重力置换式漏喷同存机理研究

Mechanism of Mud Loss and Well Kick due to Gravity Displacement

裂缝性地层在钻进过程中经常出现漏喷同存的情况,造成井控困难、井下复杂情况和储层伤害。但是,漏喷同存的机理目前还处于经验描述阶段,缺少基础理论研究和模型描述。针对直井钻遇单条裂缝时由于重力置换而引起的漏喷同存问题,研究了它的发生条件和气液两相流的流动特征,分别建立了气相模型和液相模型,并通过气液分界面将这两个模型耦合起来。模型计算与试验验证表明,对漏失速率和气体溢流量影响最大的因素是缝宽,其次是压差、钻井液流变性能;通过合理调节井筒压力和改善钻井液流变性能可减缓漏失和溢流。建立的模型与实验结果吻合较好,可为实际钻井工程中处理漏喷同存提供一定的理论依据。

Due to the complexity of naturally fractured formations, the occurrence of mud loss and well kick at the same caused the difficulty in well control, downhole complexity, and formation damage. At present, the mechanism of mud loss and well kick at the same is still under investigation and lack of basic theoretical investigation and model, description. For the problem of mud loss and well kick due to gravity displacement in vertical well with a single fracture encountered, the occurrence reason was investigated and characteristics of two phase flow was described. Gas and liquid model were developed and coupled by gasliquid interface. Simulation and experimental results indicate that the dominate factor affecting leakage rate and gas flow is fracture width, followed by differential pressure and drilling fluid rheological properties. The main measures of mud loss and well kick control are to adjust wellbore pressure and rheological properties. The simulation result agrees with experiment results. It can provide a theoretical basis in drilling with mud loss and well kick at the same time.