Potential Gas Research Articles

PROSPECTS FOR OIL AND GAS POTENTIAL OF THE MIOCENE-PLIOCENE AND MESOZOIC DEPOSITS OF THE ABSHERON ARCHIPELAGO

The article is devoted to the prospects of oil and gas potential of the Miocene-Pliocene and Mesozoic deposits of the Absheron archipelago. The geological information about the Absheron archipelago dates back to the middle of the 19th century, the century of the industrial revolution. The offshore area of the Absheron archipelago, located to the east of the Absheron peninsula, is abundant with islands, surface and underwater hidden rocks, ridges, ledges and sand banks. The largest islands of the archipelago Pirallahi and Chilov are located here. They are confined to the anticlinal folds of the same name and their formation is associated with large thrusts of the SW limbs of these structures. The North Absheron oil and gas zone, located in the northern part of the Absheron archipelago, covers a vast territory stretching from the northwest to the southeast and is the southern end of the Scythian-Turanian Epi-Hercynian platform. An interesting feature from the point of view of the geology of the North Absheron tectonic zone is a peculiar tectonic structure, lithofacies features and oil and gas potential. Local uplifts differ from other uplifts located in the fold zone by their indeterminate location (Fig. 1). Despite the geological and geophysical work and the drilling of numerous prospecting wells, the Miocene-Pliocene deposits of the study area have not been sufficiently studied in terms of their oil and gas potential. Drilling of numerous wells in the Miocene-Pliocene deposits did not completely open the section of these deposits. The drilling of oil and gas bearing formations with full penetration and development is mainly associated with the optimal conduct of drilling operations. The anticlinal zone begins with structure bank Absheron. In connection with the washout on the structure bank Absheron, the upper section of the Productive series (PS) comes out on the day surface, and the lower section of the PS, with the exception of Gala suite, participates in all stratigraphic units. The Gala suite was found on the southwestern limb of the structure. Recently, hydrocarbon accumulations have been identified by prospecting and exploration work on the structures of Novkhany, Ashrafi, Garabagh. From this point of view, the correct assessment of hydrocarbon accumulations in the Miocene-Pliocene deposits in the North Absheron tectonic zone is considered the main one and complements the understanding of the oil and gas potential of the study area. Keywords: Absheron archipelago, Mesozoic complex, Pliocene deposits, Caspian Sea, prospecting and exploration, tectonic zone.

Prospect Evaluation of the Cretaceous Yageliemu Clastic Reservoir Based on Geophysical Log Data: A Case Study from the Yakela Gas Condensate Field, Tarim Basin, China

This paper evaluated the oil and gas potential of the Cretaceous Yageliemu clastic reservoir within the Yakela condensed gas field lying in the Kuqa Depression, Tarim Basin, China. The petrophysical properties of the interest zones in the Kuqa area were characterized using geophysical logs from five wells. The results reveal that the gas-bearing zones are characterized by high resistivity, good permeability (K) and effective porosity (Φeff), low water saturation (Sw), and low shale concentration (Vsh), reflecting clean sand. The shale distribution model showed that these shales have no major influence on porosity and fluid saturation. The average shale volume, average effective porosity, and hydrocarbon saturation indicate that the Cretaceous Yageliemu Formation in the studied area contains prospective reservoir properties. The spatial distribution of petrophysical parameters, reservoir rock typing (RRT), and lithofacies were analyzed using the cross plots of litho saturation (volumetric analysis), iso-parametric representations of the petrophysical characteristics, cluster analysis, and self-organizing feature maps, respectively. The southeastern and northeastern regions of the research area should be ignored because of their high water and shale concentrations. The sediments in the southwest and northwest include the most potential reservoir intervals that should be considered for the future exploration and development of oil and gas fields in the study area.

