Hibernia GBS Quality Challenges
Authors: Sodha N.A. , Hoff G.C. 
Published: October 2008

The concrete gravity base structure (GBS) for the Hibernia platform was one of the most complex structures of this type ever built. The construction materials and methods used were at the leading edge of concrete technology. In order to complete the construction so that structural integrity and function were achieved in a safe and satisfactory manner, a thorough and comprehensive QNQC Program was required. This paper describes the organization of the project QAIQC organization, qualifications of the personnel, field application of QA and QC Programs, and gives examples of some of the new technical developments used to meet the GBS Construction challenges.

Introduction

The Hibernia Offshore Platform, located in 80m of water 315km east southeast of St. John's, Newfoundland is a complex structure which begins with a barrel-shaped concrete caisson which sits on the sea floor and extends upwards 85m to a roof which is 5m above mean sea level. From the roof, four legs extend another 26m to support a very large topsides equipment (ca. 55,000t operating load). The structure is designed to have a 30-year service life while resisting iceberg impact and the severe wave loading of the North Atlantic. There were many unique design and construction features specific to both the gravity base concrete substructure (GBS) which can store up to 1.3 million barrels of oil and the topsides which used 5 super modules weighing between 5,000 and 8,000t each and 7 smaller Topsides Mounted Structures. Control of all of the design and construction aspects of both the GBS and Topsides were of vital importance and these controls were designed to ensure that the structural integrity and function of the platform were achieved. Quality Assurance (methods of ensuring conformance with specifications) and Quality Control (measurement of physical requirements by inspection, testing and audits) were of prime importance to ensure the interests of the designer, the constructor and the owner.

In Newfoundland, the development of the offshore oil fields began a new chapter in QNQC requirements which had not existed in Canada before. The Hibernia platform was the first to use the regulations (draft) legislated under the Canada-Newfoundland Atlantic Accord Implementation Act (Newfoundland Act). In almost all cases, the project followed Canadian regulations, and when necessary, approvals for deviations were requested from the Canada-Newfoundland Offshore Petroleum Board (C-NOPB).

For Quality Assurance, the Canadian Standards Association (CSA) 2-299 series is required by the Canada Oil and Gas Installation Regulations (COGIR). These requirements were used to the fullest extent possible. Prior to the development of the QNQC plan for the project, quality systems from around the world were examined and compared to CSA Standards. The CSA Standards were found to be more specific and therefore more demanding than most other international standards. They provided for a structured method of addressing quality issues. Some of the experiences using them during the construction of the GBS are described in the following sections.

GBS Construction Challenges

The GBS structure contains 165,000 m3 of pumped concrete having a one-year design strength of 69 MPa.