水平井网地浸采铀溶浸范围井储耦合和粒子示踪模拟

Quantitative Characterization of Horizonal Well Leaching Range Using Coupled Well-Reservoir Coupling Model and Particle Tracing Technology

摘要:

为探索水平井技术在我国砂岩型铀矿地浸采铀领域的可行性，解析水平井网地浸采铀水动力过程和定量刻画溶浸范围是科学评判的基础和前提。水平井网地浸模式下地下水动力过程涉及井筒流与储层达西流的耦合（井储耦合），通过研发井储耦合数值模拟技术，构建水平井网地浸采铀地下水动力学模型，开发基于MODPATH粒子示踪模拟和Alpha-shape算法的溶浸范围自动提取技术，基于理想模型和实际场地模型的应用验证，实现地浸开采过程中溶浸液流动状态和溶浸范围的模拟刻画。研究结果表明：相比于传统的MODFLOW模型，井储耦合模型可刻画水平井注液过程中井储交互流量及变化，且交互流量值与储层渗透系数K值变化呈正相关；在井储耦合渗流模拟的基础上，可自动提取模拟时段内被抽液井有效捕捉的粒子迹线所包络的范围，识别抽液井不同捕获流量贡献率对应的溶浸范围，95%流量贡献率对应的溶浸范围为100%流量贡献率对应范围体积的40%，表明溶浸液从水平井注入储层至浸出液被竖井抽出，地浸开采前期流量交互主要集中于溶浸范围内部，而外部迹线的流速低，对抽液流量的贡献率低且浸出率低。

关键词:地浸采铀;水平井网;水动力;溶浸范围;数值模拟

Abstract:

To explore the feasibility of horizontal well technology in in-situ leaching （ISL） of sandstone-type uranium mines in China， it is essential to analyze the hydrodynamic processes and quantitatively characterize the leaching range. The hydrodynamic processes of groundwater in the horizontal well ISL involve well-reservoir coupling simulation， which refers to the coupling of wellbore turbulence and reservoir Darcy flow. By developing numerical simulation techniques for well-reservoir coupling， constructing a groundwater flow model for uranium leaching in the horizontal well network， and creating automatic extraction techniques for the leaching range using particle tracking simulation with MODPATH and the Alpha-shape algorithm， the simulation and characterization of the flow state of the solution and the leaching range during ISL can be achieved. The research results indicate that， compared to the traditional MODFLOW model， the well-reservoir coupling model more accurately depict the interaction flow rate and its variations between the well and reservoir during the injection process in the horizontal well， and the interaction flow rate is positively correlated with the permeability coefficient （K） of the reservoir. Based on the well-reservoir coupling simulation， the range enveloping the particle trajectories captured by the pumping wells during the simulation period can be automatically extracted. By identifying the leaching range corresponding to the flow rate contribution of pumping wells， it is determined that the leaching range corresponding to a 95% flow rate contribution is 40% of the volume corresponding to a 100% flow rate contribution. This indicates that the flow interaction， from the injection of leaching solution from the horizontal well into the reservoir to the extraction of pregnant solution by vertical wells， is primarily concentrated within the leaching range in the early stage of ISL. The flow velocity along the outer trajectories is lower， resulting in a reduced contribution to both the pumping flow rate and the leaching rate.

Key words:in-situ leaching;horizontal well network;hydrodynamics;leaching range;numerical simulation