Petroleum potential of Achimov deposits in the north of Western Siberia

Western Siberia has oil and gas potential that is very important for the development of the oil and gas industry in Russia. The north of Western Siberia has special significance for the industry, that's where the maximum aggregate deposit of hydrocarbon reserves is located in fields, such as Urengoy, Yamburgskoye and Medvezhye. Over the last decade, a tendency to reduce the efficiency of geological exploration has appeared, therefore, it is necessary to conduct a comprehensive analysis of the actual material and to select priority areas. The Lower Cretaceous complex of the Cretaceous oil and gas megalithic complex located in the north of Western Siberia is the most lucrative. The Neocomian clinoform Achimov deposits of this complex are the main object of study. Achimov deposits are trapped almost throughout the Nadym-Pur interfluve area and are having a complex structure. The formation of Achimov rocks mostly took place in the deep-water part of the paleosea that affected their heterogeneity. An analysis of the geological and field parameters of the Achimov deposits determined the maximum aggregate of hydrocarbon deposits in the eastern and northern parts of the study area, as well as zones of active rifting. Geological exploration should be carried out in such zones initially.

Detailed Geoseismic Structure of the Riphean Deposits in Buolkalakh–Lena Area Based on Deep Drilling and Seismic Exploration Data

Abstract —The work considered an integrated approach to the study of deep-lying Riphean strata of the Buolkalakh–Lena region, which have certain prospects in terms of oil and gas potential. The method of revision and synthesis of acoustic and density logs is described in detail using the example of wells drilled in 80–90 for the purpose of correct reference to seismic sections. It has been shown that the Khaipakh, Debengdin, Arymas, Kyutingdinsky, and Sygynakhtakh formations of the Early and Middle Riphean eras overlook the pre-Permian surface in the middle part of the Lena–Anabar trough. The region also developed older Riphean deposits that are not exposed on the Olenek uplift and are not studied by deep drilling. The prospects for the oil and gas content of Riphean strata in the region are mainly associated with carbonate reservoirs formed in the top of the Riphean sequence and cropping out on the pre-Permian erosive surface, the most promising rocks are those constituting large carbonate platforms that were partially eroded and subjected to processes of hypergenesis and karst formation.

Shallow burial shale gas accumulation pattern of the Wufeng–Longmaxi Formations in the northern Guizhou area, western Yangtze platform

Although continuous breakthroughs of economic shale gas exploitation have been made globally within the middle–deep buried depth (∼1500–3500 m), the shallow–buried (less than 1500 m) shales are also widely distributed, showing excellent exploration prospects. However, the shale gas accumulation (SGA) pattern of the shallow burial shale remains unknown, limiting future shale gas exploration. To investigate the SGA pattern and the exploration potential of shale gas in shallow–buried shales, experiments such as X–Ray Diffractometer, N2 and CO2 adsorption, Focused Ion Beam Scanning Electron Microscopy (FIB-SEM), total organic carbon (TOC) content, gas chromatography–mass spectrometry, and field gas content test were carried out based on three wells penetrated the Wufeng–Longmaxi Formation with the buried depths of less than 700 m in the Northern Guizhou area, western Yangtze Platform. The geochemical and mineral records indicate that the organic matter is enriched as a result of global climate and regional tectonic activity, indicating the sufficient gas generation potential. The results of low pressure N2 and CO2 adsorption, as well as images of the FIB–SEM show that the mesopores are controlled by the organic matter, and the micropores, which are associated with minerals (primarily clays), can provide much more specific surface area and pore space in shallow–buried shales. Furthermore, carbonates with low porosity and permeability from the Songkan, Jiancaogou and Baota Formations, and the shale interval with low TOC values, weak brittleness, and low porosity, can serve as good roofs and floors for the SGA. Despite the fact that multi–stage tectonic movements resulted in the formation of faults and fractures, the good preservation, adequate gas storage space, and sufficient hydrocarbon generation potential contribute to the SGA in the shallow–buried shale.

Geological characteristics and exploration potential of the coal measure gas from Shan 2 of the Shanxi formation in the eastern Ordos Basin

“Coal measure gas,” excluding tight (low-permeability) sandstone gas, refers in this study to the self-sourcing unconventional natural gas stored in coal, shale, and fine siltstone. It is characterized by various types of occurrences and reservoirs, a distinct cyclic succession of coal measure strata, widely distributed mosaic hydrocarbon accumulations, three types of coal measure gas accumulations, and configurations of vertically multiple-stacked gas-bearing reservoirs. Coal measure gas from Shan 2 can be divided—according to the grain size of sandstone, configurations of sandstone–coal–mudstone association, thickness, and layers—into four types: thick massive sandstone–coal–mudstone (type I), fine siltstone–coal–mudstone (type II), thin sandstone–mudstone–sandstone (type III), and coal–mudstone (type IV). Comprehensive evaluation suggests that the coal measure gas in the Suide-Mizhi area of the southern Ordos Basin presents an important and favorable accumulation option, characterized by coalbed methane, shale gas, and tight gas stored in sandstone–mudstone–coal strata. Therefore, it is essential to conduct full future assessments for the coal beds, shale, and tight gas controlling exploration for the “vertical gas-bearing zone” by three-dimensional exploration.

