CAJ | 학술논문

近年来,气体钻井在国内外的应用越来越广泛,其机械钻速高于钻井液钻井,气体钻井提高机械钻速的机理有待进一步研究.本文在弹性力学、热弹性理论的基础上建立气体钻井井底岩石物理模型,考虑温度和初始地应力对井底岩石应力场的影响,采用有限元软件对井底温度场和应力场进行数值模拟.结果表明,井底钻头前方待破碎岩石存在一个低应力区域,考虑温度后的低应力区域大于不考虑温度的低应力区;不考虑温度情况下井底、井壁局部岩石受拉应力作用,考虑温度情况下井底、井壁岩石均受到拉应力作用;由于拉应力的作用降低了钻头破岩难度,有利于提高机械钻速;温度对井底应力状态的影响是显著的,在井底应力场研究中应作为一个不可忽略的因素.
근년래,기체찬정재국내외적응용월래월엄범,기궤계찬속고우찬정액찬정,기체찬정제고궤계찬속적궤리유대진일보연구.본문재탄성역학、열탄성이론적기출상건립기체찬정정저암석물리모형,고필온도화초시지응력대정저암석응력장적영향,채용유한원연건대정저온도장화응력장진행수치모의.결과표명,정저찬두전방대파쇄암석존재일개저응력구역,고필온도후적저응력구역대우불고필온도적저응력구;불고필온도정황하정저、정벽국부암석수랍응력작용,고필온도정황하정저、정벽암석균수도랍응력작용;유우랍응력적작용강저료찬두파암난도,유리우제고궤계찬속;온도대정저응력상태적영향시현저적,재정저응력장연구중응작위일개불가홀략적인소.
In recent years, gas drilling is applied wider and wider at home and abroad, and its rate of penetration is higher than that of mud drilling;However, the mechanism to improve rate of penetration for gas drilling needs to be further studied. In this paper, the downhole rock physics model of gas drilling is established based on the theory of elastic mechanics and thermal elasticity theory; bottom hole temperature and stress field are simulated numerically with the software considering impact of the temperature and initial ground stress on bottom hole rock stress field. The result shows that there is a low stress area at the ready-to-break rock, which is bigger when the temperature is considered than when it isn’t. when temperature is ignored,the bottom hole rock and local rock at the sidewall are subject to tensile stress;and when temperature is considered,both the bottom hole rock and the wall rock are subject to tensile stress temperature effect after the bottom and sidewall rock are subject to tensile stress effect. Difficulty of rock breaking is reduced under the effect of tensile stress, which helps to improve the rate of penetration. Impact of temperature on bottom hole stress state is significant and it should not be ignored in studying bottom hole stress field.