Research On The Working Mechanism Of Anti-slugging Tools For Reducing Stick-slip And Constant Torque

At present,the exploration of oil and gas has entered a bottleneck,and the development of conventional oil and gas fields are gradually entering the late,causing the global oil and gas development gradually from shallow to deep,ultra-deep,from land to the ocean and other unconventional storage layer.To obtain energy from these unconventional energy reservoirs,it is necessary to drill out of the ultra-deep and curved wellbore trajectories.For drilling more slender and deeper wells,a few thousand meters of drill string is required to transmit axial forces and torques to break the rock.However,the slender drillstrings allow the drilling system to be susceptible to self-excited vibrations that may cause drill string twist,drill bit beating and sticky slip phenomenon.Wherein,when the drill bit encounters a hard formation and a soft and hard interlaced formation,when the drill bit encounters a hard formation,the force acting on the drill bit is insufficient to break the rock,which resulting the rotational speed of the drill bit will gradually decrease or cease.while the top drive system on the ground is still driving the drill string system,the system will generate torsion stick slip vibration.In order to solve this problem,this paper proposes an anti-stick drill tool with the function of reducing stick-slip and holding torture,and the following researches are carried out from the aspects of structural design,kinematics and dynamic characteristics of the tool,and the sticking characteristics of the drill bit when the tool is used in the drilling:Firstly,the working principle of the anti-stick drill tool is introduced,and the structure of the tool is designed.According to the function of the tool,the strength check and other related mechanical analysis are carried out for the two key parts of the disc spring and the helical transmission.Through the establishment of the theory models of kinematics and dynamics for helical transmission part,the axial and circumferential motion characteristics of the outer helical core shaft of the tool under different anti-torque are analyzed.By adopting ADAMS to simulat the kinematics and dynamics,and the simulation results are consistent with the theoretical analysis results.Then,the drill string models with and without the Anti-stick drill tool are respectively established.By comparing the characteristics that the drill bit axial and circumferential motion,the change of the torque and weight on bit during in the normal operation stage,the stick-slip stage,the slipping stage,to analyze the function of reducing the stick-slip vibration and holding the torque of the bit with the anti-stick tool.The results show that the drill bit has a stagnation phenomenon in the stick-slip stage,and the fluctuation range of bit rotation speed and torque are large.While the anti-stick tool is used,the drill bit is moved up and down to move away from the stick-slip area.And the drill bit has no stagnation and the torque fluctuation of the drill bit is small.Finally,based on the drill string model with anti-stick tool,the movement characteristics of the drill bit are analyzed by changing the length of the drill string,the input rotate speed of the drill string on the top and the initial compression size of the disc spring system.It is found that the increase of the length of the drill string reduces the stability of the drill bit and the increase of the maximum axial stroke of bit.The increase of the initial compression size of the anti-stick tool disc spring system decreases the maximum axial stroke of the drill bit,while the change in rotational speed has little effect on the movement characteristics of the drill bit.Based on the structure and principle of the anti-stick tool,this paper establishes the kinematics and dynamics analysis model of the tool.According to the drillstring models with the anti-stick tool,the influence of the anti-stick tool on the stick-slip characteristic of drill bit is obtained,which provides a theoretical basis for the research and application of anti-stick tool in future.