Gas Kinetics, Rumen Characteristics, and In Vitro Degradability of Varied Levels of Dried and Fresh Cassava Leaf Top Fermented with Cassava Pulp

The purpose of this study was to determine the impact of different levels of dried cassava leaf top (DCT) and fresh cassava leaf top (FCT) fermented with cassava pulp (CS) on the nutritional value of silage, gas kinetics, rumen characteristics, and in vitro degradability. Dietary treatments were administered using a completely randomized design (CRD) with eight treatments and three replicate runs. The eight treatments were as follows: 1) CS fermented no additive (nA), 2) CS fermented with additives ( Saccharomyces cerevisiae , urea, molasses, and sugar) (CSA), 3) 95% CSA fermented with 5% DCT (5DCT), 4) 90% CSA fermented with 10% DCT (10DCT), 5) 85% CSA fermented with 15% DCT (15DCT), 6) 95% CSA fermented with 5% FCT (5FCT), 7) 90% CSA fermented with 10% FCT (10FCT), 8) 85% CSA fermented with 15% FCT (15FCT), respectively. After 21 days of fermentation, samples of the silages were taken for chemical analysis and utilized to examine the in vitro gas production and degradability. The results show that fermented CS with DCT at 5% to 10% DM had the highest increase in CP when compared to nA or CSA (p<0.05). In vitro dry matter disappearance (IVDMD) was significantly higher in CS fermented with 5% to 10% DCT (p<0.01), whereas CS fermented with FCT levels demonstrated lower IVDMD than the control group (p<0.01). The gas potential extent of gas production (p) and gas production from the insoluble fraction (b) did not differ significantly across treatments (p>0.05). However, the gas production from the immediately soluble fraction (a) was maximum when CS was fermented with 15DCT (p<0.05). Different treatments significantly affected the pH of the fermentation solution with the addition of 10DCT and 15DCT for 12 and 24 hours of incubation, respectively (p<0.01). After 12 hours of incubation, the population of protozoa was lowest when 5DCT and 10DCT were evaluated (p<0.01). In conclusion, CS fermented with DCT at a concentration of 5% to 10% can increase crude protein content, in vitro dry matter disappearance (IVDMD), and gas production from the immediately soluble fraction while decreasing the protozoa population.

The effects of Jurassic igneous intrusions on the generation and retention of gas shale in the Lower Permian source-reservoir shales of Karoo Basin, South Africa

Shale gas potential of the Whitehill Formation (Permian), Karoo Basin, South Africa is strongly influenced by widespread Jurassic igneous intrusions. A high-resolution organic petrographic and geochemical study is reported here on two stratigraphic sections, the objective being to gain insights into the chemical structure and alteration of oil-prone sedimentary organic matter during contact metamorphism. One section unaffected by intrusion served as background, while the other section was intruded by two laterally continuous dolerite sills with an average thickness of 10.7 and 9.3 m, preferentially emplaced at the upper and lower contacts of the formation, respectively. Heat flow from the sills caused TOC and S2 values from programmed pyrolysis to decline over a distance of 8.7 m from 3.2 to 0.15% and 4.65 to 0.11 mg HC/g TOC, respectively, and cause the reflectance of vitrinite and solid bitumen to increase from 2.03 to 5.82% and 1.58 to 7.87%.Organic matter in the background samples is dominated by solid bitumen, a secondary thermal conversion product of oil-generative Type II kerogen. In the sill-hosting section, the thermal aureoles can be recognized by systematic changes to the optical texture and chemical structure and composition of solid bitumen. Solid bitumen particles develop anisotropy approaching the sills and become transformed into coke and pyrolytic carbon. δ13Corg values become less negative by up to 3.13‰ VPDB. These data suggest significant devolatilization of organic matter to methane and destruction of petroleum generation and retention potential in the contact aureole of the sills. The trend of these datasets, coupled with the presence of several sills and their laterally extensive nature throughout much of the study area suggests that the intrusions have been significant in increasing methane generation on a basinal scale. Together, this study indicates that the complementary application of combined light and electron microscopy (CLEM), programmed pyrolysis, and isotope ratio mass spectrometry (IRMS) is suitable for a comprehensive characterization of organic matter alteration through the maturation continuum. Results also show that contact metamorphic alteration of organic matter by intrusions produced structural and compositional changes that are distinctive from those expected from geological burial maturation where graphite is the end-product.

