New 97/8-in. HPHT Permanent Packer with New Back-Up System Provides North Sea Operator with Effective Solution for Damaged or Worn Casing

摘要

A major operator in the North Sea had experienced a problem with worn casing at the packer setting depth of an existing HPHT well, causing a leak into the production annulus. A workover was required, and a calliper survey conducted after retrieving the tubing revealed two sizeable grooves along the longitudinal axis of the casing at 120° to each other.This paper discusses the successful qualification and installation of an HPHT permanent packer for worn casing. Permanent packers are qualified by ISO 14310 VO in a test fixture to meet the ISO 11960 internal casing dimensions; however, they do not account for any wear or damage in the casing. A test program was developed to test the packer at HPHT well conditions and in worn casing. The test program consisted of the following: 1. Install the packer in 9-7/8-in casing and flow test to 3 bpm at 180°F to verify that the circulation around the packer did not damage the Aflas? element. 2. Perform an application test using synthetic oil to mimic packer loading until failure, including setting, production, and hot/cold shut in.; apply 9,000 psi annulus pressure to support the casing during testing. In this case, the maximum temperature was 343°F or above for over 200 hours. 3. Perform a modified ISO 14310 VO test at 450°F with 15,000 psi differential pressure and 400,000 lbf tension and compression. The packer passed all tests with no extrusion of the three-piece multi-durometer Aflas? element, and no leaks were detected at any of the load points in the application (liquid) test or modified ISO VO gas test.The discussion will include information on the packer design, HPHT test in worn casing, and casing acceptance criteria. This test was the first packer test performed in worn casing that demonstrated the capability of the compliant back-up systems to support the entire element in worn casing and at HPHT conditions.