Wellbore Instability Mechanism of Deep Sidetracking Wells in Mudstone Strata
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摘要: 为了解决西部超深硬脆性泥岩地层侧钻过程中井壁易垮塌的难题,从矿物特征及钻井液作用下地层强度的变化规律出发,确定了井壁失稳原因,考虑了层理面产状、井眼轨迹及地应力的综合影响,根据桑塔木组井壁围岩强度破坏条件建立了造斜井段井壁失稳地质力学模型.利用提出的井壁稳定力学模型分析可得,TKX-CH井侧钻段泥岩造斜初期坍塌压力当量密度为1.22 kg/L,实钻采用钻井液密度1.12 kg/L,井下掉块严重;井斜角达到58°时,将钻井液密度降至1.11 kg/L,井下掉块即得到抑制.现场试验表明,相同井斜角和侧钻方位角条件下,随着差应力比值的增大以及泥岩裸露在钻井液中时间的增长,维持井壁稳定的钻井液密度增大.研究认为,钻井设计时应根据地应力状态优选合理的造斜方位,以有效规避地层井壁围岩坍塌失稳风险高的井段,降低安全钻进风险.Abstract: To solve the wellbore instability problem of a deep sidetracking well in hard-brittle mudstone strata of west China,this paper indicated the mechanism of wellbore instability considering the effects of both minerals and drilling mud on rock compressive strength.Based on failure condition of wellbore,a model of well instability was built considering the contributions of bedding plane occurrence,in-situ stress,and well trajectory,etc.The calculations of this model for the sidetracking mudstone segment in Well TKX-CH showed that the collapse pressure is 1.11 kg/L.Serious rock-collapse happened in practice when drilling mud was 1.12 kg/L.This situation improved as the drilling mud density decreased to 1.1 kg/L,when the deviation angle reached to 58°.When the sidetracking orientation and deviation angle are constant,the density of drilling mud to keep well stable increases as the ratio of stress difference increases and as exposure time of mudstone inside drilling mud increases.Therefore,in order to decrease the risk of borehole instability,in-situ stress,bedding planes and exposure time of mudstone should be considered systematically in drilling design.
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[1] 周伟,耿云鹏,石媛媛.塔河油田超深井侧钻工艺技术探讨[J].钻采工艺,2010,33(4):108-111. Zhou Wei,Geng Yunpeng,Shi Yuanyuan.Discussion on ultra-deep sidetracking technology in Tahe Oilfield[J].Drilling Production Technology,2010,33(4):108-111. [2] 何伟国,唐明,吴柳根.塔河油田深层侧钻水平井膨胀套管钻井完井技术[J].石油钻探技术,2013,41(5):62-66. He Weiguo,Tang Ming,Wu Liugen.Expandable casing drilling and completion technology in deep sidetracked horizontal wells of Tahe Oilfield[J].Petroleum Drilling Techniques,2013,41(5):62-66. [3] 金衍,陈勉.井壁稳定力学[M].北京:科学出版社,2012:1-2. Jin Yan,Chen Mian.Mechanics of wellbore stability[M].Beijing:Science Press,2012:1-2. [4] 金衍,陈勉,陈治喜,等.弱面地层的直井井壁稳定力学模型[J].钻采工艺,1999,22(3):13-14.Jin Yan,Chen Mian,Chen Zhixi,et al.Mechanics model of sidewall stability of straight wells drilled through weakly consolidated formations[J].Drilling Production Technology,1999,22(3):13-14. [5] 黄荣樽,陈勉,邓金根,等.泥页岩井壁稳定力学与化学的耦合研究[J].钻井液与完井液,1995,12(3):15-21,25. Huang Rongzun,Chen Mian,Deng Jingen,et al.Study on shale stability of wellbore by mechanics coupling with chemistry method[J].Drilling Fluid Completion Fluid,1995,12(3): 15-21,25. [6] Aadony B S.Modeling of the stability of highly inclined boreholes in anisotropic rock formations[R].SPE 16526,1998.
[7] 薛世峰,马国顺,葛洪魁,等.液-固-水化耦合形式的井眼稳定性模型研究[J].石油钻探技术,2007,35(1):41-44. Xue Shifeng,Ma Guoshun,Ge Hongku,et al.Study of a fluid-solid-wetting coupling wellbore stability model[J].Petroleum Drilling Techniques,2007,35(1):41-44. [8] 王倩,王刚,蒋宏伟,等.泥页岩井壁稳定耦合研究[J].断块油气田,2012,19(4):517-521. Wang Qian,Wang Gang,Jiang Hongwei,et al.Study on shale wellbore stability coupling[J].Fault-Block Oil and Gas Field,2012,19(4):517-521. [9] Hale A H,Mody F K.Experimental investigation of the influence of chemical potential on wellbore stability[R].IADC/SPE 23885,1992.
[10] Tan C P,Richards G,Rahman S S.Managing physical-chamical wellbore instability in shale with the chemical potential mechanism[R].SPE 36971,1996.
[11] 卢运虎,陈勉,安生.页岩气井脆性页岩井壁裂缝扩展机理[J].石油钻探技术,2012,40(4):13-16. Lu Yunhu,Chen Mian,An Sheng.Brittle shale wellbore fracture propagation mechanism[J].Petroleum Drilling Techniques,2012,40(4):13-16. [12] van Oort Eric,Hale A H,Mody F K,et al.Transport in shales and the design of improved water-based shale drilling fluids[R].SPE 28309,1996.
[13] Chen Guizhong,Chenevert M E,Sharma M M,et al.A study of wellbore stability in shales including poroelastic,chemical,and thermal effects[J].Journal of Petroleum Science and Engineering,2003,38(3/4):167-176.
[14] 卢运虎,陈勉,金衍,等.钻井液浸泡下深部泥岩强度特征试验研究[J].岩石力学与工程学报,2012,31(7):1399-1405. Lu Yunhu,Chen Mian,Jin Yan,et al.Experimental study of strength properties of deep mudstone under drilling fluid soaking[J].Chinese Journal of Rock Mechanics and Engineering,2012,31(7):1399-1405. [15] Lu Yunhu,Chen Mian,Jin Yan.A mechanical model of borehole stability for weak planeformation under porous flow[J].Petroleum Science Technology,2012,30(15):1629-1638.
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