Large Quantities Of Natural Gas Research Articles

A Novel Performance Evaluation Method for Gas Reservoir-Type Underground Natural Gas Storage

The regulation of the seasonal energy supply for natural gas and the storage of fossil energy are important to society. To achieve it, storing a large amount of natural gas in porous underground media is one of the government’s choices. Due to the successful lesson learned from the oil and gas industry, natural gas storage in underground porous media has been regarded as the most potential long−term energy storage method. In this paper, we developed a new workflow to evaluate the performance of gas reservoir−type underground natural gas storage (UGS). The theoretical background of this workflow includes the correction of the average formation pressure (AFP) and gas deviation factor by error theory and the analytical mathematical model of UGS wells. The Laplace transform, line source function, and Stehfest numerical inversion methods were used to obtain pressure solutions for typical vertical and horizontal wells in UGS. The pressure superposition principle and weighting method of the gas injection−withdrawal rate were used to obtain the AFP. Through the correction of the AFP and gas deviation factor in the material balance equation, the parameters for inventory, effective inventory (the movable gas volume at standard condition), working gas volume (the movable gas volume is operated from the upper limit pressure to the lower limit pressure), and effective gas storage volume (the available gas storage volume at reservoir condition) were determined. Numerical data from the numerical simulator was used to verify the proposed model pressure solution. Actual data from China’s largest Hutubi UGS was used to illustrate the reliability of the proposed workflow in UGS performance evaluation. The results show that large−scale gas injection and withdrawal rates lead to composite heterogeneity in gas storage wells. The nine injection and production cycles’ pressure and effective inventory changes from Hutubi UGS can be divided into a period of rapid pressure rise and a period of slow pressure increase. The final AFP is 32.8 MPa. The final inventory of the Hutubi UGS is 100.1 × 108 m3, with a capacity filling rate (the ratio of effective inventory to designed gas storage capacity) of 93.6%. The effective inventory is 95.3 × 108 m3, and the inventory utilization ratio (the ratio of effective inventory to inventory) is 95.2%. The working gas volume is 40.3 × 108 m3. This study provides a new method for inventory evaluation of the gas reservoir−type UGS.

Geochemical characteristics and gas-washing accumulation mechanism of hydrocarbon from the Xihu Sag, East China Sea Basin

For many petroleum production plays with large amounts of natural gas produced, their hydrocarbon accumulation processes have been reported to be commonly involved with gas-washing. The gas generation intensity of the Xihu Sag, East China Sea Basin is up to 6 × 106 t/km2, which is the primary driving force for gas-washing to occur. 18 oils and 20 gas samples produced from the Eocene – Oligocene sandstone reservoirs in the Xihu Sag has been geochemically characterized to delineate the controlling factor of the gas-washing and in turn better understand the hydrocarbon accumulation mechanism of the study area. The results show that the natural gas is primarily mature-highly mature coal-type gas based on their carbon isotope characteristics. The oils are believed to belong to a same oil family with a similar thermal maturity and have been gas-washed based on either their molecular fingerprints or other geochemical characteristics. The high toluene/n-heptane ratio (Tol/nC7) and high n-alkane mass depletion (Q) of the oils further indicate the occurrence of gas washing. A good correlation between either the reservoir depth or the gas generation intensity of the source kitchen and the n-alkane mass depletion of the crude oil indicate reservoir depth and gas generation intensity are the two primary controlling factors on the gas washing of the study area. In order to further delineate the effects of evaporative fractionation or migration fractionation on the hydrocarbon reservoir, we introduced a new cross plot of n-alkanes mass depletion (Q) versus adamantane/diamantine (A/D) to type the oils related to the gas washing in the study area. The meaning of this paper for the exploration of oil and gas resources will be related to the understanding of different gas washing mechanism, so as to further enhance the exploration efficiency.

