Tight sandstone reservoirs have small pore throat sizes and complex pore structures. Taking the Chang 6 tight sandstone reservoir in the Huaqing area of the Ordos Basin as an example, based on casting thin sections, nuclear magnetic resonance experiments, and modal analysis of pore size distribution characteristics, the Chang 6 tight sandstone reservoir in the study area can be divided into two types: wide bimodal mode reservoirs and asymmetric bimodal mode reservoirs. Based on the information entropy theory, the concept of “the entropy of microscale pore throats” is proposed to characterize the microscale pore throat differentiation of different reservoirs, and its influence on the distribution of movable fluid is discussed. There were significant differences in the entropy of the pore throat radius at different scales, which were mainly shown as follows: the entropy of the pore throat radius of 0.01~0.1 μm, >0.1 μm, and <0.01 μm decreased successively; that is, the complexity of the pore throat structure decreased successively. The correlation between the number of movable fluid occurrences on different scales of pore throats and the entropy of microscale pore throats in different reservoirs is also different, which is mainly shown as follows: in the intervals of >0.1 μm and 0.01~0.1 μm, the positive correlation between the occurrence quantity of movable fluid in the wide bimodal mode reservoir is better than that in the asymmetric bimodal mode reservoir. However, there was a negative correlation between the entropy of the pore throat radius and the number of fluid occurrences in the two types of reservoirs in the pore throat radius of <0.01 μm. Therefore, pore throats of >0.1 μm and 0.01~0.1 μm play a controlling role in studying the complexity of the microscopic pore throat structure and the distribution of movable fluid in the Chang 6 tight sandstone reservoir. The above results deepen the understanding of the pore throat structure of tight sandstone reservoirs and present guiding significance for classification evaluation, quantitative characterization, and efficient development of tight sandstone reservoirs.
Diagenesis is one of the most important factors impacting the performance of many reservoirs and is perhaps the most important factor impacting the performance of tight sandstone reservoirs, such as those of the Sulige gas field in the Ordos Basin of China. However, the relationship between diagenesis and related parameters determining reservoir physical properties remains unclear. Therefore, we have analyzed experimental data from high-pressure mercury intrusion porosimetry, scanning electron microscopy, and thin sections in addition to using a porosity recovery calculation model to investigate microscopic characteristics, diagenesis, and pore-evolution processes of the low-permeability tight gas reservoir of the He-8 unit of the Sulige gas field in the Ordos Basin. In addition, we have identified the impacts of diagenesis on reservoir characteristics and established the relationship between diagenesis and reservoir quality evolution. We also used the Beard primary porosity model to recover the primary porosity, and to built the reducing and enhancing calculation models for intergranular pore, dissolution pore, and intercrystalline pore during diagenesis. Based on the quantitative relationship between diagenesis processes and porosity evolution, we found that the results of simulation calculation and experimental works were in close agreement with minimal error.
The character of residual oil formed during water flooding, one important technique to enhance oil recovery, is helpful to further study permeability and recovery in tight sandstone oil reservoirs. In this paper, we take a tight sandstone reservoir in Ordos Basin as the research object and use in situ displacement X-CT scanning technology to analyze the dynamic characteristics of oil during water flooding. Firstly, core pore radius and oil storage space radius were measured from digital cores which are acquired in different water flooding stages by X-CT scanning technology. Secondly, analytical and evaluation methods were established to describe fluid distribution in the pore space of the core in different water flooding stages based on curve similarity. Finally, by numerical results, we analyzed the oil distribution features in the process of water flooding for core samples. In this paper, the oil distribution characteristics during water flooding are revealed based on digital core analysis. Also, a quantitative evaluation method is given to provide theoretical guidance.
Background: Ryanodine receptor type 2 (RyR2) mediate Ca 2+ release from the endoplasmic and sarcoplasmic reticulum (ER and SR), which is involved in the peripheral coupling of mouse cardiomyocytes, and thereby plays an important role in cardiac contraction. Junctophilin-2 (JPH2, JP2) is anchored to the plasma membrane (PM) and membranes of the ER and SR, and modulates intracellular Ca 2+ handling through regulation of RyR2. However, the potential RyR2 binding region of JPH2 is poorly understood. Methods: The interaction of JPH2 with RyR2 was studied using LC-MS/MS , bioinformatic analysis,co-immunoprecipitation studies in cardiac SR vesicles. GST-pull down analysis was performed to investigate the physical interaction between RyR2 and JPH2 fragments. Immunofluorescent staining was carried out to determine the colocalization of RyR2 and JPH2 in isolated mouse cardiomyocytes. Ion Optix photometry system was used to measure the levels of intracellular Ca 2+ transients in cardiomyocytes isolated from JPH2 knock down mice. Results: We report that (i) JPH2 interacts with RyR2 and (ii) the C terminus of the JPH2 protein can pull down RyR2 receptors. Confocal immunofluorescence imaging indicated that the majority of JPH2 and RyR2 proteins were colocalized near Z-lines. A decrease in the levels of JPH2 expression reduced the amplitude of Ca 2+ transients in cardiomyocytes. Conclusions: This study suggests that the C terminus domain of JPH2 is required for interactions with RyR2 in the context of peripheral coupling of mouse cardiomyocytes, which provide a molecular mechanism for looking for Ca 2+ - related diseases prevention strategies.
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