Ophthalmic Manifestations of Chlorine Gas Exposure: What Do We Know So Far?

Chlorine gas is a hazardous substance that can cause severe health effects when inhaled or exposed to the skin. It is an odorless, colorless gas in many industrial and manufacturing settings and conflict areas. While exposure to chlorine gas is generally limited to the workplace and public areas, there are instances in which people may be exposed to high levels of chlorine gas for a short period of time due to spills, mishaps on the road or railroads, or other tragedies. In addition to the general health effects of chlorine gas, this essay will focus on the effects of chlorine gas on the eyes. The eyes are particularly sensitive to chlorine gas, and exposure can cause various symptoms, ranging from mild irritation to severe damage. Symptoms of chlorine gas exposure to the eyes include redness, burning, tearing, and blurred vision. In more serious cases, exposure to chlorine gas can cause permanent damage to the eyes, including corneal ulcers, scarring, and blindness. It is important to be aware of the signs and symptoms of chlorine gas exposure and the potential long-term effects to take the necessary steps to protect oneself. In addition to the potential health effects, it is important to understand the properties of chlorine gas. Chlorine gas is heavier than air and tends to settle in low-lying areas. It is highly reactive and can react with other substances to form hazardous compounds. As such, it is important to be aware of the potential for chlorine gas to react with other environmental substances and accumulate in certain areas. Finally, it is important to understand the background of chlorine gas use in various conflict areas. Chlorine gas has been used as a chemical weapon for centuries, and its use in modern warfare has been documented in various conflicts. As such, it is important to be aware of the potential for chlorine gas to be used in war zones and to take the necessary precautions to protect oneself. In conclusion, chlorine gas is a hazardous substance that can cause severe health effects when inhaled or exposed to the skin. The eyes are particularly sensitive to chlorine gas, and exposure can cause various symptoms, ranging from mild irritation to severe damage. It is important to be aware of the signs and symptoms of chlorine gas exposure and the potential long-term effects to take the necessary steps to protect oneself. Additionally, it is important to understand chlorine gas's properties and its background use in various conflict areas.

Depositional Environment and Organic Matter Enrichment in the Lower Paleozoic Shale from the Northeastern Margin of the Yangtze Platform, South China

In this study, twenty-six core shale samples were collected from the marine Lower Paleozoic shale in a well in the northeastern margin of the Yangtze Platform. Analyses of TOC content, mineral composition, major elements, along with trace and rare earth elements were conducted on the samples. The results were used to investigate the depositional conditions and their effects on organic matter accumulation and preservation. Generally, the sedimentation period of Niutitang Formation shale was in a cold and arid climate with anoxic marine environments, while the shale from Wufeng-Longmaxi Formation was formed in a warm and humid climate with oxic marine environments. In addition, the Wufeng-Longmaxi and Niutitang formations are characterized by low paleo-productivity. The organic matter enrichment for shale in this study could be simultaneously controlled by paleo-redox state and paleo-productivity. Organic matter enrichment of the Niutitang shale is mainly driven by preservation rather than productivity, while the dominant driving factor is the opposite for the Wufeng-Longmaxi shale. Additionally, palaeoclimate and terrestrial influx intensity were found to significantly impact the organic matter enrichment in the Wufeng-Longmaxi shale. The findings have implications for the understanding of the sedimentary processes, organic matter enrichment and preservation and shale gas potential of the study area.

