Balancing sustainable economic growth and environmental protection in developing countries is an important way to mitigate climate change. Based on panel data from nine provinces along the Silk Road Economic Belt between 2004 and 2021, this paper takes Chongqing, a pilot city for carbon trading rights, as the experimental group and the remaining eight provinces as the control group; we mainly analyze the impact of the carbon emissions trading policy on Chongqing’s carbon emissions and economic development after its implementation in 2013 using the difference-in-differences method (DID) and propensity score matching difference-in-differences method (PSM-DID). Then we use the synthetic control method (SCM) to test its robustness. The results showed that while maintaining the economic development speed, carbon trading helps to reduce carbon emissions. In addition, we also found that the economic activity effect and the energy intensity effect are the mediating effects of the carbon emissions reduction. Finally, taking the policy effect of the carbon emissions trading in Chongqing as a reference, this article confirmed the importance of aligning the carbon trading pathway with targeted green policies from the government. The government should drive the establishment of a regional carbon market in the nine provinces along the Silk Road Economic Belt, which could help to achieve sustainable development.

The pore-throat structure of low- to ultralow-permeability reservoirs is complex, causing the permeability to vary greatly under similar porosity conditions. Moreover, the pore-throat structures are the key factors that controled the physical properties of such kind of reservoirs. Therefore, conventional reservoir evaluation methods can hardly meet the research needs of low- to ultralow-permeability reservoir exploration and development. We have conducted our research on Paleogene Shahejie and Neogene Dongying low- to ultralow-permeability reservoirs in the eastern Nanpu Sag of the Bohai Bay Basin to address this issue. Cores, thin sections, and scanning electron microscopy were used to analyze the pore-throat structures to determine the characteristics of low- to ultralow-permeability reservoirs, and a new parameter for evaluating low- to ultralow-permeability reservoirs is developed. The results of this research show that primary pores, secondary pores, and microfractures are developed in the study area and that the pore-throat shape is mainly flaky or curved flaky. The microscopic pore-throat structure controlled the reservoir physical properties and fluid mobility of these reservoirs, the permeabilities of these reservoirs are dependent on the pore throats, and the correlation between connected pores and permeability is strong. Based on the analysis of the pore-throat structure, as well as the maximum mercury saturation (S_max) and the residual mercury saturation (S_r) at the maximum pressure and the minimum pressure obtained by the mercury injection test, an evaluation of the reservoir by using the mobility parameter of fluid (Δfm = S_max-S_r) is proposed, and the pore-throat radius R₁₅ obtained by the mercury intrusion experiment has the best correlation with the fluid mobility parameters. The mobility parameters of fluid can effectively improve the accuracy of logging interpretation of low- to ultralow-permeability reservoirs and provide a scientific basis for the scale stimulation and effective development of low- to ultralow-permeability reservoirs.

At present, single parameters for characterizing reservoir heterogeneity are commonly used in oilfield exploration and development, such as the permeability coefficient of variation, permeability inrush coefficient, and extreme difference, which have problems such as characterization blind spots. The heterogeneity of thick-bedded sand and conglomerate reservoirs is affected by various factors due to their thick layer characteristics, and it is difficult to effectively evaluate the heterogeneity of thick-bedded sand and conglomerate reservoirs with a single parameter. According to the characteristics of the thick sandy conglomerate reservoir, a comprehensive index calculation method of heterogeneity based on the combination weighting TOPSIS evaluation model is developed to comprehensively evaluate the heterogeneity of the sandy conglomerate reservoir by synthesizing the parameters affecting the heterogeneity of the reservoir, such as porosity, permeability, thickness of the sand layer, effective thickness coefficient, permeability variation coefficient, permeability rush coefficient, permeability contrast, and mudstone content. This approach is conducive to the normalized evaluation of complex reservoirs, and the quantitative characterization is more accurate and comprehensive. Based on the former classification scheme and the geologic characteristics of the study area, the evaluation criteria of the heterogeneity of the sandstone conglomerate reservoir are determined according to the comprehensive heterogeneity index. The research indicates that the objective weights of each indicator parameter of reservoir heterogeneity can be reasonably calculated by improving the criteria importance though intercrieria correlation weighting method, and the combined weights reflecting the importance of the indicators can be obtained by modifying the objective weights through the analytic hierarchy process. The calculated heterogeneous comprehensive index can be used to quantitatively characterize the heterogeneity of sand conglomerate reservoirs and solve the problems existing in conventional single parameters. The heterogeneous synthetic index has a good correlation with conventional parameters and has a good positive correlation with productivity. The weaker the heterogeneity is, the higher the productivity.

The Archie model is the foundation for calculating oil saturation, but limitations exist when the model is used to calculate oil saturation in the water-flooded layer. In the process of water injection, the dynamic change in oil saturation will be caused by the different degrees of water flooding and the properties of the injected water. Under the dynamic condition of water flooding, the Archie model is not suitable for calculating the oil saturation of water-flooded layers. By combining dynamic and static methods, a “double-ratio” model of the same sedimentary facies layer in the later development stage was established: Rt=R0−R0·f(Fw)=R0[1−f(Fw)]. Based on the parameters of rock resistivity and formation water resistivity, an improved Archie model for calculating oil saturation in water-flooded layers of the same sedimentary facies was established. The interpretation of the actual data of the Zhenwu oilfield in Jiangsu, China finds that the average relative error between the calculation result and the core analysis result is 5.46%. The calculation result is reasonable, which offers a scientific basis for predicting the remaining oil distributions. The computational results have been validated by real data sets. This improved mode can provide experience-based guidance for the calculation of the remaining oil saturation of the water-flooded layer in the same sedimentary interpretation layer.