Effect of aeration on fast gas pressure tests

Given the problem of the long time required for testing gas pressure, we propose a fast-test method in which we used a technique of fast borehole sealing and air replenishing. Based on the characteristics of gas emission from boreholes to be tested, we built a theoretical model for calculating parameters during the process of increasing natural pressure and aeration. Using this model, we investigated the effect of different aeration conditions on velocity of pressure tests. The result shows that: 1) aerating air into boreholes can speed up gas pressure tests and 2) the more similar the pressure of the aerated air to the original gas pressure, the smaller the gas volume absorbed by coal and the shorter the time needed in pressure test. A case study in the Lu'an mining area shows that the time needed for gas pressure test is only 4 h using our method of aeration and 29 h under conditions of increasing natural pressure, saving time by 86.2%. This case study also indicates that, by using the aeration method, only one hour is needed for gas pressure to reach a stable state, which breaks the record of the shortest time needed for gas pressure tests in China.     

Dynamic leakage mechanism of gas drainage borehole and engineering application

Borehole leakage not only affects the gas drainage effect but also presents considerable risk to human security. For the research on the leakage mechanism of gas drainage borehole, the rheological and visco-elastic-plastic characteristics were considered to establish the mechanical model of coal mass around borehole, which is used to analyze the leakage mechanism and deduce the dynamic leakage model. On the basis of the real coal seam conditions, the variation rules of the stress, leakage ring, and air leakage amount were analyzed through numerical simulation, and the influence factors of air leakage amount were also investigated to provide the theoretical basis for the sealing technology. Results show that the air leakage amount of borehole is inversely proportional to the increase in supporting stress and sealing length, and directly correlated with the increase in borehole radius and softening modulus. Using theoretical analysis, we design a novel active supporting sealing technology that can use grouting material to seal the fractures to reduce the leakage channels and also provide supporting stress to prevent borehole deformation. The engineering test results indicate that the average gas concentration with the novel active supporting sealing technology is increased by 162.12% than that of traditional polyurethane sealing method. Therefore, this technology not only effectively resolves borehole leakage but also significantly improves the gas drainage effect.     

煤层群煤与瓦斯安全高效共采体系及应用

提出了高瓦斯煤层群煤与瓦斯安全高效共采的概念：在煤层群开采条件下，首先开采瓦斯含量低、无突出危险的首采煤层，利用其采动影响使处在其上部和下部的煤层卸压，煤层透气性成百倍地增加，从而形成高效的瓦斯抽采条件．同时进行的卸压瓦斯高效抽采既解决了由卸压煤层向首采煤层涌出瓦斯问题，保障首采煤层实现安全高效开采，又大幅度地降低了卸压煤层的瓦斯含量，消除了煤与瓦斯突出危险性，为在卸压煤层内实施快速掘进与高效采煤方法提供了安全保障，从而实现了瓦斯与煤炭两种资源的安全高效共采．文中介绍了针对不同卸压瓦斯流动特点的近程、中程和远程卸压瓦斯抽采方法及工程应用实践，最后对高瓦斯煤层群煤与瓦斯安全高效共采体系的应用前景进行了分析．     

福建省无烟煤低瓦斯原因分析

从原生沉积、后期改造、煤层的煤岩特征等方面分析了福建省无烟煤矿井高变质无烟煤瓦斯涌出的原因与预防预测的方法。     

三相泡沫密封性能的实验研究

本文以表面物理化学为基础,探讨了泡沫流体的稳定性及其密封性能,得出了气液两相泡沫流体可作为封堵裂隙的介质,并且只要加入适量的固相填充剂,其密封性能可显著提高的结论,从而为煤层瓦斯压力测定的封孔技术,尤其是煤巷和松软岩层的封孔提供了一种较为理想的材料。研究工作表明,三相泡沫封孔技术是一项具有广泛实用前景的新技术。     

煤矿深部开采煤层气含量计算的解析法

针对矿井深部煤层中地温和地应力梯度对煤的孔隙率和煤层渗透率的影响以及煤的吸附特性参数受温度影响变化的特点 ,在矿井深部煤层气压力解析算法的基础上 ,提出了考虑地温和地应力梯度影响的煤层气含量计算的新方法 .现场实测煤层气压力和理论计算的煤层气压力及煤层气含量的对比分析表明 ,该计算方法能较准确地反映现场实测结果 ,从理论上进一步完善了矿井深部煤层煤层气含量的计算方法 ,并对其分布规律的预测具有重要理论价值 .     

