Understanding of mineral change mechanisms in coal mine groundwater reservoir and their influences on effluent water quality:a experimental study

This paper presents results of an experimental study to characterize the law of mineral change of fallen rock in coal mine groundwater reservoir ant its influence on water quality.The minerals of the underground reservoir of Daliuta Coal Mine is taken as the research object.Simulation experiments were designed and conducted to simulate water–rock action in the laboratory.The mineral composition was analyzed by X-ray diffractometer(XRD),the surface morphology of the mineral was analyzed by scanning electron microscope(SEM),and the specific surface area,total pore volume and average pore diameter of the mineral were measured by fast specific surface/pore analyzer(BET).The experimental results show that the sandstone and mudstone in the groundwater reservoir of Daliuta Coal Mine account for 70%and 30%,respectively.The pore diameter is 15.62–17.55 nm,and pore volume is 0.035 cc/g.Its pore structure is a key factor in the occurrence of water–rock interaction.According to the water–rock simulation experiment,the quartz content before the water–rock action is about 34.28%,the albite is about 21.84%,the feldspar is about 17.48%,and the kaolinite is about 8.00%.After the water–rock action,they are 36.14%,17.78%,11.62%,and 16.75%,respectively.The content of albite and orthoclase is reduced while the content of kaolinite is increased,that is,the Na+content becomes higher,and the Ca2+and Mg2+contents become lower.This research builds a good theoretical foundation for revealing the role of water and rock in underground coal reservoirs.

Predicting the height of water-flow fractured zone during coal mining under the Xiaolangdi Reservoir

It is very important to determine the extent of the fractured zone through which water can flow before coal mining under the water bodies.This paper deals with methods to obtain information about overburden rock failure and the development of the fractured zone while coal mining in Xin'an Coal Mine.The risk of water inrush in this mine is great because 40%of the mining area is under the Xiaolangdi reservoir.Numerical simulations combined with geophysical methods were used in this paper to obtain the development law of the fractured zone under different mining conditions.The comprehensive geophysical method described in this paper has been demonstrated to accurately predict the height of the water-flow fractured zone.Results from the new model, which created from the results of numerical simulations and field measurements,were successfully used for making decisions in the Xin'an Coal Mine when mining under the Xiaolangdi Reservoir.Industrial scale experiments at the number 11201,14141 and 14191 working faces were safely carried out.These achievements provide a successful background for the evaluation and application of coal mining under large reservoirs.

An exsitu underground coal gasification experiment with a siderite interlayer:course of the process,production gas,temperatures and energy efficiency

A 72-h ex situ hard coal gasification test in one large block of coal was carried out.The gasifying agent was oxygen with a constant flow rate of 4.5 m^(3)/h.The surroundings of coal were simulated with wet sand with 11%moisture content.A 2-cm interlayer of siderite was placed in the horizontal cut of the coal block.As a result of this process,gas with an average flow rate of 12.46 m^(3)/h was produced.No direct influence of siderite on the gasification process was observed;however,measurements of CO_(2)content in the siderite interlayer before and after the process allow to determine the location of high-temperature zones in the reactor.The greatest influence on the efficiency of the gasification process was exerted by water contained in wet sand.At the high temperature that prevailed in the reactor,this water evaporated and reacted with the incandescent coal,producing hydrogen and carbon monoxide.This reaction contributes to the relatively high calorific value of the resulting process gas,averaging 9.41 MJ/kmol,and to the high energy efficiency of the whole gasification process,which amounts to approximately 70%.