Preliminary results of the solid-state C-13 NMR study of Mongolian coals: Implications for oil and gas potential and liquefaction reactivity

Chemical structures of five coals from Mongolia were studied using solid-state C-13 NMR and oil and gas potential as well as yields of liquefaction products of the coals have been predicted. Pennsylvanian ZG, Upper Permian TT and Lower-Middle Jurassic AT-5 coals might have more potential for gas due to abundant aliphatic and aromatic CH3 carbons. Lower-Middle Jurassic KH coal probably has more potential for oil because of its increased CH2 content. Lower Cretaceous SO-3 coal may have more potential for gas, but significant amount of non-hydrocarbon gases could also be generated simultaneously. The prediction of yields of liquefaction product shows that ZG, TT and AT-5 and KH coals could yield similar hydrocarbon gas, oil and residue. Cretaceous SO-3 coal is predicted to give the lowest yields of oil, hydrocarbon gas and residue compared with others. KH sample has the highest oil yield due to its high content of CH2.&#x0D; Keywords: coal, petroleum potential, NMR, Mongolia

Characteristics of In Situ Desorption Gas and their Relations to Shale Components: A Case Study of the Wufeng-Longmaxi Shales in Eastern Sichuan Basin, China

AbstractIn situ desorption gas measurement can be used to evaluate shale gas potential, sweet spot prediction, and production strategy optimization. However, gas contents and carbon isotope compositions of in situ desorption gas and the relationship to reservoir properties and shale compositions are not systematically studied from the actual production situation. In this study, 63 core shales of Wufeng-Longmaxi formation from the YY1 well in the eastern Sichuan Basin were subjected to TOC (total organic carbon), solid bitumen reflectance (Rb), maceral fractions of kerogen analysis, and X-ray diffraction (XRD) analysis to obtain shale compositions, and 10 selected samples were conducted on low-pressure N2/CO2 (N2/CO2GA), mercury injection capillary pressure (MICP), and field emission scanning electron microscopy (FE-SEM) tests to acquire reservoir properties. Meanwhile, 60 samples were also subjected to in situ desorption tests to obtain shale gas content, and 5 selected samples were used to investigate variations in shale gas compositions and carbon isotopes during the desorption process. Results indicated that transient rates of shale gas during desorption process are significantly controlled by desorption time and temperature. In terms of in situ desorption process, total gas is divided into desorbed gas and lost gas. Desorbed gas is mainly comprised of CH4, N2, CO2, and C2H6, with desorption priorities of N2 &amp;gt; CH4 &amp;gt; CO2 ≈ C2H6, which are consistent with their adsorption capacities. The δ13CH4 values tend to become heavier during desorption process, varying from -37.7‰ to -16.5‰, with a maximum increase amplitude of 18.8‰, whereas the change of δ13C2H6 value, from -38.2‰ to -34.8‰, is minor. Desorbed gas shows carbon isotope reversals, due to that preferential desorption of 12C-CH4 during desorption process results in δ13C value less negative in CH4. The tested desorbed gas, lost gas, and total gas ranged 0.088 to 1.63 cm3/g, 0.15 to 3.64 cm3/g, and 0.23 to 5.20 cm3/g, respectively. Shale gas content, i.e., desorbed gas and lost gas, is controlled primarily by TOC content and organic matter (OM)-hosted nanometer-size pores. Clay mineral content is negatively correlated with shale gas content, due to that, clay mineral pores are more easily compacted during burial and occupied by water molecules. Compared with shale gas reservoirs in North America, the studied shale reservoir has high brittle mineral content and permeability, which is considered to have great potential of shale gas resource and to be the next commercial development zone in south China.

An Insight into Post-Consumer Food Waste Characteristics as the Key to an Organic Recycling Method Selection in a Circular Economy

Reducing the phenomenon of food waste and effective management of already wasted food in the form of post-consumer waste, included in the source-separated organic fraction of municipal solid waste (SS-OFMSW) from households and catering facilities, are some of the key challenges of the circular economy (CE), in particular in highly urbanized areas. The basis for the effective use of this waste is the knowledge of its physical and chemical properties. The main objective of the paper is to identify the key technological and organizational parameters for selective collection determining the characteristics of the SS-OFMSW and, consequently, the optimal path for its management. This paper presents the results of qualitative research of SS-OFMSW generated in the capital of Poland—Warsaw—coming from three sources: multi- and single-family housing and catering facilities. The collection efficiency of this waste was determined in the form of quality in container rate (QCR = 92–97%) and variability in terms of impurities and admixtures present in it (CV = 56–87%). High variability indicates that the system of selective waste collection in Warsaw is immature, which may hinder undertaking activities in the field of waste management planning. The study confirmed the suitability of the tested SS-OFMSW for organic recycling, especially using anaerobic digestion (AD), to which it is predisposed by water content, C/N, and biomethane potential (BMP). All tested food waste is characterized by a high yield of biogas in the range of 384–426 m3/Mg VS and an average share of methane in biogas at the level of 52–61%. Fertilizer properties, moisture, and its gas potential show little variability (CV ≤ 16%), which means that these data can be treated as stable data. The obtained results indicate the optimal direction for the collection and processing of SS-OFMSW based on post-consumer food waste in urbanized areas.

