The Stress Analysis And Structure Optimization Of The Acid Fracturing String In Ultra-deep Well

It is always happened that the string is inhibited or cannot reach the designate position orloses efficacy during the Ultra-deep well string running down, which seriously affectsdevelopment and utilization of the complex oil-gas well in deep reservoirs. It is an urgentneed to evaluate and analyze the load condition during the string running down in engineeringpractice.Since the ultra-deep well string is long, the well structure is complex, friction resistanceis big, this article takes gravity, friction resistance and buoyancy force into account.Firstly, Ihave grasped the acid fracturing process, the general structure of string and the key parts suchas separation scraper.Secondly,I have derived the formula influenced by changes of thewellbore with the column pressure field and temperature field.Finally,adopted thethree-dimensional model and coordinates follower,by analyzing the load changes in stringrunning,and given the calculation method. By Matlab program, a set of software wascompiled for engineering examples of calculation.Research results about the string multiphaseflow analysisshow:in high temperature and high pressure Wells string mechanicscalculation,internal pressure calculation formula is considered using fluid mechanics relatedformula.Calculation resultsof engineering example show that：While the string running, in thevertical wells and horizontal wells string just stick to wall,the contact force is provided bycomponent weight. But in the intervalnear the deflection point and well deviation Angle andazimuth Angle changing violently, need calculatethe radius of curvature of eachintervalbywell bore trajectory parameters fitting,determine whether strings contactedwith theborehole, according to contact condition calculate the corresponding friction resistance,bending moment, torque and so on.