Underground coal gasification and its strategic significance to the development of natural gas industry in China

Based on the present situation and trend of underground coal gasification in China and overseas, this article puts forward the basic concept, mechanism and mode of underground coal gasification, and presents the challenges, development potential and development path now faced. In China, underground coal gasification which is in accord with the clean utilization of coal can produce "artificial gas", which provides a new strategic approach to supply methane and hydrogen with Chinese characteristics before new energy sources offer large-scale supply. Coal measure strata in oil-bearing basins are developed in China, with 3.77 trillion tons coal reserves for the buried depth of 1000-3 000 m. It is initially expected that the amount of natural gas resources from underground coal gasification to be 272-332 trillion cubic meters, which are about triple the sum of conventional natural gas, or equivalent to the total unconventional natural gas resources. According to the differences of coal reaction mechanism and product composition of underground coal gasification, the underground coal gasification can be divided into three development modes, hydrogen-rich in shallow, methane-rich in medium and deep,supercritical hydrogen-rich in deep. Beyond the scope of underground mining of coal enterprises, petroleum and petrochemical enterprises can take their own integration advantages of technologies, pipeline, market and so on, to develop underground coal gasification business based on their different needs and technical maturity, to effectively exploit a large amount of coal resources cleanly and to alleviate the tight supply of natural gas. It can also be combined with using the produced hydrogen in nearby area and the CO_2 flooding and storage in adjacent oil areas to create a demonstration zone for net zero emissions of petroleum and petrochemical recycling economy. It is significant for reserving resources and technologies for the coming "hydrogen economy" era, and opening up a new path for China's "clean, low carbon, safe and efficient" modern energy system construction.

Double Fire-Two Stage Method and Parameter Calculation of Underground Coal Gasification

The double fire two stage method of underground coal gasification was suggested. On the basis of material balance, the ideal gasification parameters were calculated, and the field test process was briefly introduced. In addition, the cause for a middle to a high heat value of water gas was described. And the reasonableness and feasiblity of the method was proved, showing that the double fire two stage gasification is an important technique for commercialized production.

Evaluation method of underground water storage space and thermal reservoir model in abandoned mine

A large number of mines are closed or abandoned every year in China.Geothermal utilization is one of the important ways to efficiently reuse underground resources in abandoned mines.How to calculate the volume and distribution of underground water storage space is the key to accurately evaluate the sustainable geothermal production in abandoned mines.In this paper,according to the multi-scale characteristics of the underground space in abandoned mine,the flow and heat transfer equations in the multi-scale space are sorted out systematically,and the calculation methods of different secondary space volumes are derived in detail.Taking Jiahe abandoned mine as the background,the volume and distribution of underground secondary space are calculated,and three heat storage evaluation models considering different water storage spaces are established by using COMSOL.The simulation results show that there are great differences among different models,and the results of the equivalent porous media model considering the multi-scale space are most consistent with the reality.Sensitivity analyses of key parameters model results indicated that the heat production is closely related to not only the recharge flow rate but also the recharge temperature and operating time.Furthermore,the energy saving and emission reduction benefits of geothermal utilization in abandoned mines are calculated,the results show that geothermal utilization of abandoned mines can effectively reduce energy consumption and CO_(2)emissions,and it has great economic benefits.

基于ADINA的地下水库抽水效应数值模拟

随着经济的发展,地下水库抽水引起的建筑物周围地面沉降和地基沉降问题,已成为重大环境灾害问题之一。本文分析了沉降产生的机理,借助有限元软件ADINA模拟了地下水库抽水对沉降的影响,分别模拟了不同流量的单井抽水对沉降的影响,不同抽水井数(单井、双井、三井)抽水对沉降的影响,以某工程实例进行了模拟,得出以下结论:沉降量与抽水流量、抽水井点数、井点间距等有关。抽水流量越大,孔隙水压力就越大,地下水库沉降量也越大;抽水井点数越多,沉降量也越大,井点间距越大,沉降量越小。

Influence of liquid water on coalbed methane adsorption:An experimental research on coal reservoirs in the south of Qinshui Basin

