Syntactic foam has been used successfully for over thirty years in the offshore industry, primarily as a buoyancy material for supporting marine riser pipe, and in floats and buoys of various kinds. Now its use is growing as a thermal insulating material for subsea equipment and pipelines, ensuring continued flow of hydrocarbons under adverse conditions. Experience to date shows that syntactic foam can in many cases offer significant engineering and economic advantages compared to more conventional insulation. However, realizing the full benefit of these new materials requires careful selection of ingredients and optimization of all relevant properties using a systems approach to the manufacture, assembly, and installation of the equipment. Introduction Syntactic foam is a composite material made from tiny hollow glass microspheres embedded in a polymeric binder, as shown in Figure 1. In some cases other fillers are added as required to modify the composite properties. High compressive strength and low density are the properties that make syntactic foam an efficient buoyancy material, and low thermal conductivity is a byproduct of its construction. Given its thermal efficiency and water resistance, syntactic foam is a natural choice for insulating subsea equipment. However, syntactics for thermal insulation are designed differently than are materials intended solely for buoyancy purposes. Density of the material is of less interest, while long-term thermal stability becomes critical. As long as service is limited to cold water, a wide range of polymer binders is available, and the spherical fillers are strongly reinforced by the surrounding matrix. At elevated temperature, on the other hand, materials choices are limited and the strength of the composite may be affected in ways that are difficult to predict. Such are the challenges that are continuing to shape the development of syntactic foam insulation. History and Applications It has long been known that subsea production of hydrocarbons is prone to blockage by paraffins or hydrates that can form when the fluid temperature falls below some critical level. One aim of flow assurance technology, therefore, is to conserve the heat of the fluid and prevent excessive cooling, even during shutdown periods. This has become an increasingly important concern as production has moved into deeper water and longer flowlines have been required, and a variety of different insulation methods have evolved. The following components have received attention to date: Wet trees and valves are routinely insulated. Key issues include high temperature, differential thermal expansion and contraction, and the necessity of some parts to move or to be serviced or replaced while in service. Jumpers are also frequently insulated. These pipes are often of complex curvature and usually require insulation materials with a great deal of flexibility. Speed and ease of installation is an important objective. Sleds and PLEM's often require not only thermal insulation, but also buoyancy to aid in installing the subsea system. Syntactic foam can be designed to combine the buoyancy and insulation functions. See Figure 2 for a typical PLEM application.
This paper addresses a major challenge facing deepwater production of oil and gas: how to assure continuous flow of product under the pressures and temperatures found on the ocean floor. Syntactic foam promises to overcome the limitations exhibited by conventional insulation materials in the past. New hybrid glass and polymer chemistries with improved “hot, wet” performance survive in conditions that were formerly thought impossible. This paper presents the latest laboratory test data on these new materials, and proposes models for predicting long-term performance.
Epoxy syntactic foam, a composite material combining glass microspheres with other fillers in an epoxy binder, has been used with increasing success in insulating offshore pipelines and subsea equipment for the past decade or more. The advantages of epoxy include excellent resistance to high temperature and high pressure sea water as well as good thermal insulting properties. The exceptional strength of epoxy has made service at great depth possible. However, the rigidity of conventional epoxy-based material has so far limited its application to subsea equipment and J-Lay or S-Lay pipelines. As the offshore industry moves into deeper water and larger fields, the desirability of making advanced epoxy insulation flexible and extending its use to more efficient reeled deployment methods is becoming obvious. This paper describes research directed toward identifying new, highly flexible insulating materials suitable for service up to 300°F (150°C) and as deep as 10,000 ft (3000m). A critical part of the research program has been to develop a methodology for testing affording confidence for very long periods of service. Preliminary test data are presented, along with predictions of how this new class of products will be further developed.
This paper describes a recently developed syntactic foam material designed to collapse under precisely defined conditions of temperature and pressure to protect ultra-deep high pressure offshore oil and gas wells. Each grade of syntactic foam is engineered to have a specific set of characteristics, tailored for the region of the well it occupies. In the startup phase, the materials remain intact, with no significant volume change. As pressure and temperature in the well rise during operations, the materials begin to compress and relieve pressure in the narrow, confined space of the annulus. Finally, when conditions reach preset limits, the syntactic foam undergoes a sudden and dramatic collapse, preventing excessive overpressure, and protecting the steel casing. An important advantage of this material is that it is passive, requiring no controls or active intervention. It responds automatically to protect the well casing from overpressures and temperature spikes. The properties of the material can be adjusted to suit a wide range of conditions inside a given well, or from one well to another.
Syntactic foam, a composite material made by combining spherical fillers in a polymeric binder, has been used for over thirty years in the offshore oil industry. To date, the applications of this material have fallen into two categories: (1) buoyancy modules or floats to support drilling risers, or (2) thermal insulation for subsea equipment and flowlines. In the first category, the syntactic foam is exposed only to cold water (4° C). In the second category, the insulation may be subjected to temperatures as high as 150° C. The contrast of these two separate applications has led to two distinct classes of materials, each with its own properties and accepted standards and criteria. Now a new category of usage has arisen: Vertical production risers that require buoyant lift, and sometimes some degree of thermal insulation, for long-term service (20–25 years) in “warm” water that may be in the range of 40° C to 65° C. By combining the buoyancy requirement of lowest possible density with the insulation requirement of prolonged hydrothermal stability, this application poses new challenges for syntactic foam development and demands new directions in testing and analysis. Because of the increasingly large size of emerging offshore projects, the potential requirement here is for very large volumes. This paper describes the materials that have been identified as candidates for the new service, and outlines the testing philosophy that is being evolved to test and qualify them with confidence for very long periods of service. Preliminary test data is presented, along with predictions of long-term performance. Lessons learned during the project will have implications for all syntactic materials, and will be useful to any managers and technologists involved in marine engineering.
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