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•A thermodynamic formula of solubility parameter in nanoscale/nanopores derived.•Solubility parameters of the oil and gas phases in nanopores initially calculated.•Apply solubility ...parameters to calculate MMPs in nanopores firstly developed.•Temperature and composition effects on solubility parameter and MMPs examined.•Millimeter and nanometer-scale solubility parameter and MMPs are different.
In this paper, solubility parameters and minimum miscibility pressures (MMPs) of five tight oil–CO2 systems are calculated in millimeter to nanometer scales. First, the Peng–Robinson equation of state (PR-EOS) is modified to calculate the vapour–liquid equilibrium in nanopores by considering the effects of capillary pressure and shifts of critical temperature and pressure. Second, a thermodynamic formula of the solubility parameter is derived and presented from the modified PR-EOS, which is applied to calculate the solubility parameters in nanopores. Third, the MMPs are estimated from the newly-developed solubility parameter-based method, at which the difference between the solubility parameters of oil and gas phases (Δδ) approximately equals to 3.0(cal/cm3)0.5. The modified PR-EOS is found to be accurate for predicting the oil–CO2 phase behaviour. It is found that Δδ are almost equivalent at low pressures but with the pressure increase, Δδ at a larger pore radius becomes greater. The estimated MMPs are found to agree well with the measured MMPs from the coreflood and slim-tube tests in bulk phase and with the determined MMPs from the diminishing interface method in nanopores, whose average absolute relative deviations (AARD) are within 4.38% except for two abnormal cases. A smaller nanopore is found to contribute to the oil–gas solubility (i.e., a lower Δδ) and the MMP is also decreased with the pore radius. Moreover, the temperature increase and addition of CH4 into the oil and gas phases lead to a larger Δδ, which make the oil and gas phases become more difficult to be soluble so that the corresponding MMPs increase. On the contrary, the oil–gas solubility is beneficial from the addition of C2H6 into gas phase so that the MMP is reduced. Overall, the effects of temperature, initial oil and injection gas compositions on the MMP are found to be weakened in nanopores.
Nitrogen foam flooding is a promising technique for enhanced oil recovery, but instability of the foam limits its application. In this article, partially hydrophobic modified SiO2 nanoparticles with ...an anionic surfactant, sodium dodecyl sulfate (SDS), were used together to increase foam stability. Micromodel flooding and sandpack flooding were adopted to assess the stability and effect on enhanced oil recovery of the SiO2 stabilized foam (SiO2/SDS foam). The experimental data showed that the foam stability was decreased with an increase in temperature, while the foam volume was increased first and then decreased. SiO2/SDS foam showed better temperature tolerance than the SDS foam (foam stabilized by SDS) due to the adsorption of nanoparticles on the surface of the bubble. Almost all of the bubbles maintained spherical or ellipsoidal shape with prolonged time due to the enhanced surface dilational viscoelasticity, which was different from that of SDS foam. According to the micromodel flooding results, SiO2/SDS foam displaced more oil than brine flooding, SDS solution flooding, or SDS foam flooding. As the foam stability was enhanced, gas mobility and channeling were controlled effectively. In addition, more oil on the pore wall and in the dead-end pores was displaced out because of the higher viscoelasticity of the SiO2/SDS foam. The sandpack flooding results showed that the increase of differential pressure and profile control effect was a proportional function of the SiO2 concentration in SiO2/SDS foam. The test with a higher SiO2 concentration resulted in a higher oil recovery when SiO2 concentration was less than 1.5 wt %.