软煤应变强度硬化冲击灾变

煤与瓦斯突出软煤层不具冲击倾向性,但在深部开采中却发生了软煤层冲击灾变动力现象.为探索软煤冲击灾变的成因,通过文献研究和工程案例实证分析,证明了软煤层冲击灾变现象的客观存在;通过煤样无侧限单轴压缩试验和冲击倾向性测定,得知试验煤样无冲击倾向性,极限载荷后单调应变强度软化;模拟工程背景现场与掘进工作面和采煤工作面中部相同的边界约束和加载条件,开展单自由度边界承压试验,考察灾变全程应力、应变、声发射特征,研究软煤冲击灾变机理.结果表明:单自由度边界条件下加载,3个煤样均出现应变强度软化-硬化-灾变过程,甚至反复软化-硬化;经应变强度硬化,灾变前煤样抗压强度均超过冲击倾向性的阈值条件;定义了应变强度软化、应变强度硬化系数,灾变前应变强度硬化系数分别为1. 26,1. 53,2. 25,应变强度硬化程度比较显著;软煤在单自由度约束条件下承压,应变硬化达到煤样冲击破坏强度条件时,可发生类似硬煤的冲击灾变,合理解释了现场软煤层冲击灾变的成因.深部高应力条件下,煤与瓦斯突出软煤掘进和开采,要对应变强度硬化导致煤层冲击灾变引起重视;工程上,这种冲击灾变的强度一般不高,但其可诱导煤与瓦斯突出或瓦斯异常涌出,危害性很高.     

Strata movement and stress evolution when mining two overlapping panels affected by hard stratum

Mining causes stress redistribution and stratum movement. In this paper, a numerical model was built according to the geological conditions in the 12 th coal mine in Pingdingshan city to study the strata movement and the evolution of stress when mining two overlapping longwall panels, named panels#14 and #15. The strata close to the mined panel move directly towards the gob, while the strata that are farther away swing back and forth during the mining process. The directed movement and swinging can break the transverse boreholes for gas extraction; a surface borehole should not be within the range of directional movement. The stress evolution suggested that the mining of the lower panel #15 after the upper panel #14 would further increase the de-stressed range, while the stress concentration around the mined panel would be increased. Hard strata usually carry a greater stress than adjacent rocks and soft coal seams. The stress in a hard stratum increases greatly, and the stress decreases greatly in the coal seams below the hard stratum. This study supplies a reference for similar coal mines and is useful for determining the de-stressed range and transverse borehole arrangement for gas extraction.     

近距离突出煤层群瓦斯治理技术优化的研究

近距离突出煤层群工作面受上下邻近煤层卸压瓦斯的影响,致使回采工作面瓦斯涌出量大、工作面回风隅角及回风巷中的甲烷传感器频繁报警,瓦斯治理消耗大量的人力、物力和时间,严重制约了矿井的安全生产。通过对几种瓦斯治理方案进行分析论证,得出将整个煤层群作为一个治理单元,统筹考虑,将煤层厚度、瓦斯含量相对较小的弱突出煤层作为关键保护层,配合打钻进行立体式抽采,实现上下递进保护,最大限度地抽采邻近煤层的卸压瓦斯的方案。现场实践结果表明,保护层工作面在回采期间瓦斯抽采率高达90%以上,回风隅角瓦斯浓度降至0.6%以下,回风巷风流中瓦斯浓度降至0.2%以下,工作面月平均回采长度由原来的120 m提高至200 m。同时,从根本上解决了被保护层工作面回采期间瓦斯带来的安全威胁。     

Gas seepage equation of deep mined coal seams and its application

In order to obtain a gas seepage law of deep mined coal seams, according to the properties of eoalbed methane seepage in in-situ stress and geothermal temperature fields, the gas seepage equation of deep mined coal seams with the Klinkenberg effect was obtained by confirming the coalbed methane permeability in in-situ stress and geothermal temperature fields. Aimed at the condition in which the coal seams have or do not have an outcrop and outlet on the ground, the application of the gas seepage equation of deep mined coal seams in in-situ stress and geothermal temperature fields on the gas pressure calculation of deep mined coal seams was investigated. The comparison between calculated and measured results indicates that the calculation method of gas pressure, based on the gas seepage equation of deep mined coal seams in in-situ stress and geothermal temperature fields can accurately be identical with the measured values and theoretically perfect the calculation method of gas pressure of deep mined coal seams.     

