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Gob-side entry retaining (GSER) technology has been widely used in underground coal mines. However, the applicable conditions of GSER technology in practical engineering still need further clarification to prevent the safety hazards and significant economic losses caused by its failure. In this study, 587 application cases of GSER in China from 2000 to 2024 were collected, and the relevant data, such as geological conditions and key technical parameters of GSER projects and their impact on engineering practices, were systematically analyzed. Considering the technical characteristics and the developing status of GSER technology, the current status of the application of GSER engineering in the mining areas of China was obtained, and then the applicable geological conditions and optimal technical parameters for the effective implementation of GSER technology were identified. Additionally, the existing technical challenges and further prospects of GSER technology were illustrated. This study provides a reference for reasonable applications and further research of GSER technology. [ABSTRACT FROM AUTHOR]

To improve the research and evaluation effect of remaining oil in high water cut oilfields， this paper sorted out the concept and influencing factors of remaining oil， summarized the research methods and applicable conditions of remaining oil from three aspects of microscopic distribution， macroscopic distribution， and quantitative analysis of saturation of remaining oil， and discussed the distribution characteristics of remaining oil in water flooding reservoirs， heavy oil reservoirs， and chemical flooding reservoirs based on literature research. The difficulties and development trends of remaining oil research were further put forward. The results show that the influencing factors of remaining oil mainly include geological structure， sedimentary microfacies， reservoir heterogeneity， well pattern density， well pattern， perfection of injection-production system， and production performance. The remaining oil research methods include experimental analysis， numerical simulation， field testing， etc. The research purposes and applicable conditions of each method are different， and the test results reflect the distribution of remaining oil saturation at different locations and scales. The distribution of remaining oil in high water cut oilfields is highly dispersed and relatively enriched， and the microscopic distribution of remaining oil is in various forms of continuous and discontinuous phases. The development trend of remaining oil research includes but is not limited to five aspects： the construction of super-large physical models， the integration of multi-scale high-resolution imaging systems， the improvement of numerical simulation methods considering the time-varying and discontinuous nonlinear seepage of different displacement media and physical properties， the comprehensive application of multidisciplinary and multi-method field testing， and the wide application of big data artificial intelligence.

Copyright of Petroleum Geology & Recovery Efficiency is the property of Petroleum Geology & Recovery Efficiency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Gob-side entry retaining (GSER) technology has been widely used in underground coal mines. However, the applicable conditions of GSER technology in practical engineering still need further clarification to prevent the safety hazards and significant economic losses caused by its failure. In this study, 587 application cases of GSER in China from 2000 to 2024 were collected, and the relevant data, such as geological conditions and key technical parameters of GSER projects and their impact on engineering practices, were systematically analyzed. Considering the technical characteristics and the developing status of GSER technology, the current status of the application of GSER engineering in the mining areas of China was obtained, and then the applicable geological conditions and optimal technical parameters for the effective implementation of GSER technology were identified. Additionally, the existing technical challenges and further prospects of GSER technology were illustrated. This study provides a reference for reasonable applications and further research of GSER technology.

In order to evaluate the effect of chromium content in carbon steel on the corrosion resistance of carbon steel materials, the corrosion behavior of 1Cr and N80 steels was investigated in this study by immersion weight loss method under three different CO2 partial pressure and temperature conditions in formation water for 72, 168 and 336 h. Detailed material surface morphological characterization was performed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and confocal laser scanning microscopy (CLSM). The results show that the pitting corrosion of N80 carbon steel is serious at medium temperature and low CO2 partial pressure (50 °C, 0.30 MPa), and the corrosion rate is significantly higher than that of 1Cr steel. However, at high-temperature and high CO2 partial pressure (100 °C/0.63 MPa and 114 °C/0.73 MPa), 1Cr steel is more inclined to the mesa corrosion dominated by local corrosion characteristics, and the corrosion rate is seriously higher than that of N80 steel with uniform corrosion. From the experimental results, we can know the corrosion resistance of carbon steel and 1Cr steel is not only affected by the corrosion environment, but also depends on the formation process of the product film, as well as its compactness and integrity characteristics. At low-temperature and low CO2 partial pressure, 1 wt.% chromium content can provide a certain degree of corrosion resistance, while high temperature and high partial pressure can broaden the application window of carbon steel N80 and weaken the corrosion inhibition effect of chromium. [ABSTRACT FROM AUTHOR]

