气体钻进过程地层液体侵入量计算及携液规律研究

LIQUID INFLUX CALCULATION AND STUDY ON LIQUID-CARRYING DURING GAS DRILLING

气体钻井具有大幅提高钻速和单井产量、有效防止恶性井漏的技术优势,是深井提速、大规模低品位油气资源高效勘探开发的关键技术方法,然而一旦地层出液后,井筒内的岩屑与地层侵入液相互作用,可能造成井内泥包和井眼堵塞的井下复杂事故,常常导致钻井失败。文章基于随钻试井和井筒多相流理论,建立了气体钻井过程中非均质圆形封闭地层瞬态产液理论模型,并提出了考虑液滴大小和液滴变形特征的气体携液能力计算方法。通过室内实验台架模拟了气体钻井地层出水后的动态携液过程,表明理论携液量与实际携液量相符。结合现场气体钻井实例计算得出地层的产液量与地层物性、钻井参数等相关;增加注气量和降低气液两相界面张力能够有效地减小液滴尺寸,提高气体钻井的携液能力。

Gas drilling is the critical technique to improve ROP in deep well and develop large-scale low grade oil and gas resources due to these advantages of high penetration rate and individual-well producing rate. However, formation liquid and the cuttings will interact and then cause underground complex accidents of drill bit balling and borehole plugging to drilling failure when formation liquid invade into wellbore. Based on the well testing while drilling and multiple phase flow theory, the transient liquid production model of non-homogeneous circular sealed formation during the gas drilling was established and the calculation method of liquid-carrying capability considering the size and deformation characteristics of droplets was put forward. The dynamic liquid-carrying process after liquid production was simulated by the lab. experiment on the test stand, which indicated that theoretical values agree basically with practical values of liquid-carrying capability. Combining with the gas drilling case, it was showing that the liquid production was related to formation properties and drilling parameters. The increasing of gas injection volume and reducing of the gas-liquid interfacial tension could effectively reduce the droplet size and enhance the liquid-carrying capacity of the gas drilling.