Causes of drill pipe fracture of drilling rig

The main causes of drill pipe fracture are:

1、 The bending moment of drill pipe is too large in the process of reaming and pipe pulling back;

2、 The reasons for the excessive bending moment are as follows: first, the actual curve of the guide hole deviates greatly from the theoretical curve; Second, the hole after reaming is irregular, which makes the pipe form an included angle with the reamer and the drill pipe axis.

Other reasons:

1、 In order to save investment, the directional drilling equipment used by the construction contractor (i.e. Party A) does not match the actual needs of the project construction. The tonnage of the directional drilling equipment is too small, the maintenance is not timely, and the failure rate is high, which makes the directional drilling force uneven. At the same time, the stop and go of the construction makes the hole quality poor, the hole irregular, and the drilling tool is easy to lock, resulting in the fracture of the drill pipe;

2、 The selection of reamer model is unreasonable. Failure to select the matching model according to the actual geological conditions resulted in increased drilling torque, increased drill pipe wear and fracture;

3、 When the rock reamer is used to ream or wash the hole, the drill pipe is not connected at the back, and the reamer swings greatly in the hole, causing the drill pipe and the spindle of the reamer to fracture;

4、 The selection of drill pipes is unreasonable. Due to the failure to track and manage drill pipes and the lack of drill pipe inspection data statistics, the service life of a set of drill pipes used is uneven, and the drill pipes with large wear are broken due to stress concentration;

5、 The deviation control of the guide hole is unreasonable, and the deviation is too large. In the later correction process, due to the unreasonable actual curve, the bending moment borne by the drill pipe is too large, which is easy to cause the drill pipe stress to increase or directly cause the drill pipe surface to break due to excessive friction. In particular, the drill pipe joint bears a high eccentric friction, resulting in a large amount of heat during periodic contact friction with the hole wall, so that the surface material of the joint is subject to periodic heating and cooling, It makes the surface brittle and causes the longitudinal crack of the internal thread of the drill pipe joint under the influence of the excessive bending moment;

6、 The grading of reaming is unreasonable. The construction unit reduces the grading of reaming in order to catch up with the construction period, which greatly increases the drilling torque and is easy to cause the drill pipe to wear and break;

7、 Due to poor geological conditions, broken and collapsed channels and excessive drilling cuttings, the anti lock ability of drilling tools is low and the risk of locking is increased, resulting in drill pipe fracture