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Adsorption characteristic of supercritical CO2 on coal directly determines the CO2 geological storage capacity. Through volumetric method, this paper analyzed the manifestation effects of different models on the experimental data of various ranked coals and activated carbon. The results indicate that the variation rate of gaseous CO2 density reaches the peak around 8 MPa. Introduction of parameter k could improve the fitting quality and trap various experimental errors. The adsorption mechanism of coal samples from Tiefa and Wolonghu is micropore filling. As coal samples of Yaojie is collected from a CO2 -rich reservoir, the alteration effect by experimental CO2 adsorption is unobvious and its micropores develop quite well, thus the greatest absolute adsorption is higher than other samples. When the gas density increases gradually, the gap between excess adsorption and absolute adsorption widens, and the absolute adsorption determines the adsorption capacity of the coal samples. The fitting CO2 adsorbed phase density of the activated carbon by OK model is 1.004 g/cm3.

In order to effectively reduce the gas content of coal seam, realize the efficient utilization of gas resources and reduce the difficulty of underground gas management, combined with the geological characteristics of Shoushan I mine site, we built a surface well zoning gas extraction technology, aiming to realize the systemization of gas management in the mine area. Based on the spatial and temporal distribution characteristics of mining activities, the mine field was divided into unmined area, mined area and vacant area, and different surface wells were established for gas extraction in zoning, so as to realize the change from gas management to gas utilization. The systematic gas management technology includes four parts: scientific arrangement of surface wells, well structure and construction design, reservoir fracturing and permeability enhancement in unmined area, and drainage and gathering engineering. The selection of surface well locations is based on the spatial stratification, coal seam characteristics, surface location, coal seam recovery and gas storage conditions. In the mining area, based on the height of the collapse zone and fissure zone after coal seam retrieval, the straight wells and L-type wells in the mining area were designed to be located in the middle and upper part of the fissure zone, so that the gas can be extracted efficiently from multiple coal seams in the area with the effect of pressure relief of this coal seam retrieval. The L-shaped well body in the unmined area, the straight well body in the mined area, the L-shaped well body in the mined area and the straight well body in the mined area were designed. Hydraulic fracturing of the coal seam in the unmined area to achieve coal seam penetration increase, the composite fracturing process of directional injection & pumped bridge plug type light casing fracturing was selected to fracture the coal seam, deep penetration reinforcing bullet was used for injection operation, and 20/40 mesh quartz sand was used as proppant. In Shoushan No.1 Mine, the engineering practice of surface well zoned gas extraction technology was carried out, and the statistics of gas extraction from different types of surface wells in the mine area showed that: the maximum daily gas production from a single well in the mining area can exceed 40 000 m3, and the accumulated gas extraction from a single well is up to 2 597 000 m3, and 11 wells are currently being drilled for extraction in the well field area, with an accumulated extraction of up to 14 252 000 m3. Field effect test showed that the implementation of surface wells zoned gas extraction technology can achieve efficient gas extraction, forming a gas management model of “mining one layer to treat multiple layers”.

In order to solve the problem of gas overrun and low utilization rate caused by mining pressure relief gas pouring into mining working space in high gas outburst coal seam, this paper used numerical simulation and field application methods to study the efficient extraction of coal gas in front of the working face under the influence of dynamic pressure. The results show that according to the gas concentration monitoring data on site, the coal body in front of the working area was divided into high efficiency extraction zone, effective extraction zone and original extraction zone. The efficient extraction zone was within 20 m in front of the working face, with an average gas extraction concentration of 30% or more. Gas extraction in the effective extraction zone was affected by the dynamic pressure, and the extraction concentration decreased fluctuatingly with increasing distance from the working face. The range of the original extraction area is 50-60 m away, and the gas concentration of the borehole was stable below 10%, which was less influenced by the mining movement. The second extraction technology of dynamic pressure gas in the floor gas extraction roadway of high gas outburst coal seam through the crossing boreholes was better applied in the middle extraction roadway of 12110 working face, the number of extraction holes in the dynamic pressure area was 5%-10% of that in the non-dynamic pressure area, but the monthly extraction volume could reach up to 74.01% of the monthly extraction volume inthe non-dynamic pressure area.

The output of wind and solar power stations is intermittent and fluctuating,but their complementarity can be fully realized with reasonable wind-solar capacity ratio. The inaccurate theoretical power calculation of power station affects the extraction of true features of wind and solar,and then leads to large capacity matching error. The model-generator method commonly used in theoretical power calculation of new energy power stations is improved in this study. The abnormal data are firstly identified and reconstructed,and then the abnormal model-generators are identified and updated. Furthermore,according to the actual operation of non-model-generators,the dynamic information window is selected. By using the measured power of model-generator and non-model-generator in the dynamic information window,the non-model-generators are grouped and the scale coefficient of each group of non-model-generator is dynamically identified,and thus the theoretical power of new energy power stations is calculated. Based on the calculation of historical theoretical power for many years,the characteristics of new energy power stations are analyzed. The random output scenario is simulated accordingly,and the optimization method of wind-solar capacity ratio based on the risk of source-load mismatching is established. The accuracy of the improved model-generator method is verified by examples. By using this method,the improved theoretical power data of wind farm and photovoltaic power stations in a certain area of northwest China are obtained,and the optimal ratio of wind-solar capacity in this area is optimized. The improved model machine method proposed in this paper can effectively improve the calculation accuracy of theoretical power of new energy power stations,and the optimal ratio of wind-solar capacity calculated based on this method can provide reference for wind-solar power generation capacity of regional power grid.

Affected by geology and mining, a certain number of low-yield wells will appear after a period of production in coalbed methane wells, and technical repairs are urgently needed to restore their production capacity to the maximum. Therefore, it is of great significance to establish a reasonable and feasible theoretical standard to evaluate the workover priority of CBM wells for the efficient utilization of CBM resources. From the perspectives of technical feasibility and economic rationality, eight key indicators that affect the cost performance of CBM well workover are screened. Combining the entropy value method and the TOPSIS comprehensive ranking method, the surface coalbed methane well repair priority entropy value-TOPSIS comprehensive evaluation model was constructed, and the surface coalbed methane well repair priority evaluation was carried out by taking 9 surface coalbed methane wells that urgently needed to be repaired in a mine as the evaluation objects. The evaluation results show that among the economic indicators, the average gas production per meter in the 30 days before the coal bed methane well was stopped and the cumulative gas production per meter before the stop had a relatively high weight, which were 29.68% and 13.83% respectively, This shows that in coalbed methane well workover operations, the long-term gas production potential of the coalbed methane well and the gas production capacity when disturbed by harmful factors are the decisive factors affecting the priority of coalbed methane well workover; Among the technical indicators, the degree of casing deformation and the depth of the coalbed methane well have a relatively high weight, accounting for 11.34% and 9.90% respectively, This shows that the smaller the deformation of the wellbore casing and the shallower the depth of the coalbed methane well, the higher the priority of the workover of the coalbed methane well; The ranking of the production recovery rates of the three coalbed methane wells in the Pingdingshan mining area after workover operations is consistent with the results output by the evaluation model, which proves that the evaluation model is reasonable for determining the priority of workovers for damaged wellbores; This evaluation model can provide a theoretical reference for small and medium-sized coalbed methane development companies to determine the priority of workovers. [ABSTRACT FROM AUTHOR]