【摘要】 为了提高低渗高应力煤层增透卸压效果，解决水力压裂产生的水压裂缝与天然缝网贯通效果差的问题。基于CO₂低黏度流动性好的特点，研发一种岩石CO₂致裂器，以60℃水作为载热流体，采用CFD模拟方法研究不同CO₂温度条件下致裂器中水热流体对超临界CO₂变温、流量以及热功变化规律，通过试验分析验证CO₂致裂器的可靠性。结果表明:随着CO₂由5℃升至25℃时，CO₂温度与水热流体温度呈负相关变化; CO₂相变吸热对流量影响较大;随着CO₂初始温度的增加CO₂传热也在增长，水热流体传热系数由714 W/（m²·K）减少至359 W/（m²·K）; CO₂热做功由22.74 kJ增加至23.61 kJ,CO₂所携带的TNT能量由855.23 kJ增加至1 114.85 k J,CO₂初始温度与热做功及TNT能量呈线性关系。现场试验证明了不同温度、体积CO₂热功交换在致裂煤岩裂隙扩展中具有重要作用。更多还原

【Abstract】 This paper seeks to improve the permeability and pressure relief effect of the coal seam with low permeability and high stress,and address the poor penetration effect between hydraulic fracture and natural fracture network produced by hydraulic fracturing. Based on the advantages of low viscosity and good fluidity of CO₂,the study involves developing a rock supercritical CO₂ fracturing device; studying the changing law behind hydrothermal fluid in the fracturing device under different CO₂ temperature conditions on the temperature and 60 ℃ water as the heat-transfer fluid,flow rate and heat work of the supercritical CO₂; and verifying the reliability of CO₂ fracturing device by experimental analysis. The results show that with the increase of CO₂ temperature from 5 ℃ to 25 ℃,the temperature of CO₂ is negatively correlated with the temperature of hydrothermal fluid. The phase change heat absorption of CO₂ has a great influence on the flow rate. As the initial temperature of CO₂ increases,the heat transfer of CO₂ also increases,and the heat transfer coefficient of hydrothermal fluid decreases from 714 W/（ m²·K） to 359 W/（ m²·K）;and the thermal work of CO₂ increases from 22. 74 k J to 23. 61 k J,the TNT energy carried by CO₂ increases from 855. 23 k J to 1 114. 85 k J,indicating that the initial temperature of CO₂ has a linear relationship with thermal work and TNT energy. The field test shows that the thermal power exchange of CO₂ at different temperatures and volumes plays an important role in the crack propagation of fractured coal rock.更多还原