Wang Zhiquan, Liu Zhengdong, Hu Ze
College of Safety Science and Engineering, Liaoning Technical University, Fuxin 123000, China.
State Key Laboratory of Coal Mine Safety Technology, China Coal Technology & Engineering Group Shenyang Research Institute, Fushun 113122, China.
ACS Omega. 2023 Dec 27;9(1):1591-1602. doi: 10.1021/acsomega.3c08043. eCollection 2024 Jan 9.
The supercritical CO enhanced coalbed methane (ScCO-ECBM) technology is still in the development stage, and many simulation experiments and theoretical studies related to ScCO-ECBM are being improved. Previous research works have conducted many studies on the competitive adsorption of CO and CH in coal, but there is less research on the competitive adsorption of ScCO and CH and its impact on methane extraction characteristics. In this study, a permeability model considering the competitive effects of effective stress and adsorption swelling on permeability was established. Based on the assumed conditions and permeability evolution model, different injected pressure and initial methane pressure conditions were set to obtain quantitative results of the competitive adsorption of ScCO and CH, permeability changes, and CH production. By obtaining the competitive adsorption relationship between ScCO and CH, we analyzed the evolution law of permeability and its impact on CH production. It was found that ScCO has a stronger competitive adsorption capacity, and the competitive adsorption capacity of ScCO and CH is more sensitive to injected pressure. Under two different conditions, it was found that the higher the injected pressure or injected differential pressure, the higher the initial permeability. However, due to the greater sensitivity of the competitive adsorption capacity of ScCO and CH to injected pressure, the greater the injected pressure in the later stage, the greater the decrease in permeability, resulting in a situation where the permeability at an injected pressure of 10 MPa is lower than that at an injected pressure of 8 MPa. A simple comparison was made between gaseous CO and ScCO, and it was found that although injecting ScCO has a stronger adsorption swelling capacity that affects permeability changes, its stronger adsorption capacity can effectively displace methane and higher injected pressure, injected temperature, and advantages such as fracturing and extraction that are not yet reflected in the model. This study provides some guidance for numerical simulation of the ScCO-ECBM process and the enhancement of coalbed methane extraction.
超临界CO₂强化煤层气（ScCO₂-ECBM）技术仍处于发展阶段，许多与ScCO₂-ECBM相关的模拟实验和理论研究正在不断完善。以往的研究工作对CO₂和CH₄在煤中的竞争吸附进行了大量研究，但对ScCO₂与CH₄的竞争吸附及其对甲烷开采特性的影响研究较少。本研究建立了一个考虑有效应力和吸附膨胀对渗透率竞争效应的渗透率模型。基于假设条件和渗透率演化模型，设置不同的注入压力和初始甲烷压力条件，以获得ScCO₂与CH₄竞争吸附、渗透率变化和CH₄产量的定量结果。通过获得ScCO₂与CH₄之间的竞争吸附关系，分析了渗透率的演化规律及其对CH₄产量的影响。研究发现，ScCO₂具有更强的竞争吸附能力，ScCO₂与CH₄的竞争吸附能力对注入压力更为敏感。在两种不同条件下发现，注入压力或注入压差越高，初始渗透率越高。然而，由于ScCO₂与CH₄的竞争吸附能力对注入压力更为敏感，后期注入压力越大，渗透率下降幅度越大，导致注入压力为10MPa时的渗透率低于注入压力为8MPa时的渗透率。对气态CO₂和ScCO₂进行了简单比较，发现虽然注入ScCO₂具有更强的吸附膨胀能力从而影响渗透率变化，但其更强的吸附能力能够有效置换甲烷，且注入压力、注入温度以及压裂和开采等优势在模型中尚未体现。本研究为ScCO₂-ECBM过程的数值模拟和煤层气开采强化提供了一些指导。
