【作者】 孙士慧；

【导师】 闫铁；

【作者基本信息】 东北石油大学 ， 油气井工程， 2011， 硕士

【摘要】 气体钻井在解决低压漏失、提高钻速方面优势而被广泛应用,但井斜控制技术已成为限制气体钻井发展的瓶颈。现场资料表明,气体钻井比常规钻井液钻井更易井斜,井斜程度更大。由于气体钻井循环介质的改变使底部钻具组合的受力和变形发生变化且存在负压差,气体钻井条件下的井斜机理必然不同于常规过平衡钻井条件下的情形。因此,从理论上研究气体钻井的井斜机理、制定防斜措施并指导现场作业显得尤为重要。首先,本文根据实钻资料统计结果,得到气体钻井井斜规律:气体钻井产生的井斜较大且井斜增长速度快,井斜不易控制;总结了影响气体钻井井斜的不可控因素、可控因素。其次,基于气体钻井井底岩石受力状况,分析了破岩机理、井底温度场、地层各向异性、地层倾角等不可控因素对气体钻井井斜机理的影响,分析认为:气体钻井改变了井周井底岩石的应力状态,使得地层应力差值变大,放大了地层各向异性,这是造成气体钻井易井斜,且井斜后难控制的主要原因;气体钻井新的破岩方式是导致井斜不断增加的一个原因;气体钻井条件下地层倾角和性质对井斜的影响更加显著。再次,分析了上返岩屑、井径扩大、钻具组合、钻压、井斜角、地层出水等可控因素对气体钻井井斜的影响,认为:钻井液和岩屑颗粒对井壁的冲蚀、井底应力集中是气体钻井井径扩大的原因,井径扩大造成控制井眼轨迹的难度增加,引起井斜;地层出水会导致岩屑变湿粘结成团,在近钻头附近粘附在下井壁,形成垫层,垫层形成另外的增斜力,导致井斜。最后,从地层造斜力、岩屑垫层、钻具组合三方面对井斜控制进行分析,建议研究使用空气锤技术。更多还原

【Abstract】 In recent years, gas drilling is used widely due to the advantages of high penetration rate and low leakage. But well deviation control has become a bottleneck restraining the development of gas drilling technology. Field data show that well deviation is more serious in gas drilling than conventional drilling. The circulation medium change which results in the change of force and deformation on bottom-hole assembly (BHA) and the existence of negative pressure differential, the mechanism of well deviation in gas drilling is different from conventional drilling. So, theoretically studies on well deviation mechanism, formulate prevent measures become pretty important.First, the rule of well deviation in gas drilling is summarized according to the statistical results of field data, i.e. well deviation is serious and the growth rate is fast, the control is difficult. And the influential factors including uncontrollable factors and controllable factors are analyzed.Second, the effects of uncontrollable factors including rock-breaking mechanism, bottom temperature field, the anisotropy of stratum, formation dip on well deviation are studied based on the stress condition of bottom hole rock in gas drilling. It is indicated that the stress strain field distribution of hole and bottom rock changes which lead to the stress difference is large, the anisotropy is magnified. This is the main reason of gas drilling tend to deviate and the difficult control. New breaking modes for rock are another cause of serious deviation. The effect of formation dip and properties in gas drilling are more remarkable.Third, the effects of controllable factors including cuttings, well bore enlargement, drilling assembly, WOB, deviation angle and water export on well deviation are discussed. Well bore erosion by cutting particles and bottom stress concentration result in well bore enlargement. The difficulty of well trajectory control is increased, thus causes the well deviation. Cushion is formed by cutting bed after formation water out. And it plays a very important role in well deviation.Finally, well deviation control technologies are researched from the aspects of formation deflecting force, cushion and drilling assembly. Air hammer drilling technology is suggested.更多还原