Laboratory measurement and interpretation of nonlinear gas flow in shale

2015 ◽  
Vol 26 (06) ◽  
pp. 1550063 ◽  
Author(s):  
Yili Kang ◽  
Mingjun Chen ◽  
Xiangchen Li ◽  
Lijun You ◽  
Bin Yang
Keyword(s):  
Pore Pressure ◽  
Gas Flow ◽  
Gas Adsorption ◽  
Slip Flow ◽  
Transition Flow ◽  
Confining Stress ◽  
Slippage Effect ◽  
Longmaxi Shale ◽  
Close Relationship ◽  
Flow Mechanisms

Gas flow mechanisms in shale are urgent to clarify due to the complicated pore structure and low permeability. Core flow experiments were conducted under reservoir net confining stress with samples from the Longmaxi Shale to investigate the characteristics of nonlinear gas flow. Meanwhile, microstructure analyses and gas adsorption experiments are implemented. Experimental results indicate that non-Darcy flow in shale is remarkable and it has a close relationship with pore pressure. It is found that type of gas has a significant influence on permeability measurement and methane is chosen in this work to study the shale gas flow. Gas slippage effect and minimum threshold pressure gradient weaken with the increasing backpressure. It is demonstrated that gas flow regime would be either slip flow or transition flow with certain pore pressure and permeability. Experimental data computations and microstructure analyses confirm that hydraulic radius of flow tubes in shale are mostly less than 100 nm, indicating that there is no micron scale pore or throat which mainly contributes to flow. The results are significant for the study of gas flow in shale, and are beneficial for laboratory investigation of shale permeability.

scholarly journals Nonlinear Seepage Model of Gas Transport in Multiscale Shale Gas Reservoirs and Productivity Analysis of Fractured Well

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Ting Huang ◽  
Xiao Guo ◽  
Kun Wang
Keyword(s):  
Gas Flow ◽  
Slip Flow ◽  
Gas Production ◽  
Productivity Analysis ◽  
Transition Flow ◽  
Gas Reservoirs ◽  
Slippage Effect ◽  
Wellbore Pressure ◽  
Fractured Well ◽  
And Diffusion

Shale is abundant in nanoscale pores, so gas flow in shales cannot be simply represented by Darcy formula anymore. It is crucial to figure out the influence of gas flow in nano/micro pores on actual productivity, which can provide basic theories for optimizing parameters and improving the gas production from engineering perspective. This paper considers the effects of slippage and diffusion in nanoscale based on Beskok-Karniadakis (BK) equation, which can be applicable for different flow regimes including continuum flow, slip flow, transition flow, and free-molecule flow. A new non-Darcy equation was developed based on the analysis of effects of high order terms of BK equation on permeability correction factor. By using the conformal transformation principle and pressure coupling method, we established the productivity formula of fractured well (infinite and limited conductivity) satisfying mass variable seepage flowing in fractures. The simulation results have been compared with field data and influencing parameters are analyzed thoroughly. It is concluded that slippage effect affects gas production of fractured well when wellbore pressure is less than 15 MPa, and the effects of slippage and diffusion have greater influence on gas production of fractured well for reservoir with smaller permeability, especially when permeability is at nano-Darcy scale.

scholarly journals NMR Analysis Method of Gas Flow Pattern in the Process of Shale Gas Depletion Development

Geofluids ◽  
2022 ◽  
Vol 2022 ◽  
pp. 1-7
Author(s):  
Rui Shen ◽  
Zhiming Hu ◽  
Xianggang Duan ◽  
Wei Sun ◽  
Wei Xiong ◽  
...  
Keyword(s):  
Flow Pattern ◽  
Pore Pressure ◽  
Shale Gas ◽  
Gas Flow ◽  
Continuous Medium ◽  
Slip Flow ◽  
Flow Patterns ◽  
Transitional Flow ◽  
Analysis Method ◽  
Adsorbed Gas

Shale gas reservoirs have pores of various sizes, in which gas flows in different patterns. The coexistence of multiple gas flow patterns is common. In order to quantitatively characterize the flow pattern in the process of shale gas depletion development, a physical simulation experiment of shale gas depletion development was designed, and a high-pressure on-line NMR analysis method of gas flow pattern in this process was proposed. The signal amplitudes of methane in pores of various sizes at different pressure levels were calculated according to the conversion relationship between the NMR T 2 relaxation time and pore radius, and then, the flow patterns of methane in pores of various sizes under different pore pressure conditions were analyzed as per the flow pattern determination criteria. It is found that there are three flow patterns in the process of shale gas depletion development, i.e., continuous medium flow, slip flow, and transitional flow, which account for 73.5%, 25.8%, and 0.7% of total gas flow, respectively. When the pore pressure is high, the continuous medium flow is dominant. With the gas production in shale reservoir, the pore pressure decreases, the Knudsen number increases, and the pore size range of slip flow zone and transitional flow zone expands. When the reservoir pressure is higher than the critical desorption pressure, the adsorbed gas is not desorbed intensively, and the produced gas is mainly free gas. When the reservoir pressure is lower than the critical desorption pressure, the adsorbed gas is gradually desorbed, and the proportion of desorbed gas in the produced gas gradually increases.

