Modular one-step gas-to-liquid reactor for stranded natural gas monetization: Comprehensive thermodynamic assessment, techno-economic evaluation, and optimized field deployment

The persistent flaring of stranded natural gas (SNG) during crude oil extraction contributes substantially to global carbon emissions while wasting a valuable hydrocarbon resource. To address this challenge and empower sustainable utilization of this stranded hydrocarbon feedstock, our study proposes a first-of-its-kind modular gas-to-liquid (GTL) system for the one-step generation of liquid fuel (LF) along with an economical strategy for dynamic field deployment. This novel reactor assembly integrates mixed reforming (MR) technology for syngas generation from SNG, heat exchangers for enhanced energy recovery from the process, and Fischer-Tropsch (FT) synthesis for syngas to LF conversion within a single, compact unit operating under elevated pressure. Four plausible reactor configurations with varying heat integration and side-product (light-end hydrocarbon) utilization strategies were conceptualized and simulated in ASPEN Plus to comprehensively assess their thermodynamic, environmental, and economic performance under steady-state operation. Reactor configuration presented as Case 3, enabling extensive heat integration and light-end recycle to the process, achieves maximum reduction in CO 2 emissions compared to conventional flaring (56.9%), highest carbon efficiency (62.8%), an effective thermal efficiency of 60.9%, along with an LF yield of 7.3 gal per million cubic feet (MCF) of SNG. The thermodynamic evaluation was coupled with a comprehensive techno-economic analysis, which reveals Case 3 (without electricity cogeneration) as the most cost-effective configuration, well-suited for field deployment. Additionally, a dynamic reactor deployment framework, formulated as a mixed-integer linear programming (MILP) model for the Bakken shale formation, identifies optimal strategies for reactor purchase, relocation, operation, and decommissioning across 30 gas wells with declining SNG production and real-world product price variation. Case 3 (without electricity cogeneration) yields a relative net present value (NPV) of $44.2 million and a 21.0% reduction in CO 2 emissions over a simulation period of 60 years compared to the baseline scenario involving SNG flaring. Overall, this work establishes a scalable, sustainable, and economical strategy for utilizing SNG, offering an economically practical pathway toward low-carbon and sustainable oil field operations. • First-of-its-kind modular GTL reactor enables on-site SNG to LF conversion. • 4 reactor configurations evaluated for thermodynamic and economic performance. • MILP-based strategy identifies most profitable modular reactor deployment. • Achieves $44.2M NPV and reduces CO₂ emissions by 21%.