承压煤岩低气压渗流灾变

为探索含低压瓦斯煤层的瓦斯异常涌出灾变成因与机理,对目前该领域的文献进行了分析与总结,并通过工程案例实证分析,证明了此种灾变的存在;在流固耦合实验系统上,按背景工程约束与加载条件开展含低气压煤样承压物理试验,得到了灾变全程应力-声发射-流量实验数据及试样外表破坏情况;用UDEC,按背景工程边界与加载条件开展气-固耦合离散元数值试验,得到了灾变全程应力-应变--流速-位移速率等实验数据及试样内部破裂情况.研究结果表明:3种研究方法获得了一致性较高的结果,0.4 MPa气体压力下,煤层承压过程应力-煤-气耦合作用,可以导致发生喷出气体的灾变,在煤矿现场多表现为瓦斯异常涌出超限;在单自由度边界条件下施加单向压载,承压煤岩弹性变形前期,气体沿原生裂隙和孔隙呈常速稳态渗流;弹性变形后期,原生裂隙和孔隙被压密,气体呈减速稳态渗流;屈服阶段,扩容新生裂隙产生,气体呈加速非稳态渗流;达到极限荷载或峰后不久,发生气体喷出灾变;采、掘作业面正常通风条件下,气流瓦斯浓度持续降低,是煤层发生瓦斯异常涌出的警示信息,应引起高度重视.     

煤巷卸压带及其在煤和瓦斯突出危险性预测中的应用

本文应用岩体力学,弹塑性力学等有关知识,探讨了煤巷卸压带对煤和瓦斯突出的作用机理,建立了煤层界面的应力分布状态方程以及煤巷卸压带和地应力,瓦斯压力,煤强度之间的关系式,并分析了煤巷卸压带中煤体稳定性的条件。研究工作表明:煤巷卸压带中的瓦斯压力,煤体透气性值可以作为突出危险性预测指标和防突措施效果检验的敏感指标。最后,利用自行设计的泡沫封孔测压仪对现场进行了突出危险性预测和防突措施效果检验,得到了十分满意的结果。     

Coal seam drainage enhancement using borehole presplitting basting technology——A case study in Huainan

Xinji No. 2 underground coal mine extracts the coal seams #4 and #5. These two seams are highly gassy and gas drainage is required to control mine gas emission and reduce outburst risk. Because the seam permeability coefficient is very low and around 0.1 m~2/(MPa~2·d), a number of technologies have been trialled to enhance the seam permeability prior to gas drainage. Of these technologies trialled, the deep borehole presplitting blasting technology has been proven to be quite effective in increasing permeability. In Xinji No. 2 mine it doubled or sometimes tripled gas drainage volume. This paper describes the technology, its application in the enhancement of seam permeability in Xinji No. 2 coal mine, and its effect on gas drainage performance.     

上邻近层残存瓦斯压力的理论与应用

本文根据岩体力学与采场覆岩移动原理,探讨了煤层原始瓦斯压力、采场开采技术参数、覆岩岩性、煤层倾角等对上邻近层残存瓦斯压力的影响。指出了采场覆岩法向裂缝宽度是影响上邻近层残存瓦斯压力的关键因素,推导出了能够反映上述影响的上邻近层残存瓦斯压力计算公式。经过实际应用证明比已有的其它公式理论性强、精度高。据此还可以计算上邻近层瓦斯涌出量、可抽放瓦斯量及考察解放层的解放效果等。     

吐哈盆地沙尔湖地区煤层气钻完井适用技术探讨

在剖析美国圣胡安盆地煤层气空气钻井、裸眼洞穴完井技术及优势的基础上,确定了低煤阶煤层气钻井及裸眼洞穴完井的煤储层条件等,并以吐哈盆地沙尔湖地区低煤阶煤层气为主要研究对象,利用类比法及地质统计法,具体分析了吐哈盆地沙尔湖地区的煤储层厚度、含气量、渗透率、井壁稳定性及储层压力条件等．研究表明,沙尔湖地区煤层厚度大,储层物性好,井壁稳定性好,可采用低成本空气钻井及裸眼完井技术提高钻井效率,保护煤储层,提高煤层气采收率．     

Technology and application of pressure relief and permeability increase by jointly drilling and slotting coal

