高速牙轮钻头螺旋组合密封机理研究

Seal is a technical problem of high-speed roller bit, which is to be resolved urgently, the abrasive slurry is a key factor that affects the seal life, because the sealing mechanism is not clear so far, there is not a set of effective design and criteria to guide the sealing application. Based on a idea of "sand discharging", a spiral combination seal of a high speed roller bit is proposed in this project, breaking the previous idea of passive sand discharging, which is expected to resolve the problem. First, the structural parameters will be designed; Second, the theoretical simulation studies will be carried out by establishing a liquid-solid two-phase flow model to study the influence of mud sand amount, the key parameters of a spiral structure, a high speed and the matching relation between the key structure parameters and a high speed on the mechanism of the sand discharging and the sealing, and the influence of the O-ring key structural parameters on the pressure distribution in stationary state; Third, the experimental studies will be carried out to test sand discharging amount, the amount of wear, seal life and mechanical properties, combining with simulation, the influence of each factors on the mechanism of the sand discharging and the seal will be to studied deeply, theoretical models will be to revised or refined; Finally, a new sealing mechanism will be revealed, the structural parameters will be determined, the matching relation between the structural parameters and the high speed will be established, a quantitative calculation method and model of O-ring pressure distribution will be established, a evaluation system of a new sealing performance will be established, and the study method and mean of a new sealing will be established to provide the theoretical support for engineering applications.

密封是高速牙轮钻头急需解决的技术难题，泥浆磨粒的进入是影响密封寿命的关键因素，因密封机理至今不明确，导致没有一套行之有效的设计和使用准则来指导密封的应用。本项目提出基于“排砂”思路的高速牙轮钻头螺旋组合密封，突破以往被动防砂思路，可望解决该问题。首先，设计结构参数；其次，开展理论仿真研究，建立液固二相流计算模型，研究泥浆含砂量、螺旋结构关键参数、高速度、结构关键参数与高速度匹配关系对排砂及组合密封机理的影响规律，研究钻头停转时O型密封圈关键结构参数对压力分布的影响规律；然后，开展试验研究，测试排砂量、磨损量、密封寿命、力学性能等，结合仿真，深入研究各因素对排砂及密封机理的影响规律，修正或完善理论模型；最后，揭示新型密封机理，确定结构参数，建立结构参数与高速度匹配关系，建立定量计算O型密封圈压力变化的方法和模型，建立新型密封性能评价体系，建立新密封的研究方法与手段，为其工程应用提供理论支撑。

（1）通过开展高速牙轮钻头螺旋密封排砂机理的流场仿真研究及结构设计，得出：岩屑颗粒在螺旋泵送作用下，可以排出密封腔，验证了螺旋排砂性能的可行性；随着螺距、倾角的增加，排砂性能先增大再减小；随着螺旋圈数和转速的增大，排砂性能增强，但应根据实际工况适当提高转速；泥浆含砂量越大，密封性能越差；转速对密封性能的影响远小于螺旋结构参数的影响，可忽略不计；各螺旋结构参数之间没有相互影响，其影响规律与单一因素对螺旋密封性能的影响规律一致；初步设计了新密封结构参数：螺距1.6mm、密封间隙0.5mm、斜螺面倾角23°，O型圈内径45mm、外径52.1mm、截面直径3.55mm，压缩率12.67%。.（2）通过开展高速牙轮钻头组合密封机理的仿真研究，得出：随着螺距、密封间隙、倾角的增加，O型圈的密封性能逐渐降低；随着转速的增加，O型圈的密封性能逐渐增加，但应根据实际工况适当提高转速。.（3）通过开展钻头停转时接触力学仿真研究，得出：O型圈的应力、接触压力分布均对称，接触面两端的压力小，中间大，最大应力和接触压力都大于压差，能够保证可靠密封。.（4）开展新型密封机理的试验研究，采用水平式高速牙轮钻头轴承螺旋密封试验装置，利用泵送时间法和泵送重量法来评价排砂性能。仿真与试验结果对比表明，螺旋密封能够起到排砂作用；当转速为300r/min、螺距为2mm、倾角为23°时，密封间隙为0.5mm时，排砂效果较好。.（5）通过开展现场试验研究，得出：8 1/2 SLM537G-1新密封钻头在台架试验中寿命达到14小时，12 1/4 SLM517GK-1新密封钻头在实际钻井试验中寿命达到20小时。.本项目研究成果为揭示新密封机理，指导其应用提供理论基础。