中文摘要：

为了提高钻井作业的安全性,保证井底发生溢流后能迅速可靠封隔环空、方便后续压井作业,设计了一种安装在近钻头端的井下防喷器,对其结构和工作原理进行了详细介绍.通过建立井下防喷器中推块机构的受力模型,分析了推块对管柱的反作用力与推块锥面角和碟簧变形量之间的关系.对花键进行了强度校核,使用有限元软件对不同厚度和硬度的胶筒的封隔能力进行了分析,同时进行了井下防喷器的室内实验.研究结果表明：当单个碟簧的变形量为0.2mm、推块的锥面角度为45°时,单个推块可对钻柱产生2.2kN的反作用力,设计值和实验数据接近;当钻柱扭矩达到45 000N·m,花键的挤压应力仍在许用应力范围内;在压缩量和封隔间隙相同的情况下,胶筒的宽度越宽、硬度越大,封隔能力越强,且胶筒硬度越大,需要的下压力也越大.研究结果对井下防喷器的设计具有一定指导作用.

英文摘要：

In order to improve the safety of drilling, ensure annulus can be quickly and reliablysealed and provide convenience for well-killing operations,a kind of downhole blow-out preventernear the bit was designed, whose structure and working principle were introduced in detail. Byestablishing the force model of push block mechanism in downhole blow-out preventer, he relationshipbetween reacting force of push block to column with cone angle of push block and deformationamount of disc spring was analyzed. The strength of spline was checked. The rubbersleeves with different thickness and hardness were analyzed based on the finite element software.Meanwhile the indoor experiments of downhole blow-out preventer were carried out. Research resultsshowed that when deformation amount of single disc spring was 0. 2 mm and cone angle is 45°, reacting force of push block to column produced by single disc spring was 2. 2 kN which wasclose to experimental value; when torque of drill string reached to 45 000 N·m , extrusion stressof spline was in the range of allowable stress. In the same compression and seal clearance, the widerwidth and the bigger the hardness of the rubber was, sealing ability was stronger. When the greater hardness of the rubber was , more pressure was needed to compress rubber. The researchingachievement has certain significance for the design of downhole blow-out preventer.