Development of axial vibration impact device used for screw drill

Axial vibration will occur when a rolling element of thrust bearing rolls on a purpose-built relief track.Based on this property, a kind of axial vibration impact device was developed in this paper.When it is integrated with a screw motor, the technical characteristics of rotary percussion drilling and screw drill + double-table-drive composite drilling are presented.Its thrust bearing is structurally composed of roller, roller bracket and roller track, and this structure divides the whole drilling string into two parts, i.e., axial vibration impact and part and target part.Cam teeth (tooth height 9-17 mm) are distributed uniformly on the upper end face of roller track.When a roller rolls along the ascending surfaces of cam teeth, energy is stored at the vibration impact areas of ascending string.When the roller falls along cam teeth, impact is generated at the contact surface by the vibration impact area of drilling string via a screw output shaft and an impact drive shaft due to the effect of weight on bit and its self-weight, and the spacing between two end faces of shaft is defined as the stroke (4 mm shorter than the height of cam tooth).Based on the basic application conditions of 3 000 m mid-deep wells, the relationships of the impact power and energy storage torque of the device vs.weight on bit and stroke were analyzed by simulating drilling strings with elastic beams, and the ranges of stroke and weight on bit were provided.And accordingly, a prototype was experimentally developed and its impact property was tested.It is shown that when the peak impact is 2.2 times the weight on bit, the service life of this device can reach 80 h in the conditions of weight on bit of 20 kN and pumping rate of 30 L/s.It is indicated that the development of this axial impact device meets the design requirements and preliminarily satisfies the engineering application conditions.