New 9-7/8-in. HPHT Permanent Packer with New Back-Up System Provides North Sea Operator with an Effective Solution for 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. This problem required a workover, and a calliper survey was conducted after retrieving the tubing. Two large grooves along the longitudinal axis of the casing at 120° to each other were found.Since the worn casing was the problem, a new permanent packer was required, and this paper will discuss the process required to successfully qualify and install an HPHT permanent packer that would satisfactorily address the needs for worn casing.Permanent packers are qualified by ISO 14310 V0 in a test fixture to meet the API 5CT 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 for both HPHT well conditions and 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℉ to verify that the circulation around the packer would 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℉ or above for over 200 hours.3. Perform a modified ISO 14310 V0 test at 450℉ 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 V0 gas test.The discussion will include information on the packer design, HPHT tests in worn casing, and casing acceptance criteria. This test was the first packer test performed in worn casing that demonstrated the capability of a compliant back-up system to support the entire element in worn casing and at the HPHT conditions.