Natural Gas Liquids from the Associated Flare Gas Stream: Monetized in Real-Time via Various Qualitative Products

Abstract

Typically, the raw natural gas, released from underground porous reservoir rocks and passed through well bore system, that brings it to the surface wellhead is much different from the sweetened natural gas used by consumers. Conventionally, starting at the wellhead, down to the gas processing plants, the natural gas is purified to yield pure methane –rich stream and sweetened natural gas liquids (NGLs) comprising mostly, molecules that are heavier than methane like ethane, propane, butanes, pentanes and hexane plus hydrocarbon components. Consumers use natural gas in either of the two streams in various forms, such as, residential fuel for domestic heating, cooking, refrigeration and air conditioning; energy source which competes with petroleum products like fuel oil, diesel and liquefied petroleum gas (LPG); and feedstock to both petrochemical and chemical industries for manufacturing various intermediate chemicals and finished products such as ammonia (synthetic nitrogen fertilizer), methanol, chloromethanes, oxalcohols polythene, textiles, paints, synthetic drugs, toys, solvents, car tyres, explosives, soles of shoes et cetera. This investigation on the real-time monetization of natural gas liquids (NGLs) from the flared associated stranded natural gas in Nigeria, theoretically, reviewed the purification, recovery and separation of NGLs from a bulk natural gas stream, starting at the well head, to the gas processing plants, which normally entail, change of phase using either an Energy-Separating Agent(ESA) such as refrigeration for partial and total liquefaction/ fractionation or a Mass-Separating Agent (MSA) such as, the adsorption and absorption processes. It showed that the NGL volume extractable depends on the amount of gas available (flow rate), the NGL contained in the gas (composition), the processing technique employed by the processing plant et cetera. Usually, NGLs can comprise from 5% to over 50% of the natural gas stream. With a flow rate of 20million scfd (20MMscfd) on a sweetened composition of the flared associated stranded natural gas stream in Nigeria (table 3), the real-time daily NGLs component by component was obtained table 4, which indicates that about 160 bpd of ethane, 122 bpd propane, et cetera, would be available for monetization in various qualitative products that are in very high demand.