预测宾汉流体中最大下套管速度的实用方法

A PRACTICAL METHOD OF PREDICTION OF MAXIMUM PIPE INTRODUCING SPEED IN BINGHAM FLUID

汪海阁 苏义脑

Wang Haige Su Yinao

总公司石油勘探开发科学研究院钻井所

波动压力的大小与井眼系统稳定密切相关,而管柱下放速度又是影响波动压力的主要因素。因此,基于平衡压力钻井和井控要求而确定合理的管柱下放速度,对确保安全快速钻井具有重要意义。文中以宾汉流体为例,从理论上推导了控制管柱最大下放速度的非线性方程组,并在地层破裂压力梯度给定的情况下分析了影响管柱最大下放速度的主要因素。计算结果表明:随钻井液屈服值、塑性粘度增加,最大下放速度应该减小;随环空内外管径比增加,最大下放速度应该减小;随地层破裂压力梯度增加,最大下放速度可以增大。文中还给出了计算实例。

Pressure surges are closely related with stability of borehole system and the pipe introducing speed is a key factor that influences pressure surges. Therefore determination of rational pipe introducing speed required by balanced drilling and well control is very important for ensuring a safe and fast drilling. Taking Bingham fluid for an example, the paper deduced theoretically a group of non-linear equations of control maximum pipe introducing speed and analyzed the principle factors that influence the maximum pipe introducing speed under conditions of determined formation break-down pressure gradient. The calculated data shown that the maximum pipe introducing speed decreases with increasing of yield point and plastic viscosity of the drilling fluid and enlargement of ratio of outside diameter over inside diameter of the borehole annulus and it increases with increasing of formation break-down pressure gradient. Some calculation samples were also provided in this paper.

10.3969/j.issn.1000-7393.1997.03.002