In-situ gas contents of a multi-section coal seam in Sydney basin for coal and gas outburst management

The gas content is crucial for evaluating coal and gas outburst potential in underground coal mining. This study focuses on investigating the in-situ coal seam gas content and gas sorption capacity in a representative coal seam with multiple sections (A1, A2, and A3) in the Sydney basin, where the CO_(2) composition exceeds 90%. The fast direct desorption method and associated devices were described in detail and employed to measure the in-situ gas components (Q_(1), Q_(2), and Q_(3)) of the coal seam. The results show that in-situ total gas content (Q_(T)) ranges from 9.48 m^(3)/t for the A2 section to 14.80 m^(3)/t for the A3 section, surpassing the Level 2 outburst threshold limit value, thereby necessitating gas drainage measures. Among the gas components, Q_(2) demonstrates the highest contribution to Q_(T), ranging between 55% and 70%. Furthermore, high-pressure isothermal gas sorption experiments were conducted on coal samples from each seam section to explore their gas sorption capacity. The Langmuir model accurately characterizes CO_(2) sorption behavior, with ft coefcients (R^(2)) greater than 0.99. Strong positive correlations are observed between in-situ gas content and Langmuir volume, as well as between residual gas content (Q_(3)) and sorption hysteresis. Notably, the A3 seam section is proved to have a higher outburst propensity due to its higher Q_(1) and Q_(2) gas contents, lower sorption hysteresis, and reduced coal toughness f value. The insights derived from the study can contribute to the development of efective gas management strategies and enhance the safety and efciency of coal mining operations.

Advances in gas content based on outburst control technology in Huainan, China

The sudden and violent nature of coal and gas outbursts continues to pose a serious threat to coal mine safety in China. One of the key issues is to predict the occurrence of outbursts. Current methods that are used for predicting the outbursts in China are considered to be inadequate, inappropriate or impractical in some seam conditions. In recent years, Huainan Mining Industry Group(Huainan) in China and the Commonwealth Scientific and Industrial Research Organisation(CSIRO) in Australia have been jointly developing technology based on gas content in coal seams to predict the occurrence of outbursts in Huainan. Significant progresses in the technology development have been made, including the development of a more rapid and accurate system in determining gas content in coal seams, the invention of a sampling-while-drilling unit for fast and pointed coal sampling, and the coupling of DEM and LBM codes for advanced numerical simulation of outburst initiation and propagation. These advances are described in this paper.

Comparing potentials for gas outburst in a Chinese anthracite and an Australian bituminous coal mine

Gas outbursts in underground mining occur under conditions of high gas desorption rate and gas content,combined with high stress regime, low coal strength and high Young's modulus. This combination of gas and stress factors occurs more often in deep mining. Hence, as the depth of mining increases, the potential for outburst increases. This study proposes a conceptual model to evaluate outburst potential in terms of an outburst indicator. The model was used to evaluate the potential for gas outburst in two mines, by comparing numerical simulations of gas flow behavior under typical stress regimes in an Australian gassy mine extracting a medium-volatile bituminous coal, and a Chinese gassy coal mine in Qinshui Basin(Shanxi province) extracting anthracite coal. We coupled the stress simulation program(FLAC3D) with the gas simulation program(SIMED II) to compute the stress and gas pressure and gas content distribution following development of a roadway into the targeted coal seams. The data from gas content and stress distribution were then used to quantify the intensity of energy release in the event of an outburst.

Determination of indices and critical values of gas parameters of the first gas outburst in a coal seam of the Xieqiao Mine

Based on the important role in mine safety played by parameters of the first gas outburst, we propose a method of combining historic data, theoretical analysis and experimental research for the purpose of crit- ical values of gas parameters of the first gas outburst in a coal seam of the Xieqiao Mine. According to a characteristic analysis and a summary of the rules of coal and gas outbursts in the No.8 coal seam of a Hua- inan mine, we have investigated their effect on coal and gas outbursts in terms such as ground stress, gas, and coal structure. We have selected gas parameters and determined the critical values of each of the fol- lowing indices： gas content as 7.7 m^3/t, tectonic coal as 0.8 m thick, the absolute gas emission as 2 m3/min, the rate of change as 0.7 m3/min, the gas desorption index of a drilling chip KI as 0.26 mL/（g min^1/2） and the values of desorption indexes Ah2 as 200 Pa. From a verification of the production, the results indicate that application of each index and their critical values significantly improve the level of safety in the pro- duction process, relieve the burden upon the mine, save much labor and bring clear economic benefits.

