Flaring is a routine practice in the oil, gas, and petrochemical industries, primarily employed to ensure safe, and stable operations during unplanned upsets, maintenance, and start-up or shutdown conditions [1]. However, flaring results in the release of significant volumes of greenhouse gases (GHGs), contributing to environmental degradation and substantial energy and economic losses. Amount of gas that is flared varies significantly with time, facilities, and technologies employed, but the quantity of flare gas can be often very large. For instance, approximately one-third of the total natural gas produced from the Bakken formation—equivalent to around 250 MMSCFD—is either vented or flared. Similarly, the Eagle Ford formation in Texas accounts for nearly 100 MMSCFD of flared gas [2,3,4]. Given the environmental and economic consequences, the recovery and utilization of flare gas have become essential priorities for sustainable development in the energy sector. Over the past decade, a variety of technological approaches have been developed and deployed to recover flare gas and convert it to value-added products. These include gas compression for direct utilization as fuel gas or reintegration into the process feed stream, compression and reinjection into oil reservoirs to support enhanced oil recovery (EOR), and conversion into natural gas liquids (NGLs) for use in petrochemical production. In addition, flare gas can be liquefied or compressed into liquefied natural gas (LNG) or compressed natural gas (CNG), enabling its transport and use as an alternative fuel. Other utilization pathways include gas-to-liquid (GTL) technologies for producing synthetic fuels, conversion to chemicals such as methanol, dimethyl ether (DME), ammonia, or ethylene, and gas-to-wire (GTW) systems for electricity generation at remote or stranded sites [1,3]. However, the feasibility and economic justification of these recovery methods are highly dependent on flare gas characteristics, such as flowrate, composition, pressure, and source variability. This is particularly challenging in the context of unconventional shale wells, which generally have lower individual well production compared to conventional wells, leading to less favorable economies of scale for traditional gas recovery infrastructure. Furthermore, many of the technologies mentioned above are not capable of handling large variations in feed gas, which is often observed for flare gas.
This study focuses specifically on the utilization of flare gas from unconventional wells, proposing a modular, scalable process model that enables distributed gas valorization. The core of the process involves the conversion of flare gas components into benzene and other valuable byproducts such as ethane, ethylene, and toluene through a direct non-oxidative dehydroaromatization (DHA) process, by microwave (MW)-assisted thermo-catalytic technology. A model of the laboratory-scale reactor is developed. Reaction mechanisms are proposed based on the observed data and rate parameters are estimated by using in-house experimental data under MW-assisted conditions. The laboratory scale reactor model is then scaled up to a modular scale reactor for which a multi-scale, multi-physics model is developed [5]. A plant-wide process model is developed to simulate the integrated MW-assisted DHA system that produces the products at their desired specifications. To evaluate the commercial potential of this novel approach, techno-economic analysis (TEA) and life cycle assessment (LCA) are performed, and the results are benchmarked against existing literature and industrial practices. A comprehensive sensitivity analysis is also conducted to assess the impact of key variables on the levelized cost of benzene (LCOB). These variables include plant scale and throughput, the target internal rate of return (IRR), the capital cost of MW reactors, feedstock availability and utility prices, and catalyst cost and replacement frequency.
References:
- Roehner, R.; Panja, P.; Deo, M. Reducing Gas Flaring in Oil Production from Shales. Energy & Fuels, 2016, 30, 7524-7531.
- Tan, E.C.D.; Schuetzle, D.; Zhang, Y.; Hanbury, O. Schuetzle, R. Reduction of greenhouse gas and criteria pollutant emissions by direct conversion of associated flare gas to synthetic fuel oil wellheads. J. Ener. Envir. Eng., 2018, 9, 305-321.
- Khalili-Garakani, A.; Nezhadfard, M.; Iravaninia, M. Enviro-economic investigation of various flare gas recovery and utilization technologies in upstream and downstream of oil and gas industries. Cleaner Production, 2022, 346, 131218.
- Aoun, A.E.; Pu, H.; Khtib, Y.; Ameur, M.C.B. Natural gas flaring status in the Bakken shale play and potential remedial solutions. Fuel, 2023, 342, 127807.
- Mevawala, C.; Bai, X.; Hu, J.; Bhattacharyya, D. Plant-wide modeling and techno-economic analysis of a direct non-oxidative methane dehydroaromatization process via conventional and microwave-assisted catalysis. Applied Energy, 2023, 336, 120795.
