Bruce T. Kelley

Method and apparatus to prevent hydrate formation in full wellstream pipelines

The apparatus and method disclosed prevents hydrate formation in subsea oil and gas pipelines including at least one marine riser. The invention reduces the pressure on the fluids in a shut in pipeline by displacing fluids in the system into a reservoir thereby reducing the height of the column of fluids in the riser. A pump may be used to remove additional fluid from the fluid reservoir and pipeline to ensure the hydrostatic pressure associated with the final fluid level is below the pressure where hydrates may form at shut in temperatures. During start-up, a pump removes fluids from the fluid reservoir at about the same rate as produced fluids are allowed into the pipeline. The pump is shut down and pipeline operations are resumed when the liquid full wellstream fluids in the pipeline warm to a temperature outside the range where hydrates may form.