Recovery of Casing Gas from Remote and Scattered Oil Wells

Abstract It is difficult to collect/gather casing gas given the number of wells and their location in an undulating terrain without separate gas pipelines. To solve this obstacle, synchronal rotary compressors were specifically designed for the demonstration area. In the demonstration area, synchronal rotary compressors and walking beam compressors were installed on oil well pads to inject casing gas into oil pipes. This approach decreases wellhead back pressure to ensure crude oil production and avoid casing gas flaring or venting. When oil wells didn’t connect to pipelines, the moderate compression and vehicle transportation method was applied to gather the gas. The oil and gas mixture is transported to batteries where a light hydrocarbon recovery plant has been built. Dry gas, LPG and stable light oil are produced from the mixture using a separation and refrigeration process. LPG and light oil are shipped to market, and the dry gas is used to generate electric power. The walking beam compressors were installed in 2011 and had been in use for more than dozens of months. The synchronal rotary compressors were installed in 2010 and had been in use for more than years. The related light hydrocarbon recovery plant was built in 2011 and is fully operational. Collectively, the gas-gathering and processing devices can recover more associated gas -- up to 20,000 cubic meters per day -- and reduce GHG emission by 15,000 tonnes CO2E yearly. The total investment was $8.2 million including gas gathering system, crude oil stabilization device, light hydrocarbon recovery plant, waste heat recovery, etc. The payback period was 4.5 years, and the intenal rate of return (IRR) was 22.5%.