Using Isothermal Adsorption/Desorption System Model IS-100 and Electrohydraulic Servo Rock System Model MTS815 as the main apparatuses and collecting samples from the major coal reservoirs in the south of Qinshui Basin, a hot point region of coalbed methane exploration, the paper carries out systematical comparisons of the isothermal adsorption experimental data for injection water coal samples, equilibrium moisture samples and dry coal samples, probes and establishes an experimental method of injection water coal sample preparation and isothermal experiment to simulate real reservoir conditions, and then summaries the experimental regulations and discusses the mechanism of liquid water influencing coal methane adsorption. Results of the experiment indicate that: The Langmuir volume of injection water coal samples is notably larger than that of equilibrium moisture samples, as well as larger than or equivalent to that of dry coal samples; the Langmuir pressure of injection water coal samples is the highest, the next is equilibrium moisture samples, while the dry samples is the lowest, of which the experimental results of injection water samples to simulate real reservoir conditions are more close to the fact. Under the conditions of in-position reservoirs, liquid water in coals has evident influence on methane adsorption ability of coal matrix, which can increase the adsorbability of coal and make the adsorption regulation fit to Langmuir model better. Its major reason is the increase of wetting coal matrix adsorbability. The above experimental results overthrow the conventional cognition that liquid water has no influence on coalbed methane adsorption, which may lead to an improvement of the coalbed methane isothermal adsorption experimental method and of the reliability of coalbed methane resource evaluation and prediction.

A study on the flowability of gas displacing water in low-permeability coal reservoir based on NMR technology

Flowability of gas and water through low-permeability coal plays crucial roles in coalbed methane(CBM)recovery from coal reservoirs.To better understand this phenomenon,experiments examining the displacement of water by gas under different displacement pressures were systematically carried out based on nuclear magnetic resonance(NMR)technology using low-permeability coal samples of medium-high coal rank from Yunnan and Guizhou,China.The results reveal that both the residual water content(W_(r))and residual water saturation(S_(r))of coal gradually decrease as the displacement pressure(P)decreases.When P is 0-2 MPa,the decline rates of W_(r) and S_(r) are fastest,beyond which they slow down gradually.Coal samples with higher permeability exhibit higher water flowability and larger decreases in W_(r) and S_(r).Compared with medium-rank coal,high-rank coal shows weaker fluidity and a higher proportion of irreducible water.The relationship between P and the cumulative displaced water content(W_(c))can be described by a Langmuir-like equation,W_(c)=WLP/(PL+P),showing an increase in W_(c) in coal with an increase in P.In the low-pressure stage from 0 to 2 MPa,W_(c) increases most rapidly,while in the high-pressure stage(P>2 MPa),W_(c) tends to be stable.The minimum pore diameter(d′)at which water can be displaced under different displacement pressures was also calibrated.The d′value decreases as P increases in a power relationship;i.e.,d′the coal gradually decreases with the gradual increase in P.Furthermore,the d′values of most of the coal samples are close to 20 nm under a P of 10 MPa.

王洼煤矿水库坝体下工作面安全开采高度研究

为解决水库坝体下开采安全性,提高煤炭资源回收率,以王洼煤矿水库坝体下110505工作面为研究背景,通过物理仿真模拟、数值模拟及理论分析等方法对覆岩裂隙发育规律及导水裂隙带高度展开研究。为避免矿井开采对地表水坝与水体破坏,针对导水裂隙带高度分析结果,提出了110505工作面限高开采方案。结果表明:工作面开采后地表形成“凹”型盆地,并产生拉伸裂隙,致使地表水位下降78%;现场实测导水裂隙高度为170.76 m,物理仿真模拟试验、数值计算、传统经验公式得出三者的导水裂隙带高度分别为162,164 m和120.57 m;方差修正系数对经验公式做出修正后,反推出限高开采的安全开采高度为2.6 m。研究揭示了工作面覆岩导水裂隙带高度发育规律及水库水体受采动影响的规律,为王洼煤矿后续此类条件下安全措施的制定提供了依据。

