一种起下钻引发的两相稳态波动压力经验模型

Fluctuating pressure caused by tripping in two phase steady flow

考虑气体的压缩性、井筒深度及黏附力等参数,建立了起下钻引发的两相稳态波动压力经验模型,以一个具体的工程实例为例,采用龙格库塔方法,借助计算机编程对其求解。结果表明:空隙率减小、钻井液密度增大、井深增大及过快的起下钻速度均使井筒两相波动压力增大,使钻井安全密度窗口相应变小,允许最大起下钻速度减小;由于气体的混入,使气液两相的黏附力减小、压缩性增大,可适当加快下钻速度,这样不但不会压漏地层,更起到提高钻井时效的目的;利用经验公式计算波动压力可达到快速简捷的目的,可为钻井工程师提供理论基础及应用指南。

In consideration of gas compressibility, adhesion, wellbore depth, a new empirical model for fluctuating pressure caused by tripping in two phase flow is proposed based on two-phase flow model. The mathematical model is solved by using Runge-kutta method based on computer programming in one engineering example. Results show that, with the decreases of po- rosity,and the increase of drilling fluid density, well depth, and the quickly tripping speed, fluctuating pressure is increased in wellbore in gas-liquid two phase, the drilling safety density window is reduced, the maximum tripping speed is decreased. Due to the mixed gas, adhesion is reduced in two phase flow, and compressibility is generally increased. If the down movement speed of drill pipe can be increased in appropriate, the formation is not only not to leak, the drilling efficiency is increased. Experience model used to calculate fluctuating pressure can be fast, which can provide theoretical basis for drilling engineers and application guide .