Injection Strategy Research Articles

Numerical Simulation of the Dynamic Behavior of Low Permeability Reservoirs Under Fracturing-Flooding Based on a Dual-Porous and Dual-Permeable Media Model

In recent years, fracturing-flooding technology has achieved a series of successful practices in the development of low-permeability oil reservoirs. However, research on the dynamic behavior of fracturing-flooding remains limited. In this paper, a dual medium model considering anisotropic characteristics is established for the target blocks. Multiple sets of conventional water injection transitions and multi-cycle fracturing-flooding operations are designed for simulation to explore the subsequent optimal operational schemes. Simulations are conducted on the optimal transitions between conventional water injection and multi-cycle fracturing-flooding schemes for different reservoir models with varying physical properties to study the dynamic behavior of fracturing-flooding in oil reservoirs with different properties. The results indicate that, for conventional water injection schemes, the optimal transition time for both the target well group and other reservoirs with different properties corresponds to a formation pressure coefficient between 1.2 and 1.3, with the optimal injection–production ratio being 1:1. From the perspective of water cut, the accumulated oil production of multi-cycle fracturing-flooding is higher than that of conventional water injection. The optimal multi-cycle fracturing-flooding schemes for both the target well group and other reservoirs with different properties are to start fracturing-flooding when the formation pressure coefficient is around 0.8 and to begin production when it reaches 1.4.

A Numerical Simulation of Mixture Formation in a Hydrogen Direct-Injection Internal Combustion Engine

Direct-injection technology applied in hydrogen internal combustion engines can effectively prevent backfire, thereby improving the engine performance. Nonetheless, optimizing the injection strategy is highly intricate, requiring a comprehensive understanding of the hydrogen–air mixture formation process inside the cylinder. In this study, a simulation of hydrogen–air mixture formation was systematically conducted in a hydrogen direct-injection internal combustion engine using three-dimensional computational fluid dynamics (CFD) software. Under rated conditions, the influence of the nozzle hole number, injection direction, injection timing, and combustion chamber geometry on the mixture formation was analyzed from the perspectives of flow state and mass transfer. The results indicate that more nozzle holes would lead to more significant non-uniformity of the mixture, mainly due to the Coanda effect. The normalized standard deviation (NSD) of a six-hole nozzle design is 0.3495, which is higher than the NSD of all the single-hole nozzle conditions. By changing the hydrogen injection timing from −144 °CA to −136 °CA, the non-uniformity coefficient of the mixture is little affected, while notable differences in the distribution of the mixture are observed. The appropriate injection directions and optimized combustion chamber geometries could also help to effectively organize the in-cylinder flow, significantly improving the uniformity of the in-cylinder mixture and reducing the likelihood of abnormal combustion events.

Assessing GFDL‐ESM4.1 Climate Responses to a Stratospheric Aerosol Injection Strategy Intended to Avoid Overshoot 2.0°C Warming

AbstractIn this work, we apply the GFDL Earth System Model (GFDL‐ESM4.1) to explore the climate responses to a stratospheric aerosol injection (SAI) scenario that aims to restrict global warming to 2.0°C above pre‐industrial levels (1850–1900) under the CMIP6 overshoot scenario (SSP5‐34‐OS). Simulations of this SAI scenario with the CESM Whole Atmosphere Community Climate Model (CESM2‐WACCM6) showed nearly unchanged interhemispheric and pole‐to‐Equator surface temperature gradients relative to present‐day conditions around 2020, and reduced global impacts, such as heatwaves, sea ice melting, and shifting precipitation patterns (Tilmes et al., 2020, https://doi.org/10.5194/esd‐11‐579‐2020). However, model structural uncertainties can lead to varying climate projections under the same forcing. Implementing identical stratospheric aerosol radiative properties in GFDL‐ESM4.1, which has a much lower Effective Climate Sensitivity compared to CESM2‐WACCM6, resulted in a decrease in global‐mean surface temperature by more than 1.5°C and a corresponding reduction in precipitation responses. Two major reasons contribute to the different temperature response between the two models: first, GFDL‐ESM4.1 has less warming in the SSP534‐OS scenario; second, GFDL‐ESM4.1 has shown more pronounced cooling in response to the same stratospheric AOD perturbation. Notably, the Southern Hemisphere experiences substantial cooling compared to the Northern Hemisphere, accompanied by a northward shift of the Intertropical Convergence Zone (ITCZ). Furthermore, our analysis reveals that spatially heterogeneous forcing within the SAI scenario results in diverse climate feedback parameters in the GFDL‐ESM4.1 model, through varying surface warming/cooling patterns. This research highlights the importance of considering model structural uncertainties and forcing spatial patterns for a comprehensive evaluation of future scenarios and geoengineering strategies.