水侵气藏型储气库全周期高效建设微观模拟实验

借助微观可视化模型与微流控技术,开展了水侵气藏型储气库初期建库阶段注气驱水及循环储采阶段采气底水上侵、储气排驱水体的模拟实验,分析气液界面稳定机制、气液渗流与赋存规律,探索储气库全周期高效运行的优化调控方式。研究表明:储气库初期建库阶段应调控注气速度,充分发挥重力作用保证气液界面宏观稳定运移,大幅度提高气体的波及能力,为储气库后续循环储采阶段提供更大的储气孔隙空间。储气库循环储采阶段,恒定的储采气速度导致孔隙空间利用率低,逐渐提高储采气速度,从“小吞小吐”逐渐过渡到“大吞大吐”,可以持续打破孔喉内流体的平衡受力状态,扩大储气孔隙空间与流动通道,有利于储气库扩容增效和调峰保供。

地面井分层卸压的煤系气合采原理及方式探讨

为了进一步认识制约煤系气合采的因素,提高煤系合层排采各产层的产气贡献,分别从动力、通道和气源条件出发,分析了煤系气合采的必备因素。基于改变地应力状态提高储层导流能力以及分层改变储层流体压力,满足多层合采动力条件的原理,提出了地面井分层卸压的煤系气合采方式。该方式通过在地面进行定向钻井,在目标储层中进行高压水射流作业,人工创造卸压空间(缝、槽、穴等),改变地应力状态,降低有效应力伤害,增加储层导流通道的数量和开度,提高目标储层压降传递速率。待储层压力降至符合煤系气合采动力条件时进行合层排采,从而提高煤系合采各产气层的产气贡献。相较于常规增产改造措施,此方式能够减少煤系气储层在有效应力作用下的储层伤害,且有助于提高储层压降传递效率,增强煤系气的解吸和扩散,降低多层煤系气合采过程中的层间干扰。在以上研究基础上,认为地面井分层卸压的合采方式主要适用于储层地应力大、产层间距小的煤系气储层,且有望在薄互层煤系气储层增产改造及层间干扰严重的叠合共生煤系储层开发领域进行应用推广。

塔里木盆地塔河北部“过溶蚀残留型”断溶体发育特征及其成因

为了研究塔里木盆地塔河北部强剥蚀区海西早期古岩溶洞穴发育特征,用古地貌恢复、岩溶水系统分析、测井-岩心洞穴识别和地震属性刻画等方法进行了YQ5井区的洞穴类型样式识别、缝洞结构刻画和洞穴成因演化研究。研究结果表明:YQ5井区在塔河油田Ⅱ号和Ⅲ号古岩溶台地北部的地势平缓区,总体为多期次岩溶叠加改造后的残留地貌,主要发育幅差较小的溶峰洼地、溶丘洼地和溶丘平原,南部发育NE向展布的峰丛垄脊沟谷。与塔河油田主体区及斜坡区不同,YQ5井区地下和地表水系的流向与地貌趋势不一致,岩溶水系统遭受构造作用破坏,导致补给、径流和排泄的岩溶水循环过程不完整。YQ5井区主要发育暗河型洞穴和“过溶蚀残留型”断溶体。暗河型洞穴充填较为严重,洞穴的有效储集空间受到破坏,影响油气开发效果。岩溶台地的构造抬升造成区域侵蚀基准面的下降,顺走滑断裂的垂向侵蚀作用有利于“过溶蚀残留型”断溶体的持续发育和保存,油气开发效果好。“过溶蚀残留型”断溶体的发育主控因素为走滑断裂、地层剥蚀强度和负向地貌。与塔河古岩溶台地演化过程一致,YQ5井区的岩溶演化经历深切曲流期、岩溶改造期和下渗断溶期3个阶段。暗河型洞穴被持续改造破坏,断溶体则持续建造。

