Pipe-in-pipe pipelines

A method of connecting an in-line subsea structure to a pipe-in-pipe (PIP) pipeline for laying in a marine environment, the PIP pipeline comprising a plurality of PIP pipeline sections, each PIP pipeline section of the plurality of PIP pipeline sections having at least metal inner and outer pipes and an annular space thereinbetween, the PIP pipeline having one or more PIP connectors, a first PIP pipeline section of the plurality of PIP pipeline sections and a second PIP pipeline section of the plurality of pipeline sections being connected to one another with a PIP connector from the one or more PIP connectors, the PIP connector having a first connector end and a second connector end, the first connector end comprising inner and outer longitudinal collars corresponding in circumference to the circumferences of the inner and outer pipes of the first PIP pipeline section, and welded to the first PIP pipeline section, and the second connector end comprising a machined portion configured to match and connect with a complementary portal or bore of the in-line subsea structure, and a coupling portion coupled to the second PIP pipeline section, said coupling being decoupable from the second PIP pipeline section, the method comprising at least the steps of:

• (i) providing the PIP pipeline;
• (ii) decoupling the coupling portion that is at the second connector end of the connector and coupled to the second PIP pipeline section to provide the machined portion of the PIP connector that is configured to match and connect with the complementary portal or bore of the in-line subsea structure;
• and
• (iii) connecting the in-line subsea structure onto the machined portion of the PIP connector to connect the in-line subsea structure to the PIP pipeline,
• wherein the in-line subsea structure is a pipeline end structure or a pipeline intermediate structure that is located at a subsea location.