Dynamic characteristics analysis and parameter optimization of rotary steering bottom-hole assembly

The rotary steering bottom-hole assembly (RSBHA) plays an important role in drilling. Less attention has been paid on the stability of RSBHA but more on the steering function. A dynamic model for RSBHA was established to prevent the severe vibration and failure, and the finite element method was used to calculate the dynamic characteristics. Dynamic displacements and bending stress were calculated under the conditions of different structure, different rotary speed and different weight on bit. The results showed that installing a stabilizer at an appropriate location can effectively reduce lateral displacement and dynamic bending stress of the RSBHA. Furthermore, rotary speed had a great effect on the dynamic bending stress: RSBHA with given structure reached its lowest stress level at 100 r/min and its maximum stress level at 180 r/min. If the RABHA structure was appropriate, lateral displacement of the RSBHA changed a little when the weight on bit increased, and dynamic bending stress distribution of the RSBHA seemed reasonable.