deposited on the Eastern Siberian craton are predominantly considered to mainly consist of Neoproterozoic sandstones. Clastic rocks near the unconformity border of the Ediacaran and the Riphean are represented by sandstone and siltstone layers with thicknesses of several tens of meters, belonging to the Nepa, Tira, and Byuk horizons in the Nepa–Botuoba region. These Neoproterozoic sandstones have features characteristic of aeolianites formed under the action of high wind velocity in the Ediacaran period. Sandstone samples near the Riphean–Ediacaran boundary were collected from five deep wells and characterized for granulometry and mineral composition using optical microscopy, XRD, SEM, and ICP-MS techniques. These sandstones have a high proportion of quartz (60–98%) with minor amounts of feldspars, carbonate, and sulfate cements. Thin sections of the sandy rocks feature bimodal distributions of the grains throughout many sections, with large well-rounded quartz grains being several orders of magnitude greater than the silt matrix grains. The monomineralic quartz rocks have an overgrowth of quartz grains. These rocks can be petroleum reservoirs with good porosity and permeability, but in most of the studied intervals, a high content of anhydrite and dolomite interstitial cement significantly reduces both. The porosity of the rocks is low, while the permeability is very low, which may be associated with a significant amount of clay and cement material. Aeolianites normally contain large amounts of bimodal quartz (due to its high stability and resistance to weathering) and possess the presence of heavy minerals

Roasting-leaching experiments on glauconitic rocks of Bakchar ironstone deposit (Western Siberia) for evaluation their fertilizer potential

This study examines factors favouring optimal release of potassium from a glauconitic rock by moderate roasting-leaching. Sieving and electromagnetic separation of oolitic iron ore deposit increases the concentration of glauconite grains substantially. Roasting and chemical leaching of this concentrate enhances the release of potassium as interlayer structures of glauconite collapses. This study records the percentage of potassium recovered from glauconite under different experimental conditions, viz., temperature, reaction time, concentration as well as volume of HCl and stages involved in the leaching treatment. Leaching of glauconite without roasting results a low recovery ( < 15%) of K at room temperature. The recovery of K content from the sample increases markedly with increase in concentration of HCl, leaching time, and the ratio by mass of sample to HCl, and marginally with increased stages of leaching. Roasting at 900 degrees C recovers maximum K up to 62-63% for one-stage leaching treatment at 100 degrees C for 120 min with a 4 mol.l(-1) HCl solution for a sample: HCl ratio of 1:5. The roasting-leaching method, therefore, holds promise for converting glauconite to potash salts for agronomic applications

Mineral-geochemical features of the minor river sediments in the interfluve area of the Lo and Kau rivers (Northern Vietnam)

Relevance. Investigations of mineral and chemical composition of river sediments have great meaning in development and improvement of techniques of hydrogeochemical study of minerals and decisions of tasks for normalization of anthropogenous influence on surface and ground water objects. The aim of the research is to estimate mineral and chemical composition in river bottom sediments of the area between the Lo and Kau rivers (Northern Vietnam) as causes and effects of formation of geochemical anomalies in water objects. Methods of the research: mathematical modelling, landscape-geochemical and statistical methods, methods of definition of chemical and mineral composition of river bottom sediments. Results and conclusions. The data on mineral and chemical composition of the Ban Thi, Dai rivers and their tributaries sediments were obtained. The authors have analyzed the interrelations between mineral and chemical composition of river bottom sediments, water extracts from them and river waters. It is shown that concentrations of some chemical elements find the direct ratio to the contents of chlorite and in inverse proportion to the contents of quartz. It is ascertained that carbonate barrier plays the important role in regulation of chemical composition of river waters in the affected area of mining plants associated with the extraction of lead-zinc ores. The authors obtained the approximate estimations of hard sediment particles transport distance (up to 34 km at rain period) and the average time of approximation to saturation of river waters relative to calcite (approximately 9,4 h). The conclusion on the key role of geochemical barriers in formation of geoecological conditions of ore extractions, including decrease of zinc, lead and some other elements concentration in river waters and sediments on the distance up to 10-11 km is proved

The nature, origin and significance of luminescent layers in the Bazhenov Shale Formation of West Siberia, Russia

