【作者】 李志强；

【导师】 鲜学福；

【作者基本信息】 重庆大学 ， 安全技术及工程， 2008， 博士

【摘要】 煤层气,曾称煤层瓦斯,是赋存于煤及其围岩中的一种与煤伴生共存的非常规天然气,主要成分为甲烷,是一种优质洁净的气体资源。开发利用煤层气不仅可以有效的遏制煤矿瓦斯灾害,降低甲烷气体对大气环境的温室效应,而且开采储量巨大的煤层气资源对于优化我国以煤为主的能源结构,缓解能源短缺具有战略意义。我国煤层气具有巨大的储量和诱人的开发前景,但至今尚未进入商业化开发阶段,主要是因为我国煤储层具有高煤级、高地应力、低渗透的特征,这使得我国煤层气的富集规律、渗透性变得异常复杂。本文针对我国当前煤层气富集区预测难以定量化、预测位置模糊不精确;高渗区预测定性描述、预测位置不准确;储量计算精度不高,难以反映煤厚和含量的非均质性;选区综合评价中指标矛盾不相容性;背斜煤层气富集规律及富集成藏机制缺乏系统完整的研究等几大关键科学问题展开研究,取得了如下成果:煤层气富集区预测,建立了地应力场、地温场中煤层气含量、压力预测方程,提出了煤层气富集区高精度、定量化预测理论与方法。进行了kaiser原岩应力测试实验、不同温度的甲烷吸附实验及煤质分析实验,结合原始地质数据,定量预测了重庆沥鼻峡盐井矿区主力煤层气的含量、压力分布,并划定了煤层气富集区,解决了煤层气富集区难以定量化预测和预测位置不准的难题。提出了两种新的、精度较高的煤层气储量计算方法——微元体积法,计算了研究区煤层气地质储量和技术可采储量,解决了当前煤层气储量计算中难以体现含气量和煤厚非均质性的问题。煤层气高渗透区预测,(1)建立了地应力场、地温场中煤层渗透率预测方程,同时提出了用实验室测试的渗透率计算真实渗透率的校正方法,定量预测了研究区7层煤的渗透率分布,划出了高渗透区的位置,解决了煤层气高渗区预测难以定量化和预测位置不准的问题;(2)进行了不同温度、不同有效应力下的CH4和He渗流实验,发现了不同有效应力条件下,渗透率与温度的关系,提出了升温渗流过程中的“内膨胀效应”和“外膨胀效应”理论模型,并通过数学推证,解释了低有效应力条件下渗透率随温度升高而增大,高有效应力条件下渗透率随温度升高而降低的实验现象;(3)提出了地应力场、地温场中煤层气渗流运移控制方程,以现场实际资料和实验为基础,计算了矿井煤层气的抽采运移能力。背斜煤层气富集成藏规律,进行了煤的扫描电镜实验、孔径分布与比表面积实验、从煤层气的生成、储集、保存和煤的沉积的角度,对重庆沥鼻峡高陡背斜煤层气富集规律进行了较为系统的研究,通过将各因素与含气量逐项对比分析,研究了重庆沥鼻峡盐井矿区煤层气富集的主控因素、控气机制及成藏模式,并得出本区煤层气富集影响因素为煤厚、埋深、断层、含碳量(煤阶),主控因素为构造动力,构造改造引起了煤厚、埋深、渗透率、煤体结构、煤的孔隙结构、应力等一系列变化,同时引起了局部动力变质作用。高陡背斜煤层气富集的构造控气机制,进行了煤岩的力学性质实验,计算了沥鼻峡背斜盐井矿区的应力场,研究了应力分布与煤层气富集的关系。从构造动力学角度,研究了高陡背斜、高角度断层、煤厚变化的成因及各因素的控气机制,研究了背斜煤层动力变质的分布规律及其控气机制。煤层气开发有利区带预测的选区综合评价,引入了全新的煤层气选区综合评价方法——模糊物元法,根据前述研究成果,提出了煤层气评价指标体系,对开发有利区块进行了优选排队,预测了本区煤层气开发的有利区带,并对各区开发条件进行了综合评价。根据评价结果,提出了重庆地区煤层气开发的建议。重庆地区高陡背斜煤层气富集规律与构造动力密切相关,从构造动力学定性和岩石力学定量综合研究,是今后重庆地区煤层气开发的主要研究方向,井下卸压抽采是本区较为合适的开发方式。更多还原