Revealing the NO Formation Kinetics for NH3/CH4 Blends Under Dual-Flame and Premixed Swirl Flame Configurations

Ammonia stands out as a promising zero-carbon fuel and an efficient hydrogen carrier, offering great promise for industrial applications in gas turbines and boilers. However, different combustion modes significantly influence the flame structure and combustion characteristics of ammonia. In this study, two distinct fuel injection strategies were employed in a model combustor: ammonia and methane, under fully premixed and dual-flame combustion modes. Numerical simulations were performed to analyze the flame structure, velocity fields, and temperature distribution, complemented by planar flow field, flame OH* chemiluminescence, and NO emission measurements. Findings reveal that with an increasing NH3 ratio, the flame front becomes more elongated with more pronounced temperature fluctuations at the swirler exit. Particularly, at 50% NH3, a significant reduction in flame temperature is observed, notably at a height of 30 mm from the burner. For dual flames, the reaction NH2 + O ↔ HNO + H was less significant compared to its effect in premixed flames, whereas the H + O2 ↔ O + OH reaction demonstrated the highest sensitivity coefficient. An increase in the NH3 ratio correspondingly led to a reduction in NO consumption reaction rates, heightening the sensitivity coefficient for NO inhibition, and providing critical insights into ammonia combustion optimization.

Combustion and Emission Characteristics of Methanol–Diesel Dual Fuel Engine at Different Altitudes

Currently, in the two technological approaches for using diesel pilot injection to ignite methanol and partially substituting diesel fuel with methanol, neither can fully achieve carbon neutrality in the context of internal combustion engines. Compression-ignition direct-injection methanol marine engines exhibit significant application potential because of their superior fuel economy and lower carbon emissions. However, the low cetane number of methanol, coupled with its high ignition temperature and latent heat of vaporization, poses challenges, especially amidst increasingly stringent marine emission regulations. It is imperative to comprehensively explore the impacts of the engine geometry, intake boundary conditions, and injection strategies on the engine performance. This paper first investigates the influence of the compression ratio on the engine performance, subsequently analyzes the effects of intake conditions on methanol ignition characteristics, and finally compares the combustion characteristics of the engine under different fuel injection timings. When the compression ratio is set at 13.5, only an injection timing of −30 °CA can initiate methanol compression ignition, but the combustion is not ideal. For compression ratios of 15.5 and 17.5, all the injection timings studied can ignite methanol. Reasonable increases in the intake pressure and intake temperature are beneficial for methanol compression ignition. However, when the intake temperature rises from 400 K to 500 K, a decrease in the thermal efficiency is observed. Particularly, at an injection timing of −30 °CA, both the peak cylinder pressure and peak cylinder temperature are higher, the ignition occurs earlier, the combustion process shifts forward, and the combustion efficiency and indicated thermal efficiency are at higher levels. Furthermore, the overall emissions of NOX, HC, and CO are relatively low. Therefore, selecting an appropriate injection timing is crucial to facilitate the compression ignition and combustion of methanol under low-load conditions.

Impact of beam asymmetries at the Future Circular Collider e+e−

In this paper, we present detailed simulations with asymmetric initial beam settings in the context of the proposed Future Circular Collider e+e− (FCC-ee) using the framework. We compare simulated equilibrium bunch sizes and luminosities against an already existing analytical model, which shows remarkably good agreement for realistic small perturbations. We investigate the longitudinal top-up injection, the currently preferred injection scheme for the FCC-ee, using self-consistent simulations featuring beam-beam collisions with beamstrahlung and the injection process for the first time. We present and assess the sensitivity and required precision of the nominal beam parameters in a potential real-life operation by providing first estimates of the tolerances in the initial asymmetry of several machine parameters, with respect to the 3D flip-flop mechanism, obtained from parameter scan simulations. Published by the American Physical Society 2024