Geological CO2 storage is an emerging topic in energy and environmental community, which is, as a commonly accepted sense, considered as the most promising and powerful approach to mitigate the ...global carbon emissions during the transition to net‐zero. Of the geological media which initially considered cover the saline aquifers, oil and gas reservoirs, coal beds, and potentially basalts, up to now only the first two choices have been proven to be the most capable storage sites and successfully implemented at pilot/commercial scales. Here, two tandem papers propose novel strategies for the first time, by synthesizing and utilizing new high‐dryness CO2 foam, to enhance geological CO2 storage capacity in saline aquifer and oil and gas reservoirs. In this paper, a new high‐dryness CO2 foam is synthesized and injected into the saline aquifers to explore the storage capacity enhancement, with the unique foam‐induced advantages of sweep area expansion and storage efficiency improvement. Such a new idea is specifically evaluated and validated through a series of static analytical and dynamic performance experiments. With the optimum surfactant concentration of 0.5 wt%, the foaming volume and quality are determined to be 521 mL and 80.81%, respectively, which also shows excellent salt tolerance with 45,000 ppm Na+, 25,000 ppm Ca2+, and 25,000 ppm Mg2+. Moreover, the water consumption for CO2 storage decreases from 464.31 g/mol at 25% foam quality to 67.38 g/mol at 85% foam quality by using the new CO2 foam. Overall, the newly synthesized CO2 foam could effectively enhance geological CO2 storage capacity and concurrently diminish water consumption, therefore realizing the win‐win environment and economic benefits.
Plain Language Summary
Geological CO2 storage is an emerging topic in energy and environmental community, which is, as a commonly accepted sense, considered as the most promising and powerful approach to mitigate global carbon emissions amid the transition to net‐zero. The geological CO2 storage options initially included ocean storage, surface mineral carbonation, and geological storage, but currently only refer to the storage in geological media. Of the geological media which initially considered cover the saline aquifers, oil and gas reservoirs, coal beds, and potentially basalts, up to now only the first two choices have been proven to be the most capable storage sites and successfully implemented at pilot/commercial scales. Here, a paper proposes novel strategies for the first time, by synthesizing and utilizing new high‐dryness CO2 foam, to enhance geological CO2 storage capacity in saline aquifer and oil and gas reservoirs. Novel strategies, which effectively enhance geological CO2 storage capacity, are specifically evaluated and validated through a series of static analytical and dynamic performance experiments. Qualitative and quantitative analyses fill the knowledge gap or enhancing geological CO2 storage in saline aquifer and oil and gas reservoirs. Also, solid scientific analyses/supports are provided for future academic research and practical geological CO2 utilization and storage.
Key Points
Novel strategies for the first time, by synthesizing and utilizing new high‐dryness CO2 foam, to enhance geological CO2 storage capacity in saline aquifer
Qualitative and quantitative analyses fill the knowledge gap of enhancing the geological CO2 storage in saline aquifer
Solid scientific analyses/supports are provided for future academic research and practical geological CO2 utilization and storage
Global climate changes urge prompt energy transition for less carbon emissions, from traditional fossil fuels to renewable and sustainable clean energy. However, in reality, the world's energy ...majority cannot make U-turn immediately to renewables or clean energy due to the immature technology readiness, insufficient resource availability and unstable energy supply. In the next few decades, the fossil fuels, particularly oil and gas, will continue acting as the primary energy sector. Thus, instead of absolutely abandoning fossil fuel and seeking for impractical carbon mitigation technologies, to decarbonise the oil and gas will be definitely feasible and contribute more to net-zero transitions. This study, initially put eyes on the oil and gas decarbonization, critically reviewing the oil and gas resources, technologies, policies, and their futures toward net-zero. Basically, the status of oil and gas resources from different global regions, including the details of reserves, productions, consumptions, are summarized and analyzed. Moreover, the oil and gas technologies are categorized as gas, thermal and non-thermal, new recovery methods, each of which is specifically discussed in the applicable reservoir, mechanism, features and examples. Then, the global carbon emissions are reviewed in perspectives of emissions from fuel types and world regions as well as mitigations policies. Accordingly, the carbon mitigation approaches, specially in the oil and gas industry, are collected and listed from enterprise managements and technology renovations. Lastly, based on all the information and analyses and assisted with IEA energy outlook report, we provide a potential pathway for the oil and gas towards carbon neutral. This paper provides comprehensive overview on the oil and gas pathway to net-zero, which will not only technically guide the oil and gas decarbonisations, also be of interest to wide-range readers who are not experts but intend to understand the energy transitions.
