热力复合作用下PDC钻头动态磨损规律研究

【作者】 张鹏；

【导师】 马亚超； 陈洪亮；

【作者基本信息】 西南石油大学 ， 工程硕士（专业学位）， 2022， 硕士

【摘要】 随着油气资源的不断勘探开发,我国油气资源开发的主战场逐渐向温度高、硬度大的深层和超深层等非常规地层中转变,PDC钻头在钻遇这些地层时,常在环境温度、切削热和载荷的复合作用下破岩,钻头磨损严重,降低了破岩效率和钻头的使用寿命。而目前关于热力复合作用对PDC钻头磨损规律影响的研究较少,不能为高温复杂地层中PDC钻头的设计提供指导。为此,本文以PDC钻头为研究对象,开展了在热力复合作用下PDC钻头的动态磨损规律研究,为改善PDC钻头在高温地层中的钻井性能提供指导。本文的主要研究工作和取得的成果如下:(1)开展了不同环境温度和切削深度下PDC齿破岩仿真研究。分析了 PDC钻头破岩时切削热的产生和传导过程,建立了 PDC齿破岩的有限元仿真模型,得到了在不同环境温度和切削深度下PDC齿破岩过程中齿面的温度场特征和轴向力变化。结果表明,在切削深度为2mm,环境温度从25℃提高至300℃的过程中,PDC齿的最高齿面温度从265℃提升至625℃,平均温度从160℃提升至360℃;在切削深度为3mm时,环境温度从25℃提高至300℃的过程中,PDC齿的最高齿面温度从341℃提升至735℃,平均温度从200℃提升至420℃;在破岩仿真过程中,PDC齿所受平均轴向力最大为3kN;可见环境温度对PDC齿齿体温度的影响较大,进而影响PDC齿的磨损和使用寿命。(2)开展了热力复合作用下PDC齿磨损实验研究。根据PDC齿破岩过程中齿体的温升和所受轴向力特征,采用正交实验方法构建实验方案,并进行热力复合作用下PDC齿的磨损实验,分析了不同温度、轴向力和对磨时间下PDC齿的微观形貌特征和磨损量,构建了 PDC齿磨损模型。结果表明,PDC齿在500℃以上,其表面产生的裂纹数目增多,剥落坑的体积增大,表面析出的氧化物也大量增多;在温度25℃～750℃,轴向力0～1600N,磨损时间10min～40min条件下,温度是影响PDC齿磨损量的主要因素,其次是轴向力,最后是磨损时间。(3)开展了热力复合作用下PDC齿磨损规律研究。首先建立PDC齿切削受力模型和齿体温升模型,结合建立的PDC齿磨损模型,采用零点遍历法,开展了热力复合作用下PDC齿的磨损规律研究。结果表明,在热力复合作用下,前倾角对PDC齿所受轴向力、齿体温度和线磨损率有较大的影响;侧转角对PDC齿的轴向力、温升和磨损速率影响较小;PDC钻头的转速和钻速均对PDC齿的磨损产生较大影响;随着环境温度的增大,PDC齿的齿体温度和磨损速率均呈线性增大。(4)开展了热力复合作用下PDC钻头动态磨损规律研究。根据PDC钻头几何学和坐标转换等基础理论,构建磨损齿空间几何形态的数学模型,采用数值迭代的方法对PDC钻头上相互关联破岩、相互关联受力、相互关联磨损的各个切削齿进行磨损趋势预测,详细分析了热力复合作用下PDC钻头齿的动态磨损规律,并与没有热作用下PDC钻头齿的磨损进行了对比。结果表明,PDC钻头不同部位齿的磨损差异性是逐渐变化的;前倾角和每圈进尺是影响PDC钻头磨损的关键参数;前倾角为12.86°时,具有较好的耐磨性,各切削齿磨损差异性小,钻井进尺更长,具有更高的钻井性能;在钻压允许的极限值内,增大PDC钻头每圈进尺有助于降低PDC钻头的磨损程度;热力复合作用下PDC钻头齿的磨损高度是不考虑热作用下PDC齿磨损高度的两倍,且热力复合作用下PDC钻头磨损最严重的位置是外锥,不考虑热作用下PDC钻头齿磨损最严重的位置是冠部。更多还原

