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欠平衡钻井钻遇气层时,地层气体会以小气泡的形式侵入井筒,气侵量是欠压值及打开储层厚度的函数。现有计算环空气泡上升速度的方法仅考虑单个气泡的膨胀上升,没有充分考虑气泡融合特性对气泡上升速度的影响。本文考虑了气侵过程中气泡碰撞、液相湍流等综合因素,随着气泡沿井筒的不断上升,建立了环空气泡上升速度计算模型,在此基础上,提出了在气侵期间,气泡上升速度随半径的增加而加快,并得出考虑气泡融合特性可以更准确地计算环空气泡上升速度的结论。
When an underbalanced drilling hole is encountered, the formation gas intrudes into the wellbore in the form of small bubbles. The gas intrusion volume is a function of the under-pressure and the thickness of the reservoir. The existing methods for calculating the rising velocity of annular air bubbles consider only the expansion and rise of a single air bubble, and do not sufficiently consider the influence of bubble fusion characteristics on the bubble rising velocity. In this paper, we consider the comprehensive factors such as bubble collision and liquid turbulence in the process of gas invasion. With the rising of the bubble along the wellbore, a model for calculating the ascending velocity of the ring-shaped bubble is established. On this basis, The velocity accelerates with the increase of radius, and the conclusion that bubble bubble velocity increases with the bubble fusion characteristics can be calculated more accurately.