微波加热开采低渗透煤层煤层气的逾渗机理研究

Coal bed methane (CBM) is an important clean energy and high-quality chemical raw materials. China has rich storage, but most of reservoirs are low permeability. It is difficult and inefficient to exploit CBM. The project adopts combinative research methods including site visits, theoretical analysis, experimental studies and numerical simulation field application. Increase the inter temperature of coal bed by microwave heating and research the variation of CBM's mechanics parameters and permeability characteristics under different confining pressure, axial compression and pore pressure. It shows that the mechanism of increasing the seepage rate of low permeability coal seam by microwave heating. Based on high-precision CT scan system carries through the interior observation experiment of coal and rock destroy and crash process under stress field. The relation between percolation transition basic parameters and environment parameters could be found according to the coal and rock interior structure CT pictures under load whole process. According to the CBM's characters and coal's parameters change laws by microwave heating, the percolation theory and double-porosity medium mathematical model on CBM exploitation by microwave heating in low permeability coal seam are found. Numerical simulation program composition carry out numerical simulation for percolation process of CBM exploitation by microwave heating. The percolation evolutionary laws on CBM exploitation by microwave heating in low permeability coal seam by analyzing numerical simulation results could be found. It disclosures the percolation mechanism on CBM exploitation by microwave heating in low permeability coal seam. The research provides a basis for theoretical support to solve the CBM exploitation technology problem of low permeability coal seam.

煤层气是重要的洁净能源和优质的化工原料，但我国煤层绝大多数为低渗透煤层，井下瓦斯抽放率很低。本项目采取现场考察、实验研究、理论分析、数值模拟相结合的综合性研究方法。通过微波加热方式提高煤层内部温度，研究不同围压、轴压、孔隙压力下，煤与煤层气受微波加热后力学参数和渗透特性变化规律，基于高精度CT扫描系统对煤岩体受应力场、温度场作用后破坏破碎全过程进行内部观测试验，得到煤岩逾渗转变基本参数与环境参数关系，通过分析微波加热煤体和煤层气自身性质的改变规律，建立起微波加热开采低渗透煤层气藏的逾渗演化双重介质数学模型，编制数值模拟软件对微波加热开采煤层气逾渗过程进行数值模拟研究，分析数值模拟结果，总结低渗透煤层气在不同形式微波加热作用下逾渗演化规律，揭示微波加热开采低渗透煤层气的逾渗机理，为解决低渗透率煤层瓦斯抽放的技术难题提供基础理论支持。

煤层气是重要的洁净能源和优质的化工原料，但我国煤层绝大多数为低渗透煤层，如何提高低渗透煤层渗透率是煤层气商业化开采面临的难题。项目通过实验室实验、实验分析、理论分析和数值模拟等手段，对微波加热开采低渗透煤层煤层气的逾渗转变机理进行研究，揭示微波加热煤层能够诱使煤层逾渗，进而提高低渗透煤层中煤层气采出速率的机理。项目主要研究成果如下：自制了微波加热解吸渗透装置，进行了不同围压、轴压、孔隙压力下，煤与煤层气受微波加热后力学参数和渗透特性实验。实验证明，微波加热有利于煤层气渗流量的增加；基于高精度CT扫描系统对煤岩体受应力场、温度场作用后破坏破碎全过程进行内部观测试验，得到煤岩逾渗转变基本参数与环境参数关系；得到了热对煤的相变作用、孔隙变化规律和介电常数特征；通过分析微波加热煤体和煤层气自身性质的改变规律，建立起微波加热开采低渗透煤层气藏的逾渗演化双重介质理论和数学模型；利用有限元数值模拟软件对微波加热开采煤层气逾渗过程进行数值模拟研究，在单井热力开采煤层气基础上，研究多井开采煤层气条件下，井间干扰多煤层气渗流规律的影响；编制了微波加热诱发逾渗开采煤层气藏的程序软件；总结低渗透煤层气在不同形式微波加热作用下逾渗演化规律，揭示微波加热开采低渗透煤层气的逾渗机理，提出含瓦斯煤的逾渗转变过程；这些成果的取得为解决低渗透率煤层煤层气抽放的技术难题提供基础理论支持。