Investigation of Analysis Methods for Pulse Decay Tests Considering Gas Adsorption

Han, Guoqing; Chen, Yang; Liu, Xiao Li

doi:10.3390/en12132562

Cited by 6 publications

(8 citation statements)

References 31 publications

(60 reference statements)

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“…We examined closely the intact pressure curves throughout the experiment and found that gas flow in the preferential flow path occurs at the very beginning of the pulse-decay experiment, which finishes within one second based on our observation, and it is much faster than that in the secondary accessible flow path. Thus, the concepts of total and secondary accessible porosity, estimated from Equations (4) and (5), respectively, are proposed in this work to differentiate the two types of the flow path. Figure 4 shows two types of porosity calculated from the test at different pressures.…”

Section: Resultsmentioning

confidence: 99%

“…Gas and liquid permeability are different, partially due to the Klinkenberg (gas slippage) effect [1][2][3]. The transient pulse-decay experiments have been frequently applied to measure the permeability of tight porous media [4][5][6][7]. Table 1 chronologically lists representative work of exploring transient flow properties using the pulse-decay method since 1968.…”

Section: Introductionmentioning

confidence: 99%

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Impact of Heterogeneity on the Transient Gas Flow Process in Tight Rock

et al. 2019

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There exits a great challenge to evaluate the flow properties of tight porous media even at the core scale. A pulse-decay experiment is routinely used to measure the petrophysical properties of tight cores including permeability and porosity. In this study, 5 sets of pulse-decay experiments are performed on a tight heterogeneous core by flowing nitrogen in the forward and backward directions under different pressures under pore pressures approximately from 100 psi to 300 psi. Permeability values from history matching are from about 300 nD to 600 nD which shows a good linear relationship with the inverse of pore pressure. A preferential flow path is found even when the microcrack is absent. The preferential path causes different porosity values using differential initial upstream and downstream pressure. In addition, the porosity values calculated based on the forward and backward flow directions are also different, and the values are about 1.0% and 2.3%, respectively, which is the primary novelty of this study. The core heterogeneity effect significantly affects the very early stage of pressure responses in both the upstream and downstream but the permeability values are very close in the late-stage experiment. We proposed that that there are two reasons for the preferential flow path: the Joule–Thomson effect for non-ideal gas and the core heterogeneity effect. Based on the finding of this study, we suggest that very early pressure response in a pulse-decay experiment should be closely examined to identify the preferential flow path, and failure to identify the preferential flow path leads to significant porosity and permeability underestimation.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Impact of Heterogeneity on the Transient Gas Flow Process in Tight Rock

et al. 2019

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“…To study the performance of the pulse decay test in the presence of gas adsorption, the numerical simulation method of Han et al [23] was used in this study. Figure 13 shows the pressure equilibrium time considering the gas adsorption effect, where V L is the Langmuir volume [m 3 /kg] and P L is the pressure, respectively [Pa].…”

Section: Effect On the Pressure Equilibrium Timementioning

confidence: 99%

“…Cui et al [22] first considered the gas adsorption effect by modifying the porosity and extended the conventional analysis method to the case of gas adsorption. Han et al [23] considered the effect of the adsorbed phase volume based on Cui's method and proposed the pressure derivative method to analyze the pulse decay test of nonequilibrium adsorption situations.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Comparison of Test Performance of Different Pulse Decay Methods for Unconventional Cores

2020

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Various pulse decay methods are proposed to test tight cores. These methods can be divided into three types. This study compares the performance of these methods to test the permeability of unconventional cores in terms of homogeneous cores, dual-medium cores, and gas adsorption, including the pressure equilibrium time, possible errors caused by conventional analysis methods, and reflections on the characteristics of dual-media. Studies shows that the two test methods with an antisymmetric relationship in the boundary conditions have basically identical test performance. When testing homogeneous cores, regardless of whether the gas is adsorptive or not, the pressure equilibrium time of the first type of method is approximately half of that of the second type of method. The dual-medium parameters seriously affect the pressure equilibrium time of different methods, which may cause the difference of order of magnitude. For homogeneous cores, the permeability errors of the first and second types of methods caused by porosity errors are similar and larger than that of the third type of method. For dual media, the fracture permeability obtained by the third type of method using the conventional analysis method may differ from the actual value by tens of times. No method can significantly eliminate the sorption effect. When the core is a dual-medium, only the pressure curves of the upstream positive-pulse method, downstream negative-pulse method and one-chamber method can reflect the characteristics of dual media. The pressure derivative of the one-chamber method cannot reflect the characteristics of dual media at the early time. The pressure derivative of the second type and the upstream positive-pulse downstream negative-pulse method can reflect the complete characteristics of dual media, but their pressure derivative of the constant-slope segment is small, and the interporosity flow parameter may not be identified.

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“…Reservoir rocks in conventional versions are mainly characterized by absolute permeability above 0.01 mD, while unconventional-below 0.01 mD [1]. Computational fluid dynamic (CFD) gives the opportunity to assess the absolute permeability of the rock, supporting the standard procedure: laboratory measurements of absolute permeability, as gas permeameters [2]. However, it is still challenging to estimate the absolute permeability in tight rocks (unconventional) [3,4].…”

Section: Introductionmentioning

confidence: 99%

Research on Fluid Flow and Permeability in Low Porous Rock Sample Using Laboratory and Computational Techniques

Krakowska

Madejski

2019

Energies

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The paper presents results of fluid flow simulation in tight rock being potentially gas-bearing formation. Core samples are under careful investigation because of the high cost of production from the well. Numerical simulations allow determining absolute permeability based on computed X-ray tomography images of the rock sample. Computational fluid dynamics (CFD) give the opportunity to use the partial slip Maxwell model for permeability calculations. A detailed 3D geometrical model of the pore space was the input data. These 3D models of the pore space were extracted from the rock sample using highly specialized software poROSE (poROus materials examination SoftwarE, AGH University of Science and Technology, Kraków, Poland), which is the product of close cooperation of petroleum science and industry. The changes in mass flow depended on the pressure difference, and the tangential momentum accommodation coefficient was delivered and used in further quantitative analysis. The results of fluid flow simulations were combined with laboratory measurement results using a gas permeameter. It appeared that for the established parameters and proper fluid flow model (partial slip model, Tangential Momentum Accommodation Coefficient (TMAC), volumetric flow rate values), the obtained absolute permeability was similar to the permeability from the core test analysis.

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Investigation of Analysis Methods for Pulse Decay Tests Considering Gas Adsorption

Cited by 6 publications

References 31 publications

Impact of Heterogeneity on the Transient Gas Flow Process in Tight Rock

Impact of Heterogeneity on the Transient Gas Flow Process in Tight Rock

Theoretical Comparison of Test Performance of Different Pulse Decay Methods for Unconventional Cores

Research on Fluid Flow and Permeability in Low Porous Rock Sample Using Laboratory and Computational Techniques

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