Geochemical characteristics and genetic mechanism of the high-N2 shale gas reservoir in the Longmaxi Formation, Dianqianbei Area, China

As an important pilot target for shale gas exploration and development in China,the Longmaxi Formation shale in the Dianqianbei Area is characterized by high content of nitrogen,which severely increases exploration risk.Accordingly,this study explores the genesis of shale gas reservoir and the mechanism of nitrogen enrichment through investigating shale gas compositions,isotope features,and geochemical characteristics of associated gases.The high-nitrogen shale gas reservoir in the Longmaxi Formation is demonstrated to be a typical dry gas reservoir.Specifically,the alkane carbon isotope reversal is ascribed to the secondary cracking of crude oil and the Rayleigh fractionation induced by the basalt mantle plume.Such a thermogenic oil-type gas reservoir is composed of both oil-cracking gas and kerogen-cracking gas.The normally high nitrogen content(18.05%-40.92%) is attributed to organic matter cracking and thermal ammoniation in the high-maturity stage.Specifically,the high heat flow effect of the Emeishan mantle plume exacerbates the thermal cracking of organic matter in the Longmaxi Formation shale,accompanied by nitrogen generation.In comparison,the abnormally high nitrogen content(86.79%-98.54%) is ascribed to the communication between the atmosphere and deep underground fluids by deep faults,which results in hydrocarbon loss and nitrogen intrusion,acting as the key factor for deconstruction of the primary shale gas reservoir.Results of this study not only enrich research on genetic mechanism of high-maturity N_@ shale gas reservoirs,but also provide theoretical guidance for subsequent gas reservoir resource evaluation and well-drilling deployment in this area.

Research into comprehensive gas extraction technology of single coal seams with low permeability in the Jiaozuo coal mining area

For a low permeability single coal seam prone to gas outbursts, pre-drainage of gas is difficult and inefficient, seriously restricting the safety and efficiency of production. Radical measures of increasing gas extraction efficiency are pressure relief and infrared antireflection. We have analyzed the effect of mining conditions and the regularity of mine pressure distribution in front of the working face of a major coal mine of the Jiaozuo Industrial （Group） Co. as our test area, studied the width of the depressurization zone in slice mining and analyzed gas efficiency and fast drainage in the advanced stress relaxation zone. On that basis, we further investigated and practiced the exploitation technology of shallow drilling, fan dril- ling and grid shape drilling at the working face. Practice and our results show that the stress relaxation zone is the ideal region for quick and efficient extraction of gas. By means of an integrated extraction technology, the amount of gas emitted into the zone was greatly reduced, while the risk of dangerous outbursts of coal and gas was lowered markedly. This exploration provides a new way to control for gas in working faces of coal mines with low permeability and risk of gas outbursts of single coal seams in the Jiaozuo mining area.

Calculating densities and viscosities of natural gas with a high content of C_(2+) to predict two-phase liquid-gas flow pattern

The paper is devoted to the two-phase flow simulation.The gas-condensate mixture flow in a horizontal pipe under high pressure is considered.The influence of the equation of state(EOS)choice for mixture properties modelling on the flow regime calculation results is studied for gas with high content of methane homologues.An analytical overview of the methods to predict the flow pattern is provided.Based on this analysis,two techniques are selected.For these techniques,values of density and viscosity for each phase are required.Density calculation for the gas phase is performed with Van der Waals based EOS.The propriate EOS is selected based on studies of calculation errors for test mixtures.Calculation of liquid phase density is done by means of Patela-Teja and Guo-Du equations,two different models are considered for viscosity estimation.The flow patterns of gas-condensate mixture in a range of temperatures and pressures are calculated and verified via probability map.The results of study allow to recommend the Brusilovsky EOS for calculation of densities for similar gas mixtures and make more rigorous flow regime evaluation.The probability map shows that for the chosen composition and parameters of media the flow pattern is mostly transitional between segregated and annular independent from EOS.

