Abstract:Shale gas reservoir has strong anisotropy and wellbore instability is prone to occur. Wellbore stability model in gas shale was created based on transverse isotropic theory and single plane of weakness theory. Core samples of gas shale were tested to research the influence of drilling fluid on shale matrix strength and bedding plane strength. The influences of dip of bedding,drilling azimuth,drilling time and drilling fluid,etc. on collapsing pressure of horizontal wells were analyzed. The results show that when the dip of bedding is smaller than 45°,failure along the bedding plane will take place on the wellbore wall;when the dip of bedding is higher than 45°,failure in shale matrix will take place in some drilling azimuth;drilling horizontal wells near the direction of minimum horizontal stress may easily lead to wellbore collapsing;with the hole open time increasing,the collapsing pressure will raise gradually;and the failure mode of wellbore wall may change from the initial shale matrix failure into bedding plane failure;oil based mud is more positive for long-term wellbore stability than water based mud. The results can provide a reference for drilling in gas shale.
闫传梁,邓金根,蔚宝华,谭 强,邓福成,朱海燕,胡连波,陈子剑. 页岩气储层井壁坍塌压力研究[J]. 岩石力学与工程学报, 2013, 32(8): 1595-1602.
YAN Chuanliang,DENG Jingen,YU Baohua,TAN Qiang,DENG Fucheng,. RESEARCH ON COLLAPSING PRESSURE OF GAS SHALE. , 2013, 32(8): 1595-1602.
U. S. Energy Information Administration. Shale gas in the United States:recent developments and outlook[OL]. http://www. Eia. Gov/ reports,2012.
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