The fractured drill pipe was investigated by means of non-destructive testing, chemical composition analysis, optical microscope, material property testing machine and SEM with EDS. The results showed that fracture of drill pipe body was hydrogen sulfide stress corrosion cracking. High strength, high hardness, and stress corrosion sensitivity of the drill pipe material were important reasons leading to failure.
The buttress thread connection was used in deep well or ultra-deep well widely because of its high joint efficiency. Pullout failure scarcely happen on buttress premium thread connection with great joint strength and good sealing property. Direct evidences about connection dropout couldn’t get in most cases by reason of casing string had fallen into well or casing string had been concreted in formation by cement. Now the difficulty of analysis on pullout is higher and higher. A buttress premium thread casing joint had pulled out at mill end of coupling in a straight well and dropout casing string couldn’t get out of the well. Research on this pullout case was carried out combining relative theories with tests. Macroscopic analysis and dimension measurement were done for dropout coupling. The material’s physical and chemical properties were checked. Thread inspection and full-scale tests were done for two casing simples that are same lot with pullout. Metallograph analysis was carried out on load flank and guide flank in box thread of pullout coupling and same lot new coupling. The results showed that dropout failure was ascribe to inadequate make-up torque at mill end of pullout coupling and complex downhole condition and improper handling in the oil field. On the other hand joint’s strength decline on the effect of unsuitable heat treatment to coupling and greatly uneven black crested pin thread around circumference. The pertinence measures were laid down at the end of this passage.
A new drill pipe steel microalloyed with 0.04 w.t.% Nb was designed to meet the needs of drilling operation in super-deep wells, and the precipitation behavior of Nb during temper was studied in detail. The results show the austenitic grain can be refined by the addition of 0.04 w.t.% Nb, and the steel has a high yield strength of 1192MPa, high tensile strength of 1226MPa and high impact absorbing energy of 137J when the steel is quenched at 900°C and tempered at 550°C, moreover, the volume fraction and dimension of precipitates increases with increasing temper temperature. When the new steel is tempered at 550°C, the new steel has the best comprehensive performance due to the fine dispersed precipitates. The mechanical properties of the new steel are much better than that of the common drill pipe steel.
This paper studies properties of concrete under the action of water-reducing retarder and expansive agent; gives the optimal design calculation method of cooling water pipe in the construction technology: mainly considering pipe’s diameter, distance, cooling water’s flow, temperature, time etc; studies the optimization to the concretes construction method. Midas/Civil, one finite element analysis soft-ware, analyses mass concrete construction of the whole process of the temperature field and stress field in the numerical simulation, considering the admixtures and construction technology. The results show that commonuse of admixtures and reasonable construction technology are the important means of controlling cracks.
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