In-situ observation of particles invasion behavior into the sealing interface under vibration.

• Particles invasion can make downhole sealing failure occur more easily. • In-situ observation method was designed to study the particles invasion process. • Particles invasion into the FKM sealing interface under vibration was observed. • Changes in sealing boundaries and particles position due to vibration. • Frequency of vibration affected the ease of particles invasion behavior. The invasion behavior of particles in the drilling fluid under vibration conditions may lead to sealing failure more easily. A test rig was designed to simulate the operating condition of FKM O-rings under vibration and particles environment. In-situ observations of particles invasion behavior were also performed. The results showed that two behavior of sealing boundaries movement and particles displacement would lead jointly to particles invasion into the sealing interface. It was also shown that both behaviors were induced by vibration and that their salience was influenced by the effect frequency of vibration. A new method to study this problem was proposed. [ABSTRACT FROM AUTHOR]