An integrated model with stable numerical methods for fractured underground gas storage

Underground gas storage formed from the depleted oil/gas reservoir has excellent development potential for storing a large amount of natural gas. However, the reservoir in some regions is mostly a fractured structure. Its pore distribution and permeability theory are complex. An integrated model for the fractured underground gas storage (UGS) formed from the depleted oil/gas reservoir is proposed for the first time to respond to the absence of the numerical model. This integrated model couples the wellbore, reservoir and gas properties. We propose a gas flow direction factor and transient heat transfer models for the alternative flow directions in the wellbore. Natural gas property models are adopted to describe gas properties more accurately. We analyze the stability, efficiency and global mass conservation of the reservoir model. A new equation for source term is proposed to solve the reservoir model stably and efficiently. A pressure correction method is proposed to guarantee global mass conservation for long period operation of the UGS.Our simulation results indicate that the new equation for the source term ultimately ensures diagonal dominance and improves 20%–30% computational efficiency. The pressure correction method strictly guarantees global mass conservation. By simulating the entire cycle of gas injection, wellbore shutdown and gas production, we determine the maximum gas storage capacity of the UGS and analyze the variation law of pressure and temperature in the wellbore and reservoir.

우크라이나-러시아 전쟁으로 인한 에너지위기와 독일의 대응

The Ukrainian-Russian War caused an energy crisis in Germany. Germany imports large amounts of natural gas from Russia. Germany's dependence on Russia for natural gas supply has been a long-standing situation. For Germany, this situation was not a big problem before the Ukrainian-Russian War. However, after the Ukrainian-Russian War, the Western Bloc imposed economic sanctions against Russia. And in response, Russia also started sanctions against the Western Bloc. Russia used natural gas as a weapon to pressure Germany, but this was not limited to simply reducing or banning exports. Russia intended to liquidate Gazprom Germania GmbH, a German company belonging to the Gazprom Group. If this company went liquidated, Germany's natural gas supply and demand would be seriously disrupted, so Germany implemented trust management as an administrative measure to prevent liquidation of this company. The purpose of this paper is to review Germany's response to the energy crisis caused by the Ukraine-Russia war by examining specific cases and individual legal systems of Germany's trust management system.

Origin of natural gas within the deep-sea uncompacted sediments of the Shenhu area, northern South China Sea: Geochemical and methanogenic cultivation results

Large amounts of natural gas are dispersed at low concentrations or have accumulated to form highly saturated gas hydrates within uncompacted deep-sea (water depth usually >500 m) sediments worldwide. However, studies on their origin and microbial genetic mechanism are scarce. Using the gas hydrate prolific region of the Shenhu area in the northern South China Sea as our study area, we systematically investigated the genetic types and generation pathways of the natural gas in those sediments based on gas geochemical and anaerobic methanogenic cultivation results. Our results indicated that natural gas within the uncompacted deep-sea sediments in the Shenhu area is dominated by microbial methane (>95%) with a minor amount of biodegraded hydrocarbon (ethane to propane) (<1%). The microbial methane within the highly saturated gas hydrate reservoir was produced by hydrogenotrophic methanogens in the deeper buried optical methanogenic zone (25 °C < in-situ temperature <85 °C), rather than in the in-situ gas hydrate layer. However, the primary microbial gas generative potential of the upper part of the methanogenic zone (28–300 mbsf) in the Shenhu area is relatively poor because of insufficient methanogenic substrates. These findings suggest a strong vertical heterogeneity of methanogenesis potential in the methanogenic zone in the Shenhu area, which may be a common phenomenon in the worldwide marine sediment environments, especially in the regions with relatively low organic matter richness.

All that is Frozen Melts into the Sea: Arctic Gas, Science, and Capitalist Natures

ABSTRACT Considerable ecological Marxist analysis has investigated the centrality of nonhuman natures such as soil, forests, and rivers in capitalist accumulation: not only the importance of overcoming natural barriers but appropriating the unpaid productivity of natures for free or low cost. The frozen materiality of ice, however, is a particularly unruly and disagreeable nature that defies most attempts to easily subsume it within capital. This article examines the efforts by the Polar Gas Project – a lengthy pipeline proposed during the 1970s that would have shipped large quantities of natural gas from the Canadian Arctic to southern markets – and specific attempts to develop reliable ice science to facilitate its development. Applying Collard and Dempsey’s analytic of five orientations of capitalist natures, this article examines Polar Gas’ attempted production of ice as an “underground infrastructure,” “outcast surplus,” and “threat.” Through this, empirical evidence of scientific work to produce capitalist natures is detailed and the specific materiality of ice examined in the context of proposed accumulation, revealing the historical limits of capital’s production and remaking of nature.

