Abstract

In the coming years several existing offshore platforms in Indonesia will be required to be recertified due to (a) having exceeded the design life and (b) change in the original certified condition. Most of these will continue to be operational, hence re-certification will become mandatory due to Migas regulations. These platforms will pose a real risk to life and environment. Further they will be operating without proper insurance coverage.

For re-certification, these platforms need to satisfy a re-assessment procedure. The structural integrity studies form an integral part of such assessments. In most cases the traditional "elastic" methods will be inadequate for the structural integrity studies of existing platforms. Currently it is widely recognized that if an existing structure does not meet the "elastic design" criteria it does not mean that the structure is inadequate or unserviceable. In recent years the need to go beyond the elastic limits for such analysis has been accepted. A number of research projects and studies have emerged to address this problem. Of these the most important document was the American Petroleum Association (API RP2A-WSD sect 17.0) draft code. This code recommends the use of Full Plastic Collapse Analysis (FPCA) also known as "push over" analysis for the strength integrity studies of the existing platforms.

Though this technique has been known for a number of years, universally very few platforms have been reassessed using the FPCA method. This method was adopted two years ago by YPF Maxus Southeast Sumatra Inc (MAXUS) on the structural integrity assessments of a number of existing platforms. Resources required to carry out such studies are currently available in Indonesia.

The objective of this paper is to describe the FPCA method, and the methodology that is adopted for such assessments. The paper will also present case studies from MAXUS project, and will conclude by interpreting the results obtained.