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.

scholarly journals Klinkenberg effect for gas permeability and its comparison to water permeability for porous sedimentary rocks

2006 ◽  
Vol 3 (4) ◽  
pp. 1315-1338 ◽  
Author(s):  
W. Tanikawa ◽  
T. Shimamoto
Keyword(s):  
Pore Pressure ◽  
Water Permeability ◽  
Gas Flow ◽  
Gas Permeability ◽  
Slip Flow ◽  
Sedimentary Rocks ◽  
Water Film ◽  
Klinkenberg Effect ◽  
Two Phase ◽  
Order Of Magnitude

Abstract. The difference between gas and water permeabilities is significant not only for solving gas-water two-phase flow problems, but also for quick measurements of permeability using gas as pore fluid. We have measured intrinsic permeability of sedimentary rocks from the Western Foothills of Taiwan, using nitrogen gas and distilled water as pore fluids, during several effective-pressure cycling tests at room temperature. The observed difference in gas and water permeabilities has been analyzed in view of the Klinkenberg effect. This effect is due to slip flow of gas at pore walls which enhances gas flow when pore sizes are very small. Experimental results show (1) that gas permeability is larger than water permeability by several times to one order of magnitude, (2) that gas permeability increases with increasing pore pressure, and (3) that water permeability slightly increases with increasing pore-pressure gradient across the specimen. The results (1) and (2) can be explained by Klinkenberg effect quantitatively with an empirical power law for Klinkenberg constant. Thus water permeability can be estimated from gas permeability. The Klinkenberg effect is important when permeability is lower than 10−18 m2 and at low differential pore pressures, and its correction is essential for estimating water permeability from the measurement of gas permeability. A simple Bingham-flow model of pore water can explain the overall trend of the result (3) above. More sophisticated models with a pore-size distribution and with realistic rheology of water film is needed to account for the observed deviation from Darcy's law.

A Nano-Pore Scale Gas Flow Model for Shale Gas Reservoir

2014 ◽  
Author(s):  
Y.. Li ◽  
X.. Li ◽  
J.. Shi ◽  
H.. Wang ◽  
L.. Wu ◽  
...  
Keyword(s):  
Gas Flow ◽  
Pore Diameter ◽  
Knudsen Diffusion ◽  
Adsorbed Layer ◽  
Production Performance ◽  
Darcy Flow ◽  
Pore Scale ◽  
Transition Flow ◽  
Gas Reservoirs ◽  
Flow Mechanisms

Abstract Many shale/tight gas reservoirs can have pore scale values in the range from one to hundreds of nanometer. And the flow in nano-scale deviate the Darcy's law. Knudsen diffusion and/or gas slippage effects usually have modeled to character the non-Darcy flow mechanisms by many authors. In this paper, we investigate the non-Darcy flow mechanisms in unconventional gas reservoirs, and classify these various mechanisms based on different pore scale and pressure. Then, based on the change of pore scale and pressure, the models of gas flow that consider the absorption, desorption, slip flow, transition flow, Knudsen diffusion and continuous flow in nano-pore have been proposed to evaluate the flow character. Then, the relationship between the absorbed layers and pressure or Langmuir coefficient has been built and the influences of absorption of gas molecule have been studied on the permeability change. Compared with experimental value, the model could agree with the experimental value very well. And, desorption of the absorbed layers make the pore diameter become larger. When the thickness of the absorbed layers and the pore diameter ratio is larger than 0.1, the effect of adsorbed layer becomes very significant. With this study, the change of permeability and the gas rate on entire long term production performance could be understood better and predicted, and it is very important for the optimization of production performance and adjustment.

scholarly journals An Experimental Study on Percolation Characteristics of a Single-Phase Gas in a Low-Permeability Volcanic Reservoir Under High Pressure

2015 ◽  
Vol 8 (1) ◽  
pp. 186-192
Author(s):  
Tang Xiaoyan
Keyword(s):  
High Pressure ◽  
Pore Pressure ◽  
Gas Flow ◽  
Single Phase ◽  
Stress Sensitivity ◽  
Gas Production ◽  
Low Permeability ◽  
Gas Reservoir ◽  
The Core ◽  
Slippage Effect

