无井式煤炭地下气化高温-地应力耦合作用下覆岩裂隙发育机理及演化特征

The industrialization of underground coal gasification (UCG) is one of the important directions of China's advanced energy technology field. China's UCG technology and combustion control technology has reached the international advanced level. With the rapid development of UCG industrialization, how to solve the underground gasifier surrounding rock fracture and the induced ingress of groundwater is becoming one of the technical challenges for its routine production. The research on overburden fracture development mechanism and height prediction model under coupled action of high temperature-ground stress during UCG could provide scientific basis for solving the problem. .The laboratory experiments, similar material simulation at constant temperature and humidity environments, numerical simulations, field tests and theoretical analysis are used as key research methodologies in the research. The three-dimensional shape and propagation laws of the combustion space area is studied firstly. Then the overburden fracture development patterns, mechanism and evolution characteristics of the combustion space area supported by unconventional coking coal pillars are revealed. The prediction model of overburden fracture development height under the coupled action of high temperature-ground stress during the strip UCG is established. The width design methods of the gasifier and isolated coal pillars under overburden aquifers are proposed. The research results could provide scientific and technical supports for gasification design under overburden aquifers. This project has great scientific significance to enrich the strata control theory. It also has great practical importance to protect underground water and ecological environment. What's more, it has significant application prospect in promoting UCG industrialization.

煤炭地下气化产业化是我国先进能源技术领域的重要方向之一，我国煤炭地下气化工艺与燃烧控制技术已达到了国际先进水平。但随着产业化推广应用，如何解决地下气化炉围岩破裂及其诱发的地下水侵入将成为阻碍其正常生产的核心技术难题之一。研究地下气化高温-地应力耦合作用下覆岩裂隙发育机理与高度预测模型可为解决该问题提供科学依据。.本项目拟采用力学测试、相似材料模拟、数值模拟、现场试验和理论分析等手段，从研究无井式地下燃空区形态及扩展规律入手，揭示“非常规”型焦化煤柱支撑下覆岩裂隙发育形态、机理及演化特征，建立带状地下气化高温-地应力耦合作用下覆岩裂隙发育高度预测模型，提出覆岩含水层下气化炉与隔离煤柱宽度设计方法；从而为覆岩含水层下气化采煤设计提供科学与技术支撑。本项目对于丰富矿山岩层控制理论具有重要的科学意义；对于保护矿区地下水与生态环境具有重要的实用价值；对于煤炭地下气化产业化推广具有重要应用前景。

煤炭地下气化产业化是我国先进能源技术领域重要方向。但随着地下气化推广应用，如何解决地下气化炉围岩破裂及其诱发的地下水侵入将成为阻碍其正常生产核心难题之一。为了解决上述难题、实现含水层下安全气化采煤，采用实验、模拟、监测及理论分析等方法，从研究无井式地下燃空区形态及扩展规律入手，研究揭示“非常规”型焦化煤柱支撑下覆岩裂隙发育形态、机理及演化特征，建立多场耦合作用下带状地下气化覆岩裂隙发育高度预测模型，进而为覆岩含水层下气化采煤设计提供科学依据与技术支撑。. （1）揭示了不同地下气化工艺燃空区分布形态，得出无井式双通道地下气化燃空区形态近似为“梯形”，“条采-面采”后退式控制注气地下气化燃空区形态为宽扁圆形，且燃空区宽度取决于地下气化工艺，一般为15～35m。分析了煤种类及顶底板岩性对地下燃空区形态影响规律，建立了顾及煤种类及顶底板岩性的地下气化燃空区三维形态理论模型。. （2）无井式煤炭地下气化覆岩裂隙发育形态呈现出向两侧延伸的“蝶翼型”。研究明确了气化炉参数对覆岩裂隙发育高度影响，当气化炉高度一定且隔离煤柱稳定时，气化炉宽度与采动裂隙发育高度呈线性关系；当气化炉宽度和隔离煤柱宽度一定时，气化炉高度与采动裂隙发育高度呈线性关系。在上述研究基础上，研究揭示了煤炭地下气化燃空区覆岩裂隙发育机理。. （3）基于燃空区顶板-煤柱-底板协同变形思想，构建了“非常规”焦化煤柱支撑的顶板-煤柱-底板协同变形力学模型，建立了相应的燃空区覆岩裂隙发育高度计算模型；同时对比分析了煤炭地下气化和常规井工开采覆岩裂隙发育差异，建立了兼顾采动程度的燃空区覆岩裂隙发育高度计算模型。形成了覆岩含水层下气化采煤设计原则及流程，提出了覆岩含水层下气化炉与隔离煤柱宽度设计方法，为水体下气化采煤设计提供了技术支撑。. 项目研究成果对于保护矿区地下水与生态环境具有重要实用价值；对于煤炭地下气化产业化推广具有重要应用前景。