•The first comprehensive overview on the oil and gas pathway to net-zero.•Oil and gas resources, technologies, policies, and their futures toward net-zero initially reviewed.•Solid qualitative and quantitative analyses fill the knowledge gap of oil and gas decarbonization.
In this paper, a generalized methodology has been developed to determine the diffusion coefficient of supercritical CO2 in cores that are saturated with different oil samples, under reservoir ...conditions. In theory, a mathematical model that combines Fick’s diffusion equation and the Peng-Robinson equation of state has been established to describe the mass transfer process. In experiments, the pressure decay method has been employed, and the CO2 diffusion coefficient can be determined once the experimental data match the computational result of the theoretical model. Six oil samples with different compositions (oil samples A to F) are introduced in this study, and the results show that the supercritical CO2 diffusion coefficient decreases gradually from oil samples A to F. The changing properties of oil can account for the decrease in the CO2 diffusion coefficient in two aspects. First, the increasing viscosity of oil slows down the speed of the mass transfer process. Second, the increase in the proportion of heavy components in oil enlarges the mass transfer resistance. According to the results of this work, a lower viscosity and lighter components of oil can facilitate the mass transfer process.
Abstract
Kelvin–Helmholtz (K-H) instability is a fundamental boundary instability between two fluids with different speeds, exchanging the mass, momentum, and energy across the boundary. Although the ...K-H instability has been suggested to play a critical role in atmospheric ion loss on Mars, the knowledge about its formation and evolution is still poor, due to the limitation of spacecraft missions and a dearth of dedicated simulation codes. In this study, we combine observations from the Mars Atmosphere and Volatile EvolutioN mission and global 3D kinetic simulations to investigate the solar wind–Mars interaction. For the first time, it is found that K-H waves prominently appear in the −E hemisphere, which is attributed to the stronger proton velocity shear therein associated with the asymmetric diamagnetic drift motion of protons. The K-H instability is mainly excited in the −E hemisphere and propagates downstream along the boundary, with the waves also able to be generated near the subsolar point. The K-H waves produce plasma clouds with a net oxygen ion escape rate of about 1.5 × 10
24
s
−1
, contributing to almost half of the global loss on present-day Mars. This heavy ion escape pattern associated with K-H instability is cyclic and could occur on other nonmagnetized planets, potentially influencing planetary atmosphere evolution and habitability.
We aimed to investigate how sulfur (S) application prior to oilseed rape cultivation influences the uptake of cadmium (Cd) by rice grown in low- and high-Cd soils. A pot experiment involving four S ...levels (0, 30, 60, 120 mg S kg−1) combined with two Cd rates (low and high—0.35 and 10.35 mg Cd kg−1, respectively) was conducted. Soil pore water during rice growth and plant tissues at maturity were analyzed. The soil pore water results indicated that S application decreased Cd solubility under submergence due to the S-induced increase of soil pH and the enhancement of sulfide formation in soil micropores. When S was applied at rates of 30, 60 and 120 mg S kg−1, brown rice Cd concentrations decreased by 18%, 18%, and 55% (p < 0.05) in the low-Cd soil but increased by 20%, 40%, and 40% in the high-Cd soil compared with those in the non-S treatment. The different effects of S on Cd accumulation in brown rice were related to Cd-induced oxidative stress in the rice plants. In low-Cd soils, a S-induced increase in phytochelatins in rice roots restricted and inhibited Cd translocation in brown rice. In high-Cd soils, the Cd-induced oxidative stress in rice plants weakened the protective effects of S, while highlighted the promotion of Cd uptake by S. Overall, S fertilizer is recommended for oilseed rape–rice rotations in low-Cd paddy fields. In high Cd-contaminated fields, oilseed rape–rice rotations are suitable for the simultaneous remediation by oilseed rape and production of rice without S fertilization.
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•In low-Cd soil, S fertilization prior to oilseed rape decreased brown rice-Cd.•S fertilizers are recommended for oilseed rape-rice cultivation in low-Cd soil.•In high-Cd soil, S fertilization prior to oilseed rape increased brown rice-Cd.•S fertilizers should be avoided in high-Cd soil with rape-remediation and rice-production simultaneously.