Investigation of oil-based CO2 foam EOR and carbon mitigation in a 2D visualization physical model: Effects of different injection strategies

CO2 flooding in low-permeability and tight oil reservoirs often encounters gas channeling, which affects oil recovery. To address this, oil-based CO2 foam development is explored using a two-dimensional visual physical model. The study includes three experimental setups: CO2 flooding followed by oil-based CO2 foam flooding, CO2 Huff-n-Puff (HnP) followed by oil-based CO2 foam HnP, and oil-based CO2 foam HnP followed by oil-based CO2 foam flooding. Findings reveal that using oil-based CO2 foam after CO2 development increases recovery factors by 15.62% and 35.86% for HnP and flooding, respectively, and significantly boosts CO2 storage. The CO2 storage is 1.96 times and 6.03 times higher than the initial one. After oil-based CO2 foam is used, the red area near the outlet of the visualization model becomes shallower, indicating a further decrease in residual oil saturation. The oil-based CO2 foam method reduces residual oil saturation and extends production duration while decreasing gas production rates. This approach effectively plugs gas channels, enhancing CO2 sweep efficiency, crude oil mobility, and recovery. The results provide innovative strategies for oilfield development, supporting carbon sequestration and offering substantial economic and environmental benefits.

Power increase potential of coal-fired power plant assisted by the heat release of the thermal energy storage system: Restrictions and thermodynamic performance

The integration of a thermal energy storage (TES) system is an effective way to improve the load cycling rate of coal-fired power plants (CFPPs). To evaluate the power increase potential and thermodynamic performance of CFPP supplied by heat release of the molten salt TES system, eight discharging modes for CFPP integrated with the TES system including steam injection, heater bypass, and additional turbine schemes were comparatively evaluated. The system simulation models of the integrated systems were developed and the thermodynamic performance of the proposed system were evaluated. Results show that the mode SI-HPT (high-pressure turbine steam injection) has the largest output power increase of 25.00 % under the benchmark condition of 75%THA, but the mode HB-LPH (low-pressure heater bypass) shows a very low output power increase of 2.08 %. Moreover, the power generation efficiency is changed by the external heat source through a change in the average heat absorption temperature of the Rankine cycle and the internal irreversibility of the steam/water cycle. Under the typical benchmark discharging condition of 75%THA, the power generation efficiency of the turbine in mode SI-LPT (low-pressure turbine steam injection) can be reduced from 47.41 % to 44.15 %, but it can be increased from 47.41 % to 48.86 % in mode SI-HPT. When the temperature ranges of the TES system are above 600 °C and below 450 °C, the modes SI-HPT and SI-LPT obtain the optimal comprehensive performance, respectively. This study can provide the scientific guidance for retrofit for CFPP to achieve efficient and flexible design.

Hydrogen injection and withdrawal performance in depleted gas reservoirs

Residual gas trapping in porous media is a key indicator of hydrogen storage and recovery performance. The injection scheme of cushion and working gases helps maintain pressure and reduce losses. However, this information is limited in the literature. This work explores core flooding experiments (using electrical resistivity for in-situ saturation monitoring) on Bandera Grey sandstones under reservoir conditions (42 °C, 1400 psi, and 5 wt% NaCl), investigating cushion gas type and injection rate effects on storage and recovery performance. Results indicate that CO2 injection ahead of hydrogen yielded the highest storage capacity with Sgi=0.255, then CH4: Sgi=0.226 and finally, N2: Sgi=0.216. At lower injection rates (0.2–0.6 cc/min), CH4 cushion gas exhibited the highest recovery (42%), whereas at higher injection rates (1.2–10 cc/min), CO2 resulted in the highest, with 33%. These findings emphasize cushion gas's role in enhancing hydrogen storage capacity and production efficiency in depleted gas reservoirs.