【Abstract】 Coalbed methane, a kind of unconventional gas associated with coal, exists in coal seam and surrounding rocks of coal seam. CH4, main ingredient of coalbed methane, is a new kind of clean gas resource. Exploitation and utilization of coalbed methane is beneficial to not only prevent the mine methane disaster, but also reduce greenhouse effect generated by methane, meanwhile, exploitation of huge reserves coalbed methane has important strategic meaning for China to optimize energy structure dominated by coal and reduce energy shortage.There are huge coalbed methane reserves and attractive development future in China. But up to now, China has not moved into commercialization phase of coalbed methane exploiting. The main reason was that the coal seam has characteristics of high stress, high rank and low permeability in China, which makes coalbed methane enrichment regular complicated. According to five key scientific problems: the enrichment zone of coalbed methane has not been predicted quantitatively; high permeability zone of that is hard to predict exactly and quantitatively; calculation precision of gas storage capacity is not enough; appraisal indexes of favorable zone selecting are incompatible; coalbed methane enrichment law and mechanisms is lack of systematic study. The main achievements of the thesis are followings:Pressure and content prediction equations of coalbed methane are established in geothermal and geo-stress field. The quantitative prediction theory and method of coalbed methane enrichment zone is put forward. Ground stress testing by Kaiser Method, experiment of adsorption at different temperature and coal quality analysis is carried out. The coalbed methane content and pressure distribution of main coal seam of Yanjing mine area in Chongqing Libi gorge is predicted quantitatively, meanwhile, gas enrichment zone is determined. The problem of coalbed methane enrichment zone quantitative prediction is solved.Base on the above achievements, two new calculation methods of gas reserves are provided. Geological reserves and technical recoverable reserves of coalbed methane are estimated in liibi gorge Yanjing first mine area. The heterogeneity problem of gas reserves calculation is solved.The quantitative prediction theory and method of coalbed methane high permeability zone is established in geothermal and geo-stress field. Corrector method of permeability is put forward between experiment and actual measurement. The permeability distribution of seven coal seams is calculated, at the seam time, the high permeability zone of main coal seam is divided. CH4 and He seepage experiment in coal at different stress and temperature is carried out. The relationship between permeability and temperature at different stress is found. The pore model of internal expansion and out expansion is provided during gas flowing with temperature increasing. The permeability increases with the temperature increasing at low effective stress, but decreases with the temperature increasing at high effective stress. The seepage equation is put forward in geothermal and geo-stress field. The flowing process is simulated.Coalbed methane enrichment regular was studied. SEM and pore distribution experiments of coal are carried out. Coalbed methane enrichment law at Libi gorge high-steep anticline is systematically studied on four aspects, such as creation, reservoir, preservation and flow of coalbed methane. Compared content and the factors, main controlling factors and their controlling mechanism were studied. Main influencing factors of gas enrichment were found. The main influencing factors are coal seam thickness, depth, faults and FCd( coal rank), the main controlling factors is tectonic. The tectonic rebuilding generates changing of coal seam thickness, depth, permeability, coal mass structure, pore structure and stress and so on. Meanwhile, degree of coalification is promoted because of tectonic rebuilding in some locations..Mechanical property of rock is tested. Stress field is simulated in Libi gorge anticline. According to stress distribution, the cause and deformation of anticline, faults, and coal seam thickness is studied, the factors controlling mechanism is studied too.Fuzzy element method, a new evaluation method, is provided. Based on former research results, evaluation index system is established. The favorable exploration zone is predicted, and exploration condition of four zones are comprehensive assessmented.According to above results, suggestion of developing coalbed methane in Chongqing is put forward. There are close relations between coalbed methane enrichment and tectonic stress. Combined qualitative tectonic dynamics with quantitative rock mechanics, is a main research direction about coalbed methane in Chongqing. Drawing after reducing stress is favorable development method in the research area.更多还原