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Hydraulic fracturing is typically required before shale gas production. Residual fracturing fluid in the reservoir leads to a hydration reaction and weakens the fracturing effect. To address these problems, an additional process during the reservoir heat treatment at the time point after hydraulic fracturing and before formal extraction is proposed, namely, heat treatment after shale gas reservoir hydraulic fracturing, and analysis of the Sichuan Longmaxi Shale is used as an example. The feasibility of the method has been demonstrated by observing the changes in porosity, permeability, tensile strength and other parameters of hydrated shale after heating and exploring the influencing factors and change laws associated with each parameter. Experiments can be conducted to verify that after heating the hydrated shale, the heating temperature, heating rate and holding time are positively correlated with shale porosity, permeability and tensile strength. After shale hydration, the elastic modulus, yield limit and compressive strength decrease; after hydrated shale heat treatment, the compressive strength decreases slightly, while the elastic modulus and yield limit increase, but they are lower than those of the original shale. The changes in the parameters have a positive effect on shale gas production, and this method is theoretically feasible. • This paper proposes a new method of reservoir modification. • This method can solve the reservoir hydration problem after hydraulic fracturing. • This method occurs after hydraulic fracturing and before formal mining. • Measured changes in properties of hydrated shale after heat treatment. • Combined with the engineering, the method's feasibility was analysed. [ABSTRACT FROM AUTHOR]

Abstract: The dynamic environmental economic dispatch (DEED) model is presented in this paper, in which the fuel cost and emission effect over a certain period of time are optimized as conflicting objectives. It is a high dimensional, nonlinear constrained multiobjective optimization problem when generators’ valve point effect, ramp rate limits and power load variation are considered. This paper proposes a modified adaptive multiobjective differential evolution (MAMODE) algorithm to solve the problem. In MAMODE, expanded double selection and adaptive random restart operators are proposed to modify the evolutionary processes for avoiding premature and a dynamic heuristic constraint handling (DHCH) approach is introduced to deal with the complicated constraints. The DHCH can lessen infeasible solutions gradually. To illustrate the effectiveness of the method, four cases based on three test power systems are studied. The simulation result indicates that the DEED can be solved quickly. Comparison of numerical results demonstrates the proposed method has higher performance. [Copyright &y& Elsevier]

Abstract: The binary nano-CaCO3/polypropylene (PP), poly(ethylene terephthalate) (PET) fibers/PP and ternary nano-CaCO3/PET fibers/polypropylene composites were prepared by melt blending method, and their structure and mechanical properties were investigated. The results show that the ternary nano-CaCO3/PET fibers/PP composite displays significantly enhanced mechanical properties compared with the binary PET fibers/PP and nano-CaCO3/PP composites, and neat PP. The X-ray diffraction, dynamic mechanical analysis, scanning electron microscopy and analysis of the non-isothermal crystallization kinetics were used to investigate the reinforcement mechanism of composites. The results indicate that the interfacial action and compatibility between PET fiber and PP are obviously enhanced by the addition of modified nano-CaCO3 particles in the ternary composites and the mechanical property enhancement in the ternary system may be mainly originated from the formation of β-form crystallites of PP induced by the synergistic effect between PET fibers and nano-CaCO3. [Copyright &y& Elsevier]

To verify the effect of hydrated shale treated by different heat treatment conditions (including heating temperature, heating rate and holding time) on shale gas exploitation efficiency. In this study, uniaxial compression tests were carried out on shale treated under different conditions, and the energy evolution in the process of shale deformation and failure was analysed. According to the energy dissipation and energy accumulation in the process of deformation and failure, the initial porosity, deformation resistance and rock strength of shale sample are discussed and analysed. The results indicate that after high-temperature heating treatment, the initial porosity, ability to resist deformation during elastic deformation stage, and brittleness characteristics of hydrated shale are all improved. The total input energy decreases by 23.16 %, and the peak dissipated energy decreases by 45.89 %, while the proportion of elastic strain energy to total energy in the compaction stage increases by 31.58 %. After thermal treatment, the hydrated shale exhibits increased initial damage, increased rock porosity, and enhanced ability to resist deformation. Therefore, high-temperature heat treatment of hydrated shale is conducted before shale gas exploitation, which enhances both the extraction efficiency and safety during the extraction process. This method is theoretically feasible. • Energy evolution analysis of heat treatment hydration shale deformation process. • The pre-peak input energy is reduced by 19 %, and the reservoir pores are increased. • The post-peak input energy is reduced by 16 %. The brittleness of rock is enhanced. • The ability of shale to resist deformation is enhanced after heat treatment. [ABSTRACT FROM AUTHOR]

Abstract: Floods have become increasingly alarming worldwide. Flood risk management in terms of assessing disaster risk properly is a great challenge that society faces today. Natural disaster risk analysis is typically beset with issues such as imprecision, uncertainty, and partial truth. There are two basic forms of uncertainty related to natural disaster risk assessment, namely, randomness caused by inherent stochastic variability and fuzziness due to macroscopic grad and incomplete knowledge sample. However, the traditional probability statistical method ignores the fuzziness of risk assessment with incomplete data sets and requires a large sample size of data. The fuzzy set methodology is introduced in the area of disaster risk assessment to improve probability estimation. The purpose of the current study is to establish a fuzzy model to evaluate flood risk with incomplete data sets. The present paper puts forward a composite method based on variable fuzzy sets and information diffusion method for disaster risk assessment. The results indicate that the methodology is effective and practical; thus, it has the potential to forecast the flood risk in flood risk management. We hope that by conducting such risk analysis, the impact of flood disasters can be mitigated in the future. [Copyright &y& Elsevier]