关键词: 井壁稳定,   , 失稳机理,   , 多元协同,     , 防塌钻井液

Abstract: The formation mineral composition, micro structure and physicalchemical properties of representative shale samples of deep complex shale formation in Yuguo area of Tuha oilfield were analyzed by Xray diffraction, Scanning Electron Microscope, swelling and dispersion tests, specific surface area capacity measurement, specific water capacity and other experimental methods the mechanisms of wellbore instability in deep complex formation were made clear. A three cooperation principle for stabilizing wellbore by improving the performance of drilling fluid was put forward. This method includes the technologies of sealing and consolidating side wellbore physicchemically, enhancing inhibition against hydration and providing the effective stress support of reasonable drilling fluid density. The responding antisloughing drilling fluid which is suitable to deep complex formation in Yuguo area was developed by selecting all kinds of additives and optimized formulation. The site trial indicates that this drilling fluid has great capacity to antisloughing and sealing layer. The drilling fluid is easy to manage and maintain. Using this drilling fluid can improve drilling velocity and save drilling cost.

Key words: Wellbore stability,    ,  Instability mechanism,     ,  Multicomponent combination,    , Antisloughing drilling fluid