Research Of The Ultra-high Strength Sucker Rods String Optimization Design Method

The sucker rods of ultra-high strength have Ultra-high tensile strength and fatigue strength,suitable for heavy,overweight loads,non-corrosive or slightly corrosive wells.In recent years,its application in major oil fields becomes more and more widely.But there are still issues such as unclear use boundary or low use efficiency in practice,it needs to be further improved.Tensile test for ultra-high strength sucker rod is carried out,which is consists of three groups of grade HY and grade HL sucker rod,to obtain yield and tensile strength.Through the fatigue test of sucker rod specimen,the P-S-N curve has been obtained,then the rod fatigue limit has been calculated.Through the load analysis of sucker rod in directional well,clear up the load calculation step up and down stroke in the axial load.For the research of design method,Firstly,on the basis of rod tensile and fatigue tests' parameters,API method has been improved,and the formula of sucker rod of ultra-high strength allowable stress has been got;Using system efficiency as a optimizing target,the?·A·?????? method and the modified API method have been used for designing the three directional wells' sucker rods combination,through comparative analysis to obtain a more suitable method of the sucker rod of ultra-high strength---the modified API method.Using grade D and ultra-high strength rod in the same well.Change the rod combination and swabbing parameter to obtain the combination of rod string and corresponding objective function EI,and contrast and analysis to obtain the minimum depth of the ultra-high strength sucker rod to replace the grade D rod;meanwhile,using the ?·A·?????? method to calculate the maximum pump depth directly of single-stage sucker rod,which provides some reference for the field application of the ultra-high strength sucker rod string.