Insulated pipe and method for preparing the same

#This invention pertains to a thermally insulated pipe-in-pipe assembly and a method of preparing the same.

#In deep-water hydrocarbon (e.g. oil, gas or mixtures thereof) extraction, crude oil or gas is extracted from below the sea floor and transferred via a pipeline system to the surface of the water. It is critically important to maintain the temperature of the oil or gas flowing through the pipeline, which typically is extracted at elevated temperatures (e.g., 60-300° C.), at temperatures above about 40° C. to avoid the precipitation of solid materials and hydrates which can lead to plugging of the pipeline and interfere with production. As the water temperature at great depths is slightly above freezing temperature (e.g, about 4° C.), provision must be made to insulate the pipelines. Further, if oil or gas flow must be interrupted for well maintenance or because of inclement weather conditions affecting surface platforms and interrupting pumping operations, it is important to maintain the temperature of residual crudes and gases within the pipeline and other components of the pipeline system (e.g., Christmas trees or subsea trees, risers, and the like) above precipitation temperatures for the particular crudes or gases being extracted in order to minimize or completely avoid the expensive and production-interrupting necessity of declogging and/or flushing the pipeline system before resuming production.

#To this end, many efforts have been made to provide economical and efficacious solutions to the problem of insulating underwater oil and gas pipeline systems. A particularly well-accepted method is to provide a pipeline comprising a pipe-in-pipe system wherein an inner pipe is surrounded by an outer pipe serving as a carrier pipe, and wherein the annular space defined by the inner pipe and outer pipe contains an insulating material. For example, U.S. Pat. No. 6,145,547 discloses a pipe-in-pipe assembly comprising a self-sustaining plate of microporous material surrounding an inner carrier pipe and encased by an outer carrier pipe, wherein a free passageway is provided for longitudinal gas flow. The assembly is maintained at reduced pressure for improved thermal insulation. U.S. Patent Application Publication 2004/0134556 A1 discloses a heat insulating system for tubular bodies (e.g., a pipe-in-pipe assembly) comprising at least two superimposed evacuated panels, each of which is separately placed around the inner pipe of the pipe-in-pipe assembly, and wherein the two opposed edges defining gaps of each of the at least two panels are placed so as not to coincide and thus eliminate a continuous passageway for the transfer of heat between the inner and outer pipes.

#FIG. 1 illustrates one embodiment of a sealed container useful in the context of the invention.

#FIG. 2 illustrates a cross-sectional view of two sealed containers of the embodiment of FIG. 1 positioned so as to encircle an inner tubular member.

#FIG. 3 illustrates a pipe-in-pipe assembly having an inner pipe 5, an outer pipe 6, and two sealed containers of the embodiment of FIG. 1 comprising a porous, resilient, and volumetrically compressible material placed within the annular space defined by an inner pipe and an outer pipe.

#The invention provides methods of preparing an insulated pipe-in-pipe assembly and system, as well as a pipe-in-pipe assembly and system.

#The inventive method of preparing an insulated pipe-in-pipe assembly comprises (i) providing an assembly comprising (a) at least one inner pipe, (b) at least one outer pipe that is positioned around the at least one inner pipe so as to create an annular space between the exterior surface of the at least one inner pipe and the interior surface of the outer pipe (and optionally additional annular spaces between the exterior surface of an outer pipe and the interior surface of an additional outer pipe), and (c) at least one container comprising porous, resilient, volumetrically compressible material, wherein the compressible material is restrained within the container and has a first volume, wherein the first volume of the compressible material is less than the unrestrained volume of the compressible material, and wherein the at least one container is disposed in the annular space (or one or more of the annular spaces in the event more than one outer pipe is utilized), and (ii) altering the at least one container to reduce the level of restraint on the compressible material to increase the volume of the compressible material to a second volume that is greater than the first volume, thereby forming an insulated pipe-in-pipe assembly.

#The assembly comprising at least one inner pipe, at least one outer pipe, and at least one container can be provided by practicing any suitable sequence of steps. For example, the container(s) can be placed adjacent to the exterior surface(s) of the inner pipe(s) and/or the interior surface of the outer pipe prior to positioning of the inner pipe(s) and outer pipe to form the annular space. Alternatively, the inner pipe(s) and outer pipe can be positioned to form the annular space prior to positioning the container(s) within the annular space. Other variations will be readily apparent to the ordinarily skilled artisan within the context of the invention, and the inner pipe(s) and/or the outer pipe(s) can be manipulated to achieve the desired positioning of the inner pipe(s) and outer pipe(s).