STUDY ON THE THRESHOLD GAS PRESSURE IN COAL AND GAS OUTBURST

Based on the statistical data of 26 outburst prone coal seams in China, this paper presents the relationship among the threshold gas pressure in coal and gas outburst and the volatile content and hardness of coal by mathematical statistics. The threshold value of gas pressure for outburst pmin in MPa may be calculated by formula Pmin =5(0. 1+0. 07Kf), where / is the hardness and V the volatile content (%) of a soft bed. In China, the value of Pmin of some outburst prone coal seams ranges from 0. 57 to 0. 1 MPa.

The construction of technical standard system for ultra deep and high sour gas fields in Northeast Sichuan

To deal with the exploitation difficulties of gas fields in Northeast Sichuan with deep marine strata, after researching the relative standards domestic and abroad extensively, summarizing and promoting the successful experiences and failure lessons of project construction technology application scientifically, Sinopec has established an integrated technical standard system for the exploration and development of ultra deep and high sour gas fields. The system consists of 51 enterprise standards and covers 7 professions including geophysical prospecting, drilling, drilling log, well logging, gas formation test and production, sour gas gathering and transferring system, and HSE (health,safety,environment). It guides and guarantees the safe, high-quality and high-efficiency project construction effectively by means of enhancing the engineering design criterion, recommending the data processing and interpretation methods, identifying the requirements of operation and field inspection and standardizing the application of technical equipments.

Evolution and application of in-seam drilling for gas drainage

The presence of seam gas in the form of methane or carbon dioxide presents a hazard to underground coal mining operations.In-seam drilling has been undertaken for the past three decades for gas drainage to reduce the risk of gas outburst and lower the concentrations of seam gas in the underground ventilation.The drilling practices have reflected the standards of the times and have evolved with the development of technology and equipment and the needs to provide a safe mining environment underground.Early practice was to adapt equipment from other felds,with rotary drilling being the only form of drilling available.This form of drainage allowed various levels of gas drainage coverage but with changing emphasis,research and development within the coal industry has created specifc equipment,technology and practices to accurately place in-seam boreholes to provide effcient and effective gas drainage.Research into gas content determination established a standard for the process and safe levels for mining operations to continue.Surveying technology improved from the wire-line,single-shot Eastman survey instruments which was time-dependent on borehole depth to electronic instruments located in the drill string which transmitted accurate survey data to the drilling crew without time delays.This allowed improved directional control and increased drilling rates.Directional drilling technology has now been established as the industry standard to provide effective gas drainage drilling.Exploration was identifed as an additional beneft with directional drilling as it has the ability to provide exploration data from long boreholes.The ability of the technology to provide safe and reliable means to investigate the need for inrush protection and water drainage ahead of mining has been established.Directional drilling technology has now been introduced to the Chinese coal industry for gas drainage through a practice of auditing,design,supply,training and ongoing support.Experienced drilling crews can offer site specifc gas drainage drilling services utilising the latest equipment and technology.

地面精确定位钻孔在矿井火灾抢险救灾中的应用

盐井一矿因采煤工作面火灾事故导致4个井筒井口全部封闭。为实现对井下火区高效快速灭火,防止发生因高瓦斯突出矿井火灾蔓延引发的瓦斯煤尘爆炸二次事故,并最终实现矿井安全启封,采用雪姆钻机施工,在井下火区高温火点地面对应位置施工了2个精确定位垂直钻孔,分别穿透采煤工作面上部采空区垮落带。地面钻孔现场施工过程中,实现精确定位、安全施工、成功下套管,经钻孔窥视和检测,确认施工到位。该应用可为地面大流量注液氮灭火和帷幕注浆封堵提供装备、技术和工艺保障方面的指导。

