EVALUACION DE FALLAS DURANTE EL COMPORTAMIENTO DE FATIGA EN TUBERIAS ENROLLABLES USADAS EN POZOS DE PETROLEO

F. DIAZ,; S. HEREÑÚ; J MALARRIA; I. ALVAREZ - ARMAS; A. F. ARMAS; J. PEREZ IPIÑA

San Nicolás, Argentina

Conferencia; 15 CONF DE LAM / 2 CONF SOBRE USOS DEL ACERO DEL IAS, 2004; 2004

QT-800 coiled tubing (CT) is used to perform a wide variety of production and service operations in oil wells.  The material used to manufacture QT-800 CT is a modification of ASTM A-606 Type 4 high strength low alloy (HSLA) steel. The most dominant factors controlling the deformation behavior of CT in the field are the bending/straightening cycles associated  with the spool and gooseneck.  In spite of the fact that strain fluctuations are larger at the outer  surface of the tubing, the primary cracks always nucleate along the inner surface. This is due to the nature of the manufacturing procedure, which tends to produce an inner surface less fatigue resistant than the outer surface. In this study, hardness measurements and transmission electron microscopy (TEM) observations are correlated to evaluate the microstructural metallurgical factors that generate the asymmetry in the fatigue behavior of both surfaces