沁水盆地南部叠置含煤层气系统合层排采层间干扰作用机制和主控因素研究

For a long time, the scale development of coalbed methane (CBM) in the southern Qinshui Basin is confined to Shanxi Formation, and the abundant CBM resources in the Taiyuan Formation is unable to be extracted in a large scale. The interlayer fluid interference between the superposed CBM-bearing systems in vertical during commingled drainage is a key scientific and technical problem to restrict the high-efficiency commingled production of the CBM in Taiyuan Formation and Shanxi Formation. Centre on this key scientific problem, the Taiyuan Formation and Shanxi Formation of Carboniferous-Permian in the southern Qinshui Basin are taken as the research object in this project, and a method combining geological analysis of CBM-bearing system, numerical simulation and physical simulation of commingled drainage is adopted to discuss the essential characteristics of fluid pressure systems of Taiyuan Formation and Shanxi Formation, establish the boundary conditions, geological model and mathematical model of the interactions between the two sets of fluid pressure system during commingled drainage, and conduct the production numerical simulation of commingled drainage, and then clarify the interaction relationship between the two sets of fluid pressure systems under the condition of commingled drainage. On these bases, combining the physical simulation of interlayer interference, the active mechanism and primary controlling factors of interlayer interference of CBM commingled production under the development condition of “superposed CBM-bearing systems” is illuminated. The knowledge obtained from the project can promote the establishment of optimal design theory and method of high-efficiency commingled production of the CBM in the study area, which will provide the technology innovation basis for improving the recovery rate of CBM in Shanxi Formation and Taiyuan Formation.

长期以来，沁水盆地南部煤层气规模性开发局限于山西组，丰富的太原组煤层气资源无法规模性动用。垂向上叠置含煤层气系统在合采诱导下引发的层间流体干扰，是制约该地区太原组与山西组煤层气高效合排的关键科学技术问题。围绕该科学技术问题，本项目以沁水盆地南部石炭—二叠系太原组和山西组为研究对象，采用含煤层气系统地质分析、合层排采数值模拟及物理模拟等手段相结合的研究方法，探讨山西组和太原组流体压力系统的基本特征，建立两组流体压力系统排采相互作用的边界条件、地质模型和数学模型，开展研究区两组煤层气合层排采产能数值模拟，厘清合层排采条件下两组流体压力系统的相互作用关系。在此基础上，结合层间干扰物理模拟实验，阐明“叠置含气系统”开发条件下两组地层流体压力系统间的层间干扰作用机制和主要控制因素。项目所获认识可推进建立研究区煤层气合层高效排采的优化设计理论与方法，为提高山西组和太原组煤层气的采收率提供技术创新依据。

长期以来，沁水盆地南部煤层气规模性开发局限于山西组，太原组煤层气产能难以有效释放。针对这一技术“瓶颈”，采用流体压力系统分析与数值模拟相结合的研究方法，探讨了该区山西组和太原组含煤层气系统的基本特征，发现了煤系叠置流体压力系统的客观存在和显现特点。基于合层排采煤层气井产能数值模拟，分析了叠置含煤层气系统合层排采条件下，山西组和太原组两组地层流体压力系统中储层压力在空间的动态变化规律，阐明了沁水盆地南部太原组和山西组合层排采层间干扰作用机制。研究发现，叠置系统发育是共采条件下上、下两套流体压力系统层间干扰产生的地质根源，上、下两套储层压力梯度差越大，层间干扰越明显，共采兼容性越差，同时，K2灰岩含水层的存在会增强上、下两组流体层间干扰效应，灰岩富水性越强，储层能量越高，干扰越显著，共采兼容性越差。查明了控制太原组15号煤层单层排采的主要地质因素，构建了针对15号煤层煤层气单层开发潜在有利区模糊层次评价体系，划分出了平面开发地质单元。基于山西组和太原组主煤层单层开采煤层气井产出水的特征微量元素研究，建立特征微量元素交汇模板，对合层排采煤层气井产出水的来源进行了有效判识，进而摸清了合层排采条件下山西组和太原组两组地层流体在煤储层及井筒内的运移过程和相互作用关系，该认识对于合层排采兼容性具有重要的指示意义。此外，基于对合层排采煤层气井产能地质控制因素的分析，采用模糊物元分析方法，建立了合层排采的地质评价体系。最终，建立了以特征微量元素标准模板和模糊物元评价为核心的合层排采可行性综合判识方法。