A study on optical diagnostics and numerical simulation of dual fuel combustion using ammonia and n-heptane

As a zero-carbon fuel, ammonia is considered an ideal alternative for reducing carbon footprints. However, the use of pure ammonia is limited by its poor fuel properties, which can be mitigated by employing a dual fuel approach using high reactivity fuel and ammonia. Nonetheless, the evolution mechanisms of nitrogen oxides (NOx) and unburned ammonia (NH3) remain unclear. In this study, n-heptane was selected as the high-reactivity fuel. The characteristics of the dual fuel approach and the evolution mechanisms of NOx and unburned NH3 were investigated using optical diagnostics and numerical simulations, respectively. The results indicate that the combustion characteristics can be improved by adjusting the direct injection strategy. Unconsumed NH3 remains in the low-temperature regions of the late period of combustion, resulting in unburned NH3 emissions. The consumption of unburned NH3 is governed by the reaction NH3 + OH <=> H2O + NH2. The distribution of N2O is primarily concentrated in low-temperature regions. The generation of N2O is controlled by the reaction NH + NO <=> H + N2O. The improvement of the in-cylinder temperature can suppress the generation of N2O and promote the consumption of NH3, resulting in reduced emissions of both N2O and unburned NH3.

Influence mechanism and optimization of the diesel engine jet disturbance chamber injection strategy for enhanced combustion and thermal efficiency

Influence mechanism and optimization of the diesel engine jet disturbance chamber injection strategy for enhanced combustion and thermal efficiency

Study of Fuel Injection Strategy for a Methanol and Diesel Dual-Fuel Large-Bore and Medium-Speed Marine Engine

Study of Fuel Injection Strategy for a Methanol and Diesel Dual-Fuel Large-Bore and Medium-Speed Marine Engine

Overview of Typical Projects for Geological Storage of CO2 in Offshore Saline Aquifers

With the continuous growth of global energy demand, greenhouse gas emissions are also rising, leading to serious challenges posed by climate change. Carbon Capture, Utilization, and Storage (CCUS) technology is considered one of the key pathways to mitigate climate change. Among the CCUS technologies, CO2 storage in offshore saline aquifers has gained significant attention in recent years. This paper conducts an in-depth analysis of the Sleipner and Snøhvit projects in Norway and the Tomakomai project in Japan, exploring key issues related to the application, geological characteristics, injection strategies, monitoring systems, and simulation methods of CO2 storage in offshore saline aquifers. This study finds that CO2 storage in offshore saline aquifers has high safety and storage potential but faces several challenges in practical applications, such as geological reservoir characteristics, technological innovation, operational costs, and social acceptance. Therefore, it is necessary to further strengthen technological innovation and policy support to promote the development and application of CO2 storage in offshore saline aquifers. This study provides valuable experiences and insights for similar projects worldwide, contributing to the sustainable development of CO2 storage in offshore saline aquifers and making a greater contribution to achieving global net-zero emission targets.

Chemical kinetics of Lean − Rich − Lean fuel-air staged NH3/H2-air combustion for emission control

Ammonia has garnered considerable attention among researchers as a carbon–neutral fuel option. Addressing the challenge of its inherently slow combustion kinetics, significant research efforts have been directed toward mitigating NOx emissions, which represents a critical hurdle in advancing the commercial viability of ammonia as a sustainable fuel. The rich-lean combustion approach has been advocated and demonstrated as the primary means to keep NOX within acceptable emission limits. However, in the current study, a distributed fuel and air injection strategy is proposed and investigated as a superior alternative compared to the traditional rich-lean method for NOX reduction for NH3/H2-air mixtures with higher ammonia fuel fraction (XNH3 = 50 − 90 %). The proposed lean-rich-lean strategy with multi-staging of fuel and air supply is achieved by injecting NH3-air mixtures into H2-air combustion products followed by a downstream supply of preheated dilution air. Such an injection strategy manages the surge of NHi and O/H radicals while avoiding local temperature peaks by implementing a two-stage ignition pattern of NH3/H2 blends combustion in series. NOX reductions of approximately 48 % and 7 % forXNH3 = 50 % and 70 %, respectively, is achieved with the lean-rich-lean combustion strategy compared to the rich-lean strategy over a wide range of global equivalence ratios(ϕG = 0.3 to 0.7). The lean-rich-lean combustion strategy for atmospheric NH3/H2-air swirl flames, when integrated with advanced SCR technology, is anticipated to demonstrate a viable approach to achieving zero carbon and low NOX emissions in industrial applications.

