Structural Design And Mechanical Analysis Of Test String In High Pressure And High Yield Gas Well

With the exploration and development of natural gas,the testing of gas reservoir is developing towards high pressure and high yield.At present,the commonly used test string is facing the problems of high test pressure and test output,which often leads to the failure of gas well test or inaccurate data.Therefore,it is necessary to design a kind of test string for high pressure and high production according to the characteristics of current gas wells.At the same time,due to the changes of string structure and test technology,the existing string mechanics theory and analysis method can not accurately reflect the stress of test string in high pressure and high production gas wells,so it is necessary to establish a set of mechanical model and analysis method for high pressure and high production test string.Firstly,according to the testing characteristics of gas wells,the main problems faced in the testing of high-pressure and high-yield gas wells are analyzed.According to the design principles and methods of the testing string,the high-pressure and high-yield testing string is designed,and the composition of the testing tools is analyzed.Finally,the testing tools are optimized according to the testing conditions.Secondly,compared with the surface manifold,the stress and deformation of the test string from the bottom into the wellbore is difficult to monitor in real time.It is necessary to calculate indirectly the pressure,temperature and flow of the well head.However,these parameters are different from the wellhead.Therefore,the time and space of the wellbore production,pressure and temperature are established considering the heat transfer from the flow body to the formation in the wellbore The equations are calculated by Newton Raphson method,and compared with the measured values,and the feasibility of the method is verified.Thirdly,the force of the string in the test process is analyzed,which is mainly divided into temperature,fluid and other forces.The effect of temperature is mainly reflected in the temperature effect;the effect of fluid is mainly reflected in the expansion effect,piston effect and fluid viscous force;the effect of other forces is mainly reflected in the gravity,buoyancy,buckling effect,friction and bending force The influence of force and effect on string.Then,the string is divided into three parts,and the axial force of each part is calculated;at the same time,the axial deformation of the string is calculated for different working conditions,and then the strength checking calculation formula of the test string is given.Finally,the model of the test string is established by using the finite element software.Through the test method,the influence of the string under the buckling effect,temperature effect and expansion effect is simulated.The error is less than 3%compared with the theoretical value of the string.It is proved that it is feasible to determine the equivalent stress and axial deformation of the string by the finite element method.Then,the equivalent stress and axial displacement of the string are calculated respectively by the finite element model,which can guarantee the safe use of the test string.Then,the factors that affect the strength of the test string are analyzed by using the finite element software,which provides a reference for the standard use of the test string.