Integrated Approach to Subsea Integrity Management: Benefits of Early Field Integrity Management Planning for Chevron's Tahiti Field
Authors: Quinn Ronan , Kavanagh Kieran , Power Jeffrey , Thompson Hugh 
Published: October 2008

This paper describes the benefits of an integrated approach to integrity management (IM) planning for a deepwater asset, whereby early integrity management planning is performed across all subsea systems, including the hull, risers, moorings, pipelines and subsea equipment. An example is given whereby the integrated approach to IM has been applied to early field planning for Chevron's Tahiti field in Green Canyon block 596/640 in the Gulf of Mexico.

The field is being developed with a truss spar, polyester mooring, SCRs and steel flowlines producing from two drill centers. Design and IM challenges include the riser and flowline design for HPHT, design of polyester mooring and provision for sour service. The Tahiti plan identified monitoring, inspection, analysis/testing and procedures necessary for maintaining the integrity of risers, flowlines, subsea equipment, hull and mooring. These were combined with the vessel and mooring inspection required by the MMS and Coast Guard to minimize expensive vessel mobilizations and ROV time.

The goal of the IM program, which involves extensive structural and environmental monitoring combined with a comprehensive hull and subsea inspection program, is to verify key design and response uncertainties early in field life and demonstrate continued fitness for purpose throughout the life of field.

The process involved in defining an outline IM plan for the subsea system has been performed in consultation with key stakeholders of the system. This identified synergies in the planning and scheduling of IM activities and achieved significant cost benefit through optimized mobilizations.

Introduction

Effective integrity management planning allows the operator of an offshore floating production development to reduce uncertainties associated with the design or response of subsea and floating systems and improve understanding of in-service response, thereby managing and controlling the risks associated with deepwater hydrocarbon production.

This paper presents an innovative approach to the development of a preliminary subsea integrity management plan (IMP) and associated costs for a full field development, including hull, moorings, risers, flowlines and subsea equipment.

A case study is presented whereby this approach has been applied to the early IM planning for Chevron's Tahiti field in the Gulf of Mexico. The plan defines the proposed IM strategies for each of the field sub-systems and puts these in the context of the US federal regulations underlying them.

General Integrity Management Process

The process for implementing an IM plan for a field system is illustrated in the flowchart of Figure 3, taken from the draft update of API RP2RD [5]. This illustrates how a risk assessment is performed on system-specific failure modes defined through a typical Hazard Identification (HAZID) process.

This risk assessment may be fully quantitative, if statistical data is available, or alternatively it may assign risk ratings to failure modes based on an assessment of probability and consequence of failure. The IM strategy is then typically conceived based on the level of risk assigned to key failure modes of the system. The final IM program for a field is then typically defined as a series of activities that may typically be subdivided into four functional areas: