ABSTRACT Climate change requires an immediate transition from fossil fuels to clean energy sources. Although hydrogen is considered a future energy source, over 90% of hydrogen is currently produced from fossil fuels, and large-scale renewable-fed hydrogen processes are limited by current technologies and economic processes. Therefore, hydrogen production from fossil fuels is a significant topic, particularly if fossil fuel-fed hydrogen production and utilization can be absolutely carbon-free. For the first time, this review critically discusses and analyzes the current advances and fundamentals of fossil fuel dehydrogenation from the perspective of techno-economic-environmental assessments while considering all potential fossil resources and hydrogen technology. This review concludes that the preference of fossil fuels for any hydrogen production technology is as follows: fossil gas > heavy fossil liquid > light fossil liquid > fossil minerals. Thermo-catalytic hydrocarbon decomposition can outperform most other hydrocarbon reforming and pyrolysis processes owing to its energy efficiency, economic effectiveness, and environmental friendliness. Further, we explore potentially new “green hydrogen” technology and confirm that fossil fuels could be completely decarbonized throughout the full-chain stages from exploration to production and consumption. Overall, this work reveals that fossil fuels can be utilized completely carbon-free and provides technical support for future fossil fuel dehydrogenation and energy decarbonization in academic research, industrial practice, and governmental strategies.
It is significant to accurately evaluate the relative permeability of oil–water two phase for multiphase seepage in porous media in low permeability and tight oil reservoir. However, stress sensitivity is an important characteristic for low permeability and tight oil reservoir. It is an effective way for fractal theory to describe the complexity and heterogeneity of the microstructure of porous media. To describe the relative permeability of oil–water two phase in porous media with complex and irregularity pores, a new relative permeability model oil–water two phases is proposed by the fractal theory and the stress sensitivity is taken into the established model in this paper. Meanwhile, the effects of effective stress, elastic modulus, porosity, maximum and minimum flow radius on oil–water relative permeability are analyzed. The new model is verified by comparing with the laboratory data and the results demonstrate that irreducible water and residual oil saturation have a negative correlation with effective stress. The relative permeability of the oil–water two-phase will shrink to the middle as the rise of effective stress, and the region of co-infiltration will decrease. The deformation quantity of porous media, irreducible water and residual oil saturation will increase as the elastic modulus decreases. The larger the maximum flow radius is, the lower the irreducible water saturation and residual oil saturation is. Both the porosity and the minimum flow radius have slight influences on the relative permeability of oil–water two-phase. The proposed relative permeability model can effectively predict the relative permeability of oil and water and help to describe and reveal the multiphase flow in porous media.
Injecting CO2 into depleted gas reservoirs can sequester greenhouse gases and simultaneously enhancing gas recovery, which has significant environmental and economic benefits. Natural gas resources in tight sandstone reservoirs are huge, but the gas production decreases rapidly and the gas recovery is low due to poor reservoir properties. When these gas reservoirs are depleted, the implementation of CO2 flooding has greater potential to improve gas production and store CO2. However, the production characteristics of the CO2 flooding process and application potential in tight gas reservoirs at the field scale are not yet clear. To fully understand the production mechanism of the CO2 flooding and evaluate the technical feasibility, based on the geological data of the Sulige gas field in the Ordos Basin, a 3D numerical simulation model under the five-point well pattern is established. The production behavior of enhanced gas recovery and CO2 storage processes is studied through numerical simulation approach. Results indicate that the CH4 production rate is significantly increased after CO2 flooding, and the gas recovery can be increased by up to 19.2%, confirming the feasibility of CO2 injection to enhance CH4 production in depleted tight gas reservoirs. Once the CO2 breakthrough occurs, the CH4 production rate decreases rapidly, and the CO2 distribution is only slightly affected by the gravity difference of the components. These characteristics are significantly different from those of high-permeability gas reservoirs. The CO2 front in the early stage is proportional to the square root or cube root of time, depending on the perforation location and reservoir thickness. However, the CO2 front in the late flood stage shows a linear relationship with the square of time. It is recommended that injection well and production wells are completely perforated because the enhanced gas recovery is higher than other perforation options and excessive bottom-hole pressure in the injection well can be avoided. The new findings of this work can provide some insights into the production mechanism of CO2 storage and enhanced recovery in tight gas reservoirs, which is beneficial for reducing investment risks and improving production efficiency for future large-scale field applications.
This paper discusses the so-called Bakers’ Strike Edict from Ephesus (Ephesos 231 = IK 12.215 p. 27) in light of recent studies on the Roman imperial toolkit to build empire-wide communities. Clifford Ando and Myles Lavan argued that Roman emperors in the first two centuries CE were consciously blurring distinctions between Roman and non-Roman populations, so that there could be a shared sense of an empire-wide community among people in the provinces. This paper argues that, in addition to Lavan’s observations, gubernatorial edicts also show concerns and measures that sought to communicate a sense of the communal at the local level. While the focus of discussion is on the edict responding to a bakers’ strike at Ephesus, several other examples from a corpus of gubernatorial edicts are also used in connection with this example. This paper hopes to contribute to Ando’s and Lavan’s arguments by pointing to a lower register of community building visible in gubernatorial edicts. The governors’ concerns for and efforts to creating communal cohesion and their need to balance parallel and at times competing “common goods” not only adds another nuance to the grander community building project at the imperial level, but demonstrates further complications on how praesidial governors – and in particular proconsuls – can and would react to difficult issues at the local level.