控压钻井井筒多相流体瞬态变质量流动理论及工况解释方法研究

In the current exploration and development of oil and gas resources, the proportion of drilling complex formation is increasing, drilling efficiency and safety problem have become more and more important. Managed Pressure Drilling can control wellbore pressure accurately, improve the ROP, enhance the well control ability, effectively reduce the pressure-related drilling problems, has become the main method for improving drilling operation safety and reducing cost. Different from the convention drilling, fluid flowing conditon, the coupling of formation fluid and wellbore fluid, wellhead backpressure are all have a significant effect for the wellbore pressure system in MPD operation. However, as the basic MPD theory research of our country is in a late start, the understanding of the mechanism of MPD wellbore flow is not clear, and the downhole parameter monitor technology and the downhole conditions interpretation are relatively backward compared with foreign countries. This problem restrict the popularizing and application of MPD technology. This project will establish the wellbore multiphase transient variable mass flow model through theory research, explore the measurement method of complex fluid dielectric constant, accurately analyse and caculate the situation of wellbore pressure change, monitor the coupling conditon of formation and wellbore, provide the theoretical basis for MPD technology, and the efficient monitor method for pressure interpretion.

目前在我国油气资源勘探开发过程中，复杂地层钻井比例不断加大，钻井安全和效率问题日益突出。控压钻井能对井筒内压力实施有效、准确控制，提高机械钻速，减少钻井事故的发生,已经成为提高钻井作业安全性和降低成本的重要手段。控压钻井较之常规钻井有很大不同，井筒内流体流动状态、地层流体与井筒流体耦合、井口回压大小等均对井筒压力体系产生重要影响，但目前我国控压钻井技术尚处起步阶段，与国外相比，基础理论研究薄弱，对控压钻井过程中井筒内流体流动的机理研究不深入，井下参数检测和工况解释方法相对落后。这些问题制约了控压钻井技术在我国的推广、应用。本项目拟通过理论研究建立控压钻井过程中井筒内多相流体瞬态变质量流动水力模型，探索复杂流体介电常数测量方法，以准确分析计算井筒压力变化情况和检测地层流体与井筒流体耦合情况，为控压钻井技术提供理论支撑，为工况解释提供有效地检测方法。

目前在我国油气资源勘探开发过程中，复杂地层钻井比例不断加大，钻井安全和效率问题日益突出。控压钻井能对井筒内压力实施有效、准确控制，提高机械钻速，减少钻井事故的发生，已经成为提高钻井作业安全性和降低成本的重要手段。本项目通过基于变质量流动的控压钻井井筒压力波动数值模拟研究和垂直井筒漏失室内模拟实验与压力波传递实验，对流体的排量、粘度，质量交换的位置、量级以及节流阀的动作进行了敏感性分析，描述了控压钻井过程中井筒内多相流体瞬态变质量流动条件下的井筒压力波动规律；开展了井筒流体介电常数变化规律研究，并探索复杂流体介电常数测量方法，以准确分析计算井筒压力变化情况和检测地层流体与井筒流体耦合情况；结合控压钻井工艺特点，建立了基于无迹卡尔曼滤波的井下双测点压力实时解释的反演模型，以及正常工况下的井筒水力学校正模型，首次将气侵/漏失速率以及气侵/漏失点位置作为反演参数，理论上可以实现针对井下气侵和漏失工况实现准确的量化解释和分析。本项目研究成果为控压钻井技术提供理论支撑，为工况解释提供有效地检测方法。