Abstract: Large gas pockets in a crude oil transfer pipeline are detected and separated. As a large gas pocket forms, the liquid level drops (and the hydraulic head declines) in the export riser portion of the transfer pipeline, increasing the pressure required to transfer the fluid. Detection of the lower level and separation decreases the pressure required. Smaller gas pockets, which can be swept down the export riser portion, are not separated. The detecting and separating functions can be combined in a float-type gas vent valve, or separate gas detectors and gas vent valves can be used. The separated gas can be recombined with the crude oil, or used at an import platform, or separately transported to an on-shore facility. If the separated gas requires pressurization, a compressor-expander may be used to compress gas for flow in one direction and recover power from the expanding gas during flow in the other direction.