Experimental and Numerical Simulation Studies on the Synergistic Design of Gas Injection and Extraction Reservoirs of Condensate Gas Reservoir-Based Underground Gas Storage

The natural gas industry has developed rapidly in recent years, with gas storage playing an important role in regulating winter and summer gas consumption and ensuring energy security. The Ke7010 sand body is a typical edge water condensate gas reservoir with an oil ring, and the construction of gas storage has been started. In order to clarify the feasibility of synergistic storage building for gas injection and production, the fluid characteristics during the synergistic reservoir building process were investigated through several rounds of drive-by experiments. The results show that the oil-phase flow capacity is improved by increasing the number of oil–water interdrives, and the injection and recovery capacity is improved by increasing the number of oil–gas interdrives; the reservoir capacities of the high-permeability and low-permeability rock samples increase by about 4.84% and 7.26%, respectively, after multiple rounds of driving. Meanwhile, a numerical model of the study area was established to simulate the synergistic storage construction scheme of gas injection and extraction, and the reservoir capacity was increased by 7.02% at the end of the simulation period, which was in line with the experimental results. This study may provide a reference for gas storage construction in the study area.

SNA·SMNP·CBE system: A novel integrative strategy for β-hemoglobinopathies gene therapy

Here, we developed and demonstrated a novel integrative system—Silica Nanorods (SNA) substrate cell capture combined with Supramolecular Nanoparticle (SMNP) delivery mediated CBE base editing (SNA·SMNP·CBE)—achieving the synchronization of CD34+HSPCs cell capture and gene editing for β-hemoglobinopathies. First, in vitro study shows it enables efficient and precise modification of BCL11A promoter in CD34+HSPCs, yielding the highly editing efficiency of 50.4 %, thus making an alternative strategy to conventional immunomagnetic cell separation and electroporation transfection system mediated CBE editing (IMS·EP·CBE). Then, we transplanted the edited human CD34+HSPCs into severe combined immunodeficiency (SCID) mice by using intraosseous injection strategy. When compared with conventional IMS·EP·CBE methods, our results showed that significantly higher human HBG expression in the bone marrow and peripheral blood of recipient mice, and long-term engraftment, evidenced from similar gene expression profiles to naïve CD34+HSPCs at 14 weeks. Conclusively, our integrative system—SNA·SMNP·CBE·intraosseous injection—offers an appealing novel way for the unique potential of gene therapy in the clinic application for β-hemoglobinopathies patients.

Separate-Layer Injection Scheme Optimization Based on Integrated Injection Information With Artificial Neural Network and Residual Network

Abstract Separate-layer injection technology is a highly significant approach for enhancing oil recovery in the later stages of oilfield production. Both separate-layer and general injection information are crucial parameters in multi-layer oilfield injection systems. However, the significance of general injection information is usually overlooked during the optimization process of separate-layer injection. Moreover, conventional optimization schemes for separate-layer injection fail to meet the immediate and dynamic demands of well production. Consequently, a separate-layer injection optimization method based on artificial neural network and residual network (ANN-Res) model was proposed. Firstly, the primary controlling factors for production were identified through grey correlation analysis and ablation experiments. Then, a data-driven model was established with an artificial neural network (ANN), in which the residual block was utilized to incorporate general injection information, eventually forming an ANN-Res model that integrates separate-layer and general injection information. Finally, a workflow for separate-layer injection optimization was designed in association with the ANN-Res model. Analysis of primary controlling factor for production shows that the combination of separate-layer and general injection information for production prediction leads to redundancy. The results of injection–production prediction demonstrate that the ANN-Res model is significantly better than that of the ANN model which only inputs separate-layer or general injection information. Furthermore, the result of optimization proves the proposed method can be successfully applied to injection optimization, realizing the purpose of increasing oil production and decreasing water cuts, thereby improving oilfield development.