Accumulation mechanism and model of coal measure derived oil and gas in the deep reservoir of Huanghua Depression, Bohai Bay Basin, China

Hydrocarbon accumulation in coal measure strata is consist of several types which includes intra-source accumulation and adjusted accumulation, particularly in basins that had experienced multi-stage tectonic activities. The mechanism governing this accumulation is extremely complex. Using the Paleozoic petroleum system in the Huanghua Depression as an example, the mechanism of hydrocarbon accumulation in deep reservoirs can be revealed by means of core observation, geochemistry testing of coal measure source rock, thin section observation, fluid inclusions testing, and profile analysis of typical reservoirs, combined with the burial and thermal history of strata. Based on the regional tectonic, the mechanism of hydrocarbon accumulation in coal measures is defined and the accumulation model was established. The results show that the Paleozoic petroleum system in the Huanghua Depression has three different types of source-reservoir-cap assemblages: under-source, intra-source, and above-source assemblage. Regional tectonic evolution controlled the hydrocarbon generation process of source rocks, showing the hydrocarbon generation characteristics of “oil in the early stage and gas in the late stage.” The Middle Cretaceous is the first of two periods of hydrocarbon accumulation, during which stage occurred in low-maturity oil and a small amount of natural gas were mainly stored in intergranular pores and dissolution pores. The tectonic uplift in the Late Cretaceous caused the destruction of the ancient reservoir. The second accumulation stage occurred in the Middle Paleogene to the present. A large amount of natural gas and high maturity oil were mostly stored in dissolution pores and structural fractures. The hydrocarbon accumulation in Huanghua Depression was simultaneously regulated by reservoir reformation, tectonic activities, and source rock maturation. Based on the foregoing understanding, the hydrocarbon accumulation model of “oil and gas transfer station” in coal measures is put forward, that is, oil and gas are first accumulated in intra-source or near-source reservoirs, and are then adjusted from this “oil and gas transfer station” to other areas as a result of tectonic activity.

China’s LNG import risk assessment based on the perspective of global governance

The uncertainty of LNG import risks will have a significant impact on China's energy security. This paper establishes a multi-agent game model based on the current LNG transportation network and global LNG supply and demand pattern, evaluates the LNG import risks faced by China under the global governance model, and simulates and predicts the optimal LNG import strategy of China in 2030. The research results show that between 2007 and 2020, China’s LNG import risks increased rapidly compared with political risks and national risks. From the perspective of risk identification, the comprehensive risk of China's imports from Southeast Asia and Australia is lower. However, due to the increasing demand gap for LNG, the Middle East, and Africa are still necessary supply sources. It is estimated that by 2030, the future LNG market will be oversupplied, and the United States is expected to become the world's top LNG supplier. China will reduce its dependence on Africa and the Middle East, and import a large amount of natural gas from the United States, Australia, Qatar, and Russia to reduce supply risks. From the perspective of import market competition, the new analysis model proposed in this article provides an effective tool for exploring the optimal strategy for LNG import.

Decarbonization of natural gas systems in the EU – Costs, barriers, and constraints of hydrogen production with a case study in Portugal

The European Union (EU) imports a large amount of natural gas, and the injection of renewable hydrogen (H2) into the natural gas systems could help decarbonize the sector. The new geopolitical and energy market situation demands urgent actions in the clean energy transition and energy independence from fossil fuels. This paper aims to investigate techno-economic analysis, barriers, and constraints in the EU policies/frameworks that affect natural gas decarbonization. First, the study examines the levelized cost of hydrogen production (LCOH). The LCOH is evaluated for blue and grey hydrogen, i.e., Steam Methane Reforming (SMR) natural gas as the feedstock, with and without carbon capture, and green hydrogen (three type electrolyzers with electricity from the grid, solar, and wind) for the years 2020, 2030, and 2050. Second, the study evaluates the current policies and framework based on a SWOT (Strength, Weakness, Opportunities, and Weakness) analysis, which includes a PEST (Political, Economic, Social, and Technological) macro-economic factor assessment with a case study in Portugal. The results show that the cheapest production costs continue to be dominated by grey hydrogen (1.33 €/kg.H2) and blue hydrogen (1.68 €/kg.H2) in comparison to green hydrogen (4.65 €/kg.H2 and 3.54 €/kg.H2) from grid electricity and solar power in the PEM - Polymer Electrolyte Membrane for the year 2020, respectively. The costs are expected to decrease to 4.03 €/kg.H2 (grid-electricity) and 2.49 €/kg.H2 (solar – electricity) in 2030. The LCOH of the green grid-electricity and solar/wind-powered Alkaline Electrolyzer (ALK) and Solid Oxide Electrolyzer Cell (SOEC) are also expected to decrease in the time-span from 2020 to 2050. A sensitivity analysis shows that investments costs, electricity price, the efficiency of electrolyzers, and carbon tax (for SMR) could play a key role in reducing LCOH, thereby making the economic competitiveness of hydrogen production. The key barriers are costs, amendments in rules/regulations, institutions and market creation, public perception, provisions of incentives, and constraints in creating market demand.