Physical Chemistry in Context: Using Quantum Mechanics to Understand the Greenhouse Effect

The concepts taught in an undergraduate physical chemistry course are directly related to the molecular processes governing climate change, yet the connections between quantum mechanical molecular properties and global warming are rarely made explicit. To improve student knowledge about climate change, we developed a three-part activity that computationally and experimentally explores blackbody radiation, the greenhouse effect, and the relationship between IR absorption properties and global warming potentials for the anthropogenic greenhouse gases defined in the Paris Agreement. The activities addressed the traditional learning objectives of a quantum-focused physical chemistry course by exploring topics such as the quantized nature of energy in Planck’s Law, the selection rules for rovibrational transitions, and discrepancies between theoretical models and observed experimental results. However, our approach was unique in that each concept was addressed within the context of the atmospheric phenomena related to climate change. A previously published climate science survey instrument was administered pre- and postactivity to assess student learning gains. The average percent of correct responses on this survey increased from 44% to 68% as a result of completing the activities.

Methodology for assessing the heat potential recovery regime at food industry enterprises

Areas of improving energy saving and the environmental situation in the processing and food industry In Ukraine are relevant, as technologies and equipment by their nature and degree for efficient use of fuel resources are practically achievable for their improvement, especially today. The purpose of the study is to improve the methodology for the optimisation of the mode of reuse of the thermal potential of exhaust process gases in the implementation of a two-stage cooling process. The indicators of process gas emissions with a volume consumption of 0.54 m3 /s and temperature – 1600°C with the parameters of the furnace operation A2-SHBG were used to construct local temperature characteristics. Their construction is carried out based on the heat balance and heat transfer at short surface intervals, considering the parameters of coolant flows. The results were analysed by the Flow Vision software suite under the structure of the graph, according to the laws of thermodynamics. A method for calculating the amount of cold heat agent for reuse in the technological process is proposed. It is established that under the accepted heat exchange conditions, the required amount of atmospheric air with an initial temperature of -300°Ccan be heated to a temperature of +640°C, and with an initial temperature of +300°C, can be heated to +1450°C. Natural gas consumption will change from 20 m3 / h, without preheating atmospheric air, up to 12.7 m3 /h when heating atmospheric air in the heat exchanger at an initial temperature of + 300°C. It is stipulated that when calculating energy resource savings, it is necessary to consider the initial temperature of the cold heat agent when using the heat of exhaust process gases. The proposed method for calculating the optimal heat recovery mode allows calculating changes in the consumption of the primary fuel and energy resource and creating a database for the effective implementation of energy-saving technologies when reusing waste gas heat into production

Shale gas potential of Ordovician marine Pingliang shale and Carboniferous–Permian transitional Taiyuan-Shanxi shales in the Ordos Basin, China

