Abstract

Oil and Natural Gas Corporation Limited (ONGC) has a significant gas discovery in deep to ultra-deep-water locations at water depths in the range of 2500 to 2800 m in the east coast of India. The eastern offshore field is characterised with deep to ultra-deep-water depths; geo-hazards; harsh environmental conditions with very high current and cyclonic conditions with very large waves; high wax contents; hydrates; geo-hazards and high pressure/high temperature (HP-HT) conditions. Thus; the development of this offshore gas field in water depths more than 2500m and extreme environmental conditions would pose a huge technological challenge to be addressed.

In the paper we discuss the selection of suitable floating structural production concepts and evaluate associated ultra-deep-water riser systems including their technical and commercial aspects. The main objective of this paper is to create a reference document which can help operators of deep-water and ultra-deep waters in the area to take informed decisions related to selection/operation of the types of field development concepts and riser systems for a particular type of floating structure.

Introduction

Objective of paper. This paper is prepared to enable operators of gas fields in deep to ultra-deep waters (more than 2500m depth) to ensure that all aspects of field development challenges are covered in the conceptual design phase of the development so a robust development can be ensured.

Oil and gas developments in India. It is acknowledged that the needs to ensure energy for the population in India has led to exploration for gas in deep and ultra-deep waters. With the use of gas as fuel for electricity plants; there will be a considerable reduction in emission of greenhouse gases (up to 50%) compared with the use of coal and it is suggested that the use of gas will improve the living conditions for those who will get easier access to energy and those who struggle with their health due to pollution from energy generation. As it may not be realistic to generate the amount of renewable energy needed for the huge population of the country in the nearest future; the reduced pollution obtained by burning gas represents a step towards a less polluted environment.

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