Study on the Microscopic Pore Structures of Coal Measure Reservoirs in the Shanxi Formation, Eastern Ordos Basin

The Carboniferous-Permian coal measures in China contain abundant natural gas resources. Shale, coal and tight sandstone reservoirs are developed in coal measures, and the quantitative characterization of the pore structures of different types of reservoirs can provide scientific guidance for the sweet spot prediction of tight reservoirs. In this study, taking the Shan 2 Member coal measure of the Shanxi Formation in the eastern Ordos Basin as an example, the pore structures of shale, coal rock and tight sandstone were systematically studied based on organic geochemistry, scanning electron microscopy, high-pressure mercury injection, and low-temperature N2 and CO2 adsorption experiments. The results show that the microscopic pore structures of different types of reservoirs in the Shan 2 Member coal measures are quite different. Shale and tight sandstone mainly develop clay mineral pores at mesopore scale, followed by intragranular and dissolution pores developed in quartz and feldspar minerals, while organic pores are rarely developed. A large number of macro-scale clay mineral pores and micro-fractures are developed in tight sandstone, meanwhile the pore connectivity of tight sandstone is better than that of shale. A large number of micro to nano-scale organic pores are developed in coal, and the specific surface area of micropores in coal is much larger than that of mesopores in shale and tight sandstone. Sandstone, shale, and coal are frequently interbedded in coal measure strata. Tight sandstone provide the main storage space for free gas, and pores in shale and coal absorb a large amount of natural gas. Sandstone-shale-coal assemblages and sandstone-coal assemblages are the key targets for the exploration of hydrocarbons in the Shanxi Formation coal measures in the study area.

The Structure of Permafrost in Northern West Siberia: Geophysical Evidence

The permafrost of Arctic West Siberia stores extremely rich resources of hydrocarbon fuels that remain a key energy source and an important element of the global economy. A large amount of natural gas in permafrost is bound in gas hydrates which may become an alternative fuel of the future. Shallow subsurface in the permafrost area of northern West Siberia has been studied by transient electromagnetic (TEM) soundings to estimate the permafrost thickness and to detect faults as channels for fluids and heaving features as possible indicators of gas hydrate accumulations. The shallow transient electromagnetic (sTEM) surveys were conducted in discontinuous and continuous permafrost at two sites in northern West Siberia (the northeastern Yamal Peninsula and the southern Gydan Peninsula), with a focus on the vicinities of lakes and cryogenic landforms (frost mounds). The sTEM method resolves well the heterogeneous permafrost structure, with faults, numerous unfrozen zones (taliks), and frost mounds marked by resistivity and seismic anomalies. Some lakes are located above faults, and their origin may be related to deformation, whereas the frost mounds may mark deep-seated fluid dynamic processes. Local thickening of permafrost may be associated with the presence of gas hydrates. The detected features may trace gas migration pathways and reveal possible sites of gas emission.