The assessment of shale gas potential for the Ordovician Pingliang Formation and Carboniferous–Permian Taiyuan and Shanxi formations in the northwest margin of Ordos Basin, China provides insight into how fluctuation in depositional environments has a significant role on lithofacies and shale gas potential. To investigate the shale gas potential, a series of measurements (i.e. Rock-Eval pyrolysis, maceral composition analyses and X-ray powder diffraction, etc.) on representative outcrop samples were conducted to characterise shale properties. The organic matter from marine Pingliang shale is predominantly type I with a strong predominance of sapropelinite, whereas the transitional Taiyuan-Shanxi shales are dominated by types II to III kerogen. Furthermore, the Pingliang shale is characterised as a ‘poor’ source rock mainly owing to the lower total organic carbon (TOC) content (average 0.79 wt%) and higher maturity [average 1.78% in vitrinite reflectance (R o)], while the transitional Taiyuan-Shanxi shales are mostly characterised as ‘fair’ source rocks, and some samples with high TOC content (more than 2.0 wt%) present good source rocks. It is also found that the sedimentary environment, as a key factor determining the organic matter and TOC content, inevitably influences the type and content of minerals in shale, and controls the shale gas potential. For example, the transitional argillaceous Taiyuan-Shanxi shales are significantly different from the siliceous Pingliang shales, specifically, total clay content for the former is more than 50 wt%, while the latter is rich in quartz content (more than 70 wt%). Additionally, the quartz and clay contents of the Taiyuan shale range widely, especially the smectite content of I–S ML. The barrier coastal facies in the Taiyuan Formation are more conducive to the enrichment and preservation of organic matter because the Shanxi shale was deposited in shallow delta facies with a greater terrestrial influence. Conclusively, the Taiyuan and Shanxi formations have relatively good exploitation potential for shale gas, especially the relatively high TOC content (average 2.45 wt%) and moderate R o value (average 1.25%). For future exploration, selecting areas with relatively large shale thickness, high brittle mineral content, stable tectonics and better preservation conditions are key to optimising favourable exploration areas for shale gas. KEY POINTS The shale gas potentials of the argillaceous Taiyuan-Shanxi shales and siliceous Pingliang shale are compared. The influence of sedimentary facies on reservoir parameters of marine and transitional shales is established. This is a first detailed comparison of the marine and transitional shale gas potential in the northwest margin of Ordos Basin, China.

Coaly and lacustrine hydrocarbon source rocks in Permo-Carboniferous graben deposits (Weiach well, Northern Switzerland)

Permo-Carboniferous graben sediments in the North Alpine Foreland Basin (NAFB) include Upper Carboniferous (Stephanian) coal-measures and lower Permian (lower Autunian) lacustrine shales with high organic matter contents. Coals are probably the source for a gas accumulation in Switzerland, while the bituminous shales are potential source rocks for oil. In order to study the hydrocarbon potential of coal and bituminous shales and to contribute to the understanding of their depositional environment, 90 core samples from the Weiach-1 well (northern Switzerland) were investigated using organic petrographic, palynofacies, Rock-Eval pyrolysis, and geochemical techniques (incl. biomarker analysis and compound-specific carbon isotopy). Carboniferous coal seams are up to 10 m thick and were deposited in low-lying freshwater mires. They contain a significant gas potential and reached a maturity stage related to the onset of gas generation. Sapropelic rocks were not observed in the coal-bearing succession. Organic matter-rich Permian shales (Autunian shales) were deposited in anoxic lakes with a stratified water column. The organic matter is of mixed aquatic and terrigenous origin. δ13C values of chlorophyll-derived isoprenoids provide evidence for reworking of organic matter in the water column. The Autunian shales have a strongly varying, but locally very good oil potential. They reached early oil window maturity, but did not yet generate significant amounts of hydrocarbons. The main shale interval in the studied borehole is about 12 m thick and will generate about 0.35 tHC/m2 when mature. A comparison with literature data shows that it is possible to distinguish oils generated from Permian, Jurassic and Oligocene source rocks based on biomarker ratios and isotope data.

Theory and practice of unconventional gas exploration in carrier beds: Insight from the breakthrough of new type of shale gas and tight gas in Sichuan Basin, SW China

Unconventional gas in the Sichuan Basin mainly includes shale gas and tight gas. The development of shale gas is mainly concentrated in the Ordovician Wufeng Formation–Silurian Longmaxi Formation, but has not made any significant breakthrough in the Cambrian Qiongzhusi Formation marine shale regardless of exploration efforts for years. The commercial development of tight sandstone gas is mainly concentrated in the Jurassic Shaximiao Formation, but has not been realized in the widespread and thick Triassic Xujiahe Formation. Depending on the geological characteristics of the Qiongzhusi Formation and Xujiahe Formation, the feedback of old wells was analyzed. Then, combining with the accumulation mechanisms of conventional gas and shale gas, as well as the oil/gas shows during drilling, changes in production and pressure during development, and other characteristics, it was proposed to change the exploration and development strategy from source and reservoir exploration to carrier beds exploration. With the combination of effective source rock, effective carrier beds and effective sandstone or shale as the exploration target, a model of unconventional gas accumulation and enrichment in carrier beds was built. Under the guidance of this study, two significant results have been achieved in practice. First, great breakthrough was made in exploration of the silty shale with low organic matter abundance in the Qiongzhusi Formation, which breaks the traditional approach to prospect shale gas only in organic-rich black shales and realizes a breakthrough in new areas, new layers and new types of shale gas and a transformation of exploration and development of shale gas from single-layer system, Longmaxi Formation, to multi-layer system in the Sichuan Basin. Second, exploration breakthrough and high-efficient development were realized for difficult-to-produce tight sandstone gas reserves in the Xujiahe Formation, which helps address the challenges of low production and unstable production of fracture zones in the Xujiahe Formation, promote the transformation of tight sandstone gas from reserves without production to effective production, and enhance the exploration and development potential of tight sandstone gas.