SDQ-73型深孔取样装置在松软高突煤层中的适用性研究

煤层瓦斯含量井下直接测定结果的准确性很大程度上取决于所取煤样的质量。针对松软高突煤层中取样问题的现状,展开了SDQ-73型深孔取样装置在松软高突煤层的适用性研究。通过在首山一矿二1煤层12050、12061工作面的井下试验,分别完成了SDQ-73取样适用性试验及孔口接粉取样试验,并对两种取样方法的测试结果进行对比分析,得出该深孔快速取样装置可实现在松软高突煤层中的深孔、定点、快速取样,且取样质量明显高于传统的孔口接粉取样,完全符合GB/T23250《煤层瓦斯含量井下直接测定方法》的取样要求。

高速公路长大隧道瓦斯综合防控措施

高瓦斯长大隧道施工难度大、风险高,瓦斯防治是其工程安全管控的重中之重。结合在建重庆渝广高速公路华蓥山隧道瓦斯段落的设计与施工情况,总结高瓦斯长大隧道施工所采取的地质预报、施工通风、信息化管理以及瓦斯抽采与引排等综合处理措施,供类似工程参考。

沙曲矿北翼风井揭过煤层瓦斯含量及瓦斯压力测定技术

沙曲煤矿属于高瓦斯突出矿井。北翼风井所要揭过的主要煤层为3+4#和5#厚煤层,为了保证风井揭煤的安全施工,必须准确掌握两层煤的瓦斯含量和瓦斯压力。测定结果为:3+4#煤层相对瓦斯含量为11.56 m3/t,5#煤层为14.74 m3/t;3+4#煤层瓦斯压力为1.5 MPa,5#煤层为2.4 MPa。结果表明这两层煤为高瓦斯突出煤层,要保障安全揭煤必须采取瓦斯抽放和卸压措施,满足防突细则后方可实施揭煤工程。

高突出危险煤层煤巷安全快速掘进综合防突技术

针对沙曲矿综掘工作面掘进过程中瓦斯频繁超限、易发生煤与瓦斯突出及掘进速度缓慢的难题,提出了深孔预抽、超前抽放钻孔和边掘边抽抽采瓦斯的综合防突技术。现场实践表明,该综合防突技术措施较好地消除了工作面的突出危险,巷道掘进速度提高1倍以上,实现了高瓦斯突出危险煤巷安全快速掘进,缓解了沙曲矿采掘衔接紧张的局面。

高压脉动注水提高瓦斯抽放技术的试验研究

指出了静压注水和动压注水在处理煤层瓦斯的缺陷,进行了高压脉动注水的工业性试验,分析了注水前后煤体水分含量、瓦斯涌出、突出预测、校检指标的情况,试验结果表明,煤层高压脉动注水能较好地防治煤与瓦斯突出。

The Anti-obesity Effect of Allium cepa L. leaves on High Fat Diet Induced Obesity in Male Wistar Rats

Background:Over the years,there has been research on the anti-obesity effect of the Allium cepa bulb,but a dearth of research was carried out on the leaves,which is consumed as vegetable salad and soup,hence this study was proposed.Objective:This study aims at investigating the effect of A.cepa leaves on high fat diet(HFD)induced obesity in male Wistar rats.Methods:Twenty-eight male Wistar rats were divided into four groups with seven rats each.Apart from Group 1(normal control which received normal pelleted diet),obesity was induced in 21 rats of Group 2 to 4 with HFD.Group 2,the obese control was administered with 100%HFD,while the diet for group 3 and 4 was supplemented with 10%and 20%A.cepa powdered leaves,respectively,for 28 days.Results:In the rats treated with 10%and 20%A.cepa,body weight,fat mass,blood glucose,total cholesterol,triglycerides,aspartate amino transferase,alanine amino transferase,creatinine and urea levels were reduced significantly(P<0.05)in comparison with the obese control group.The liver of the rats treated with 10%and 20%A.cepa leaves revealed small and few amounts of fat deposits in comparison with the obese control group,which revealed numerous and large deposits of fat.The kidney of the rats treated with 10%and 20%A.cepa leaves showed moderate and mild inflammation,respectively,in comparison with the obese control group which showed acute inflammation.The leaves of A.cepa had antioxidant properties and the presence of volatile compounds with anti-obesity properties in A.cepa were identified using gas chromatography-mass spectrometry(GC-MS).Conclusion:A.cepa leaves had weight-loss effect in that it decreased body weight,fat mass,glucose and lipid levels including fat deposits in the liver.