Natural gas accumulation in the basin–mountain transition zone, northwestern Sichuan Basin, China

The basin–mountain transition zone is an important area for hydrocarbon exploration. To better understand the process and mechanism of hydrocarbon accumulation in this area, the middle Permian Qixia Formation at the piedmont of the Longmenshan Mountains, northwestern Sichuan Basin, China, was investigated. It is showed that natural gas in the Qixia Formation in the thrust belt (i.e., the Kuangshanliang and Hewanchang areas) was derived from lower Cambrian strata by oil cracking. The reservoirs are filled with amounts of bitumen, which reflects strong oil charging. However, the gas accumulation is not rich, which is due to the later destruction of hydrocarbon accumulations by the invasion of meteoric waters. In contrast, in the thrust front (i.e., the Shuangyushi area) and forebulge belt (i.e., the Jiulongshan area), the reservoirs contain few bitumens and large amounts of natural gas, which is indicative of good preservation for hydrocarbon accumulation. The natural gas was mainly derived from kerogen cracking in middle Permian source rocks, although it was mixed with a small amount of lower Cambrian-derived oil-cracking gases. The thrust front and forebulge belts occur in areas of lesser deformation, and thus are favorable for gas accumulation, due to the strata containing both sapropel- and humic-type source rocks and reservoirs. It is generalized that hydrocarbon resources in (ultra-)deep strata in the basin–mountain transition zone may be an important target for exploration worldwide.

Microstructure and Mechanical Properties of GTAW Welded Joint of Invar Alloy

Experiment of automatic gas tungsten arc welding of liquefied natural gas carrier Invar alloy with a thickness of .7 mm was completed, and the welding parameters were optimized, as well as microstructure and mechanical properties of the welded joint were measured and analyzed. The grain size of the area near the weld centerline was small, mainly cellular dendrites, and the grain size on both sides of the weld centerline increased gradually, mainly dendrites, whereas the grain size near fusion line was larger, and there were more columnar crystals. The heat-affected zone was composed of coarse austenite grains. Transgranular cracks were the main cracks in the welding seam. When welding current was 40 A, frequency was 120 Hz, and welding speed was 350 mm/min, tensile strength of the welded joint was 446.9 MPa, which 88.1% of the base metal’s tensile strength and 10.3% of the fracture elongation. The fracture surface of tensile specimens showed typical plastic fracture characteristics, with no obvious crack characteristics, and no eutectic liquid films were observed. Introduction Invar alloy is a Fe–36%Ni alloy. Its thermal expansion coefficient at room temperature is less than 1.6X10-6/k, which is about one-tenth of that of low carbon steel, and changes little in a larger temperature range. Therefore, Invar alloy is widely used in making precision measuring instruments and low temperature-resistant materials (Corbacho et al. 1998; Park et al. 2011; Qiu et al. 2016; Yakout et al. 2018). In recent years, with the increasing demand for clean energy, liquefied natural gas (LNG) carriers are developing rapidly (Zhao et al. 2015; Oh et al. 2018). LNG liquefies at temperatures below -161.5°C. The volume of LNG is about 1/ 625 of the volume of gaseous natural gas of the same mass; thus, it can transport large quantities of natural gas over long distances.

Phase Behavior Identification and Formation Mechanisms of the BZ19-6 Condensate Gas Reservoir in the Deep Bozhong Sag, Bohai Bay Basin, Eastern China

Significant developments have been observed in recent years, in the field of deep part exploration in the Bozhong Sag, Bohai Bay Basin in eastern China. The BZ19-6 large condensate gas field, the largest gas field in the Bohai Bay Basin, was discovered for the first time in a typical oil-type basin. The proven oil and gas geological reserves in the deeply buried hills of the Archean metamorphic rocks, amount to approximately 3 × 10 8 tons of oil equivalent. However, the phase behavior and genetic mechanisms of hydrocarbon fluids are still unclear. In this study, the phase diagram identification method and various empirical statistical methods, such as the block diagram method, φ 1 parameter method, rank number method, and Z -factor method were implemented to comprehensively identify the phase behavior types of the BZ19-6 condensate gas reservoir. The genetic mechanism of the BZ19-6 condensate gas reservoir was investigated in detail through analyses of physical properties of the fluid at high temperatures and pressures, organic geochemical characteristics of condensate oil and gas, and regional tectonic background. Consequently, this study is shown as follows: (1) The BZ19-6 condensate gas reservoir is a part of a secondary condensate gas reservoir with oil rings, formed synthetically since the Neogene period due to multiple factors, such as retrograde evaporation from deep burial and high temperature, inorganic CO2 charging from the deep mantle, and late natural gas invasion. (2) The hydrocarbon accumulation process of the BZ19-6 condensate gas reservoir is as follows: First, a large amount of oil is accumulated at the end of the lower Minghuazhen deposition (5 Ma BP); second, a large amount of natural gas is generated in the deep-source kitchen and mantle-derived inorganic CO2 charged into the early formed oil reservoirs at the end of the upper Minghuazhen deposition (2 Ma BP). As a result, the content of gaseous hydrocarbons in the hydrocarbon system of the reservoir increased, which led to large amounts of liquid hydrocarbons dissolved in gaseous hydrocarbons and significantly reduced the critical temperature of the hydrocarbon system. Therefore, existing secondary condensate gas reservoirs are formed when the critical temperature is lower than the formation temperature and it enters the critical condensate temperature range.

