【摘要】 在井壁稳定分析中,将疏松砂岩储层作为孔隙介质,依据孔隙热弹性小变形应力叠加原理,建立温度及井壁渗流等多种因素影响下,疏松砂岩储层井眼周围有效应力计算模式,结合井壁岩石破坏准则,给出了地层坍塌压力、破裂压力计算模式,研究了温度变化和井壁渗流等因素对安全钻井液密度窗口的影响规律,为确定疏松砂岩地层的安全钻井液密度窗口提供理论依据。研究结果表明,随着地层渗透性增大,地层破裂压力降低,坍塌压力升高,安全钻井液密度范围变小;井壁温度降低,地层坍塌压力和破裂压力同时降低,安全钻井液密度范围变窄;井壁温度升高,地层破裂压力和坍塌压力同时升高,安全钻井液密度范围变宽。但在温度降低及井壁渗流综合影响下,地层承压能力大幅下降,地层坍塌压力也降低,为了保证钻井安全,应适当降低钻井液密度。更多还原

【Abstract】 During the well bore stability analysis, the unconsolidated sand formation is considered as pore medium. Considering temperature and seepage property for unconsolidated sandstone, and according to thermoplastic theory, calculation mode for borehole effective stress distribution was set up, and effective stress distribution rule was investigated. Combined with formation failure mode, collapse pressure and fracture pressure calculation mode were deduced, and how temperature change and well bore seepage property influence safe mud density window were studied. Results show that, 1) with the formation permeability increasing, the formation fracturing pressure decreases, the caving pressure increases and the safe drilling fluid density window is narrowed; 2) when the well bore temperature decrease, the formation caving pressure and fracturing pressure decrease together, and the safe drilling fluid density window is narrowed; 3) when the well bore temperature increases, the formation caving pressure and fracturing pressure increase together, and the safe drilling fluid density window is widened. While in comprehensive influence of temperature decrease and well bore seepage, the formation bearing pressure decreases substantially, and the caving pressure decreases also. Therefore, to guarantee safe drilling, the drilling fluid density should be reduced properly.更多还原