腔径比对自激振荡脉冲超临界二氧化碳射流性能影响

Effect of cavity diameter ratio on the pulse performance of self-excited oscillation pulsed supercritical carbon dioxide jet

井壁稳定性低及煤层透气性低是限制煤层气开采的关键因素,超临界二氧化碳射流钻井技术在煤层气开采中有其独特的优势,由于其高密度、低黏度和扩散性强等特点,在增强井壁稳定性及提高采收率的同时,能够实现二氧化碳的地下封存。但较高的系统能耗限制了超临界二氧化碳射流钻井技术的推广应用。在此基础上,自激振荡脉冲超临界二氧化碳射流技术降低了系统能耗,推动了碳利用、封存技术的应用。为丰富完善自激振荡脉冲超临界二氧化碳射流理论,开展腔径比对于自激振荡脉冲超临界二氧化碳射流性能的影响研究。基于流场结构角度,采用数值模拟优选出适用于自激振荡脉冲超临界二氧化碳射流的腔径比范围,分析腔径比对射流脉冲性能的影响。开展不同腔径比条件下,自激振荡脉冲超临界二氧化碳射流的脉冲压力测试实验,得出腔径比对于自激振荡脉冲超临界二氧化碳射流脉冲压力的影响规律。采用自激振荡脉冲超临界二氧化碳射流破煤岩实验系统,开展不同腔径比条件下的自激振荡脉冲超临界二氧化碳射流破煤实验,对比验证不同腔径比条件下的射流脉冲性能。结果表明:腔径比并非孤立的影响因素,其与上游喷嘴直径相关共同影响射流的脉冲性能及破煤效果。不同的上游喷嘴直径存在与其匹配的最优腔径比,匹配度越高,自激振荡脉冲超临界二氧化碳射流的脉冲压力越大、破煤效果越好。上游喷嘴直径分别为2.6,2.4 mm,腔径比分别为3.5,3.0时,自激振荡脉冲超临界二氧化碳射流的脉冲性能最佳,射流破煤效率最高。

Low well wall stability and low permeability of the coal seam are key factors limiting the extraction of coalbed methane.Supercritical carbon dioxide jet drilling technology has its unique advantages in coalbed methane extraction.Due to its high density,low viscosity and strong diffusivity,it not only enhances well wall stability and recovery rates,but also enables underground storage of carbon dioxide.However,the high-energy consumption of the system limits the application of supercritical carbon dioxide jet drilling technology.On this basis,the self-excited oscillation pulsed supercritical carbon dioxide jet technology reduces the system energy consumption and promotes the application of carbon utilization and storage technology.In order to enrich and improve the theory of self-excited oscillation pulsed supercritical carbon dioxide jet,the effect of cavity diameter ratio on the performance of self-excited oscillation pulsed supercritical carbon dioxide jet was investigated.Based on the flow field structure,various numerical simulations were used to select a range of cavity diameter ratios suitable for the self-excited oscillation pulsed supercritical carbon dioxide jets and to analyze the effect of cavity diameter ratio on the pulse performance of the jets.The effect of the cavity diameter ratio on the pulse pressure of the self-excited oscillation pulsed supercritical carbon dioxide jet was investigated.The self-excited oscillation pulsed supercritical carbon dioxide jet breaking experiments were carried out using the self-excited oscillation pulsed supercritical carbon dioxide jet rock breakage experimental system under different cavity diameter ratios to compare and verify the pulse performance of the jet under different cavity diameter ratios.The results show that the cavity diameter ratio is not an isolated factor,but is related to the upstream nozzle diameter to influence the pulse performance of the jet and the coal breakage effect.The higher the matching ratio,the higher the pulse pressure of the self-excited oscillation pulsed supercritical carbon dioxide jet and the better the coal breakage effect.When the upstream nozzle diameters are 2.6 mm and 2.4 mm,and the cavity diameter ratios are 3.5 and 3.0 respectively,the pulse performance of the self-excited oscillation pulse supercritical carbon dioxide jet is the best and the coal breakage efficiency is the highest.