Formation of a Low-Density Liquid Phase during the Dissociation of Gas Hydrates in Confined Environments.

The large amounts of natural gas in a dense solid phase stored in the confined environment of porous materials have become a new, potential method for storing and transporting natural gas. However, there is no experimental evidence to accurately determine the phase state of water during nanoscale gas hydrate dissociation. The results on the dissociation behavior of methane hydrates confined in a nanosilica gel and the contained water phase state during hydrate dissociation at temperatures below the ice point and under atmospheric pressure are presented. Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction (PXRD) were used to trace the dissociation of confined methane hydrate synthesized from pore water confined inside the nanosilica gel. The characterization of the confined methane hydrate was also analyzed by PXRD. It was found that the confined methane hydrates dissociated into ultra viscous low-density liquid water (LDL) and methane gas. The results showed that the mechanism of confined methane hydrate dissociation at temperatures below the ice point depended on the phase state of water during hydrate dissociation.

A new-structure grey Verhulst model for China’s tight gas production forecasting

Tight gas, shale gas and coalbed gas are recognized as the three sources of unconventional natural gas in the world. Currently, China’s tight gas production is at an absolute advantage. Hence, a reasonable prediction of tight gas production is of great value to China’s government in formulating energy policies. In this study, the data characteristics of China’s tight gas production were analysed. Then a new-structure grey Verhulst model for predicting China’s tight gas production was employed, and the time response function and initial value optimization method of the new model were deduced. Next, the new model was used to simulate and predict China’s tight gas production. The comprehensive error was 2.07%, which was much smaller than that of the traditional grey Verhulst model (7.78%) and the GM(1,1) model (18.57%). Finally, China’s tight gas production was predicted and analysed. The results show that the growth of China’s tight gas production will slow down in the next three years due to the high cost of tight gas exploitation. Therefore, Chinese government should speed up tight gas exploitation through policy support; meanwhile, China needs to continue importing large quantities of natural gas to ensure sufficient domestic supply of natural gas.

Study on Prediction Model About Water Content in High-Temperature and High-Pressure Water-Soluble Gas Reservoirs

Abstract Because of a large amount of natural gas dissolved in the formation water of high-temperature and high-pressure (HTHP) water-soluble gas reservoirs, the water vapor content in water-soluble gas reservoirs is generally maintained under a supersaturated state; meanwhile, natural gas has a high carbon dioxide fraction, which significantly affects the water vapor content. Application of the conventional method to calculate the water content of HTHP water-soluble gas reservoirs leads to errors. In this work, the water content of HTHP water-soluble gas reservoirs was studied through laboratory experiments and theoretical research, and the main factors affecting water content were studied. Results show that the water content of water-soluble gas reservoirs decreases as pressure increases. The water content decreases faster in the low-pressure stage, while the decease of water content in the high-pressure stage is relatively steady. The water content of gas reservoirs increases with increasing temperature. When the temperature is lower than 100 °C, the change is slow; when the temperature is higher than 100 °C, the change is fast. The water content of gas reservoirs is affected by temperature during the low-pressure stage. The water content in the high-temperature stage is obviously affected by pressure; the water content of the gas reservoir is also affected by the carbon dioxide content of the natural gas component and the salinity of the formation water. Higher carbon dioxide content and lower formation water salinity yield higher water content. Furthermore, error analysis of the conventional water content prediction method and the measurement shows inconsistency in measurement and calculation. The error between the two methods is large, with an average of 54.88%. Based on the experiment, a mathematical model for calculating the water content of HTHP water-soluble gas reservoirs was established considering pressure, temperature, salinity, and natural gas composition. The predicted water vapor content of natural gas is close to the experimental value with a high precision. The average relative error between the measured and model calculated value is about 8.72%.

