The behavior of enclosed-type connection of drill pipes during percussive drilling

A Shadrina,L Saruev

doi:10.1088/1755-1315/27/1/012057

Abstract

Percussion drilling is the efficient method to drill small holes (≥ 70 mm) in medium- hard and harder rocks. The existing types of drill strings for geological explorations are not intended for strain wave energy transfer. The description of the improved design of the drill string having enclosed-type nipple connections is given in this paper presents. This nipple connection is designed to be used in drilling small exploration wells with formation sampling. Experimental findings prove the effectiveness of the enclosed nipple connection in relation to the load distribution in operation. The paper presents research results of the connection behavior under quasistatic loading (compression-tension). Loop diagrams are constructed and analyzed in force-displacement coordinates. Research results are obtained for shear stresses occurred in the nipple connection. A mechanism of shear stress distribution is described for the wave strain propagation over the connecting element. It is shown that in the course of operation the drill pipe tightening reduces the shear stress three times.

Highlights

During the percussive drilling, the pipe connection is exposed to the axial load, impacts produced by percussive mechanisms, and coupling torque [1]
The analysis of the curves shown in figure 4, shows the deformation properties of the nipple thread connection
A mechanism of deformation of the enclosed-type nipple connection during the quasistatic loading is given in the table below

Summary

Introduction

The pipe connection is exposed to the axial load, impacts produced by percussive mechanisms, and coupling torque [1]. The study of the nature of these loads, their estimation and consideration in the drill string design allow improving the durability of thread connections. Such types of connections as pipe-in-pipe, coupling, coupling-and-tool refer to inefficient design methods of the percussive drilling because cyclic tensile stresses and a low rate of power pulse propagation are observed. The loop diagram obtained on the oscilloscope display was photoed. The coupling torque of the drill string was obtained using the weight lever and ranged from 49 to 245 Nm. Pulses obtained on the oscilloscope display were photoed. The obtained data were processed using the mathematical statistics techniques

Results and discussion

III-IV IV–V Interval V–I V–VI

Conclusions