钻井液脉冲沿井筒传输的多相流模拟技术

在随钻测量系统和闭环钻井系统中,把钻井液看作气相、液相和固相的多相流体,研究了钻井液脉冲的传输速度计算方法,分析了钻井液的组份含量和特性对脉冲信号传输速度的影响.根据多相流的动力学方程,建立了模拟钻井液脉冲动态传输特性的数学模型.研究结果表明,钻井液中的气相和固相将对钻井液密度和压缩性产生影响,进而影响钻井液脉冲的传输速度和传输特性.随着钻井液密度和压缩性的提高,脉冲信号的传输速度降低.脉冲传输速度对含气量非常敏感,随着含气量的增加,传输速度迅速下降;沿井筒往复传播的钻井液脉冲在系统边界处将产生折射和反射,类似于阻尼振荡;钻井液粘度是影响脉冲信号衰减速度的一个重要因素.该数值模拟方法简便易行,可以替代部分室内实验,对现有钻井液脉冲传输系统的改进以及新系统的开发都具有参考价值.

Multiphase simulation technique of drilling fluid pulse transmission along well bore

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 oscilla- tion 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.