侵入气体沿井筒的上升规律研究

地层气体侵入井筒后形成气液两相流动体系,气体沿井筒向上滑脱运移,随着所受压力的降低其发展变化过程会很快,如果不及时处理就会演变为井涌、井喷,甚至井喷失控.因此,准确的预测侵入气体沿井筒的上升规律,有助于认识气侵发展过程,同时为现场采取井控措施提供理论依据,有效避免井下复杂事故.基于侵入气体沿井筒运动的力学特性,建立了气体的上升速度模型,模型模拟分析表明:地层渗透率越高、机械钻速越快、单位时间内侵入井筒的气体量越多、气体上升速度越快,井底压力波动越大;施加一定的井口回压可以有效抑制气体的膨胀运移.

Rising Migration Rule of Gas Kick in Wellbore

Gas-liquid two-phase flow is formed when gas kick has been taken during drilling.Gas kick migrate from bottomhole to surface.With the forces exerting on the gas kick decreases,gas develops quickly which can lead to a catastrophe if not dealt with properly.The precise rising velocity of gas kick is not only help to recognize the development of gas kick,but also provide theoretical basis for well control operation which can avoid drilling accidents effectively.Based on the force analysis and mass conservation,the rising velocity of gas kick is calculated.Model application shows that the higher formation permeability,the faster rate of penetration,and the more gas kick volume,bubble migrate faster and bottomhole pressure fluctuate severe.Applying a certain wellhead back pressure can inhibit the expansion and migration of gas kick effectively.