Appearing first as a dot on the horizon, the remote Nini oil field on Europe’s rugged North Sea slowly comes into view from a helicopter.Used to extract fossil fuels, the field is now getting a second lease on life as a means of permanently storing planet-warming carbon dioxide beneath the seabed.In a process that almost reverses oil extraction, chemical giant INEOS plans to inject liquefied CO2 deep down into depleted oil reservoirs, 1,800 meters (5,900 feet) beneath the seabed.The Associated Press made a rare visit to the Siri platform, close to the unmanned Nini field, the final stage in INEOS’...