We are treding on ground I know little about, but maybe the venturi principle... Make the pipe smaller, the flow will increase in speed, then lower the pressure until you return to normal.
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In theory you would have to cool the gas to permit the same volume of flow at a lower pressure. In reality to do this would require the insulation of the entire pipeline and significant cooling because volume change due to cooling is based on absolute temperatures.
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you need to cool the gas - so run it deeper in the ground - or install refrigeration units.
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Only one way: enlarge the pipe diameter.