Research And Experimental Analysis Of Working Mechanism Of Hydraulic Oscillator

With the gradual exhaustion of oil and gas resources in shallow layers, at the same time the demand for oil and gas resources is increasing with fast development of economic, the oil engineering turns to the drilling direction of deep well, horizontal well and extended reach well. However, compared with vertical wells, it will produce more technical difficulties during the drilling process of horizontal and large displacement wells, in which the large frictional resistance is a dominating problem in exploration and development of horizontal and extended reach wells. As a new vibration and friction reducing tool, the hydraulic oscillator has remarkable application advantages. But the research upon it is limited at home and abroad. This paper focuses on the mechanical and friction reducing properties of hydraulic oscillator, verifies its properties with experiment, it will produce great significance for the development of this tool. The main research contents of this paper are followings:Firstly, the structural characteristics and working principle of hydraulic oscillator are introduced in detail. According to the structure characteristics of the tool, the basic calculation of the motor is carried and the motion characteristics of the motor and valve plate systems are analyzed. Furthermore, the motion analysis models of the motor and valve plate system are built. From the numerical example, it can be seen that the motion of the motor and valve plate system have periodic law and the movement frequency of the valve plate system is related to the input flow rate, the flow area between the static and dynamic valve plates increases with the increase of static valve hole diameter.On the basis of the kinematics, the characteristics of work pressure drop and water hammer of hydraulic oscillator are analyzed. And the calculation model of hydraulic oscillator under axial impact force and vibration model under experimental conditions are established. Moreover, combined with the structural parameters of hydraulic oscillator, the numerical examples of the work pressure drop, water hammer pressure, axial impact force and vibration displacement are obtained respectively. At a certain of flow rate, the smaller the diameter of the static valve hole is, the larger the pressure drop is, together with the water hammer pressure, total axial force and vibration displacement.By the tool bench test, the frequency, pressure drop, vibration impact force, shock and vibration displacement of the tool were tested. Compared with the test results and the theoretical results, theoretical results were in accord with test results well, it can verify the correction of theoretical calculation.Through establishing the axial vibration analysis model of hydraulic oscillator in the horizontal well, the axial vibration friction-reducing mechanism is analyzed. Combined with the numerical parameters, the vibration friction-reducing effects of the two different important parameters-the diameter of static valve hole and the mounting positions of the hydraulic oscillator are analyzed. From the analysis results, it can be seen that the smaller the diameter of static valve hole is or the closer the distance between the mounting position and the drill bit is, the greater the vibration friction-reducing effect is. During practical drilling, both the tool pressure drop and the effect of vibration on the MWD tool need to be considered to choose the right installation location and the diameter of static valve hole.In summary, based on the structure and working principle of the hydraulic oscillator, the motion analysis model and mechanical analysis model are established and the models are verified by the field experiments. Furthermore, the vibration friction-reducing characteristics of the hydraulic oscillator in down hole are analyzed. The paper can provide theoretical basis for tool selection and corresponding optimizing drilling process in the future site application of hydraulic oscillator.