Analysis of Frequent Failure of Oil Well Tubings Due to Formation of Longitudinal Slit
- PDF / 2,687,555 Bytes
- 9 Pages / 595.276 x 790.866 pts Page_size
- 7 Downloads / 161 Views
CASE HISTORY—PEER-REVIEWED
Analysis of Frequent Failure of Oil Well Tubings Due to Formation of Longitudinal Slit Jeetendra Gupta . Abhay Kujur . Sangeeta R. Prasad . Anita Sharma . Anil Bhardwaj
Submitted: 28 December 2015 / in revised form: 3 April 2016 / Published online: 21 June 2016 ASM International 2016
Abstract In an onshore oil field, many premature tubing failures were observed in wells operating on sucker rod pump. Failures were in the form of longitudinal crack/ vertical slit. During last three to four years, the failure frequency had increased and in one well, new tubing vertically cracked in 8 months only. In the internal surface of the tubing, a longitudinal grooving was observed. The shape of the groove resembled the sucker rod and the crack was along the groove. Observation of grooved region under SEM revealed abrasion features typical of mechanical wear. Small corrosion pits were also observed on some portion of grooved region. As the well was vertical, so chance of contact between tubing and sucker rod was low. But tubing was freely suspended in the well, i.e., there was no tubing anchor which made it vulnerable for the buckling. Analytical studies showed that the failed tubing was in buckling region. On comparison of hardness, it was observed that tubing material was softer than the sucker rod. Buckling of the tubing resulted in rubbing of sucker rod against tubing wall due to which tubing had worn out in the form of groove. Wear-oxidation and oxidation-wear of tubing surface at grooved region and corrosive agents of produced water accelerated this material removal process and when the wall thickness of the tubing at groove region reduced to a point where it was not enough to withstand the hoop stresses, a longitudinal crack formed in the grooved region and tubing failed.
J. Gupta (&) A. Kujur S. R. Prasad A. Sharma A. Bhardwaj Materials & Corrosion Section - Institute of Engineering and Ocean Technology, Oil & Natural Gas Corporation, Navi Mumbai, Maharashtra, India e-mail: [email protected]
123
Keywords Tubing failure Tubing wear against sucker rod Longitudinal crack/vertical slit on tubing Tubing buckling
Introduction Sucker rod pump (SRP) systems are the oldest and most widely used artificial lift technique for oil wells. A sucker rod pumping system is made up of several components, some of which operate above ground and other parts of which operate underground, down in the well. The entire surface system is run by a prime mover, V-belt drives, and a gearbox with a crank mechanism on it. The steel sucker rods are used to connect the down-hole pump inside the tubing with the surface system. Sucker rod couplings are used to connect the sucker rods. Due to movement of the prime mover, the sucker rod reciprocates continuously inside the tubing, and a volume of produced fluid is lifted through the tubing annulus and discharged at the surface. In a such SRP well, communication was found between casing and tubing, and during the initial pull-out, a vertical slit/crack
Data Loading...
