Determination of Formation Collapse Pressure of Bonan Shale Taking into Account Tri-axial Stresses
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摘要: 渤南区块罗家地区沙三储层以泥页岩为主,泥页岩厚度大、分布广,有机碳含量高,富含油气。但是该组地层微裂缝发育,岩石强度各向异性明显,加上水化作用影响,水平井钻井过程中井壁稳定问题突出,使用传统坍塌压力预测模型不能有效计算泥页岩储层的坍塌压力,普通考虑弱面的分析模型通常忽略了中间主应力对岩石强度的影响,预测结果也不如意。在对罗家地区泥页岩矿物成分和微裂缝分布情况分析的基础上,基于弱面强度理论,综合考虑三向应力的影响,建立了更精确的坍塌压力预测模型。实例分析表明,对于该区域的泥页岩钻井,一味地增大钻井液密度并不能保证井壁稳定,该区块岩石碳酸盐矿物含量较多,原始强度较高,且地层孔隙度低,如果使用控压钻井,使井底压力略低于地层压力,可增加岩石强度,增大井壁稳定性,并降低钻井成本,增加钻速。Abstract: The lithology of the Shasan reservoir formations in Luojia, Block Bonan is mainly shales that are thick and widely spread. The shales are rich in organic carbon and oil and gas. Borehole instability has been encountered during horizontal drilling because of the developed fractures in those formations, the anisotropy of the formations, and the hydration of the formation rocks. Conventional models prognosing the collapse pressure of the formations cannot be used to calculate the collapse pressure. Those models that only consider the weak planes have no thought for the effect of intermediate principal stress on the strengths of rocks, and the prognoses are generally not done satisfactorily. Mineral composition and fracture distribution have been examined about the shale samples taken from Luojia, and based on the weak plane strength theory, a more accurate prognosis model, which takes into account the effects of triaxial stress, has been established for the prediction of collapse pressure. The application of the model shows that for wells penetrated the shale formations, borehole stability cannot be realized through only higher mud weight. Carbonate formations with higher original strengths and low porosity are not uncommon in this area. If managed pressure drilling (MPD) is used with bottom hole pressure slightly lower than formation pressure, the strength of the rocks can be increased, and hence the stability of the borehole wall. This, in turn, will help reduce drilling cost and increase ROP.
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Key words:
- Shale /
- Weak plane /
- Horizontal well /
- Tri-axial stress /
- Collapse pressure /
- Hole stabilization
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[1] AADNOY B S. Modeling of the stability of highly inclined boreholes in anisotropic rock formations[J]. SPE Drilling Engineering,1988,3(3): 259-268 [2] AADNOY B S. Effects of reservoir depletion on borehole stability[J]. Journal of Petroleum Science and Engineering,1991,6(1): 57-61. [3] ONG S H,ROEGIERS J C. Fracture initiation from inclined wellbores in anisotropic formations[J]. Journal of petroleum technology,1996,48(7): 612-619. [4] 金衍,齐自立,陈勉,等. 水平井试油过程裂缝性储层失稳机理[J]. 石油学报,2011,32(2): 295-298.JIN Yan,QI Zili,CHEN mian,et al. A mechanism study on the fractured reservoir instability during well testing of horizontal wells[J]. Acta Petrolei Sinica,2011,32(2): 295-298. [5] 刘向君,叶仲斌,陈一健. 岩石弱面结构对井壁稳定性的影响[J]. 天然气工业,2002,22(2): 41-42.LIU Xiangjun,YE Zhongbin,CHEN Yijian. Influence of rock weak plane texture on sidewall stability[J]. Natural Gas Industry,2002,22(2): 41-42. [6] 袁俊亮,邓金根,蔚宝华,等. 页岩气藏水平井井壁稳定性研究[J]. 天然气工业,2012,32(9): 66-70.YUAN Junliang,DENG Jingen,YU Baohua,et al.Wellbore stability of horizontal wells in shale gas reservoirs[J]. Natural Gas Industry,201,32(9): 66-70. [7] 刘志远,陈勉,金衍,等. 多弱面地层水平井裸眼井壁垮塌量计算模型[J]. 石油勘探与开发,2014,41(1): 102-107.LIU Zhiyuan,CHEN Mian,JIN Yan,et al. Calculation model for bore-hole collapse volume of a horizontal openhole in multiple-weak-plane formation[J]. Petroleum Exploration and Development,2014,41(1): 102-107. [8] JAEGER J C,COOK N G W. 岩石力学基础[M]. 中国科学院工程力学研究所,译. 北京: 科学出版社,1981: 80-84. JAEGER J C,COOK N G W. Fundamentals of rock mechanics[M]. Institute Engineering Mechanics,Chinese Academy of Science,Trams. Beijing:Science Press,1981: 80-84. [9] 陈平,马天寿,夏宏泉. 含多组弱面的页岩水平井坍塌失稳预测模型[J]. 天然气工业,2014,34(12): 87-93.CHEN Ping,MA Tianshou,XIA Hongquan. A collapse pressure prediction model of horizontal shale gas wells with multiple weak planes[J]. Natural Gas lndustry,2014,34(12): 87-93. [10] LEE H,ONG S H,AZEEMUDDIN M,et al. A wellbore stability model for formations with anisotropic rock strengths[J].Journal of Petroleum Science and Engineering,2012,96/97: 109-119. [11] 马天寿,陈平. 层理页岩水平井井周剪切失稳区域预测方法[J]. 石油钻探技术,2014,42(5): 26-36.MA Tianshou,CHEN Ping. Prediction method of shear instability region around the borehole for horizontal wells in bedding shale[J]. Petroleum Drilling Techniques,2014,42(5): 26-36.
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