Argillites that strongly luminesce under UV radiation were detected in the Bazhenov Shale Formation (BSF) of the West Siberian Basin during routine core examination and found to be persistent over a wide lateral area. The mineralogy and fabric of these luminescent layers were characterized by optical and fluorescence microscopy, SEM, TEM, XRD and IR methods. Optical and fluorescence microscopy showed that the luminescent layers were to a large extent derived from volcanic ash falls and could be described as meta-tuffites, although normal detrital sedimentation continued at the same time. The layers have a thickness of several mm to a maximum of 3–4 cm and can be defined as a clay-rich regional horizons extending for over 500 km. XRD showed that two principal clay minerals were predominant, namely a kaolinite group minerals, (kaolinite-rich) and a mixed-layer illite-smectite (I/S) similar to that found in K-bentonite. Total organic matter in the luminescent layers is much lower than that in the enclosing BSF clayey-silty siliceous sediments above and below as shown by pyrolytic analyses. Evidence is presented that the luminescent characteristic of the argillites is related to their clay mineralogy, specifically to their content of kaolin minerals, although a contribution from nitrogenous organic matter cannot be entirely discounted. In some ways the luminescent argillites can be compared with bentonites associated with ash transformations or with tonsteins in coal beds, which are also derived from volcanic ash falls and contain highly crystalline kaolinite. However, tonsteins originate at or near land surface whereas the argillites were apparently formed in the deep ocean. But just as tonsteins can be used for detailed stratigraphic studies and are valuable in the context of coal exploration, so may the luminescent argillites prove to be significant both stratigraphically and in the search for economic hydrocarbon deposits, bearing in mind that their clay mineralogy may be sensitive to temperature and depth of burial and related to their placement in the oil and gas window

Mineral-geochemical features of the minor river sediments in the interfluve area of the Lo and Kau rivers (Northern Vietnam)

Актуальность работы. Исследования минерального и химического состава донных отложений имеют важное значение в разработке и усовершенствовании методик гидрогеохимических поисков полезных ископаемых и решения задач нормирования антропогенного воздействия на поверхностные и подземные водные объекты. Цель работы: оценка минерального и химического состава речных отложений в междуречье рек Ло и Кау (север Вьетнама) как причины и следствия процессов формирования геохимических аномалий в водных объектах. Методы исследования: математическое моделирование, ландшафтно-геохимический и статистические методы, методы определения химического и минерального состава донных отложений. Результаты и выводы. Получены данные о минеральном и химическом составе донных отложений рек Бан Тхи и Дай (Северный Вьетнам, провинция Баккан) в меженный период 2016 г. Выполнен анализ взаимосвязей между минеральным и химическим составом донных отложений водотоков, водных вытяжек из них и речных вод. Показано, что концентрации целого ряда химических элементов прямо пропорциональны содержанию хлоритов и обратно пропорционально содержанию кварца. Установлено, что карбонатный барьер играет важную роль в регуляции химического состава речных вод в зоне влияния горнодобывающих предприятий, связанных с добычей свинцово-цинковых руд. Получены ориентировочные оценки расстояния переноса твёрдых частиц (до 34 км в период дождей) и среднего времени приближения к насыщению речных вод относительно кальцита (примерно 9,4 часа). Обоснован вывод о ключевой роли геохимических барьеров в формировании геоэкологических условий разработки месторождений твёрдых полезных ископаемых, в том числе снижении концентраций цинка, свинца и ряда других элементов в речных водах и донных отложениях на участках до 10-11 км.Relevance. Investigations of mineral and chemical composition of river sediments have great meaning in development and improvement of techniques of hydrogeochemical study of minerals and decisions of tasks for normalization of anthropogenous influence on surface and ground water objects. The aim of the research is to estimate mineral and chemical composition in river bottom sediments of the area between the Lo and Kau rivers (Northern Vietnam) as causes and effects of formation of geochemical anomalies in water objects. Methods of the research: mathematical modelling, landscape-geochemical and statistical methods, methods of definition of chemical and mineral composition of river bottom sediments. Results and conclusions. The data on mineral and chemical composition of the Ban Thi, Dai rivers and their tributaries sediments were obtained. The authors have analyzed the interrelations between mineral and chemical composition of river bottom sediments, water extracts from them and river waters. It is shown that concentrations of some chemical elements find the direct ratio to the contents of chlorite and in inverse proportion to the contents of quartz. It is ascertained that carbonate barrier plays the important role in regulation of chemical composition of river waters in the affected area of mining plants associated with the extraction of lead-zinc ores. The authors obtained the approximate estimations of hard sediment particles transport distance (up to 34 km at rain period) and the average time of approximation to saturation of river waters relative to calcite (approximately 9,4 h). The conclusion on the key role of geochemical barriers in formation of geoecological conditions of ore extractions, including decrease of zinc, lead and some other elements concentration in river waters and sediments on the distance up to 10-11 km is proved