Dynamic Simulation of Drilling Vibrations for Design of Drill Strings and Downhole Tools

在恶劣的加拿大环境中，如海上，石油钻井平台停机成本极高（接近100万美元/天）。与振动相关的管道和井下工具故障是常见的，其中大位移定向威尔斯井带来了与垂直威尔斯井不同的挑战。 这项研究将导致一个计算效率高的动态振动模型的斜井威尔斯。 该模型将用于改进井下部件的设计，并研究有意振动的潜在好处。 振动可分为轴向（沿着管道长度）、扭转（扭曲）或横向（管道弯曲）。 因为这些振动是相互依赖的，所以需要一个模型来预测所有三个。 为了简化计算和节省计算时间，许多先前的模拟对所考虑的振动类型进行了限制;然而，这些模型不会捕捉到某些对于预测部件寿命和钻井性能很重要的现象。钻柱由一个垂直部分组成，该部分由相对较细的受拉管道组成，过渡到弯曲的“建造”部分，并以称为钻铤的较重管道结束，该钻铤沿着钻头，传感器和用于引导钻头的工具一起组成“井底组件”或BHA。 垂直段和建造段将采用刚性质量和旋转惯性之间的一系列集中轴向和扭转弹簧进行建模，并采用钻井液阻尼。 在构建部分，将通过考虑摩擦力和接触力的各种数学模型来细化扭矩和阻力预测。 因为BHA管最易受与轴向和扭转运动高度耦合的横向振动的影响，所以BHA将被建模为一系列三维振动圆柱体，这些圆柱体被弹簧约束，沿着有井筒摩擦力、冲击力和接触力。 一旦这种更简单、运行更快的模拟方法通过实验和更复杂但速度更慢的有限元模型进行验证，它将用于预测管道和其他组件从表面到最终深度的载荷。 载荷将用于更详细的组件级有限元模型中，以预测局部应力和应变，然后预测其疲劳寿命。 疲劳失效是指由于重复或变化的载荷而导致的过早失效。 该模型还将用于研究有意引入振动的可能性，以减少摩擦扭矩和向前移动管道的阻力，增加钻头和岩石之间的钻削力，或减少可能导致管道卡住的岩屑堆积。 提高油井钻探效率将增加盈利能力，并有利于资源密集型的加拿大经济。 减少钻井故障和提高油井质量将减少所需的钻井总量，并减少对地面的环境影响。

Oil rig downtime is extremely costly (approaching $1M/day) in harsh Canadian environments such as the offshore. Vibration-related failures of pipes and downhole tools are common, with extreme reach directional wells imposing different challenges than vertical wells. This research will result in a computationally-efficient dynamic vibration model for deviated wells. The model will be used for improved design of downhole components, and to study the potential benefits of intentional vibration. Vibration can be classified as axial (along the pipe length), torsional (twisting), or lateral (bending of the pipes). Because these vibrations are interdependent, a model is needed that can predict all three. Many prior simulations place restrictions on the types of vibration considered, in the interests of simplicity and computation time; however, such models will not capture certain phenomena important for predicting component life and drilling performance.***The drillstring consists of a vertical portion made of relatively thin pipes in tension, transitioning into a "build" section that is curved, and ending with heavier pipes called drill collars that, along with the bit, sensors, and tools for steering the bit, make up the "bottom-hole assembly", or BHA. The vertical and build sections will be modeled with a series of lumped axial and torsional springs between rigid masses and rotary inertias, with damping due to drilling fluid. In the build section torque and drag force prediction will be refined by consideration of various mathematical models of friction and contact force. Because the BHA pipes are most susceptible to lateral vibrations that are highly coupled to axial and torsional motion, the BHA will be modeled as a series of three-dimensionally vibrating cylinders constrained with springs, along with wellbore friction, impact, and contact forces. Once this simpler, faster-running simulation method is validated with experiments and more complex but slower finite element models, it will be used to predict the loads on pipes and other components as they progress from the surface to their final depth. The loads will be used in a more detailed component-level finite element model to predict local stresses and strains, after which their fatigue life will predicted. Fatigue failure refers to premature failure due to repeated or varying loads. The model will also be used to study the potential for intentionally-introduced vibration to reduce friction torque and resistance to moving the pipes forward, to increase drilling force between the bit and rock, or to reduce the buildup of rock cuttings that can cause the pipe to stick. Improving the efficiency of oil well drilling will increase profitability and benefit the resource-intensive Canadian economy. Reduced drilling failures and improved well quality will reduce the total amount of drilling required and lessen environmental impact at the surface.