页岩气钻水平井段岩屑床破坏及岩屑运移机理研究

针对页岩气开采成本高,以及清水钻井在垂直井段具有成本低和机械钻速快的优点,且页岩气清水钻井岩屑运移规律尚认识不清。基于流体力学基本控制方程和湍流输运方程,建立了三维井眼环空岩屑运移模型。使用全隐式多网格耦合求解技术进行数值计算。利用该模型开展清水钻水平井段岩屑运移可行性研究,以及钻井液排量、岩屑床高度、岩屑粒径、清水黏度和钻柱转速对岩屑运移规律的影响研究。研究表明,在水平井段清水钻井液携岩是可行的,数值计算结果对比,得出钻井液排量、岩屑床高度和岩屑粒径是影响清水携岩能力的敏感参数。建议钻井过程岩屑床厚度不要超过井眼直径的10%,岩屑颗粒直径为5 mm左右,根据钻井需要选用合适的钻井液排量、钻井液黏度和钻柱转速。清水钻井岩屑运移机理研究可为页岩气安全高效开采提供技术支撑,同时将加快页岩气工程的开发进程。

Cuttings bed damage and cuttings transport mechanism study of horizontal well for shale gas

For high-cost of shale gas exploitation, and the advantage of low cost and faster ROP for water drilling in the vertical well section. So it is necessary to carry out cuttings transport mechanism of shale gas for water drilling. Based on the basic equations of fluid mechanics and turbulence transport equations, the cuttings transport model of three-dimensional wellbore annulus is established, numerical simulation using a fully implicit coupled multigrid solver technology. The model is verified the feasibility using the experimental data. Using this model to carry out the feasibility study of cuttings transport for water drilling in horizontal well. And also study the effect law of displacement of drilling fluid, cuttings bed height, cutting diameter, the viscosity of water and rotational speed of the drill string. Result has shown that water drilling both raising speed and raising efficiency comparing air drilling and aerated mud drilling. The result shows cuttings carrying capacity is basically the same for the water drilling and mud drilling, thus the cuttings carrying capacity is feasible for the horizontal well with drilling water. The numerical result shows the sensitive parameters of the displacement of drilling fluid, cuttings bed height and particle size for affecting cuttings carrying ability of water drilling. We recommend the cuttings bed thickness should not exceed 10% of the diameter of the borehole, and cuttings particle diameter is about 5mm. According to the need of drilling using the appropriate drilling mud displacement, drilling fluid viscosity and rotational speed of the drill string. Cuttings transport mechanism of water drilling can provide technical support for safe and efficient exploitation of shale gas, and will accelerate the development process of shale gas project.