Micro scale fractures play a crucial role in facilitating the migration of oil and gas in low permeability shale reservoirs. However, the identification of such fractures is a complex task. The efficacy of the dual lateral log physical field changes as a means of identifying shale micro fractures remains uncertain. To address this issue, a three-layer shale bedding fracture model was developed using the finite element method and core and conventional logging data from eight wells, which was based on different shale reservoirs within the Yanchang Formation in the Ordos Basin. The present study examines the dual lateral log response characteristics resulting from distinct characteristics of horizontal bedding fractures, with a focus on the response mechanism. The simulation of logging response characteristics of shale and siltstone combination were utilized by core statistical data for verification purposes. The results indicate that under the lithology combination of shale and siltstone, the magnitude of the difference between the resistivity of the filled fracture and the formation resistivity, the greater the formation resistivity of the shale itself, the wider the fracture width, and the greater the difference between the apparent resistivity and the real formation resistivity. Furthermore, the suitable conditions for the detection of shale bedding fracture characteristics by dual lateral log are clarified. In the presence of effective filling, the dual lateral log has the capability to identify shale fractures at the micron scale. The findings of our study establish a theoretical framework for the identification and assessment of shale fractures, and furnish technical assistance for the optimal selection of “sweet spots” within shale reservoirs and the precise evaluation of reservoirs. This study lays a theoretical foundation for the identification and evaluation of shale fractures, and provides technical support for the optimal “sweet spot” selection of shale reservoirs and the accurate evaluation of reservoirs.

Approximate calculation of the pH of a NaHA solution plays an important role in analytical chemistry. However, the physical meanings and applicable conditions of the pH approximate formulas are not demonstrated in detail in current textbooks. In this paper, the applicable conditions and physical significance of various approximate formulas are described. The approximate formulas with incorrect physical meanings and inappropriate applicable conditions should be modified. NaHA solutions can be categorized as acidic (Ka1Ka2 > Kw) or alkaline (Ka1Ka2 < Kw). When cKa2 ≥ 20Kw, by assuming that the production of OH- from water and from HA- is negligible, the approximate formula of an acidic NaHA solution is obtained. When c ≥ 20Ka1 (namely cKb2 ≥ 20Kw), the approximate formula of an alkaline NaHA solution is obtained by ignoring the production of H+ from water and HA-. The formula pH = (pKa1 + pKa2)/2 is suitable for both acidic and alkaline NaHA solutions, but their applicable conditions are quite different. This paper carefully discussed the pH calculation of NaHA solutions. The computation results demonstrated that some formulas should be disabled and the related wrong statements in textbooks be corrected. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering Management / Gongcheng Guanli Xuebao is the property of Journal of Engineering Management Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

: Using directional ramps to reduce intersection delays is one of the means to alleviate the problem of urban node congestion. However, taking into account the constraints of land use, capital and environment, it is necessary to carefully demonstrate the applicability and conditions of constructing an interchange. This study aims at the preliminary feasibility of building a left - tum directional ramp in the city. It analyzes the required road conditions and traffic conditions, and uses VISSIM simulation to obtain the delays, emissions and fuel consumption of the intersection before and after the ramp. Estimate the construction cost of the directional ramp through the proposed standard intersection, compare and analyze its economics, and summarize the method for quickly assessing whether a left - turn directional ramp can be built. The study puts forward new ideas for improving the feasibility study of urban interchange planning. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Zhejiang University (Science Edition) is the property of Journal of Zhejiang University (Science Edition) Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Engineering Management / Gongcheng Guanli Xuebao is the property of Journal of Engineering Management Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To achieve the purpose of reducing water production, increasing oil production, cutting down cost and increasing efficiency without additional investment and cost, the injection-production coupling technique is adopted to change the underground pressure field and strengthen the weakly affected area. Currently, the studies on the mechanism of injection-production coupling and the optimization of injection-production parameters are mainly carried out by using mathematical models and material models at home and abroad. However, there are few studies on the utilization range and utilization degree of residual oil. In this paper, a numerical simulation model is established based on the actual fault block of Xianhe. Through the analysis of pressure gradient and pressure change, the utilization range and utilization degree of residual are obtained. Besides, by analyzing the influence of change of influencing factors on the development effect of injection-production coupling mode, the applicable conditions of injection-production coupling mode are given, which can provide theoretical ordnance for oil filled work. Results show that the operating range of residual oil under the condition of injection-production coupling is about 4 times that under the condition of stable water injection. In the fault reservoir water flooding development, the further the oil well is away from the fault, the closer the water well is to fault, and the more suitable the injection-production coupling is. Borderless and bottomless water reservoir is more suitable for the development of injection-production coupling mode. The injection-production coupling method has good adaptability to inclined reservoirs. [ABSTRACT FROM AUTHOR]

Copyright of Natural Gas & Oil is the property of Editorial Department of Natural Gas & Oil and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)