ABSTRACT
Coiled tubing (CT) has been widely used for oil and gas exploitation, however corrosion of CT under high pressure and high temperature (HPHT) environment was often reported, also corrosion induced failures of CT welds were often observed to occur during service. Corrosion related behaviors of CT welds are not clear. Therefore, a study of the corrosion resistance of CT welds under HPHT environment is carried out. In order to efficiently evaluate the corrosion resistance of welds, some test samples were obtained by linear cutting out of a CT110 in service on the site. The water samples from gas field were used as the test reagent to simulate the actual corrosive medium. Based on the results of weight loss test under HPHT corrosive environment and tensile test under room conditions, the corrosion sensitivities of the welding seam and base material under various temperatures and partial pressures of CO2 as well as the mechanical properties of the corroded CT were compared and evaluated quantitatively, the corrosion morphologies and material products of the test samples were analyzed by scanning electron microscope (SEM). The test results showed that the corrosion rates of the welding seam in a HPHT caldron were 1.7, 2.0 and 1.2 times of the base metal's when the total pressure is 4MPa, and the temperature is 30°C, 60°C and 90°C, respectively. The corrosion rates of the welding seam is 2.0, 2.1 and 2.0 times of the base metal's when the partial pressure of CO2 is 0.1MPa, 0.2MPa and 0.3MPa, respectively. The yield strength of the weld seam after corrosion test was found to be reduced by 4.8% (the yield strength of the base metal was reduced by 4.0%) and its tensile strength was reduced by 8.2% (the base metal was reduced by 7.1%). This indicates that CT weld seam is more susceptible to corrosion than CT base material under service condition.
Subject(s)
Corrosion , Metals/chemistry , Carbon Dioxide/chemistry , Hot Temperature , Metallurgy , Microscopy, Electron, Scanning , Oil and Gas Fields , Pressure , Surface Properties , Tensile Strength , WeldingABSTRACT
Aim To investigate the effect of curcumin on radiosensitivity of radioresistant nasopharyngeal carcinoma cell line CNE-2R and its mechanism.Methods The concentration of curcumin was screened by MTT assay.Dose-survival curves were obtained according to the colony forming test for L-Q matching and multitarget-single hitting matching,while SF2 and the correlation parameters of radiation biology were calculated.The changes of cell cycle in CNE-2R cells caused by curcumin were also tested by flow cytometry(FCM).The differential expression of genes related to cell cycle and DNA damage repair were detected by RT-qPCR.Results CNE-2R cells could not be inhibited by 10 μmol·L-1 curcumin.Dealt with 10 μmol·L-1 curcumin for 24 h,the value of α/β increased to 1 596 from 6.56;the value of SF2 decreased to 0.361 Gy from 1.93 Gy;the value of N decreased to 1.06 from 1.60;the value of D0 decreased to 2.12 from 3.27;the value of Dq decreased to 0.12 from 1.53.FCM showed that the cells in G2 phase had a significant increase and the cells in S phase had a significant decrease after dealt with 10 μmol·L-1 curcumin for 24 h.The expression of CDK4 was significantly up-regulated and GADD45g,BRCA1 were significantly down-regulated.Conclusion Curcumin radiosensitizes nasopharyngeal carcinoma cell line CNE-2R by changing cell cycle and affecting DNA damage repair through regulating the expression of CDK4,GADD45 g and BRCA1.