Difficulties with soft coal seams having a high gas content and high stress levels can be addressed by a technology of pressure relief and permeability increase. Slotting the seam by auxiliary drilling with a water jet that breaks the coal and slots the coal seam during the process of retreat drilling achieves pressure relief and permeability increase. Improved efficiency of gas extraction from a field test, high gas coal seam was observed. Investigating the theory of pressure relief and permeability increase required analyzing the characteristics of the double power slotting process and the effects of coal pressure relief and permeability increase. The influence of confining pressure on coal physical properties was examined by using FLAC3D software code to simulate changes of coal stress within the tool destruction area. The double power joint drilling method was modeled. Field experiments were performed and the effects are analyzed. This research shows that there is an “islanding effect” in front of the joint double power drill and slotting equipment. The failure strength of the coal seam is substantially reduced within the tool destruction area. Drilling depths are increased by 72% and the diameter of the borehole is increased by 30%. The amount of powdered coal extracted from the drill head increases by 17 times when using the new method. A 30 day total flow measurement from the double power drilled and slotted bores showed that gas extraction increased by 1.3 times compared to the standard drilled bores. Gas concentrations increased from 30% to 60% and were more stable so the overall extraction efficiency increased by a factor of two times.     

中国采煤工作面瓦斯涌出规律及其控制研究

将采煤工作面瓦斯来源划分为煤壁、采落煤和采空区３部分,并给出了各部分瓦斯涌出量的计算公式,研究了回采过程,煤层群不同的开采顺序以及厚煤层分层开采时的瓦斯涌出 述了中国煤矿采矿工作面采用不同的通风系统、脉冲通风以及瓦斯抽放等控制瓦斯涌出的原理与技术的新成果,介绍了瓦斯涌出量达１５０ｍ＾３／ｍｉｎ的综采放顶煤工作面瓦斯控制技术实例。     

高瓦斯煤层开采的新思路及待研究的主要问题

提出了解决高瓦斯煤层开采的新思路：在一个密闭的空间中实现瓦斯与煤同采,使采煤工作在一个即能密封又能开放的空间中进行;当采煤机械高速运行、瓦斯涌出量很大量,回采工作面上下巷道密闭,使回采工作空间的瓦斯浓度保持在30％以上,完全处于不能产生爆炸的环境中,使机械设备的效率能够得到充分发挥,实现高产高效安全生产的目标;当工作面出现故障、必须停采处理时,打开工作面上下巷道的风门,恢复通风。煤与瓦斯同采是高瓦斯煤层的一项全新的开采方式,需要对其主要问题进行深入的研究。     

大口径瓦斯抽排钻孔套管稳定性分析

为了研究大口径抽排钻孔套管的稳定性,在总结套管抗挤强度计算方法的基础上,分析了地层流体压力、固管质量、表土层沉降、爆破震动及巷道开挖引起的围岩次生应力等因素对大口径瓦斯抽排钻孔套管的稳定性的影响。结果表明：表土层沉降产生的负摩阻力增加了套管轴向应力,进而减小了套管的抗挤强度;爆破震动产生的应力波的衰减特性与套管距炮心的距离有关,当套管处的径向应力峰值大于套管的动抗挤强度时,套管发生失稳;巷道开挖产生的围岩次生径向应力值一般小于原岩径向应力值,对套管稳定性的影响较小。     

Dynamic development characteristics of amounts of gas and levels of pressure in the Pan-1 coal mine of Huainan

The Pan-1 coal mine located in Huainan municipality, Anhui province, is abundant in coal resources. In order to discover the natural conditions of gas in its coal seams, we inverted the burial history of these coal seams using the software of Easy%Ro method and simulated the development process of gas volumes and pressure of the major coal seams using CBMHistory Simulation Software. Our analysis shows that the devolution of gas volumes and levels of pressure can be divided into four stages: I.e., a biogas stage (P1-P3), a pyrolysis gas stage (T1-T2), an active gas enrichment stage (T3-K1) and a gas dissipating stage (K2-present). Cur-rently, the average amounts of gas and gas pressure in coal seams Nos. 13-1,11-2 and 8 of the Pan-1 coal mine are 8.18 m3/t and 2.20 Mpa; 3.89 m3/t and 2.47 Mpa and 6.35 m3/t and 2.89 Mpa, respectively. This agrees very well with current mining data.