Recovery of Multicomponent Shale Gas from Single Nanopores

Wu, Haiyi; He, Yan; Qiao, Rui

doi:10.1021/acs.energyfuels.7b01013

Cited by 32 publications

(29 citation statements)

References 38 publications

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“…The primary driver of change in composition in unconventional reservoirs is believed to be absorption: as the pressure decreases due to depletion of the reservoir, gas which is adsorbed onto the walls desorbs to the bulk and flows to the wellhead, 31 changing the composition reaching the wellhead. 32 However, complex behavior can originate because of the small pores acting as a molecular sieve for large molecules, only allowing the small molecules to flow 30 and because individual components have different mobilities; for example, methane is more mobile than ethane and propane. 33 Pressure decline in the reservoir altering the thermodynamic equilibrium of hydrocarbons can also lead to hydrocarbon composition variability as a function of time, as is the case for conventional reservoirs.…”

Section: ■ Methodologymentioning

confidence: 99%

Projecting the Temporal Evolution of Methane Emissions from Oil and Gas Production Sites

Cardoso-Saldaña

Allen²

2020

Environ. Sci. Technol.

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Many recent studies have reported methane emissions from oil and gas production regions, often reporting results as a methane emission intensity (methane emitted as a percentage of natural gas produced or methane produced). Almost all of these studies have been instantaneous snapshots of methane emissions; however, total methane emissions from a production site and the methane emission intensity would be expected to evolve over time. A detailed site-level methane emission estimation model is used to estimate the temporal evolution of methane emissions and the methane emission intensity for a variety of well configurations with and without emission mitigation measures in place. The general pattern predicted is that total emissions decrease over time as production declines. Methane emission intensity shows complex behavior because production-dependent emissions decline at different rates and some emissions do not decline over time. Prototypical uncontrolled wet gas wells can have approximately half of their emissions over a 10 year period occur in the first year; instantaneous wellsite methane emission intensities range over a factor of 3 (0.62–2.00%) in the same period, with a 10 year production weighted-average lifecycle methane emission intensity of 0.79%. Including emission control in the form of a flare can decrease the average lifecycle methane emission intensity to 0.23%. Emissions from liquid unloadings, which are observed in subsets of wells, can increase the lifecycle methane emission intensity by up to a factor of 2–3, between 1.2 and 2.3%, depending on the characteristics of the unloadings. Emissions from well completion flowbacks raise the average lifecycle methane emission intensity from 0.79 to 0.81% for flowbacks with emission controls; for flowbacks with uncontrolled emissions, lifecycle methane emissions increase to 1.26%. Dry gas and oil wells show qualitatively similar temporal behavior but different absolute emission rates.

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Section: ■ Methodologymentioning

confidence: 99%

Projecting the Temporal Evolution of Methane Emissions from Oil and Gas Production Sites

Cardoso-Saldaña

Allen²

2020

Environ. Sci. Technol.

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“…Fortunately, molecular dynamics (MD) simulations, originating from Newtonian mechanics to define the force and capture the corresponding motion trajectory of all the particles, make it possible to directly characterize and observe the dynamics behaviors of each atom or molecule at the nanoscale. − Typically for shale nanopores flow, the multiple phases (e.g., water and methane) and radical ambient conditions (e.g., high pressure and temperature) can be easily taken account into MD simulations system, − and, hence, a great deal of MD simulation studies have been performed to reveal the transport characteristics of shale gas within nanopores, providing important cognitions and fundamental frameworks for gas transport through shale nanopores. In this work, the authors attempt to present a comprehensive review on current advances of shale gas transport through microporous/nanoporous media from molecular perspectives, including molecular models, flow simulation strategies, and significant results.…”

Section: Introductionmentioning

confidence: 99%

Transport of Shale Gas in Microporous/Nanoporous Media: Molecular to Pore-Scale Simulations

