Abstract

The hydrate reservoir in Shenhu area is a complex, multilayered system and the production strategy of the target layer is the key to long-term efficient exploitation. According to available geological data, we used numerical simulation to analyze three cases of gas production in different layers by using the depressurization method with vertical wells. The production behaviors and evolutions of pressure, temperature, gas, and hydrate saturation were analyzed. The results showed that the depressurization rate was limited by the low permeability. For 10 years of production, the production case in the free-gas layer could obtain the largest cumulative gas production, and hydrate dissociation could obtain stable gas production.

Abstract

Oxy-fuel combustion (OFC) is a promising technology for Carbon Capturing and Storage (CCS) in power generation systems. This work presents a mathematical model to predict relevant gas engine parameters for combined heat and power application. Different oxidizer blends (O2 + CO2) for the combustion of refuse-derived fuel pyrolysis gas were tested. Numerical predictions showed that oxy-fuel combustion of RDF pyrolysis gas in power engines did not penalize system thermal efficiency. The exhaust gas temperature and heat content suit combined heat and power plants under zero emissions operation.

Abstract

The use of a fully renewable energy system (RES) to power mid- and low-scale off-grid systems is an attractive alternative solution to replace fossil fuel technologies in order to meet the ever-growing demand and tackle environmental problems. In this study, the design optimization of a hybrid solar biogas, Organic Rankine Cycle (ORC-Toluene) and Air Gap Membrane Distillation (AGMD) for desalination and electric power generation is presented. Three objective functions namely, maximizing power and water production, and minimizing the unit exergy product costs has been formulated. The turbine efficiency, top ORC vapor temperature and ORC condenser temperature has been selected as the decision variables. The non-dominated sorting genetic algorithm (NSGA-II) has been employed to solve the optimization problem and produce a Pareto frontier of the optimal solutions. Further, the TOPSIS approach has been used to select the optimal solution from the Pareto set. The study constitutes the first attempt to holistically optimize such a hybrid off-grid cogeneration system in a robust manner. It is found that the proposed system is capable of generating 1960 kW of electricity and 8 𝑘𝑔𝑚2ℎ⁄ freshwater with 11 $/GJ unit exergy product costs.

Abstract

In previous work, we proposed an integrated system of solid oxide fuel cells (SOFCs) and thermally self-sustained methane steam reformer (TS-MSR) and conducted the corresponding thermo-electro-chemo-mechanical behavior evaluation of SOFCs considering pre-reformer designs. While this work aims to conduct the thermo-chemo-mechanical behavior evaluation of TS-MSR when micro-channel technology is employed. The results indicate the application of microchannel technology facilitates the mass transfer within the TS-MSR and the resulting lower temperature improves the thermal strain stress behavior. This study can provide a reference for the design and thermomechanical evaluation of the integrated system before commercialization.

Abstract

Facing the water-injection difficulty and low oil recovery in ultra-low permeability reservoirs, single-well water injection-production (SWWIP), which transforms water injection between different wells to between horizontal-well fracture stages, was recently proposed as an innovative water-injection approach for EOR. However, SWWIP under some well patterns could cause even worse production performance in development applications. Therefore, this work conducts an adaptability study of SWWIP under common well patterns and aims to find suitable patterns for carrying out SWWIP. We summarized three kinds of SWWIP modes based on the reported work. An industry-standard reservoir simulator (CMG-IMEX) is used to simulate the production of three modes under five kinds of well patterns, including five-spot, rhombus five-spot, seven-spot, staggered seven-spot and nine-spot patterns. Under the same well pattern, we first compared oil recovery of different SWWIP modes and conventional injection-production mode to find the best/worst modes. Then, based on the best mode, we compared oil recovery of different well patterns to find the optimal pattern. The results show that the average oil recoveries of mode 1,2,3 and the conventional injection-production mode under five kinds of well patterns are 13.9%, 9.7%, 17.9%, and 12.9%, respectively. Mode 3 is optimal to improve oil recovery. It is demonstrated that the oil recoveries of mode 1 under staggered seven-spot and nine-spot patterns and mode 2 under rhombus five-point, seven-spot, staggered seven-spot and nine-spot patterns are generally lower than conventional injection-production mode. Therefore, mode 1 under staggered seven-spot and nine-spot patterns and mode 2 under rhombus five-point, seven-spot, staggered seven-spot and nine-spot patterns are not suitable for development operation. The results also show that the mode 3 under seven-spot pattern can obtain the highest oil recovery with the same water injection.

