Monetization of Remote Flared Natural Gas via Total Synthetic Conversion to Methane for Real-Time Production of Liquefied Natural Gas, Compressed Natural Gas or Natural Gas Hydrate

Abstract

Natural gas (methane) is of little value unless it can be brought from either the wellhead or process facility to the customer, who may be several thousand kilometers from the source. At the onset the most popular way to move gas from the source to the consumer was through pipelines, but as transportation distances increase, pipelines become uneconomical. Presently, liquefied natural gas (LNG), compressed natural gas (CNG) and gas-to-solids (GTS)/natural gas hydrate (NGH) options are the three other gas-to -gas (GTG) options to bring gas to market, which take advantage of the reduction in volume of the gas to economically transport the gas.This investigation on the Real-Time Conversion of the Entire Flare Associated Stranded Natural Gas Stream to Methane (Natural Gas) and subsequent monetization via CNG, LNG, and NGH,is focused on using customized skid mounted mini gas processing plants,to synthesize the C₂+ fractions to methane (C₁), through either cracking and steam reforming of the hydrocarbons. The flare stream is treated for acid gases, water vapor and solid impurities removal, which in this case, constitutes 2.39% of the flare gas stream. The Sweetened (97.61%) flare stream, which includes; ethane, propane, butanes and natural gasoline (pentanes and heavier hydrocarbons), captured in their vapor form or as natural gas liquids NGLs, is chemically synthesizedto the lighter molecules of C₁ (methane).     The gasification of liquid hydrocarbons involves a reduction of the overall carbon to hydrogen ratio. Also, the physical conversion of the resulting methane stream to either LNG, CNG, or NGH reduces the volume of the gas drastically for economic transportation to the market such as the power generation companies, heavy industries, commercial companies and residential estates. The theoretical physical volume reduction ranges are NGH (150 to 200), CNG (200 to 250), and LNG (600 to 625). Small-scale plants (mini-skid-mounted units) are designed to process natural gas flow rate of 50M scfd and below, to monetize flare streams in remote locations.Associated stranded flared natural gas is measured in either standard cubic feet (ft³) or cubic meters (m³). When it is converted toLNG, CNG or NGH, it is measured in mass units, usually tons or million tons (MT), and on reconversion to gas, it is sold by energy units (calorific value), commonly specified in dollars per British thermal unit (BTU), Joules (J) and Kilocalories (kcal.). In some other places gas is charged to residential customers at a price per 'therm', which is equivalent to 100,000 Btu or in gasoline gallon equivalent (GGE),specifically for CNG. The commonly used factor is 1,000Btu/scf while the fundamental differences between the GTG transportation options is the thermal efficiency of conversion of natural gas to products, which is 93+ % for CNG, 91% for NGH and between 85 to 91 % for LNG. For the Sweetened flare stream 19,522,000 scfd, the available retail heat energy for the various options is: CNG (18,155,460,000 btu), NGH (17,765,020,000 btu) and LNG (between 16,593,700,000 btu to   17,765,020,000 btu).