环空气液两相流中气泡微观动态特征研究

The research which related to the field of underbalanced drilling, managed pressure drilling and well control (overflow, the process of killing),is one of the key basic research to optimize the drilling and safe drilling. Formation mechanism and dynamic characteristics of bubbles in annulus、the size and shape characteristics of the bubble、the force of the bubbles and migration law、the interaction between the bubbles and the drilling fluid and the interaction between bubbles and so on will affect the pressure distribution of the annulus, directly change the dynamic characteristics of the bottom hole pressure, thereby change the balance between the bottom hole pressure and formation pressure. So it is a great challenge to optimize the drilling and safe drilling. The project intends to study the dynamic behavior characteristics of micro-bubbles in the annular gas liquid two-phase through a large number of experiments and mechanism of simulation and create a new mathematical model to calculate and predict the dynamic variation of the annular pressure by MPD bottom hole pressure measurement data and wellhead pressure control data. It will solve scientific issues of unclear understanding of the micro-dynamic behavior characteristics of the bubble in annulus while drilling and study the micro-bubble dynamic behavior characteristics of annulus pressure. What's more, it has important academic value and is of great practical significance for real-time drilling optimization and security controls.

本项研究涉及的领域包括欠平衡钻井、控压钻井和井控（溢流关井、压井过程），是优化钻井和安全钻井的关键基础性研究方向之一。钻井过程中环空气泡的生成机理及动态特征、气泡的尺寸大小及形状特征、气泡的受力情况及运移规律、气泡之间及气泡与钻井液之间的互作用规律等都会影响环空压力分布，直接改变井底压力的动态特征，进而改变井底压力与地层压力之间的平衡关系，给优化钻井和安全钻井带来巨大挑战。本项目拟通过大量的实验研究和机理模拟对环空气液两相流中气泡的微观动态行为特征进行研究，并以控压钻井井底压力测量数据和井口控压数据为基础建立计算和预测环空压力动态变化规律的新型数学模型，拟解决当前对钻井环空气泡微观动态行为特征认识不清的科学问题，并在此基础上研究气泡微观动态行为特征对钻井环空压力场的影响规律，对钻井实时优化和安全控制具有重要学术理论价值和重大实际意义。

钻井过程中环空气泡的生成机理及动态特征、气泡的尺寸大小及形状特征、气泡的受力情况及运移规律、气泡之间及气泡与钻井液之间的互作用规律等都会影响环空压力分布，直接改变井底压力的动态特征，进而改变井底压力与地层压力之间的平衡关系，给优化钻井和安全钻井带来巨大挑战。本项目通过实验和机理模拟对环空气液两相流中气泡的微观动态行为特征进行研究，取得以下成果。.（1）进一步明确了气泡微观生成机理。通过实验模拟和机理分析，从井壁岩石孔隙中气体侵入和环空中随钻井液循环的破碎岩屑中气体侵入等多个方面对气体侵入井筒的微观过程和机理进行了研究。.（2）分析了井筒环境对气泡形态特征的影响规律。基于热质传递和气体膨胀等基本理论，研究了井筒中不同深度下温度、压力等关键环境变量对气泡大小、形状等主要特征参数的作用规律。.（3）揭示了气泡力学特征与运移规律。借助流体力学理论，模拟了气泡之间、气泡与钻井液之间的力学作用机理，重点研究了气泡的合并规律及环空中单个气泡的受力情况，对不同环空条件下气泡的运移规律进行了客观科学的研究。.（4）基本明确了气泡动态变化对环空压力分布规律的影响。在实验研究、机理模拟和理论研究的基础上，研究了气泡微观动态变化规律对环空压力分布的作用机理，建立了能够准确计算、预测环空井底压力、井口压力的理论模型，并通过与现场实测环空压力数据对比进行了验证。