In this paper, we find that with the decrease in the average pore pressure in the process of gas production, both the slippage effect and the stress sensitivity effect will gradually increase; the increase in the slippage effect is significant, while the increase in the stress sensitivity effect is not. In this paper, the Kalamay volcanic gas reservoir of the Junggar Basin in China was selected as the object of our research. The gas reservoir has typical fractured volcanic reservoirs, and the long-term percolation feature remains unclear. To study the percolation characteristics of singlephase gas under high pressure, the experimental method was designed to simulate these characteristics in the process of gas production by measuring the gas flow in the core and the input and the output pressure at both ends. We carried out simulation experiments of single-phase gas flow percolation characteristics under high pressure using 11 pieces of volcanic rock samples in three wells of the study area. The results show that as the core pore pressure increased, the permeability of low-permeability cores of the volcanic rock decreased significantly at room temperature. However, this decrease became more gradual, which means that the higher the core pore pressure is, the smaller the permeability variation caused by gas slippage is; when the pore pressure is above 10 MPa, the permeability is nearly constant, slippage effect significantly reduces in the process of gas percolation, so it can be completely ignored under these formation conditions. As the pore pressure decreases, the slippage effect and stress sensitivity effect will gradually increase; when the pore pressure is less than 10 MPa, the permeability appears to increase significantly, and this is especially true for a pressure of 5 MPa. The main cause of this result is the slippage effect of gas seepage during the depletion of the gas reservoir, when the pore pressure is lower than a certain value. The valid stress changes of the core are not large, and the stress sensitivity is not strong, so the slippage effect plays a major role, which leads to an increase in the gas permeability during the late period of certain flow gas production.

Laminar Forced Convection in Annular Microchannels With Slip Flow Regime

2009 ◽  
Author(s):  
Arman Sadeghi ◽  
Abolhassan Asgarshamsi ◽  
Mohammad Hassan Saidi
Keyword(s):  
Nusselt Number ◽  
Fluid Flow ◽  
Aspect Ratio ◽  
Boundary Conditions ◽  
Knudsen Number ◽  
Gas Flow ◽  
Slip Flow ◽  
Outer Wall ◽  
Graphical Form ◽  
Uniform Temperature

Fluid flow and heat transfer at microscale have attracted an important research interest in recent years due to the rapid development of microelectromechanical systems (MEMS). Fluid flow in microdevices has some characteristics which one of them is rarefaction effect related with gas flow. In this research, hydrodynamically and thermally fully developed laminar rarefied gas flow in annular microducts is studied using slip flow boundary conditions. Two different cases of the thermal boundary conditions are considered, namely: uniform temperature at the outer wall and adiabatic inner wall (Case A) and uniform temperature at the inner wall and adiabatic outer wall (Case B). Using the previously obtained velocity distribution, energy conservation equation subjected to relevant boundary conditions is numerically solved using fourth order Runge-Kutta method. The Nusselt number values are presented in graphical form as well as tabular form. It is realized that for the case A increasing aspect ratio results in increasing the Nusselt number, while the opposite is true for the case B. The effect of aspect ratio on Nusselt number is more notable at smaller values of Knudsen number, while its effect becomes slighter at large Knudsen numbers. Also increasing Knudsen number leads to smaller values of Nusselt number for the both cases.

A permeability model for gas flow in coal considering the water content and slippage effect

2020 ◽  
Vol 3 (4) ◽  
pp. 305
Author(s):  
Jianhua Li ◽  
Bobo Li ◽  
Jiang Xu ◽  
Zhihe Wang ◽  
Zheng Gao ◽  
...  
Keyword(s):  
Water Content ◽  
Gas Flow ◽  
Permeability Model ◽  
Slippage Effect

Lattice Boltzmann Simulation of Rarefied Gas Flow Along Moving Rigid Objects in Micro-Cavities

2015 ◽  
Author(s):  
Weilin Yang ◽  
Hongxia Li ◽  
TieJun Zhang ◽  
Ibrahim M. Elfadel
Keyword(s):  
Free Path ◽  
Lattice Boltzmann ◽  
Path Length ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Free Path Length ◽  
Mean Free Path ◽  
Fluid Simulation ◽  
Transition Flow ◽  
Rarefied Gas Flow

Rarefied gas flow plays an important role in the design and performance analysis of micro-electro-mechanical systems (MEMS) under high-vacuum conditions. The rarefaction can be evaluated by the Knudsen number (Kn), which is the ratio of the molecular mean free path length and the characteristic length. In micro systems, the rarefied gas flow usually stays in the slip- and transition-flow regions (10−3 < Kn < 10), and may even go into the free molecular flow region (Kn > 10). As a result, conventional design tools based on continuum Navier-Stokes equation solvers are not applicable to analyzing rarefaction phenomena in MEMS under vacuum conditions. In this paper, we investigate the rarefied gas flow by using the lattice Boltzmann method (LBM), which is suitable for mesoscopic fluid simulation. The gas pressure determines the mean free path length and Kn, which further influences the relaxation time in the collision procedure of LBM. Here, we focus on the problem of squeezed film damping caused by an oscillating rigid object in a cavity. We propose an improved LBM with an immersed boundary approach, where an adjustable force term is used to quantify the interaction between the moving object and adjacent fluid, and further determines the slip velocity. With the proposed approach, the rarefied gas flow in MEMS with squeezed film damping is characterized. Different factors that affect the damping coefficient, such as pressure of gas and frequency of oscillation, are investigated in our simulation studies.

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