Experimental study of the effects of a multistage pore-throat structure on the seepage characteristics of sandstones in the Beibuwan Basin:Insights into the flooding mode

To investigate the relationship between grain sizes, seepage capacity, and oil-displacement efficiency in the Liushagang Formation of the Beibuwan Basin, this study identifies the multistage pore-throat structure as a crucial factor through a comparison of oil displacement in microscopic pore-throat experiments. The two-phase flow evaluation method based on the Li-Horne model is utilized to effectively characterize and quantify the seepage characteristics of different reservoirs, closely relating them to the distribution of microscopic pores and throats. It is observed that conglomerate sandstones at different stages exhibit significant heterogeneity and noticeable differences in seepage capacity, highlighting the crucial role played by certain large pore throats in determining seepage capacity and oil displacement efficiency. Furthermore, it was found that the displacement effects of conglomeratic sandstones with strong heterogeneity were inferior to those of conventional homogeneous sandstone, as evidenced by multiple displacement experiments conducted on core samples with varying granularities and flooding systems. Subsequently, core-based experiments on associated gas flooding after water flooding were conducted to address the challenge of achieving satisfactory results in a single displacement mode for reservoirs with significant heterogeneity. The results indicate that the oil recovery rates for associated gas flooding after water flooding increased by 7.3%-16.4% compared with water flooding alone at a gas-oil ratio of approximately 7000 m^(3)/m^(3). Therefore, considering the advantages of gas flooding in terms of seepage capacity, oil exchange ratio, and the potential for two-phase production, gas flooding is recommended as an energy supplement mode for homogeneous reservoirs in the presence of sufficient gas source and appropriate tectonic angle. On the other hand, associated gas flooding after water flooding is suggested to achieve a more favorable development effect compared to a single mode of energy supplementation for strongly heterogeneous sandstone reservoirs.

后疫情时期契约农业对农户收入信心影响的实证研究

本文以新型冠状病毒肺炎事件为例,研究后疫情时期契约农业是否有助于提升农户收入信心。首先,基于生产函数理论建立数理模型,分析契约农业对农户收入信心的影响。其次,将农户从签订契约的合同商处得到的社会支持分为后疫情时期采取的有效防控措施、提供饲料来源等降低生产困难、疫情及生产相关信息、协助农户更快恢复生产生活四个方面,研究契约农业如何通过社会支持影响农户收入信心。选取229户农户调查问卷数据进行实证分析,估计结果显示,契约农业提升农户收入信心。为避免遗漏变量导致估计结果偏差,实证分析时引入户主及家庭特征等控制变量。最后,文章建议地方政府应该加大契约农业的推广,并加强疫情及生产等信息的宣传,加快本地生产生活恢复等。研究结论为契约农业的进一步推广提供理论解释,并对于后疫情时期提升农户收入信心、确保农户稳定增收具有指导意义。

Individual Differences in Learning Rate and Fear Response Predict Fear Memory and Recovery in Mice and Human Subjects

Dear Editor,Following an emotionally intensive and fearful traumatic event,some individuals develop anxiety disorders such as post-traumatic stress disorder (PTSD)[1].Cognitive therapy is used as an effective therapy to suppress fearful and/or traumatic memories;however,it fails in almost half of the anxious patients,resulting in the return of fearful memories [2].