•New mathematical model from exergy analyses for HDRs heat extraction process by enclosed water recycling in horizontal well.•The accumulated exergy first gradually increases but decreases ...subsequently with the water rising flow rate.•The temperature distributions in the HDR around the wellbore are analyzed at different time.
In this paper, a novel mathematical model for the heat extraction process from hot dry rocks (HDRs) by enclosed water recycling in a horizontal well is established, on a basis of which a series of exergy analyses are conducted. The pressure and temperature distributions in the wellbore and the exergy extracted under different working conditions are calculated. Eight factors are specifically studied to evaluate their effects on the accumulated exergy of the produced hot water. It is found that the accumulated exergy first gradually increases but decreases subsequently with the water rising flow rate. The accumulated exergy is noticed to increase obviously with the increase of the length for the horizontal section, temperature of the HDR, thermal conductivity of the HDR, and diameter of the casing. The temperature distributions in the HDR around the wellbore are analyzed at different time. More specifically, the temperature drop of the HDR gradually spreads to far area of the wellbore with the continuous extraction of geothermal energy. The temperature of the rock around the wellbore decreases by increasing the injection rate. A higher HDR thermal conductivity leads to a quick heat transfer from the remote to near wellbore area. The exergy analyses in this study provide strong theoretical supports to utilize the HDR heat extraction.
The open-cut tunnels in Aixi Lake, Nanchang, are constructed in a condominium form of highway tunnel and subway tunnel, which are the first superimposed double-level tunnels in China. The scientific ...problems faced by this new structure form have attracted the attention of engineers and researchers. If this structure form can be reasonably used, it can reduce the repeated excavation of the ground and reduce the impact of highway tunnel construction on subway tunnels. It is of great guiding significance to study the influence of the spacing between lower double-track subway tunnels on the stress and deformation characteristics of the upper highway tunnel. Based on the model test, the deformation, axial force, bending moment, and earth pressure of the upper highway tunnel are studied. The results show that the maximum displacement of upper tunnel floor can be reduced by 30% when the spacing of the lower tunnel makes the center line of the lower single tunnel coincide with the quadripartite line of the upper tunnel. Horizontal spacing between lower double-track tunnels significantly influences the bending moment of upper tunnel floor but hardly influences the axial force of the upper tunnel floor. Considering the influence of lower tunnel spacing on the earth pressure of the upper tunnel floor, the spacing of the lower tunnel should not exceed 50% of the section width of the upper tunnel.
Foam is a kind of ideal fluid for profile control in petroleum engineering, which has attracted intense interests of scholars globally in recent years. In this study, a foam system stabilized with ...anionic surfactants and clay particles was proposed for profile control in reservoirs, and the formulation was optimized experimentally. Moreover, flooding experiments in visible porous media models and in sandpacks were conducted to test the plugging effect of the foam system on reservoirs, and the effects of different factors such as gas–liquid ratio, temperature and permeability on profile control were also evaluated. According to the experimental results, the clay-HY-2 system was elected for its satisfactory foamability, stability, and salinity resistance, and the optimum concentrations of HY-2 and clay particle are 0.6 wt% and 5.0 wt%, respectively. Compared with traditional foam fluids, the clay-HY-2 system can form denser and smaller bubbles in high- and middle-permeable layers, enhancing the plugging effect there, while there are less bubbles in low-permeable layers, i.e., the restriction on the flow in narrow structures is slight. The clay-HY-2 foam can perform the efficient and uniform profile control effect on sandpacks when the foam quality is around 50%. The resistance factor of the foam decrease gradually with the increasing temperature, however, the resistance factor remains higher than 350.0 when the temperature reaches 80.0 °C. When the permeability exceeds 1502.0 mD, the clay-HY-2 foam can perform deep profile control in reservoirs, and the resistance factor are not sensitive to the change of permeability when it exceeds 3038.0 mD. Besides, the site application case shows that the clay-HY-2 foam do have good profile control effect on reservoirs, i.e., improving oil production and declining water cut.
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