Methane is a safety concern in underground coal mines. In its explosive range of 5%–15% in air, methane can be easily ignited in the presence of an ignition source to create a violent methane explosion. Ventilation is the main control mechanism to keep methane levels below the explosive limit. However, effectiveness of a ventilation system is dependent on multiple factors such as geological conditions, mine design, and reservoir properties of the coal seam. Without good knowledge of these factors, methane emissions can still create a localized zone of high methane concentrations in areas of low air velocities and quantities, and can render the ventilation system ineffective. Among those factors controlling methane emissions, reservoir properties of the coal seam are particularly important, especially if the mined seam is the main source of methane, with the properties of the coal controlling methane storage and emission potential during mining operations. If not diluted by ventilation air, methane in coal seams is not only a hazard to mining safety, but an important concern from an environmental point of view as a greenhouse gas. Capturing and utilizing methane from active mines will both improve mining safety and decrease greenhouse gas emissions, and will provide an additional energy source that otherwise will be lost. A similar concept is also true for sealed workings and abandoned mines, as methane accumulating in these areas can be detrimental for active mines operating nearby in the event of gas migration between the workings. Methane accumulations can also be used for energy production if captured. Methane capture and utilization technologies have been demonstrated and are being successfully used mainly in the US and in Australia, and in other countries around the world [1]. There are various geological and operational factors affecting a mine's methane emissions during coal extraction. Therefore, a relative term called “specific emissions” is used as a lumped parameter to designate the gassiness of a mine. Specific emissions are the amount of methane generated per unit amount of coal that is mined [2], and this quantity is generally used to determine the degasification and ventilation needs of a particular operation. It has been shown for Australian mines that the amount of mine emissions exceeded the gas content of coal by a factor of 4 [3]. This ratio is due to the fact that methane that leads to specific emissions of a mine may be generated from the mined coal itself, and also may originate from overlying and underlying strata if they are gassy. In addition, the quantity may change based on variations in operational parameters. While gas content of a coal seam is one of the key data impacting in-place coalbed methane resource estimations, it is not the only parameter important to coalbed and coal mine methane assessments. Coalbed methane and coal mine methane production potentials are affected by coal reservoir properties, mining conditions, and coal productions. This is one reason why coal production is used as a major parameter in most empirical models of methane emissions, and why coal production should be reevaluated under ventilation constraints [4]. Degasification of methane from coal seams and from adjacent strata which is a common practice, especially for long wall mines operating in gassy coal seams. Degasification can be used for controlling methane emissions prior to and during mining by reducing emissions into the ventilation system. Reducing the gas content of coal seams either by using vertical boreholes drilled from the surface, using horizontal boreholes drilled from adjacent entries, or by drilling directional boreholes from the surface, are effective ways to control methane emissions [5–7]. Multi-lateral horizontal boreholes are drilled from a single drilling location in the head gate entry to reduce the gas content of the coal volume in the panel area before mining. Boreholes drilled from various locations in the main entries extend into multiple panel areas to drain the gas in a larger area before mining commences. Multiple wells can be connected for transportation of the gas within the mine. Numerous studies have demonstrated that under continuous and uniform coal seam conditions, the performance of the boreholes and their effectiveness at reducing emissions can be predicted by modeling techniques [8,9]. Regardless of whether methane emissions can be controlled by ventilation alone or by any pre-mining degasification method, fluid-flow and fluid-storage related properties of the coal seam have to be known. Coal reservoir properties of the mined seam are not only important for methane emissions into the ventilation system but also for the success of degasification operations. Effects of various mining and coal reservoir properties on potential emissions into entries during development mining of coal seams are discussed in [10,11 ] using dynamic reservoir simulation, where as the effects of water jetting on decreasing outbursts and improving entry development rate is discussed in [12]. If there are wells operating in the mining area for degasification purposes, then properties of mined coal seams can be determined or estimated using different techniques, including laboratory analyses [13,14], geophysical logs [15], and well testing methods [16]. History matching of pressure and production behavior of these wells using reservoir simulation can also estimate properties of the coal seam being degasified. Each of these methods has advantages and disadvantages. Although laboratory analyses can be informative, it is difficult to reproduce in-situ conditions in the laboratory. Therefore, not all data measured in the laboratory may be representative of in-situ conditions. Geophysical methods can be effective to measure some of the reservoir properties pertinent to porous rocks and coal seams. However, permeability should be inferred from other measurements. On the other hand, well testing techniques can produce data that are more representative of in-situ conditions, but these methods are complicated, expensive, and sometimes require lengthy times to gather and process the information. In addition, geophysical logging, well testing, and production/pressure history matching techniques all require wellbores that are either producing or that can be used in reservoir testing. Coal mining areas may not necessarily have boreholes that are equipped for well testing and history matching purposes. Although not every mining area is expected to have degasification wells that make the history matching technique applicable, all coal mines must measure airflows and methane concentrations regularly at specific locations in the ventilation network. Thus in this study, an alternative approach is proposed to predict coal seam reservoir properties through integration of ventilation data measured in entries with numerical reservoir simulation. Because all coal mining operations must make ventilation measurements at specific locations, these types of data are always available. To our knowledge, this approach and the history matching of ventilation air data have not previously been tried and demonstrated in the literature for estimating coal seam reservoir properties.

