基于赫—巴模型的微小井眼钻井连续油管内钻井液流阻计算分析

微小井眼连续油管(CT)钻井技术具有诸多优点,但微小井眼尺寸小,导致钻井液流动空间小、排量较小、返速较高、循环损失较大,限制了该技术的推广使用。为解决微小井眼CT钻井循环钻井液流阻过大的问题,基于赫—巴模型,结合微小井眼CT钻井的特点,计算了CT内钻井液流阻,探讨了CT内钻井液流阻与钻井液平均流速、CT长度或井深、CT内水眼直径、滚筒直径等参数的关系。研究结果表明:①滚筒上CT内流阻随钻井液流速增大而呈线性增加且增加幅度更大,使用小排量进行钻进能降低滚筒上的流阻;②滚筒上和井筒中CT内钻井液流阻均随CT的长度增加呈线性增加,而随着CT内水眼直径增加呈线性减小,钻深井时,可使用大管径进行钻进;③CT内钻井液流阻受滚筒直径的影响很小,但随钻井液的流速增大呈线性增加,因此当滚筒上缠绕的CT较长时,可使用多个滚筒进行缠绕,以降低滚筒上CT内钻井液流阻。结论认为,寻找控制和减小微小井眼钻井CT内钻井液流阻的方法和优选适合CT钻井的相关参数,有助于加快该技术的推广应用。

Calculation and analysis of drilling fluid flow resistance in coiled tubing for slim-hole drilling based on the Herschel-Buckley Model

The coiled tubing (CT) drilling technology in slim holes with many advantages has been unfortunately restricted due to tight space for fluids flowing, small flow rates, high flowback rates, huge loss in circulation. In order to solve the problem of overly large fluids flow resistance in the CT drilling, we calculated the flow resistance of drilling fluid in CT based upon the Herschel–Buckley Model and the features of this technology, and discussed the relationships between the fluids flow resistance and the other factors such as average flow rates of fluids, CT length (or well depth), CT water-hole diameter, tubing roller diameter, etc. The following findings were achieved. (1) On the tubing roller, CT internal flow resistance increases linearly with the drilling fluids flow rate and drilling fluids with small flow rates will decrease the flow resistance on the roller. (2) Both on the tubing roller and in the wellbore, CT drilling fluid flow resistance increases linearly with CT length but decreases linearly with CT internal water-hole diameter; therefore, large-diameter CTs will be better for drilling deep wells. (3) The tubing roller diameter has little effect on the CT fluids flow resistance, which increases with the fluids flow rate linearly; The CT wound on the roller is long enough to use multiple rollers so as to reduce the flow resistance of fluids in CT. In conclusion, this study provides a reference for controlling and reducing the CT fluids flow resistance and optimizing the relevant parameters, helpful to accelerate the popularization and application of this technology.