Methane emissions from the Munich Oktoberfest

Abstract. This study presents the first investigation of the methane (CH4) emissions of a large festival. Munich Oktoberfest, the world's largest folk festival, is a potential source of CH4 as a large amount of natural gas for cooking and heating is used. In 2018 we measured the CH4 emissions of Oktoberfest using in situ measurements combined with a Gaussian plume dispersion model. Measurements were taken while walking and biking around the perimeter of the Oktoberfest premises (Theresienwiese) at different times of the day, during the week and at the weekend. The measurements showed enhancements of up to 100 ppb compared to background values and measurements after Oktoberfest. The average emission flux of Oktoberfest is determined as (6.7±0.6) µg (m2 s)−1. Additional analyses, including the daily emission cycle and comparisons between emissions and the number of visitors, suggest that CH4 emissions of Oktoberfest are not due solely to the human biogenic emissions. Instead, fossil fuel CH4 emissions, such as incomplete combustion or loss in the gas appliances, appear to be the major contributors to Oktoberfest emissions. Our results can help to develop CH4 reduction policies and measures to reduce emissions at festivals and other major events in cities. Furthermore, events with a limited duration have not yet been included in the state-of-the-art emission inventories, such as TNO-MACC, EDGAR or IER. Our investigations show that these emissions are not negligible. Therefore, these events should be included in future emission inventories.

Entropy generation rate minimization for steam methane reforming reactor heated by molten salt

Traditional steam methane reforming facilities for producing hydrogen not only consume a large amount of natural gas, but also emit a lot of greenhouse gas. Considering the utilization of clean energy, the reduction of carbon dioxide emission, and the production of chemicals, this paper establishes a model of steam methane reforming reactor heated by molten salt by utilizing finite-time thermodynamics. In order to reduce the irreversibility of this reactor, the entropy generation rate minimization and some operating parameters are taken as the optimization objective and variables, respectively. The hybrid particle swarm optimization algorithm is proposed for solving this model. Afterwards, the influences of the porosity of the catalyst bed and catalyst activity on the optimal performance are analyzed. The results indicate that the total entropy generation rate of the reactor is reduced by 22.08% after optimizing the inlet parameters of the molten salt and reaction mixture. Within the scope of this study, the total entropy generation rate of the optimal reactor decreases with the increasing porosity of catalyst bed. When the catalyst activity decreases, the hydrogen production rate can remain constant by adjusting the operating parameters. The obtained results are favorable to guide the optimal design of the practical reactors.

Evaluation of Potential for Salt Cavern Gas Storage and Integration of Brine Extraction: Cavern Utilization, Yangtze River Delta Region

The Yangtze River delta region of China consumes a large amount of natural gas, but the current gas storage facilities of this region can provide only 19.6 × 108 m3 of natural gas for use, which will be far less than the required gas storage volume of 66.8 × 108 m3 in 2030. The reason is due to lacking suitable underground gas storage space. To meet the space demands of underground gas storage (UGS) in the Yangtze River Delta region, the feasibilities of UGS construction in salt formations including depth of mines, thickness of salt strata, distance to pipelines, and geologic safety of the salt mines are evaluated. The representative blocks of Huai’an salt mine and Fengxian salt mine are suggested as potential sites for UGS construction. To promote UGS construction operation quickly and economically, utilizing the existing caverns can be considered firstly. The evaluation indicates that the existing caverns can store about 12.91 × 108 m3 natural gas for UGS with a cavern utilization rate of 30%. To satisfy the space for residual gas storage, the idea of “integration of brine extraction and cavern utilization” is put forward; that is, salt mining enterprises carefully control the usability of newly increased cavern volume during brine extraction. The forecast shows that about 36.9% of the newly increased cavern volume is sufficient to meet the residual cavern demand of UGS to fulfill a gas store volume of 34.3 × 108 m3 in 2030 in the Yangtze River delta. This research provides an effective method to solve the space need for UGS in the Yangtze River delta; simultaneously, it also presents win–win cooperation for the utilization of abandoned caverns and energy storage.