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Dynamic stability of a stepped drillstring conveying drilling fluid

Zhao G.-H., Tang S., Liang Z., Li J.

Journal of Theoretical and Applied Mechanics

2017

Vol. 55 nr 4

1409--1422

Taking into account differences between a drill pipe (DP) and a drill collar (DC), the drillstring in a vertical well is modeled as a stepped pipe conveying a drilling fluid downwards to the bottom inside the string and then upwards to the ground from the annulus. An analytical model that describes lateral vibration of the drillstring and involves the drillstring gravity, weight on bit (WOB), hydrodynamic force and damping force of the drilling fluid is established. By analysis of complex frequencies, the influences of WOB, borehole diameter, DP length, velocity and density of the drilling fluid on the stability of the system are discussed.

Metal Complexes of C-Functionalized Macrocyclic Dioxotetraamines Bearing 8-Hydroxyquinoline Stability in Aqueous Solutions

Su X., Zhu S. -R., Sun W., Zhao G. -H., Chen Y. -T.

Polish Journal of Chemistry

2001

Vol. 75, nr 5

623--632

Two novel 8-hydroxyquinoline connected dioxotetraamines have been designed and synthesized, and have been characterized by elemental analysis, IR, mass spectra and 1H NMR. The two ligands L1 and L2 have two chelating groups. Each can react with a transition metal ion forming complexes. Potentiometric titrations have been performed in 0.1 mol/L NaNO3 at 25_C giving the 1:1 stability constants. Coupled with UV spectroscopy the affinity of 8-hydroxyquinoline and dioxotetraamines to transition metal ions were compared and the possible structure of the metal complex species in solution was discussed. The results show that as to Mn2+, Zn2+ and Co2+, 8-hydroxyquinoline is a stronger chelating reagent than dioxo[13] or [14]tetraamine macrocycles and at 1:1 molar ratio (M:L), the former binds in 100% to the metal ions, while the dioxotetraamines can be only partially or not coordinated.