中文翻译：

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使用储层模拟和矿井通风测量来估计煤层特性

甲烷是地下煤矿的安全问题。甲烷在空气中的爆炸范围为 5%~15%，在有火源的情况下很容易被点燃，产生剧烈的甲烷爆炸。通风是将甲烷水平保持在爆炸极限以下的主要控制机制。然而，通风系统的有效性取决于多种因素，例如地质条件、矿山设计和煤层的储层特性。如果对这些因素没有很好的了解，甲烷排放仍然会在低空气速度和数量的地区产生一个高甲烷浓度的局部区域，并可能导致通风系统无效。在控制甲烷排放的这些因素中，煤层的储层特性尤为重要，特别是如果开采的煤层是甲烷的主要来源，煤的特性可以控制采矿作业期间的甲烷储存和排放潜力。如果不通过通风空气稀释，煤层中的甲烷不仅会危害采矿安全，而且作为温室气体从环境角度来看也是一个重要问题。从活跃矿山中捕获和利用甲烷将提高采矿安全并减少温室气体排放，并将提供额外的能源，否则将失去。类似的概念也适用于密封矿井和废弃矿井，因为如果矿井之间发生气体迁移，这些区域中积聚的甲烷可能会对附近运营的活跃矿井造成不利影响。如果被捕获，甲烷积累也可用于能源生产。甲烷捕集和利用技术已被证明并正在成功应用，主要在美国和澳大利亚以及世界其他国家[1]。有多种地质和操作因素会影响煤矿开采过程中的甲烷排放。因此，使用称为“特定排放量”的相对术语作为集总参数来指定矿井的含气量。特定排放量是每单位开采煤量产生的甲烷量 [2]，该量通常用于确定特定操作的脱气和通风需求。澳大利亚矿山的研究表明，矿山排放量超过煤的瓦斯含量 4 倍 [3]。该比率是由于导致矿山特定排放的甲烷可能来自开采的煤炭本身，也可能来自上覆和下伏地层（如果它们是含气的）。此外，数量可能会根据操作参数的变化而变化。虽然煤层的瓦斯含量是影响就地煤层气资源估算的关键数据之一，但它并不是对煤层和煤矿瓦斯评估很重要的唯一参数。煤层气和煤矿瓦斯生产潜力受煤储层性质、开采条件和煤炭产量的影响。这就是为什么在大多数甲烷排放经验模型中将煤炭产量用作主要参数的原因之一，也是为什么应在通风限制下重新评估煤炭产量的原因之一 [4]。对煤层和相邻地层中的甲烷进行脱气，这是一种常见的做法，特别是对于在瓦斯煤层中运行的长壁矿。通过减少进入通风系统的排放，脱气可用于控制采矿前和采矿期间的甲烷排放。通过使用从地表钻孔的垂直钻孔、使用从相邻入口钻孔的水平钻孔或通过从地表钻孔定向钻孔来降低煤层的瓦斯含量是控制甲烷排放的有效方法[5-7]。多侧水平钻孔从入口闸门入口的单个钻孔位置钻孔，以减少开采前面板区煤体积的含气量。从主入口的不同位置钻出的钻孔延伸到多个面板区域，以便在开始开采之前将气体排放到更大的区域。可以连接多口井来输送矿井内的气体。大量研究表明，在连续且均匀的煤层条件下，钻孔的性能及其减少排放的有效性可以通过建模技术进行预测 [8,9]。无论是单独通过通风还是通过任何开采前脱气方法控制甲烷排放，都必须了解煤层的流体流动和流体存储相关特性。开采煤层的煤储层特性不仅对进入通风系统的甲烷排放很重要，而且对脱气操作的成功也很重要。[10,11] 中使用动态储层模拟讨论了各种采矿和煤储层特性对煤层开发开采过程中潜在排放到入口的影响，其中讨论了喷水对减少突出和提高入口开发速度的影响[12]。如果在矿区有用于脱气目的的井，则可以使用不同的技术来确定或估计开采煤层的特性，包括实验室分析 [13,14]、地球物理测井 [15] 和试井方法 [16] . 使用油藏模拟对这些井的压力和生产行为进行历史匹配也可以估计正在脱气的煤层的特性。这些方法中的每一种都有优点和缺点。虽然实验室分析可以提供信息，很难在实验室中重现原位条件。因此，并非所有在实验室中测量的数据都可以代表现场条件。地球物理方法可以有效地测量与多孔岩石和煤层相关的一些储层特性。然而，渗透率应该从其他测量中推断出来。另一方面，试井技术可以产生更能代表现场条件的数据，但这些方法复杂、昂贵，有时需要很长时间来收集和处理信息。此外，地球物理测井、试井和生产/压力历史匹配技术都需要正在生产或可用于储层测试的井眼。煤矿区可能不一定有为试井和历史匹配目的而配备的钻孔。尽管并非每个矿区都有望拥有使历史匹配技术适用的脱气井，但所有煤矿都必须定期测量通风网络中特定位置的气流和甲烷浓度。因此，在本研究中，提出了一种替代方法，通过将条目中测量的通风数据与数值储层模拟相结合来预测煤层储层特性。由于所有煤矿开采作业都必须在特定位置进行通风测量，因此这些类型的数据始终可用。据我们所知，