Application and Principle of Bolt-Mesh-Cable Control Technology in Extremely Soft Coal Seam Roadway
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More articlesStress Sensitivity of Proppant-Containing Fractures and Its Influence on Gas Well Productivity
Formation pressure gradually decreases with fracturing fluid flowback and gas production. Due to the stress sensitivity of the fractures, the permeability of the artificial fractures after fracturing becomes lower, which significantly affects gas well productivity. This paper focuses on two questions: (1) the stress sensitivity of proppant-containing fractures with different roughness and (2) tight gas well productivity considering stress sensitivity. Two types of artificial fracture samples, smooth and rough, are prepared and filled with different proppant concentrations. Then, the changing confining pressure method is used to quantify sample stress sensitivity. On this basis, the productivity equation for the fractured well with finite conductivity that considers fracture and matrix stress sensitivity is derived, and the influence of stress sensitivity on productivity is discussed. The results show that proppant concentration and fracture surface roughness will significantly affect fracture permeability and stress sensitivity; with increasing proppant concentration, fracture permeability increases, stress sensitivity decreases, and well productivity increases; under the same proppant concentration, the stress sensitivity is lower and the gas production is higher for smooth fracture; and when the artificial fracture changes from no proppant to proppant, the productivity of the fracturing well is improved the most.
Identification of Gas-Water Two-Phase Flow Patterns in Horizontal Wells of Shale Gas Reservoirs Based on Production Logging Data
In order to clarify the gas-water two-phase flow law in horizontal wells and study the gas-water two-phase flow characteristics in horizontal wells, firstly, the gas-water two-phase in a horizontal well is numerically simulated and analyzed, and the flow pattern distribution under different well inclination angles and different phase separation flow rates is obtained. Secondly, a series of production logging instruments including CAT instrument was used to conduct experimental research on gas-water two-phase flow under different flow conditions, and the measured values of each CAT probe were extracted to reflect the local holdup under different flow patterns. Finally, SSA-BP neural network algorithm is used to identify a gas-water two-phase flow pattern in a wellbore by using experimental parameters such as center holdup, well inclination angle, spinner revolution, and CAT probe measurements. The recognition accuracy of the neural network was improved from 83.75% to 91.66%, and the operation speed was accelerated. It provides a research idea to explore the flow characteristics of gas-water two-phase flow in horizontal wells.
Risk Assessment for Water Disaster of Karst Tunnel Based on the Weighting of Reliability Measurement and Improved Extension Cloud Model
Risk assessment of water disaster in karst tunnels is a nonlinear, complex, and uncertain system problem. Based on the reliability measurement method and extension cloud theory, the reliability measurement weighting and improved extension cloud model are established for the risk assessment of water disaster in karst tunnels. Firstly, on the basis of fully considering the relevance of evaluation indicators, a dynamic weighting theory for reliability measurement of indicators based on Jousselme distance is proposed. Secondly, according to the two different entropy algorithms of the extension cloud model, an improved extension cloud model is proposed based on the entropy algorithm fusion of game theory. The comprehensive cloud correlation degree obtained by the improved extension cloud model is combined with the indicator reliability measure weight. Then, the dangerous state of the water disaster in karst tunnels is judged, and the visualization of the water disaster level judgment is realized. And the model is tested with sample data from six typical karst tunnels. Finally, the model is applied to the Yangpeng Karst Tunnel on the Beijing-Zhuhai expressway. The results show that the water disaster level of the tunnel is I, and the evaluation results are consistent with the actual situation. Compared with the matter element extension model and the extension cloud model, the calculation results are more accurate. The corresponding treatment measures have been taken, and the good effect of water disaster treatment has been achieved. The practical value of the model is further proved, and a new reference method is provided for the prediction and prevention of water disaster in karst tunnels.
