scholarly journals Slip-Flow Regimes in Nanofluidics: A Universal Superexponential Model

2021 ◽  
Vol 15 (5) ◽  
Author(s):  
Mohammad Aminpour ◽  
Sergio Andres Galindo Torres ◽  
Alexander Scheuermann ◽  
Ling Li
Keyword(s):  
Slip Flow ◽  
Flow Regimes

Performance of Lightly Loaded Gas Journal Bearings in the Slip-Flow and Turbulent-Flow Regimes

1968 ◽  
Vol 10 (4) ◽  
pp. 363-366
Author(s):  
M. D. Wood
Keyword(s):  
Steady State ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Reynolds Equation ◽  
Dynamic Performance ◽  
Slip Flow ◽  
Flow Regimes ◽  
Journal Bearings ◽  
Performance Parameters ◽  
Existing Data

The note compares recently published versions of the governing gas film equations for slip-flow and turbulent flow with Reynolds equation for laminar flow. The comparison shows how approximate values of steady-state and dynamic performance parameters may be deduced for the new conditions from existing data.

scholarly journals Gas flow mechanisms under the effects of pore structures and permeability characteristics in source rocks of coal measures in Qinshui Basin, China

2017 ◽  
Vol 35 (3) ◽  
pp. 338-355 ◽  
Author(s):  
Xiaowei Hou ◽  
Yanming Zhu ◽  
Shangbin Chen ◽  
Yang Wang
Keyword(s):  
Flow Regime ◽  
Mass Flux ◽  
Gas Flow ◽  
Slip Flow ◽  
Flow Regimes ◽  
Source Rocks ◽  
Cross Sectional ◽  
Direction Parallel ◽  
Permeability Characteristics ◽  
Flow Mechanisms

The gas flow mechanisms in source rocks of coal measures under the effects of the pore structures and permeability characteristics were investigated by field-emission scanning electron microscopy, low-pressure nitrogen gas adsorption, high-pressure mercury intrusion, and pressure pulse decay permeability method. Various flow regimes were distinguished in the pores and fractures of differing scales, and the mass fluxes through the same were calculated using the data obtained by the numerical and experimental investigations. Results indicated that mesopores predominated in shale, while coal contained well-developed mesopores and macropores. In addition, the permeabilities of coal and shale were observed to be significantly anisotropic and highly stress dependent. The cross-sectional area proportions of the pores per unit cross-sectional area of the matrix in the free molecular, transition, and slip flow regimes in shale and coal were determined to be, respectively, 0.2:0.7:0.1 and 0.15:0.6:0.25. In the free molecular and transition flow regimes, the mass flux decreased with increasing reservoir depth, while the reverse was the case in the slip flow regime. Further, in the continuum flow regime, the mass flux was unimodally distributed with respect to the reservoir depth. The total mass flux in coal was greater in the direction perpendicular to the bedding compared to the direction parallel to the bedding, while the reverse was the case in shale. In addition, the continuum flow regime predominated in coal in both the directions perpendicular and parallel to the bedding, but only in the direction parallel to the bedding in shale. This work presents a comprehensive model for the analysis of all the flow regimes in pores and fractures of differing scales, as well as the anisotropy. Findings of the study are meaningful for establishing the coupling accumulation mechanism of the Three Coal Gases and developing a unified exploration and exploitation program.

Analytical and Experimental Investigations of Gas-Flow Regimes in Shales Considering the Influence of Mean Effective Stress

SPE Journal ◽  
2016 ◽  
Vol 21 (02) ◽  
pp. 557-572 ◽  
Author(s):  
Alireza A. Moghadam ◽  
Rick Chalaturnyk
Keyword(s):  
Flow Regime ◽  
Effective Stress ◽  
Gas Flow ◽  
Gas Permeability ◽  
Slip Flow ◽  
Flow Regimes ◽  
Absolute Permeability ◽  
Apparent Permeability ◽  
Reservoir Conditions ◽  
Slip Flow Regime

Summary Flow conditions determine the flow regimes governing gas flow in porous media. Slip-flow regime commonly occurs in laboratory gas-permeability measurements, and one must consider the physics of that when finding the absolute permeability of a sample. Accurate permeability estimates are paramount for production forecasts, financial planning, and recovery estimation. Slip flow is present in low-permeability rocks, both in the laboratory environment and at reservoir conditions. Gas flow through the matrix lies under the slip-flow regime for the majority of low-permeability-reservoir production scenarios, and accurate prediction of pressure and production rate requires a good understanding of the flow regime. In this paper, an analytical study is conducted on the dominant flow regimes under typical shale-gas reservoir conditions. A flow-regime map is produced with respect to gas pressure and matrix permeability. Steady-state gas-permeability experiments are conducted on three shale samples. An analytical model is used to match the experimental results that could explain the order-of-magnitude difference between the permeabilities of gas and liquid in shales. Experimental results are combined with further tests available in the literature to inform a discussion of the model's parameters. The results improve the accuracy of gas-flow modeling and of absolute-permeability estimates from laboratory tests. Similar tests performed at various mean effective stresses investigate the influence of mean effective stress on flow regime and apparent permeability. The results indicate that flow regime is a function of mean effective stress, and that the apparent permeability of shale rocks is a function of both flow regime and mean effective stress.

Direct-Simulation Monte Carlo Investigation of a Berea Porous Structure

SPE Journal ◽  
2016 ◽  
Vol 21 (03) ◽  
pp. 0938-0946 ◽  
Author(s):  
Chariton Christou ◽  
S. Kokou Dadzie
Keyword(s):  
Monte Carlo ◽  
Velocity Profile ◽  
Porous Structure ◽  
Pore Diameter ◽  
Slip Flow ◽  
Direct Simulation Monte Carlo ◽  
Flow Regimes ◽  
Porous Structures ◽  
Direct Simulation ◽  
Simulation Monte Carlo

Summary Shale-gas and tight gas reservoirs consist of porous structures with pore diameter in the range of 1 to 200 nm. At these scales, the pore diameter becomes comparable to the gas mean free path. Flows in these structures fail often in the transition and slip flow regimes. Standard continuum fluid methods such as the Navier-Stokes-Fourier (NSF) set of equations fail to describe flows of these regimes. We present a direct-simulation monte carlo (DSMC) study of a 3D porous structure in an unlimited parallel simulation. The 3D geometry was obtained with microcomputed-tomography (micro-CT). The gas considered is CH4 (100%), and the gas intermolecular-collision model for the simulation is the variable hard sphere (VHS). Simulations were carried out for three different Knudsen (Kn) numbers within the transition and slip flow regimes. The results demonstrate some of the significant differences that appear in gas-flow properties depending on the Kn number and the flow regime. In addition, the velocity profile appears to depend on the Kn number. At the inlet of the porous structures, more-uniform velocity profile occurs for the three Kn numbers. At the outlet, the velocity profile varies depending on the Kn number. For Kn ≈ 0.037, a parabolic shape is observed for the velocity profile, whereas a more-uniform shape is observed for Kn ≈ 3.7.

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