Stranded Gas is a popular term for natural gas reserves which due to physical and/or economical reasons, such as remoteness, difficult geology or gas composition of the reservoir cannot be produced. Stranded gas always has attracted the attention of the oil & gas industry as innovations in technology, fabrication, execution and growing natural gas usage creates opportunities to monetise such stranded gas.
This paper intends to discuss emerging technical solutions to liquefy and process associated or nonassociated Stranded Gas with the help of cryogenic technology. Firstly, small-to-mid scale technologies to liquefy natural gas are addressed. Small-scale LNG plants for the purpose of this paper are defined as plants with a capacity of typically 70.000 tpa (200 tpd) to 200.000 tpa (600 tpd) normally using plate fin heat exchangers for the liquefaction section while mid-scale LNG plants are understood to cover larger capacities up to about 1.200.000 tpa (3.500 tpd) using coil wound heat exchangers. Secondly floating production and storage units for LNG production (LNG FPSO's) with a capacity of up to 2.500.000 tpa are introduced. Thirdly a specific but potentially attractive solution is to monetise high nitrogen reservoirs, so called nitrogen rejection units (NRU's), are outlined.
Starting with a description of suitable process solutions and their application envelope, executed projects will be discussed. Given the remoteness of a typical stranded gas project standardisation and modularisation are a key strategy to reduce plant cost, schedule and execution risk. Respective strategies and approaches will be illustrated. Finally, economical considerations will conclude the paper indicating that small- and mid scale LNG, floating LNG and nitrogen rejection units can be economically viable in many instances to monetise stranded natural gas.