Experimental Research on Bit Side Force and Anti-deviation in Vertical Well

Based on dimensional method, the similarity criterion of simulation test was derived. The experimental apparatus was established in accordance with the similarity criterion. A series of experiments with different drilling parameter were carried out. The experimental results show that with rotary speed rise, the bit side force fluctuation increased, however, the vibration energy at the dominant frequency decreased, at low rotary speed, the dominant frequency of the bit side force is equal to rotation frequency of drill string, and at high rotary speed, the dominant frequency is consistent with the backward whirl frequency of drill string, which is about 3 times of rotation frequency, moreover, as WOB rise, the vibration energy at dominant frequency increased, while the total wave energy decreased, and the critical rotary speed value at the jump process of the dominant frequency increased. Furthermore, for the purpose of deviation controlled straight drilling, there is the problem of optimization grouping between WOB and rotary speed.

Well deflection is a crucial indicator to evaluate the hole quality in drilling, and bit side force is a key parameter judging the inclination control effect in the technique of inclination control. Therefore, many of scientists and engineers in the field of drilling have done the massive theoretical research work for bit side force and have established a number of mathematics calculation models. The certain result obtained from the theoretical researches was applied for field,1-4 however it is inaccurate to analyse side force at bit only through the theoretical analysis. With the development of downhole logging while drilling technology and indoor measurement technology, some progress is made on the research of bit side force by analysing down-hole measured field data and conducting laboratory simulation experiments. In order to measure the bit side force during drilling,5,6 Millheim7 , Maron8 and others designed a short section of the test structure which can measure the axial force, bending moment and shear force for derivation of the bit side force. However, the high cost of measurements and the complex working conditions on site are resulting in the incomplete measured data. So in this paper, the laboratory simulation test has become an important mean to research the bit side force. To establish lab simulation test device, this paper derived the simulation test of similarity criterion by using dimensional analysis method. According to the principle of similitude, an experimental device for investigating the bit side force was designed and set up. And a series of experiments with different drilling parameter was carried out to study the influencing factor on the bit side force during vertical rotary drilling.  

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