【Abstract】 With the continuous exploration and development of oil and gas resources,the main battlefield of my country’s oil and gas resource development has gradually shifted to unconventional strata such as deep and ultra-deep layers with high temperature and high hardness,When the PDC bit drills into these formations,it often breaks rock under the combined action of ambient temperature,cutting heat and load,and the bit wears seriously,which reduces the rock-breaking efficiency and the service life of the bit.At present,there are few studies on the effect of thermal compound action on the wear law of PDC bits,which cannot provide guidance for the design of PDC bits in high temperature and complex formations.Therefore,this paper takes the PDC bit as the research object,and carries out the research on the dynamic wear law of the PDC bit under the combined effect of heat and force,which provides guidance for improving the drilling performance of the PDC bit in the high temperature formation.The main research work and achievements of this paper are as follows:(1)The simulation research on rock breaking of PDC cutter under different ambient temperatures and cutting depths was carried out.The generation and conduction process of the cutting heat when the PDC bit breaks rock is analyzed,and the finite element simulation model of the PDC tooth breaking rock is established.The temperature field characteristics and axial force changes of the cutter surface during the rock breaking process of the PDC cutter under different ambient temperatures and cutting depths are obtained.The results show that when the depth of cut is 2mm and the ambient temperature increases from 25℃ to 300℃,the maximum tooth surface temperature of PDC teeth increases from 265℃ to 625℃,and the average temperature increases from 160℃ to 360℃;When the depth of cut is 3mm and the ambient temperature is increased from 25℃ to 300℃,the maximum tooth surface temperature of the PDC teeth is increased from 341℃ to 735℃,and the average temperature is increased from 200℃ to 420℃;In the process of rock breaking simulation,the average axial force on the PDC teeth is up to 3KN;It can be seen that the ambient temperature has a great influence on the temperature of the PDC cutter body,which in turn affects the wear and service life of the PDC cutter.(2)The experimental study of PDC cutter wear under the combined effect of thermal and mechanical was carried out.According to the temperature rise and axial force characteristics of the cutter body during the rock breaking process of the PDC cutter,the orthogonal experimental method was used to construct the experimental scheme,and the wear experiment of the PDC cutter under the combined thermal effect was carried out.The micro-morphological characteristics and wear amount of PDC cutter at different temperatures,axial forces and anti-grinding times were analyzed,and the wear model of PDC cutter was constructed.The results show that when the temperature of PDC cutter is above 500℃,the number of cracks on the surface increases,the volume of spalling pits increases,and the oxides precipitated on the surface also increase.Under the conditions of temperature of 25℃～750℃,axial force of 0～1600N,and wear time of 10min～40min,temperature is the main factor affecting the wear amount of PDC cutter,followed by axial force,and finally wear time.(3)The research on the wear law of PDC cutter under the combined thermal and force action was carried out.First,the PDC cutter cutting force model and cutter temperature rise model were established,combined with the established PDC cutter wear model,the zero-point traversal method is used to study the wear law of PDC cutter under the combined thermal and force action.The results show that the rake angle has a great influence on the axial force on the PDC cytter,the temperature of the cutter body and the linear wear rate under the combined thermal and force action;the side rotation angle has little effect on the axial force,temperature rise and wear rate of PDC cutter;the rotation speed and ROP of the PDC bit have a great influence on the wear of the PDC cutter;with the increase of ambient temperature,the body temperature and wear rate of PDC cutter both increase linearly.(4)The research on the dynamic wear law of PDC bit under the combined effect of thermal and force was carried out.According to the basic theories such as PDC bit geometry and coordinate transformation,the mathematical model of the space geometry of the worn cutter is constructed,the numerical iteration method is used to predict the wear trend of each cutter on the PDC bit that is associated with rock breaking,interrelated stress and interrelated wear,the dynamic wear law of PDC bit cutter under combined thermal action is analyzed in detail,and the wear of PDC bit cutter under no thermal action is compared.The results show that the wear difference of the teeth in different parts of the PDC bit changes gradually;the rake angle and footage per circle are the key parameters affecting the wear of PDC bits;when the rake angle is 12.86°,it has good wear resistance,the wear difference of each cutting tooth is small,the drilling footage is longer,and the drilling performance is higher;within the allowable limit of WOB,increasing the footage per circle of the PDC bit helps to reduce the wear level of the PDC bit;the wear height of the PDC bit cutter under the combined thermal action is twice that of the PDC bit without considering the thermal effect,and under the thermal compound,the most severely worn position of the PDC bit is the outer cone,and the most severely worn position of the PDC bit under the thermal action is the crown.更多还原