废弃矿井非正规老空区储气空间分布及其煤层气渗流特性

Due to the backward coal mining methods in the history of in our country, a large number of informal gobs of abandoned mines were formed containing rich methane resources. However, the existing "Three zones" and "O" shape circle theories are mainly used for guidance to determine the distribution of normal gob of methane enrichment region, which resulted higher project cost and undesirable extracting effect in the process of development of informal gob using surface wells. For the above reasons, we study the distribution of gas storage space (including cavity, collapse body and cracked body) of informal gob by using rock structural snalysis, similar simulation experiment and UDEC numerical simulation. And based on the permeability tests of collapse body and cracked body, we study the permeability distribution in gas storage space. Then the simulation software of COMSOL Multiphysics will be used as a platform to set up a multi physics field mathematical model which relects the process of methane migration. Using the model, we could study the dynamic characteristics of methane migration in gas storage space. Ultimately the distribution characteristics of gas storage space of informal gob under different rock structurals will be determined, and the methane enrichment region of different gas storage spaces also would be divided. Finally the results of this study will be used for verification, feedback and correction with field industrial test results. Research results will provide new theory and thinking of location selection and well pattern arrangement for surface well extracting the methane of informal gobs.

我国历史上采用落后采煤方法形成的大量废弃矿井非正规老空区蕴含有丰富的煤层气资源。然而由于已有的“三带”和“O”形圈理论主要用于指导正规采空区煤层气富集区的确定，在指导地面钻井开发非正规老空区煤层气过程中往往导致工程成本较高且难以取得预期抽采效果。基于此本项目通过岩层结构分析、相似模拟和UDEC数值模拟，研究非正规老空区储气空间（包括空洞、垮落体和裂隙体）分布，在此基础上结合不同应力环境下垮落体和裂隙体渗透试验，研究储气空间的渗透率分布，进而以多物理场模拟软件COMSOL Multiphysics为平台，建立反映煤层气运移过程的多场耦合数学模型，研究储气空间内煤层气运移的时空动力学特性，最终确定不同岩层结构下非正规老空区储气空间分布特征，划分出各类储气空间内煤层气富集区，并通过现场工业性试验进行验证、反馈、修正。研究成果将为非正规老空区煤层气地面抽采钻井井位选择和井网布置提供新的理论和思路。

已有的经典“三带”和“O”形圈理论主要用于指导正规采空区煤层气富集区的确定，在指导地面钻井抽采非正规老空区煤层气过程中往往导致工程成本较高且难以取得预期抽采效果。基于此，本项目采用理论分析、物理模拟试验、数值计算和现场试验等方法，研究了废弃矿井老空区积气空间分布及其煤层气渗流特性，主要取得如下成果：采用二维相似试验和UDEC数值软件，研究了老空区裂隙场分布特征，并基于Matlab软件开发了相应的数字图像处理及分析程序，对裂隙场图像进行二值化处理，定量研究了废弃矿井老空区积气空间分布特征；采用煤岩体加载渗透试验系统，研究了垮落体和裂隙体应力与渗透率之间的关系；运用EDEM数值软件，研究了应力传递及演化对垮落岩体内不同层位空隙率分布的影响；利用FLAC3D数值软件，计算了不同宽度和煤层倾角老空区的三维应力分布，划分出老空区积气空间，并分析了其分布特征；采用三维可加载多元气体渗流试验系统，研究了老空区煤层气积气空间分布特征；采用COMSOL数值软件，研究了不同井位地面钻井抽采条件下老空区煤层气渗流特性；提出了适用于废弃矿井老空区的井位层位优选、防水井身结构、穿煤柱压裂贯通老空区和间歇式蓄流高效抽采的成套技术，并在现场进行了应用。