Effects of Scavenging-Port Semi-Direct Injection Strategy on Mixture Formation for a Two-stroke Spark Ignition Kerosene Piston Engine

Abstract The two-stroke spark ignition (SI) kerosene piston engines (KPE) are commonly utilized in lightweight unmanned aerial vehicles (UAV). The quality of mixture formation is crucial for the engine performance. This paper investigates the mixture quality in a semi-direct injection (SDI) SI KPE. Computational models were established using a 1D simulation tool and a 3D computational platform to analyze the effects of injection pressure, injection timing, and fuel temperature on atomization and mixture formation. The results indicate that increasing injection pressure promotes a more uniform mixture distribution. Higher injection pressures also enhance the formation of fuel film. At the top dead center (TDC), the average equivalence ratio (ER) with an injection pressure of 0.7 MPa is 3.8% higher than that of 0.3 MPa and 1.9% lower than that of 0.5 MPa. Delaying the injection timing increases the pressure difference between the cylinder and scavenging port, weakening fuel penetration and improving the fuel gasification rate. When the injection timing is set to 180 °CA ATDC, the average ER at TDC is 10.4% higher than that at 140 °CA ATDC, with a 6.6% decrease in fuel capture rate. Increasing fuel temperature effectively enhances the fuel gasification rate. However, excessively higher fuel temperatures will not significantly improve mixture quality. At a fuel temperature of 380 K, the average ER at TDC is 2.9% higher than that at 340 K. Response surface analysis reveals that the control parameters affect the average ERs in the following order of influence: injection timing, fuel temperature, and injection pressure. This study provides theoretical support for optimizing control parameters in SDI SI KPEs.

Exploring Hydrogen–Diesel Dual Fuel Combustion in a Light-Duty Engine: A Numerical Investigation

Dual fuel combustion has gained attention as a cost-effective solution for reducing the pollutant emissions of internal combustion engines. The typical approach is combining a conventional high-reactivity fossil fuel (diesel fuel) with a sustainable low-reactivity fuel, such as bio-methane, ethanol, or green hydrogen. The last one is particularly interesting, as in theory it produces only water and NOx when it burns. However, integrating hydrogen into stock diesel engines is far from trivial due to a number of theoretical and practical challenges, mainly related to the control of combustion at different loads and speeds. The use of 3D-CFD simulation, supported by experimental data, appears to be the most effective way to address these issues. This study investigates the hydrogen-diesel dual fuel concept implemented with minimum modifications in a light-duty diesel engine (2.8 L, 4-cylinder, direct injection with common rail), considering two operating points representing typical partial and full load conditions for a light commercial vehicle or an industrial engine. The numerical analysis explores the effects of progressively replacing diesel fuel with hydrogen, up to 80% of the total energy input. The goal is to assess how this substitution affects engine performance and combustion characteristics. The results show that a moderate hydrogen substitution improves brake thermal efficiency, while higher substitution rates present quite a severe challenge. To address these issues, the diesel fuel injection strategy is optimized under dual fuel operation. The research findings are promising, but they also indicate that further investigations are needed at high hydrogen substitution rates in order to exploit the potential of the concept.

Reductions in GHG and unburned ammonia of the pilot diesel-ignited ammonia engines by diesel injection strategies

How to reduce the exhaust NH3 and N2O emissions is very crucial for bridging the gap between the high greenhouse gas (GHG) reduction potential and the engineering application of ammonia engines with high ammonia energetic ratios (AER). In this study, experiments were conducted to explore how the diesel injection pressures and the split injections affect the characteristics of combustion, emissions, and thermal efficiency for the AER of 80 % in a LPDF (i.e., low-pressure injection ammonia-diesel dual-fuel) engine. As for the split injections, both the early first injection during the compression stroke and the postponed second injection after the top dead center (TDC) were detailed investigated. With the injection pressure of the pilot diesel increasing from 60 to 150 MPa, about 28 % reductions in the unburned NH3 and about 13 % reductions in the N2O are achieved. With the optimized split injections before the TDC, about 11 % reductions in the unburned NH3, 13 % reductions in N2O, and 1.1 % enhancements of the indicated thermal efficiency can be simultaneously achieved. For the split injections with the second injection after TDC, the exhaust temperature can be to some degree increased but result in more NH3 and N2O, alongside a decline in thermal efficiency. Numerical simulations show that the diesel spray targeting and mixture reactivity stratification can explain the mechanism behind the improved performance of the optimized split injections, suggesting the potential for further improvement by the co-optimization of diesel injection strategy and combustion chamber geometry for the LPDF operations with high AERs.