Secondary Migration Trend Based on Basin Modeling: A Case Study of the Cambrian Petroleum System in the Tarim Basin
Secondary hydrocarbon migration is an important aspect of oil-gas accumulation research. While previous studies have relied on geological and fluid geochemical characteristics to predict migration direction, these results are often limited by the number of samples. In recent years, basin simulation has emerged as a valuable tool in hydrocarbon migration research due to its extensive algorithms and adaptable modeling capabilities. It has obvious technical advantages especially for resource evaluation in areas with a lower exploration degree and scarce data. The deep oil and gas in the Cambrian petroleum system in the Tarim Basin is a deep hydrocarbon challenging area in China. There has been no breakthrough in exploration due to the large burial depth () and the long accumulation and transformation processes. Therefore, predicting the secondary migration of Cambrian oil and gas has become the key to solving this problem. In this study, first, the thermal evolution of the Lower Cambrian source rocks in the Tarim Basin was recovered, and the three thermal evolution models were developed. The secondary migration process of the Cambrian petroleum system was restored using the geologic model of the source rocks and paleotectonic evolution and the latest fluid potential information. By comparing the simulation results, four secondary migration models of the ultradeep oil-gas migration and accumulation were developed: multisource, multiphase, multidirectional accumulation; multisource, multiphase, single-directional accumulation; single-source, multiphase, multidirectional accumulation; and single-source, multiphase, single-directional accumulation. The fluid potential simulation results indicate that the Cambrian oil and gas have salient inheritance characteristics. The dominant migration channels in the uplift and slope are beneficial to oil-gas migration and accumulation, and the Katake uplift and the west Bachu uplift have multisource charging accumulation. The east Bachu uplift and the Tabei uplift are oil-gas accumulation zones that are beneficial to the lower petroleum system due to the continuous charging of a single petroleum system. This fluid potential simulation provides a new solution for studying the secondary migration of deep oil and gas. It provides an important reference for studying hydrocarbon accumulation in deep and ultradeep areas.
Dynamic Response Analysis of Roadway Surrounding Rock Induced by Dynamic Load under the Action of Hard and Thick Rock Stratum
In the process of coal seam mining, there are often hard thick key layers in the overlying strata. Due to the high strength and good integrity of the hard thick key layer, after the hard thick key layer is broken, the overlying strata will collapse and lose stability in a large area, which is very easy to induce dynamic disasters such as rock burst, mine earthquake, coal wall caving, and roof slab caving. Aiming at the hard and thick key layer overlying the working face, the dynamic response of the mine under the strong mine earthquake induced by the breaking of the main key layer of high-level magmatic rock is numerically simulated and analyzed by using FLAC2D numerical simulation software, and the variation laws of the stress field, displacement field, and velocity field of the coal seam roadway under different boundary conditions and different focal heights are studied. The research shows that the roof of solid coal roadway is prone to vibration in a small range, and the displacement increases and decreases with the disturbance. The displacement of the floor and two sides of the solid coal roadway and the top floor and two sides of the roadway along the goaf continues to increase in the initial stage of the disturbance, and the displacement will remain stable with the continuation of the disturbance. The displacement of both sides and roof and floor of gob roadway can reach stability in the later stage of disturbance, and with the increase of the number of adjacent goaf, the longer it takes for the displacement of surrounding rock to reach stability. When the focal height is lower than 90 m, the variation of surrounding rock response increases sharply with the decrease of focal height. When a strong earthquake occurs in the low rock stratum, the impact damage of roadway surrounding rock is almost inevitable. The influence degree of strong earthquake on the stability of roadway surrounding rock is arranged as follows: gob-side roadway (mined out on one side) > solid coal roadway (mined out on both sides) > solid coal roadway (mined out on one side). The evolution process also shows that the working face boundary conditions have an important influence on the energy propagation of mine earthquake. With the increase of the number of adjacent goafs, the faster the energy attenuation rate of mine earthquake propagation is. The research results have important reference significance for the safe mining of working face under similar geological conditions.
Progressive Evolution Model of Fault Water Inrush Caused by Underground Excavation Based on Multiphysical Fields
Underground fault water inrushes are frequent hydrogeological disasters associated with underground mining and tunnel construction projects. In this study, we analyze the water inrush mechanism of underground engineering by building a numerical simulation model to evaluate the process of water inrush, analyze water inrush changes under various working conditions, and consider the fluid-solid coupling effect of rock mass and water. These analyses provide effective suggestions for preventing water inrush from faults. The study establishes a two-dimensional numerical model based on Darcy’s law and plane strain field to analyze water inrush from faults in underground engineering. The analysis shows that factors such as aquifer pressure, permeability between the aquifer and fault zone, and permeability sensitivity coefficient are important considerations that affect the occurrence of water-inrush disasters. The study also identifies the sudden change in water inrush speed at the fault zone and the roadway when the working condition is changed as an indication of the nature of water inrush at the fault. Additionally, the study presents preventive measures such as drainage grouting to ensure the safety of underground engineering constructions. Overall, this research provides important insights into the causes and effects of water inrush from faults and can inform practical measures to mitigate the risks associated with underground engineering.