Shale gas transport in rock matrix: Diffusion in the presence of surface adsorption and capillary condensation

Chen, Jin-Hong; Althaus, Stacey M.; Liu, Hui‐Hai; Sun, Qiushi

doi:10.1016/j.jngse.2019.03.015

Cited by 8 publications

(3 citation statements)

References 16 publications

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“…Fluid transport from the matrix to fracture depends on diffusion motivated by concentration difference. 49 Because the Knudsen number in fracture of our model is on average 0.03, we ignore slip flow for simplification. Convection is simplified as viscous flow, which obeys Darcy's law.…”

Section: Model Developmentmentioning

confidence: 99%

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Influence of Water on Gas Transport in Shale Nanopores: Pore-Scale Simulation Study

Zhang

Yan

et al. 2020

Energy Fuels

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Water exists in shale gas reservoirs in the form of connate water and retained fracturing fluid. The nanoscale interaction between gas and water plays an important role in gas transport in shale nanopores. However, the research comprehensively focusing on gas−water transport in all pore types including organic pores, inorganic pores, and fractures is limited. In this work, we use a pore-scale model to study the influence of water on gas transport in shale nanopores. Shale pore structure of the model includes three organic pores, three inorganic pores, and one fracture. Because fluids have different transport behaviors in each sort of pore, a mathematical formulation is derived to describe fluid adsorption−desorption, diffusion, and flow (convection) in organic pores, inorganic pores, and fractures, respectively. The mathematical formulation is used in the model to simulate gas−water transport at a wide range of pressures and water saturations. The influence of water on gas transport is analyzed by comparing equivalent gas flow rate in two-phase cases and single-phase (gas) cases. Results indicate that the equivalent gas flow rate in twophase cases is on average 43.03% of the equivalent gas flow rate in single-phase cases. The impact of water mainly happens in the fracture due to mutual interference of gas and water during two-phase flow. This effect induces a linear relation between equivalent gas flow rate and water saturation. The two-phase flow in the fracture dominates gas transport capability in shales. The gas in inorganic pores has much better movability than the gas in organic pores under a limited pressure drop. In the case of water saturation 40% and average pressure 22 MPa, most of the gas in inorganic pores can transport out of the matrix, while over 54% of the gas in organic pores fails to transport out. This implies that shale gas production largely depends on free gas transport. Enhancing adsorbed gas recovery is essential to maintain good well productivity.

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Section: Model Developmentmentioning

confidence: 99%

“…Mass transport in fracture includes diffusion and flow (convection). Fluid transport from the matrix to fracture depends on diffusion motivated by concentration difference . Because the Knudsen number in fracture of our model is on average 0.03, we ignore slip flow for simplification.…”

Section: Model Developmentmentioning

confidence: 99%

Influence of Water on Gas Transport in Shale Nanopores: Pore-Scale Simulation Study

Zhang

Yan

et al. 2020

Energy Fuels

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“…8 NMR has also been used to investigate pore structure in tight sandstones 10 and to obtain mobility of liquid hydrocarbons in well-characterized hierarchical carbon materials. 11 In addition, NMR has proved to be effective in studying bound water saturation and permeability in tight sandstones. 12,13 Additional advances also include application of downhole NMR tools to estimate fluid type and saturation using T 1 −T 2 mapping 14 and estimation of pore-size distributions and reservoir permeability.…”

Section: Introductionmentioning

confidence: 99%

Fluid Transport Mechanisms in Unconventional Tight Rocks Based on NMR Imaging

Kortunov

Messner

et al. 2022

Energy Fuels

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Unconventional resource development has been enabled by advanced completion methods such as horizontal drilling and multistage hydraulic fracturing. However, unconventional reservoir production rates decline more rapidly relative to conventional reservoirs, and recovery factors remain relatively low. Enhancing hydrocarbon recovery can be improved through a fundamental understanding of transport processes inside unconventional rocks. This work provides unique insights into fluid transport mechanisms in unconventional rocks during miscible displacement using a direct and noninvasive method to quantitatively detect hydrocarbons and their distribution inside rock samples by proton NMR imaging coupled with theoretical analysis of experimental results. This study shows the importance of unconventional rock morphology and pore structure to better understanding fluid transport and overall mass transfer rates. Different transport mechanisms in representative homogeneous and heterogeneous unconventional tight rocks are demonstrated. For homogeneous tight rocks, viscous or hydraulic flow is the dominant fluid transport mechanism in the direction of an applied pressure differential. However, a more complex behavior is observed in heterogeneous tight rocks. Despite smaller average pore sizes, the heterogeneous tight rocks can possess macroscopic permeabilities comparable to largerpore rocks due to microfracture(s) in the sample that remain open at field relevant net confining stresses. Such microfractures enable a dual fluid transport mechanism inside the heterogeneous tight rock: hydraulic fluid transport along microfracture(s) and diffusion dominated fluid exchange across microfracture(s) inside the rock matrix. Overall mass transfer rates through heterogeneous tight rocks depends on the interplay of these two transport mechanisms, relative rates and travel distances. Experiments with lab cores showed that for fluid exchange of an injected fluid with the in situ fluid, diffusion in the matrix is a rate limiting step. More study is required to upscale our observations to a field relevant scale.

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A permeation model of shale gas in cylindrical-like kerogen pores at geological conditions

Sun

Liu

Cao

2019

Chemical Engineering Science

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Shale gas transport in rock matrix: Diffusion in the presence of surface adsorption and capillary condensation

Cited by 8 publications

References 16 publications

Influence of Water on Gas Transport in Shale Nanopores: Pore-Scale Simulation Study

Influence of Water on Gas Transport in Shale Nanopores: Pore-Scale Simulation Study

Fluid Transport Mechanisms in Unconventional Tight Rocks Based on NMR Imaging

A permeation model of shale gas in cylindrical-like kerogen pores at geological conditions

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