There is increasing demand in the oil and gas industry for higher performance thermal coatings to insulate and protect off-shore transport conduits operating at temperatures from about 150° C. to above about 205° C. In order to maintain the conduit at the required operating temperatures in an undersea environment, the coatings must have high thermal stability to resist the high operating temperatures, and low thermal conductivity to prevent the formation of hydrates and waxes that would compromise pumping efficiency of the fluid in the conduit. The thermal conductivity can be further decreased through foaming the coating to some required degree.
Multi-phase fluid flow is common in subsea fluid transport conduits, such as flowlines and risers. Two main concerns in such systems are the formation of gas-water hydrates and the deposition of wax. Both of these phenomena are related to the temperature of the fluid, and in extreme cases the conduit can become severely constricted or even blocked. This in turn can lead to reduced or lost production. In particularly serious cases this may lead to the need to replace sections of pipeline or entire systems with corresponding loss of asset value. Thermal insulation is used to provide controlled energy loss from the system either in steady state condition or in the case of planned and un-planned stoppage and thereby provide a reliable basis for operation.
For single-pipe flowlines and risers, using bonded external insulation, the mechanical loads as well as the requirements placed on the mechanical and thermal performance of thermal insulation systems normally increase with water depth. Hence, the traditional thermal insulation foam technology used in shallow waters and the associated design and test methodologies may not be applicable to deep-water projects, where the depths may exceed about 1,000 meters. In cases of long pipe tiebacks, for example subsea-to-beach tiebacks, and in cases where the service temperature is above approximately 150° C., there exist limitations with current technology that may hinder the successful development of offshore, deep water oil or gas fields.
Current technologies include single pipe solutions, typically with insulation requirements in the heat transfer coefficient range of 3-5 W/m2 K, using polypropylene foam or polyurethane foam as the insulant, and so-called pipe-in-pipe systems wherein a second pipe surrounds the primary conduit, the annulus between the two pipes being filled with an insulating material.
Limitations and deficiencies of these technologies include:                Relatively high thermal conductivity of known insulating systems, necessitating excessively thick coatings to achieve the required insulation performance, leading to potential difficulties in foam processing, potential issues with residual stress, difficulties during pipe deployment, and sea-bed instability.        Insufficient resistance to temperatures from about 150° C. to above about 205° C., resulting in compression and creep resistance issues in high temperature installations at high water depths and material degradation resulting in a loss of mechanical properties.        Excessive costs due to poor material cost versus performance capabilities or high transportation and deployment costs.        Deployment and operation disadvantages with Pipe-In-Pipe systems due to weight factors leading to buckling and weld failure if not properly addressed, and the need for high gripping loads during pipe laying.        
Although the high temperature resistant pipe insulation systems disclosed in U.S. Pat. No. 8,397,765 by Jackson et al. (incorporated herein by reference in its entirety) provide improved thermal performance over known insulation systems at operating temperatures of about 130° C. or higher, these thermoplastic-based insulation systems generally have insufficient resistance to temperatures from about 150° C. to above about 205° C.
Therefore, there remains a need for improved insulated fluid and/or gas transport conduits undersea pipelines for carrying single or multi-phase fluids such as oil, gas and water, particularly those operating at temperatures from about 150° C. to above about 205° C.