| Gas drilling technology is one of the indispensable mainstream technologies in the field of oil and gas drilling in China,the drilling string vibration and well slope problem of gas drilling is a classic problem that is common in gas drilling engineering but has not been solved well,and now it has become an important factor restricting the development of gas drilling,the sharp vibration of the drilling string will cause the failure of the drilling string,and the well slope will cause the borehole trajectory to be difficult to control,both of which will cause serious drilling accidents,seriously affect the efficiency of drilling work and even bring major economic losses.From the perspective of drilling safety and efficiency,it is particularly important to study the vibration and anti-slope characteristics of gas drilling columns.In this paper,the lateral vibration with the greatest hazard from gas drilling is analyzed,and in order to obtain the accurate natural frequency of lateral vibration,the lateral vibration mode characteristics of the whole well drill string and the bottom drilling tool are compared and analyzed,and then the whole well drill string that is more in line with the actual situation is determined as the research object.The working drill string is subject to stress rigidification caused by axial force at all times,so the prestress mode analysis,prestress harmonic response analysis,and prestress transient dynamic analysis are carried out on the whole well drill string.The results show that when the axial force is tensile,it will increase the natural frequency of lateral vibration of the drill string,and when the axial force is pressure,it will reduce the natural frequency of the lateral vibration of the drill string;when the drilling pressure is 50 k N,the speed of the drill string is between 0 and 90 r/min,there is a resonance weak area of 0.4 to 0.6Hz(corresponding to 24 to 36 r/min),and the larger the drilling pressure,the lower the frequency of the weak resonance area;after the collision between the drill string and the well wall,the stress rigidification effect will lead to an increase in vibration energy at the neutral point but a decrease in amplitude.Since the lateral vibration will lead to the change of the well slope in the drilling,the relationship between the lateral vibration and the anti-oblique straightening of the double stabilizer pendulum drilling tool in the oblique straight well is studied,the interaction between the bottom drilling tool and the well wall is introduced,a dynamic well slope model of the double stabilizer pendulum drilling tool is established,and the buckling,collision,lateral vibration and anti-oblique characteristics of the double stabilizer pendulum drill tool are studied.The study found that the buckling form of the drilling tool was bent from the sinusoidal bending → the spiral bending with the increase of drilling pressure,and the greater the degree of buckling,the more contact points with the well wall,which in turn affected the anti-oblique characteristics of the pendulum drilling tool;the order of collision between each part of the double pendulum pendulum drill tool and the well wall was in descending stabilizer → the upper stabilizer → the first drill collar → the second stage of drilling collar;the lateral vibration trajectory of the drilling collar of each part was mostly concentrated on the downhole wall of the inclined well,and fluctuated in a more fixed area;when the drilling pressure was given,the buckling form of the drilling string did not change much.However,intermittent collisions between the stabilizer and the well wall still occur;the dynamic anti-slope force under the lateral vibration shows a sinusoidal trend,the drilling pressure has little influence on the dynamic lateral force,and the amplitude of the well inclination force and the azimuth force reach the maximum value at the frequency of 3.2 Hz.In order to study the influence of the lower boundary condition on the lateral vibration of the bottom drill tool and the trajectory of the drill bit,the dynamic boundary condition of the drill bit in real time was introduced,the coupling dynamic model of the drill string-drill bit-rock was established,and the motion trajectory of the PDC drill bit and the hybrid drill bit when breaking the rock was studied,as well as the difference between the lateral vibration of the bottom drill tool,the influence of dynamic stress,and the lateral vibration of the bottom drill tool under different drill pressure and rotation speed under the hybrid drill bit system.The results show that the trajectory of the hybrid drill bit is offset along the lower left,the trajectory of the PDC drill bit is offset along the upper left,and the offset distance and angle of the mixed drill bit are very small,and the drilling posture is more stable;the lateral vibration speed of the bottom drill tool in the PDC drill bit system is greater than that of the hybrid drill bit system,the vibration is more intense,and the trajectory direction of the near drill drill string section center is similar to the trajectory direction of the drill center of the drill bit;the larger the drill pressure in the hybrid drill bit system,the more intense the lateral vibration of the bottom drill tool;when the drill pressure is 150 k N,the intermediate speed is 180 r/ The lateral vibration of the bottom drill tool is more intense than at 120r/min and at 240 r/min.The results of this paper are helpful to systematically understand the lateral vibration and anti-oblique characteristics of the gas drilling system,and provide a theoretical basis for effectively preventing resonance,understanding the relationship between the lateral vibration characteristics of the double pendulum drilling tool and the anti-oblique straightening,and providing a reference for avoiding the lateral vibration failure of the drilling tool and the directional operation technology of the hybrid drill bit. |
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