| At present,the oil and gas reserves in our country are decreasing day by day.If we want to develop more oil and gas resources,we need to drill deeper strata.In general drilling operations,ordinary PDC bits are used for drilling,but PDC bits are usually suitable for hard formations in deep wells.In actual drilling operations,problems such as drilling jam and rock breaking are often encountered.These problems will reduce the bit drilling rate and wellbore quality,and seriously affect the bit service life.By using foreign drilling technology for reference and studying the characteristics of underground rock formation,it is shown that the percussive rotary drilling technology can effectively improve the drilling rate of PDC bit and prevent drilling jam.The occurrence of accidents such as well deviations.Compared with the impact drilling technology abroad,the research of hydraulic impact drilling technology in China started relatively late.Although many domestic production units and research institutes have done a lot of research on hydraulic impactors and achieved good results,the developed hydraulic impactors have never been able to meet the needs of production.There will be many problems in practical application.Therefore,a new type of hydraulic impactor is designed according to the requirement of actual drilling operation.The diameter of the hydraulic impactor is Φ 172 mm and the drilling fluid flow rate is controlled between20-40 mm.L / S,a new type of hydraulic impactor is studied by theoretical calculation and computer simulation.The specific research work in this paper is as follows:This paper introduces the application of hydraulic impactor in conventional drilling of PDC bit.The whole structure design of the new type hydraulic impactor is completed,the working principle of the hydraulic impactor is explained,and three problems encountered in the design are put forward.These problems are: drilling fluid shunt problem,The problem of drilling fluid purification and the buffer problem of preventing the piston rod from bumping up.The working process of the designed hydraulic impactor is explained in detail according to the process state diagram.It is concluded that a motion period of the hydraulic impactor consists of four states and the whole structure of the hydraulic impactor is verified to be reasonable at the same time.In order to drive the piston rod of the hydraulic impactor to impact the anvil,it is required that the drilling fluid produce high pressure area and low pressure zone in the chamber of the hydraulic impactor,and in the design process of the hydraulic impactor,The throttle port is used to adjust the working flow and pressure difference of themoving impingement assembly,and the working flow rate of the piston cavity is estimated according to the requirement of rock burst.Then two design schemes of throttle of hydraulic impactor are put forward.The first one is to determine the flow rate of drilling fluid of hydraulic impactor is 30 L / s,and then change the size of throttle.The flow rate until the throttle can meet the impact frequency requirements of the hydraulic impactor;The second is to determine the reasonable diameter of the throttle port and the piston cavity,change the total flow rate of the drilling fluid through the hydraulic impactor,and carry on the simulation analysis of the passage.The pressure drop curves of drilling fluid passing through the throttle or piston cavity are drawn respectively.Through continuous trial and contrast,it is determined that under the total flow rate of a certain drilling fluid,the flow rate of the piston cavity reaches the impact frequency requirement.The simulation results show that the size can meet the requirements.Using solidworks 3D modeling software to model the motion impact component,using ADAMS kinematics analysis simulation software to carry on the collision simulation analysis to the motion impact component of the hydraulic impactor,choosing the Impac function model to establish the constraint to the model.By simulating the whole process of impact hammer on anvil seat,the curve of impact force change during the impact of moving impact components on anvil seat is obtained.According to the curve,the maximum impact force and impact time can be obtained.Then the model is imported into the ansys static analysis module,and the strength of the moving impact component is checked,and the maximum impact force is applied to the impact hammer.The stress distribution and displacement of the whole moving impact assembly are given to verify that the moving impact assembly can meet the intensity requirements.According to the parameters of hydraulic impactor,the single tooth rock breaking model of PDC bit is established,and the physical parameters of cutting tooth and rock model are defined.The rock breaking situation of drilling without hydraulic impactor and hydraulic impactor is simulated respectively,and the stress distribution and displacement of PDC bit when breaking rock are compared.Finally,it is concluded that using hydraulic impactor to assist rock breakage can effectively improve rock breakage efficiency.The main results of the paper are as follows:The motion and impact function of hydraulic impactor is realized,and the scheme of driving impact hammer body with piston rod by drilling fluid is adopted.At the same time,it is determined that five kinds of throttle sleeve with different sizes are suitablefor different drilling fluid flow conditions,and the impact power of the designed hydraulic impactor is about 392 J and the impact frequency is controlled at 30 Hz by theoretical calculation.ADAMS dynamic simulation software is used to simulate the impact of moving impact components,and the curve of impact force change in the whole process of impact anvil of impact hammer is obtained.The maximum impact force is 2.97 × 10 ~5N and the impact time is 15 Ms.According to the maximum impact force applied to the impact hammer contact surface,it is obtained that the maximum stress occurs on the contact surface when the impact hammer hits the anvil seat.The stress value is 314.27 MPA,which meets the strength requirement of the moving impact component material.According to the obtained parameters of hydraulic impactor,the single tooth rock breaking model of PDC bit is established,which simulates the drilling rock breaking situation after the hydraulic impactor and hydraulic impactor are not used,respectively.By comparing the stress distribution and displacement of PDC bit during rock crushing,it is concluded that the designed hydraulic impactor can effectively improve the rock breakage efficiency.Through the research and analysis of the hydraulic impactor in this paper,the function and internal structure principle of the hydraulic impactor are further understood.In the process of structure design,it is more persuasive to adopt two design schemes of throttle port size.The structure of hydraulic impactor designed by combining theoretical calculation with computer simulation is analyzed whether it is reasonable or not.The dynamic simulation software is used to verify whether the impact power of hydraulic impactor meets the requirement of auxiliary rock breaking.Finally,the rock breaking effect of bit is compared under the two conditions of hydraulic impactor being used or not.It is verified that the designed hydraulic impactor can meet the requirement of auxiliary rock breaking. |
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