超临界CO_(2)喷射压裂射流密封机理

Isolation Mechanism during Supercritical Carbon Dioxide Jet Fracturing

超临界CO_(2)(SC-CO_(2))喷射压裂技术有望成为非常规油气资源的高效开发手段。为了探明其射流密封机理,开展了SC-CO_(2)喷射压裂作业时环空、孔眼及裂缝中的流场数值模拟研究。结果表明:SC-CO_(2)喷射压裂作业时SC-CO_(2)射流在环空附近形成低压区,促使环空流体进入地层孔眼而不进入已压开裂缝中,从而实现射流密封;SC-CO_(2)喷射压裂的射流密封效果与喷嘴压降和喷嘴直径正相关,与套管孔径和环空压力反相关,而受到SC-CO_(2)流体温度的影响极小;在相同的模拟条件下,SC-CO_(2)喷射压裂的射流密封效果强于水力喷射压裂。

Supercritical carbon dioxide(SC-CO_(2))jet fracturing is expected to be an efficient technique for developing the unconventional oil and gas resources.To verify the isolation mechanism during SC-CO_(2) jet fracturing,the flow fields within the annulus,cavity and fracture of SC-CO_(2) jet fracturing were simulated with computational fluid dynamics method.The results indicates that during SC-CO_(2) jet fracturing SC-CO_(2) jet will generate a low-pressure region in the annulus,which will force the annulus fluid into the target formation cavity,instead of flowing into the previous fractured zones.Moreover,the isolation effect of SC-CO_(2) jet fracturing increase with the growth of jetting pressure and diameter of the nozzle,decrease with the growth of casing hole diameter and annulus pressure,and is not affected by SC-CO_(2) temperature,and SC-CO_(2) jet fracturing has stronger isolation effect than water jet fracturing.