Development of Leak Resistance in Industry Standard OCTG Connections using Finite Element Analysis and Full Scale Testing

摘要

The original American Petroleum Institute (API) tubularrnspecifications were established in the early 20th century withrnthe intent to standardize pipe sizes and connections so thatrnmaterial from one mill/user could be assembled with materialrnfrom other sources. The original API specifications forrnthreaded connections did not focus specifically on ensuringrnleak resistance-only interchangeability. Today, thernimportance of connection integrity and reliable leak resistancernis more widely recognized. Casing and tubing stringsrnrepresent the primary environmental and safety barrier(s) forrnoil and gas containment. The threaded connections for thesernstrings are one of the performance-limiting and most criticalrnfeatures for the tubular product.rnTo address the leak resistance issue, an API work grouprnconsisting of user and manufacturer representatives developedrna performance-based connection specification for LTC (Long,rnThreaded and Coupled)1 connections for casing and tubing.rnThese new specifications are currently being finalized as arnSupplemental Requirement to API Specification 5CT, SR22.rnDevelopment of these supplemental specifications employedrnFinite Element Analysis (FEA), full scale physical testing,rnand evaluations of product specifications, inspection andrngaging methods, process control, makeup and threadrncompound. The objective of this API initiative is to minimizerncostly failures, increase performance, improve delivery andrndecrease inventory, and minimize supplier and user life cyclerncost by developing an engineered connection as an industryrnstandard. API Supplemental Requirement (SR) 22rnspecifications enable manufacturers to supply a reliable fieldreadyrnproduct with the performance users require.