关键词: 随钻测量, 钻井液脉冲, 闭环钻井, 多相流, 数值模拟

Abstract: In the measurement while drilling and closed-loop drilling systems,the drilling fluid was taken as a gas-liquid-solid multiphase.A method for calculating the pulse velocity in drilling fluid travel was proposed.The influences of component of drilling fluid and free-gas content in drilling fluid on the pulse velocity of drilling fluid were analyzed.According to multiphase fluid dynamics,the mathematical model and methods to simulate pulse transmission behavior of drilling fluid were developed.The research result demonstrated that the solid-phase and free-gas contents in drilling fluid had some influences on the density and compressibility of drilling fluid and further on the pulse velocity and transmission behavior of drilling fluid.The pulse velocity of drilling fluid declined with increase of density and compressibility of drilling fluid.Also,the pulse velocity of drilling fluid declined with increase of gas content.The drilling fluid pulse transmitting up and down along well bore had refraction and reflection components similar to damped oscillation at the boundary of system.The viscosity of drilling fluid has important influences on the pulse attenuation of drilling fluid.The proposed model and methods can be used to simulate transmission behavior of drilling fluid pulse along well bore.The simulation process can replace laboratory experiments for improving the existing performance of drilling fluid pulse system and for developing new drilling fluid pulse system.

Key words: measurement while drilling, drilling fluid pulse, closed-loop drilling, multiphase flow, numerical simulation