Mechanical analysis of support anchor straddle packer test tubular string and its application

Compared with single parker test,support anchor straddle packer test tubular string is more complicated.And,the test tubular string works under more serious conditions and loads.So,support anchor straddle packer test tubular string and down hole tools were often damaged,resulting unsuccessful testing,even disasters.To solve the problem mentioned above and develop regulations to direct support anchor straddle packer testing,considering the disadvantages of present achievements of tubular string mechanics which could only calculate unrestrained tubular strings,separated mini-element analysis method and energy method are used to analyze the buckling behavior of the tubular strings between two parkers and supporting tubing.It is found that the tubular strings with limitable length and restrained by parkers and borehole may buckle into one semi-sinusoidal curve,two semi-sinusoidal curve and helix.Also deduced are the three criterion buckling loads.From buckling analyses of this paper,loads,stresses,strength safety of support anchor straddle packer test tubular string could be analyzed.If the combination of tubular strings is designed,the permissible testing pressure differential could also be calculated.Based on regulations and calculations resulted from this paper,several wells were successfully tested with support anchor straddle packer.