Shallow water flow is a geohazard encountered in deepwater drilling. It is often characterized by excessive water flow into the wellbore caused by the pressure difference between overpressured sediments and the wellbore, and it usually leads to serious well control problems and may eventually result in the loss of a well. Many research efforts focused on the identification of shallow water flow zones and the associated water flow in the drilled wellbore. Not many studies investigated the coupled hydromechanical behaviors in sediments during the occurrence of shallow water flow, while such behaviors are directly related to uncontrolled flow in the wellbore and solid deformation. Based on a coupled hydraulic-mechanical model and finite element methods, this work investigates the temporal-spatial evolutions of near-well pressure and stress induced by shallow water flow. Hydraulic behaviors in the deepwater shallow sediments are described by saturated fluid flow in porous media while mechanical behaviors in the sediments are depicted by linear elasticity. Finite element methods are used for the numerical solution to the coupled hydraulic-mechanical formulation. The study then conducts a series of parametric studies to quantitatively understand the effects of relevant parameters on pressure, stress, and uncontrolled flow into the wellbore. Results indicate that overpressure has the most significant impact while Young’s modulus has the most limited impact on spatial-temporal pressure/stress evolutions and the uncontrolled water production in the wellbore. Permeability, porosity, water viscosity, and water compressibility all have certain effects on near-well physical characteristics and wellbore water production. In addition, it is noted that pressure drainage and induced stress are more significant when it is closer to the wellbore. This numerical study helps to quantitatively identify the most influential parameters related to shallow water flow and calculates the water mass flow loaded in the wellbore.

中文翻译：

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基于数值模拟的深水钻井浅层沉积物浅水流耦合流体力学行为参数研究

浅水流是深水钻井中遇到的地质灾害。其特点是由于超压沉积物与井筒之间的压力差，导致大量水流入井筒，通常会导致严重的井控问题，最终可能导致一口井的损失。许多研究工作集中在浅水流带的识别和钻井孔中的相关水流的识别上。浅水流发生过程中沉积物的耦合流体力学行为研究较少，而这些行为与井筒中不受控制的流动和固体变形直接相关。基于耦合的水力-机械模型和有限元方法，这项工作研究了浅水流引起的近井压力和应力的时空演变。深水浅层沉积物中的水力行为用多孔介质中的饱和流体流动来描述，而沉积物中的力学行为用线弹性来描述。有限元方法用于对耦合的液压机械公式进行数值求解。然后，该研究进行了一系列参数研究，以定量了解相关参数对压力、应力和不受控制的流入井眼的影响。结果表明，超压的影响最显着，而杨氏模量对时空压力/应力演变和井筒中不受控制的产水量的影响最有限。渗透率、孔隙率、水粘度、水压缩性对近井物理特性和井筒产水都有一定的影响。此外，值得注意的是，越靠近井筒，压力排放和诱导应力越显着。这种数值研究有助于定量确定与浅水流相关的最有影响的参数，并计算井筒中加载的水质量流量。