Study On The Influence Of Weight On Bit And Torque Measurement Under Non-uniform Temperature Field

The development of complex Wells such as deep and ultra-deep Wells makes the drilling move towards deep burial,high temperature and high pressure,which leads to increased safety risks and frequent accidents in the drilling process.The near-bit measuring tool can measure engineering parameters such as weight on bit and torque near the bit,identify complex conditions during drilling,and reduce drilling risks.Therefore,the accuracy of measuring parameters of the near-bit measuring tool is very high.However,during the drilling process,there is a temperature difference between the fluid temperature in the drill string and the annulus fluid,resulting in uneven distribution of the temperature field inside the near-bit measuring tool,which affects the accuracy of weight on bit and torque measurement.At present,the influence of non-uniform temperature field inside near-bit measuring tool on weight on bit and torque measurement remains unclear.Therefore,it is particularly important to explore the influence of non-uniform temperature field in near-bit measuring tools on weight on bit and torque measurement.In this paper,the scheme of weight on bit and torque measurement for near-bit measuring tools is determined,and the mechanical characteristics of strain chamber are studied.The mathematical model of wellbore temperature field was established and solved discretely by finite difference method.The distribution law of fluid temperature in drilling string and annulus fluid was analyzed under different parameters.The three-dimensional heat transfer model of the near-bit measuring tool is established by fluent,and the non-uniform temperature field distribution inside the measuring tool is studied.The influence of non-uniform temperature field on weight on bit and torque measurement was investigated.It is found that the non-uniform temperature field has a maximum error of 22.88% in the measurement of weight on bit,but has no effect on the measurement error of torque.The relationship between the temperature difference between the inside and outside wall of the near-bit measuring tool and the measurement error of weight on bit is fitted out.Based on this relationship,a correction method for the influence of non-uniform temperature field on weight on bit measurement is proposed.The following studies were carried out :(1)The force of the near-bit measuring tool is analyzed,and the measurement scheme of weight on bit and torque is determined.The finite element model of the near-bit measuring tool was established.The sensitivity of the side wall and the bottom surface of the strain chamber and the sensitivity of the strain chamber under circular,elliptical and square shapes were analyzed.The strain gauge sticking position and strain chamber shape were determined.(2)According to the principle of heat transfer,considering the Joule-Thomson effect caused by the water hole of the drill bit,the temperature field model of the drilling wellbore is established.The finite difference method is used to solve the discrete problem.After verifying the accuracy of the model,the temperature distribution of the fluid in the drill string,the drill string,the annulus fluid,the casing cement ring and the formation in the drilling wellbore is obtained;The influence of parameters on wellbore temperature field was analyzed,and the influence of specific heat capacity of drilling fluid,density of drilling fluid,circulation flow rate,inlet temperature,circulation time and well depth on the temperature of fluid in drill string and annulus fluid was studied.The temperature difference between fluid in drill string and annulus fluid was determined under different parameter conditions.(3)Based on fluent,a three-dimensional heat transfer model of the near-bit measuring tool was established,and the distribution of non-uniform temperature field inside the measuring tool and the temperature difference between the inside and outside walls of the measuring tool were calculated under different installation positions of the near-bit measuring tool and different working parameters.Based on this,the strain composition at the place where the strain gauge is pasted is analyzed,and the influence of non-uniform temperature field on weight on bit and torque measurement is calculated through the thermal coupling analysis of the near-bit measuring tool,and the influence law of the temperature difference between the inside and outside walls of the measuring tool on weight on bit and torque measurement is obtained.On this basis,a method to correct the measurement errors of weight on bit and torque of measuring tools by non-uniform temperature field is proposed.