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The main manifestation of the broken drive shaft is that there is no footage suddenly during drilling or the length is suddenly lengthened during drilling.
The main measures to prevent such accidents: comprehensively consider factors such as the wellbore trajectory, the strata used and the structure of the drilling tool, and selectively adopt the compound drilling method. It is generally not suitable for compound drilling if the degree is greater than 1.5°, and the rotation speed of the turntable is generally lower than 70r/ min;
Reasonable control of WOB to achieve uniform feeding of drilling, prevent the occurrence of drilling slippage, avoid the sudden increase and decrease of WOB, resulting in frequent braking of screw drilling tools, rapid pressure fluctuations, and breakage of the drive shaft, especially when the drilling speed is extremely fast It is easy to occur when a sudden dissection occurs;
When tripping, the speed of lowering should be controlled to prevent sudden jamming and damage to the drive shaft; when compound drilling, the rotating speed of the turntable should comply with the requirements of the instruction manual.
The main measures to prevent such accidents: the drilling team should improve the performance of the drilling fluid when using the screw drilling tools, reduce the sand content as much as possible, and prevent the bypass valve from being stuck between the valve core and the valve seat and cannot be closed;
The ground test should be done before the screw drilling tool is drilled, and records should be made. The technician can accurately calculate the circulating pump pressure when the screw drilling tool is drilled to the bottom, and provide a basis for the operator to accurately judge whether the bypass valve is closed.
If the pump pressure is low after turning on the pump because the bypass valve is not closed, the pump should be stopped and restarted, and the bypass valve can be closed after repeated several times;
When drilling, strengthen the observation of drilling time and lithology to judge whether the drilling is normal. If the lithology does not change and the drilling time is suddenly prolonged, either the drive shaft is broken or the bypass valve is punctured.
The main control measures are that the drilling team adjusts the performance of the drilling fluid, strictly controls the sand content and lowering speed, reduces the time of pump downtime during drilling, and meets the requirements of rock-carrying, so as to prevent the occurrence of such accidents.
Main preventive measures: urge manufacturers to attach great importance to using good rubber and adhesives, improve the glue hanging process, improve the quality of glue hanging, and strengthen quality inspection, so as to improve the quality of products;
Adjust the performance of the drilling fluid, strictly control the sand content, and reduce the wear on the stator rubber; use the specified displacement and weight-on-bit and other parameters to drill to reduce the damage to the motor of the drilling tool;
Use a good mixer and other degassing equipment to make the mud pump disperse water well, and it is strictly forbidden to contain gas in the drilling fluid, because cavitation can accelerate the damage to the stator rubber;
Ventilate the drilling tool before entering the well to prevent foreign matter in the water hole; finally, select the appropriate normal temperature or high temperature screw drilling tool according to the bottom hole temperature being drilled.
At present, the screw drilling tool is an irreplaceable tool for drilling directional wells, horizontal wells and other special process wells in China. By optimizing the use conditions of the screw drilling tool, it is ensured that it is used correctly and properly.
By accurately judging the downhole situation and taking decisive measures in time, the occurrence of downhole accidents of screw drilling tools can be minimized, thereby reducing failure and prolonging service life.