Abstract

Enhanced Geothermal System (EGS) is now the main method to extract heat from the hot dry rock, and the fractures are the key to achieving a high heat extraction. This paper extends the related transmissibility calculation method of non-neighboring connections (NNC) in the projection-based embedded discrete fracture model (pEDFM) to the calculation of effective thermal transmissibility. In this way, a thermal pEDFM is proposed to evaluate the heat extraction performance of the fractured EGS. The model verification is conducted by comparing the result of the thermal pEDFM and the analytical solution. At last, two simulation examples are utilized to illustrate the flexibility and the practicality of the thermal pEDFM, which reveals that the thermal pEDFM can be applied in the evaluation of the heat extraction analysis for the fractured EGS.

Abstract

Estimating the state-of-charge of battery packs is more important than that of single cells in electric vehicles. This paper proposes a battery pack model to estimate the SOC of a series-parallel battery pack for electric vehicles, which integrates the difference model and the mean model. To verify the performance of the model, we use the model to estimate the SOC of a 12-series-3-parallel (12S3P) battery pack under dynamic conditions, the results show that the maximum error of the battery pack SOC estimation is 0.005.

Abstract

The emission footprint of blue hydrogen production varies in literature, resulting in opposing recommendations on its eligibility in a carbon-neutral energy system. Next to fugitive methane emissions and global warming potential, the assumptions regarding carbon capture (CC) can significantly influence results. This analysis reviews these assumptions of several recently published blue hydrogen studies and compares them to experiences with CC in practice. It is found that the impact of various CC modelling parameters on emission footprints requires using real-world data in emission accounting. It is necessary to establish a concise emission accounting methodology for CC to increase transparency for stakeholders on blue hydrogen emissions.

Abstract

Seabed methane seeping is widespread around the world, affecting the ocean and the global carbon cycle. Natural gas hydrate (NGH) is an important physical way to have leaked CH4 sequestration. Hydrate formation kinetics is one of the key factors affecting methane capture efficiency. Varied dissolved CH4 concentrations due to different methane flux differences may affect the kinetic characteristics of hydrate formation, which is necessary to be unveiled. In this work, the effect of initial dissolved CH4 concentration on hydrate formation in static system was investigated by constructing different CH4 leakage flux conditions in simulated “Haima” cold spring environment. The experimental results showed that the increase of initial dissolved CH4 concentration accelerated hydrate formation, while the obvious promoting effect may depend on the higher dissolved CH4 concentration. Morphology experiments showed that under the condition of relatively high concentration of dissolved CH4, a large number of flocculent hydrates formed in the liquid phase, and induced the growth of CH4 hydrate toward the liquid phase. Combined with CH4 gas consumption analysis, it is believed that this phenomenon was related to the formation of porous CH4 hydrate. The results obtained in this study have important reference significance for understanding the mechanism of hydrate formation and evolution in the CH4 seeping environment.

Abstract

To obtain sustainable economical oil production and recovery of investment, commingling production has been widely used in multi-layer oil reservoirs. However, the characteristics of oil-water flow in porous media have long been neglected, making variations in multi-layer co-production (MLCP) difficult to anticipate. This paper concentrates on complex seepage and pore throat characterizations, as well as the construction of a prediction model capable of monitoring the dynamic behavior of MLCP in microscopically variable porous media. More specifically, high-pressure mercury injection (HPMI) and nuclear magnetic resonance (NMR) were used to characterize pore throat sizes and distributions, and a capillary bundle model was used to assess water displacement seepage resistance. In the process of continuous water parallel displacement, the changes in seepage resistance induced by throat altering and coupling boundary layer effects were especially explored. As a consequence, using the time-node analysis approach, a thorough mathematical model was built and confirmed by comparing experimental results. With errors of 3.94 % and 1.62 %, the projected oil recovery and water cut from the created model are in excellent agreement with actual findings.