Composite Materials: An Enabling Material for Offshore Piping Systems
Authors: Martin Rod 
Published: May 2013

This paper discusses the recent advances in composite materials to meet the future challenges of producing oil and gas in deepwater and remote areas. Key to this is the reliable long term use of these materials in potentially degrading environments. The paper discusses screening tests for material suitability for a new range of fiber reinforced thermoplastics and then describes longer term research ongoing to develop test and analytical methodologies to determine the long term life of these materials. Key to this technology is the development of new test methods to identify changes in material properties that can be included in a ply-by-ply analysis of the composite material rather than treating them as a monolithic, homogenious material.

Introduction

In 2007 a technology gap review of composites in the UK oil and gas industry [1] was published that listed a number of existing and potential uses of composites and their barriers to growth in the oil and gas industry. In the five years since that review was published, composite materials have seen a significant growth in awareness of the opportunities they offer as an enabling material to help the industry meet some of the security of energy supply challenges ahead. This enablement is due to these materials being lighter, stiffer (in the fiber direction), stronger and more corrosion resistant than carbon steel. However, the willingness of the industry to accept components fabricated from composite materials is directly related to the operational risks for that component. As a result, composite materials have still only made progress in the lower risk components - but that appears to be changing.

The new horizons for oil production are often termed as reserves that are " hard to reach?? and include ultra-deep water, ultra-deep wells, arctic conditions, highly sour reservoirs, or as " unconventional oil?? such as shale, bitumen and tar sands. Many operators produce from high pressure high temperature (HPHT) reservoirs and some anticipate having to develop technology to exploit fields where extreme conditions (XHPHT) exist. While the numerical definition of HPHT is debatable, operators are anticipating working with downhole temperatures in excess of 200?C and pressures well in excess of 138MPa (20,000psi) where steel wall thickness would begin to become economically unviable. The use of supercritical gases such as CO2 and H2S for enhanced oil recovery is also increasing. Such developments place greater demands on materials (both metallic and non-metallic) in terms of their ability to withstand the operating conditions, but composite materials represent a potential solution to operating under many of them. However, the implementation of composite materials and, more importantly, their qualification for long term performance, represents an opportunity and a technology gap that must be quickly addressed.

One of the biggest opportunities in the very near future is deep and ultra-deep water offshore tubulars. A mere 2% of prospective resources have been explored in deep and ultra-deep waters and 40% of future oil supply will come from water depths of 1500m to 3000m. The use of composite materials will remove substantial weight from the tubulars rising from the seabed to the production system on the surface. This in turn will reduce the topside counter balancing weight and buoyancy requirements, allowing current handling capacities of rigs and derricks, installation vessels and floating production systems to be used. The weight density of steel is 8 in air and for composites is approximately 2. However in water, the densities are reduced to 7 for steel and 1 for composites. Thus composites offer a seven-fold weight reduction which reduces the capacity of handling equipment or allows larger parts when using composites.