封井后提放钻杆过程中球形防喷器胶芯力学行为*

球形防喷器封井后强行起下钻作业极易导致胶芯密封失效，为研究动密封过程中防喷器胶芯失效机制，基于橡胶大变形理论建立球形防喷器动态密封数值模型，探究球形防喷器胶芯在封井和起下钻过程的应力分布和失效模式。结果表明：球形防喷器密封钻杆后，胶芯内壁会产生条状褶皱，支撑筋下板块拐角处产生鼓点状应力分布，颈部和背部存在应力集中现象；当钻杆倾斜时，钻杆与胶芯接触密封区也发生倾斜，胶芯左右两侧应力小幅增大；起下钻过程中，胶芯内壁的条状应力集中变为片状分布，钻杆接头进出密封区域时，接触应力发生突变。

Mechanical Behavior of Rubber Core of Spherical Blowout Preventer During Lifting and Releasing Drill Pipe after Well Sealing

The rubber core seal failure of the spherical blowout preventer(BOP) is very likely to occur during forced tripping operations.In order to study the failure mechanism of the spherical rubber core in the process of dynamic sealing,the numerical model of dynamic seal of spherical BOP was established based on the theory of large deformation of rubber.The stress distribution and failure mode of spherical BOP core during sealing and tripping were studied. The results show that in the process of sealing drill pipe,the inner wall of rubber core will produce strip fold,and a high stress distribution in the shape of a transverse drum is produced at the corner of the plate under the support bar, and there is stress concentration in the neck and back of the support bar.In the process of sealing inclined drill pipe,the sealing area on the drill pipe is inclined,and the stress value on the left and right sides of the rubber core increases slightly.In the process of tripping,the strip-type stress concentration zone in the inner wall of the rubber core changes to the oval stress concentration zone.When the drill pipe joint enters and exits the sealed area,the contact stress will change abruptly.