基于量纲分析的沥青钻井液重力置换规律研究

EXPERIMENTAL STUDY ON GRAVITY DISPLACEMENT MECHANISM OF ASPHALT-DRILLING FLUID BASED ON DIMENSIONAL ANALYSIS

伊朗雅达油田Kazhdumi地层沥青质稠油发育,钻井过程中裂缝常发生置换式双向流动,严重影响钻井安全,迫切需要开展重力置换规律研究,形成有效的防控技术。为了深入揭示置换发生的条件、发展规律、影响置换量的因素,文章研制了一套基于真实裂缝的可视化重力置换实验装置,研究了裂缝宽度、钻井液与沥青密度差、沥青与钻井液黏度差等对重力置换的影响。引入量纲分析理论,推导出了重力置换量的准则方程。结果表明,缝宽对置换量的影响较大,随着裂缝宽度的增加,置换量不断增加;置换量随钻井液与沥青密度差的增大而增加;随着沥青与钻井液黏度差的增大,置换量将显著减小,尤其从低黏度差到高黏度差,减小的幅度更大。提出了“化学封堵+控压钻井+物理阻隔”的综合防控技术,现场应用效果显著,可为国内外同类地层安全钻进借鉴参考。

Asphaltic heavy oil is developed extensively in Kazhdumi Formation of Yada Oilfield in Iran.Gravity replacement often occurs during drilling,which seriously affects the drilling safety.It is urgent to study the law of gravity displacement and preventive and control measures.In order to thoroughly reveal the conditions of displacement,development rules and factors affecting displacement amount,a set of visual gravity displacement experiment device is developed with real crack as the research object,and the effects of crack width,density difference between drilling fluid and asphalt,and viscosity difference between asphalt and drilling fluid on gravity displacement are studied.By introducing dimensional analysis theory,the criterion equation for the calculation of gravity displacement is derived.The results show that the effects of crack width on the displacement is very obvious.As the crack width increases,the displacement increases.The displacement increases with the drilling fluid-the asphalt density difference.While the viscosity difference between the asphalt and the drilling fluid increases,the amount of displacement will be significantly reduced,especially from low viscosity difference to high viscosity difference,the greater the reduction.A comprehensive prevention and control technology of"chemical plugging+pressure-controlled drilling+physical barrier"is put forward,and the field application is remarkable,which can be used as a reference for safe drilling in similar formations at home and abroad.