低阶煤储层气-水两相多机理流动规律及数值模拟研究

The exploration and development of low-rank coal bearing areas and its corresponding foundamental research are relatively weak,and the systematic study on the well pattern optimization is relatively few. According to the the special pore structure and fluid occurrence characteristics in coalbed methane reservoirs, the project will conduct the adsorption and desorption experiments under ground stress state and their interaction mechanism experiments with seepage flow,in order to further clarify the interaction mechanism between desorption phenomenon in the matrix and seepage flow of fluids through the macropores under the actual reservoir condition, followed by an establishment of mathematical and numerical models concerning the multi-mechanism of gas-water flow, and a relevant simulation program about them will be worked out. On such basis, a new optimizor of broader universality and greater portability applying the particle swarm optimization algorithom, with two seperate fitness functions of net present value and large-scale isostatic pressure drawdown is to be framed and uesd to guide the low-rank coalbed methane development.As a whole, the above research is of great significance in promoting the all-round development of low-rank coalbed methane industry.

本项目针对低煤阶煤储层特殊的孔隙结构及流体赋存特征，开展地应力场作用条件下低煤阶煤层气的吸附/解吸实验及其与渗流间的相互作用机理实验研究，揭示真实低煤阶煤储层条件下受地应力场和温度场等耦合作用的煤层气吸附/解吸规律以及吸附/解吸变形与渗流间的相互作用规律；综合考虑吸附/解吸作用以及应力场、渗流场和浓度场的耦合作用，建立可更为准确描述低煤阶煤储层条件下气-水两相多机理运移的数学模型，并编制相应的模拟计算程序。在此基础上，考虑煤层的非均质性特征及卸压开采特点，以煤层大范围持续均衡降压以及经济效益最大化为目标，结合改进的粒子群优化算法，建立一套新的低煤阶煤层气井网自动优化理论方法，并开展相关的概念井网优化设计分析，为我国低煤阶煤层气的大规模商业开发提供重要的理论基础。

针对低煤阶煤储层的孔隙结构及流体赋存特征，开展了地应力场作用条件下的煤层气吸附/解吸规律及其与渗流间的相互作用机理试验研究，揭示了真实储层条件下低煤阶煤层气受地应力场及温度场等耦合作用的吸附/解吸规律以及吸附/解吸变形与渗流间的相互作用规律，并综合考虑吸附/解吸作用以及应力场、渗流场和浓度场的耦合作用，构建了可更为准确描述低煤阶煤储层条件下气—水两相多机理流动的耦合物理模型及数学模型，并针对气-水两相复杂流动模型离散后形成的代数方程组求解，形成了包括块矩阵压缩存储、块 ILU 预处理、块正交极小化算法等高效求解技术；在模型求解的基础上，充分考虑煤层的非均质特征及卸压开采特点，以煤层大范围持续均衡降压以及经济效益最大化为目标，建立了一套基于改进粒子群优化算法的煤层气直井井网优化设计方法，打破了现有井网优化方法的局限，该方法可以根据煤层气开发区块的具体地质条件实现新井网井位以及老井网加密井位的自动优化，并开展了应用分析，为我国低煤阶煤层气高效开发提供了重要的理论指导和技术支撑。