循环水浸作用下煤体孔隙与损伤演化机制实验研究

煤柱坝体作为矿井采空区水库的主要承载结构,在多场耦合影响下的损伤失稳机制直接制约采空区水库的长期安全稳定运行。本文借助核磁共振(NMR)研究了“单侧”浸水条件下不同次数循环浸水下煤样T2谱图、孔喉、孔隙率变化和核磁图像演化规律,分析了单侧循环浸水次数不断增加下煤样内部孔隙演化规律以及单轴压缩破坏形态特征,揭示了煤样水浸损伤破坏机制,结果表明,随循环浸水次数的增加,煤样孔隙数、孔喉占比、孔隙率均保持增长的态势,分别增长了67.18%、3.48%、3.49%。煤样单轴抗压强度与残余强度逐渐减小,煤样的平均峰值强度由15.74 MPa依次下降到11.76、9.65、8.41 MPa,循环浸水9次煤样相较于初始状态煤样的平均单轴抗压强度下降46.56%,平均残余强度从未循环浸水的5.55 MPa依次下降到3.08、2.44、0 MPa。煤样单侧循环浸水水分子由浸水侧逐渐向煤样内部渗流,最后扩展至整个煤样,进一步造成孔隙率增加。长期的循环浸水对煤样的软化作用十分显著。研究结果为采空区水库空间结构稳定性控制提供了科学依据。

融合多种模态特征的井下供水管网流量预测

煤矿井下供水系统是煤矿安全生产的生命线,供水管网水流量的预测是供水系统优化调度的基础,预测的重要性对供水调度有重要影响。文章提出了一种融合多模态数据特征的煤矿井下供水管网流量预测方法,该方法通过图深度学习的方法实现了对井下管网空间拓扑结构、历史时间依赖、井下实际生产工况、周期相关等多种数据模态特征的融合,具体的,使用添加空间注意机制的图卷积神经网络获取井下管网监测点的空间拓扑关系,然后利用循环神经网络中的门控循环单元获取监测点的时间依赖,并融合煤矿生产规律与不同周期的流量数据形成最终预测结果,通过陕西亭南煤矿实际数据进行实验,结果表明,提出的预测方法相较于SVM、LSTM、STGCN等方法能更准确地预测井下流量未来的趋势,预测偏差分别降低了9.3%、6.84%和3.65%。

煤矿井下供水管网智能调控策略方法研究

煤矿井下供水管网系统是保证煤矿安全生产的关键环节,针对煤矿井下供水管网系统能耗高、管网漏损率高以及调控复杂度增加等问题,以陕西亭南煤矿井下实际供水系统工况展开智能调控策开研究。综合管网影响调控因素建立两级优化调度模型,通过一级优化调度确定每个水泵房的最佳供水压力与供水量,然后以泵组的运行费用为目标函数,建立二级优化模型寻求水泵的最佳运行方案。求解模型中针对传统遗传算法易陷入局部最优解的问题,采用了组合变异算子进行改进。实验结果表明,通过优化调度后,煤矿井下供水系统的能耗明显降低,节能效果显著,在保障供水系统的安全运行的前提下平均日节能8.8%。

深煤层气井低伤害完井液分析

深煤层气井的开采通常是采用水敏损害的完井液,但这类完井液存在着严重的伤害问题,对煤层气井的开采效率有着不利影响。在煤层气开采过程中,需要不断向井底注入液体,在注入过程中不可避免地会对煤层造成一定的伤害。从深煤层气井开采过程中出现的问题出发,对煤层气井中常见的完井液进行了分析和讨论,并在此基础上提出了相应的低伤害完井液方案。分析结果表明:低伤害完井液能有效降低深井煤层气开采过程中出现的问题。

利用测井资料评价煤层气可采性

精准评价煤层气可采性,对于制定压裂排采方案至关重要。本文以鄂东气田韩城矿区煤储层为研究对象,充分利用测井、煤岩心化验分析及排采动态测试资料,对影响煤储层完井品质的煤体结构指数、煤岩脆性指数、地应力差异系数进行了计算,并构建了煤储层完井品质指数预测模型;详细分析了煤层气排采出水量与各影响因素间的内在关系,建立了煤层气排采出水量预测模型;有机融合煤储层完井品质指数和出水量预测指数,建立了煤层气开采性评价指数预测模型和划分标准,进而基于该套技术方法进行了煤层气开采性评价。研究结果表明:本文所述技术既充分考虑了完井品质对煤层气开采的影响,又兼顾了排采出水量,所评价的煤层气可采性与煤层气开采实际生产情况较为吻合。

煤矿地下水库技术原创试验平台体系研制及应用

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