Fan

et al. 2020

Energy Fuels

136

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As the typical unconventional reservoir, shale gas is believed to be the most promising alternative for the conventional resources in future energy patterns, attracting more and more attention throughout the world. Generally, the majority of shale gas is trapped within the tight shale rock with ultralow porosity (<10%) and ultrasmall pore size (as less as several nanometers). Thus, the accurate understanding of gas transport characteristic and its underlying mechanism through these microporous/nanoporous media is critical for the effective exploitation of shale reservoir. In this context, we present a comprehensive review on the current advances of multiscale transport simulations of shale gas in microporous/nanoporous media from molecular to pore-scale. For the gas transport in shale nanopores using molecular dynamics (MD) simulations, the structure and force parameters of various nanopore models, including organic models (graphene, carbon nanotubes, and kerogen) and inorganic models (clays, carbonate, and quartz), and flow simulation strategies (such as nonequilibrium molecular dynamics (NEMD) and Grand Canonical Monte Carlo simulations) are systematically introduced and clarified. The significant MD simulation results about gas transport characteristic in shale nanopores then are elaborated respectively for different factors, including pore size, ambient pressure, nanopore type, atomistic roughness, and pore structure, as well as multicomponent. Besides, the two-phase transport characteristic of gas and water is also discussed, considering the ubiquity of water in shale formation. For the lattice Boltzmann method (LBM) and pore network model (PNM) approaches to conduct pore-scale simulations, we briefly review its origins, modifications, and applications for gas transport simulations in a microporous/nanoporous shale matrix. Particularly, the upscaling methods to incorporate MD simulation into LBM and PNM frameworks are emphatically expounded in the light of recent attempts of MD-based pore-scale simulations. It is hoped that this Review would be helpful for the readers to build a systematical overview on the transport characteristic of shale gas in microporous/nanoporous media and subsequently accelerate the development of the shale industry.

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“…To our knowledge, most recently, some MD simulations − have been executed to consider the nanoconfined flow behavior of shale gas under realistic ambient pressure, indicating that the flow velocity of methane gas is still plunger-shape across the channel with a significant slip length (as much as 100 nm). Unfortunately, the walls used in these studies are universally limited to graphite-based materials possessing ideally smooth surfaces, such as graphene sheets, which are significantly different from the amorphous structure of shale kerogen. − Therefore, although the invalidity of the continuous model for describing the nanoscale flow has been successfully justified by abundant studies under specific conditions (ideally smooth walls and ultra-low ambient pressure), − ,− there is still no direct evidence or related investigation to reveal the nanoconfined flow behavior of shale gas through amorphous kerogen nanopores.…”

Section: Introductionmentioning

confidence: 99%

Nanoconfined Transport Characteristic of Methane in Organic Shale Nanopores: The Applicability of the Continuous Model

Xia

et al. 2020

Energy Fuels

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In recent years, since the fast mass transport emerges from some low-dimensional nanostructures (e.g., graphene and CNTs), the applicability of the continuous model (e.g., hydrodynamics) for describing the nanoscale flow has been intensely challenged, even for shale gas. As the typical tight rock with numerous nanopores, most scholars considered that gas transport capacity (permeability) within a shale organic matrix (i.e., kerogen) would be significantly enhanced as well, due to the nanoscale slip effect. Herein, we perform comprehensive molecular dynamics (MD) simulations to reveal the realistic gas transport behavior through shale kerogen nanopores. The results show that, interestingly, all the velocity profiles for different kerogen (type I, II, and III) nanopores display no-slip parabolic shape, which are quantitatively satisfied with the continuous model under various conditions, including pressure drop (0.25−1 MPa), pore size (2−8 nm), and ambient pressure (5−50 MPa) and temperature (300−390 K). In particular, using potential energy surface (PES) and particle trajectory capture (PTC) technologies, we find that, confined by the rough kerogen walls and ultra-high reservoir pressure, the methane molecules collide with the walls frequently but just go round and round without moving along the walls (confined reflection), and thus, the tangential momentum (slip velocity) is negligible at the walls. Importantly, this work demonstrates that traditional consideration of the slip effect is redundant for methane transport in organic shale (kerogen) nanopores and will overestimate the gas permeability immensely (as much as 100 times). These new insights would be helpful for the precise understanding and accurate modeling of methane transport within nanoporous shale rocks.

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Recovery of Multicomponent Shale Gas from Single Nanopores

Cited by 32 publications

References 38 publications

Projecting the Temporal Evolution of Methane Emissions from Oil and Gas Production Sites

Projecting the Temporal Evolution of Methane Emissions from Oil and Gas Production Sites

Transport of Shale Gas in Microporous/Nanoporous Media: Molecular to Pore-Scale Simulations

Nanoconfined Transport Characteristic of Methane in Organic Shale Nanopores: The Applicability of the Continuous Model

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