超临界二氧化碳喷射压裂孔内流场特性

摘要

为了证实利用超临界二氧化碳( CO2)流体进行喷射压裂的可行性，利用Span-Wagner气体状态方程建立超临界CO2流场的计算流体力学模型，模拟超临界CO2喷射压裂过程中的孔内流场。结果表明：在喷嘴压降相同的条件下，与水射流相比，超临界CO2射流的射流速度更高，射流核心区更长；超临界CO2喷射压裂具有比水力喷射压裂更强的射流增压效果，更容易压开地层；超临界CO2射流具有显著的焦耳-汤姆逊效应，会导致温度下降，在压裂施工中应合理控制喷嘴压降，以防发生冰堵事故；超临界CO2的密度主要受压力影响，通过调节压力就能有效控制，可适应不同的地层温度条件。%TO verify the feasibility Of supercritical carbOn diOxide ( SC-CO2 ) jet fracturing, a cOmputatiOnal fluid dynamic mOdel was established based On Span-Wagner state equatiOn tO simulate the flOw field in the cavity during SC-CO2 jet fractu-ring. The results shOw that in cOmparisOn with water jet, the SC-CO2 jet has higher jet energy and experiences less energy at-tenuatiOn. It alsO has higher pressure bOOsting effect than water jet fracturing. JOule-ThOmsOn effect can happen during SC-CO2 jet and lead tO temperature decrease. TherefOre nOzzle pressure drOp shOuld be reasOnably cOntrOlled during the jet frac-turing prOcess tO avOid ice blOck. The density Of SC-CO2 is mainly influenced by pressure instead Of temperature. SO it can be cOntrOlled by adjusting pressure fOr it tO wOrk under different fOrmatiOn temperatures.