The temperature dependence on the coherence time of a quantum pseudodot qubit

In this work, the energies and eigenfunctions of ground state and first-excited states (GFES) of a strongly coupled polaron in a quantum pseudo-dot (QPD) were studied by using variational method of Pekar type (VMPT). A single qubit can be realized in this two-level quantum system. Then, we calculated the coherence time of a QPD qubit by employing the Fermi Golden Rule. The temperature effects on the coherence time are taken into account by using the quantum statistics theory (QST) and self-consistent calculation method. According to the obtained results, it is found that the coherence time increases with decreasing temperature. Also, this time is a decaying function of the chemical potential of the two-dimensional electron gas and the zero point of the PHP.

Magnetic characteristics and tectonic structure of the Earth's crust of the Carpathian oil and gas region as a component of complex hydrocarbon criteria

For the first time, a qualitative and quantitative analysis of the geomagnetic field and oil and gas capacity was performed for the territory of the Carpathian region, which made it possible to reveal the connection of hydrocarbon deposits with the magnetization of the Earth’s crust at the regional and local levels and the features of the deep structure of the Earth’s crust according to seismic data. The regularity of the distribution of oil and gas deposits of the Carpathian oil and gas-bearing region revealed by geomagnetic criteria is confirmed by their connection with regional and local anomalies of the gravity field and heat flow density. According to the analysis of the regional geomagnetic field and magnetic models along the PANCAKE and RomUkrSeis geotraverses, gas fields are located above the magnetic blocks of the middle and lower parts of the Earth’s crust or in their marginal parts, and oil fields are located above practically non-magnetic deep blocks. Under the thrust part of the Carpathian arc, the regional features of the Earth’s crust structures are clearly manifested, namely, starting from the longitude of the city of Rakhiv, the submeridional direction of extension of regional anomalies of magnetic, gravity, and thermal fields and their horizontal gradient zones prevails. The oil and gas potential of the region is in good agreement with this — the gas fields are timed to the minimum values of the regional horizontal gradient of the regional magnetic field, to the increased gradient of Bouguet anomalies, as well as to the minimum values of the horizontal gradient of heat flow density anomalies. In local geophysical fields, gas fields are gravitating: to weakly negative magnetic anomalies and their gradient zones; to negative anomalies of the gravitational field predominantly; to positive anomalies of heat flow density in the northwest, within the area of Trans-European suture zone (without the middle of the Krakovets fault), and negative anomalies in the Carpathian trough. Oil and oil condensate deposits are correlated with a band of positive magnetic field anomalies, negative gravity field anomalies, and increased heat flux density values. The main deep faults of the Carpathian region and the marginal part of the Platform in the first approximation can be considered Velikomostivsko-Chernivetsky, which characterizes the change in the character of magnetic and gravity fields and heat flow density, Rava-Rusky, which reflects the zone of articulation of the Eastern and Western European platforms, Pre-Carpathian — the border of the Pre-Carpathian trough and the Folded Carpathians on the Earth’s surface (as well as the boundary of the Archaean(?)-Paleoproterozoic and Meso-Neoproterozoic crust according to the modern international chronostratigraphic scale), as well as the Transcarpathian fault. On the basis of magnetic and seismic data, the hypothetical depth position of these faults and the possible connection with them of hydrocarbon flows into the upper part of the Earth’s crust are proposed. Therefore, the geomagnetic criteria of the oil and gas bearing capacity of the Earth’s crust of the Carpathian region are agreed based on the results of the study of the gravity field and heat flow density anomalies, which makes it possible to predict the spread of oil and oil condensate and gas and gas condensate deposits according to the regional and local features of these fields in a first approximation.